Calculation of postoperative bone healing of cystic lesions of the jaw—a retrospective study

Objectives: There is a long history of studies into cystic lesions of the jaws. However, there is little data on postoperative bone regeneration. The aim of the study was to calculate the size of the residual bone lesions after cystostomies and cystectomies to predict the postoperative bone healing. Material and methods: This retrospective study focused on patients undergoing cystectomy (n = 114) or cystostomy (n = 86), who were treated for cystic lesions between 2010 and 2015. New formulas were developed to measure the decrease in lesion sizes using the craniocaudal and mesiodistal diameters from preoperative as well as postoperative radiographs (panoramic radiographs, CT scans, CBCT). With these predictive models (calculated by linear regression analyses), it is possible to calculate how the lesions would shrink using initial size of the cyst and time after surgery for both dimensions. Results: After cystostomy, the mesiodistal size was initial size 6.0 + 0.7 × initial size − 9.4 × time. The craniocaudal size was 5.1 + 0.7 × initial size − 7.3 × time. After cystectomy, the mesiodistal size was 0.4 + 0.7 × initial size − 8.4 × time. The craniocaudal size was 0.4 + 0.5 × initial size − 6.4 × time (R² = 0.59 and 0.67, respectively). Conclusion: These formulas are suggested to be used to calculate residual size of bone lesion after cystostomy and cystectomy to predict postoperative bone healing. Clinical relevance: The formulas are based on deliberately simple measurement using only panoramic radiographs to encourage their application in daily clinical practice.