A Quantitative Study Of Bone Augmentation In Osteotome Sinus Floor Elevation Based On CBCT

The Osteotome sinus floor elevation(OSFE)creates a new bone augmentation space by minimally invasively lifting the sinus mucosa through the osteotome,which better solves the implanting problem of insufficient alveolar bone after tooth loss in the posterior region of the maxilla.However,since the process of osteotome and grafting is performed under blind operation,there is a certain risk of mucosal perforation.Traditional osteotome has been improved to reduce the irritation to the mucosa,but the quantitative grafting is currently rarely studied.In order to find the best effect of grafting,while avoiding the risk of mucosal perforation associated with excessive grafting,it is necessary to explore how to find a relatively suitable volume of the bone grafted under variable objective conditions.The popularity of CBCT and the development of digital medicine have made it possible to accurately observe the effect of graftingt in OSFE.In view of the uncertainty of the lifting space for traditional surgery and the possible reconstruction of grafting during the healing period,this research will be studied from two aspects:immediate postoperative and preprosthetic CBCT.Objective:(1)Discuss the influence factors of the volume of the bone grafted by observing the immediately postoperative status of bone augmentation,and to predict the lifting volume according to the significant influence factors,then provide the gist for the preoperative design of grafting volume.(2)Evaluate the volumetric change of Bio-Oss volume during healing period based on CBCT,and to explore the conditions for best effect of grafting after the healing period,and to further improve the preoperative program of grafting volume.Method:(1)Select 37 cases after Osteotome sinus floor elevation with grafting at the Stomatological Hospital offormer Chengdu General Hospital from September 2015 to June 2018,a total of 41 lifting sites.Then import the data of immediate postoperative CBCT into the Mimics Innovation Suite software package to reconstruct the lifting area,measure the volume and height of the lifting,and classify the lifting sites by the morphology of the local maxillary sinus floor.The possible influence factors of elevation volume were analyzed by single factor analysis and multiple linear regression,then established the predicting equation of multiple regression analysis.(2)Collect 18cases after Osteotome sinus floor elevation with grafting(Bio-Oss)at the Stomatological Hospital offormer Chengdu General Hospital from September2017 to December 2018.Then import the data of immediate postoperative CBCT and pre-prosthetic CBCT into the Mimics Innovation Suite software package,the lifting areas at two time points were reconstructed,then measure the volume of grafting and lifting height.And utilize the paired sample t-test to check the difference of indexes between two time points.Then classify the sample into two categories according whether there is complete bone wrapping around the top of the implant,and use the independent sample t-test to check how the height of the bone graft at the top of the implant at immediate postoperatively effect state of the bone augmentation before repair.Result:(1)There is a linear correlation between lift height and lift volume(r=0.646,P<0.001).The sinus floor shape and elevation height are incorporated into the multiple regression mode,both of them are significant factors influencing the volume.The prediction equation is:lifting volume(mm~3)=–2.059–65.625(sinus floor is steep from one angle)–182.368(sinus floor is steep from double angle)+64.543×lifting height(mm),F=31.993,P<0.001.R~2=0.722.The predicted absolute error is 38.16 mm~3 and the relative error is 14.77%.(2)The statistical values of grafting volume change between immediately after surgery and before repair were:t=6.67,P<0.05.In addition,the statistical value of lifting height change was t=7.28,P<0.05.After an average healing period of 6.94±1.21 months,the volume shrinkage of Bio-Oss was 15.27±5.88%,and the height reduction rate was22.95±13.65%.Immediately after the operation,the height of the bone graft at the top of the implant had a significant effect on the incremental state of the bone augmentation before repair(t=4.14,P<0.05).Conclusion:(1)The elevated height and the morphology of local sinus floor were the main factors which would influence the elevated volume.Use these two variables to predict the lifting volume was of high reliability.(2)A certain degree of contraction and reconstruction of grafting will occur during the healing period when OSFE graft with deproteinized xenograft;additional grafting placed on the top of the implant during surgery will help to form a complete wrap around the top of the implant after healing period.