vertical jaw relations/ dentistry course in india

Vertical Jaw

Relations

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According to GPTVertical jaw relation are those

established by the amount of separation of maxillae & mandible under specific conditions.


The physiologic rest position of the mandible as related to the maxillae and the relations of the mandible to the maxillae when the teeth are in occlusion are the two dimensions of jaw separation of primary concern in complete denture construction.


Thus Vertical Jaw Relations are classified as

(1) The Vertical Relation of Rest position

(2) The Vertical Relation of Occlusion and

(3) The differences between the vertical relation of rest and the occluding vertical relation, the “Interocclusal Rest Space” also known as “Freeway Space”


According to GPT :“Physiologic rest position” is

The postural relation of the mandible to the maxillae when the patient is resting comfortably in the upright position and the condyles are in a neutral unstrained position in glenoid fossa.


When observations of physiologic rest position are being made, the patient’s head should be upright and unsupported.


The force applied by the jaw opening muscles is added to the force of gravity, when the head is upright.

In a reclining patient, gravity does not pull the mandible down and so one may find the distance between the jaws to be less than it is when the head is upright.


Rest vertical dimension = Occlusal vertical dimension + Interocclusal distance.

During the construction of complete dentures, the Rest Vertical Dimension is determined first and then reduced or closed to the Vertical Dimension at occlusion.


The second thing that establishes the vertical relation of the mandible to the maxillae is the occlusal stop provided by teeth or occlusion rims.


Vertical dimension of occlusion:It is defined as the distance measured

between two points when occluding members are in contact (GPT 99).


“Why is interocclusal space necessary???”The health of the periodontal

membranes that support the natural teeth and the health of the mucosa of the basal seat for dentures depends on rest from occlusal forces to maintain their health.


For this reason, an interocclusal rest space between the maxillary and mandibular teeth is essential for the opening and closing muscles and gravity to be in balance when the muscles are in a state of minimum tonic contraction.


The interocclusal rest space is the difference between the rest vertical relation and the occlusal vertical relation and amounts to 2-4 mm in a vertical direction if observed at the position of the first pre molars.


Once the vertical relation of rest position has been determined, it is easy to adjust the vertical relation of the occlusion rims sufficiently to provide for the necessary interocclusal distance.


Methods To Record Vertical JawRelation


The methods for determining the vertical Maxillomandibular relations can be grouped roughly into two categories

(1) Mechanical methods(2) Physiologic methods

The use of esthetics as a guide combines both the mechanical and the physiologic approaches to the problem.


MECHANICAL METHOD Ridge relationsA) Distance of incisive papilla from

mandibular incisors. The incisive papilla is used to measure the patients vertical relation since it is a stable land mark and is changed little by resorption of the residual alveolar ridge.


The distance of the incisive papilla from the incisal edge of the mandibular incisors is about 4 mm in the natural dentition.

The incisal edge of the maxillary central incisor is an average of 6mm below the incisive papilla


So the average vertical overlap of the opposing central incisor is about 2 mm.

The disadvantage of this method is the absence of lower teeth and so is useful in treatment of single dentures


: B)Parallelism of the ridges

Paralleling of the ridges, plus a 5 degree opening in the posterior region as suggested by Sears, often gives a clue to the correct amount of jaw separation.


This theory if used alone, is not reliable, because many patients present such marked resorption that the use of this rule would generally close the vertical relation.

But when considered with other observations, it may be of value.

However, in most patients the teeth are lost at irregular intervals and the residual ridges are no longer parallel.


2) Measurement of former dentures:

Measurements are made between the borders of the maxillary and mandibular dentures by means of a boley gauge and corresponding alterations can be made in the new denture to compensate the occlusal wear.


If the teeth click or if the closest speaking space is obliterated during speech, the Vertical Dimension should be reduced and the amount of reduction is determined arbitrarily.


Measurement of former dentures using Boley’s gauge


3)Pre-extraction records :

It is frequently possible to see the patient before he or she becomes edentulous. In such cases, one can usually establish the occlusal position, record it in some manner and transfer this record to the edentulous situation. This is a relatively easy procedure and can be accomplished in several ways.


A)Profile radiograph: The exposure of a full lateral radiograph

is made with the teeth in occlusion, and after extraction occlusion rims are made to an apparently correct vertical relation.

They are inserted, the patient closes on them and another radiograph is taken.

The two films are compared and any necessary adjustment is made to bring the mandible in correct position as in the initial film.


Radiographs:


DisadvantagesAdditional Patient exposure to radiation.Additional time (Time consuming)Conventional radiographic equipment used

to provide profile R/g is not available in most dentists offices.

Inaccuracy due to enlargement of the image


B) Profile photographs

Profile photographs are made and enlarged to life size.

Measurements of anatomic landmarks on the photograph are compared with measurements using the same anatomic landmarks on the face


The photographs should be made with the teeth in max occlusion

This was explained by W.H. Wright in 1939 certain measurements made from previous patients photographs to measurements on the patients face, such as interpupillary distance and the distances from lop of the eyebrows to the base of the chin.


These measurements can be compared when the records are made and again when the artificial teeth are tried in.

Disadvantage of this method is that the angulations of the photograph might differ with the patients.


.C) Profile Silhouettes:An accurate reproduction of the profile

in silhouette can be cut out in cardboard or contoured in wire.

The silhouette can be repositioned to the face after the Vertical Dimension has the established at the initial recording and / or when the artificial teeth are tried in


i)Lead wire adaptation: Lead wires may be adapted carefully to

pre extraction profiles, and this contour is transferred to a cardboard.

The resultant cutout is stored until after extraction.


When the dentist estimates the vertical relation using the trial plates, the cardboard cutout is placed against the profile in order to see whether the facial contour has been maintained or re-established.

It is not in common use today.


ii)Swenson’s method(1959): ...

Swenson suggested that acrylic resin face masks made before the extraction and later when the patient is rendered edentulous, it is fitted on the fact to see whether the vertical relation has been restored properly.

This method is rather impractical because it requires a great deal of time and is little more accurate than the lead–wire technique.


Swenson’s method (1959)


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Drawbacks of this method It is time consuming Requires lot of skill and experience

with the use of facial impressions and casts for the fabrication of artificial facial parts

Lastly the face assumes a different topography in the erect posture from that in the recumbent or semi-recumbent position


D)Facial Measurements : Various devices for Matching facial

measurements have been used in many different forms.


i) The Dakometer


ii) Willi’s gauge: This instrument is used for recording

vertical height before extraction. The arm is placed in contact with the base of the nose, and the arm is moved along the slide till it lightly but firmly touches the lower border of the chin.


It is locked in position by the screw. The distance on the scale is recorded on the patient’s chart.

It is not an accurate method as there may be variations is applying pressure


G) Articulated casts: These are of practical value in the

assessment of the vertical relation. Measurements can be made of the casts in occlusion and relatively stable points.

Such as the incisive papilla and the crest of the lower ridge the sulcus depth, the extended height of the upper and lower buccal frena or the hamular notch and retromolar pad.


The casts also assist in the selection of size, shape and position of the teeth.


4)POST EXTRACTION METHODS a) Niswonger’s method: Niswonger in 1934 suggested a method for

determining the vertical dimension that is commonly used today.

The patient is seated so that the Ala-Tragal line is parallel with the floor.

Two markings are made, one on the upper lip below the nasal septum other in the most prominent part of the chin.


The patient is told to swallow and relax.

The distance between the marks are recorded.

Subsequently, the occlusion rims are constructed so that when they occlude, the measured distance is 1/8” less than the original measurement.

This 1/8” average freeway space falls within 2-4 mm.


This method has the disadvantage that the marks moves with the skin and sometimes it is difficult to obtain two constant measurements of the rest position.

However, when combined with other observations this technique is reasonably reliable.


b)Willi’s method: Willis believed that the distance from the pupil of the eye to the rima oris should be equal to the distance from the base of the nose to the inferior border of the chin, when the occlusion rims are in contact.


c)Concept of equal-thirds Some observers suggested that the face

can be divided into equal thirds, the forehead, the nose and the lips and chin. This concept is of little practical value for a variety of reasons


d)Silverman’s closest speaking space which measures the vertical relation in the phonetic method must not be confused with the freeway space. The freeway space established vertical relation when the muscles involved are at minimal tonic contraction and the mandible is in its rest position.


The closest speaking space measures the vertical relation when the mandible and muscles involved are in physiologic function of speech.


The occlusion rims are placed in the mouth and the height is adjusted until a min of 2 mm of space exists when the patient pronounces the letter ‘s’.

It may vary from 1-10mm, but the 2mm average will generally prevent an increase in vertical relation.

Disadvantage of this method is that the patient who has 8– 10 mm closest speaking space will require other means for determination of the vertical relation.


e) Boos method (Power point) Boos (1940) found that there is a point of maximum biting power. He states that the patient registers the greatest amount of pressure on a spring dynometer at a point considerably more open than the denture occlusion.


The bimeter is attached to an accurately adapted mandibular record base.

A metal plate is attached to the vault of an accurately adapted maxillary record base to provide a central bearing point.


The vertical relation is adjusted by turning the cap.

The gauge indicating the pounds of pressure generated during closure at different degrees of jaw separation


When the maximum power point has been determined the set is locked. Plaster registrations are made and the cast is transferred to an articulator.

Investigators agree that such a device

offers no more accuracy than Niswonger’s or Silverman’s method.


: 6) Lytle’s method (Neuromuscular perception) The patients tactile sense is used as a

guide to determine the correct occlusal vertical relation

An adjustable central bearing screw is attached in the palate of maxillary occlusion rim and a central bearing plate in the mandible.


The screw is adjusted first so it is obviously too long .Then in progressive steps the screw is adjusted until the patient indicates that the jaws are closing too far.

The procedure is repeated until patient indicates that the teeth feel too long.

The screw is then adjusted until the patient indicates that the length feels right

.


This method is not very effective with senile patients or those who have impaired neuromuscular coordination


G)Electromyography

Rest position of the mandible can be determined by means of electromyography which would record the minimal activity of the muscles. All muscles show greater activity in other positions than in rest position.


Physiologic Methods: 1) Physiologic rest position:

Registration of the jaws in physiologic rest position gives an indication to a relatively correct vertical relation when used with other methods. After the insertion of the occlusion rims into the patient’s mouth, the patient is asked to swallow and let the jaws relax.


Then the lips are carefully parted to see how much space is present between the occlusion rims. The patients must allow the dentist to separate the lips without moving the jaws or lips. This interocclusal rest space should be between 2-4 mm when viewed in the premolar region.


The interarch space and rest position can be measured by indelible dots or adhesive tapes on the face. If the difference is greater than 4mm the occlusal vertical relation would be considered too small. If the occlusal vertical relation is less than 2mm the occlusal vertical relation would be assumed to be too great.


2) Phonetics:

Speech is used as an aid in determining the vertical relation.

Phonetics tests of vertical dimension consist more of listening to speech sounds production than of observing the relationship of teeth during speech


The patient is asked to repeat the letter ‘M’ until he is aware of the contacting of the lips.

The patient is asked to stop all jaw movements when the lips touch and the distance between the two points of reference are measured.


If the anterior teeth touch when these sounds are made, the vertical relation of occlusion is probably too great.

Likewise the occlusal vertical relation is also considered to be too great if the teeth click together during speech.


The position of the tongue and the relation of the teeth is also an imp factor.


3)Facial expression:

The experienced dentist learns the advantage of recognizing the relaxed facial expression when the jaws are rest. A study of the skin of the lips compared to the skin over other parts of the face can be used as guide normally the tone of the skin should be same throughout.


However, it must realized that the relative anteroposterior positions of the teeth are at least equally involved in the vertical relations of the jaws as in the restoration of skin tone.


The contour of the lips depends on their intrinsic structure and support behind them.

Therefore the dentist must initially contour the labial surfaces of the occlusion rims so they closely simulate the anterioposterior tooth positions and the contour of the denture base which in turn,must replace or restore the tissue support provided by the natural structures.


The skin around the eyes and over the

chin will be relaxed. Relaxation around the nares reflects

unobstructed breathing.


Based on harmony of face


4)Swallowing threshold:

The position of the mandible at the beginning of the swallowing act has been used as a guide to the vertical relation.


The theory behind the methodis that when a person swallows, the

teeth come together with very light contact at the beginning of the swallowing cycle.


The technique involves building a cone of soft wax on the lower denture base so that it contacts the upper occlusion rim with the jaws too wide open.


The flow of saliva is stimulated and the repeated action of swallowing will gradually reduce the height of wax cone to allow the mandible to reach the level of occlusal vertical relation.

The length of time this action is carried out and relative softness of the wax cone will affect the results.


The length of time this action is carried out and the relative softness of the wax cone will affect the results

It is difficult to find consistency in the final vertical positioning of the mandible by this method.


Maxillary occlusion rim should be checked for Labial fullnessHeight of occlusal rimAnterior planeAnteroposterior planeMidline High lip lineCanine lines


Labial fullnessThe lip is normally supported by the

alveolar process and teeth which,at this stage,are represented by the denture base and occlusion rim.

Therefore the labial surface must be cut back or added to until a natural and pleasing position of the upper lip is obtained.


The upper lip may appear too full because the lower lip at this stage is unsupported.


The height of occlusal rimThe incisal edges of the maxillary incisors

will be at the same position as the occlusal surface of the maxillary occlusal rim.

There are a number of variations ,which should act as guide rather than a rule,depending on the patient

In most old people less tooth will be visible owing to attrition of natural teeth and some loss of tone of orbicularis oris muscle


The anterior planeThe upper anterior teeth are set with their

incisal edges in the same position as the occlusal surfaces of the rim it is important for the anterior plane of the rim to be trimmed to this level.

Generally the plane to which the anterior teeth to be set and to which the rim must be trimmed is parallel to an imaginary line joining the pupils of the eyes.


Anterior posterior planeThis plane indicates the position of the

occlusal surfaces of the posterior and is obtained in conjunction with the anterior plane.

The rim is trimmed parallel to ala-tragal line.Studies have shown that the occlusal plane

of the natural teeth is usually parallel to this line.


MidlineFew human faces are symmetrical therefore

there is no hard and fast rule for determining midline.

Following aids help in deciding the vertical line on labial surface of upper rim


Imaginary line from center of brows to center of skin

Immediately below center of philtrumAt the bisection of the line from corner to

corner of the mouth when lips are relaxedwhere it crossed by a line at right angles to

the inter pupillary line from a point midway between the pupils when the patient is looking directly forward


Lip lineLip line is a straight line just in contact

with the inferior border of the upper lip when relaxed

High lip line is a line just in contact with the lower border of the upper lip when it is raised as high as possible unaided such as in smile or laughing


High lip line indicates the amount of denture which may be seen in normal conditions and thus assists in determining the length of tooth needed.


Mandibular occlusion rimIs trimmed so that when it occludes

evenly with the maxillary rim as a guide at correct vertical height


EFFECTS OF INCREASED VERTICAL RELATION 1) Discomfort to the patient

2) Trauma: by the jamming effect of the teeth coming into contact sooner than expected may cause not only discomfort, but also pain owing to the brusing of the mucous membrane by these sudden and frequent blows.


3)Loss of freeway space: which may be due to

(a) muscular fatigue of any one or group of muscles of mastication. (b) Trauma caused by the constant pressure on the mucous membrane and(c) Annoyance from the inability to find a comfortable resting position.


4)Clicking teeth – The tongue which has become accustomed to the presence of teeth in certain fixed positions and during speech helps to produce sounds without the teeth coming into contact. When there is increase in vertical height opposing cusps frequently meet each other, producing an embarrassing clicking or clattering sound. This effect is also produced during eating.


5)Appearance – The face has an elongated appearance since, at rest the lips are parted and closing them together will produce an expression of strain.

6)Bone - Residual alveolar bone undergoes rapid resorption


EFFECTS OF DECREASED VERTICAL RELATION:

1)Inefficiency – which is due to the fact that the pressure with which it is possible to exert; with the teeth in contact decreases considerably with over closure because the muscles of mastication act from attachments, which have been brought close together.


2) Cheek biting – In come cases where there is a loss of muscular tone, as well as reduced vertical height, the flabby cheek tends to become trapped between the teeth and bitten during mastication.


3)Appearance: The general effect of overclosure on facial expression is of increased age. There is close approximation of nose to chin, the soft tissues sag and fall in and the lines on the face are deepened. The lips loose their fullness and the vermillion borders are reduced to approximate a line.


4) Angular cheilitis : A reduced vertical relation results in a crease at the corners of the mouth beyond the vermillion border and the deep fold thus formed becomes bathed in saliva, thus leading to infection and soreness.


5) Pain in the TMJ: Trauma in the region of the temporomandibular fossa may be attributed to a reduced vertical relation with symptoms like obscure paints, discomfort, clicking sounds, headaches and neuralgia.


6)Costen’s syndrome: is stated to be the result of prolonged overclosure.


CONCLUSION

The establishment of the vertical maxillomandibular relations is a phase of prosthodontic treatment for edentulous patients in which it is difficult to arrive at definite conclusions from a practical view point.


Since there is no precise scientific method of determining the correct vertical relations, the registration of vertical relations depends upon the clinical experience and judgment of the dentist rather than a science.

This could be the reason why there are dozens of methods in use and why one method is as good as another.


BibliographyProsthodontic treatment for edentulous

patients – BOUCHER, 11th Edition.Syllabus of complete dentures –

HEARTWELL ,4th Edition.Essentials of complete denture –

WINKLER.Complete Denture Prosthodontics- John J

SharryClinical Dental Prosthetics - H.R.B Fenn


Clinical assessment of vertical dimension. JPD 1972,VOL 28(3), 238-246.

Variations in mandibular rest position with and without dentures in place. JPD 1976,VOL 36, 159.

Clinical study of rest position using kinesiograph and myomonitor. JPD 1979, VOL 41, 456.

Head angulation and variation in maxillomandibular relationship, Part-I : The effect on vertical dimension of occlusion. JPD 1983, VOL50 96.


Relationship of head posture and rest position of mandible. JPD 1984 VOL 52 ,111.

Determination of vertical dimension at rest. A comparative study.JPD 1987, VOL 59, 238.

Determination of vertical dimension of occlusion : A literature review.JPD 1988, VOL 59,

327.


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