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HORIZONTAL JAW RELATION

Once the correct vertical dimension is

determined and allowance for the necessary

interocclusal distance or freeway space has

been made, the jaw relation in the horizontal

plane must be established.

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HORIZONTAL JAW RELATIONCENTRIC RELATION

Definition: CENTRIC RELATION:

The most retruded position of the mandible to the maxilla when the condyles are in the most posterior, unstrained position in the glenoid fossae at an established vertical dimension.

GPT

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FEATURES AND SIGNIFICANCE

It is ideal arch to arch relationship and hence optimum position of jaws for the health, comfort and function of the TMJ.

It is a mandibular position where the condyle disc assembly is seated braced in anterior-superior position against the posterior slope of the articulator eminence. Although it was believed to be the rearmost uppermost and midmost in the glenoid fossa. (RUM POSITION)

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Centric relation is related to terminal hinge axis.

In centric relation condyles exhibit pure rotation without any translation.

It is a reproducible position which can repeatedly arrived at and thus serves as a reliable guide to develop centric occlusion in artificial dentures.

It is a starting point for the arrangement of artificial teeth to develop maximum intercupsation in complete denture.

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It is also serves as a reference position for the institution of occlusal rehabilitation in dentulous conditions.

The terminal act of masticatory stroke terminates in centric relation. It is also a position where upper and lower teeth are traced against each other during deglutition.

Centric relation is a reproducible and stable position. Therefore it is used as a reference when mounting dentulous and edentulous casts onto articulator.

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5R

Recordable

Reproducible

Retruded

Reference

Relation

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METHODS OF RECORDING CENTRIC RELATION

I. FUNCTIONAL CHEW – IN METHODS

I. Needle – house technique

II. Patterson's method

II. GRAPHIC METHODS

I. INTEROCCLUSAL CHECK RECORD METHOD

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FUNCTIONAL CHEW-IN METHODS

In tooth, the methods patient produces a pattern of mandibular movements by moving the mandible to protrusion, retrusion and right and get lateral.

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NEEDLE – HOUSE METHOD

They used compound occlusion rims with four metal styli placed in the maxillary rim.

When the mandible moves with the styli contacting the mandibular rim, the styli cut four diamond shaped tracings.

The tracings incorporate the movements n three planes and the records are placed on a suitable articulator to receive and duplicate the record.

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PATTERNSON’S METHOD The Patterson method uses wax occlusion rims.

A trench is made in the mandibular rim and a mixture of half plaster and half carborundum paste is placed in the trench.

Mandibular movements generate compensating curves in the plaster and carborundum.

When the plaster and carborundum are reduced to the predetermined vertical dimension of occlusion, patient s instructed to retrude the mandible and the occlusion rims are joined together with metal staples.

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GRAPHIC METHOD The most common form of exclusive recording

is the Gothic arch tracing.

It indicated the horizontal relation of the mandible to the maxillae.

Extraoral

Gothic arch tracing

Intraoral

Basic purpose of training is to record the protrusive and lateral records.

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EXTRA ORAL TRACING The extra oral tracer consist of an intraoral

equalization of pressure on the bases.

A needle like point called as styli makes the tracing on the tracing table coated with cartoon suit or wax.

These tracing are shaped like gothic arch, so they are referred to as gothic arch tracings.

They are also known as arrow print tracing.

The tracing is not acceptable unless a printed apex is develop.

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A blunted apex usually indicates an acquired functional relationship.

Sharp apex indicates position of centric relation.

Double tracings indicate lack of co-ordinated movements at a different vertical dimension.

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INTRA ORAL TRACING

The central bearing plate and point is connected to the proper vertical relation and when the rims are in place.

The patient is instructed to perform lateral and protrusive movements.

Gothic arch is traced on the plate.

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INTEROCCLUSAL CHECK RECORD METHOD

Advocated by Trapazqo and Hickey

The normal functioning of the patients proprioception and visual acuity and some touch of dentist, useful in obtaining accurate record.

The record is made by making a nick and notch on the maxillary occlusal rim.

Trough on the mandibular occlusal rim in the region of 2nd premolar and 1st molar area.

Nick should be placed in the second premolar are and notch on the 1st maxillary molar area.

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Extra amount of wax is softened and placed in the trough of lower rim.

Place the rims in the patients mouth.

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Patient is made to retrude the mandible by applying any one of the methods

a) Instruct the patient to protrude and retrude the mandible repeatedly while the patient olds the finger lightly against the chin.

b) Ask the patient to take the tongue backward to touch the posterior vibrating line and swallow and occlude.

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c.) Ask the patient to swallow repeatedly.

d.) Guide the mandible to centric by holding with the index, middle finger and thumb on the chin.

• Once the wax gets hardened remove the occlusal rim out.