Dimensional stability of double-processed complete denture bases fabricated with compression molding, injection molding, and CAD-CAM subtraction milling

Statement of problem. Studies evaluating the dimensional stability of denture bases fabricated by the double processing method are lacking. Purpose. The purpose of this in vitro study was to evaluate the dimensional stability of denture bases fabricated by 3 different techniques: compression molding, injection molding, and computer-aided design and computer-aided manufacturing (CAD-CAM) subtraction milling. Material and methods. Forty-five mandibular denture bases were fabricated from a master cast by a standardized process. A double processing protocol was used with 3 methods: compression molding (PRESS), injection molding (INJECT), or CAD-CAM (CAD). The bases were compared with the titanium master cast after the first processing. By a digital subtraction process, the dimensional stability of the bases was measured at 22 different locations on the intaglio surface. Denture teeth were then positioned according to a standardized protocol, and the denture was processed a second time and finished. The dimensional discrepancy was reassessed after the second processing and compared with the titanium master cast. Results. In all groups, most of the dimensional changes occurred during the first processing (P<.05), with no statistically significant deformation occurring during the second processing (P>.05). The CAD group presented significantly smaller dimensional changes than PRESS (P<.05) and INJECT (P<.05) groups. No significant difference was found in the dimensional stability in the PRESS and INJECT groups (P>.05). Conclusions. Denture bases fabricated by a CAD-CAM methodology exhibit fewer dimensional changes than either compression or injection molding. Distortion occurred during the fabrication of the denture base, and a second processing did not significantly affect the dimensional stability of the denture base.