Three-dimensional Reconstruction Study On The Volume Change Of Bone Grafts After Different Maxillary Sinus Lift

Objective:Alveolar bone will be resorbed after maxillary molar lost,combining with the gasification and expansion of maxillary sinus.It often leads to insufficient bone supply for implant at the missing tooth site.Maxillary sinus augmentation is considered to be a reliable method for implant placement in the atrophic maxillary posterior region.The volume of bone grafts after maxillary sinus lift will be decreased to different degrees,Which even affected the service life of the implant.The long-term stability of bone graft materials plays an important role in the outcome of surgery.In this study,conical beam CT scanning and three-dimensional reconstruction software Mimics 19.0 were used to investigate the volume changes of bone grafts post-operation 6 months.In order to provide clinical guidance,the correlation between different influencing factors and the three-dimensional volume changes of bone graft materials will be analyzed.Methods:A total of 46 implants were implanted in 30 patients according to the inclusion criteria.Patients were grouped according to four influencing factors:residual alveolar bone height(RBH),sinus size,surgical mode,and number of teeth lost.CBCT was taken in all patients before surgery(TO),on the day after surgery(T1),and 6 months after surgery(T2).The difference of the residual maxillary sinus volume above the bone graft area at T1 and TO represents the initial volume of the bone graft area(GV).The difference of the residual maxillary sinus volume above the bone graft area at TO and T2 represents the bone graft material volume post-operation 6 months(GV6),The volume change rate of bone graft material 6 months after surgery was observed,It defined as ?GV%=(GV-GV6/GV)%.SPSS 21.0 was used for multiple linear regression analysis,Spearman rank correlation analysis,one-way analysis of variance,Mann-Whitney U test and two independent sample T tests,and P<0.05 was considered statistically significant at the test level.Results:All the 30 patients,including 15 females and 15 males,had no intraoperative and postoperative complications,and the short-term implant survival rate was 100%.The average volume change rate of bone graft at 6 months after surgery was 19.49±12.21%.The results of multiple linear regression analysis showed that sinus size was an independent factor affecting the volume change rate of bone grafts at 6 months after surgery(P<0.05),while other indicators were not affecting factors.Spearman rank correlation analysis was used to observe the correlation between the volume change rate of bone grafts and sinus size.where R=0.434,P=0.017,and there was a positive correlation between the volume change rate of bone grafts and sinus size(P<0.05).Statistical methods including one-way analysis of variance,Mann-whiiney U test and two independent sample T test were used to observe that there was no significant difference in the rate of bone graft volume between the groups.Conclusion:At 6 months after maxillary sinus lift,bone grafts had a certain three-dimensional volume contraction,and the volume change of bone grafts had a certain correlation with sinus size,which was a positive correlation.But the volume change of bone grafts had no significant correlation with RBH,surgical mode and number of missing teeth.There was no significant difference in the rate of volume change of bone grafts between the groups with different RBH,surgical methods and number of missing teeth.Due to the small number of cases included in this study,there are some limitations.Large sample size statistical and histological studies are needed to confirm the factors affecting the three-dimensional volume change of bone graft materials for clinical guidance.