Development of OcclusionDevelopment of Occlusion

Stage1. Deciduous teeth.Stage1. Deciduous teeth.Development of teethDevelopment of teeth• Mandibular central

incisors:– 8-th month

• Primary first molar– 16-th month– FIRST OCCLUSAL FIRST OCCLUSAL

VERTICAL VERTICAL DIMENSION AND DIMENSION AND ICPICP

• Primary second molars– 30-th month

Dental archDental arch

• More rounded than in permanent dentition

• Overbite: 3 mm

• Overjet: 2.5 mm

Anteroposterior intermaxillary Anteroposterior intermaxillary relation of the primary posterior teethrelation of the primary posterior teeth

• Mesial step betwwen the distal surfaces of the second molars– Mandibular teeth are situated more

anteriorly than the maxillary teeth

• Flush terminal plane– Distal surfaces of the deciduous

molars are in the same frontal plane

• Distal step

Primate spacePrimate space

• Largest space in the

primary dentition

– Mesially from the

maxillary primary

canine

– Distally from the

mandibular canines

Stage 2. Mixed dentition (6Stage 2. Mixed dentition (6thth to 12 to 12thth years)years)

• First permanent molar and exfoliation of the first central mandibular incisors– 6-th year

• Canines– 10-th year

• Permanent second molar– 12-th year

Development of intermaxillary Development of intermaxillary relationsrelations

• Mesial step:– Permanent first molars erupt in a neutral intermaxillary

relation• Mandibular is one cusp mesially than the maxillary

• Flush terminal plane:– Permanent molars erupt into cusp to cusp position

• 75% grows spontaneously into neutral position

• Distal step:– Postnormal occlusion (distal occlusion or Class II

occlusion) • Indicates that the mandibular arch is posterior to the maxillary arch

Leeway spaceLeeway space

Development mechanisms of Development mechanisms of the intermaxillary relationsthe intermaxillary relations

• Closure of the mandibular primate space– Pressure of the first permanent molars mesialize the

primary molars

• Utilization of the ”leeway” space upon exfoliation of the primary molars– Upon exfoliation of the primary molars the first

mandibular permanent molar can migrate more mesially than the maxillary

• Relatively more growth of the mandible than that of the maxilla– The greater mandibular groth will carry mandibular

teeth more anteriorly than the maxillary teeth.

Permanent dentitionPermanent dentition

• The dentition of most individuals differs in one or more respects from the theoretically ideal occlusion

Deviation from the ideal occlusionDeviation from the ideal occlusion-malocclusion (marked deviation)-malocclusion (marked deviation)

• 1. Dentitional– Form or eruption alignment of the teeth

• 2. Occlusal– Sagittal, vertical, transverse, intermaxillary

relation

• 3. Space anomalies– Spacing or crowding

75% of the population has at least one anomaly

Occlusal anomaliesOcclusal anomalies

• Extreme maxillary overjet (> 6mm)

• Mandibular overjet (< 0mm)

• Distal or mesial molar occlusion (1/2 cusp with or more)

• Anterior deep bite (5mm or more)

Occlusal anomaliesOcclusal anomalies

• Posterior open bite

• Anterior open bite (overbite ≤ 0 mm)

• Transverse: (buccal cusp of the maxillary posterior tooth occludes lingually to the buccal cusp of the opposing mandibular teeth– B, lingual crossbite

– C, buccal crossbite

Growth of the jawsGrowth of the jaws

• Maxilla– Apposition of the bone exclusively to the

tuberosity – Midpalatal suture area

• Mandible– Condyle (very important)

• Superior and anterior development deep bite• Posterior development anterior open bite

• Surface– Apposition at the posterior part of the ramus– Alveolar process

Factors influencing the facial Factors influencing the facial growth and biting formgrowth and biting form

• 1. Hereditary factors

• 2. Functional factors– Rectangular type

• Deep bite

• High muscular activity

• Steep articular eminence

– Triangular type• Open bite

• Lower muscular activity

• Shallow articular eminence

Parafunctions of the childhoodParafunctions of the childhood

• 1. Finger- or dummy (pacifier) sucking– Increased overjet

– Anterior open bite

– Crossbite

– Distal occlusion

• 2. Mouth breathing (due to obstructed airway)– Posterior crossbite

– Less labial inclination

Occlusal parafunctionOcclusal parafunction

• Parafunction in contrast to normal

functional behaviors such as mastication,

deglution, or speaking these behaviors

appear to have no functional purpose

– 1. Bruxism

• Teeth grinding or clenching

– 2. Lipbiting

– 3. Thumb sucking

– 4. Abnormal posturing of the jaw

Parafunctional behavior can result in several Parafunctional behavior can result in several serious problems for the patient and serious problems for the patient and

considerable frustration to the dentistconsiderable frustration to the dentist

Effects of bruxismEffects of bruxism

• Muscular pain on the working side

• Tooth wear

• Damage in the opposite TMJ, because there is no support on the non-working side

AdaptationAdaptation

• Canine wear progresses until non-working

side contacts develop and provide support

for the mandible during bruxism

• In long history of bruxism the muscles are

relatively strong and can withstand

clenching without pain and fatigue

Nocturnal bruxismNocturnal bruxism

• Signs in 80-90% of the population

• All stages of the sleep– Rythmic grinding patterns

– Periods of sustained forceful clenching• Lasts for 5min.

Ethiology of nocturnal bruxism Ethiology of nocturnal bruxism Theories!!!Theories!!!

• Occlusal (seems unlikely)

• Psychological– Stress

• Systemic– Drogs (amphetamine, L-DOPA, fenfluramine)

– Tardive dyskinesia- neuroleptic drugs

– Alcohol

– Genetic predisposition

Diagnosis of nocturnal bruxismDiagnosis of nocturnal bruxism

• 5% of the child, 10% of the adult population is aware of bruxism

• Further 40-60% can be identified by examination of occlusal wear patterns– Flattening of the maxillary canines

– Smooth shiny wear facets

– Tooth mobility, fractured restorations

– Muscle or joint pain upon waking up

– Anterior temporalis headache

– Muscle hypertrophy

– Sensitive teeth

Provocation testProvocation test

• With the wear facets matched the patient is asked to clench or grind maximally until symptoms are noted

• 0.5mg Benzodiazepine at bed time for one week temporarily reduces bruxism and symptoms of the patients

• Portable EMG biofeedback device may alarm during bruxism activity

Diagnosis of nocturnal bruxismDiagnosis of nocturnal bruxism

Diurnal parafunctionDiurnal parafunction

• Grinding and clenching• Thumb or finger sucking• Lip or cheek biting• Nail biting• Postural habits

– Drivers– Violinists

• Unilateral chewing• Musicians’ special movements• Loose complete dentures

Diurnal parafunctionDiurnal parafunction

• Symptoms are commonly exacerbated by chewing, biting, yawning and speaking

• Joint damage (excessive loading of the TMJ)

• Clicking sounds:– Muscle incoordination

– Muscular hyperactivity

– Internal derangement

Evaluation of diurnal parafunctionEvaluation of diurnal parafunction

• Questionnaire– Daily painchart: Oral habits may become

evident

• Diurnal EMG-alarm device

Occlusal trauma: responses in the Occlusal trauma: responses in the periodontium to occlusal forcesperiodontium to occlusal forces

• Primary– Abnormal forces acting onto the healthy

periodontium

• Secondary– Effect of occlusal forces that may or may

not be excessive in relation to the normal periodontium on an already reduced or weakened periodontium

• Microscopic and macroscopic changes in the periodontium

– Periodontal ligament: slight derangement to necrosis

– Alveolar bone: resorption and apposition

• Normal periodontium appears to be capable of adapting occlusal forces

• Periodontal pocket formation is not initiated by occlusal forces!!!

Occlusal trauma: responses in the Occlusal trauma: responses in the periodontium to occlusal forcesperiodontium to occlusal forces

Clinical diagnosis of occlusal traumaClinical diagnosis of occlusal trauma

• Pain, discomfort from damaged supporting tissues

• Tooth mobility, fremitus, migration

Radiographic evidence of occlusal Radiographic evidence of occlusal traumatrauma

Loss of continutity of the lamina duraFunel like changes in the periodontal ligament

space adjacent to the alveolar crestFurcation rarefactionVertical bone lossHypercementosisPulp stonesRoot resorptionCondensation of trabecular boneGingival recession

Range of clinical responses and therapeutic Range of clinical responses and therapeutic outcomes from traumatic occlusal forcesoutcomes from traumatic occlusal forces

Traumatic stimulus

Acts on Elicits range of changes

Therapeutic outcomes

Occlusal parafunction: mainly bruxism of the grinding variety with its implied horizontal force components. Effects of such forces will depend on their magnitude, frequency, and duration, as well as as their direction

Limited area of periodontium: reduced number of residual teeth

1. No clinical adaptation

2. Clinical response: mild pain or discomfort, mobility or fremitus

3. Overt clinical response: increasing mobility or fremitus, undermined function or comfort

1. none2. Usually self limiting, but should be treated if a iatrogenically caused3. Optimization of stress distribtuion:A,occlusal adjustment therapy B,interocclusal appliance therapyC,Prosthodontic therapyD,Minor orthodontic therapy

Traumatic stimulus

Acts on Elicits range of changes

Therapeutic outcomes

Occlusal parafunction: mainly bruxism of the grinding variety with its implied horizontal force components. Effects of such forces will depend on their magnitude, frequency, and duration, as well as as their direction

Large area of periodontium is intact

1.No clinical response: adaptation2.Mild clinical signs or symptoms

1.None2.Optimization of force distribution

Limited to large area of periodontal support that has been compromised by the effects of periodontitis

1.Mobility response magnified; increasing mobility or fremitus2.Other sequelae of periodontitis are not enhanced

1.Stabilizatio of occlusion and optimization of force distribution with least possible interference to plaque control and periodontal maintenance2.Control of inflammatory process resulting from the periodontitis

Problems related to the occlusal Problems related to the occlusal functionfunction

• Degenerative joint disease• Rheumatoid arthritis

• Traumatic joint disease

• Internal derangement of the TMJ

• Congenital TMJ anomalies

• Postnatal growth disturbances of the TMJ

Degenerative joint disease (arthrosis, Degenerative joint disease (arthrosis, osteoarthrosisosteoarthrosis, osteoarthritis, , osteoarthritis,

degenerative arthritis)degenerative arthritis)

• Non-inflammatory disease

• Deterioration and abrasion of the articular soft tissue surface with simultaneous remodelling of the underlying bone

• A secondary synovitis can occur resulting in pain and fibrosis leading to capsular contraction

• Single joint is affected (seldom generalized)

• Frequency is higher in women and increases with age

Etiology of osteoarthritisEtiology of osteoarthritis• Age??? • Gender???• Mechanical overloading of the joint

– Contralateral side joint recieves larger forces during the movements

– Correlation between dental attrition and surface changes of the bone

– Tooth loss correlates with macroscopic TMJ-lesions (missing molar support)

• Muscular hyperactivity (bruxism)• Chronic unilateral chewing• Deformity

– Trauma– Congenital

Symptoms of osteoarthritis in the Symptoms of osteoarthritis in the TMJTMJ

• Pain, stiffness, difficulties in the mouth opening

• Grating noise in the later progress

Clinical signsClinical signs of osteoarthritis in the TMJ of osteoarthritis in the TMJ

• Crepitation (about 25% of the population in Sweden) coincides with the grating sound

• Tenderness to palpation of the TMJ and the muscles

• Reduced mobility of the TMJ

• Reduced range of movement of the mandible

• Pain and deviation on mandibular movements

• Radiographic changes

Radiographic signs of osteoarthritis in Radiographic signs of osteoarthritis in the TMJ:the TMJ:

signs of degeneration and remodellingsigns of degeneration and remodelling• Reduced joint space• Subcortical sclerosis• Flattening of the lateral parts of the joint• Marginal osseous outhgrowths (osteophytes) • Intraosseous destructions (cyst in the condyle)

• Arthrography: Injection of a radiopaque dye into one or both joint compartments– Evaluation of disk perforation or structural damage

of the soft tissue articular surface

Rheumatoid arthritisRheumatoid arthritis• Polysystemic autoimmune

disease• Progressive inflammatory

destruction of the cartilage and the bone may lead to the ankylosis of the joint surfaces

• TMJ symptoms are relatively rare

• Pain at rest and at movements

• TMJ tenderness at palpation and crepitation

• Severe anterior bite during opening due to the bilateral condylar destruction

• Anterior open bite• Radiographic signs:

– Reduced joint space– Marginal erosion of the

cortical lining– Subchondral cystic reduction– Complete loss of the condyle

Traumatic joint diseaseTraumatic joint disease

• Inflammatory response to an excessive external trauma to the joint tissues (history!)

• Complications: – Subcondylar or intracapsular fracture

• Soft tissues may be torn, intracapsular bleeding , oedema can occur, joint effusion

• Painful limitation of movement, joint swelling, tenderness

Internal derangementInternal derangement

• Changes in the normal disk-condyle relationship

• Anterior, posterior, lateral or medial disk displacement

• Pain and functional disturbances

Anterior dislocation of the diskAnterior dislocation of the disk• Acute: ruptured or stretched posterior

attachement because of trauma to the mandible (accident,extraction, intubation)– Pain – Reduced mouth opening capacity– Limited lateral excursion

• Chronic cause: chronic reciprocal joint clicking both on opening and on closing due to microtrauma: – Loss of posterior teeth– Parafunctional muscle hyperactivity– Occlusal interferences resulting in posterior displacement

of the mandible

Diagnosis of the ”closed lock”Diagnosis of the ”closed lock”• 1. history of clicking which suddenly disappears

and changes to severe difficulty in opening the mouth widely

• 2. reduced mouth opening due to reduced mobility of one or both joints (25- 30mm)– Deviation during opening

– Pain at passive opening

• 3. radiographically increased space between the articular eminence and the condyle– Arthrography

– Double contrast arthrotomography