Porcelain Inlay and Onlay| Properties, Preparation and Restoration | PPT
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Porcelain Inlay and Onlay
Restorative Options – Direct
Posteriors: amalgam (material specific), composite (lesion specific)
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.
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.
Restorative Options – Indirect
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????
What cavity preparation features do we need to modify?
Bulk – more occlusal clearance
Reinforcement – bonding
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.
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.
Empress Procelain System
All procelain restoration used for inlay, onlay, full crown
Adequate marginal fit
Better wear characteristic than conventional procelain
Similar to cast gold inlay/onlay in terms of cavity preparation design
Porcelain Fused to Metal Crown vs Empress: Similarities
Brittle – reinforced through the bonding process
Composite vs Empress: Similarities
Mode of retention – dentinal bonding agent
Apply skills you learn for composite on the bonding process.
Summary of Characteristics
Acceptable marginal fit
Conservation of tooth structure
Less occlusal wear
Highly technique sensitive
High esthetic demand
Replace moderate to large existing restoration
Moderate to large primary caries
Unable to adequately isolate the field
Parafunctional habits – bruxing, clenching, excessive wear
Empress vs Gold Inlay/Onlay
Conservation of tooth structure (gold onlay vs porcelain inlay)
Less complicated cavity design??
Technique sensitive – bonding process
Abrasive to occluding dentition
Empress vs PFM
Conservative cavity preparation
Foundation restoration may not be necessary
Less abrasive to occluding dentition
No metal collar
Cavity Preparation Design
1. Occlusal Depth/Cusp Reduction
Occlusal Depth = 1.5 to 2.0 mm
Cusp Reduction:Functional cusp = 1.5-2.0mm
Nonfunction cusp = 1.5 mm
2. Internal/External Line Angles
Degree of draw = approximately 12 to 15 degree
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