# Comparative Evaluation of the Mechanical Properties of Denture Base Resins Fabricated Using Computer-Aided Design and Manufacturing, Three-Dimensional Printing, and Conventional Heat Polymerization Techniques: An In Vitro Study

## TL;DR

This study compares the strength of denture materials made with 3D printing, CAD/CAM milling, and traditional methods.

## Contribution

The study provides a direct comparison of mechanical properties of PMMA denture resins using modern and conventional fabrication techniques.

## Key findings

- CAD/CAM-milled resins showed the highest flexural strength compared to 3D-printed and conventional resins.
- 3D-printed resins had the highest impact strength, outperforming both CAD/CAM and conventional methods.
- Conventional heat-polymerized resins performed the lowest in both flexural and impact strength.

## Abstract

Introduction: With the advent of digital dentistry, modern fabrication techniques, such as three-dimensional (3D) printing and computer-aided design/computer-aided manufacturing (CAD/CAM) milling, might offer promising alternatives to conventional heat-cured methods. This study aimed to compare the flexural and impact strengths of polymethyl methacrylate (PMMA) denture base resins fabricated using 3D printing, CAD/CAM milling, and conventional heat polymerization.

Materials and methods: An in vitro experimental design was employed to fabricate denture base resin specimens using three different techniques. Group 1 (n = 40) consisted of heat-polymerized PMMA specimens, Group 2 (n = 40) comprised CAD/CAM-milled PMMA disks, and Group 3 (n = 40) included specimens fabricated with 3D-printed PMMA resin. Standardized rectangular samples were prepared for each group and subjected to thermocycling and artificial saliva immersion to simulate oral conditions. The flexural strength was tested using a three-point bend method on a universal testing machine, while the impact strength was evaluated using an Izod-type impact testing machine. Each group consisted of 20 specimens for flexural strength testing and 20 specimens for impact strength testing. Statistical analysis was conducted using one-way analysis of variance (ANOVA) and Tukey’s post hoc test, with a significance level set at p < 0.05.

Results: Flexural strength analysis revealed that the CAD/CAM-milled specimens exhibited the highest mean strength, followed by the 3D-printed and conventional groups. Significant differences were found between the CAD/CAM and the other two groups (p < 0.05), while the 3D-printed and conventional groups showed no significant difference (p > 0.05). Impact strength testing showed that the 3D-printed specimens had the highest mean values, followed by the CAD/CAM and conventional groups. All pairwise comparisons for impact strength were statistically significant, indicating superior energy absorption in the 3D-printed specimens (p < 0.05).

Conclusion: This study demonstrated that CAD/CAM milling resulted in the highest flexural strength, making it favorable for resisting functional stress. However, the 3D-printed resins exhibited superior impact strength, suggesting enhanced resistance to sudden forces.