Effect Evaluation Of Implant-Abutment Junction Of Platform Switching

Objective: 1.In order to assess clinical effect of platform switching and platform matching of implant-abutment junction by means of Metaanalysis,which include clinical survival rate,marginal bone loss and periodontal related index.2.Discussion of stress distribution on implant-bone interface of platform matching and platform switching,as well as stress distribution of different kinds of platform width and implant embedded depth,which using the method of biomechanics analysis.It is to provide theoretical reference for the selection of clinical design and application.Methods: 1.Meta-analysis: A literature search of Pubmed,EBSCO,Elsevier,Ovid,CNKI,CBM,Wanfang and VIP databases from inception to February 31,2015 was conducted to collected the randomized controlled trials(RCT)and clinical case-control trials(CCT)about the studies.Manual search was performed among Chinese Journal of Stomatology,West China Journal of Stomatology,Journal of Practical Stomatology,Journal of Oral Science Research.According to include and exclude standards,two professional training of reviewers independently screened the literature,evaluated the quality of the screened literatures,and used Revman5.3.0 to make the Meta-analysis and used the GRADEprofiler3.6.1 to assess the quality of the evidence.2.Three-dimensional finite element analysis:⑴Using PROE Wildfire5.3.0 software to establish abutment of 3.8×6mm and trapezoidal bone block,whose length of 12 mm,width of 12 mm,buccolingual diameter of 12 mm on the top and of 14 mm on the bottom,height of 16.5mm,which cortical bone thickness is 1.5mm.According to the shape parameters of the GLOBAL implant system,establishing implants of 3.8×11mm,4.3×11mm,4.8×11mm,5.5×11mm.10 models were assembled as format of IGES,which IAJ of platform matching was at crestal,while IAJ of platform switching located at crestal,sub-crestal 0.5mm,subcrestal 1mm respectively.⑵Importing models to ANSYS WORKBENCH 15.0,setting material parameters,contact way,boundary constraints and load,recording and analyzing the change rule of Von Mises stress distribution and peak value on implant-bone interface.Result:1.Eventually 41 articles are incorporated,29 randomized controlled trial(RCT)and 12 clinical controlled trials(CCTS),which includes a total of 3594 implants.Results of Meta-analysis: ⑴ Survival rate of implant OR=1.33 [95%CI(0.70,2.53),P=0.38 ].⑵ Marginal bone loss SMD =-1.57 [95%CI(-1.99,-1.15),P<0.001].⑶ Periodontal pocket depth MD=-0.22 [95%CI(-0.32,-0.12),P<0.001].⑷ Bleeding index MD=0.04 [95%CI(-0.06,0.14),P=0.43].⑸ Gingival index MD=-0.01[95%CI(-0.08,0.06),P=0.78].⑹ Plaque index MD=-0.01[95%CI(-0.04,0.07),P=0.69].⑺ When quality of the evidence is graded using "GRADEprofiler3.6.1" software,there is two category that is high,two is moderate and three is low,while other is very low in the GRADE system for grading evidence.2.⑴ Under loads of vertical and buccolingual direction,the Von Mises stress-peak of models are located in the contact between the neck area of cortical bone and implant,while of cancellous bone is smaller,mainly concentrated in the neck and root tip position.Von Mises stresspeak value of cortical bone of platform matching is greater than platform switching.⑵ Under different conditions of load,Von Mises stress-peak value of cortical bone and cancellous bone decrease gradually with the increase of platform width whether IAJ is at crestal or sub-crestal 0.5mm or sub-crestal 1mm.⑶Under different conditions of load,Von Mises stresspeak of cortical bone is at crestal> sub-crestal 1mm>sub-crestal 0.5mm whether platform width is 0.25 mm or 0.5 mm or 0.85 mm.Von Mises stress-peak of cancellous bone is at sub-crestal 0.5mm> sub-crestal 1mm>crestal.Conclusion:1.Platform switching has an advantage over preserving implant marginal bone,forming a shallow depth of periodontal pocket,which is compared with platform matching.2.Von Mises stress-peak of implant-bone interface of platform switching is much smaller than which of platform matching.Increase of platform width with diameter of implant increasing can achieve function of optimizing stress distribution of alveolar ridge.So in order to reduce Von Mises stress-peak of alveolar ridge,large diameter of implant should be chosen if there is enough bone volume.3.With the increase of platform switching implant embedded depth,cortical bone’s Von Mises stress-peak rises after falling.It suggests that implant embedded level could be controlled according to the type of bone in order to ensure that implant is surrounded by enough of cortical bone in clinical operation.