*2.2.7 CAD/CAM milling and copy milling*

CAD/CAM milling and copy milling is an important field of dentistry and prosthodontics using CAD/CAM (computer-aided design and computer-aided manufacturing) to improve the design and creation of dental restorations [81, 82]. Thus, leucite-reinforced glass–ceramics involve Authentic and Empress CAD. Both have the identical microstructure and containing feldspathic glass with about 45 wt%. These blocks may characterize utilizing external strains and containing finer leucite crystals (about 5–10 μm in size). Additionally, the strength behavior of Empress CAD was comparable with Vitablocs. During the last two decades, dental CAD/CAM technology has been used to replace the laborious and time consuming, conventional lost wax technique for efficient fabrication of restorations [83]. Hence, this technology enables dentists to produce complex shapes of ceramics.

Typically, CAD/CAM dental restorations are milled from solid blocks of ceramic or composite resin that closely match the basic shade of the restored tooth. Metal alloys including zirconia can also be milled. The software sends this data to a milling machine where the prosthesis was milled [84]. CAD/CAM allows easy production of precise, esthetic, and durable prostheses [85]. CAD/ CAM complements earlier technologies employed for these goals by enhancing

**Figure 8.** *TEM image of the ZrO2 ceramic powder [80].*

### **Figure 9.**

*Photographs of (A) stainless steel abutment, (B) CAD design for a crown specimen, (C) CAD/CAM composite resin crown bonded to the abutment, (D) loading points on the occlusal surface, and (E) the used machine [87].*

the speed of design and creation, making affordable restorations, reducing unit coast, etc. Nevertheless, chair-side CAD/CAM equipment requires more time on the part of the dentists, and the fee was much higher than conventional restorative treatments. During the years 2015–2018, the data of 21 patients undergoing fibula free flap reconstructive surgery with CAD/CAM patient-specific reconstruction plates were analyzed, including the applicability of the virtual plan, flap survival, duration of surgery, ischemia time, simultaneous dental implantation, implant exposure, and postoperative complications [86]. At the time of primary reconstruction, a number of 76 dental implants were inserted in the 21 patients. The results showed that, in the secondary surgery, the implant can be uncovered 38.1% of the total patients in 7.6 months. Thus, the overall success rate for implants was 97.4%. Virtual surgical planning with CAD/CAM plates allows early and functional dental rehabilitation. Okada et al. [87] fabricated composite crowns using four computer aided design/computer aided manufacturing (CAD/CAM) blanks composed of a resins (sample 1) and a lithium disilicate (sample 2), which exhibited distinct tendencies (see **Figure 9**). The results revealed that the flexural strength was in the range of 175 to 247 MPa for sample 1 and 360 MPa for sample 2 while the fracture strength was in the range of 3.3 to 3.9 kN for the sample 1 and 3.3 kN for the sample 2.
