Comparison of hardness and polishability of various occlusal splint materials

Anastasiia Grymak; John M Aarts; Sunyoung Ma; John Neil Waddell; Joanne Jung Eun Choi

doi:10.1016/j.jmbbm.2020.104270

Comparison of hardness and polishability of various occlusal splint materials

J Mech Behav Biomed Mater. 2021 Mar:115:104270. doi: 10.1016/j.jmbbm.2020.104270. Epub 2020 Dec 17.

Authors

Anastasiia Grymak¹, John M Aarts¹, Sunyoung Ma¹, John Neil Waddell¹, Joanne Jung Eun Choi²

Affiliations

¹ Faculty of Dentistry, Sir John Walsh Research Institute, University of Otago, New Zealand.
² Faculty of Dentistry, Sir John Walsh Research Institute, University of Otago, New Zealand. Electronic address: joanne.choi@otago.ac.nz.

PMID: 33341739
DOI: 10.1016/j.jmbbm.2020.104270

Abstract

Objectives: To measure polishability of occlusal splint materials manufactured by various methods.

Methods: Seven occlusal splint materials manufactured by four different methods - Heat cured (Vertex Rapid simplified Clear), CAD-milled (Ceramill a-splint), Vacuum-formed (Proform splint) and 3D-printed (Freeprint Ortho, KeySplint Soft, DentaClear and FreePrint Splint 2.0) were tested for gloss, roughness, and surface hardness and elastic modulus. For all groups, the tests were repeated with the materials polished with three different polishing burs, pumice and high shine. All polishing procedures were standardised by applying the force of 1 N for 1 min at the set speed. 3D printed materials were further tested with additional specimens manufactured at different printing angles of 0°, 45° and 90°. Data was statistically analysed using ANOVA (SPSS Version 26) and MatLab (R2020a). Polished surfaces of each specimen were analysed under scanning electron microscope.

Results: Vacuum-formed materials showed the highest polishability (80.61 ± 0.98 GU) with no statistical significance to heat-cured or CAD-milled (p = 1.00). Pumice and high shine polish significantly improved the gloss for all groups. The mean gloss and surface roughness for all 3D-printed materials ranged from 75.24 ± 25.05 GU to 0.18 ± 0.21 GU and 2.73 ± 3.18 μm to 0.06 ± 0.01 μm, which was significantly lower (p < 0.001) than heat-cured, CAD-milled and vacuum-formed materials. The highest hardness (0.40 ± 0.009 GPa), elastic modulus (6.06 ± 1.49 GPa) and gloss were found when materials were 3D-printed at 45°, with the lowest surface roughness.

Conclusion: Statistically significant differences in polishability were found among the different occlusal splint materials. The polishability and surface hardness of 3D-printed occlusal splint materials was influenced by the print angle. The 0° 3D-printed occlusal splint materials produced the highest gloss and the lowest surface roughness pre-polished, indicating that no polishing is required. While the 3D-printed occlusal splint materials at 45^oand 90° required polishing with burs, pumice and high shine to reduce the surface roughness, there were layering structures created during printing.

Keywords: 3-D printing; CAD/CAM; Mechanical properties; Occlusal splint; Polishability; Surface gloss; Surface roughness.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Dental Polishing*
Hardness
Materials Testing
Occlusal Splints*
Surface Properties