Abstract: Objective To analyse the volume and three-dimensional direction changes of maxillary bone cyst treated by endoscopic and transnasal fenestration through three-dimensional modelling and model registration, and to explore the difference in volume reduction and three-dimensional contraction of maxillary cyst treated by endoscopic and transnasal fenestration. Methods The data of patients with maxillary bone cyst diagnosed in Yantai Stomatological Hospital Affiliated to Binzhou Medical College from June 2019 to June 2022 were collected. The operation was divided into two methods: transoral fenestration, transnasal endoscopy intranasal fenestration with nasal base and inferior nasal canal fenestration. Materialise Mimics 21 and 3-matic software were used for 3D reconstruction to measure changes in volume, proximal and distal diameter, buccolingual diameter and height. Results The regression models of volume percentage and time of the two groups were obtained: V₁=-0.007×t3+0.462×t2-10.175×t+99.481(P<0.001, R=0.956, adjusted R²=0.904); V₂=-0.018×t3+0.872 t2-13.834×t+99.978(P <0.001, R=0.964, adjusted R²=0.919), the volume contraction rate of the endoscopic intranasal fenestration group was higher than that of the transoral fenestration group in the first 6 months. The capsule volume in the transoral window group remained stable at 22 months. The volume of the two groups was similar after stabilisation of the changes in the cystic cavity. The percentage change of the three-dimensional direction in the transoral fenestration group was adjusted by a regression model: X₁=-2.23×10^-4×t3+0.074×t2-3.652×t+98.979(P<0.001, R=0.91, adjusted R²=0.811); Y₁=-0.005×t3+0.288×t2-5.638×t+100. 028(P< 0.001, R=0871, adjusted R2=0.734); Z₁=0.079×t2-3.880×t+97.633(P<0.001, R=0.917, adjusted R2=0. 830); The regression model of percentage and time of 3D direction change of the nasal window group was as follows: X₂=0.072×t2-3.346×t+98.80(P<0.001, R=0.945, adjusted R²=0.883); Y₂=-0.001×t3+0.127×t2-4.036×t+99.138(P<0.001, R=0.892, adjusted R2=0.766); Z₂=0.074×t2-3.758×t+99.209(P<0.001, R=0.961, adjusted R²=0.916). The maxillary cyst changed mainly in height after intranasal fenestration under nasal endoscope. Maxillary cyst after transoral fenestration mainly changed in proximal and distal diameter and height. Conclusion Transoral fenestration for maxillary bone cyst and intranasal fenestration under nasal endoscope for maxillary apical cyst have similar clinical effects in terms of volume contraction, and intranasal fenestration under nasal endoscope will shrink the volume faster. Accurate prediction of morphological changes of maxillary apical cyst can provide some reference for clinical work.

Key words: Maxillary cyst, Transoral fenestration, Intranasal fenestration under nasal endoscopy, 3D modeling and model, Registration, Regression model