Dynamic fatigue of 3D-printed splint materials

Objectives: Printed splints may be an alternative treatment for functional disorders. In addition to the selection of materials, the influence of cleaning or polymerisation can affect the dynamic behaviour and fatigue limit of printed materials. Material and Methods: 96 discs (n = 6 per group, 16mmx2mm) were printed (P30+ DLP-printer, Straumann, CH; 100 mu m layer) from splint materials (M1: Luxaprint OrthoPlus, DMG, G; M2: V-Print Splint, Voco, G). Specimens were either automatically cleaned (C1: Straumann P Wash, Straumann, CH) or manually cleaned (C2: Voco Pre-/ Main-Clean protocol, Voco, G). Post polymerisation was performed with LED (P1: Cure, Straumann, CH) or Xenon light (P2: Otoflash N171, Ernst Hinrichs Dental, G). The flexural fatigue limit was determined under cyclic loading in terms of a staircase approach with a piston-on-3-ball-test according to ISO 6872 after 24 h or 60 days water storage (37 degrees C). Specimens were preloaded with 50N and dynamic force was applied for 105 loadings per step (f = 3Hz; steps 1: 50N-100N, 2: 50N-150N, 3: 50N-200N, 4: 50N-250N; F1000, Prematec, G; water at 37 degrees C). Statistics: Kaplan Maier Log Rank (Mantel-Cox) test, ANOVA, Pearson correlations, Levene-test (alpha = 0.05, SPSS 26.0, IBM, Armonk, NY, USA)). Results: Mean survival cycles after 24 h of storage varied between 40388 (M1C2P2) and 195140 (M2C2P1) cycles and after 60 d decreased to 14022 (M1C2P2) and 173237 (M2C1P1). Kaplan Maier Log Rank test revealed significant differences between the material combinations. For M1 cleaning (Pearson: 0.346, p = 0.016) and for M2 polymerisation (Pearson: 0.616, p = 0.000) significantly influenced the number of loading cycles. Intermediate effects were found for material (p = 0.026), cleaning (p = 0.024) and polymerisation (p = 0.000) as well as the combination of material and polymerisation (p = 0.008). Conclusions: The results show that the number of possible loading cycles of additively manufactured splint specimens depends on the type of material, their cleaning and post-polymerisation. Clinical significance: Materials, cleaning and post-polymerisation of additive manufacturing processes should be matched to improve dynamic loading performance of splint materials.

Automated summary

The study found that the number of loading cycles that additively manufactured splint specimens can withstand depends on the type of material, cleaning, and post-polymerisation. Therefore, the materials, cleaning, and post-polymerisation of additive manufacturing processes should be matched to improve the dynamic loading performance of splint materials.