Indirect Cast gold inlay & Onlay restorations 12/3/2015 Indirect Cast gold inlay & Onlay restorations Dr. Gaurav Garg ( M.D.S.) Lecturer, College of Dentistry Al Zulfi, Majmaah University

Learning objectives At the end of the lecture students should know: Indirect restorations & their types Indications, contraindications, advantages & disadvantages of indirect restorations Materials used for indirect restorations & clinical procedures Tooth preparation for cast gold inlay & onlay restorations

Introduction An indirect restoration is any restoration that is fabricated extraorally and then cemented into/onto the tooth.

Types: 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) Inlay Onlay Crown

Inlay Inlay 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.

Onlay Onlay involves the proximal surfaces (class II) of a posterior tooth, and caps all of the cusps.

Indications Large Restorations Endodontically Treated Teeth Teeth at Risk for Fracture Diastema Closure and Occlusal Plane Correction Removable Prosthodontic Abutment

Contraindications High Caries Rate Young Patients Esthetics Small Restorations

advantages High compressive & tensile strength Biocompatibility Low Wear Control of Contours and Contacts

Disadvantages Multiple appointments and higher Chairside Time Costly Technique sensitive Splitting Forces: Small inlays may produce a wedging effect on facial and/or lingual tooth structure, and thereby increase the potential for splitting the tooth

Materials Traditional high-gold alloys- Most suitable for inlay & onlay (Costly-minimum total gold- plus-platinum content of 75% by weight) Low-gold alloys Palladium-silver alloys Base metal alloys ( Nickel chromium , Cobalt chromium, Cheaper)- Decreased tarnish resistance, decreased burnishability & higher incidence of allergy

Clinical procedures Evaluation of the occlusal contacts of the teeth in centric & eccentric movements Local Anaesthesia & isolation Tooth preparation Impression making Temporization Try in & occlusal adjustments Cementation of the restoration

Tooth preparation for inlay & onlay

Factors influencing the design of the cavity Length of the clinical crown Anatomic contours of the occlusal, Proximal, buccal and lingual surfaces Position of tooth in the arch Occlusal and proximal relations Unusual esthetic conditions, if any Condition of soft tissues around the tooth Extent and location of carious lesions.

INLAY Outline form Include carious lesion and all faulty pits and fissures & cavosurface margin is to be established on sound enamel The depth of the cavity is maintained at 1.75 - 2.0 mm from the central groove Consider Enameloplasty Buccolingual width of cavity- 1/3rd of Intercuspal distance Gingivally there should be a clearence of 0.5 mm from adjacent tooth Burs for inlay/onlay preparation

Retention 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 more Secondary retention: Proximal slice Slots Shallow retentive grooves, 0.3 mm deep (0.2 mm inside DEJ), may be given in the bucco-axial and linguo-axial line angles

Factors affecting retention Magnitude of dislodging forces Geometry of the tooth preparation: Taper : Decreased retention if taper is increased Axial Depth: deep preparation provide more retention Surface area: Retention increases with increase in surface area of preparation Roughness of the surfaces being cemented Materials 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 alloys Type of luting agent: Adhesive resin cements provide higher retention than other cements.

Resistance form Flat pulpal and gingival floors Rounded Axiopulpal line angle Removal of unsupported enamel Preserve cuspal strength Cavosurface 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 burnished Primary & Secondary flares

Bevel Types: a. Partial bevel: It involves part of the enamel wall. Given in direct composite restorations b. 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)

No.8862 bur

Flares A. Primary Flare: It involves divergence of the buccal and lingual proximal walls at an angle of 45º It bring the buccal and lingual proximal margins of the cavity preparation in the embrasures enabling easy cleaning and finishing B. 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. B A

ONLAY Cuspal/occlusal reduction: 1.5 mm on functional cusp 1 mm on non functional cusp Chamfer/Shoulder margin

References & Suggested reading Sturdevant's art & science of operative dentistry-2006- 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

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