Linear and volumetric wear of conventional and milled denture teeth

Abstract

Objective: The purpose of this study was to compare the linear and volumetric wear of conventional and milled double-cross-linked polymethyl methacrylate, nano-composite, and nano-ceramic infused resin posterior denture teeth.

Methods: Double-cross-linked polymethyl methacrylate (PMMA) premolar teeth were scanned and used to mill denture teeth from a double-cross-linked PMMA resin disc and a nano-composite with nano-ceramic infused resin disc. The specimens (n = 8: conventional double-cross-linked PMMA resin teeth-DCL, milled double-cross-linked PMMA resin teeth-DCL-CAM, conventional nano-composite infused resin teeth with four layers composed of composite and PMMA resin teeth-NC, and milled nano-composite and nano-ceramic infused resin teeth-NC-CAM) underwent chewing simulation in the biaxial fatigue testing machine at 1.53 Hz frequency, thermocycling between 5 and 55°C, and 49 N force against a Ø6mm steatite. After 250,000 cycles, the linear changes on the occlusal surfaces of the specimens were analyzed with pairwise comparison with Bonferroni post hoc test, and the volumetric changes of the specimens were analyzed with a one-way ANOVA with Bonferroni post hoc test (p < 0.05).

Results: The linear wear of the conventional and milled denture teeth was linearly correlated with the number of cycles between 50,000 and 250,000 cycles. After 250,000 cycles, NC had significantly more linear and volumetric wear (0.52 ± 0.10 mm and 4.29 ± 0.94 mm³ ) than DCL (0.18 ± 0.03 mm and 0.74 ± 0.14 mm³ ; p < 0.001) and NC-CAM (0.15 ± 0.03 mm and 0.35 ± 0.21 mm³ ; p < 0.001). DCL-CAM and NC-CAM had linearly and volumetrically equivalent wear to DCL (p > 0.05). NC-CAM had significantly less linear and volumetric wear (0.15 ± 0.03 mm and 0.35 ± 0.21 mm³ ) than DCL-CAM (0.24 ± 0.07 mm and 1.22 ± 0.61 mm³ ; p < 0.05).

Conclusions: The conventional NC wore more than DCL, DCL-CAM, and NC-CAM. Both milled denture teeth wore an equivalent amount to conventional DCL. The wear between the conventional and milled DCL was equivalent.

Clinical significance: Denture teeth selection can prolong the retreading process and decrease the occurrences of prosthetic complications. Milled denture teeth are good alternatives to conventional denture teeth with regards to their wear resistance.

Keywords: computer-aided design; computer-aided manufacturing; conventional denture teeth; denture tooth Wear; digitally fabricated denture teeth.