1Indirect Cast gold inlay & Onlay restorations 12/3/2015Indirect Cast gold inlay & Onlay restorationsDr. Gaurav Garg ( M.D.S.)Lecturer, College of DentistryAl Zulfi, Majmaah University
2Learning objectives At the end of the lecture students should know: Indirect restorations & their typesIndications, contraindications, advantages & disadvantages of indirect restorationsMaterials used for indirect restorations & clinical proceduresTooth preparation for cast gold inlay & onlay restorations
3IntroductionAn indirect restoration is any restoration that is fabricated extraorally and then cemented into/onto the tooth.
4Types:Intracoronal restorations that fit within the contours of a tooth (e.g. inlays, Onlays, cast intra-radicular posts)Extra-coronal restorations that cover the outer surface of a tooth to recreate the anatomic contours (e.g. full or partial coverage crowns, veneers)InlayOnlayCrown
5InlayInlay involves the occlusal (Class I) or occlusal and proximal (Class II) surfaces of a posterior tooth and may cap one or more, but not all of the cusps.
6OnlayOnlay involves the proximal surfaces (class II) of a posterior tooth, and caps all of the cusps.
7Indications Large Restorations Endodontically Treated Teeth Teeth at Risk for FractureDiastema Closure and Occlusal Plane CorrectionRemovable Prosthodontic Abutment
8Contraindications High Caries Rate Young Patients Esthetics Small Restorations
9advantages High compressive & tensile strength Biocompatibility Low WearControl of Contours and Contacts
10Disadvantages Multiple appointments and higher Chairside Time Costly Technique sensitiveSplitting Forces:Small inlays may produce a wedging effect on facial and/or lingual tooth structure, and thereby increase the potential for splitting the tooth
11MaterialsTraditional high-gold alloys- Most suitable for inlay & onlay (Costly-minimum total gold- plus-platinum content of 75% by weight)Low-gold alloysPalladium-silver alloysBase metal alloys ( Nickel chromium , Cobalt chromium, Cheaper)- Decreased tarnish resistance, decreased burnishability & higher incidence of allergy
12Clinical proceduresEvaluation of the occlusal contacts of the teeth in centric & eccentric movementsLocal Anaesthesia & isolationTooth preparationImpression makingTemporizationTry in & occlusal adjustmentsCementation of the restoration
14Factors influencing the design of the cavity Length of the clinical crownAnatomic contours of the occlusal, Proximal, buccal and lingual surfacesPosition of tooth in the archOcclusal and proximal relationsUnusual esthetic conditions, if anyCondition of soft tissues around the toothExtent and location of carious lesions.
15INLAYOutline formInclude carious lesion and all faulty pits and fissures & cavosurface margin is to be established on sound enamelThe depth of the cavity is maintained at mm from the central grooveConsider EnameloplastyBuccolingual width of cavity- 1/3rd of Intercuspal distanceGingivally there should be a clearence of 0.5 mm from adjacent toothBurs for inlay/onlay preparation
18Retention form Primary retention: Occlusal dovetail Parallelism of buccal & lingual walls: Occlusal divergence of 2º-3º. The divergence can be increased up to 6º in case the depth of cavity is moreSecondary retention:Proximal sliceSlotsShallow retentive grooves, 0.3 mm deep (0.2 mm inside DEJ), may be given in the bucco-axial and linguo-axial line angles
19Factors affecting retention Magnitude of dislodging forcesGeometry of the tooth preparation:Taper : Decreased retention if taper is increasedAxial Depth: deep preparation provide more retentionSurface area: Retention increases with increase in surface area of preparationRoughness of the surfaces being cementedMaterials being cemented: The more reactive the alloy is, the more will be adhesion with the luting cement. Therefore, base metal alloys are better retained than less reactive high gold alloysType of luting agent: Adhesive resin cements provide higher retention than other cements.
20Resistance form Flat pulpal and gingival floors Rounded Axiopulpal line angleRemoval of unsupported enamelPreserve cuspal strengthCavosurface bevel- 40º- it creates obtuse angled marginal tooth structure, which is bulkiest and strongest. Such type of marginal tooth structure produce an acute angled (30º- 40º) marginal cast alloy, which can be easily burnishedPrimary & Secondary flares
21BevelTypes:a. Partial bevel: It involves part of the enamel wall. Given in direct composite restorationsb. Short bevel: It involves the entire enamel wall. This type of preparation is best suited in cast gold restorations.c. Inverted bevel: It is given on the labial shoulder of metal ceramic crowns to effectively improve the esthetics at the margins.d. Reverse Bevel: A reverse bevel is placed at the dentinal portion of the gingival floor towards the axio- gingival line angle.The hydrostatic pressure during cementing a cast restoration can produce a rotational displacement of the castings with flat gingival walls.This effect is resisted by the reverse bevel resulting in even seating of the cast restoration.(d)
23Flares A. Primary Flare: It involves divergence of the buccal and lingual proximal walls at an angle of 45ºIt bring the buccal and lingual proximal margins of the cavity preparation in the embrasures enabling easy cleaning and finishingB. Secondary flares:Beveling the cavosurface wall peripheral to the primary flare.The direction of the secondary flare results in 40º marginal metal, which is burnishable and produces good adaptation to the cavity margin.In certain cases where the contact is broad and wide, the secondary flares become mandatory to bring the proximal walls in self-cleansing embrasures.BA
28References & Suggested reading Sturdevant's art & science of operative dentistry Theodore M. Roberson, Harald O. Heymann, Edward J. Swift, Jr.Principles of operative dentistry (2005)- A.J.E. Qualtrough, J.D. Satterthwaite, L.A. Morrow and P.A. Brunton.Fundamentals of Operative Dentistry- 2nd Edition- Summitt & Robbins