THE BIOLOGICAL COMPLICATION OF IMPLANT ABUTMENT MATERIALS

e (n = 34 ) ISSN: 2320-5407 Int. J. Adv. Res. 5(12), 445-455 451 Figure(2):Forest plot of comparison implants all ceramic zirconia abutments versus Ti abutments, outcome: Marginal BoneLoss (mm) D . In cl u d ed C . El ig ib ili ty Full-text articles assessed for

446 abutment were used in high esthetic region as an ancillary for metallic abutment (2). In a recent clinical study, In different esthetics situation the zirconium abutment shows high documented performance over titanium abutments (3). brittleness is still the limitation of ceramic materials (4). This property for all ceramic material decrease the resistance to tensile forces. The all ceramic material has high tensile forces which increase the fracture risk of the material for a during function. Whether the fracture toughness of the ceramic is the main cause of fracture (5). zirconia shows the uppermost fracture toughness among all dental ceramics (1). Clinical studies show that supported prosthesis either on teeth supported or on implants supported can be constructed from zirconium frameworks give high clinical performance on function. In the esthetic area after four years of follow up, zirconium implant abutment shows no evidence of fractures (6,7). On the other side, the alumina abutments after 1 year shows 7% fracture of the alumina abutment (8).
Peri-implant alveolar bone loss determined through routine radiographically. which defined as a localized inflammatory lesion relating to alveolar bone loss round to a completely osseointegrated implant supported restoration (9). after at least 10 years of functional loading, many studies have been published (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) observing survival rates of implant supported restoration and concluded that the mean survival rate ranged from 87% to 96%. Implant supported restoration are overwhelmed with biological and mechanical complications despite having high long-term survival rates. (10). The cause of Crestal bone loss may be due to mechanical or biological factors. The common mechanical complication that results from poor prosthetic design, insufficient number of implant, size and position of implant fixture and parafunctional habits of patients is occlusal overloading (11). The clinical drawbacks of inaccurate implant supported restoration range from fractures of abutment screws, prostheses losing, implant fracture and periimplant "marginal bone loss". The main biological cause of alveolar bone loss is microbial pathogens in dental plaque (12).

Aim of Research:-
The goal of this review was to detect the complication of different abutment (all ceramic and metallic) materials of the implant supported restoration regarding the biological complication.

Methods:-
Criteria of studies :-Article types:-All randomized controlled trials (RCTs) & cohort study estimating the effect of different types of implant abutment (metallic or all ceramic abutment) on the alveolar bone loss of implant supported superstructure.
The participante:-People having implant supported restoration affected by bone loss.

Search methods for identification of studies:-Electronic databases searches:-
The resulting inclusion criteria (table 1) were obligatory to: complication of implant supported restoration (biological complication), articles published in English. Case report, case study, invitro study, article in press and animal studies articles were excluded (table2).
To identify the research question, the PubMed database, the Cochrane and ovoid databases were searched electronically. Databases were searched for articles from 2000 through October 2017 using the next (MeSH) terms: (a) dental abutment (b) implants abutment (c) zirconia abutment (d) All ceramic abutment (e) metallic abutment (f)titanium abutment (g) periodontal loss (h) periodontal pocket (i) periodontal pocket index, (j) alveolar bone loss 447 (k) rescission and the combinations . Other applicable non-MeSH words were used in the search to recognize articles showing periodontal inflammatory parameters. These included "yettriastabilized zirconia abutment" "zirconia implant abutment" "inflammation implant abutment" "bleeding index implant abutment" and "periimplant pocket" and "clinical attachment loss around implant abutment." The studies collected after the Missing data Protocol :-Efforts was done to regain missing data from trials authors. and if cross-sectional data were accessible; Change data can be done, the standard deviation "SD" of the changes was to be assessed using the no. within patient correlation, which will give information to the conservative estimate of the SD for change. This technique was described by Follmann (13). To guess the standard error of the difference for split mouth studies, when the proper data were not accessible and could not be found.

Heterogeneity Assessment :-
Cochran"s test for heterogeneity was used to assess the significance of any differences. heterogeneity would have been considered significant if P < 0.1. All 14 included studies results were pooled using the random model effect as statistical heterogeneity among studies was significance where (I4 = 93% P <0.00001).

Results:-
After inclusion criteria regulation, fourteen studies were selected, Included studies tested customized metallic and all ceramic abutments and also provided data on standard all ceramic and metallic abutments (14)(15)(16)(17). All included studies reported a well-defined period of follow-up. Assessment of heterogeneity:any discrepancies in the treatment effects estimation from the different RCTs will be evaluated by the means of Cochran"s test for heterogeneity and heterogeneity, which will have considered significant if P < 0.1. The 14 statistic, which will describes the percentage of the total difference across the trials that is due to heterogeneity other than chance, will be used to compute heterogeneity with 14 over 50% being considered moderate to high heterogeneity. All 10 included studies results were pooled using the random model effect as statistical heterogeneity among studies was significance where (I4 = 93% P <0.00001). The mean difference of MBL which used in this meta-analysis the mean difference of marginal bone loss between all ceramic and titanium abutments for all pooled results were -0.20 (−0.32-0.08) with 95% confidence interval. This overall estimate is statistically significant with P < 0.0009. The meta-analysis was done for the continuous outcome with random effect model, as seen in (Fig. 2). for Zirconia abutments and 2.7 mm for Titanium sites. No significant differences was informed between Zirconia and Titanium abutments in the included studies. The pocket probing depth mean difference which used in this meta-analysis were -0.10 (-0.25-0.05) with 95% confidence interval. This overall evaluation is non-significant statistically with P = 0.18. The meta-analysis with random effect model was made for the continuous outcome as seen in ( Fig. 3) Results of the Effect of metallic and nonmetallic implant abutment on rescission index :-Examination of rescission index around Zirconia and Titanium abutments was reported in four studies. showing mean values at Zirconia abutments ranged from 0 to 0.3 and at Titanium abutments ranged from 0 to 0.4, after 6months the mean of recession index around Zirconia abutment was 0.16 while for titanium abutment was 0.27 (15).later 1 year follow up the mean of recession index around Zirconia abutment was zero while for titanium abutment was 0.04 (12) , furthermore increasing the recession was reported after 2 year follow up for Zirconia to range from 0.3 and was 0.4 for titanium abutment (10),additionally the mean of recession index around Zirconia abutment ranged from 0.1-0.3 whereas for titanium abutment was from 0.3-0.4 after 3y and 5y follow up (8,11) with no significant differences between them .

Results of the Effect of metallic and nonmetallic implant abutment on Pocket
The mean difference of rescission index was -0.09 (-0.20-0.03) with 95% confidence interval. This overall estimate is statistically non-significant with P = 0.13. The meta-analysis with random effect model was made for the continuous outcome of rescission index as seen in (Fig. 4)

Discussion:-
The purpose of this review was to systematically assess the biological complication all ceramic and metallic abutments. The authors in their investigation focused on the biological outcome (pocket depth and recession) . The authors plan was to exclude studies in which abutments were compared to tooth born restoration or any restoration other than implant abutment. So, follow-up ranged from four to eleven years were omitted in several studies (6,11). This action can be claimed; though, patient bias is avoidable through uncontrolled prospective clinical trials. Therefore, the longest follow-up included was 5 years long (10,11). In general, the results of both abutment materials showed only minor statistically significant differences. Evidence-based review assessed the outcome of abutment materials on alveolar bone loss, was drawn in the same decision as previous, (27). Based on visceral, human biology and different clinical studies, abutments materials (zirconia & titanium) showed no difference in effect on alveolar bone stability. The present systematic review shows no significant differences on pocket probing depths between the different abutment materials. On the other hand, it is inspiring to note that van Brakel et al. (21) showed significantly lower pocket probing depth around Zirconium abutments compared to Titanium abutment. This study showed a complete picture of the surface roughness zirconia and titanium implant abutments (Ra-val. 210 Zirconia-236 Titanium nm). New invitro studies (15) showed that the surface roughness of the different abutment materials has a significant role in the performance of cells on Zirconia or Titanium abutment. It was stated that polished Zirconia surfaces, in compression to Titanium surface gives a better adhesion media for attachment cells (22). It could be speculated that decrease pocket probing depth around implant abutment is in deep relation with well adherence of the gingival cells to the abutments. it is hard to evaluate the plaque accumulation influence on the abutment material due to abutment aren"t showing to oral cavity. The included studies didn"t frequent a biological or mechanical complication. The most noticeable complication was noted in two studies (23,24). Remarkably, fistulas triggered by excess cement was documented as one of biological complications, (25,26), So this result was explained by the abutment design. the margin of the superstructure is located subgingival about 1-1.5 mm below gingival crest, implant supported fixed partial denture were cemented using dual cured resin cement on zirconia abutment so due to removal of excess cement which is extremely difficult to be removed as a result biological complication was speculated. So, it is concluded that full removal of excess resin cement is must even if with customized implant abutment. (27). So, it is very difficult to remove an excess of resin cement from the implant abutment (28). Therefore, the idea of this complication is not related to abutment material (titanium or zirconia) but 453 in deep dependent to abutment design and cementation agent. Resin cement remnant was documented to be a probable reason for implant loss in on article (11). The microbial variety and microorganisms number in oral biofilm in relation to different abutment materials reported that the titanium abutment have a high concentration of microorganisms numbers and also biofilm mass. Due to roughness of titanium surfaces which play an important role in microbial adhesion. oppositely, zirconia abutment shows the free energy surface which lead to lower susceptibility for bacterial adhesion. Supporting to the idea of biomaterial property"s play an important role in stress distribution around implant abutment which in sequence affect the alveolar bone loss (15), suggested that higher elastic of modulus for the implant supported superstructure material allowed for a more uniform stress distribution within the implant supported framework, thus providing a more effective and reliable load transfer to the implant fixture. This could clarify that why the all ceramic restorations (high modulus of elasticity) could redistribute the stresses more evenly to the implant fixture when compared to the other restorations. (29). One of the important approach on clinical practice to preserve the soft tissue integrity and improving the peri-implantitis treatment is decreasing bacterial adhesion and consequently biofilm formation on implant abutment surface. However, Different types of implant abutment materials show different opinion for biofilm formation. Titanium and zirconium abutment show hydrophobic activity due to thick peptidoglycan layer that attract immediately the gram-positive bacteria. In the opposite hand gram-negative bacteria will be fend off. although the hydrophobicity of titanium and zirconium abutment play an important role for bacterial adhesion but the bioactive dioxide layer titanium shows semiconductor structures, and this may explain debated results in the systematic literature (22).

Conclusions:-
Although until now all evidence based researches doesn"t give a absolute-cut decision for the use of ceramic or metallic as abutment materials in relative to alveolar bone response, some studies show better mechanical & Biological performance of zirconia abutment over titanium abutment. Regarding meta-analysis zirconia abutments gives statistically significant advantage of over titanium one in developing favorable response of alveolar bone