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INLAY VS AMALGAM

INLAY VS AMALGAM. DEFINITION OF INLAY. Inlay is defined as a fixed intracoronal restoration, a dental restoration made outside of a tooth to correspond to the form of prepared cavity, which is then luted into the tooth (Rosensteil). Indications.

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INLAY VS AMALGAM

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  1. INLAY VS AMALGAM

  2. DEFINITION OF INLAY • Inlay is defined as a fixed intracoronal restoration, a dental restoration made outside of a tooth to correspond to the form of prepared cavity, which is then luted into the tooth (Rosensteil)

  3. Indications • It is an alternative to amalgam and composite when higher strength and superior control of contours & contacts is desired. • Used instead of amalgam in patients with low caries rate who require small class II with ample supporting dentin

  4. Advantages • Strength • Biocompatibility • Low wear • Control of contours & contacts

  5. Disadvantages • Higher chair side time & increased appointments • Temporary required between preparation & delivery appointments • Cost factor • Technique sensitive • Splitting forces

  6. Basic concepts of cavity design for cast restoration

  7. Basic concepts of cavity design for cast restoration • Preparation path • Inlay taper • Preparation features of circumferential tie • Occlusal & gingivalBevels • Facial & lingual Flares • Primary • Secondary

  8. Preparation path • Single insertion path • All reductions oriented towards one path • The “line of draw” – path of removal & re-insertion should be perpendicular to plane across cusp tips or parallel to long axis of tooth crown

  9. Inlay taper • Apico-occlusal taper • Cavity walls must diverge from floor outwards • To permit unobstructed removal & placement of wax pattern & casting • Developed by preparing occlusal walls so that they form obtuse angle with pulpal floor

  10. According to Sturdevant : • 2 ° – 5 ° from line of draw • Short vertical walls : 2 ° • Long vertical walls : > 2 ° • According to Charbeneau: • 10 ° – 16 ° of convergent angle • 5 ° – 8 ° on each wall • According to Marzouk: • 2 ° – 5 ° from path of preparation

  11. Taper may be increased or decreased according to followingfactors : • Wall lengthTaper required (< 10°) • Surface involvementin preparation Taper required (< 10°) • Need for retentiontaper

  12. PREPARATION FEATURES OF CIRCUMFERENTIAL TIE • Circumferential tie – peripheral marginal anatomy • Features : • In an intracoronal cavity, the circumferential tie is in the form of a bevel, which is a plane of a cavity wall or floor directed away from cavity preparation • Occlusal & gingivalBevels • Types • Functions • Facial & lingual Flares • Primary • Secondary

  13. BEVELS • “Flexible extentions” of a cavity preparation, allowing the inclusion of surface defects, supplementary grooves, or other areas on tooth surface. • To provide “lap joint” • Establishes closure at the interface of gold & enamel or cementum

  14. Types & design features of occlusal & gingival bevels • According to their shapes & types of tissue involvement there are 6 types of bevels : • Partial bevel • Short bevel • Long bevel • Full bevel • Counter bevel • Hollow ground (concave) bevel

  15. Partial bevel • Involves : part of enamel wall ; not exceeding 2/3 of its dimension • Use : to trim weak enamel rods from margin peripheries

  16. Short bevel • Involves : entire enamel wall ; but not dentin • Use : mostly with Class I alloys specially type 1 & 2

  17. Long bevel • Involves : all enamel wall & up to ½ of dentinal wall • Use : most frequently used for Class I,II & III alloys • Advantage : preserves internal “boxed-up” resistance & retention features of the preparation

  18. Full bevel • Involves : all the dentinal & enamel walls of cavity wall or floor • Use : only if impossible to use other bevels • Disadvantage : deprives the preparation of its internal resistance & retention features

  19. Counter bevel • Use : when capping cusps ; to protect & support them • Used opposite to an axial cavity wall on facial or lingual surface of tooth • It will have gingival inclination facially & lingually

  20. Hollow ground (concave) bevel • Any bevel prepared in concave form • Allows space for cast material bulk ; improves retention & resistance • Ideal for Class IV & V cast materials

  21. Function of Bevels • Satisfies Noy’s requirements • Creates obtuse angled marginal tooth structure strongest configuration of marginal anatomy • Creates acute angledmarginal cast alloy most amenable to burnishing

  22. Function of Bevels • Reduces error factors (space between cast & tooth substance) • Bevel – major retention form ; here direct retentive frictional component exists between casting & tooth

  23. A bevel allows closer approximation of a crown margin to tooth In presence of bevel, distance from margin to tooth is less than D & is function of sine of acute angle of margin (m) or cosine of obtuse angle of finish line (p)

  24. Impacts striking enamel next to a bevel can be withstood without damage (left) Where there is no bevel, unprotected enamel rods near the restoration can be more easily fractured (right)

  25. Types & design features of facial & lingual flares • Flares – flat or concave peripheral portions of facial & lingual walls • 2 types : • Primary flare • Secondary flare

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