THE EFFICACY OF PLATFORM-SWITCHING IN IMPROVING IMPLANT STABILITY.A SYSTEMATIC REVIEW AND META-ANALYSIS

Asmaa Serag Eldien 1 and Marwa Amr Alnawawy 2 . 1. BDS, MSc., Assistant lecturer, 6 of October University, Department of Periodontology. 2. BDS, MSc., Assistant lecturer, Cairo University, Department of Periodontology. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

. Traditionally, a radiographic marginal bone remodeling of 1.5 mm during the first year followed by a radiographic MBL of ≤0.2 mm during each succeeding year is an important parameter for the assessment of implant success (Albrektsson et al. 1986).
Several studies had described three rationale stands behind those of PSI as a biomechanical, biologic, and microbiologic feature (Maeda et al. 2007).
The marginal bone remodeling is related to the micro-gap size and location between implant and abutment, and the rational of using an abutment with a smaller diameter than the diameter of the implant shoulder is to locate it more distant to the first bone-implant contact. The aim of this review was to evaluate MBL radiologically and failure rate of implants inserted in post-extraction sites and restored with or without platform switching protocol after one year of prosthetic loading. 94 Study Selection:-Screening of titles and abstracts was conducted independently by (A.S and M.A); followed by full text screening to check if the studies abide with the pre-set selection criteria which are; patients undergoing dental implant surgery; patients receiving implants with a platform-switching design or regular abutment; articles published in the English language; RCT studies with at least 12 months of follow-up (clinical studies in humans). Any disagreement was solved by discussion between the review authors.

Investigation outcomes:-
The primary outcome was implant survival rates, while the secondary outcome was the post-surgical marginal bone loss (in both platform-switching and regular platform).

Results:-Study Selection:-
The initial electronic search resulted in a total of185 articles (Fig. 1).After screening the titles and abstracts 47 studies were included for further analysis. Reviewing the full text of the remaining articles led to the exclusion of 44 studies. Hand searching did not result in any additional articles. In Table 1 the main characteristics of the 3 included studies.
Quality assessment:-A quality assessment of the methodologies of all included studies was conducted. It was based on the randomized controlled trial checklist of the Cochrane Center, CONSORT guidelines (Fig. 2). The following seven criteria were used: selection bias, allocation bias, performance bias, detection bias, defined inclusion/exclusion criteria, attrition bias and reporting bias. If all of these criteria were fulfilled, the article was classified as a low risk of bias (L). If one or two of these criteria were assessed as high risk of bias or unclear, the study was regarded as a moderate potential .Mean values and standard deviations were extracted from the data. If no standard deviation was available it was recalculated by the formula (SE = SD/√n) with n as the sample size. If there was insufficient data available, the corresponding authors were contacted for providing clarity.
The I 2 statistic was used to assess the heterogeneity between the studies. Because of observed heterogeneity mean differences were combined for continuous data using random effects models meta-analysis (The Cochrane Collaboration, 2012). Study weights were determined by the sample size.  (Pieri et al., 2011). In the latter study, two patients (one in the control group and one in the test group) were excluded due to deviations from the protocol: one was excluded because of intraoperative determination of a need for bone grafting to cover a buccal dehiscence after tooth extraction; and one patient failed to comply with the study protocol (the patient missed designated postoperative appointments).

Secondary outcome:-Marginal bone loss
In this context, the 3 studies showed a statistically significant difference in favor of the use of PS implants for bone preservation (Canullo et al. 2016; Crespi et al. 2009), Pieri et al., 2011)The meta-analysis revealed significant bone loss in the control group compared with the PS group, with a mean difference (MD) of -0.30 mm (95% CI -0.41; -0.19, P < 0.00001 (Fig. 3). The Chi 2 of heterogeneity was 9.44 (P < 0.00001, I 2 = 79%).

Discussion:-
The objective of the current meta-analyses was to analyze MBL changes around immediately placed dental implants. The Third ITI Consensus Conference ( et al. 2004), categorized placement of implants according to the healing time following extraction as: Type 1 immediate (within 24 h of extraction), Type 2 early (4-8 weeks after extraction), Type 3early-delayed (12-16 weeks after extraction) and Type 4 late (more than 6 months) . In this systematic review, the survival rate of Type 1 placements was subject to evaluation.
There are several factors that may affect the outcomes of procedures other than the timing of implant placement. They are either patient-related factors including: the type of the bone; the location and dimension of the edentulous area; the history of oral diseases. Or they could be related to the adopted surgical protocol. . This yielded considerable number of studies that could be combined in a systematic. The main finding of this study was that the level of bone loss with PS implants was significantly lower than that found with the use of RP implants (P < 0.00001). This is in agreement with the systematic review conducted by (

Conclusions:-
Within the limitations of the present systematic review, the additional benefit of platform-switching should not be under estimated. Although the meta-analyses showed significant difference in favor of PS, however, the considerable heterogeneity should be beared in mind when drawing the results on greater population. The language constraints, limiting the included studies to English language, may have caused missing some data that could have 97 added to the body of evidence. Further studies that are properly conducted are recommended for better evaluation of the true tangible effect of platform-switching.

Disclaimer:-
The review authors report no conflict of interest. This study was self-funded Bibliography:-