In vitro performance of CAD/CAM and conventional removable dentures

Innovations in CAD/CAM technology and materials science offer new methodologies for removable prosthodontics. As clinical data are still rare, in vitro performance of both CAD/CAM and comparable conventional materials may help to estimate the clinical outcome.

Specimens (n = 8 per group) from teeth (CediTEC, SR VivodentCAD, Vitapan), base materials (V-Print dentbase, IvoBase CAD, Paladur), adhesives (CediTEC Primer/Adhesive, IvoBase CAD Bond), and a fully printed specimen (Try-In) were created. All specimens underwent thermal cycling and mechanical loading (TCML): 1,200,000 × 50 N; 2x3000 x 5°C/55°C; H2O. Surviving specimens were loaded to fracture. Statistical tests used were the Shapiro-Wilk test and the Kaplan-Meier survival, with the level of significance set to α = 0.05.

Mean loading cycles until failure varied between 100 and 621,667 cycles. Up to five specimens per group failed during TCML. With one exception, all specimens of the entirely CAD/CAM-fabricated group survived TCML. The log-rank (Mantel-Cox) test showed significantly different (P = 0.000) loading cycles between the systems (chi-square test: 28,247; degree of freedom: 8). Failure of the dentures during TCML was characterized by failure of the denture base (2x), denture tooth (13x), mixed base/tooth (3x) or adhesive between base and tooth (1x).

TCML and fracture testing showed different aspects of denture tooth restoration. The results indicated no correlation between fracture force, fracture pattern, and survival cycles. Denture teeth (milled, heat-pressed), bases (milled, printed, pressed), and primer should be matched up to optimize the performance of dentures.