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- S.SATHISHSELECTIVE GRINDING PROCEDURES IN COMPLETE DENTURES

INTRODUCTION

Occlusal harmony in complete denture is necessary if the dentures are to be comfortable, to function efficiently, and to preserve the supporting structures.

It is difficult to see occlusal discrepancies intra orally with complete denture.

The resiliency of the supporting soft tissues and displaceability of the tissues in varying degrees tend to disguise premature occlusal contacts.

The tissues permit the dentures to shift; as a result, after the first interceptive occlusal contact the remaining teeth appear to make satisfactory contacts. The eye cannot be relied upon to observe occlusal discrepancies, and the patient cannot be depended upon to diagnosed occlusal faults.

It is the responsibility of the dentist to find and correct these occlusal discrepancies and permit the patient to depart free of occlusal disharmony. Occlusal faults can be determined by obtaining and interocclusal record from the patient and remounting the dentures on an articulator.

These faults can be corrected by careful selective grinding procedures.

Remounting of the dentures on the articulators and selective sliding procedures should be carried out at the time of placement of the dentures.

DEFINITIONSelective grinding / Occlusal Reshaping is defined as the,

intentional alteration of the occlusal surfaces of the teeth to change their form.

GPT-8

Teeth are altered by selective grinding to make simultaneous cusp tip to cusp tip contact on both sides of the arch when the jaws are in left or a right lateral position, balanced occlusion in a static eccentric position exists. When the mandible is in a straight protruded relation with the maxilla and the posterior teeth are altered to make cusp contacts at the same time to anterior teeth make incisal edges contact , balanced occlusion protrusion exists.Occlusal interference as small as 15 micron

Problems causedTMJ PAINCompression of articular disc

WHAT IS OCCLUSION?Occlusion is defined as any (static) contact between the incising or masticating surfaces of upper & lower teeth Supported by roots that are anchored to the bone

Moves independently in their socket

Malocclusion may remain uneventful for years

Occlusal forces affect only concerned teeth

Non vertical forces tolerated better

Mastication usually done in the second molar region

Bilateral balance is not found

Proprioceptive mechanism enables the patient to avoid prematurities and gives better control

Supported by denture base placed on slippery mucosa

Moves as a unit on their base

Malocclusion evokes immediate instability & painForces acting affect the whole base

Non vertical forces not tolerated

The second premolar area is preferred for mastication

Bilateral balance is necessary for denture stabilityPoor feed-back mechanism, so neuromuscular control is compromised

Natural occlusionArtificial occlusionOcclusion in complete denturesConcepts of occlusion

1.Balanced occlusion

2.Monoplane/non-balanced occlusion

3.Lingualised occlusion Balanced occlusion Defined as bilateral simultaneous, anterior and posterior occlusal contact of teeth in centric and eccentric positions.

SIGNIFICANCE

SwallowingStabilityMaintains integrity of foundation tissuesMinimal stresses on TMJIncreased efficiency Factors affecting balanced occlusionHanaus quint

Condylar guidanceIncisal guidancePlane of occlusionCompensating curveCuspal inclination

SELECTIVE GRINDING:

Modification of occlusal & incisal surfaces of teeth at selected areas to correct occlusal errors & gain a balanced occlusion.

Necessity??Artificial teeth move about to a minor degree during festooning and while the wax denture base is being converted in to resin.

This tooth movement is due primarily to dimensional changes in the wax denture base,in the investing materials ,and in the resin denture base during curing.

Occlusal discrepancies caused by these dimensional changes ordinarily are removed before the dentures are polished.

Occlusal harmony in complete denture is necessary so that the denture will be: 1- comfortable and functions efficiently. 2- preserve the supporting structures CAUSES OF ERRORS IN OCCLUSION1) Inaccurate maxillo-mandibular relation record by the dentist. 2) Errors in the transfer of maxillo-mandibular relation. 3) ill-fitting record bases. 4) Incorrect arrangement of the posterior teeth. 5) Failure to close the flask completely during processing. 6) Warpage of the dentures by over-heating them during polishing. 7) Changes in the denture base material (dimensional changes of the acrylic dough). REVIEW OF LITERATURESSchuyler, Friedrich and Vaeghan in 1935 observed the disturbances in occlusal relationship and opening of the bite of full dentures made of acrylic resin, even when the flask was completely closed during processing. Osborne and Taylor in 1941 have noted the disturbance and attributed it to over packing and the accompanying displacement of teeth in the mold.

It was felt, however, that these changes were caused in part by the volumetric change of acrylic resin during polymerization. SELECTIVE GRINDINGExtra oral corrections

Recognizing pre mature contact (Dark ring with a light centre)

Grind until multiple, uniform distributed & even contacts.Intra oral corrections

Using articulating papers.

Central bearing devices. correlator coble deviceAbrasive paste.Extra-oral selective grinding is more preferable than intra-oral selective grinding for the following reasons:

1) Presence of compressible tissue under the denture, that may move with the denture especially in flabby ridge and very resorbed ridges, while in extra-oral selective grinding the dentures are on hard bases (casts).

The bad psychological impact on the patient as he will see his teeth ground in front of him in intra-oral selective grinding.

3) Lateral excursion (right and left) and protrusive movements are difficult.

SELECTIVE GRINDING RULESAvoid grinding functional cusps. (BULL Rule)

Grind opposing fossae or marginal ridge.

Centric holding cusp reduced when it interferes with another centric holding cusp Can be reduced if it causes interferences in centric & eccentric position.

Elimination of protrusive interferences along a path of 3-5mm

Working side interferences are eliminated until canines meet edge to edge or upto distance of 3-4mm.

OBJECTIVES OF CORRECTING OCCLUSAL DISHARMONY The objectives as stated by Schuyler in 1935 are,

1)Maximum distribution of stress in centric maxillo-mandibular relation.

2)Retention of the maxillo-mandibular opening.

3)Harmony of guiding inclines, which distributes eccentric occlusal stresses.

4) Reduction of the incline of guiding tooth surfaces, that occlusal stresses may be more favorably applied to the supporting tissues.

5) Retention of sharpness of cutting cusps.

6) Increase in food exits.

7) Decrease in contact surfaces.CORRECTION OF OCCLUSAL ERRORSLaboratory remounting

Clinical remounting

Direct intraoral correctionLABORATORY REMOUNTING

DisadvantagesCannot correct errors made while recording jaw relationsCannot correct errors made while mounting the casts on the articulatorDoes not compensate changes caused by settling of the denture bases

Made in laboratory after processing and before the denture is inserted in mouth. The aim is to regain the original OVD that was disturbed by processingIt is believed that adjusting the balanced occlusion is not necessary at this stage (immediately after processing and before insertion in mouth) because of settling of denture bases that occur after insertion. Settling changes the occlusal relationship; so it is wiser to wait for settling to occur before adjusting the balanced occlusion. 27CLINICAL REMOUNTING WITH NEW INTEROCCLUSAL RECORDS AdvantagesCorrect errors made during recording of jaw relations, or while mounting cast on articulatorLess chair side time Corrections away from the patients viewNo saliva which makes detection by articulating paper difficultNo shifting of dentures or incorrect closure by pt*the dentures are remounted on to an articulator from new interocclusal records made in patients mouth. Corrections are done by selective grinding on articulator.28THE AIM OF CLINICAL REMOUNTING The prematurities are ground until multiple, uniformly distributed and even contacts are obtained bilaterally Clinical remounting is currently the most commonly preferred method of occlusal correctionClinical Remounting Procedure

Ask patient to bite on cotton rolls for 10 min.Guide mandible into CR several times.Bite registration material is placed on the post. teeth of the mandibular denture

Clinical Remounting Procedure

Guide mandible into CR

Obtain interocclusal record of CR.Clinical Remounting Procedure

Mount upper denture using remounting jig

Mount lower dentureClinical Remounting Procedure

METHODS OF DETECTING OCCLUSAL ERRORS

OCCLUSAL INDICATORSQualitative IndicatorsArticulating paperArticulating silkArticulating filmMetallic shim-stock filmHigh spot indicatorOcclusion spraysWax templateQuantitative indicatorsT Scan occlusal analysis systemARTICULATING PAPER

It is a paper impregnated with blue dye

It is placed bilaterally and teeth are tapped together

High points will show a dark staining or a dough nut shape blue circles

High points are trimmed with carborumdum stone, till all contacts show an equal distribution of force.

Articulating paper

Micronised colour pigmentsWax oil emulsion

Articulating Silk8 microns thickUniversally applicable

Articulating Film Articulating Film

Form a thin biocompatible filmTo check the occlusion& approximal contacts when checking the trial fit of crowns.

Occlusion spraysWAX TEMPLATEA softened wax is place between both dentures, areas of heavy contact will show thinning of wax or even a hole.

TimeMagnitudeDistribution of occlusal contacts

T ScanIndicationsComplete denturesFixed or removable denturesComplete arch reconstruction involving implantsComplete arch reconstruction involving FPDNatural tooth occlusal equilibrationDisclusion time reductionOcclusal splintsMandibular repositioning devicesT ScanRecording technique

T ScanForce

T Scan

The force trajectory shows the premature contact significant on the particular sides & occlusal correction can be carried on the required side.

T Scan

leftrightHow to do a selective grindingLock the articulator condyles to allow for hinge movement only.

Use a blue articulating paper to mark teeth with high contacts in centric relation.

Loosen the condyles allow for eccentric movemnts.

Use a red articulating paper to mark teeth with high contacts at eccentric movements.

High points are evaluated and centric prematurities are removedt.

How to Recognize Premature Contacts?A dark ring with a light center usually denotes a premature contact.

You should distinguish between marks made by normal occlusal contacts and those of premature contacts.

Articulating paper should not be reused many times and should be changed often.

Selective Spot GrindingMake grinding until even (same intensity), stable, and multiple marks spread over wide area in both sides

OCCLUSAL ERRORS & THEIR SELECTIVE GRINDINGA)Centric position errors:1) Pair of opposing teeth hold other teeth out of contact:- deepen the fossae corresponding to cusps till other teeth came in contact.2) UPPER & LOWER TEETH ARE NEARLY END TO END:- grind the inner inclines of upper buccal & lower lingual cusps.- grind lingual of upper lingual cusps.- grind buccal of lower buccal cusps.

3) Upper teeth are far buccal to lower ones:- grind the inner inclines of upper lingual cusps & lower buccal cusps.

B) WORKING SIDE ERRORS:1) Both upper buccal & lower lingual cusps are long:- grind the high cusp tips of non functional2) Buccal cusps make contact but lingual dont:- grind the buccal cusp tips & alter their inclines (in)non functional cusps).

3) Lingual Cusps Make Contact But Buccal Dont:- grind lingual cusps & alter their inclines (of non functional cusp only).

4) Upper Buccal & / Or Lingual Cusps Are Mesial To Intercuspation Position:- reduce upper mesial inclines & lower distal inclines

5) UPPER BUCCAL & / OR LINGUAL CUSPS ARE DISTAL TO INTERCUSPATION POSITION:- reduce upper distal inclines & lower mesial inclines

6) teeth on working side are out of contact:-selective grinding to balancing side

C) BALANCING SIDE ERRORS:1) Balancing side show heavy contact, and working side show no contact:- grind the inner incline of lower buccal cusp.2) No contact on balancing side:- grind the buccal upper cusps on lower lingual cusps of cusps on working side.

D) PROTRUSIVE POSITION ERRORS:1) Anterior teeth show heavy contacts with no posterior contact:- reduce palatal surface of upper anteriors & labial surface of lower anteriors.

2) Posteriors show heavy contact with no anterior contact:- grind distal inclines of upper cusps & mesial inclines of lower cusps.

Note:-You have to wipe markings every time to ensure good localization of abnormal contacts.- after finishing selective grinding, teeth are milled (polished) with pumice.

Direct Intraoral CorrectionDisadvantagesRequires a lot of patient cooperation.Patient should have good neuromuscular control.Saliva.Inaccurate closure by patient.Misleading due to resiliency of tissues and shifting of denture bases.

OCCLUSAL ADJUSTMENTSAdjustment of occlusion can be done by-

Selective reshaping of ridges of cusps.Changes can be made at angles of marginal ridge.Reduction of cusp height can be done.Reduction of sulcus by reducing angles of triangular and oblique ridges.

While reduction do not create flat areas, always maintain rounded contours polished surface of cusps and ridges.All eccentric interferences should be removed first then only centric relation interferences should be removed.Occlusal contouring diamond instrument #8833, maximum speed 120,000 R.P.M.Football shaped diamond instrument 8868-023, maximum speed 80,000 R.P.M.Dura white stones, nmbers 1C2, 1C4, FL1, KN3.Enamel adjustment kit.SUMMARY AND CONCLUSION Selective grinding in complete denture Prosthodontics is an important laboratory procedure which is carried out by remounting of the dentures after processing is completed.

This remounting may either be laboratory remount or patient remount. In spite of carrying out each step in denture construction very carefully, it is seen that in the end when the dentures are remounted there is an occlusal pre maturities or interferences and selective grinding may be needed.REFERENCESBoucher's Prosthodontics Treatment for Edentulous Patients. Twelfth Edition.Chapter 20.

Dalhousie continual education

Complete Denture Prosthodontics, 1st Edition, 2006 by John Joy Manappallil, Chapter 19

Essentials of complete denture prosthodontics,2nd edition , Sheldon Winkler.

Textbook of complete dentures, Charles .M. Heartwell.

INDIAN DENTAL ACADEMY: SELECTIVE GRINDING IN COMPLETE DENTURE , Aug 12,2013.

Acta Stomatol Croat, Vol. 35, br. 3, 2001.

Selective grinding in dental occllusion [Rev Belge Med Dent (1984). 1990] - PubMed NCBI.

Dental equilibration by selective grinding [Av Odontoestomatol. 1989] - PubMed NCBI.

CONCEPTS OF ARRANGEMENT OF ARTIFICAL TEETH, SELECTIVE GRINDING AND BALANCED OCCLUSION IN COMPLETE DENTURE PROSTHODONTICS, NUJHS Vol. 2, No.1, March 2012 ISSN 2249-7110 .

Occlusal adjustment by selective grinding and use of an anterior De programmer,Tetsuo Saito* (Quintessence Int 1990;21:887-892.)