Comparative volumetric wear of occlusal splint materials under simulated gastric acid and artificial saliva conditions

Abstract

Abstract Background Wear of occlusal splint materials may alter appliance geometry and occlusal relationships during use. This in vitro study evaluated the volumetric material loss of four commercially available occlusal splint materials differing in polymer composition and manufacturing technology after mechanical loading in artificial saliva and simulated gastric acid. Methods A total of 128 specimens were prepared from two digital light processing (DLP)-printed PMMA-based resins (Detax Freeprint Splint and Armarez), one CAD/CAM-milled PEEK material (PEEK Biosolution), and one conventionally injection-molded polyamide material (Cool&Flex). The specimens were allocated to artificial saliva or simulated gastric acid and subjected to either 30,000 or 120,000 chewing cycles. Baseline and post-simulation stereolithography datasets were superimposed, and volumetric material loss was calculated in mm³. The effects of material, storage medium, chewing-cycle number, and their interactions were evaluated using robust factorial ANOVA based on 20% trimmed means. Results Volumetric material loss was significantly associated with material ( p < 0.001, partial η² = 0.881), chewing-cycle number ( p = 0.001, partial η² = 0.626), and the material × chewing-cycle interaction ( p = 0.001, partial η² = 0.752). The main effect of storage medium was not statistically significant ( p = 0.054). When values were pooled across both storage media and chewing-cycle conditions, Cool&Flex showed the greatest volumetric material loss (20% trimmed mean ± SE: 1.171 ± 0.193 mm³), whereas comparatively low values were observed for PEEK Biosolution (0.079 ± 0.014 mm³) and Armarez (0.087 ± 0.020 mm³). Conclusions Under the conditions of this in vitro study, volumetric material loss differed among the tested commercial products and increased with mechanical loading, although the magnitude of this increase varied by material. Storage in simulated gastric acid did not significantly affect volumetric material loss. Because polymer composition and manufacturing method varied simultaneously among the products, their independent effects cannot be distinguished. These findings are limited to the materials and experimental conditions evaluated and should not be interpreted as direct predictions of clinical longevity.

The authors' abstract, as published at the source. BMC Oral Health, 2026 · DOI ↗