Influence of CAM vs. CAD/CAM scanning methods and finish line of tooth preparation in the vertical misfit of zirconia bridge structures.
OBJECTIVE
To evaluate the influence of CAD/CAM scanning method (wax-up digitization vs. direct scanning of tooth preparation) and finish line type (chamfer vs. shoulder) on the vertical fit of zirconia frameworks for three-unit posterior-lower bridges.


METHODS
30 sets of two stainless steel master dies were prepared with different marginal designs (chamfer and shoulder) around the contour of each abutment. Over these samples, 30 structures for three-unit posterior-lower bridges were made with Cercon Smart Ceramics CAD/CAM system (Dentsply). An optical laser digitized the wax patterns of 15 bridge structures, and 15 pairs of master dies were directly scanned for designing by computer the remaining half of frames. All zirconia milled structures were luted onto the metallic models with a special clamp made-up to maintain constant seating pressure. Vertical discrepancy around the margins was assessed under scanning electron microscopy (SEM). Misfit data was analyzed using two-way ANOVA and Tukey's test for multiple comparisons at a = 0.05.


RESULTS
Vertical discrepancy of the wax-up/digitized bridge structures was significantly higher than that of the computer-designed frameworks (P < 0.0001). No statistically significant differences were found between the chamfer and shoulder vertical misfit values assessed around the metallic models margins (P = 0.55).
Castillo de Oyagüe
Raquel
R
Department of Prosthodontics, Faculty of Dentistry, University Complutense of Madrid, Madrid, Spain.
Sánchez-Jorge
María Isabel
MI
Sánchez Turrión
Andrés
A
Monticelli
Francesca
F
Toledano
Manuel
M
Osorio
Raquel
R
D017076:Computer-Aided Design; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003830:Denture, Partial, Fixed; D006801:Humans; D008334:Mandible; D003765:Models, Dental; D008963:Molar; D010363:Pattern Recognition, Automated / Q000379:methods*; D017755:Prosthesis Fitting; D019231:Tooth Preparation, Prosthodontic / Q000379:methods*; D014716:Vertical Dimension; D014885:Waxes; D015040:Zirconium
D014885:Waxes; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide