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Comparative in vitro study on wear resistance and colour stability of 3D-printed, milled, and conventional PMMA
Yasmine Mahmoud Mohamed Elsharkawy1,2, Hebatallah Tarek Mohamed3, Tarek Mohamed Al Sayed El Saeedi3
1Department of Oral and Maxillofacial Prosthodontics, Faculty of Dentistry, Ain Shams University, Cairo, Egypt. yasmine.elsharkawy@dent.asu.edu.eg.
Background:
Digital dentures are a promising alternative to the conventional fabrication technique. However, their mechanical and optical properties require further evaluation, so this study aims to compare the wear resistance and colour stability of milled and 3D-printed polymethyl methacrylate denture teeth to conventional teeth. This is essential as too much wear can cause a loss of the vertical dimension of occlusion (VDO), which can compromise the chewing efficiency, esthetics, and even cause the dentures to break.
Methods:
Mandibular first molars denture teeth were manufactured using three different techniques, which were chosen to be assessed for wear resistance and colour stability. In the first group, conventionally prefabricated mandibular first molars were used; in the second group, the molars were milled from PMMA blocks; in the third group, the molars were fabricated from 3D printing resin (n = 7). The teeth were loaded on the chewing simulator to simulate the intraoral conditions, and then the volumetric changes were evaluated using surface matching software. Teeth were subjected to aging using the thermocycler, and colour stability was evaluated using a spectrophotometer.
Results:
The null hypothesis was rejected, indicating significant differences between the groups. For wear resistance, the highest mean wear (RMS) value was reported in the conventional group, 1.806 ± 0.085, followed by the printed group, 0.021 ± 0.006, and then the milled group, 0.019 ± 0.005. For colour stability, the highest mean value of colour change (Delta E) was reported in the printed group 2.996 ± 0.445, followed by the conventional group 2.725 ± 0.234, and then the milled group 0.539 ± 0.118.
Conclusion:
Milled PMMA generally demonstrates better wear resistance and colour stability compared to 3D-printed and conventionally processed PMMA. 3D-printed PMMA exhibits comparable wear resistance to milled PMMA. 3D-printed PMMA demonstrated comparable colour stability to conventional resin.
