1. Porcelain Inlay and Onlay
Preparation and Restoration
Dr. Ignatius Lee

2. Restorative Options - Direct
Posteriors: amalgam
Anteriors: composite
2000’s
Posteriors: amalgam (material specific), composite (lesion specific)
Anteriors: composite

3. Evolution of Cavity Preparation Design for Posterior Composite
Taking into consideration the differences in the physical properties between the two materials (amalgam vs composite); and based on the rationale of the cavity preparation design for amalgam
Questions were asked: Do we need convergent walls? retention grooves? Worry about unsupported enamel? Extension for prevention? Do we need bulk?
New cavity preparation design for posterior composite was created; it was based on specific characteristic of the material.

4. Why are we talking about amalgam/composite
Example of utilizing the skill/knowledge we acquired in using a specific material/procedure (amalgam restoration) and applying it on a new material/procedure (composite restoration)
Preparation skills should be easily transferable.
Knowledge on the rationale of cavity preparation will allow us to adapt to the new material based on the material’s specific characteristic.
Answer to your question on “why are we still teaching cast gold inlay/onlay”? - when only a few dentists are doing these kinds of procedures in their offices.

5. Restorative Options - Indirect
Cast gold inlay/onlay, 3/4 crown, full cast crown, PFM
2000’s
Cast gold inlay/onlay, 3/4 crown, full cast crown, PFM
Porcelain/composite inlay/onlay

6. Differences between gold and porcelain restorations
Physical properties - porcelain more brittle
Mode of retention - bonding vs mechanical retention
Concept of margin
Based on these differences, can we design a cavity preparation for using porcelain intra-coronally??
Starting with cavity preparation design for cast gold inlay/onlay, what features do we have to modify for porcelain????

7. Physical Properties
What cavity preparation features do we need to modify?
Bulk - more occlusal clearance
Reinforcement - bonding
Bevels contraindicated

8. Mode of Retention
Cast gold preparation rely on 6 to 7 degree of divergent walls and sharp internal line angles.
Porcelain rely on the bonding process, no need for 6 to 7 degree divergent wall and sharp internal line anlges.

9. Marginal Adaptation
Cast gold - rely on close adaptation (20u); lack of adhesion between tooth structure/cement/gold interface
Porcelain - rely on the adhesion between tooth structure/resin cement/procelain to create a gap free continuous margin.
No gingival bevels needed to minimize the gap.

10. Empress Procelain System
All procelain restoration used for inlay, onlay, full crown
Castable
Adequate marginal fit
Better wear characteristic than conventional procelain
Similar to cast gold inlay/onlay in terms of cavity preparation design

11. Porcelain Fused to Metal Crown vs Empress: Similarities
Highly esthetic
Wear
Brittle - reinforced through the bonding process

12. Composite vs Empress: Similarities
Mode of retention - dentinal bonding agent
Apply skills you learn for composite on the bonding process.

13. Mechanism of Adhesion
Porcelain etched with hydrofluoric acid (micromechanical)
Bond between etched tooth and DBA - identical to composite/tooth
Silane coupling agent - chemical bond

14. Summary of Characteristics
Highly esthetic
Acceptable marginal fit
Conservation of tooth structure
Less occlusal wear
Highly technique sensitive

15. Indications High esthetic demand
Replace moderate to large existing restoration
Fractured tooth/restoration
Moderate to large primary caries
Contraindiations
Unable to adequately isolate the field
Parafunctional habits - bruxing, clenching, excessive wear

16. Empress vs Gold Inlay/Onlay Empress
Advantages
ESTHETIC
Conservation of tooth structure (gold onlay vs porcelain inlay)
Less complicated cavity design??
Disadvantages
Expensive
Technique sensitive - bonding process
Abrasive to occluding dentition

17. Empress vs PFM Empress Advantages Conservative cavity preparation
Foundation restoration may not be necessary
Less abrasive to occluding dentition
No metal collar
Disadvantages
Expensive
Technique sensitive

18. Cavity Preparation Design
1. Occlusal Depth/Cusp Reduction
Occlusal Depth = 1.5 to 2.0 mm
Cusp Reduction:Functional cusp = mm
Nonfunction cusp = 1.5 mm
2. Internal/External Line Angles
Rounded

19. Cavity Preparation Design
3. Draw
Degree of draw = approximately 12 to 15 degree
4. Bevel
No bevel

20. Mn first premolar- DO amalgam with fractured lingual cusp, deep pulpal floor
Existing amalgam removed, making all walls divergent, smoothed all cavosurface margins

21. Mx first molar - MOD amalgam with deep pulpal floor (4mm)
Existing amalgam removed

22. Proximal walls and gingival seats extended, occlusal wall divergent, clinical judgement was made to cover DL cusp (with shoulder)
No cavosurface bevel on shoulder

23. MOB amalgam on Mx first molar with deep pulpal floor
Existing amalgam removed, make all walls divergent and smoothed all cavosurface margins

24. Occl amalgam on Mn first molar, normal pulpal depth; patient complaining about pain on function- Dx: DB cusp fractured
Patient’s occlusion

25. Existing amalgam removed, DB cusp reduced by 2mm, all walls divergent
No shoulder on DB cusp - WHY???

26. MOD amalgam on Mn second molar with fractured Li cusp
MOD amalgam on Mn second molar with fractured Li cusp. Normal pulpal depth; all amaglam removed
Proximal box divergent, Li cusp - smoothed cavosurface margin

27. MOD amalgam on Mn first molar - occlusal fractured
Shade selection BEFORE rubber dam; need dentin shade (match shade at gingival third) and overall shade

28. Finished preparation; rubber dam removed; ready for impressioning; proximal box divergent, cusp reduction, buccal cusp with heavy bevel (no shoulder)
Buccal view

29. Wax up on working cast
Special die for shade matching/staining - reason for taking the dentin shade

30. Restoration on die/working cast

31. Trying in under rubber dam; adjust proximal contact; do not adjust occlusal contact

32. Cementation under rubber dam using resin cement; excess cement removed using cotton tip
Excess resin cement removed from proximal/gingival margins using an explorer

33. Rubber dam removed following cementation
Adjust occlusion using fine diamond in high speed hand piece

34. Laboratory Exercise - Mn first molar,
MOD onlay preparation for porcelain

35. Finished Preparation - MOD porcelain onlay preparation

36. Restoration on die, back from laboratory

37. Restoration seated under rubber dam
Bu view after cementation

38. Restoration on die, back from laboratory
Restoration seated under rubber dam