Shear Bond Strength of Artificial Teeth to Conventional and Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) Denture Bases: An In Vitro Comparison

TL;DR

This study compares how well different types of artificial teeth stick to denture bases made with traditional and digital methods.

Contribution

The study introduces a direct comparison of bond strength between conventional and CAD/CAM denture materials with various artificial teeth.

Findings

CAD/CAM-milled teeth on CAD/CAM bases showed the highest shear bond strength.

Conventional heat-cured bases with composite teeth had stronger bonds than acrylic teeth.

Material compatibility significantly affects bond strength.

Abstract

Introduction: Complete dentures remain essential for restoring function and aesthetics in edentulous patients; however, tooth debonding continues to be a leading cause of repair. This in vitro study aimed to compare the shear bond strengths of three types of artificial teeth (crosslinked acrylic, composite, and computer-aided design/computer-aided manufacturing as CAD/CAM-milled teeth) bonded to conventional heat-cured polymethyl methacrylate (PMMA) and CAD/CAM-milled denture base resins.

Materials and methods: Sixty cylindrical specimens (20 mm in height × 25 mm in diameter) were divided into two main groups (n = 30 each) based on the denture base material: conventional heat-cured PMMA and CAD/CAM-milled PMMA. Each group was subdivided (n = 10) according to tooth type: crosslinked acrylic, composite, and CAD/CAM-milled teeth. Teeth were bonded following the manufacturer's protocols for the CAD/CAM group and the standard packing technique for the heat-cured group. The shear bond strength was measured using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed using one-way and two-way analyses of variance with post-hoc tests (p < 0.05).

Results: Mean shear bond strength values were as follows: conventional heat-cured base with composite teeth (272.11 ± 85.44 MPa), acrylic teeth (179.09 ± 74.71 MPa), and CAD/CAM-milled teeth (174.47 ± 43.13 MPa); CAD/CAM-milled denture base with CAD/CAM-milled teeth (359.56 ± 76.62 MPa), acrylic teeth (275.51 ± 89.69 MPa), and composite teeth (237.23 ± 75.71 MPa). Two-way analysis of variance revealed significant main effects for both denture base material and tooth type, with a highly significant interaction effect (p < 0.001, η²p = 0.28). The strongest bond was achieved with CAD/CAM-milled teeth on CAD/CAM-milled denture bases, which was significantly higher than that of all other combinations.

Conclusion: Bond strength is highly dependent on material compatibility. The combination of CAD/CAM-milled teeth and bases from pre-polymerized high-pressure PMMA provides superior adhesion. In conventional heat-cured systems, the composite teeth yield the strongest bond. For optimal clinical durability in digital workflows, matched CAD/CAM tooth-based systems should be preferred.