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.