Purpose: To investigate the influence of reducing material thickness on flexural properties of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base resins.
Materials and methods: Four CAD-CAM denture base acrylic resin materials were selected; two were made via the subtractive method (AvaDent and IvoCad) and two were made with the additive method (FormLabs and NextDent). One heat-polymerized denture base material was used as a control. Specimens were fabricated with varying thicknesses (n = 10/group): 3.3 mm, 2.5 mm, 2 mm, or 1.5 mm. Flexural strength was evaluated via a three-point bending test. One- and two-way ANOVA were used for data analysis along with Tukey's post hoc comparison (α = 0.05).
Results: Reducing the thickness of materials made via the subtractive method did not influence flexural strength up to 2 mm (p > 0.05). However, the difference was significant at a 1.5 mm thickness (p ˂ 0.001). For materials made via the additive method, NextDent specimens had no significant decrease in flexural strength when the thickness was reduced to 2 mm (p = 0.58). FormLabs specimens showed a significant decrease (p ˂ 0.001), although the values of flexural strength were clinically acceptable. During testing, specimens manufactured via the additive method at a 1.5 mm thickness bent without fracturing and were therefore excluded. All materials showed a reduction in elastic modulus as the thickness decreased (p ˂ 0.001).
Conclusion: Heat-polymerized, AvaDent, and IvoCad materials may be used for denture base fabrication at a minimum thickness of 1.5 mm. FormLabs and NextDent may be fabricated at a 2 mm minimum thickness, with clinically acceptable flexural properties.
Keywords: CAD-CAM; PMMA; denture base thickness; digital dentistry; flexural properties.
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