Momen A. Atieh

Platform Switching for Marginal Bone Preservation Around Dental Implants: A Systematic Review and Meta-Analysis

BACKGROUND Platform switching for maintaining peri-implant bone levels has gained popularity among implant manufacturers over the last few years. However, the assumption that the inward shifting of the implant-abutment junction may preserve crestal bone was primarily based on serendipitous finding rather than scientific evidence. The objectives of the present study were to systematically review radiographic marginal bone-level changes and the survival of platform-switched implants compared to conventional platform-matched implants. METHODS A literature search of electronic databases (MEDLINE, EMBASE, The Cochrane Oral Health Groups Trials Register, The Cochrane Central Register of Controlled Trials, the U.K. National Research Register, the Australian New Zealand Clinical Trials Registry, the Database of Abstracts of Reviews of Effectiveness, and Conference Proceedings Citation Index) was performed up to March 15, 2010. Hand searches included several dental journals, and authors were contacted for missing information. Controlled trials that compared marginal bone-level changes around platform-switched dental implants with those restored with platform-matched prostheses were selected. The review and meta-analysis were done according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Data were analyzed using two meta-analytic statistical packages. Mean differences (MDs) were calculated for analyzing continuous data, and risk ratios (RRs) were used for dichotomous data with 95% confidence intervals (CIs). RESULTS Ten studies with 1,239 implants were included. The marginal bone loss around platform-switched implants was significantly less than around platform-matched implants (MD: -0.37; 95% CI: -0.55 to -0.20; P <0.0001). No statistically significant difference was detected for implant failures between the two groups (RR: 0.93; 95% CI: 0.34 to 2.95; P = 0.89). Subgroup analyses showed that an implant-abutment diameter difference > or= 0.4 was associated with a more favorable bone response. CONCLUSIONS The review and meta-analysis show that platform switching may preserve interimplant bone height and soft tissue levels. The degree of marginal bone resorption is inversely related to the extent of the implant-abutment mismatch. Further long-term, well-conducted, randomized controlled studies are needed to confirm the validity of this concept.

The Frequency of Peri-Implant Diseases: A Systematic Review and Meta-Analysis

BACKGROUND The peri-implant diseases, namely peri-implant mucositis and peri-implantitis, have been extensively studied. However, little is known about the true magnitude of the problem, owing mainly to the lack of consistent and definite diagnostic criteria used to describe the condition. The objective of the present review is to systematically estimate the overall frequency of peri-implant diseases in general and high-risk patients. METHODS The systematic review is prepared according to the Meta-analysis of Observational Studies in Epidemiology statement. Studies were searched in four electronic databases, complemented by manual searching. The quality of the studies was assessed according to Strengthening the Reporting of Observational Studies in Epidemiology, and the data were analyzed using statistical software. RESULTS Of 504 studies identified, nine studies with 1,497 participants and 6,283 implants were included. The summary estimates for the frequency of peri-implant mucositis were 63.4% of participants and 30.7% of implants, and those of peri-implantitis were 18.8% of participants and 9.6% of implants. A higher frequency of occurrence of peri-implant diseases was recorded for smokers, with a summary estimate of 36.3%. Supportive periodontal therapy seemed to reduce the rate of occurrence of peri-implant diseases. CONCLUSIONS Peri-implant diseases are not uncommon following implant therapy. Long-term maintenance care for high-risk groups is essential to reduce the risk of peri-implantitis. Informed consent for patients receiving implant treatment must include the need for such maintenance therapy.

Mineral density of hypomineralised enamel

OBJECTIVES To characterize molar-incisor hypomineralisation (MIH) defects of different severities quantitatively and qualitatively using X-ray microtomography (XMT) and to measure the range of reduction in mineral density (MD) of MIH enamel compared with the normal range. METHODS Ten sound teeth and ten MIH teeth were scanned using a commercial XMT system. Four hydroxyapatite phantoms of different densities were used as calibration standards with each scan. A calibration equation derived from the phantoms with each tooth was used for MD calibration. MD was traced from the cementum-enamel junction (CEJ) to the cusp tip and from the dentine-enamel junction (DEJ) to the outer enamel surface. RESULTS In sound teeth, MD increased from CEJ to cusp/incisal tip, while in MIH teeth MD dropped from the CEJ to the occlusal region, then increased again at the cusp tip. MD was highest midway between DEJ and outer enamel in sound teeth. In MIH, enamel showed normal thickness and MD was highest near the DEJ and then decreased towards the outer enamel. MD of MIH enamel was on average about 19% lower than sound enamel. The MIH defects seemed to follow the incremental lines of enamel formation. CONCLUSIONS MIH defects are hypomineralised defects of different severities that follow the natural incremental lines of enamel formation. Cuspal areas are usually only mildly affected and cervical enamel always appears to be sound.

Diagnostic accuracy of panoramic radiography in determining relationship between inferior alveolar nerve and mandibular third molar

PURPOSE The aim of this review was to determine the diagnostic accuracy of panoramic radiographic markers in the detection of the relationship between the mandibular canal and third molar roots. MATERIALS AND METHODS A literature search of electronic databases, Cochrane Oral Health Groups Trials Register, National Research Register, conference proceedings, and abstracts was performed to identify studies that had investigated the diagnostic accuracy of the 3 panoramic radiographic markers (ie, darkening of the root, interruption of the radiopaque borders, and diversion of the mandibular canal). RevMan, version 5.0, and Meta-DiSc software programs were used for the pooled analyses and the construction of a summary receiver operating characteristic curve. RESULTS A total of 5 studies were included, involving 894 observations. The overall pooled sensitivity and specificity for darkening of the root was calculated as 51.2% (95% confidence interval [CI] 42% to 60%) and 89% (95% CI 87% to 90%), respectively. The interruption of radiopaque borders showed a pooled sensitivity of 53.5% (95% CI 78.1% to 81.8%) and a pooled specificity of 80% (95% CI 78.1% to 81.8%). The diversion of the canal criterion had a pooled sensitivity of 29.4% (95% CI 21.8% to 38.1%) and a pooled specificity of 94.7% (95% CI 93.6% to 95.7%). The area under the receiver operating characteristic curve was 70% to 77%. CONCLUSIONS The results of this meta-analysis suggest a reasonable diagnostic accuracy for panoramic radiography in the preoperative evaluation of the relationship between third molars and the canal. Additional studies are needed to examine a more accurate, accessible, and cost-effective initial radiographic technique before third molar surgery.

Immediate restoration/loading of immediately placed single implants: is it an effective bimodal approach?

OBJECTIVE To compare systematically the survival and radiographic marginal bone level changes of two immediate implant protocols in the aesthetic region; immediate single implant restoration/loading in extraction sockets (the bimodal approach) compared with the same in healed sites. MATERIAL AND METHODS A literature search of electronic databases, Cochrane Oral Health Groups Trials Register, National Research Register, conference proceedings and abstracts was performed without language restriction up to 1 August 2008. Hand searching included several dental journals and authors were contacted for missing information. Controlled trials that compared immediate restoration/loading of single implants placed in extraction sites with those placed in healed sites were selected. The meta-analysis was prepared according to the guidelines of the Quality of Reporting of Meta-analyses statement. The data were analysed using RevMan version 5.0 software. A fixed effects model was chosen with standardized mean differences for continuous data, and risk ratios for dichotomous data with 95% confidence intervals. RESULTS Ten studies with 629 implants were included. Immediate single implant restoration/loading in extraction sockets in the aesthetic zone was associated with significantly higher risk of implant failure (risk ratio of 3.62, 95% confidence interval 1.15-11.45, P=0.03). However, the bimodal approach showed favourable marginal bone changes after 1 year. CONCLUSION The review and meta-analysis supported the potential advantages offered by this bimodal approach, but indicated a higher risk when compared with immediate restoration/loading in healed ridges. Further long-term, well-conducted, randomized-controlled studies are needed to confirm the validity of this treatment option.

Ceramic implants (Y-TZP): are they a viable alternative to titanium implants for the support of overdentures? A randomized clinical trial.

OBJECTIVE The objective of this study was to assess 1-year clinical success of one-piece zirconia implants compared with similar-design titanium implants, in the context of a novel protocol for implant distribution. MATERIALS AND METHODS Twenty-four edentulous participants were randomly allocated to one-piece titanium or zirconia implant group. Each participant received four implants in the maxilla (mid-palatal and three anterior crestal implants) and three implants in the mandible (mid-symphyseal and two bilateral distal implants). Conventional loading protocol was followed. Marginal bone remodeling and clinical success of implants were evaluated. The data were statistically analyzed, and risk predictors for implant failures were evaluated. RESULTS There was no significant difference in the survival rate between the two groups. In the mandible, the survival rate of titanium implants was 95.8% vs. 90.9% for the zirconia implants. The corresponding values in the maxilla were 71.9% and 55%, respectively. Three implants in the zirconia group fractured. Statistically significant less marginal bone loss was observed around titanium implants (0.18 mm) compared with the zirconia group (0.42 mm). The prediction model revealed a higher risk for implant failures in the maxilla (P < 0.0001). CONCLUSION The outcome of this study indicates caution before recommendation can be made for the use of single-piece zirconia implants for overdenture support. Their use should be limited to cases with proven allergy to titanium. This is mainly due to the increased bone loss and higher fracture rate observed for zirconia implants. Future biomaterial research should focus on producing surface characteristics on zirconia implants with outcomes similar to those established for the optimum osseointegration of titanium implants.

Loading protocols for mandibular implant overdentures: a systematic review with meta-analysis.

BACKGROUND Mandibular overdentures are a successful treatment option for the edentulous patients with long-term predictable outcomes, using conventional loading protocols. Currently, both early and immediate loading protocols for mandibular implant overdentures are prevalent in the literature. PURPOSE A systematic review and meta-analysis of the current published literature on comparative studies using conventional versus either early and/or immediate loading protocols for mandibular implant overdentures. MATERIALS AND METHODS The review was carried out in accordance with the QUOROM (Quality of Reporting of Meta-Analyses) guidelines. The PICO (Population, Intervention, Comparisons, Outcomes) format was used in conjunction with predefined inclusion criteria. A literature search of PubMed (1969-October 2008), EMBASE (1998-October 2008), the Cochrane Database of Systematic Reviews, and the Cochrane Controlled Trial Register was conducted. In addition, hand searching through refereed dental journals was also performed for the years 2000 to 2008. The meta-analysis was conducted by using the MIX software v.1.7 (Kitasato Clinical Research Center, Kanagawa, Japan). RESULTS A total of 191 studies were identified through the electronic search. After full-text screening and cross-matching with the predefined inclusion criteria, only 10 studies with a minimum follow-up of 2 years were eligible for inclusion in this review. Of the 10 included studies, seven have compared the outcome of conventional versus early loading of implants supporting mandibular overdentures. The remaining three studies, on the other hand, compared the outcome of conventional versus immediate loading. The meta-analysis revealed no significant difference in the outcome between conventional and either early (p = .72) or immediate (p = .08) loading of implants supporting mandibular implant overdentures. CONCLUSIONS Short-term outcomes of early or immediate loading protocols for mandibular implant overdentures achieved comparable success to conventional loading ones. No evidence was found of long-term studies to support or refute either early or immediate loading protocols for mandibular implant overdentures.

An overview of systematic reviews on the effectiveness of periodontal treatment to improve glycaemic control.

Several systematic reviews with meta-analyses on the effectiveness of periodontal treatment to improve glycaemic control have been published. So far no overview of these systematic reviews has been performed. The main objective of this report was to assess critically these systematic reviews to provide the reader with a high-level synthesis of research evidence. MEDLINE (via PubMed) and EMBASE databases were searched independently and in duplicate to identify systematic reviews with meta-analyses of clinical studies that assessed the relationship between diabetes mellitus and periodontitis. The last database search was performed on 10 March 2015. The reference lists of included systematic reviews were also scrutinized for further publications. The methodological quality of the included systematic reviews was assessed independently with two validated checklists (AMSTAR and OQAQ) by two authors. Disagreements in the assessment were resolved by consensus. A total of 226 potential publications were initially retrieved. Eleven systematic reviews with meta-analyses were finally included. Glycosylated haemoglobin A1c (HbA1c) was the most commonly used clinical endpoint. Meta-analytic estimates from systematic reviews generated an average reduction of 0.46% (median 0.40%) of HbA1c in patients with diabetes mellitus who received periodontal treatment. These meta-analyses had, nevertheless, methodological limitations such as inclusion of trials with different types of risk of bias that hinder more robust conclusions. A recent meta-analysis that included recently published large randomized controlled trials did not show significant change in the level of HbA1c at the 6 mo follow-up. The AMSTAR checklist generated results that were more conservative than OQAQ. Findings from this overview do not support the information that periodontal treatment may improve glycaemic control. Methodological issues described in this overview may guide further research on this topic.

Xenogeneic collagen matrix for periodontal plastic surgery procedures: a systematic review and meta-analysis.

Several clinical trials describe the effectiveness of xenogeneic collagen matrix (XCM) as an alternative option to surgical mucogingival procedures for the treatment of marginal tissue recession and augmentation of insufficient zones of keratinized tissue (KT). The aim of this systematic review and meta-analysis was to evaluate the clinical and patient-centred outcomes of XCM compared to other mucogingival procedures. Applying guidelines of the Preferred Reporting Items for Systematic Reviews and Meta analyses statement, randomized controlled trials were searched for in electronic databases and complemented by hand searching. The risk of bias was assessed using the Cochrane Collaborations Risk of Bias tool and data were analysed using statistical software. A total of 645 studies were identified, of which, six trials were included with 487 mucogingival defects in 170 participants. Overall meta-analysis showed that connective tissue graft (CTG) in conjunction with the coronally advanced flap (CAF) had a significantly higher percentage of complete/mean root coverage and mean recession reduction than XCM. Insufficient evidence was found to determine any significant differences in width of KT between XCM and CTG. The XCM had a significantly higher mean root coverage, recession reduction and gain in KT compared to CAF alone. No significant differences in patients aesthetic satisfaction were found between XCM and CTG, except for postoperative morbidity in favour of XCM. Operating time was significantly reduced with the use of XCM compared with CTG but not with CAF alone. There is no evidence to demonstrate the effectiveness of XCM in achieving greater root coverage, recession reduction and gain in KT compared to CTG plus CAF. Superior short-term results in treating root coverage compared with CAF alone are possible. There is limited evidence that XCM may improve aesthetic satisfaction, reduce postoperative morbidity and shorten the operating time. Further long-term randomized controlled trials are required to endorse the supposed advantages of XCM.

Evaluation of optimal taper of immediately loaded wide-diameter implants: a finite element analysis.

This study aimed to evaluate the effects of different tapering angles of an immediately loaded wide-diameter implant on the stress/strain distribution in bone and implant after implant insertion in healed or fresh molar extraction sockets. A total of 10 finite element (FE) implant-bone models, including 8.1-mm diameter implant, superstructure, and mandibular molar segment, were created to investigate the biomechanical behavior of different implant taper angles in immediate and delayed placement conditions. The degrees of implant taper ranged from 2° to 14°, and the contact conditions between the immediately loaded implants and bone were set with frictional coefficients (μ) of 0.3 in the healed models and 0.1 in the extracted models. Vertical and lateral loading forces of 189.5 N were applied in all models. Regardless of the degree of implant tapering, immediate loading of wide-diameter implants placed in molar extraction sockets generated higher stress/strain levels than implants placed in healed sockets. In all models, the von Mises stresses and strains at the implant surfaces, cortical bone, and cancellous bone increased with the increasing taper angle of the implant body, except for the buccal cancellous bone in the healed models. The maximum von Mises strains were highly concentrated on the buccal cortical struts in the extracted models and around the implant neck in the healed models. The maximum von Mises stresses on the implant threads were more concentrated in the non-tapered coronal part of the 11° and 14° tapered implants, particularly in the healed models, while the stresses were more evenly dissipated along the implant threads in other models. Under immediate loading conditions, the present study indicates that minimally tapered implants generate the most favorable stress and strain distribution patterns in extracted and healed molar sites.