Vertical Jaw Relation

Presented by :

Aravind.M | IVBDS|2007 batchUnder the guidance of Dept. of prosthodontics

RELATION

Jaw Relation

Any spatial relationship of the maxilla to the mandible or any one of the infinite relationships of the mandible to the maxilla.

MAXILLO – MANDIBULAR RELATION

Jaw Relation

Orientation Jaw relation

Vertical Jaw relation

Horizontal Jaw relation

Vertical Jaw Relation / Vertical Dimension

• Vertical dimension refers to the length of the face.

• It is maintained either by the occlusion of the teeth or the balanced tonic contraction of the opening and closing muscles of mandibular movements.

SIGNIFICANCE

• Provides optimal separation between maxilla and mandible.

• If not measured accurately, the joint will be strained.

• If the VD is altered, severe discomfort to both TMJ and muscles of mastication.

FACTORS AFFECTING VD

• Tooth : Acts as a vertical stop.

• Musculature : Opening and closing muscles tend to be in a state of minimal tonic contraction.

Two measurable lengths of the face are important guides in making maxillo -mandibular relation records and are referred to as :

• Vertical dimension of rest or physiologic rest position. (VDR).

• Vertical dimension of occlusion (VDO).

Vertical dimension of physiologic rest position (VDR)

• Vertical separation of the jaws when the opening and closing muscles of mandible are in a state of minimal tonic contraction sufficient only to maintain posture.

Physiologic rest position

• The position assumed by the mandible when the head is in an upright position, the muscles are in equilibrium in tonic contraction and the condyles are in a neutral unstrained position is the physiologic rest position of the mandible.

Vertical dimension of occlusion (VDO)

• Vertical separation of the jaws when the teeth or occlusion rims are in contact.

Interocclusal Distance (IOD)

It is generally considered that the teeth

should not be in contact when the jaws are at the

vertical dimension of rest position. The 2 to 4mm

distance between the upper and lower teeth when the

mandible is at physiologic rest position is called

interocclusal distance (IOD) frequently referred to as

the “free way space”.

FREE WAY SPACE

VDR = VDO + IOD

VDR – IOD = VDO

EFFECTS OF ALTERED VD

INCREASE IN VDO / DECREASE IN IOD

• The chin-nose distance will increase, and then patients will have an appearance of open mouth.

• Constant pressure to the basal seat area which will lead to bone resorption.

• Soreness of the tissues of the basal seat.

• “Clicking”, of dentures during speech.

• Improper phonetics

DECREASE IN VDO / INCREASE IN IOD• Potentially damaging to the TMJ.

• The normal tongue space is limited. Facial

distortion appears more noticeable with over

closure that with the slightly opened closure

because with over closure the chin appears to be

closer to the nose, the commissure of the lips turns

down and the lips lose their fullness.

• The muscles of facial expression lose their tonicity

and the face appears flabby instead of firm and full.

• Over closure of jaws may lead to angular chelitis

METHODS OF DETERMINING VDR

• FACIAL MEASUREMENT AFTER SWALLOWING AND RELAXING.

• SPEECH

• TACTILE SENSE

• MEASUREMENT OF ANATOMICAL LANDMARKS

• FACIAL EXPRESSION.

FACIAL MEASUREMENTS AFTER SWALLOWING AND RELAXING

• Patient is asked to sit upright and comfortably, eyes looking straight ahead.

• Insert maxillary occlusal rim.• Place 2 points of reference.• Instruct the patient to wipe his lips

with his tongue, to swallow and to drop his shoulders – rest position.

• Measure - repeat and take average.

TACTILE SENSE

• Instruct the patient to stand erect and open the jaws wide until strain is felt in the muscles.

• When the opening becomes uncomfortable, ask him to close slowly until the jaws reach a comfortable relaxed position.

• Measure the distance and compare it.

SPEECH

2 methods:

• 1st method : Ask the patient to repeatedly

pronounce the letter ‘M’, a certain number of times. Distance is measured immediately after the patient stops.

• 2nd method: keep talking to the patient and

measure the distance immediately after the patient stops talking.

ANATOMIC LANDMARKS

• Distance between the pupil of the eye and Rima oris and the distance between anterior nasal spine and lower border of mandible is measured using Willis guide.

• If both the distances are equal, jaws are considered at rest.

FACIAL EXPRESSION

• Patients jaw will be in rest position when he is relaxed.

• Skin around the eyes and chin should be relaxed.

• Nostrils are relaxed and breathing is unobstructed.

• Upper and lower lips have slight contact in one plane.

METHODS OF DETERMINING VDOa) Mechanical methods• Ridge relation

Distance from incisive papilla to mandibular incsiors.

Parallelism of ridges.

• Pre-extraction records: Profile photographs Profile silhouettes Radiography Articulated casts Facial measurements

• Measurement from former dentures

b)Physiological methods

• Power point• Using wax occlusal rims• Physiological rest position• Aesthetics• Swallowing threshold• Tactile sense or neuromuscular

perception• Patient’s perception of comfort.

MECHANICAL METHODS

Ridge relation :Defined as positional relationship of

the mandible ridge to the maxillary ridge.

a) Distance from the incisive papilla to the mandibular incisors.

• The distance of the papilla from the incisal edges of lower anterior teeth averages approximately 4mm in natural dentition. The incisal edges of the maxillary central incisors are an average 6mm below the incisive papilla. Based on this value VDO can be calculated.

b) Parallelism of the ridges: • Sears suggested that correct

vertical dimension of occlusion is at a point where the jaws are parallel with a 5 degree opening in the posterior region.

Measurement of the former dentures:• A Boley’s gauge is used to measure

the distance between the border of the max and mand denture ,when the dentures are in occlusion.This measurement is used to determine the VDO.

Pre extraction records Profile radiographs :• Made with teeth in occlusion.

These are compared with those made with occlusion rims in position.

• DISADV- Time consuming, Image distortion, Radiation hazard.

Profile Photographs • Taken in maximum occlusion of

teeth. The photographs should be enlarged to the actual size of the patient. The distance between the two anatomic landmarks is then compared with that of patient to avoid errors.

Casts of the teeth in occlusion

Facial Measurements:Tatoo points are marked

on tip of the nose and base of the chin. The vertical dimension between the anatomic landmarks is then compared with that of patient to avoid errors. Willis gauge is also used to measure facial dimension . One arm contacts the base of the nose and the other arm contacts the base of the chin.

PHYSIOLOGIC METHODS

Niswonger’s method(1934) :• Two markings are made , one on the

upper lip below the nasal septum, and the other on the chin.The patient is told to swallow and relax. The distance between the marks is measured. The occlusal rims are adjusted until the distance between the marks is 2-4 mm less during occlusion.

• Disadv- The marks move with the skin.

Phonetics and esthetics.

The dentist asks the pt to speak certain words and then makes certain observations of the relationship of the occlusion rims to each other and to the lips.

Using ‘m’sound: The pt repeats the

letter ‘m’. When the lip just touches ask the patient to hold the jaws still. The distance between tip of the nose and chin is measured (VDR).The occlusion rims are adjusted and again measured. The second measurement should be 2-4mm less than the first measurement(VDO)

The ch,s,and j sounds:• There should be 1mm space between

the occlusion rims in the anterior area at correct VDO.

Using 33 :• When repeating this word there

should be enough space for the tip of the tongue to protrude between the anterior teeth.

Using f or v sounds:• The max incisors/occlusion rims

should lightly contact the lower lip at the vermillion border when pt pronounces these words.

SILVERMAN’S CLOSEST SPEAKING SPACE

• The 2mm space between the incisors at correct VDO when pt pronounces words containing ‘S’ eg.

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

ESTHETICS

In normal relaxed position the lips are even anteroposteriorly and in slight contact. If the face appears strained the vertical height may be more. If the corners of the mouth droop, making the chin appear too close to the nose, then vertical dimension may be too less.

Swallowing threshold.

The technique is based on the fact that when a person swallows, the teeth come together with a very light contact at the beginning of the swallowing cycle. If the occlusion rims do not come into contact during swallowing then the VDO is less.

Method: Cones of soft wax

having excessive height are placed on the lower base. Salivation is stimulated ( using candy) and the pt is instructed to swallow. The repeated swallowing reduces the height of the wax to the occlusal vertical dimension.

• Tactile sense and Patient- perceived comfort.

The pt’s tactile sense is used as a guide to the determination of the correct vertical dimension. Using a central bearing plate attached to mand: occlusion rim and central bearing screw attached to max: occlusion rim, VD is increased too high. Then in progressive steps the screw is adjusted downward until the pt signifies overclosure. The procedure is then reversed until the pt signifies that its just right.

• BOOS BIMETER(POWER POINT)Boos(1940) stated that

maximum biting force occurs at VDO.A device that measures the biting force (Bimeter) is attached to the mand: record base and a metal plate to maxillary.A screw is turned to adjust the vertical relation . The maximum power point on the gauge indicates the correct VDO.

• Electromyography • Rest position can be determined by

recording the minimal activity of muscles of mastication.

• SCRIBING GUIDE LINES

Its Over