Decompression of Large Cyst Invading the Mandibular Canal Leading to Reduced Cyst Volume and Increased Mandibular Canal Length

Abstract

Purpose: The mandibular canal is damaged by the growth of cysts, and remodeling of the mandibular canal is observed as the size of the cyst decreases after decompression procedures. This study aimed to estimate changes in cyst volume and mandibular canal length using cone-beam computed tomography (CBCT) before and after decompression surgery. Materials and Methods: A retrospective cohort study was conducted in patients with a diagnosis of mandibular cyst invading the mandibular canal between 2012 and 2018. All patients underwent CBCT at the initial visit and after decompression. The predictor variable was the period before decompression and before enucleation surgery. The outcome variables were changes in cyst volume and mandibular canal length, which were evaluated 3-dimensionally. The initial volume of the cyst, initial length of the mandibular canal, and patient's age were set as variables of interest that affected the outcome. Results: Decompression was performed in 20 patients (18 male and 2 female patients), and the mean decompression duration was 8.81 ± 2.94 months. The average volume reduction rate after decompression was 60.23%, with an average volume reduction speed of 0.72 mL/month. The average length increase rate after decompression was 50.88%, and the average speed of length increase was 2.68 mm/month. The initial volume of the cyst and initial length of the mandibular canal were the important variables affecting the results. Complete separation of the mandibular canal from the cyst was observed in 11 cases, and incomplete separation was found in 9. Conclusions: Separation from the cyst and regeneration of the mandibular canal using decompression were observed using 3-dimensional CBCT analysis. The results of this study suggest that decompression is effective in separating and preserving important anatomic structures invaded by the cyst. © 2020 American Association of Oral and Maxillofacial Surgeons