A Systematic Review And Meta-Analysis About Titanium Mesh Exposure In Guided Bone Regeneration (GBR) Procedures And A Clinical Retrospective Study About Alteration Of Anterior Maxillary Labial Bone Wall

[Purpose]To investigate whether titanium mesh exposure is influenced by the type of titanium mesh,the type of bone graft material or the associated employment of absorbable membranes.[Materials and methods]Electronic literature searches were conducted using four databases: Pub Med,EMBASE,Web of Science and Cochrane.Articles reporting titanium mesh exposure rates were included,and exposure rates in different subgroups were compared to determine whether a factor significantly influenced titanium mesh exposure.[Results]Twenty and twelve articles were included in the qualitative and quantitative synthesis,respectively.The weighted exposure rates of employing conventional titanium mesh or 3D-customized titanium mesh are 19.9% and 15.2%（p=0.34）.When employing autogenous bone combined with anorganic bovine bone material as bone graft material,the weighted exposure rate was 21.7%,whereas when using other bone graft material,the exposure rate was 23.5%（p=0.74）.The weighted exposure rate of using titanium mesh associated with absorbable membranes is 23.9% while the weighted exposure rate of using titanium mesh without absorbable membranes is 20.2%（p=0.36）.Metaregression showed that when analyzing one factor,the other two confounding factors did not influence the result（p=0.28）.[Conclusions]It seemed that the type of titanium mesh,the type of bone graft material or the combined employment of absorbable membranes did not statistically significantly influence the titanium mesh exposure rate in guided bone regeneration.[Purposes] To investigate the changes of labial bone mass in patients who underwent Guided Bone Regeneration technique in anterior maxillary 2 to 4 years ago,and to explore the factors that may affect the alteration of labial bone mass.[Materials and methods] In cone beam computed tomography（CBCT）images,the implant length was divided into 4 parts from the shoulder to the root,and 5 measurement sites（D1,D2,D3,D4,D5）were obtained.Vertical lines perpendicular to the long axis of the implant were drawn at these sites to obtain the distance between the labial edge of the implant and the outer edge of the labial bone plate.They were defined as horizontal facial alveolar bone thickness（HFBT）.The distance from the shoulder of the implant to the most protrusion point of the labial bone plate crown was defined vertical facial alveolar bone level（VFBL）of the implant.The HFBT and VFBL were measured in CBCT images at three time points: on the day after surgery（T₁）,half a year later（T₂）and 2-4 years later（T₃）.The changes of labial bone thickness and height at different stages（T₃^T₁,T₂^T₁,T₃^T₂）were calculated and defined as △HFBT and △VFBL.The △HFBT and △VFBL were grouped by gender,age,implantation site,timing of implantation,periodontal condition,bone graft material type,barrier membrane type and implant system,and the values between different subgroups were compared to investigate if there is a statistical difference.[Results]Eighty-seven patients,including 38 males and 49 females,were included in the study.Two of the patients had almost no labial bone mass six months after the surgery,so they were excluded in the statistical analysis.A total of 107 implants were included in the statistical analysis.1.VFBL,HFBT₁,HFBT₂ and HFBT₃ decreased significantly from T₁ to T₂（p < 0.05）.HFBT₁,HFBT₂ and HFBT4 were significantly reduced from T₂ to T₃（p < 0.05）.From T₁ to T₃,the bone absorption of HFBT₁,HFBT₂,HFBT₃,HFBT4 and HFBT5 was 0.88 mm,1.14 mm,0.72 mm,0.53 mm and 0.31 mm respectively,and they were all statistically different（p < 0.05）.Bone resorption between T₁ and T₂ was significantly greater than that between T₂ and T₃,and they accounted for the majority of bone resorption after implantation.2.From T₁ to T₃,gender and age did not significantly affect the absorption of the labial bone plate.The lateral incisor group had greater bone resorption than the central incisor group（p < 0.05）.At D1 and D2 sites,there was more resorption in the immediate implantation group than in the delayed implantation group（p < 0.05）.There was no significant difference in bone resorption at all sites between healthy people and the patients whose periodontitis has been effectively controlled.At the D1 site,Dentium bone graft material group had less resorption than Bona bone graft material and Bio-Gene bone meal group（p < 0.05）,and at D2 and D3 sites,Dentium bone graft material had less bone resorption than the Bona bone graft material group（p < 0.05）.When employing titanium meshes with or without absorbable collagen membrane,there was no significant difference in bone resorption（p < 0.05）.And there was also no significant difference among different collagen membranes and implant systems in bone resorption（p < 0.05）.3.From T₁ to T₂,gender had no significant effect on the change of bone height and labial bone thickness.Patients older than 40 years had more bone resorption than younger patients（p < 0.05）.The lateral incisor sites faced more bone resorption than the central incisor sites（p < 0.05）.At the D1 site,the immediate implantation group had more bone resorption than the delayed implantation group（p < 0.05）.And at D2 and D3 sites,patients with periodontitis had more labial bone resorption than healthy people（p < 0.05）.Bona bone graft material was more easily absorbed than other bone graft materials within 6 months after operation.However,there was no significant difference in bone resorption between different collagen membranes and implant systems.4.There was no significant effect on the absorption of labial bone by the single crown or union crown restoration.5.There was no correlation between HFBT₁ and △VFBL（p = 0.02）.There were significant correlations between HFBT₁ and HFBT₂,HFBT 1 and HFBT₃,and low correlations between HFBT₁ and △HFBT（T₃-T₁）,HFBT 1 and △HFBT（T₂-T₁）.[Conclusion] For the patients who underwent GBR in the maxillary anterior area 2 to 4 years ago,obvious horizontal absorption occurred in the labial bone plate of the implant.And the rate of absorption was different.Placement site,timing of implantation and type of bone graft materials may be the possible factors affecting horizontal resorption of labial bone plate within 2 to 4 years after operation.Age,timing of implantation,periodontal condition and type of bone graft materials may be the factors affecting horizontal resorption and placement site may be the factor affecting vertical resorption within 6 months after operation.