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Flexural Strength, Monomer Release, and Wear of Occlusal Splint Materials Fabricated Through Conventional, Milled, or
Nurul Liyana Aminuddin1,2, Haralampos Petridis1
1Department of Prosthodontics, UCL Eastman Dental Institute, London, England, UK.
Objective:
To evaluate the flexural strength, monomer release, and wear resistance between conventional, milled polymethylmethacrylate (PMMA), and 3D-printed resins built at 90° and 60° printing angles for occlusal splints.
Materials And Methods:
60-rectangular and 100-disc specimens were fabricated from heat-cured PMMA (Oracryl [HP], Bracon Dental, United Kingdom), milled PMMA (Kerox Premia [KP], Kerox Dental, Hungary), and 3D-printed resins (FreePrint Splint2.0 [FS], Detax, Ettlingen, Germany, and KeySplint Hard [KS], Keystone Industries, Myerstown, USA) at 90° and 60° printing angles. Specimens for flexural strength and wear tests were immersed immediately in 37°C water for 50 h and thermally aged for 20,000 cycles. Flexural strength was evaluated using a three-point bend test. Wear was tested using a chewing simulator for 140,000 cycles, and volume loss was calculated using Autodesk MeshMixer software. Monomer release was analyzed via UV spectrophotometry over 7 days. Statistical analysis was performed using the Shapiro-Wilk test and one-way ANOVA with Tukey's multiple comparison tests.
Results:
KP showed the highest mean flexural strength (115.5 ± 5.3 MPa, p < 0.0001), followed by HP (86.6 ± 10.8 MPa, p < 0.0001), with 3D-printed resin showed the lowest. Meanwhile 90° FS showed greater flexural strength (60.5 ± 3.8 MPa) compared to 60° FS (p < 0.001) and KS (p < 0.01). The difference between 90° and 60° KS were not statistically significant (p > 0.05). Monomer release peaked on Day 3 for all groups, with KS consistently showing the highest concentration (29.7 ± 3.6 ppm), followed by FS (28.8 ± 3.8 ppm), HP (27.9 ± 4.9 ppm), and lastly, KP showed the lowest concentration (24.9 ± 3.8 ppm). KP demonstrated the lowest mean volume loss (2.5 ± 1.3 mm3, p < 0.01), followed by HP (4.4 ± 1.7 MPa), whereas 3D-printed resin showed the highest. No significant wear differences were observed between 90° and 60° printing angles.
Conclusion:
Milled PMMA outperformed other materials, followed by conventional PMMA, while 3D-printed resin showed inferior performance in flexural strength, wear resistance, and monomer release. Printing angles significantly influenced flexural strength but not wear properties in 3D-printed resins.
