Comparison of Dimensional Accuracy and Stability of 3D-Printed, Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM), and Conventional Polymethyl Methacrylate (PMMA) Denture Base Materials: An In Vitro Study

Abstract

INTRODUCTION: This in vitro experimental study aimed to evaluate and compare the dimensional accuracy and stability of polymethyl methacrylate (PMMA) denture base materials fabricated by three distinct techniques: conventional heat polymerization, computer-aided design/computer-aided manufacturing (CAD/CAM) milling, and three-dimensional (3D) printing. The objective of this study was to assess the influence of fabrication methods on the dimensional integrity of denture bases after processing and to simulate clinical conditions to determine which technique provides superior accuracy and minimal deformation over time. MATERIALS AND METHODS: This in vitro experimental study was conducted at the Department of Prosthodontics, Maharaja Ganga Singh Dental College and Research Centre, Sri Ganganagar, Rajasthan, between May and December 2024. A master die (25 mm × 25 mm × 3 mm) was designed using AutoCAD 2024 (Autodesk Inc., USA) and milled using Plexiglass (Plazit Polygal India Pvt. Ltd., India). The Standard Tessellation Language (STL) file was used to cut a plexiglass (Plazit Polygal India Pvt. Ltd., India) template, which was then utilized for conventional compression molding. This process resulted in an actual master die, which was used to create molds for fabricating conventional PMMA specimens. The same STL file was used for fabricating CAD/CAM-milled and 3D-printed specimens, ensuring uniformity across all test specimens. The specimens were divided into three groups (n = 40 each). Group 1 used Triplex Hot PMMA (Ivoclar Vivadent AG, Liechtenstein) processed by compression molding and heat polymerization. Group 2 consisted of specimens CAD/CAM-milled from Ivotion Base discs (Ivoclar Vivadent AG, Liechtenstein) using a five-axis milling machine (Arum 5X-500, Doowon, South Korea). Group 3 included 3D-printed specimens fabricated from 3D Accuprint denture resin (D-Tech Dental Technologies, India) using a digital light processing (DLP) printer (Phrozen, Taiwan). All specimens were thermocycled 50 times between 5°C and 55°C (SD Mechatronik, Germany) and immersed in artificial saliva (Wet Mouth, ICPA Health Products Ltd., India) for seven days. Dimensional changes were evaluated using digital calipers (Mitutoyo, Japan) for 2D linear measurements and 3Shape extraoral scanning (3Shape A/S, Denmark) with Geomagic Control X (3D Systems, USA) for 3D superimposition. RESULTS: All the groups exhibited statistically significant reductions in length, width, and depth (p = 0.000). Intergroup comparisons showed no significant differences in the linear dimensions (p > 0.05). However, 3D superimposition showed significant differences (p = 0.000), with CAD/CAM demonstrating the least deviation (0.06 mm), followed by 3D printing (0.11 mm) and conventional printing (0.22 mm). CONCLUSION: CAD/CAM milling showed superior dimensional accuracy and stability compared with 3D printing and conventional methods. Statistical analysis confirmed significant differences among the groups, with CAD/CAM-milled PMMA outperforming both alternatives. These findings support the use of CAD/CAM milling for precision-driven prosthodontics, with 3D-printed PMMA serving as a viable alternative for customization.