Biocompatibility and cytotoxic effects of myofunctional appliance materials on human periodontal ligament fibroblasts

Background/purpose Prefabricated myofunctional devices are widely used in children's dentistry and early orthodontics. This study investigated the effects of materials used in myofunctional appliances on the viability of human periodontal ligament fibroblasts (HPLFs), inflammatory responses, and bone remodeling under simulated oral conditions. The focus was on biocompatibility and cytotoxicity to ensure safety in clinical applications. Materials and methods Four materials—EF Line (EF), ProOrtho (PO), Myobrace (MB), and Invisalign (IV)—were tested under conditions with and without artificial saliva (AS). HPLFs were cultured and exposed to eluates from these materials for 24, 48, and 72 h. Cell viability was measured using the MTT assay, and protein expression of inflammatory and bone remodeling markers (COX-2, IL-1, IL-6, TNF-α, ALP, OPG, RANKL) was evaluated using Western blotting. Results A 30 % AS concentration had minimal impact on cell viability and was used in subsequent experiments. EF showed significant cytotoxicity and elevated inflammatory protein expression, particularly IL-6 and COX-2, peaking at 48 and 72 h. PO exhibited moderate effects, while IV and MB maintained higher cell viability and lower inflammatory responses, similar to the control group. For bone remodeling markers, EF demonstrated high RANKL expression and low ALP/OPG levels, indicating bone resorption potential. In contrast, IV and MB had minimal impact on bone remodeling, maintaining a favorable RANKL/OPG ratio. Conclusion MB and IV demonstrated higher biocompatibility, minimal inflammatory effects, and stable bone remodeling properties. EF and PO exhibited higher cytotoxicity and inflammatory potential, maybe needed further material modifications to improve properties.