In vitro precision of fit of computer-aided design and computer-aided manufacturing titanium and zirconium dioxide bars

Objectives. Optical scanners combined with computer-aided design and computer-aided manufacturing (CAD/CAM) technology provide high accuracy in the fabrication of titanium (TIT) and zirconium dioxide (ZrO) bars. The aim of this study was to compare the precision of fit of CAD/CAM TIT bars produced with a photogrammetric and a laser scanner. Methods. Twenty rigid CAD/CAM bars were fabricated on one single edentulous master cast with 6 implants in the positions of the second premolars, canines and central incisors. A photogrammetric scanner (P) provided digitized data for TIT-P (n = 5) while a laser scanner (L) was used for TIT-L (n = 5). The control groups consisted of soldered gold bars (gold, n = 5) and ZrO-P with similar bar design. Median vertical distance between implant and bar platforms from non-tightened implants (one-screw test) was calculated from mesial, buccal and distal scanning electron microscope measurements. Results. Vertical microgaps were not significantly different between TIT-P (median 16 μm; 95% CI 10-27 μm) and TIT-L (25 μm; 13-32 μm). Gold (49 μm; 12-69 μm) had higher values than TIT-P (p = 0.001) and TIT-L (p = 0.008), while ZrO-P (35 μm; 17-55 μm) exhibited higher values than TIT-P (p = 0.023). Misfit values increased in all groups from implant position 23 (3 units) to 15 (10 units), while in gold and TIT-P values decreased from implant 11 toward the most distal implant 15. Significance. CAD/CAM titanium bars showed high precision of fit using photogrammetric and laser scanners. In comparison, the misfit of ZrO bars (CAM/CAM, photogrammetric scanner) and soldered gold bars was statistically higher but values were clinically acceptable.