Changes in bone graft height and influencing factors after sinus floor augmentation by using the lateral window approach: A clinical retrospective study of 1 to 2 years

Statement of problem Recent systematic reviews have reported resorption of bone grafts after augmentation, but the influencing factors are numerous and uncertain. Different brands of bone graft and other factors may affect the bone formation effect after sinus floor augmentation. Purpose The purpose of this retrospective clinical study was to evaluate the graft material height changes after sinus floor augmentation with cone beam computed tomography (CBCT) and to investigate the potential influencing factors related to graft resorption. Material and methods Four midsagittal cut CBCT images of 157 posterior maxillary implants after maxillary sinus floor elevation by using the lateral window approach with bone grafts from 116 patients were obtained. Four CBCT scans had been performed immediately (T0), 6 months (T1) and 12 months after bone grafting (T2), and 1.5 to 2 years after treatment (T3), and the distance between the implant platform and the grafted mucosa of the maxillary sinus floor was measured at 3 locations. Correlation coefficients of these parameters were calculated. A linear mixed model was used to investigate potential factors influencing graft height reduction, including the patient's sex, age, smoking status, periodontal status, graft brand, implant site, implant level, placement time, and residual bone height. Results Mean ±standard deviation graft height at the mesial side of the implant (MeGH) was significantly decreased by 0.32 ±0.88 mm in the first 6 months, was gradually reduced after 6 months (0.26 ±0.43 mm), and then 1 to 2 years later increased to 0.39 ±0.97 mm. The changes in graft height at the center of the implant (CeGH) and graft height at the distal side (DiGH) groups were similar to those in the MeGH group. A significantly positive correlation was found among the height alterations in 3 locations (rs=0.954, P<.001). The linear mixed model showed that smoking was more likely to cause graft height reduction in MeGH (P=.034). Conclusions Graft height significantly decreased after maxillary sinus augmentation over 1 to 2 years. Smoking had a negative effect on graft height changes, while the 2 brands of graft and other factors had no significant effect.