2 Causes of Denture Errors Clinical errorsTechnical errorsInherent deficiencies in the material itself
3 Evaluation Procedures ProcessingPolished surfacesTissue fit and comfortRetention, stability and supportJaw relationsOcclusionEstheticsSpeech
4 Evaluation of Processing * Inspect for processing errors, e.g. porosityInspect for inadequate polishingRun your finger along the borders & impression surface to check if sharp edges or acrylic spicules existExamine frenal notches for sharp edgesExamine for adhered plaster or stone fragmentsIt is imperative that clinician examine the denture thoroughly before insertingCorrections are made by scraping or grinding with knife, sandpaper, or stone burs
5 Patient Education & Preparation * First oral feeling with fullness is normal & will disappear over timeExcessive salivation(compulsive spitting or rinsing should be avoided, instead swallowing encouraged to remove excess saliva)The pt should be aware that only after the dentist has completed evaluation and adjustment of denture in the mouth and is satisfied with it, will the pt be allowed to view it.
6 Evaluation of Tissue Fit & Comfort Pressure Indicating Paste (PIP)*Every new denture must be checked with PIP to identify and determine if pressure areas exist to reduce them.Commercial preparations are available. PIP can be prepared in clinic by mixing zinc oxide eugenol base paste with Vaseline. Light body elastomeric impression paste can also be used as PIP
7 Evaluation of Tissue Fit & Comfort Never adjust unless you can see exactly where to adjustUse indicator medium(PIP, indelible marker, etc)
9 How to Read PIP? Streaks - no contact (N) No Paste - Impingement (I) Paste, no streaks - normal contact (C)
10 Evaluation of Tissue Fit & Comfort Severe undercutsCause abrasion and soreness in seating and removalManagementRelieve with extreme caution with aid of PIP
11 Evaluation of Tissue Fit & Comfort Overextended bordersDenture appears to rise or has inadequate retentionManagementIdentify the offending borders, mark with indelible marker inside the pt mouth and carefully reduce
12 Evaluation of Retention, Stability & Support Test for retention*Test for posterior palatal sealThe finger is placed on the ridge and a rolling pressure is applied away from the side being checked. The denture should resist dislodgment.Posterior palatal seal is checked by applying pressure in anterior region
13 Test for RockingApply alternating finger pressure on occlusal surfaces of R & L sidesRocking around fulcrum pointMidpalatal raphe is a common fulcrum point if inadequate relief has been provided ** The fulcrum point must be identified and relieved with the aid of PIP.
14 Evaluation of Occlusion Denture processing almost always causes changes in occlusion due to dimensional changes in resinThese changes are usually manifested as increase in OVD
15 Causes of Occlusal Errors Errors in impressionsIll-fitting trial denture basesInaccurate jaw relation recordsErrors during transfer of the records to articulatorIncorrect arrangement of posterior teethDimensional changes during curingProcessing faults……..**Failure to close flask completely, too much pressure while closing the flask, tooth movement during flasking or packing, failure to cool flask before deflasking, distortion due to improper flasking, warpage due to overheating during polishing
16 Why is it difficult to detect occlusal errors in the mouth? * Negative attitude (assume an error exists and try to find it)*shifting of denture bases, incorrect closure by pt.
17 What is the ideal occlusal contact? At first contact, even maximum intercuspation at CR without denture shifting or instability & without pain **sliding of denture bases or uneven pressure caused by faulty occlusion can lead to ulceration of mucosa.
18 Types of Occlusal Errors CO not coincide with CRPremature contact (high point) in one or both sidesUneven distribution of occlusal contactsEccentric movement prematurities (protrusive & lateral)
19 What are the Methods of Detecting Occlusal Errors? Touch & slide method (Refer to lecture 9)Denture dislodges or shifts when pt occludesPt complains of pain beneath denture bases*
20 Correction of Occlusal Errors Laboratory remountingClinical remountingDirect intraoral correction
21 Laboratory Remounting * Disadvantages Cannot correct errors made while recording jaw relations Cannot correct errors made while mounting the casts on the articulator Does not compensate changes caused by settling of the denture basesMade 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.
22 Clinical Remounting with New Interocclusal Records * AdvantagesCorrect errors made during recording of jaw relations, or while mounting cast on articulatorLess chair side timeCorrections away from the patient’s 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 patient’s mouth. Corrections are done by selective grinding on articulator.
23 The Aim of Clinical Remounting The prematurities are ground until multiple, uniformly distributed and even contacts are obtained bilaterally
24 Clinical remounting is currently the most commonly preferred method of occlusal correction
25 Clinical 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
26 Clinical Remounting Procedure Guide mandible into CRObtain interocclusal record of CR.
27 Clinical Remounting Procedure Mount upper denture using remounting jigMount lower denture
29 Selective Spot Grinding * *Articulating paper is used to identify the prematurities. Articulating paper should be placed bilaterally. The articulator is raised and closed with sharp repeated tapping motions. The prematurities are identified and reduced with a small conical stone bur or another suitable bur.The art of reducing premature contacting surfaces, so that an equal pressure exists at all points with interference at no point.
30 How to Recognize Premature Contacts? A dark ring with a light center usually denotes a premature contactYou should distinguish betw. marks made by normal occlusal contacts and those of premature contactsArticulating paper should not be reused many times and should be changed often.
31 Selective Spot Grinding Make grinding until even (same intensity), stable, and multiple marks spread over wide area in both sides
32 Eliminating Occlusal Errors Re-establishment of CO.Correction of protrusive relation.Correction of working side occlusal errors.Correction of balancing side errors.Initially, centric occlusion errors are corrected, followed by protrusive, R & L lateral interferences.
33 Basic Tooth Positions Balancing Contacts Centric Occlusion Working Contacts
34 Selective Grinding Rules to Obtain CO After the first few taps on the articulating paper only a few high contacts appear.The marking process and the grinding are repeated until all except the anterior teeth contact in CO.Ideally all holding cusps * of the maxillary and mandibular posterior teeth will make simultaneous contacts.It is not uncommon for one or two functional cusps not to make contact after establishing the final CO.It is not necessary to continue adjusting until these cusps make contacts because aggressive adjustment will sacrifice the established OVDHolding, supporting or functional cusps are the maxillary palatal and mandibular buccal.The balancing non-functional cusps are upper buccal and lower lingual (BULL)
35 Selective Grinding Rules to Obtain CO As far as possible, avoid grinding cusp tips especially centric holding cusps, instead grind the opposing fossae or marginal ridges where the centric holding cusps occludeIf the high contact is on the centric holding cusp inclines, the cuspal inclines can be reduced, thereby gradually moving the contact more toward the bearing cusp tip.A centric holding cusp may be reduced when it interferes with another centric holding cusp or when makes interferences in centric and eccentric positions
36 Re-establishment of CO Problem: Teeth too longSolution: Deepen the fossae
37 Re-establishment of CO Problem: Teeth too nearly end to endSolution: Grind Inclines
38 Re-establishment of CO Problem: Too much horizontal overlapSolution: Broaden central fossae
39 After the CO re-establishment…. DO NOT:Reduce maxillary lingual cusps.Reduce mandibular buccal cusps.Deepen the fossae.
40 Correction of Protrusive Relation The teeth are brought edge to edgeAny interferences to smooth anterior gliding of dentures are eliminated by grindingElimination of protrusive interferences along a path of 3 to 5 mm is sufficient
41 Correction of Working Side Occlusal Errors BULL rulebuccal upper-lingual lower
42 Correction of Working Side Occlusal Errors Reduce lingual inclines of buccal cusps of upper teeth.Reduce buccal inclines of lingual cusps of lower teeth.ON WORKING SIDE ONLY!!!
43 Correction of Working Side Occlusal Errors Problem: Buccal and lingual cusps too long.Solution: Change inclines of balancing cusps.
44 Correction of Working Side Occlusal Errors Problem: Buccal cusps are too longSolution: Change lingual incline of maxillary buccal cusp
45 Correction of Working Side Occlusal Errors Problem: Lingual cusp too long.Solution: Change buccal incline of lingual cusp of mandibular tooth.
46 Correction of Balancing Side Errors On the balancing side, the cusps usually involved are the functional cusps and therefore grinding becomes more confusing
47 Correction of Balancing Side Errors Decide which supporting cusp maintains CO and reduce its opponent.
48 Correction of Balancing Side Errors Grind the lingual incline of the mandibular buccal cusp.
49 Direct Intraoral Correction DisadvantagesRequires a lot of pt cooperationPt should have good neuromuscular controlSalivaInaccurate closure by ptMisleading due to resiliency of tissues and shifting of denture bases
50 ReferencesBoucher's Prosthodontics Treatment for Edentulous Patients. Twelfth Edition.Chapter 20.Dalhousie continual educationComplete Denture Prosthodontics, 1st Edition, 2006 by John Joy Manappallil, Chapter 19