**3. Conclusions**

Any reader of this review, who is well versed in materials science, will be tempted to enter dentistry to introduce newer and better ceramics to dentistry. As one can comprehend, no material is ideal in all aspects, to natural structure of teeth. However, mechanical and biological properties of ceramics have exhibited a significant improvement in the past few decades. Recent surges in all-ceramic crowns for esthetics and durability is a highlight of such improvements. Also, with dentistry, frequently gaining new faces are catered by these ceramic materials. Further scope of research in dental ceramics can be directed to stronger and osseointegrative ceramic implants, more esthetic and strong crowns and veneers, to mention a few. Definitely, future is bound to witness a bigger revolution in field of dental ceramics, with introduction of newer ceramics and nanotechnology for the betterment of dental restorations on the lines of form, function and esthetics, along with improved biocompatibility.

structure are fabricated in this manner. Pressables may be used for inlays, onlays, veneers,

Numerous ceramics have found their way into this system, due to its short processing time. Some of them are described here. **Glass/Crystal ceramics** are made from fine-grain powders, producing pore-free ceramics. This was the first material specifically produced for the CEREC system. It has an excellent history of clinical success for inlays, onlays, and anterior and posterior crowns. These blocks are available as monochromatic, polychromatic with stacked shades as in a layered cake, and in a form replicating the hand-fabricated crowns whereas an enamel porcelain is layered on top of dentin porcelain. **Glass/Leucite** is a feldspathic glass with approximately 45% leucite crystal component. **Lithium disilicate** is not initially fully crystallized, which improves milling time and decreases chipping risk from milling. The milled restoration is then heat-treated for 20 - 30 mins to crystallize the glass and produce the final shade and mechanical properties of the restoration. This crystallization changes the restoration from blue to a tooth shade. The microstructural and chemical composition is essentially the same. **Framework** Alumina are fabricated by pressing the alumina-based powder into a block shape. These blocks are only fired to about 75% density. After milling, these blocks are then infused with a glass in different shades to produce a 100% dense material, which is then veneered with porcelain. **Porous Alumina** frameworks may be fabricated from porous blocks of material. Pressing the alumina powder with a binder into molds produces the blocks. The blocks may be partially sintered to improve resistance to machining damage or used as pressed in a fully "green" state (unfired, with binder). The frameworks are milled from the blocks and then sintered to full density at approximately 1500°C for 4 to 6 hours. The alumina has a fine particle size of about 1µm and strength of approximately 600 MPa and is designed for anterior and posterior single units, as well as anterior three-unit bridges. **Porous Zirconia** frameworks milled from porous blocks are fabricated similarly to alumina blocks. As is the case with the alumina block, the milled zirconia framework shrinks about 25% after a 4 - 6 hours cycle at approximately

Any reader of this review, who is well versed in materials science, will be tempted to enter dentistry to introduce newer and better ceramics to dentistry. As one can comprehend, no material is ideal in all aspects, to natural structure of teeth. However, mechanical and biological properties of ceramics have exhibited a significant improvement in the past few decades. Recent surges in all-ceramic crowns for esthetics and durability is a highlight of such improvements. Also, with dentistry, frequently gaining new faces are catered by these ceramic materials. Further scope of research in dental ceramics can be directed to stronger and osseointegrative ceramic implants, more esthetic and strong crowns and veneers, to mention a few. Definitely, future is bound to witness a bigger revolution in field of dental ceramics, with introduction of newer ceramics and nanotechnology for the betterment of dental restorations on the lines of form, function and esthetics, along with improved

1300°C to 1500°C. The particle size is about 0.1 µm to 0.5 µm.

and single-unit crowns.

3. CAD/CAM

**3. Conclusions** 

biocompatibility.

#### **4. Acknowledgements**


#### **5. References**


**Part 3** 

**Glass Ceramics / Composites** 

