الفهرس 
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Abstract
Statement of the problem: Tooth wear in bruxing patients may lead to the need of restorative treatment and occlusal splints as a protective measure, however the wear between the occlusal splints and opposing restorations had not been identified yet. Objective: The aim of this in vitro study was to evaluate wear of different occlusal splints and opposing fixed restorations. Materials and methods: Three different occlusal splints with two different antagonists were used. A full dentate typodonte was used so each group had 10 specimens with an occlusal splint on the upper arch opposing crowns on the lower posterior molars either porcelain fused to metal (PFM) crown or veneered poletheretherketon (PEEK ). group I: 3D printed occlusal splint group II: Heat-cured occlusal splint group III: vacuum-formed occlusal splint. All specimens were polished till obtaining convergent surface roughness values of the three materials. All the specimens were subjected to chewing simulation test including the application of 5kg (49N) load for 75,000 cycle to simulate 6 months with vertical movement 1mm, horizontal movement 3mm and frequency 1.6Hz. Baseline surface roughness and volume loss of all the specimens were obtained using optical surface profiler before and after chewing simulation. Statistical analysis was performed as follow: descriptive statistics ,Student t-test and one-way ANOVA followed by Tukey’s post-hoc. Pearson’s correlation was done between volume loss and roughness change. Results: according to the splint surface: Gr I recorded the lowest surface roughness change and volume loss (p≤0.0001, p=0.0013<0.05). Total roughness change against PFM was statistically non-significant higher than the change mean value against PEEK (p=0.4435> 0.05). Total volume loss against PFM was statistically significant higher than the volume loss against PEEK (p=0.014< 0.05). Total surface roughness and volume loss of the two types of fixed restoration were comparable to each other with the PFM crowns had the highest roughness change and the PEEK crowns had the highest volume loss. Pearson linear correlation (Correlation coefficient (r) = 0.1234, r2= 0.0152 and p > 0.05) showed that there was weak positive relation between surface roughness and volume loss. Conclusion: 3D printed occlusal splints had the least wear change after wear simulation for 6 months. The effect of antagonist on the wear of splint could be considered as PFM cause more wear on the splint than the PEEK.