Comparative evaluation of the flexural strength of two different CAD/CAM-milled PMMA for long-term fixed provisional restorations

Abstract

Aim: To determine and compare the flexural strength (FS) of heat-cured poly methyl methacrylate (PMMA) resin, CAD/CAM-milled PMMA resin, and CAD/CAM-milled PMMA resin reinforced with graphene.

Materials and methods: In accordance with ISO 10477:2018, thirty rectangular samples with measurements of 25 mm (l) x 2 mm (b) x 2 mm (h) were manufactured for the purpose of FS evaluation (Dentistry-polymer-based crown and veneering materials). PMMA resin samples that were heat-cured (Group-I; n = 10), CAD/CAM-milled (Group-II; n = 10), and CAD/CAM-milled PMMA resin reinforced with graphene (Group-III; n = 10) were produced and sorted according to the kind of material. Before testing, the samples were kept for a full day in distilled water. For each of the thirty samples, a 3-point bend test was conducted utilizing a universal testing machine at a crosshead speed of 1.0mm/min till breakage. Utilizing a One-way ANOVA and the post hoc Tukey HSD test, the FS data were tabulated and statistically analyzed.

Results: For the test samples in Group I, the mean flexural strength was 550.29 MPa. For Group II the mean flexural strength was 1481.966 MPa. For Group III the mean FS was 1447.45 MPa. A comparative assessment of Group I test samples, Group II test samples, and Group III test samples showed that the mean FS is highly significant (P < 0.001∗∗). On multiple comparisons, the mean FS difference between Group I test samples and Group II test samples was observed to be highly significant (P < 0.01∗∗). The mean FS difference between Group I test samples and Group III test samples was observed to be highly significant (P < 0.01∗∗). The mean FS difference between Group II and Group III was observed to be insignificant (P > 0.05∗ ).

Conclusion: CADCAM-milled PMMA resin showed the maximum FS followed by CADCAM-milled PMMA resin reinforced with graphene and heat-polymerized PMMA. Therefore, CADCAM PMMA–based polymers could be utilized for long-term provisional restorations in comparison to heat-polymerized poly methyl methacrylate (PMMA) resin.