Biological considerations of orientation, vertical and horizontal jaw relations in complete denture- Second part

Short Learning Objectives 1. Definition of Horizontal relation 2. Importance and Significance 3. Method of recording

Centric relation GPT 4, BOUCHER The horizontal jaw relation when the condyles are in the most posterior, unstrained position in the glenoid fossa at any given degree of jaw separation from which the lateral movements can be made. BOUCHER The most posterior relation of the lower to the upper jaw from which lateral movements can be made at a given vertical dimension .

GPT- 8 definition The maxillomandibular relationship in which condyles articulate with the thinnest avascular portion of their respective disc with the complex in the anterior superior position against the slopes of articular eminences. . This position is independent of tooth contact. . This position is discernible when the mandible is directed superiorly and anteriorly. . It is restricted to a purely rotary movement about the transverse horizontal axis.

Importance of centric relation Centric relation is a reproducible and stable and comfortable position.Therefore it is used as a reference when mounting dentulous and edentulous casts in articulator.Thus CR serves as a reference relationship for establishing an occlusion. When CR and CO of artificial teeth do not coincide the stability of denture bases is in jeopardy and patient will have unnecessary pain or discomfort.

3 primary requirements: To record the correct horizontal relationship of mandible to maxilla To expert equalized vertical pressure To retain record in undistorted condition until the cast have been accurately mounted on articulator

SIGNIFICANCE In case of dentulous patients proprioceptive impulses are obtained from PDL. In case of edentulous patients centric relation act as proprioceptive centre to guide occlusal movements.

SALIENT FEATURES: 6 R 1- Retruded 2. Repeatable 3. Recordable 4 SALIENT FEATURES: 6 R 1- Retruded 2. Repeatable 3. Recordable 4. Reproducible 5. Point of return 6. Point of reference.

Effective manipulation of mandible requires delicacy and firmness. METHODS FOR ASSISTING THE PATIENT TO RETRUDE THE MANDIBLE. Relaxing the jaw and closing Repeatedly protruding and retruding the mandible Swallowing and closing Tapping the rims or back teeth repeatedly Touching the tip of the tongue to the posterior aspect of the palate or denture border and bite. Palpate the temporal and massater muscles to relax them.

METHODS TO RECORD CENTRIC RELATION: Physiological or tactile or inter occlusal check record method FUNCTIONAL Needle house method Patterson method GRAPHIC Intra oral Extra oral

Physiologic method Based on: Proprioceptive impulse of patient Kinethetic sense of mandibular movement Visual acuity and sense of touch of patient Technique is divided into two steps in edentulous condition- • Tentative records using occlusion rims attached to accurate stable record bases. • Inter occlusal check records with the teeth arranged for try in.  

INDICATIONS Abnormally related jaws. Displaceable flabby tissue. Large tongue Uncontrolled mandibular movements. In patients already using a complete denture

Material used Waxes: low fusing Impression compound Dental plaster ZnOE paste

PROCEDURE Recording tentative jaw relation: Maxillary occlusal rim inserted to patients mouth. Vertical dimension at rest is established. Mandibular occlusal rim inserted and reduced accordingly, Using base plate wax, make a tentative CR record by having the patient retrude close the jaws until he feels the closure to be at tentative vertical dimension of jaw separation.

b) Making the inter occlusal check record. Upper and lower trial dentures are inserted into the mouth. Do not let the patient make tooth contact. If premature tooth contact exists with the jaws in centric relation, the patient’s proprioception may not direct the return to this identical position. Aluwax is added on the occlusal surface of teeth of mandibular occlusal rim Patient asked to retrude mandible and close on the wax till tooth contact occurs. Trial dentures removed and allowed to cool.

Functional method Method utilize the functional movements of jaws to record the centric relation. Patient asked to perform border movements such as protrusive and lateral excersion movement. Needle house method Fabrication of occlusal rim made from impression compound Four metal beads or styli are embedded into premolar and molar areas of maxillary occlusal rim. Occlusal rim inserted into patients mouth and asked to close occlusal rim and make protrussive,retrussive ,right and left movement of mandible. When movements are made “diamond shaped marking pattern rather than a line is formed on the mandibular occlusal rim.

Patient produces mandibular movements by moving mandible to protrusion , retrusion, right and left lateral

b)Patterson method Occlusal rim made of modelling wax. In trench or trough is made along the length of mandibular occlusal rim. A mixture of carborundum and dental plaster is loaded into the trench. Perform mandibular movement till predetermined vertical dimension. Movement generates compensative curves in plaster

Graphic method The graphic method record a tracing of mandibular movements in one plane 2 types: Arrow point tracing Pantograph Arrow point tracing is a graphic record measured across single plane Pantogaph is measured three dimensionally.

Factors to be considered while carrying out tracing Stability of denture base Resistance of rims Difficulty in placing central bearing device Height of residual alveolar ridge Tongue interference Efficiency of recording device Lack of coordinated movements

Made using gothic arch tracers Recorded in horizontal plane. Consists of central bearing device:a device that provide central point of bearing or support between the maxillary & mandibular dental arches. consists of contacting point attached to one dental arch and plate attached to opposing dental arch Plate provide surface on which the tracing of mandibular movements is recorded. Consists of: CENTRAL BEARING POINT & CENTRAL BEARING PLATE.

TYPES OF ARROW POINT TRACERS: INTRA ORAL TRACING POINT: Central bearing device is located intra orally. Tracer is placed within the mouth. Central bearing point & plate is inserted into patients mouth. Central bearing point is adjusted such that it contact the central bearing plate at predetermined vertical dimension. Ask to make anteroposterior and lateral movements. Central bearing point will draw the tracing pattern on central bearing plate Tracing should resemble an arrow point with a sharp apex.

2)EXTRA ORAL POINT TRACER: Concept similar to intra oral tracer. Additionally have an attachment that project outside mouth. Record bases attached to recording devices inserted in patients mouth. Central bearing point is retracted to conduct training exercises. Recording plate which projects extra orally is coated with precipitated chalk and denatured alcohol. Patient asked to perform all movements. Examine for sharp apex.

ECCENTRIC JAW RELATION “any relationship of mandible to maxilla other than centric relation” Include protrusive and lateral relations. Help to adjust the lateral and horizontal condylar inclination in the articulator. Thus helps the articulator to reproduce eccentric movements of mandible and establish balanced occlusion. Recorded using functional or tactile method.

Take home message…. Correct recording of Jaw relation records are very essential for successful fabrication of complete denture. Failure to record properly will ultimately lead to failure of prosthesis.

Multiple Choice Questions 1. Free way space is- A. VDR-VDO B. VDO-VDR VDR- IOD VDO+IOD

2. Face bow helps to record- Vertical Jaw Relation Horizontal Jaw Relation Orientation Jaw Relation Centric Relation

3. Which of the following is not the type of Face bow- Kinematic Fascia Ear Piece Condyle

4. Average InterocclusaL distance is- 1-2mm 2-3mm 1-3mm 2-4mm

5. Face bow is helpful when change is expected in- Vertical Jaw Relation Horizontal Jaw Relation Orientation Jaw Relation Centric Relation

6. Point taken during recording orientation jaw relation are- 3-2 anterior and 1 Posterior 3- 1Anterior and 2 Posterior 4-2 anterior and 2 Posterior 2- 1Anterior and 1 Posterior

7. Graphic method is used to record- Vertical jaw relation Horizontal jaw relation Orientation jaw relation Physiological jaw relation

8. According to newer definition, centric relation is- RUM MS AS SUM

9. Patterson method, which is used to record centric relation, is- Physiological method Functional method Graphic method Radiological method

10. Which of the following is not the feature of centric relation- Retruded Repeatable Recordable rechargeable