Abstract
BACKGROUND: Mandibular retraction is a prevalent dental and maxillofacial deformity that negatively affects patients' functional health and facial aesthetics. It has been challenging to achieve optimal outcomes for patients who have passed the peak of growth and development using only functional orthopedic treatment. There is a pressing need to explore innovative methods to promote the adaptive remodeling of adult condylar cartilage and the mandible in response to external stimuli. This study aimed to investigate the impact of varying injection frequencies of stem cells from the apical papilla (SCAPs) on the growth and development of condylar cartilage and the mandible, as well as their potential for adaptive remodeling. METHODS: The study was conducted on 8-week-old adult male Sprague-Dawley rats. The effects of SCAPs injection and different durations of mandibular advancement (MA) on the adaptive remodeling of condylar cartilage and the mandible were assessed. After the initial experimental findings, various injection frequencies of SCAPs were applied to determine the most effective conditions for promoting the growth and adaptive remodeling of condylar cartilage and the mandible during an 8-week period of mandibular advancement. RESULTS: The study found that rats with extended mandibular lead times (8 weeks) or an appropriately increased frequency of mandibular leading time (once every 2 weeks or once every 1 week) exhibited increased lengths of the mandibular body and ascending branch, and a thickened full layer of condylar cartilage. The highest proportions of the proliferative layer, mature layer, and hypertrophic layer were observed in these rats. Additionally, there was a significant increase in the expression levels of SOX9 and COL2A1. CONCLUSION: The data from this study suggest that adult rats, even after missing their peak growth period, retain the potential for continued growth and development of their condylar cartilage. By prolonging the duration of mandibular advancement and administering injections of stem cells from the apical papilla (SCAPs), it is possible to stimulate the growth and development of the mandibular condyle.