lec 1 orthodontics اللهريخ دورو .د

Lec 1 Orthodontics خيرالله ورود. د

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What is orthodontics?

Orthodontics:

“Ortho” means correction of irregularity and “dontics” means teeth, so orthodontics

means correction the irregularities of teeth; but this is a narrow definition; so the

orthodontics can be defined as that branch of dentistry concerned with facial growth,

development of the dentition and occlusion, diagnosis, interception, and treatment of

occlusal anomalies.

According to American Board of Orthodontics “Orthodontics is that specific area

of dental practice that has; as its responsibility; the study and supervision of the

growth and the development of the dentition and its related anatomical structures from

birth to dental maturity, including all preventive and corrective procedures of dental

irregularities that requiring the repositioning of teeth by functional or mechanical

means to establish normal occlusion and pleasing facial contours”.

BRANCHES OF ORTHODONTICS

The art and science of orthodontics can be divided into three categories based on the

nature and time of intervention:

1) Preventive orthodontics

Preventive orthodontics is the action taken to prevent the development of

malocclusion such as the elimination of deleterious local habits (like thumb

sucking), the maintenance of tooth form by proper restoration of individual


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teeth; timely removal of retained deciduous teeth; use of space maintainers after

premature loss of deciduous teeth, if indicated,

2) Interceptive orthodontics

The procedures that are undertaken during the early development of

malocclusion to lessen the severity of malocclusion and sometimes the

elimination of the cause such as serial extraction, correction of developing

anterior crossbite and the removal of supernumerary teeth.

3) Corrective orthodontics.

The employing of certain technical procedures for an existed malocclusion to

reduce or eliminate the problem. The procedures employed in correction may be

Fixed or removable mechanotherapy, functional appliances or surgical

approach.

AIMS OF ORTHODONTIC TREATMENT

1. Psychosocial well being: The improvement of facial & dental esthetics which

lead to improvement the quality of life and Individual’s self –esteem( how

positively the person feels about himself), It reflects the patient’s desire to

improve their social acceptability and eliminate discrimination based on

appearance, which can affect their quality of life greatly.

2. Dental health:

a) Alignment of teeth in order to reduce the stagnation area, the presence of

stagnation areas makes the effective cleansing and brushing is difficult

which increase the risk for the development of dental caries.

b) Alignment of teeth in order to reduce periodontal diseases. The

malocclusion may force one or more teeth to be squeezed buccally or

lingually out of their investing bone reducing periodontal support and

traumatic occlusion may lead to increase the loss of periodontal support.

c) Alignment of anterior proclined teeth in order to reduce the possibility of

fracture or damage to the anterior teeth due to traumatic injury or

accident.

d) Impacted tooth may affect the position and health of adjacent teeth in

addition of loss of function of the impacted tooth itself.


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3. Functions:

a) Alignment of teeth in order to improve masticatory function. Patients

with open bites, markedly increased over jet (Class II) or reversed over

jet (Class III) often complain difficulties with eating particularly incising

food.

b) The elimination of premature contacts which give rise to mandibular

displacement and may cause later muscle or joint pain.

c) Orthodontic treatment of certain malocclusion which is related to speech

problems will result in speech improvement. (Not all cases of speech

problem are caused by malocclusion, sometimes there is a normal speech

associated with sever anatomic distortion).

d) The alignment of irregular teeth prior to bridge work, crown, partial

denture or dental implant.

OCCLUSION

Occlusion is the relationship in which the maxillary and mandibular teeth come

together when closing in centric relation. There are three types of occlusion:

Ideal occlusion: is a hypothetical concept of an ideal arrangement of teeth based on

the anatomy of teeth combined with an ideal inter-arch relationship which result in

optimal esthetic, function and stability of dentition and supporting structures. It is

rarely if ever found in nature. However, it provides a standard by which other

occlusion can be judged.

Normal occlusion: is an occlusion within the accepted deviation from ideal

occlusion. Minor variations in the alignment of the teeth which are not of esthetic or

functional importance may be considered as a normal occlusion.


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Malocclusion: is an irregularity in the occlusion beyond the accepted range of

normal.

Class I Class II Class III

The fact that an individual has a malocclusion is not itself a justification for treatment,

the orthodontic treatment should be considered only:

If the patient will benefit esthetically or functionally.

If the patient is suitable and willing to undergo the treatment.

The scope of orthodontic treatment:

i. Alteration in tooth position.

ii. Alteration in skeletal pattern.

iii. Alteration in soft tissue pattern.

Andrew's six keys of normal occlusion

In 1972, six significant occlusal characteristics identified & first reported by Lawrence

F. Andrews. These six keys are not method of classifying occlusion, but they serve as

a goal during orthodontic treatment.


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1) Molar relationship:

i. The mesiobuccal cusp of the maxillary first permanent molar should

occlude in the groove between the mesial and middle buccal cusp of the

mandibular first permanent molar.

ii. The distal surface of the distobuccal cusp of the maxillary first permanent

molar made contact and occluded with the mesial surface of the

mesiobuccal cusp of the mandibular second permanent molar.

iii. The canines and premolars enjoy a cusp-embrasure relationship.

2) Crown angulation (Mesio-distal tip):

The term angulation refers to angulation (or tip) of the long axis of the crown

not to the angulation of long axis of entire tooth. The gingival part of the facial

long axis of the crown must be distal to the incisal (occlusal) part of the axis, it

varied with each tooth type.

3) Crown inclination (Labio-lingual or Bucco-lingual inclination):

Crown inclination refers to the labiolingual inclination of the long axis of the

crown anterior teeth or buccolingual inclination of the long axis of the crown of


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posterior teeth. For each tooth there is a specific inclination, which may be

either labial or buccal (positive torque); or lingual (negative torque).

In upper incisors, the crown inclination is labially, the gingival portion of the

crown’s labial surface is palatal to the incisal portion (positive inclination or

torque)

In all other crowns, including lower incisors, the crown inclination is

lingually, the gingival portion of the labial or buccal surface is labial or buccal

to the incisal or occlusal portion (negative inclination or torque) with

progressively greater negative inclination exist in lower(canines, premolar and

molars) when compared with upper (canines, premolar and molars).

4) Rotations:

To achieve correct occlusion none of the teeth should be rotated. Rotated molar

and bicuspid occupy more space than normal while rotated incisors occupy less

space than normal.

5) Spaces:

There should be a tight contact points between teeth with no spacing.


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6) Occlusal plane: The plane of occlusion is measured from the most prominent

cusp of the lower second molar to the lower central incisor. The occlusal plane

varied from flat to a slight curve of Spee. The mandibular curve of spee should

not be deeper than 1.5mm.

Recently, the authors believe that the correct crown diameter (correct tooth size)

represents the 7th key to normal occlusion. This key had to be present in Andrew’s

non orthodontic study models.


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The disadvantages and potential risks of orthodontic treatment:

1) Root resorption: During the course of 2-year treatment with a fixed orthodontic

appliance, it's inevitable to find around 1 mm of root length resorption as a

consequence of tooth movement. However, the use of excessive orthodontic

force may lead to unaccepted amount of root resorption and devitalization may

occur for the affected tooth or teeth.

2) Loss of periodontal support: As a result of reduced teeth cleansing, an increase

in gingival inflammation is commonly seen following the placement of fixed

appliances. This normally reduces or resolves following removal of the

appliance.

3) Demineralisation may occur due to plaque accumulation in patient with poor

oral hygiene.

4) Soft tissue damage: Traumatic ulceration can occur during treatment with both

fixed and removable appliances.

5) Pulpal injury: excessive orthodontic force may lead to pulp injury and death

especially for teeth with history of trauma.


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Definitions of common orthodontic terms

Overjet: It is the horizontal distance between the lingual surface of maxillary

incisors and the labial surface of the mandibular incisors when the teeth occlude in

occlusion, measured at the tip of upper incisor.

There are 4 types of overjet on dependent upon the inclination of incisors and the

antero-posterior relationship of the dental arches:

1. Normal overjet: the overjet is between 2-4mm in which the upper incisors are

in front of the lower incisors in occlusion.

2. Excessive overjet: it is increased overjet more than 4 mm in cases of class II.

3. Edge-to-edge overjet: the overjet may be zero in case of edge to edge

relationship.

4. Reversed overjet: the overjet may be less than zero in cases of class III.

Excessive overjet Reverse overjet Edge to edge overjet

How to measure the overjet?

Ask the patient to close in centric occlusion. Put

the Vernier (Orthodontic Ruler) horizontally,

however the end of the vernier touch the labial

surface of lower incisor. The measurement in the

vernier caliper that reaches the incisal edge of

upper incisor represents the O.J.


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Overbite: is the vertical distance between the tips of the maxillary incisor margin

and the mandibular incisors margin when the teeth occlude in occlusion.

1. Normal overbite: the tip of lower incisors contacts the middle third of the

palatal surface of the upper incisors in occlusion (directly below the cingulum

plateau of upper incisors (2-4mm).

2. Anterior open bite: there may be no incisal contact and the lower incisor edge is

below the level of the upper incisal edge in occlusion (less than zero). It

subdivided into:

a) Dental open bite: a localized open bite that involves only few teeth due

to a digit sucking habit or other local factor

b) Skeletal open bite: caused by divergence of the skeletal mandibular

and/or maxillary planes leading to increase the facial height as in case of

posterior rotational growth of the mandible.

Normal overbite Dental open bite skeletal open bite

3. Deep overbite: excessive overbite more than 4 mm. It may be:

a) incomplete overbite (non-traumatic): when the lower incisal edge dose

not touch any opposing tooth or tissue

b) Complete overbite: when the lower incisal edge occludes with the

palatal soft tissue or the palatal aspects of the opposing upper incisors. It's

either:

i. Traumatic: when the upper incisors are proclined and the lower

incisors cause trauma to the palatal soft tissue.

ii. Bitraumatic: when the upper incisors are retroclined and the lower

incisors cause trauma to the palatal soft tissue and the upper

incisors cause trauma to the lower labial soft tissue.


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Incomplete overbite Deep overbite Open bite

Traumatic deep bite complete over bite Bitraumatic deep bite

How to measure the overbite?

Ask the patient to close in centric occlusion. Mark by pen, the amount of

overlap of upper incisor on the labial surface of lower incisor edge. Ask the patient to

open his mouth. Then measure by vernier caliper (Orthodontic Ruler) the vertical

distant between the incisor edge of the lower incisor and the marked point on the labial

surface of lower incisor. This measurement represents the overbite.

Cross bite:

It is an abnormal relationship of one or more teeth in one dental arch to one or more

teeth of opposing arch in buccolingual or labiolingual direction.

Classification of cross bite

1. According to the etiology:

a) Dental crossbite: when cross bite is confined to the dentition

b) Skeletal crossbite: generally, the greater the number of teeth in cross bite

the greater is the skeletal component of the etiology. A cross bite of

buccal segments may be due to mismatch in the relative width of the


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arches, or due to an antero-posterior discrepancy which results in a wider

part of one arch occlude with a narrower part of the opposing arch.

For this reason, buccal cross bite of an entire buccal segments are mostly

associated with class III malocclusion, and a lingual cross bites are

associated with class II malocclusion.

c) Functional crossbite: are usually occurring due to the presence of

occlusal interference. In this situation, the patient tends to habitually

move the mandible forward or laterally in order to achieve maximum

intercuspation. For example, anterior cross bite in pseudo class III

malocclusion which associated with anterior mandibular displacement;

and false unilateral posterior cross bite which is associated with lateral

mandibular displacement.

2. According to their location in the arch:

a) Anterior crossbite: if one or more of the lower incisors are in front of the

upper incisors, this condition is called reverse overjet.

b) Posterior crossbite: cross bite of the premolar and molar region involving

one or two teeth or entire buccal segment. This can be classified into:

i. Buccal posterior crossbite: the buccal cusps of the mandibular

posterior teeth occlude buccally to the buccal cusps of the

maxillary posterior teeth. This can be classified according to the

side into:

A. Unilateral crossbite: affect only one side of the dental arch.

It could be either:

i. True unilateral crossbite: occur due to unilateral

constriction of the upper arch and usually does not

associated with deviation of the mandible on closure

ii. False unilateral crossbite: caused by narrowing of

the maxilla or widening of the mandible leading to

cusp to cusp relation, this situation is uncomfortable to

the patient so the patient tries to get maximum

intercuspation by deviation of the mandible to one

side leading to the development of unilateral cross

bite.

B. Bilateral crossbite: affected both sides of dental arch and

caused by severe maxillary collapse and/or mandibular

widening, there is no mandibular deviation during closure.


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ii. Lingual crossbite (Scissor bite): the buccal cusps of the

mandibular posterior teeth occlude lingually to the palatal cusps of

the maxillary posterior teeth without contact of their occlusal

surfaces.

Anterior crossbite unilateral posterior crossbite bilateral posterior crossbite

False unilateral crossbite

Buccal posterior crossbite Lingual crossbite (Scissor bite)

Lec 2 Orthodontics ورود خيرالله . د

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Definitions of common orthodontic terms

Tooth size-arch length discrepancy (TSALD): it is the differences between the space

needed in the dental arch and the space available in that arch. It is manifested in the

form of crowding or spacing, and it's may be mild, moderate or severe. It may also be

localized to the anterior or posterior region or generalized.

Spacing: it is tooth size-arch length discrepancy where the tooth size is less than the

arch length and lead to spacing. A dental arch with spacing of more than accepted

range (2 mm or more), it is either:

a) Localized: Localized in one position like median Diasthema that caused by

abnormal frenal attachment.

b) Generalized: Affect the whole dental arch mostly caused by abnormal soft

tissue function like tongue thrust

Crowding: it is tooth size-arch length discrepancy where the tooth size is more than

the arch length, which can lead to lack of space in the dental arch and usually

associated with rotation and displacement of teeth. A dental arch with crowding of

more than accepted rang (2 mm or more); either caused by local factor like early

extraction of deciduous teeth or general factor like collapsed maxillary arch that lead

to crowding of the whole arch.


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Imbrication: The overlapping of incisors and canines in the same arch, usually due to

crowding.

Midline shift (deviation): it is a lack of coincidence between the upper and lower

dental midline. A midline shift of 0.5 mm may consider as normal. Maxillary and

mandibular dental midlines are assessed in relation to the facial midline and to the

each other. Deviation of midline can be due to:

a) Mandibular deviation during closure as in case of premature occlusal

contact.

b) Asymmetric dental crowding such as in unilateral buccally malposed canine.

c) Unilateral missing of the teeth.

It is very important to determine the position of midline shift if it in the upper or lower

arch or in both of them during diagnosis and treatment planning specially in order to

choose which tooth or teeth to be extracted, in addition to that it is important to

differentiate between midline shift of the dentition and the face because we may see

one of them or some time both of them. Midline shift of the face mostly caused by


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abnormal skeletal factor (like unilateral hyperplasia of the mandible) or deviation of

the nose.

Unilateral hyperplasia of the mandible

Abnormal inclination: this condition involves an abnormal tilting of the crown, with

the root being in it normal position. A tooth may be abnormally inclined in any of the

four directions labially, buccally, lingually, mesially or distally.


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Proclination: it is the term used to describe labial inclination (tilting) of anterior teeth

toward the lips.

Retroclination: it is the term used to describe lingual inclination (tilting) of anterior

teeth.

Impaction: it is the failure of a tooth to erupt. Occur when the eruption space is

completely blocked or occupied by other teeth due to crowding. It tend to affect the

last tooth erupt in each segment like the upper canines and the third molars.

Transposition: the switching in the position of two adjacent teeth usually the canine

and the neighboring incisor or premolar.


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Occlusal plane: the plane where the upper and lower dental arches comes in contact

with each other, which could be either flat or slightly curved.

Infraposition (Infraocclusion): A situation in which a tooth or group of teeth is

positioned below the occlusal plane; commonly due to a deleterious habit or to

ankylosis.

Over eruption (Supra eruption. Supraocclusion): The situation where a tooth or

group of teeth is positioned above the occlusal plane such as in case of extracted

opposing tooth or teeth.


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Rotation of teeth: this term refers to the movement (rotation) of a tooth around its

long axis. It most evident when viewing the tooth from an occlusal perspective;

mostly, caused by crowding and sub divided into:

1) Mild (less than 90°): Can be treated easily by removable orthodontic appliance

using couple force system.

2) Sever (more than 90°): Must be treated by Fixed orthodontic appliance only

Displacement of tooth:

It is means abnormal position of the tooth (crown and root) in the dental arch.

Overlapping of teeth: It is means abnormal position of the crown of the tooth in the

dental ach while there is normal position of root in the jaw.


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Malocclusion

Malocclusion is an irregularity in the occlusion beyond the accepted range of normal.

It could be considered in the following groups:

1) Teeth: Malpositioning of individual tooth or groups of teeth in normally related

dental arches and jaws.

2) Dental arches: Mal-relation of the dental arches to each other upon bony bases

which are themselves normally related. The ma-lrelation of the dental arches

can take place in all dimensions, antero-posteriorly, laterally and vertically.

3) Dental bases (skeletal bases): The shape and the relation of the mandible to the

maxilla are unfavorable to the production of a normal occlusion.

Note: Basal arches (skeletal bases) mean maxillary and mandibular bones, while

dental arches mean the teeth and their investing alveolar bone.

The malocclusion can be seen in form of:

Intra-arch problems: malpositions of individual tooth or group of teeth in the

same arch.

Inter-arch problems: malrelation between the upper & lower dental arches.


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Intra-arch problems

1) Labioversion (buccoversion): A tooth that has a position labial or buccal to the

normal position.

2) Lingoversion (palatoversion): A tooth that has a position lingual or palatal to the

normal position.

3) Mesioversion: A tooth that has a position mesial to the normal position.

4) Distoversion: A tooth that has assumed a position distal to the normal position.

5) Supraversion: Over-erupted above the level of occlusion.

6) Infraversion: Depressed below the level of occlusion.

7) Torsiversion: Turned or rotated tooth around its long axis.

8) Transposition

9) Impaction

10) Crowding

11) Spacing

12) Proclination

13) retroclination


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Inter-arch problems

1) Sagittal problems:

a) Class II malocclusion: the lower dental arch and/or skeletal base are in

distal relation to the upper dental arch and/or skeletal base. The mesio-

buccal cusp of the upper first permanent molar occludes anterior to the

buccal groove of the lower first permanent molar

b) Class III malocclusion: the lower dental arch and/or skeletal base are in

mesial relation to the upper dental arch and/or skeletal base. The mesio-

buccal cusp of the upper first permanent molar occludes posterior to the

buccal groove of the lower first

2) Vertical problems (open bite and deep bite)

3) Transverse problems (cross bite)

4) Midline shift

Class II Class III


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Classification of malocclusion

Angle classification( molar classification)

This classification of malocclusion was introduced by E. H. Angle, based on the

anteroposterior relationship of the maxillary and mandibular first permanent molars.

Angle’s classification divided the malocclusion into four groups:

Normal occlusion: normal anteroposterior relationship of the maxillary and

mandibular dental arches where the mesiobuccal cusp of the maxillary first

permanent molar occludes in the buccal groove between the mesial and middle

buccal cusp of the mandibular first permanent molar, and the teeth are on the

line of occlusion

Class I malocclusion (Neutrocclusion): the mesiobuccal cusp of the maxillary

first permanent molar occludes in the buccal groove between the mesial and

middle buccal cusp of the mandibular first permanent molar, but with

malocclusion like crowding, spacing, rotation of teeth, etc.

Class II malocclusion (Distocclusion)(Postnormal occlusion): The mesio-

buccal cusp of the maxillary first permanent molar occludes anterior to the

buccal groove of the mandibular first permanent molar. The severity of class II

malocclusion is determined by fraction of cusp or unit. For example class II

malocclusion half cusp or full cusp. Class II malocclusion can be divided into:

a) Class II malocclusion, Division 1: class II malocclusion with proclined

maxillary incisors resulting in an increased over jet with incomplete over

bite or mostly deep bite.

b) Class II malocclusion, Division 2: class II malocclusion typically with

the maxillary incisors tipped palatally, a short anterior lower face height,

deep bite and normal or decreasing over jet. Three types of Class II

Division 2 malocclusion can be distinguished based on differences in the

spatial conditions in the maxillary dental arch:

Type A: The four maxillary permanent incisors are tipped palatally,

without the occurrence of crowding.

Type B: The maxillary central incisors are tipped palatally and the

maxillary laterals are tipped labially.

Type C: The four maxillary permanent incisors are tipped palatally,

with the canines labially positioned.


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Type A Type B Type C

Class III malocclusion (Mesiocclusion)( Prenormal occlusion): The mesio-

buccal cusp of the maxillary first permanent molar occludes posterior to the

buccal groove of the mandibular first permanent molar. The severity of class III

malocclusion is determined by fraction of cusp or unit. For example class III

malocclusion half cusp or full cusp.

a) Pseudo class ІІІ (FALSE or postural): This is not a true class ІІІ

malocclusion but its presentation is similar. Here the mandible

displaced anteriorly during final stages of closure due to the

presence of premature contact of the incisors or the canines.

b) True class III: class III malocclusion which is not associated with

forward displacement of the mandible.

Molar classification

Class II division 1 Class II division 2


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Pseudo class III malocclusion True class III

Important notes:

Angle’s system of classification based on the permanent 1st molar. So, when

the permanent 1st molar is missing we should shift to another classification

which is canine classification and if there is impacted canine or missing we

shift to incisor classification.

Angle’s system of classification describes only the antero-posterior (sagittal)

relationship for permanent first molar and does not take in to account many

other important relationships in the anteroposterior (overjet, canine

relationship), in transverse relationship (crossbite) and vertical relationship

(open &deep bite).

Angle’s system of classification does not identify intra-arch problems such as

spacing, crowding, rotation, missing or impacted teeth.

Angle’s system of classification describes only the dental antero-posterior

(sagittal) relationship which is not necessarily the same as the underlying

sagittal skeletal relationship.

Sometimes, the Angle’s classification is not symmetrical on both sides for

example, we can find class II molar relationship on left side and class I molar

relationship on right side, this is called class II sub-division left; Condition in

which class III molar relationship is present only on the right side with class I

molar relationship on the other side, this is called class III sub-division right

Canine classification:

Class I canine relationship: It is a normal canine relation, when the tip of the

upper canines located in the embrasure area between lower canine and first

premolar (or the mesial slope of the upper canine coincide with the distal slop of

lower canine) in occlusion.

Class II canine relationship: Abnormal canine relation in which the lower

canine will be more backward from normal canine relation in occlusion.

Class III canine relationship: Abnormal canine relation, when the lower

canine will be more forward than from normal canine relation.


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Incisor classification

The incisor relationship does not always match the buccal segment (Angle

classification). Since much of the orthodontic treatment is focused on the correction of

incisor mal-relationship, it is helpful to have a classification of incisor relationship.

Class I. The lower incisor edges occlude with or lie immediately below the cingulum

plateau (middle part of the palatal surface) of the upper central incisors.

Class II. The lower incisor edges lie posterior to the cingulum plateau of the upper

incisors. There are two divisions to Class II malocclusion:

Division 1. The upper central incisors are proclined or of average inclination, with an

increased overjet.

Division 2. The upper central incisors are retroclined. The overjet is usually of an

average amount but mostly increased (deep bite).


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Class III. The lower incisor edges lie anterior to the cingulum plateau of the upper

incisors. The overjet may be either reduced or reversed.

Classification of dental base (skeletal bases) relations

The terms skeletal class I, II, III are commonly applied to describe dental base

relations in the antero-posterior direction when the jaws are closed and the teeth in full

occlusion.

1) Skeletal class I: The jaws are in their ideal antero-posterior relationship in

occlusion.

2) Skeletal class II: The lower jaw in occlusion is positioned further back in

relation to the upper jaw. This could be due to: a small mandible, a large

maxilla or a combination of both.

3) Skeletal class III: The lower jaw in occlusion is positioned further forward in

relation to the upper jaw. This could be due to: a large mandible, a small

maxilla or a combination of both.


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Classification of deciduous teeth:

Terminal plane denotes the anteroposterior relationship between the distal surfaces of

the upper and lower second primary molar, which can be classified into three types:

1) Flash terminal plane: The distal surfaces of the maxillary and mandibular

second deciduous molars are in the same vertical plane. This is the normal

relationship in the primary dentition because the mesiodistal width of the

mandibular molar is greater than the mesiodistal width of the maxillary molar

2) Mesial step: distal surface of the mandibular deciduous second molar is

positioned more mesial (anterior) than the distal surface of the maxillary

deciduous second molar

3) Distal step: distal surface of the mandibular deciduous second molar is

positioned more distal (posterior) than the distal surface of the maxillary

deciduous second molar that's mean the upper deciduous second molar occludes

with two opposing teeth.

Mesial step Flush terminal plane Distal step


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Growth and development

Introduction

What we mean by growth & development??

Growth can be defined as an increase in size or number (hypertrophy or hyperplasia)

while Development is the term refer to an increase in complexity (increase in

specialization). So we can say growth is largely an anatomic phenomenon, where as

development is physiologic phenomenon.

Why do dentist or orthodontist study growth & development??

We study growth and development to understand the following:

1. The knowledge about growth and development is necessary for every dentist in

order to distinguish normal developmental process from the pathological ones.

Knowledge of general and facial growth provides a background to the

understanding of the etiology and development of malocclusion. Such

understanding is an important part of the diagnosis and treatment planning

process.

2. The knowledge about growth and development is very important for

orthodontist since during this period any disturbances may give rise to certain

congenital malformation, facial deformities and malocclusion. As in case of

cleft lip &palate, the orthodontist plays a role in the management of this

condition at different ages from birth to maturity.

3. The dentist or orthodontist should be able to identify abnormal or unusual

pattern of skeletal growth at regular interval of the growing child in order to

undertake suitable interceptive treatment for example posterior rotational

growth of the mandible may lead to skeletal open bite.

4. The dentist should be able to identify abnormal occlusal development at an

early stage in order to undertake suitable interceptive orthodontic treatment.

Occlusal development is closely linked to facial growth and development

(premature contact may lead to skeletal class III) so the dentist or orthodontist

should be able to identify abnormal occlusal development that lead to skeletal

discrepancy.


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5. The knowledge about growth spurts (maximum growth period) and other trends

is very important in timing of certain orthodontic treatment as in myofunctional

appliance.

6. In certain treatment, for example when surgery is being considered, it important

to be able to identify when the majority of the facial growth has been

completed.

7. Growth has effect on the stability of the occlusion after orthodontic treatment in

growing patient, this need to be considered in planning retention phase. For

example, class III need long retention period because there is a continuous

mandibular growth till 20 years of age while maxillary growth usually stop

earlier.

The growth and development occur in two periods:

1) The prenatal or (neonatal) period

2) Postnatal period

The prenatal or (neonatal) period:

This category can be divided into three periods.

1. The period of ovum: (from the time of fertilization to the end of 7-8th day

I.U):

In this period, human development begins when a sperm fertilize the oocyte

resulting in formation of zygote. The zygote starts a rapid mitotic activity result

in rapid increase in cell number until it reach to 16 cells. The cells resulting

from this division are called blastomere, these cells adhere one to another and

form a ball which is called morula latter on the morula will form a cyst like

structure and became blastocyte. About six days after fertilization, the blastocyte

is composed of two distinct cell types:

The outer cell mass (trophoblast) which form a single layer of cells

covering the outside of blastocyte.

The inner cell mass (embryoblast) which is a cluster cells located inside

the trophoblast.

The inner cell mass (embryoblast) develops into embryo whereas the outer cell

mass (trophphoblast) forms the embryonic part of placenta and other peripheral

structures associated with the embryo.


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From day one of fertilization till the formation of blastocyst the ovum travel

from the fallopian tube to the uterus and at day 7-8 the blastocyst implant itself

in the wall of the uterus. The process of implantation end the ovum period and

starts the embryo period.

2. period of embryo: (8th day- 8th week I.U)

In this period, most organs and systems are formed, it is a period of differentiation

and most congenital malformation developed during this period. At the end of this

period most of the systems are established (C.N.S, G.I.T, Respiratory, and Genito-

Urinary … etc.) the developing individual has a recognizable human appearance.

One of the most important events in this period is the formation of the three germ

layers (ectoderm, mesoderm and endoderm).

All body organs are derived from these germs layers furthermore the ectoderm layer

will give rise to the neural crest cells which is responsible for the formation of

important organs.

The ectoderm will give rise to: Skin & its appendages, Oral mucous membrane, nails, hair, lens of eye, lining of the

internal and external ear, nose, sinuses, mouth, anus, tooth enamel, pituitary gland, and all

parts of the nervous system.

The mesoderm will give rise to: 1) Cardiovascular system (Heart & Blood vessels).

2) Bones & muscles.

3) Connective tissue (pulp, dentin, periodontal ligament & cementum).

4) Spleen, blood cells and lungs.


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The endoderm will give rise to.

1) Epithelial lining of alimentary canal between the pharynx & Anus.

2) Secretary cells of liver & pancreas.

3) Epithelial lining of respiratory system.

4) Tongue and tonsils.

Neural crest cell (N.C.C) contributes to form:

1) Parts of peripheral nervous system (automatic nervous system, Facial,

Glossopharyngeal, vagus & pare of trigeminal ganglia).

2) Cartilages of Branchial arches.

3) Osteoblasts that form intra membranous skull bones.

4) Facial processes.

5) Odontoblast (Precursor of dentin)

3. Period of fetus: (from the end of 8th week to the end of 40th week)

Most of the cranio –facial structures are formed in the first trimester of pregnancy. In

the last months of fetal life a rapid growth takes place i.e. the head is reduced from

about half of the entire body length at third month of intrauterine development to

about 1/3 at 5th

month and to about 1/4 at birth. Gender can be identify externally at

the 4th month. Ossification centers of most of the bones appear in this period.

Early Orofacial Development

In the Second week of embryonic life, the first sign of future position of the oral

development (endodermal thinking in the bilaminar germ disk) can be noticed. The

oropharangeal membrane will demarcate the shallow depression called stomodeum

(primitive oral cavity).

3rd week, in this week the head is composed mainly of fronto-nasal prominence which

overhangs the developing oral groove, this oral groove initially is covered by

oropharyngeal or buccopharyngeal membrane which consists of ectoderm and

endoderm, this membrane later on repture to establish oral opening.

This oral groove which is called stomodeum is surrounded by five facial prominences

cranially by fronto-nasal prominence, caudally by two fused mandibular

prominences and laterally by two maxillary prominences.


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4th week, in this week we can notice two ectodermal proliferations on either sides of

the frontal process, these later on will give rise to nasal placodes which develop to

nasal pit and olfactory epithelium.

At this time we can see the brachial or pharyngeal arches, the first pharyngeal arch is

called mandibular arch while the second arch is called hyoid arch, by the end of 4th

week four well defined pharyngeal arches can be distinguished while fifth & sixth

arches are too small and cannot be seen at the surface of embryo during this period.


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On the 5th week the nasal pits widen and the medial and lateral walls of nasal pit start

to proliferate and grows downward giving rise to the medial nasal and lateral nasal

processes. The maxillary processes on either side start to proliferate toward the medial

nasal processes, since they are proliferating faster than the lateral nasal process, the

union between the medial nasal and the maxillary processes gives rise to the maxilla,

palate, upper lip and the lower central part of the nose. The line of fusion of the two

medial nasal processes is represented by a depression on the upper lip called the

Philtrum. On either side, the maxillary prominences form the lateral part of upper lip,

the fusion between maxillary prominence and medial nasal prominence complete at 7th

week of the embryonic development, the failure of fusion between these two processes

result in a cleft lip which may be unilateral or bilateral it also can be a complete or an

incomplete one.

So the middle part upper lip (philtrum) is formed by the union of two medial

nasal processes, while the lateral parts of the upper lip are formed by the union

maxillary prominences.


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By the 8th -week, the facial structures are apparent. The nose is more prominent and

the nasal septum elongates and become more narrowed, the eyes migrate toward the

midline and the ears begin to develop, the nostrils are formed by an opening in the

nasal pit area which communicates with the upper part of the oral cavity.

The nasal septum is forming from the medial nasal process and the frontal

prominence; the demarcation between the lateral nasal process and the maxillary

process creates a furrow, which is converted into the nasal-lacrimal duct when it

closes over.

By the 12th -week the eyelids and nostrils have formed and subsequent intra-uterine

changes lead to a little further differentiation, these intrauterine changes involve

increases in size and changes in proportions.


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Development of palate

The palate begins to develop early in the 6th week, but the process is not completed

until 12th week. The most critical period during palatal development is the end of the

6th week to the beginning of 9th week.

The entire palate develops from:

1- The primary palate (premaxilla): is the triangular –shaped part of the palate

anterior to the incisive foramen. It's origin from the deep portion of the intermaxillary

segment which arises from the fusion of the two medial nasal prominences.

2- The secondary palate: which represent the part of hard palate posterior to incisive

foramen and the soft palate. By the sixth weeks of intra uterine life shelf like

projections are derived from the maxillary processes on both sides, these are called the

palatal shelves. The secondary palate arises from these paired lateral palatine shelves

of the maxillary prominences. At the eight-week, the palatal shelves will have

proceeded toward each other and united with each other and with the downward

proliferating nasal septum. These at the posterior region but anteriorly the lateral

shelves unite with the primary medial palatal triangle (medial nasal origin).


10 | P a g e

These shelves are oriented in a vertical plane with the tongue interposed, later they

become elongated and the tongue become smaller and moves inferiorly, this allow the

shelves to orient horizontally to approach one another and then to fuse in the midline.

This downward dropping of the tongue is attributed to two theories:

The growth of the mandible downward will pull the tongue with it (most

excepted).

The embryo will raise his head up leaving the tongue with the mandible in a

lower position.

The cleft palate results if the two palatine shelves of the maxillary prominences failed

to fuse with each other.

So the formation of the palate progresses through these distinct stages:

1. The development of the individual palatal components.

2. The lateral palatine shelves must assume a horizontal position above the dropping

tongue.

3. The palatal shelves must fuse with each other and with pre-maxillary region of

palate and the descending nasal septum.


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Cleft lip & palate

The etiology of cleft lip and palate is thought to be multifactorial:

1) Genetic is implicated in 20%-30% of the patients.

2) Environmental factors that have been shown in experimental animals to

result in clefting include nutritional deficiencies, radiation, several drugs,

hypoxia, viruses, and vitamin excesses or deficiencies.

Cleft lip: Is classified either unilateral or bilateral and it could be minor cleft of the

lip (small notch in the upper lip) or increase in the severity to complete cleft of the

upper lip, or continue to reach the nostril or to the angle of the eye, mostly unilateral,

some time cleft lip may include cleft of the alveolar ridge.

Cleft palate: The fusion of the palatal components that form the palate (two lateral

maxillary palatal shelves and the primary palate) usually start from the anterior aspect

and continue posteriorly so that cleft palate could happen at any site through this

process of fusion. The least severe form of cleft palate is the bifid uvula, of relatively

frequent occur, increasingly severe clefts always include posterior involvement, the

cleft advancing anteriorly in contra distinction to the direction of normal fusion.

Cleft palate can be classified according to its' severity as follows:

Class I: Cleft of soft palate (uvula)

Class II: Cleft of the secondary palate (median palatine

cleft)

Class III: Complete unilateral cleft palate

Class IV: Complete bilateral cleft palate


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Cleft lip and palate could happen separately or combined with each other. If the

cleft involves the alveolar arch, it usually passes between the lateral incisor and canine

teeth.

Classification

There is no entirely satisfactory system of classification and this reflects the wide variety of

presentation. For the individual patient it is probably most convenient just to describe the

defect however, for purposes of classification it is useful to divide clefts in three groups:

1. Clefts of the primary palate: may involve only the lip or the lip and alveolar process

as far as back as the incisive foramen.

2. Clefts of the secondary palate: may involve the soft palate only or the soft palate and

the hard palate as far as forwards as the incisive foramen.

3. Clefts involving both the primary and secondary palate.

Note: Cleft of the lip and primary palate may be unilateral (most commonly in the left side)

or bilateral.


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Effects of cleft lip and palate

Dental effects:

The presence of cleft which disturbs the dental lamina can lead to a variety of dental

presentations.

1) The lateral incisor may be absent, diminutive, and /or peg shaped with enamel

hypoplasia.

2) They may be a supernumerary or supplemental tooth located in either portion of the

alveolar bone adjacent to the cleft.

3) The tooth or teeth will often be displaced palatally and rotated.

4) If the central and lateral permanent incisors are displaced, the deciduous incisors may

retain.

5) There is also delay in dental development on the cleft side, leading to later eruption

times.

Occlusal effects:

1) A Class III incisor relationship is frequently found with a midline shift to the cleft

side.

2) Unilateral cases will frequently demonstrated a cross bite in the buccal segment,

especially in the cleft side.

3) There will usually be a gap in the dental arch in the line of cleft as the teeth can't

erupt or move into an area with limited bone.

Skeletal effects:

1) There is often a class III skeletal relationship.

2) There is also an increased anterior face height for both unilateral and bilateral clefts.

3) Lateral open bite may also be found on the cleft side due to a localized failure effect

the alveolar development.


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Treatment of cleft lip and palate:

Treatment of cleft lip and palate must be started as soon as possible after birth because

of:

1. Its physiological effect on the infant since it interferes with the natural feeding

process.

2. Its psychological trauma to the parents

The treatment of patients with cleft lip and \ or palate is along and involved process

needs many stages of intervention by many different specialists, forming a cleft lip

and palate team.

Orthodontist starts a few days after birth, with a construction of baby feeding

plate that assists the infant to suck and swallow the milk properly. It is a piece of

acrylic that disconnect between the oral and nasal cavities which are opened to each

other through the cleft palate. This plate has advantage to help the two pieces of the

palate to approximate toward each other (orthopedic movement).

Repair of the lip is performed within the first three months after birth, and the

palate is repaired within the first year. The scar tissue created from these and other

surgical procedures is considered responsible for some degree of maxillary growth

inhibition.

When the cleft involves the alveolar process, a bone graft may be necessary to

restore the alveolar anatomy and this is performed prior to the eruption of the

permanent maxillary canine on the side of the cleft include:

1. Phase I of orthodontic treatment may consist of expansion of the constricted

maxilla and correction of any cross bites as a preparation for the alveolar bone

graft. Following by alveolar bone grafting, and when the patient is in the

permanent dentition.

2. Phase II of orthodontic treatment is performed to idealize the occlusion, or if a

severe skeletal discrepancy is present, orthodontic treatment is performed to

prepare the arches for orthodontic surgery.


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Time of treatment for cleft lip and palate:

Age 0

M

3

M

6

M

9

M

1

Y

2

Y

3

Y

4

Y

5

Y

6

Y

7

Y

8

Y

9

Y

10

Y

11

Y

12

Y

13

Y

14

Y

15

Y

16

Y

17

Y

18

Y

Palatal obturator

Repair cleft lip

Repair soft palate

Repair hard palate

Tympanostomy tube

Speech

therapy/Pharyngeal

surgery

Bone grafting jaw

Orthodontics

Further cosmetic

corrections

http://en.wikipedia.org/wiki/Palatal_obturator

http://en.wikipedia.org/wiki/Soft_palate

http://en.wikipedia.org/wiki/Hard_palate

http://en.wikipedia.org/wiki/Tympanostomy_tube

http://en.wikipedia.org/wiki/Speech_therapy

http://en.wikipedia.org/wiki/Speech_therapy

http://en.wikipedia.org/wiki/Pharyngeal_flap_surgery

http://en.wikipedia.org/wiki/Pharyngeal_flap_surgery

http://en.wikipedia.org/wiki/Bone_grafting

http://en.wikipedia.org/wiki/Orthodontics


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Growth and development

Development of the tongue

The tongue develops from several different sources:

1. The body of the tongue or the anterior two thirds develops from the first

pharyngeal arch

2. The base of the tongue or the posterior one third develops mainly from the third

pharyngeal arch.

The tongue begins its development near the end of the 4th week as a midline

enlargement in the floor of the primitive pharynx, cranial to the foramen cecum; this

enlargement is called the tuberculum impar. Two lateral lingual swellings form

adjacent to the tuberculum impar, all these three structures (tuberculum impar & two

lateral lingual swellings) form as a result of proliferation of the first pharyngeal arch.

The lateral lingual swellings rapidly enlarge, fuse with one another and

overgrow the tuberculum impar, these three structures give rise to the body of the

tongue or anterior two third of the tongue.

The posterior one third or the base of tongue develops from the hypobrachial

eminence which is a midline swelling caudal to the foramen cecum; the hypobrachial

eminence is originated primarily from the 3rd pharyngeal arch.

There is a small swelling derived from the 2nd pharyngeal arch, this swelling

disappear without contribution in the formation of the tongue, the hypobrachial

eminence proliferate and fuse with the tuberculum impar and two lateral lingual

swellings. Thus the base or the posterior one third of the tongue is derived from 3rd

pharyngeal arch while the anterior two third or the body of tongue is derived from the

1st pharyngeal arch. The line of demarcation between the body and the base of tongue

is called terminal sulcus, and the foramen cecum is found in the midline of this

structure.


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Development of the mandible

In the mandibular brachial arch (first pharyngeal arch) there is a cartilage called

Meckel's cartilage, which is arise at 6th week of intra-uterine life serve as a precursor

of mandibular mesenchyme, which forms around it and is responsible for mandibular

growth activity. Bone begins to develop lateral to the Meckel's cartilage during the 7th

week and continues till the posterior aspect which is covered with bone.

During further development, Meckel’s cartilage retrogresses and disappears

except for two small portions at their dorsal end which persist and form the incus &

mallus.

The condylar cartilage develops initially as an independent secondary cartilage which

is separated by a considerable gap from the mandible, later on it fuse with developing

mandibular ramus.

The activity of the condylar cartilage does not appear until the 4th or 5th month of

postnatal life and continues until the age of 20 years so it has no role in prenatal life.


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The post-natal Growth Of the face & cranium

At birth, the skull is far from being merely a small version of the adult skull. There

are differences in shape, in the proportion of the face & the cranium, & in the degree

of development & fusion of the individual bones.

The individual bones of the skull & face are separated to many part e.g., sphenoid,

occipital, temporal & frontal bones. Some bones which appear as a single bone in

adult are still in separate constituent part at birth, other bones in the adult which are

closely jointed to their neighbors at sutures, at birth widely separated from

neighboring bones by a wide sutural areas which termed fontanelles, these are the

active bone formation areas.

Bones, which have developed from cartilage, mainly those at the base of the skull,

still have a cartilaginous element active growth. Bones; which have developed from

membrane (Intramembranous) by secretion of the bone directly within connective

tissue without any intermediate formation of cartilage; still have a wide membranous

area at their margins activity forming bone. This type of ossification occur in the

cranial vault (bones that cover the upper and outer surface of the brain) and in the both

jaws.

The Features of Skull at birth

The main features of skull at birth can be summarized as follows:

1. Bones in separate component parts.

2. Bones widely separated from neighboring bones.

3. Relative size of the face and the cranium.

1. The bones in separate component parts

a) At the base of the skull the sphenoid bone is in 3 parts, the central body with its

two lesser wings, and on each side the greater wing and its attached pterygoid

process.

b) The occipital bone is in two parts, the condylar part which carries the occipital

condyles and the squamous part which has developed from membrane and form

part of calvarium.

c) The temporal bone on each side is in two parts, the petro-mastoid component

which has developed from the cartilaginous neurocranium and the squamous

component which has developed from the membranous neurocranium.


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d) The frontal bone and the mandible, which will eventually become single

bones, are each in two parts at birth, the parts being separated in the mid-sagittal

plane.

2. Bones widely separated from neighboring bones

Sutures and fontanelles are present during fetal and early neonatal life. The

sutures are fibrous joints comprised of sheets of dense connective tissue that separate

the bones of the calvaria while fontanelles are regions of dense connective tissues

where the sutures come together, the sutures of the skull are wider at birth than in the

adult being areas of active bone formation.

Furthermore the presence of these wide sutures and fontanelles at birth help to

change the shape and size of skull to facilitate the passage of the baby through the

birth canal, sutures and fontanelles ossify at variable times after birth.

These separation (the fontanelles) are particularly noticeable at the four corners

of the parietal bone which are the anterior and posterior fontanelles in the mid sagittal

plane where the parietal bones meet the frontal bone anteriorly and the occipital bone

posteriorly, the antero-lateral and the postero-lateral fontanelles on each side at the

junction of the parietal, sphenoid and frontal bone anteriorly and parietal, temporal

and occipital bone posteriorly.


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At birth the sphenoid and occipital bones are still separated by a cartilaginous

area, the spheno-occipital synchondrosis, and eventually become fused at the base of

the skull.

3. The relative size of the face and the cranium

The relationship in size between the face and the cranium is noticeably different

at birth from that in the adult. The cranium has grown rapidly in the pre-natal period to

accommodate the rapidly developing brain. The face has developed less toward its

adult size than has the cranium with the result that at birth the face appears small in

vertical dimension in relation to the total size of the head when compared with

situation in the adult. The main reasons for this are:

1. The maxilla and the mandible, which form the main contribution to the vertical

dimension of the face, are relatively small at birth.

2. The maxillary antrum is little more than a flat space when compared with its

much greater vertical depth in the adult.

3. The mandible is relatively straight with a more obtuse angle than in the adult.

4. In the both bones there are no erupted teeth and consequently little vertical

development of alveolar bone.


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Rates of growth from the birth to the adult

At birth the head forms about 1/4 of the total height of the body while in the adult

the head forms about 1/8 of the total body height therefore, between birth and maturity

the body must grow faster than the head.

In infancy, growth proceeds at a relatively high rate, slowing progressively during

childhood to reach a minimum rate in the pre-pubertal period then there is an increase

in the growth rate in puberty and finally a marked slowing in growth rate to maturity;

while the total growth of the head from birth to maturity is proportionally less than that

of the rest of the body.

The two main components of the head are the cranium and the face, they are

differing in their relative proportion at birth and at maturity as we mention before, and

therefore they must grow at different rates.

Growth rate of the cranium

The cranium, which has grown rapidly before birth, continues to grow rapidly up to

about one year of the age accommodating the developing brain to provide an increase

in the physical and mental activity. Then the growth rate decreases and by about 7

years of age the cranium has reached 90% of its final volume, and there is a slow

increase in size to maturity. The growth rate of eyes and consequently of the eye

sockets follows a similar pattern. Thus the infant appears to have a small face with

large eyes, large cranium and retrusive nose if compare with adult.


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Growth rate of the face

The growth rate of the face, which is highest at birth, falls sharply to minimum

level in prepuberal period then it increases to a peak at puberty declining again until

growth stops in late teenage.

Facial growth is normally associated with the eruption of the primary dentition

between 1 and 3 years of age and of the permanent dentition between 6 and 14 years

of age, when the erupting teeth and the developing alveolar process add to the total

size of the jaws. Roughly the facial growth rates follow the same pattern as the rate of

the body growth.

Both maxilla and mandible show a forward and downward growth pattern. The

period of the maximum growth of the jaws is a few months later than that of body

height.

The mandibular growth continued for about 2 years longer than maxillary

growth and this difference in the growth between the two jaws may be important in

orthodontic treatment planning. The growth rate is earlier in females than in males.


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Mechanisms and areas of growth

Bones unlike most other tissues cannot grow simply by interstitial division of its living

cells. There are three main mechanisms of bone growth:

1. Cartilaginous Growth (Endochondral ossification):

Defined as the growth of the cartilage by cells division with progressive

conversion to bone by ossification, the area of its occurrence are mainly at the

base of the skull, in the area of the nasal septum and at the head of the

mandibular condyle.

At the base of the skull, Growth of cartilage at the spheno-occipital

synchondrosis would increase the antero-posterior dimension of the skull

base.

Growth of the nasal septum cartilage would bring the nose forward

The growth in the condylar cartilage would increase the height & width

of the mandible.

2. Sutural Growth (Intramembranous ossification)

The bone of the face and skull articulate together mostly at sutures; the sutural

growth occur by apposition of the bone in the areas of sutures between adjacent

bones.

The bony sutures of the head are such that sutural growth would be capable of

increasing the size of the head in all dimensions. The bony sutures which

separate the face from the cranium are aligned so that the growth in these


9 | P a g e

sutures will move the face forward and downward direction, similarly the

growth in the midline sutures would allow expansion of the maxilla.

3. Periosteal and Endosteal Growth (remodeling) Apposition & resorption occur

at many sites of the face and jaws allowing the enlargement of the head. The

apposition of the bone on the periosteal surfaces would obviously enlarge the

head in all dimensions, it would also cause the bone to be excessively thickened

and therefore concomitant resorption of the bone is necessary in order to obtain

the appropriate thickness and strength.

However, periosteal growth is not simply a matter of addition of bone to the

outer surface and resorption of bone from the inner surface. Endosteal

resorption and addition of the bone from and within the cancellous spaces is

also necessary to maintain the appropriate thickness of the cortical layer of

bone.

It is generally thought that this method of growth is the most active type of

growth in the skull and jaws after the first few years of life when cartilaginous

and sutural growth slows.


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Functional Matrix Growth (Moss theory)

This theory depends on the concept that each part of the skull will grow by the

stimulation of soft tissue matrix that mean the bones and cartilage will grow to

accommodate a growing vital organs.

The vault of the cranium will grow by the stimulation of growing brain to

accommodate its increase in size.

The orbital cavity will grow by the stimulation of growing eyeballs.

The growth of the maxilla is stimulated by the development of maxillary sinus

and nasal cavity.

The growth of the mandible can also be stimulated by the growth of tongue.

Alveolar bone growth can also be stimulated by development and eruption of

teeth.

This is the matter of controversy, the bones are growing by the stimulation of tissue

matrix growth or tissue matrix grows as a result of increase its bony compartment.

Sites of growth

The craniofacial complex divided into four areas that grow differently:

1) The cranial vault, the bones that cover the upper and outer surface of the brain

2) The cranial base, the bony floor under the brain, which also is the dividing line

between the cranium and the face.

3) The nasomaxillary complex, made up of the nose, maxilla, and associated small

bones.

4) Mandible.

1. Cranial vault (calvarium):

The calvarium is the part of the skull which develops from the membranous bones

surrounding the brain and therefore it follows the neural growth pattern. It comprises

the frontal bone, parietal bones, sequamous part of temporal bones and occipital bone.

These bones are formed directly by intermembranous bone formation without

cartilaginous precursors. The apposition of new bone at the cranial sutures and

periosteal activity (remodeling) due to the pressure from the growing brain play a role

in growth of cranial vault.


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Sutural growth occur primarily at the periosteum-line contact areas between adjacent

skull bones (sutures), but periosteal activity also changes both the inner and outer

surface of these bone plates (resorption occur from the inner surfaces & apposition

from the outer surface). Most of the growth of the cranial vault is completed by about

7 years of age.

2. Cranial base: In contrast to the cranial vault, the bones of the base of the skull (cranial base)

are formed initially in cartilaginous and will grow by endochondral ossification that

occurs at both margins of synchondrosis.

Growth occurs by:

1) Bone remodeling and sutural infilling usually occur as the brain enlarges.

2) The primary cartilaginous growth sites usually present in this region. One of

the important sites of these is spheno-occipital synchondrosis

Cartilaginous growth at the spheno-occipital synchondrosis can cause antero-

posterior expansion; this synchondrosis does not ossify until 12-16 years of the age

and therefore regarded as active growth center to the age of puberty.

Sutural growth at the suture bordering the sphenoid and occipital bones allows lateral

growth of the cranial base and it is probably active up to 6-7 years of age.


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The spheno-occipital synchondrosis is anterior to the temporomandibular joints but

posterior to the anterior cranial fossa and, therefore, its growth is significant clinically

as it influences the overall facial skeletal pattern.

The Growth at the spheno-occipital synchondrosis increases the length of the cranial

base, and since the maxillary complex lies beneath the anterior cranial fossa while the

mandible articulates with the skull at the temporomandibular joints which lay beneath

the middle cranial fossa the cranial base, it plays an important part in determining how

the mandible and maxilla relate to each other.

Anterior cranial fossa


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Sites of growth

3. Naso-Maxillary region (Maxilla)

The maxilla develops entirely by intramembranous ossification. Since there is no

cartilage replacement, growth occurs in two ways:

(1) By apposition of bone at the sutures that connect the maxilla to the cranium

and cranial base and

(2) By surface remodeling.

Maxillary region

I - Sutural growth:

Transversal Growth:

Occur due to the action of saggital suture such as inter nasal suture, inter maxillary

suture, inter palatine suture. Their activity decrease at the end of the 1st year but they

continue forming osteal tissue for a long period.


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Vertical & Antero -posterior Growth:

This type of growth depends on growth of tempro-zygomatic suture, maxillo-

zygomatic suture, maxillo-palatine suture (pterygo-palatine or peterio-maxillary

suture) and fronto-maxillary suture. These sutures are parallel to each other and orient

the direction of the facial growth downward forward.

Tempro-zygomatic suture is the last facial suture, which remains active

maxillo-palatine suture is active up to 5-6 years

maxillo-frontal and fronto-zygomatic suture play an important role in the

vertical development of the orbital cavities before the 7th

years of life.

Note. Bone apposition occurs on both sides of a suture, so the bone to which the

maxilla is attached also becomes large. Part of the posterior border of the maxilla is a

free surface in the tuberosity region; bone is added at this surface creating additional

space into which the primary and then the permanent molar teeth successively erupt


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II. Remodeling (apposition and resorption):

As the maxilla grow downward and forward, its front surface is remodeled and the

bone is removed from the anterior surface of the maxilla. It might seem logical that if

the anterior surface of the bone is moving downward and forward, this should be an

area to which the bone is added not one from which the bone is removed. The correct

concept is that the bone is removed from the anterior surface although the anterior

surface is growing forward.

a- vertical growth

1- Alveolar process: the formation of alveolar process start about the 4th

month of

I.U.L their growth is by apposition of bone on 3 aspects (inferior, internal, external).

In posterior region on 2 aspect (internal, and inferior), in the anterior region on the

palatal and inferior aspect.

2- Palate: There will be resorption on the superior aspect (nasal) and apposition on the

inferior aspect (oral); this would bring the palate down ward.

Alveolar process palate


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b- Transversal growth

An important osteal growth (apposition) occurs on the external aspect of maxilla, but

only in the posterior part of the premolar.

c- Anterior- posterior and sagittal growth

Growth occurs by:

1. By anterior alveolar growth, resorption in the vestibular part and apposition on

the inferior and palatal part.

2. By an apposition on the posterior aspect of the horizontal part of the palate.

3. By important development of the tuberosity.

The hard palate

Postnatally the growth occurs in:

Length: the maxillary tuberosity grows backward to accommodate the extra teeth, also

sutural apposition at the transverse palatine suture increasing the length.


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Width: Increase in width occurs due to the bony apposition in the mid palatine suture.

The bone apposition will be ceased at 1-2 years but still there is potential growths that

can allow future orthodontic expansion (Rapid palatal expansion screw ; Hyrax

appliance), also the increase in width take place due to the bonny apposition occur at

the alveolar processes.

The lateral appositional growth occur in palate up to 7 years, at that age it reaches in

maximum at the outer region it continue in posterior direction after lateral apposition

is ceased, thus increasing the length of the palate.

Horizontal growth

Vertical: during infancy &childhood bone apposition occur at the inferior surface of

the palate (oral surface) accompanied by bone resorption at the superior surface (nasal

surface), thus flattening the palate & increase the nasal cavity to ensure the respiratory

requirement; that why we see a V shaped palate (deep palate) in mouth breathing

patient or in associated with other abnormal behavior (like in thumb sucking).

Vertical growth


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Nasal region

Nasal part become progressively prominent, nasal cavity develops particularly

on their inferior part from the 10 years of age, and the superior part wedged between

the orbits no more growth while the inferior part continue to develop in vertical &

transversal direction which is in relation with the descending palate.

Maxillary sinus As the sinus has a volume of small peas, the eruption of the deciduous teeth will

modify its volume and it increase in size with the eruption of the 1st molar about 8

years it has a pyramidal form that will lengthen after the eruption of the canine and the

last molar.

4. Mandible

In contrast to the maxilla, both endochondral (cartilaginous) and periosteal

activity are important in growth of mandible. The secondary cartilage appears as

dissociation from the primary cartilage or from chondrocranium. This secondary

cartilage appears at the condyle, coronoid and mental protuberance areas (symphesal

suture).

The coronoid secondary cartilage ossifies and mingled with the mandible and

disappears before birth and plays no role in the mandibular growth.

The mental region, ossification began before birth and continues after birth up to the

1st year.


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The condylar secondary cartilage which is the primordial of the future condyle, a cone

shaped cartilage is regarded as the center of growth for the ramus and the body of

mandible. The increase in size is due to apposition and resorption phenomena.

It is growth began prenatally and continue postnatally at different rate reaching it is

maximum in puberty, the center of this cone shaped is converted into a bonny

structure, but the upper & outer part persist as an articulating surface and provide a

potential growth

At birth the mandible consist of two hemi-mandible separated by sympheseal suture.

The sympheseal suture will disappear at 2 years of age.

Antero-posterior Growth:

Periosteal & endosteal growth is important here.

1. Ramus of the mandible: It result in important apposition on the posterior border

and resorption on the anterior border but less rapid than the apposition in a way

that the ramus will move backward and become more thick.

2. Body of the mandible: The resorption of the anterior border of the ramus will

increase the antero-posterior dimension of the body of the mandible, so the

inferior part of the ramus is incorporated progressively in the body. An osteal

apposition occurs during the first year of the life at the mental symphesis.


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Vertical Growth:

1. Ramus of the mandible: At birth the ramus is very short, the activity of the

condylar cartilage lead to bonny laid down at the condylar cartilage in upward

and backward level lead to direct the body and ramus in downward and forward

direction.

2. Body of the mandible: The vertical growth of the ramus will move away the

body of the mandible from the maxilla in the space that is liberated there

through the development of the alveolar process by an osteal apposition with the

phenomena of teeth eruption. Little apposition occurs during the first year at the

inferior border of the body of the mandible.

Transversal Growth:

After the first year, the sympheseal cartilage does not play any more roles in the

growth only the apposition and resorption phenomena continue to manifest but they

stop early, the alveolar borders show thickening which accommodates the roots of the

permanent teeth.

In fact the increase in the transverse dimension of the mandible result from its vertical

growth because of its divergence toward the posterior, the transversal growth is

therefore sensitive in the posterior part particularly at the condyles which are more

away from each other following the transversal growth of the cranial base.

The expansion of mandible in a horizontal direction occurs as a result of the function

of the tongue, perioral muscle, and the expansion of the oral and pharyngeal cavity

(functional matrix theory). The shape of this horizontal expansion occurs in a V

shaped pattern due to early calcification of mental region.


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Features of growth &development

Pattern

Variability

Timing

Pattern

Pattern reflects proportionality; usually refer to a complex set of proportions rather

than a single proportional relationship. It describes change in these proportional

relationships over time.

A. Cephalocaudal gradiant of growth means that there is an axis of increased

growth extending from the head toward the feet. In fetal life, at about the third

month of intrauterine development, the head takes up almost 50% of the total

body length. At this stage, the cranium is large relative to the face and

represents more than half the total head. In contrast, the limbs are still

rudimentary and trunk is underdeveloped.

By the time of birth, the trunk and limbs have grown faster than the head and

face, so that the proportion of the entire body devoted to the head has decreased

to about 25%. The overall pattern of growth thereafter follows this course, with

a progressive reduction of the relative size of the head to about 12% in the adult

with more growth of the lower limbs than the upper limbs.


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Within the head region, cephalocaudal gradiant strongly affect the proportion of

growth of cranium and face with time. The skull of newborn infant has a much

larger cranium and a much smaller face, with an emphasis on growth of face

relative to cranium resulting in much more growth of facial than cranial

structures postnatally.

Within facial region, the facial growth pattern is viewed against the perspective

of cephalocaudal gradiant; the mandible being farther away from the brain tends

to grow more and later than the maxilla which is closer.


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Another aspect of normal growth pattern is:

B. Differential growth which means not all tissue systems of the body grow at the

same rate. Different tissues and in term different organs grow at different rates

and time for example: Muscular & skeletal tissue grow faster than brain and

CNS as reflected in the relative decrease of head size.

The body tissues can be broadly classified as (Lymphoid, Neural, General

(somatic) and Genital). Each of these tissues grows at different times & rates.

Scammon’s growth curve (Differential growth)

Scammon’s Curve refers to the growth of four major tissues of body. As the graph

indicates:

1) Growth of the neural tissues is rapid in early years of life and later on slow until

about 7or 8 years of age which is almost complete.

2) General body tissue, including muscle, bone and viscera, show S-shaped curve,

with a rapid growth in early years of life then followed by a definite slowing during

childhood and an acceleration at puberty (11-13 years in girls, 13-15 years in boys)

which is followed by further slower growth.

3) Lymphoid tissues proliferate far beyond the adult amount in late childhood, and

then undergo involution at the same time that growth of the genital tissues

accelerates rapidly.

4) The growth of facial skeleton follows the somatic growth pattern while the growth

of cranium follows the neural growth pattern.


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Variability

No two individuals with the exception of siamese twins are like in their growth

pattern. Hence it is important to think in terms of deviation from usual pattern and to

express variability before categorizing people as normal or abnormal.

It is important to determine whether an individual’s growth within the range of normal

variation or falls outsides the normal range, this can be achieved by using standard

growth chart in two ways:

1. The location of an individual relative to the group

2. Growth chart can be used to follow a child over time to evaluate whether there

is an unexpected change in growth pattern.

Timing

The same kind of growth and development happens for different individuals at

different times because biologic clock of individuals is different. Such as pubertal

growth spurt, occurs at different ages in different adolescents.

The adolescent growth spurt occur on the average nearly 2 years earlier in girls than in

boys, this variation in timing has an important impact on the timing of orthodontic

treatment, which must be done earlier in girls than in boys to take advantage of the

adolescent growth spurt.

This variation in timing of adolescent growth spurt between male and female is

responsible for much of the difference in adult size between men and women. Girls

mature earlier on the average, and finish their growth much sooner; boys are not

bigger than girls until they grow for a longer time at adolescence. The difference arises

because there is slow but steady growth before the growth spurt, and so when the

growth spurt occurs, for those who mature late, it takes off from a higher plateau.


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Because of variability and timing, all individual at a given chronological age are

neither of the same size or same stage of maturation. So it is better to compare

biologic development. Developmental ages including skeletal age and dental age are

used in evaluation of child’s growth status.


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Development of Occlusion

Types of Occlusion

Ideal occlusion

Normal occlusion

Malocclusion

Ideal occlusion: is a hypothetical concept of an ideal arrangement of teeth based on

the anatomy of teeth combined with an ideal inter-arch relationship which result in

optimal esthetic, function and stability of dentition and supporting structures. It is

rarely if ever found in nature. However, it provides a standard by which other

occlusion can be judged.

Normal occlusion: is an occlusion within the accepted deviation from ideal occlusion.

Minor variations in the alignment of the teeth which are not of esthetic or functional

importance may be considered as a normal occlusion.

Malocclusion: is an irregularity in the occlusion beyond the accepted range of normal,

malocclusion can occur as a result of genetically determined factors or environmental


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factors, or more commonly a combination of both. Studies from twins indicate that

skeletal pattern and tooth size and number are largely genetically determined.

Etiology of malocclusion

The etiology of a malocclusion is the study of its cause or causes. Malocclusion is said

to result due to the following factors occurring alone or in combination:

1. Hereditary (Genetic) influences

2. Environmental influence

The following components of dentofacial component are genetically determined

1) Tooth: size, shape & number.

2) Skeletal pattern: relation of maxilla to mandibular basal bones.

3) Soft tissue (muscles) especially their initial behavior pattern.

1. Heretidary influence

It includes the malocclusions transmitted by genes. Genes are responsible for

number of human traits where the dentofacial anomalies may or may not be in

evidence at birth. Knowledge of hereditary factors helps a clinician plan and executes

treatment that effectively addresses genetic causes, besides it helps greatly with both

the type and timing of orthodontic and surgical treatment.

A strong influence of heredity on facial features is usually obvious. It is easy to

recognize familial tendencies in the tilt of the nose, the shape of the jaw and the look

of the smile.

Certain types of malocclusion run in families (i.e. similar malocclusions in

parents and their offspring's) like cleft lip and palate, the Class III skeletal pattern due

to prognathic mandible is most commonly associated with familial tendencies, and the

long face pattern of facial deformity is the second most likely type of deformity that

run in families. Also, inherited disproportion between the size of the teeth and the size

of the jaws, which would produce crowding or spacing.


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Also, an inherited disproportion between the size or the shape of the upper and lower

jaws, which would cause improper occlusal relationships.

2. Environmental influences (external factors)

Environmental influences during the growth and development of the face, jaws,

and teeth consist largely of pressures and forces related to abnormal physiologic

activity.

The knowledge of environmental factors directs treatment decisions and involves

strategies to prevent the continued influence of environmental factors on the occlusion

of the teeth. For example, malocclusions resulting from an environmental factor such

as thumb sucking can be prevented if the habit is stopped before the age of 5 or 6

years in a child who is experiencing normal craniofacial and occlusal development. On

the other hand, when thumb sucking occurs in a child who has a developing Class II

Division I malocclusion, the habit is one etiologic factor superimposed on perhaps

several other factors including heredity.

Disturbances in embryologic development

Defect in embryologic development are either of genetic origin or environmental

origin, any agent that can disturb the development of embryo or fetus and cause birth

defect are called teratogens. The classes of teratogen include radiation, maternal

infection, chemicals and drugs.


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Treachers- Collins syndrome

It is characterized by generalized lack of mesenchymal tissue, Malar hypoplasia due to

underdevelopment of the zygomatic bone, Mandibular hypoplasia, Down-slanting

palpebral fissures, and lower eyelid colobomas

Hemifacial microsomia

Characterized by a lack of development in lateral facial areas. Typically there is

deformation of external ear and ramus of the mandible along with associated soft

tissues.


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Cruzon’s syndrome

This syndrome Occurs during the final stage of facial development due to prenatal

fusion of the superior and posterior sutures of maxilla along the wall of the orbit. It is

characterized by severe underdevelopment of mid-face; eyes seem to bulge from their

sockets.

Cleft lip & palate

Most common congenital defect involving the face and jaws, exactly where these

clefts appear is determined by the locations at which fusion of various facial

prominences fail to occur.

Cleidocranial dysostosis

It is characterized by abnormalities of clavicles, skull, jaws, maxillary retrusion &

possible Mandibular protrusion, retained primary teeth, delay or failure of eruption of

secondary dentition with multiple un erupted supernumerary teeth.


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Disturbances in fetal and prenatal period

Intra uterine molding: Any pressure against the developing face lead to

distortion of rapidly growing areas such as maxillary deficiency due to arm

pressure or flexing of head against chest leading to abnormal mandibular

growth (Pierre Robin Syndrome) accompanied with cleft palate.

Birth Injures:

Use of forceps to assist in delivery might damage one or both of

temporomandibular joints. Heavy pressure in the area of TMJ can cause internal

hemorrhage, loss of tissue, ankylosis and a subsequent underdevelopment of the

mandible. At one time, the underdevelopment of mandible is thought to be

caused by the use of forceps during difficult births, but in the light of the

contemporary understanding, children with deformities involving the mandible

are much more likely to have a congenital syndrome.


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Disturbances in childhood period

Childhood fractures of the jaws: Problem arises when the more severely

affected side lags behind in growth or scarring around tempromandibularjoint

restricts translation of condyle at the affected side resulting in facial asymmetry.

Muscle dysfunction:

a. Excessive muscle contraction can restrict growth like scaring after injury.


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b. Muscular dystrophy, cerebral palsy, muscle weakness syndromes lead to increased

anterior facial height, excessive eruption of the posterior teeth, narrowing of the

maxillary arch, anterior open bite.

c. Loss of part of musculature lead to facial asymmetry on the affected side since

musculature is an important part of the total soft tissue matrix whose growth normally

carries the jaw downward and forward.

Disturbances in adolescence period

Hemi-mandibular Hypertrophy: unilateral excessive growth of the mandible

occurs in metabolically normal individuals most commonly in females.


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Acromegally: Release of excessive amounts of growth hormone from an

anterior pituitary gland tumor resulting in excessive growth of mandible, Lips

thick, tongue enlarged, Teeth tipped buccally due to large tongue. In the

cephalometric radiograph we can see the enlargement of sella turcica and loss of

definition of its bony outline, reflecting the secretory tumor in that location.

Adenotonsillar hypertrophy, mouth breather: A backward rotation of maxilla

&mandible relative to cranial bases will lead to increase the mandibular plane

angle, excessive eruption of posterior teeth, long face and anterior open bite.


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Factors Affecting the Occlusal Development

1. General Factors.

2. Local Factors.

1. General factors: They affect all or greater part of the occlusion, they include:

Skeletal factors: the size, shape and relative positions of the upper and lower

jaws.

Muscle factors: the form and function of the muscles which surround the teeth.

Dental factors: the size of the dentition in relation to the size of the jaws.

Skeletal factors affecting occlusal development

The teeth are supported by the alveolar bone, which in turn based on the basal bone of

the jaws; as the teeth are set in the jaws, the relationship of the jaws to each other will

have a large influence on the relationship of the dental arches.

Any pathological condition affecting growth of the jaws is likely to have a marked

effect on the occlusion of the teeth. Inherited and acquired congenital malformation,

trauma or infection during the growing years can all affect jaw growth. The variation

in the skeletal relationship can be brought about:

1. Variation in the size of the jaws.

2. Variation in the position of the jaws.


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1- Variation in the size of the jaws

Maxillary excess/ deficiency

Mandibular excess/deficiency

Combination of both

2- Variation in the position of the jaws

Jaw in relation to the cranial base

Jaws in relation to each other

Alveolar bone in relation to basal bone

The variation in the position of the jaws can be studied in three planes:

Antero-posterior (sagittal)

Vertical

Horizontal

Jaw in relation to the cranial base The jaws are part of the total structure of the head. Each jaw may vary in its positional

relationship to other structures of the head. Such variation can exist greatly in sagittal

and vertical planes and with less extent in the lateral plane. It is usual in orthodontic

diagnosis to relate the jaws positions to the anterior cranial base and each jaw can vary

independently in its relationship to the cranial base.


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Jaws in relation to each other

Skeletal class I: The jaws are in their ideal antero-posterior relationship in

occlusion.

Skeletal class II: The lower jaw in occlusion is positioned further back in

relation to the upper jaw.

Skeletal class III: The lower jaw in occlusion is positioned further forward in

relation to the upper jaw.

The antero-posterior (sagittal) relationship of the upper and lower jaws affects

the occlusion

1. If one jaw is excessively small or large in relation to the other in sagittal

relationship the development of skeletal class II or class III relationship may

result.

2. If one jaw is set further back or further forward than the other in relation to the

cranial base the development of skeletal class II or class III relationship may

result.


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The horizontal relationship of the upper and lower jaws affects the occlusion

1-If the upper jaw is smaller than the lower jaw or the lower jaw is larger than the

upper jaw a buccal cross bite may result.

Buccal cross bite: the buccal cusps of the lower teeth occlude buccally to the buccal

cusps of the upper teeth.

2- If the upper jaw is larger than the lower jaw or the lower jaw is smaller than the

upper jaw a lingual cross bite may result.

Lingual cross bite: the buccal cusps of the lower teeth occlude lingually to the palatal

cusps of the upper teeth.

The vertical relationship of the upper and lower jaws affect the occlusion

The effect of the variation in the vertical relationship can be expressed in the shape of

the lower jaw at the Gonial angle:

1. High gonial angle tend to produce a long face, in severe cases open bite may

result.

2. Low gonial angle tend to produce a short face, in severe cases deep bite may

result.


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Alveolar bone in relation to the basal bone

1. The term skeletal relationship refers to the basal bone, the alveolar bone is

supported by the basal bone

2. The relationship between the upper and lower alveolar bone is not necessarily

the same as that between the upper and lower basal bones

3. The alveolar bone supports the teeth; therefore it will match tooth position

rather than basal bone position.

4. The alveolar bone relationships can only differ from basal bone relationship

within a limited range.

5. The alveolar bone grows to support the tilted teeth; they may be slightly

different in position from the basal bone. However the teeth cannot be moved

completely away from the basal bone. Therefore the basal bone relationship is

the most important in occlusal development.


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Methods of assessment of skeletal relationship

A. Clinical

1. Visual: skeletal relationship can be gained simply by observation of the subject

in profile, in this method the skeletal relationship may be masked by tooth

position or by lip thickness and posture.

2. Palpation method: palpation of the anterior surfaces of the basal parts of the

jaws with the teeth in occlusion, ideally the maxillary skeletal base is a 2-3 mm

a head of the mandibular skeletal base when the teeth are in occlusion.

Estimation is done by placement of index and middle finger at the soft tissue

point A & point B respectively.

B. Radiological: by using standardized lateral skull radiograph (cephalometric

radiograph).


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Skeletal Relationship in Orthodontic Treatment

The orthodontic treatment which is confined to tooth movement has little effect

on the size, shape or relative positions of the basal parts of the jaws while it has

a direct effect on tooth position and alveolar bone position.

The skeletal relationship limits the amount of orthodontic tooth movement in all

3 planes of space. It may not be possible to correct CLII or CL III incisor

relationships if they are based on severe skeletal II or skeletal III bases.

Severe Skeletal discrepancy remains a limiting factor to orthodontic treatment.

For example it would be difficult to reduce an overjet of 8mm where the teeth

are in the correct inclination. The etiology of the overjet is the severity of

skeletal CL II relationship.

D.U.C Faculty of Dentistry Orthodontic Dr. Ghufran Dhari 4th Grade Lec.9

Development of Dentition

1. Neo-natal period.

2. Deciduous dentition stage.

3. Mixed-dentition stage.

4. Permanent dentition stage.

Neo-natal period (Gum pad stage).

This period extend from birth up to the eruption of the first primary tooth, usually the lower

central incisors at around 6 months (0 – 6 months).

The alveolar arches of an infant at the time of birth are called gum pads. The mucous

membrane of gum pads of both maxilla and mandible are greatly thickened, pink in color and

firm in consistency.

These gum pads are segmented by transverse grooves in to ten segments and each segment is

a developing tooth site, the newly born child’s mouth usually contains 20 elevations

(segments) which are corresponding to the future 20 deciduous teeth (10 of them in the upper

jaw and 10 of them in the lower jaw).

The transverse groove between the canine and the 1st molar region is called the lateral sulcus

which expresses the distal margin of deciduous canines.

The gum pads get divided into ‘labio-buccal’ & ‘lingual portion’, by a dental groove.

The gum pads are separated from the palate or floor of mouth by a long and continuous

groove called gingival groove.

Maxillary gum pad


An anterior open bite (infantile) is seen during this stage in which the anterior region of the

upper and lower gum pads do not approximate each other (averted) with space created

between them while the upper & lower gum pads occlude with each other at molar region.

The infantile open bite is transient and self-corrected with eruption of primary teeth. The

anterior opening of the mouth will facilitate the feeding process (suckling) without

discomfort to the mother.

The upper jaw overlaps the lower jaw in antero-posterior and transverse direction, in other

words, the upper jaw is wider than the lower jaw and at the same time the lower jaw is in

retrognathic position in relation to upper jaw.

The labial frenum is usually attached to incisive papillary region and after the eruption of

deciduous teeth it will migrate in upward direction and gives the incisive papillary attachment

this is due to alveolar bone formation in association with the development of deciduous teeth.

Mandibular gum pad

Relation between upper and lower gum pads at birth


The upper lip at this stage is usually short, the anterior oral seal of the mouth occurs due to

the contact between the lower lip and the tongue.

The newly born child’s mouth is usually without teeth except, sometime, a natal or the

neonatal teeth. Natal teeth: teeth that are present at the time of birth while neonatal teeth:

teeth that are erupt at early age (within 30 days of life).

These teeth look like the deciduous teeth which are contained; enamel, dentine and pulpal

tissue, usually without root or there is a root with them, however it is very short. The other

types of these teeth consist of keratinized tissue only.

These teeth most commonly arise anteriorly in the mandible. These teeth could be typically a

lower primary incisor which has erupted prematurely or a supernumerary tooth.

There are familial tendencies for such teeth. They should not be removed unless they are

supernumerary, mobile or cause trauma to the mother during breast feeding.

Deciduous dentition period (From around the 6 month to 6 years)

The deciduous dentition stage starts with eruption of the first deciduous tooth, usually the

deciduous mandibular central incisor and ends with eruption of the first permanent molar.

The deciduous dentition begins to erupt at the sixth month of age until 2.5-3 year of age. (all

deciduous teeth will be erupted, completely, at the age of 3 years).


Eruption sequence of deciduous teeth :

o A, B, D, C, E

Chronology of Primary Dentition


Features of Primary Dentition

Physiological, developmental Spacing

Generalized spacing: spaces which are present among the primary dentition, more

prominent in the anterior region to accommodate the larger permanent teeth in the

jaws.

The absence of developmental spaces in the primary dentition is an indication that

crowding of teeth may occur when the larger permanent teeth erupt.

Primate/anthropoid/Simian spaces: these spaces usually present at the mesial

aspect of upper canines and distal aspect of the lower canines, (these spaces present

between B&C for upper arch and between C& D for lower arch) which is used for

proper interdigitation of opposing deciduous canines in to cl I canine relationship.

These spaces are termed as anthropoid spaces since it looks like the spaces that are

present between the teeth of higher apes. The primate spaces are used for early mesial

shift.

Primate spaces


Deep bite

The deep bite may occur in the initial stage of development due to the fact that the

deciduous incisors are more upright than their successors. The lower incisal edges often

contact the cingulum area of the maxillary incisors.

This deep bite is later reduced by:

Eruption of deciduous molars.

Attrition of incisors.

Forward movement of the mandible due to growth.

Over jet

The deciduous dentition shows increased over jet in the initial stage of development which is

usually get corrected later by forward growth of mandible.

Flush (straight) terminal plane

The mesio – distal relationship between the DISTAL SURFACE of the lower & upper

deciduous second molars is called the terminal plane.

The molar relationship in the primary dentition can be classified into 3 types:


Flush Terminal Plane: If the distal surface of maxillary and mandibular deciduous

second molars are in the same vertical plane.

Mesial Step: Distal surface of mandibular deciduous second molar is mesial to the

distal surface of maxillary deciduous second molar.

Distal Step: Distal surface of mandibular second deciduous molar is more distal to

the distal surface of the maxillary second deciduous molar.

A normal feature of deciduous dentition is a Flush(straight) Terminal Plane where

the distal surfaces of the upper & lower second deciduous molars are in the same

vertical plane

Determining the terminal plane relationship in the primary dentition is of great

importance because it determines the molar relationship (Angle classification) in the

permanent dentition as the erupting 1st permanent molars are guided by the distal

surfaces of the 2nd primary molars.


Changes that are happened in deciduous dentition period

Changes in spaces:

The spaces present between deciduous incisors tend to increase with age due to

The growth of the jaws in: antero-posterior, transverse and vertical direction.

The attrition occurs at the incisal edge and proximal surfaces of the deciduous dentition

due to increased masticatory forces.

Change in Incisor relationship

Overbite &overjet decrease

Mixed dentition period (Around 6 years- 12 years)

The mixed dentition period (stage) begins at approximately 6 years of age with the eruption

of the first permanent tooth, usually the lower first permanent molars and ends with

shedding of the last primary tooth at around 12 years of age.

During the mixed dentition period, the deciduous teeth along with some permanent teeth are

present in the oral cavity.


The permanent teeth replace the deciduous teeth (A,B,C,D and E) by (1,2,3,4 and 5) while

the molars (6,7 and 8) are developed in a separate entity.

The mixed dentition period is characterized by significant changes in dentition. So, most

malocclusions make their appearance during this stage.

Chronology of Permanent Dentition

Permanent teeth

Deciduous teeth


The mixed dentition period can be divided into three phases:

First transitional period.

Inter-transitional period.

Second transitional period.

First transitional period (6 years- 8 years).

The first transitional period is characterized by:

(1) The emergence of the first permanent molars.

(2) The exchange of the deciduous incisors with the permanent incisors.

The mandibular first molar is the first permanent tooth to erupt at around 6 years of age.


The exchange of incisors

The permanent central incisors will replace the deciduous central incisors and the permanent

lateral incisors will replace the deciduous lateral incisors .The collective mesiodistal width of

permanent incisors crowns are considerably larger than the deciduous teeth they replace by

7.6 mm in maxilla and 6 mm in mandible

This difference between the amount of space needed for the accommodation of the permanent

incisors (The collective mesiodistal width of permanent incisors crowns) & amount of space

available for this (The collective mesiodistal width of primary incisors crowns) is called

“INCISAL LIABILITY” which is about 7.6 mm in the maxillary arch & 6 mm in the

mandibular arch.

The incisal liability is overcome & the increased space requirement for the permanent

incisors to align them properly is gained from the following factors:

1. Utilization of spaces which are present between the deciduous teeth. (The physiologic or

the developmental spaces that exists in the primary dentition).

2. Proclination of the permanent incisors during eruption: the permanent incisors erupt into

a more labial position than their deciduous predecessor ( in a proclined situation) and

this will increase the available arch length present for the permanent incisors, this

proclination is mainly due to increased activity of tongue at this period due to increased

amount of growth stimulation hormones.


3. Transverse increase in inter – canine arch width is observed in both maxillary and

mandibular arches during the eruption of the permanent incisors.

4. During the eruption of lower permanent incisors, the lower deciduous canines will be

pushed in a distal and buccal direction in to the primate spaces due to the fact that the

collective mesiodistal width of permanent incisors is more than the collective

mesiodistal width of the deciduous incisors and since there is a contact between the

lower deciduous canines and the upper deciduous canines during lateral extrusion and

protrusion, so the upper deciduous canines will be pushed in a lateral and distal direction

and this will produce an additional spaces named as secondary spaces which will be

utilized by the permanent incisors.

Secondary spaces


The eruption of permanent first molars

The eruption of the permanent 1st molars is guided into the dental arch by distal surface of

the deciduous second molars.

Inter-transitional period (8.5- 10 years)

There is a silent period extends from 8.5 years of age to the 10 years of age this period is

called (Lull period). In the Lull period, there is no teeth emergence or exfoliation but there is

a little change in the occlusion including antero-posterior and vertical dimension.

In this period, the teeth present are the permanent incisors and first molar along with the

deciduous canines and molars

D.U. C Faculty of Dentistry Orthodontic Dr. Ghufran Dhari 4th Grade Lec.10

Second Transitional Period(10-12 years)

The Second Transitional Period is characterized by replacement of the(C, D & E) by (3,4 &

5) respectively and the emergence of the permanent 2nd molars.

Exfoliation of the mandibular primary canines at around 10 years of age usually makes the

beginning of this period. The (C, D & E) combined mesiodistal width is larger than the

combined mesiodistal width of the (3,4 &5) this difference in width will provide an excess

space for the permanent canines and premolars, this excess space named as “Leeway space”.

This space is very important for the development of normal occlusion.

The amount of leeway space is greater in the mandibular arch which is 3.4 mm in the lower

arch (1.7 mm per quadrant) and 1.8 mm in the upper arch (0.9 mm per quadrant).

The eruption of the permanent 2nd molars usually occurs at around 12 years of age. The upper

2nd molar developed below the maxillary antrum and situated in a high level in the maxillary

tuberosity and it take a long path of eruption but it is less than that of canine. In comparison

with canine’s path of eruption is twice as long as the second’s molar path of eruption.

Therefore, the upper 2nd molar is subjected to a less amount of malocclusion in comparison

with canine. Usually the upper 2nd molar when erupt, they directed distally, occlusally and

buccally.

For the lower 2nd molar, they have a short path of eruption in comparison with that of the

upper 2nd molar so the lower 2nd molars subjected to a less amount of malocclusion. The


lower 2nd molars developed at the anterior border of the ramus and when these teeth erupted,

they directed mesially and occlusally.

The Permanent Dentition period(12 years and beyond)

At approximately 13 years of age, all the permanent teeth except the third molar are fully

erupted.

The eruption of the third molars is the final stage in establishing the permanent dentition

which is usually erupted between 17 and 21 years of age, but this is characteristically variable

and in many cases they either remain un-erupted or fail to develop completely.

The sequence of permanent teeth eruption

The eruption sequences in the maxilla are:

(6124537)

The eruption sequences in the mandible are:

(6123457) or (6124357)


There is a difference in the erupting time of the canines in both arches. In the upper arch, the

canines generally erupt after the premolars while in the lower arch the canines erupt before

the premolars.

When the permanent second molars erupt before the premolars or canines are fully erupted,

significant shortening of the arch length occurs due to the mesial migration of the permanent

molars increasing the likelihood of malocclusion.

The eruption of permanent first molars

The first permanent molars erupt at 6 years of age. They play an important role in the

establishing and in the functioning of occlusion.

The antero-posterior positioning of the permanent 1st molars (Angle classification) is

influenced by:

Terminal plane relationship of the deciduous 2nd molars.

Shift of the teeth.

Differential forward growth of mandible.

The permanent 1st molars are guided into the dental arch by distal surface of the deciduous

second molars. The mesio – distal relationship between the distal surfaces of the lower &

upper deciduous second molars is called the terminal plane which could be (flush terminal

plane, mesial step &distal step).


The shift of teeth can occur in two ways:

The early mesial shift

The late mesial shift

The Early Mesial Shift: In a spaced arch, eruptive force of the permanent 1st molars causes

closing of any spaces present between the primary molars and the primate spaces, thus

allowing the molars to shift mesially. The early mesial shift occurs during the early mixed

dentition period utilizing the primate space.

The Late Mesial Shift: it is the mesial movement of the permanent 1st molar after exfoliation

of the primary molars & canine since the collected mesiodistal width of the C,D&E is more

than the collected mesiodistal width of the 3,4&5. And after the exfoliation of C,D&E , the

permanent first molars tries to move in a mesial direction utilizing this extra space (leeway

space) which is 3.4 mm in the lower arch and 1.8 mm in the upper arch.

The late mesial shift occurs during the late mixed dentition period utilizing the Leeway

space

Late shift by utilization of the

Leeway space

Early shift of the erupting first permanent

molars utilizing the primate spaces


The mesial shift of the teeth occurs in both maxillary and mandibular arch. However, the

mesial shift of the mandibular permanent molars is greater than mesial shift of the maxillary

permanent molars.

When the deciduous second molars are in a flush terminal plane, the permanent first

molar erupts initially into a cusp-to-cusp relationship or transform in to cl I molar

relationship which can be achieved by shift of the teeth (greater mesial movement

of the mandibular molars) &differential forward growth of mandible.

The erupting permanent first molars may be cusp-to-cusp relationship or cl I molar

relationship.

When the deciduous second molars are in a mesial step, the permanent first molar

will erupt initially into a Class I molar relationship or transform in to cl III molar

relationship by shift of the teeth and differential forward growth of mandible

The erupting permanent first molars may be in class I or class III molar relationship.

When the deciduous second molars are in a distal step, the permanent first molar will

erupt initially into a Class II molar relationship or transform in to cusp-to-cusp

relationship by shift of the teeth and differential forward growth of mandible

The erupting permanent first molars may be in class II molar relationship or cusp to -

cusp relationship.


Variations occur during the development of dentition

The permanent incisors during their eruption should be guided into a downward and forward

direction (for upper) and into upward &forward (for lower) to contact the roots of the

deciduous incisors causing their resorption.

Sometimes, the permanent incisors may be deflected from their normal path of eruption, so

the permanent incisors will erupt palatally or lingually to the deciduous teeth, this will lead to

the development of anterior cross bite.


Another normal variation is the ugly-duckling stage (Broadbent phenomenon 1945)

(physiological median diastema), Sometimes a transient or self-correcting malocclusion is

seen in the maxillary incisors region between 8 – 12 years of age, this phenomenon occurs

due to the pressure applied by the erupting canine on the roots of the lateral incisors, thus

driving the roots of the lateral incisors medially and the crowns flared laterally. This pressure

is transmitted to the central incisors also which will result in medial movement of the roots

and distal tipping of their crowns, producing a diastema (midline spacing) and flaring of

incisors. This condition usually corrects by itself when the canines erupt & the pressure is

transferred from the roots to the coronal area of the incisors.

Ugly duckling stage


The reduction in the arch length (loss of space) occurs as a result of premature exfoliation of

primary molars, interproximal caries, improper filling or ectopic eruption of permanent

maxillary first molar.

For the lower arch, the lack of space will influence the 2nd premolar eruption since it is last

tooth that erupt prior to the lower 2nd molar (except 3rd molar). The 2nd premolar may be

erupted in a lingual direction or it may be impacted under the first permanent molar.

premature exfoliation of primary molars

interproximal caries

Ectopic eruption of permanent maxillary 1st molar


For the upper arch, the lack of space will influence the canine eruption since it is the last

tooth that erupts prior to the eruption of upper 2nd molar. It could be erupted in to a buccal

direction, but if it is directed palatally, it will be mostly impacted because the masticatory

mucosa cannot be pierced by the canine due to the presence of high amount of collagen

fibers.

The upper canine is influenced by the problem of malocclusion in a great amount in

comparision to other teeth due to:

Its long and tortuous path of eruption (development) since its early development occur

under the orbit.

Its dependence on the presence or absence of the permanent lateral incisor. for the

canine to developed normally, it should firstly directed mesially until it touch the

apical part of the root of lateral incisor then it directed in to a downward and lateral

direction till reach the occlusal level.

If the root of the lateral incisor is abnormal or the lateral incisor is missed, then the

canine will lose its guidance plane of eruption and it will be erupted in any direction or

in any situation.

Lack of space available for the eruption of permanent canine causing either impaction

or displacement of canines.

Trauma


Variation in the occlusion could be seen after the eruption of 3rd

molar

The development of crowding at the anterior teeth especially at the lower incisor region can

be noticed after the age of 17 years old. This crowding could be occur due to the pressure

exerted from the eruption of third molar and this pressure will be applied on the buccal

segment teeth and these teeth will transmit the forces to the incisors. But the eruption of 3rd

molar cannot be considered to be the etiological factor which is responsible for this crowding

because the lower incisor crowding could be seen even when the third molar is congenitally

absent. So, the extraction of the 3rd molar may be or may be not eliminate the crowding at

lower anterior region.

The crowding of the lower incisor region may be related to the uprightening of the incisors at

this age, late forward growth of mandible, soft tissue maturation, reduction in the inter-canine

width, erupting lower 3rd molar, physiological mesial drift, anterior component of force of

occlusion.

lec 1 orthodontics اللهريخ دورو .د

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