The Stability Of Hard Tissue After Simultaneous GBR In The Mandibular Posterior Area By Means Of Cone-beam Computer Tomography

Objectives:The aim of this study is to measure the horizontal width and vertical height of the implant sites with simultaneous GBR on CBCT preoperatively as well as postoperatively,and evaluate the efficiency of the augmentation and the stability of the augmented hard tissue.Material and methods:The pre-operative and post-operative CBCT data of the included patients were imported into NNT and the horizontal width(HW)of the hard tissue at 0/1/2/3/4mm below the implant shoulder was measured.SPSS software was used for data analysis and statistical analysis.Results:A total of 66 implant sites in 37 patients with a mean age of 50.57 years old were included,with an average follow-up time of 2.7±1.0 years.Pre-operatively(T1),the horizontal width at the level of 0-4mm apical to the implant shoulder was 4.20±2.55 mm,5.62 ± 2.50 mm,7.04 ± 2.64 mm,8.33 ± 2.64 mm,9.64 ± 2.62 mm.Immediately after theoperation(T2),the HW at the corresponding level was 7.57±2.15 mm,8.65±1.97 mm,9.48±2.08 mm,10.06±2.09 mm,10.74±2.17 mm.After a healing period of average 6months(T3),the HW at 0-4mm level was 6.76±2.21 mm,7.93±1.93 mm,8.95±2.06 mm,9.71±2.14 mm,10.48±2.32 mm.At the time of the last follow-up(T4),the HW at 0-4mm level below the implant shoulder was 6.02±2.03 mm,7.01±2.14 mm,8.39±2.04 mm,9.16±2.09 mm,10.04±2.20 mm.There is a significant difference on the horizontal width at 0-3mm level apical to the implant shoulder between T1 and T2,and T1 and T3(P<0.01).After a long-term follow-up,the horizontal width at 0/1mm level showed a significant reduction when compared to the corresponding level at T2(P<0.05).The augmentation of the HW after simultaneous GBR at 0-4mm level was 3.33±3.05 mm,3.02±2.96 mm,2.46±2.91 mm,1.77±2.35 mm,1.13±1.77 mm.The resorption of the HW at 0-4mm level after a 6-month healing period was 0.82 ± 1.44 mm,0.71 ±1.16 mm,0.53±1.02 mm,0.37±0.97 mm,0.28±1.01 mm.When it comes to the resorption after a long-term follow-up,the reduction of HW at the corresponding level was 1.64±1.54 mm,1.57 ± 1.40 mm,0.97 ± 0.98 mm,0.73 ± 0.81 mm,0.50 ± 0.85 mm.Statistical analysis showed no difference on the resorption between 6-month healing period and long-term follow-up period.Conclusion:Considering the aspects of both measured data and variation of the hard tissue,it can be concluded that the efficacy of horizontal augmentation by simultaneous GBR is considered predictable within the healing period.However,within the limitation of the study,the conclusion of long-term stability of the augmented hard tissue can not be drawn.