40
Strengthening porcelain
Figure 40.1 Reinforcing filler particle acting as a “crack stopper” for a propagating crack.
Figure 40.2 Schematic representation of a PFM (metallo-ceramic) crown.
Figure 40.3 Schematic representation of a crown constructed with a glass-infiltrated (In-Ceram) core.
Table 40.1 Strengths of dental hard tissues and dental ceramics
| Material | Flexural strength (MPa) | Fracture toughness (MN/m3/2) |
|---|---|---|
| Enamel | 65–75 | 1 |
| Dentin | 16–20 | 2.5 |
| Feldspathic porcelain | 60–110 | 1.1 |
| Leucite porcelain | 120–180 | 1.3 |
| Aluminous porcelain | 130–140 | 2.0 |
| Glass-infiltrated alumina | 400–600 | 4–6 |
| Spinel-infiltrated alumina | 325–410 | 2.4 |
Porcelain restorations can be fabricated in a range of shades and translucencies that, with esthetics and chemical resistance, make them almost ideal replacements for lost hard tissue. Further, being a good thermal insulator, porcelain protects the pulp against heat insult even with marked hard tissue loss.
Limitations of porcelain were indicated in Chapter 39. Despite improvements that are possible by control/>
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