Does the implant-abutment interface interfere on marginal bone loss? A systematic review and meta-analysis.

The objective of this systematic review was to compare the conical internal connection (IC) with the external hexagonal connection (EH) on the occurrence of marginal bone loss (ΔMBL). Different databases were used to carry out the selection of the elected studies. The studies were judged according to the risk of bias as "high", "low" and "unclear" risk. For the meta-analysis we included only studies that could extract the data of ΔMBL, survival rate (SR) and probing depth (PD). No statistically significant differences were found for ΔMBL data at one, three- and five-year survival rates between implant connections (p <0.05), however statistically significant differences were found for PD between EH and IC implants (1-year follow-up) -0.53 [95%CI -0.82 to -0.24, p = 0.0004]. This present systematic review demonstrated that there are no significant differences between IC and EH implants for both ΔMBL and SR at 1, 3 e 5 years after functional loading, although better PD values were observed for implants pertaining to the IC connections. Considering the high heterogeneity, more well-delineated, randomized clinical trials should be conducted.

Network meta-analysis of survival rate and complications in implant-supported single crowns with different abutment materials.

OBJECTIVES: To compare the survival rate of abutments, marginal bone loss and peri-implant soft tissue discoloration among implant-supported single crowns with different abutment materials. DATA: Randomized controlled trials (RCTs), controlled clinical trials, and cohort studies of implant-supported single crowns with different dental abutment materials. SOURCES: A systematic search was conducted by an electronic search in 6 databases without restrictions on September 16, 2018, complemented by a manual search. "Grey" literatures were also searched. STUDY SELECTION: Of 3417 studies initially retrieved, thirteen were eligible for inclusion. After studies selected and data extraction, pair-wise and network meta-analyses were performed to analyze the survival rate of the abutment, the marginal bone loss and the soft tissue discoloration. The risk of bias was assessed based on the Cochrane guidelines, Newcastle-Ottawa scale, and funnel plots. Statistical heterogeneity, inconsistencies, and cumulative ranking were also evaluated. RESULTS: Fourteen RCTs and nine non-RCTs were included. No significant differences was detected among titanium (Ti), zirconia (Zr), gold (Au), and alumina (Al) abutments in terms of survival rate (excluding Al < Ti (P < 0.05), marginal bone loss (excluding Zr < Ti (P < 0.05) and Au > Zr (P < 0.05)), or discoloration of peri-implant soft tissue. Additionally, Ti abutment had the highest cumulative ranking of survival rate (97.9%); Al abutment had the lowest marginal bone loss (81.4%) and Zr abutment had the least discoloration of peri-implant soft tissue (84.8%). CONCLUSIONS: Ti abutment has a comparable survival rate with Zr, but better than Al. In addition, Zr abutment has a better effect in maintaining the marginal bone level, compared with Au and Ti. However, there was no difference in the discoloration of peri-implant soft tissue among Au, Ti, and Zr abutment. CLINICAL SIGNIFICANCE: Based on the results of our network meta-analysis, Zr might be a recommended abutment material considering the clinical efficacy of implant-supported single crowns.

Capacity to Maintain Placement Torque at Removal, Single Load-to-Failure, and Stress Concentration of Straight and Angled Abutments.

Because the main complication of implant-supported prostheses is torque loosening and/or fixation screw fracture, the goal of this study was to evaluate the torque before and after fatigue (screw placement and removal, respectively), single load-to-failure (compression test), and stress concentration of straight and angled abutments. Eighty implants were included in polyurethane cylinders. Half of the implants received straight abutments (group S, n = 40) and the other half received angled abutments (group A, n = 40). The abutments for cemented prostheses were installed with a torque of 20 Ncm. Eighty titanium structures were machined and cemented on the abutments with zinc-phosphate cement. After storage for 24 hours, half of the specimens had their torque loosening evaluated and were then immediately submitted to a compressive test in a universal testing machine (1 mm/minute, 1,000 kgf), while the other half were subjected to cyclic fatigue (200 N at 2 Hz for 2 × 106 cycles at 37°C) as an aging protocol (n = 20 from each group). The aged samples then had their torque loosening measured and were also submitted to the compression test. Representative samples were evaluated by scanning electron microscopy. Two bidimensional models similar to the in vitro specimens were created and analyzed using the finite element method to evaluate the stress concentration. Data from the in vitro tests were submitted to two-way analysis of variance and Tukey test, both with significance at P = .5. The results show that angled abutments are less capable of maintaining the installation torque and are less resistant during the single load-to-failure test. The von Mises stress concentration was higher for group A in the cervical region. The straight abutments have better prognosis than angled abutments and less susceptibility to mechanical failures.

Platform switching technique and crestal bone loss around the dental implants: A systematic review.

Background: The overall success of dental implants depends on the crestal bone support around the implants. During the initial years of dental implant placement, the bone loss around the implants determines the success rate of treatment. Platform switching (PLS) concept preserves the crestal bone loss, and this approach should be applied clinically for the overall success of dental implants. Purpose: The purpose of this study is to discuss the literature dealing with the concept of PLS concept and preservation of marginal bone, the mechanism by which it contributes to maintenance of marginal bone, its clinical applications, advantages, and disadvantages, to assess its survival rates. Materials and Methods: PubMed and Google Scholar search was done to find out the studies involving PLS concept from 2005 to 2017. Data were analyzed using SPSS statistical software. Results: Literature search revealed studies involving concepts of PLS, comparison of platform-switched and nonplatform-switched implants, case reports on PLS, and studies with histological and finite element analyses regarding PLS. Conclusion: PLS helps preserve crestal bone around the implants, and this concept should be followed when clinical situations in implant placement permit.

RésuméContexte: Le succès global des implants dentaires dépend du support osseux crestal autour des implants. Au cours des premières années de la pose des implants dentaires, la perte osseuse autour des implants détermine le taux de réussite du traitement. Concept de commutation de plate-forme (PLS) préserve la perte osseuse crestale, et cette approche devrait être appliquée cliniquement pour le succès global des implants dentaires. But: le Le but de cette étude est de discuter de la littérature traitant du concept de concept PLS et de la préservation de l'os marginal, du mécanisme par lequel il contribue au maintien de l'os marginal, ses applications cliniques, ses avantages et ses inconvénients, pour évaluer ses taux de survie. Matériels et méthodes: La recherche PubMed et Google Scholar a été effectuée pour trouver les études impliquant le concept PLS de 2005 à 2017. Les données ont été analysées à l'aide du logiciel statistique SPSS. Résultats: La recherche documentaire a révélé des études impliquant des concepts de PLS, la comparaison de implants à commutation de plates-formes et à commutation de plates-formes, rapports de cas sur PLS et études avec analyses histologiques et d'éléments finis concernant PLS. Conclusion: PLS aide à préserver l'os crestal autour des implants, et ce concept doit être suivi lorsque des situations cliniques dans l'implant permis de placement.

Cytotoxicity of orthodontic temporary anchorage devices on human periodontal ligament fibroblasts in vitro.

Objectives: The objective of this study is to test cytotoxicity of four brands of commercially available orthodontic temporary anchorage devices (TADs). Setting and sample population: Twenty-four (six for each brand, i.e., Aarhus [AO]; Dual top [RMO]; Vector TAS [ORMCO]; and Unitek TAD [3M UNITEK]) TADs were tested. Materials and methods: Twenty-four (six for each brand, i.e., Aarhus [AO]; Dual top [RMO]; Vector TAS [ORMCO]; and Unitek TAD [3M UNITEK]) TADs were individually incubated in complete cell culture medium and shaken at a rate of 1.5 rpm at 37°C for 30 days to extract possible toxic substances in conditioned media (CM). To test cytotoxicity, human periodontal ligament fibroblasts were cultured and exposed to the CM for 24 hr, followed by the examinations of morphological changes, cell viability (MTT assay), and cell damage (lactate dehydrogenase [LDH] assay). Results: No morphological changes were observed in any of the four brands of TADs compared with the negative control. LDH assay showed that none of the four brands of TADs caused significant cell damage after CM treatment compared with the negative control (P > .05). No significant differences were found between any of the four brands of TADs (P > .05). MTT assay showed similar results as did the LDH assay, except for a statistically significant difference found in the TADs from 3M UNITEK compared with the negative control (P = .047). Conclusions: According to the International Standard Organization standards, except for the TAD from 3M, none of the other three brands of commercially available TADs (from AO, RMO, and ORMCO) exhibited significant cytotoxicity, suggesting their safe clinical applications.

Histological and immunohistochemical aspects of the atrophic dental pulp modifications of abutment teeth.

BACKGROUND: Reducing the thickness of hard dental tissues through the preparation of teeth for fixed prosthodontics represents an aggression for the dentin-pulp complex and may cause changes in dental pulp tissues, by means of acute or chronic inflammation, or by asymptomatic, atrophic modifications. AIM: The aim of the study was to histological and immunohistochemical evaluate samples of dental pulp selected from previously prepared teeth, which had been functioning as abutment teeth for some years. PATIENTS, MATERIALS AND METHODS: The starting point of the study was a statistical study conducted on a batch of 276 patients, of which 64 needed to change the fixed prosthetic restorations. Some of the existing abutment teeth were extracted, others presented previously performed root canal treatments and others required endodontic treatment. RESULTS: Of the 21 samples taken, 12 showed atrophic pulp modifications, represented by low cellularity, collagen fibrosis, vascular congestion, and pulpal calcifications. CONCLUSIONS: Certain irreversible atrophic changes can be observed in abutment teeth's pulps, a fact that justifies the need of performing pre-prosthetic endodontic treatment.

Does the implant-abutment interface interfere on marginal bone loss? A systematic review and meta-analysis

Abstract The objective of this systematic review was to compare the conical internal connection (IC) with the external hexagonal connection (EH) on the occurrence of marginal bone loss (ΔMBL). Different databases were used to carry out the selection of the elected studies. The studies were judged according to the risk of bias as "high", "low" and "unclear" risk. For the meta-analysis we included only studies that could extract the data of ΔMBL, survival rate (SR) and probing depth (PD). No statistically significant differences were found for ΔMBL data at one, three- and five-year survival rates between implant connections (p <0.05), however statistically significant differences were found for PD between EH and IC implants (1-year follow-up) -0.53 [95%CI -0.82 to -0.24, p = 0.0004]. This present systematic review demonstrated that there are no significant differences between IC and EH implants for both ΔMBL and SR at 1, 3 e 5 years after functional loading, although better PD values were observed for implants pertaining to the IC connections. Considering the high heterogeneity, more well-delineated, randomized clinical trials should be conducted.

A systematic review of the influence of the implant-abutment connection on the clinical outcomes of ceramic and metal implant abutments supporting fixed implant reconstructions.

OBJECTIVES: The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs). METHODS: An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models. RESULTS: The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments. CONCLUSION: For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.

Biological aspects: Summary and consensus statements of group 2. The 5th EAO Consensus Conference 2018.

OBJECTIVES: This publication reports the EAO Workshop group-2 discussions and consensus statements which provided the scientific evidence on the influence of biological parameters on implant-related clinical outcomes. MATERIAL AND METHODS: The first publication was a systematic review on the biological effects of abutment material on the stability of peri-implant marginal bone levels and the second, a critical narrative review on how peri-implant diagnostic parameters correspond with long-term implant survival and success. The group evaluated the content of both publications, made corrections and recommendations to the authors and agreed on the consensus statements, clinical recommendations and recommendations for future research, which are described in this consensus report. RESULTS: Tested abutment materials can be considered appropriate for clinical use according to the observation period studied (mean 3.5 years). Mean peri-implant bone loss and mean probing pocket depths are not adequate outcomes to study the prevalence of peri-implantitis, while the reporting of frequency distributions is considered more appropriate. CONCLUSIONS: Titanium is currently considered the standard of care as abutment material, although other materials may be more suitable for aesthetic locations. Peri-implantitis should be diagnosed through composite evaluations of peri-implant tissue inflammation and assessment of marginal bone loss with different thresholds.

Randomized controlled clinical study of veneered zirconia abutments for single implant crowns: Clinical, histological, and microbiological outcomes.

OBJECTIVES: To analyze the effect of veneering of the submucosal part of zirconia abutments and the type of retention (cemented vs screw-retained) on clinical, microbiological, and histological outcomes of single-tooth implant crowns. MATERIAL AND METHODS: A total of 44 patients with a single missing tooth to be replaced by an implant in the anterior region participated in the study. Implants were randomly assigned to receive zirconia-based CAD/CAM reconstructions using either one of four treatment modalities: cement-retained with submucosal veneering (CR-P), cement-retained without submucosal veneering (CR-W), screw-retained with submucosal veneering (SR-P), and screw-retained without submucosal veneering (SR-W). Clinical parameters were assessed at baseline (after crown insertion), at 6 and 12 months. Histological and microbiological analyses were performed at 6 months. Descriptive statistics and the Kruskal-Wallis test were applied. RESULTS: The clinical evaluation revealed, in general, stable peri-implant soft tissues with minimal differences for all measured parameters between the four groups, except for bleeding on probing with the two cemented groups exhibiting higher values at 12 months (35.0% ± 26.5% for CR-W and 25.0% ± 38.8% for CR-P versus 13.1 ± 14.8 for SR-W and 13.0 ± 18.2 for SR-P). The descriptive and semi-quantitative histology showed a trend for a higher inflammatory reaction in the two cemented (a medium to high number of inflammatory cells) compared to the screw-retained groups (low number of inflammatory cells) at 6 months. The microbiological test demonstrated low bacterial counts and a similar distribution in between the groups except for two species (Tannerella forsythia and Peptostreptococcus micros) that were found in higher counts in the cemented groups at 6 months. CONCLUSION: Submucosal veneering of zirconia abutments did not negatively affect the health of the peri-implant tissues. The cemented groups, though, did show a clinical and histological trend to higher levels of inflammation.

Diagnostic accuracy of the implant stability quotient in monitoring progressive peri-implant bone loss: An experimental study in dogs.

OBJECTIVES: To investigate the impact of progressive bone loss in an experimental peri-implantitis model in the dog upon the implant stability quotient (ISQ) measured in the course of induced and spontaneous conditions of disease, and to evaluate the association between the clinical parameters and ISQ. MATERIALS AND METHODS: Seventy-two implants were placed in 12 Beagle dogs. Of these, 36 implants in six dogs were assessed during ligature-induced peri-implantitis (three timepoints) and at one timepoint following a period of spontaneous progression. The ISQ was recorded using resonance frequency analysis (RFA). Furthermore, the clinical peri-implant parameters were registered at four sites per implant at each timepoint. Marginal bone loss (MBL) was determined using computed tomography at four sites per implant and bone-to-implant contact (BIC) was assessed from histological samples. A linear regression model was estimated by generalized estimation equations (GEEs) in order to study the MBL-ISQ values at each measurement timepoint. Pearson's correlation test was applied. RESULTS: None of the implants failed during the study period. At implant level, a strong negative correlation was found for all timepoints between ISQ and MBL (r = -0.58; p < 0.001). Accordingly, as follow-up progressed, lower ISQ and higher MBL values were observed. A prediction of MBL depending on the ISQ values and timepoints showed a decrease in one ISQ unit to be related to ~1 mm of MBL. Likewise, a statistically significant correlation was found between BIC and ISQ evaluated after spontaneous chronification of peri-implantitis (r = 0.34; p = 0.04). Nevertheless, the ISQ values failed to correlate to any of the clinical parameters recorded. CONCLUSION: Resonance frequency analysis seems accurate in diagnosing progressive bone loss, as a statistically significant decrease in ISQ was recorded in the course of peri-implant disease. Nevertheless, the clinical relevance of this observation as a diagnostic tool is debatable, since implant stability remains high.

Influence of the abutment height and connection timing in early peri-implant marginal bone changes: A prospective randomized clinical trial.

AIM: The aim of this study was to compare the influence of the abutment height and insertion timing on early marginal bone loss (MBL) in posterior mandibular partial implant-supported restorations. MATERIAL AND METHODS: The study was planned as a prospective, randomized, controlled parallel group including subjects in need of at least two implants for the restoration of an edentulous posterior mandibular area. The patients were allocated into Groups A (implants immediately connected to 2-mm height abutments), B (immediately connected 1-mm height abutments), and C (2-mm abutments were inserted in a second-stage surgery). Each subject was placed in a 1-year follow-up program, including examination assessment of various soft tissue and bone-level parameters. RESULTS: A total of thirty-three patients, including sixty-eight implants, were enrolled in this study. One implant was lost on group C after the first month of healing. A mean MBL change of 0.719 ± 0.361, 0.651 ± 0.379, and 0.754 ± 0.672 mm was computed for groups A, B, and C, respectively, with no significant differences found. The early MBL at T1 was an independent predictor variable for the marginal bone alterations that were assessed at T3 (p < 0.001). CONCLUSION: The first-month MBL variation is a predictor factor of the bone alterations that might occur after 1 year of treatment. The early connection of final prosthetic abutments with distinct heights does not seem to reduce the 1-year MBL rate when compared with traditional treatment protocols.

Histological and micro-CT analysis of peri-implant soft and hard tissue healing on implants with different healing abutments configurations.

OBJECTIVE: The aim of this study was to assess the effect of different abutment configurations on peri-implant soft and hard tissue healing. MATERIALS AND METHODS: Two-piece dental implants, 3.5 mm in diameter and 8 mm in length, were placed in four beagle dogs. Two different transmucosal healing abutment configurations were randomly selected: one with a wide emergence profile (WE) (45° angulation with implant long axis) and the other with a narrow emergence profile (NE) (15° angulation with implant long axis). After four months of healing, the animals were sacrificed. Micro-CT scans were taken for mesio-distal analysis; subsequently, the biopsies were prepared for bucco-lingual histometric analyses. Several measurements were taken using the following reference points: marginal mucosal level (MML), apical barrier epithelium (aBE), implant shoulder (IS), marginal bone crest (BC), and first bone-to-implant contact (fBIC). RESULTS: In the micro-CT analysis, the distance from IS-fBIC was 1.11 ± 0.66 mm for WE and 0.12 ± 0.21 mm for NE (p = 0.004). The IS-BC of WE was -0.54 ± 0.80 mm, whereas NE presented 0.76 ± 0.48 mm (p = 0.002). The histometric analysis showed that both groups presented comparable dimensions of peri-implant biologic width (p > 0.05). However, in the distance from IS to BC, the WE showed a mean distance of -0.66 ± 0.78 mm while NE was 0.06 ± 0.42 mm (p = 0.039); the IS to fBIC was 0.89 ± 0.68 mm for WE while NE was 0.30 ± 0.30 mm (p = 0.041). CONCLUSION: The design of the transmucosal component can influence the establishment of the peri-implant biologic width. The flat and wide emergence profile induced an apical displacement of the peri-implant biologic width and more bone loss.

Effect of different maintenance time of torque application on detorque values of abutment screws in full-arch implant-supported fixed prostheses.

BACKGROUND: The effect of different maintenance time of torque application and screw loosening in full-arch implant-supported prosthesis remains uninvestigated. PURPOSE: To examine the effect of different maintenance time of torque application on detorque values of implant abutment screw in full-arch implant-supported fixed complete denture. MATERIALS AND METHODS: Passively fitting framework supported by four implants stabilized on resin model torqued to 35 N-cm and maintained for different times; instant torque application (protocol A), 10 seconds (protocol B), and 30 seconds (protocol C) were used. Detorque values were recorded during removal of the screws. Comparison between mean torque and detorque values were made using paired sample t-test. The mean removal torque values of each protocol were compared using three-way analysis of variance (ANOVA). RESULTS: The mean removal torque values were lower than the applied torque for all the protocols. The highest mean removal torque value was found in the immediate protocol (A) (24.44 ± 1.7), followed by the 30 seconds protocol (C) (23.37 ± 1.75), and then by the 10 seconds protocol (B) (23.35 ± 1.6). All these differences were found to be statistically significant between torque and detorque values (P = .001). However, the differences among detorque values were not statistically significant (P > .05). CONCLUSION: The application of 35 N-cm for different maintenance time of torque application on implant abutment screw did not appear to affect the detorque value in a multiple implant-supported fixed prosthesis. Maintaining the torque for prolonged time (10 seconds or 30 seconds) was not significantly associated with higher preload than instant torque application in full-arch implant-supported prosthesis.

Fracture resistance and survival of implant-supported, zirconia-based hybrid-abutment crowns: Influence of aging and crown structure.

AIM: The aim of the present study was to investigate fracture resistance of implant-supported zirconia-based crowns (monolayer vs bilayer) cemented to hybrid abutments. METHODS: Monolayer and bilayer zirconia crowns were constructed and cemented to zirconia hybrid abutments. Crowns were divided into two subgroups: (a) untreated control group; and (b) experimental group, which underwent thermal-cycling mechanical loading in a chewing simulator. Up to 1.2 million stress cycles with simultaneous thermocycling (5 and 55°C) were applied. Samples were finally subjected to static load to fracture. Data were analyzed using one-way analysis of variance and t test. Fractured surfaces were observed using scanning electron microscopy. RESULTS: Monolayer zirconia crowns had a 100% survival rate upon completion of the thermal mechanical loading, whereas bilayer zirconia crowns had a 50% survival rate. The fracture load of monolayer zirconia crowns was significantly higher than that of bilayer crowns. Moreover, the fracture load was significantly reduced in monolayer zirconia crowns after aging. Monolayer zirconia crowns showed bulk fracture within the monolayer, while bilayer crowns exhibited cohesive fracture within the veneering porcelain only. CONCLUSIONS: Monolayer implant-supported hybrid-abutment crowns exhibit significantly higher fracture resistance compared to bilayer crowns, making them better suited to handle higher masticatory loads encountered in the posterior region of the mouth.

The micromechanical behavior of implant-abutment connections under a dynamic load protocol.

BACKGROUND: The implant-abutment connection (IAC) is known to be a key factor for the long-term stability of peri-implant tissue. PURPOSE: The aim of the present in vitro study was to detect and measure the mechanical behavior of different IACs by X-ray imaging. MATERIALS AND METHODS: A total of 20 different implant systems with various implant dimensions and IACs (13 conical-, 6 flat-, and 1 gable-like IAC) have been tested using a chewing device simulating dynamic and static loading up to 200 N. Micromovements have been recorded with a high-resolution, high-speed X-ray camera, and gap length and gap width between implant and abutment have been calculated. Furthermore, X-ray video sequences have been recorded to investigate the sealing capacity of different IACs. RESULTS: Out of the 20 implant systems, eight implant systems with a conical IAC showed no measurable gaps under static and dynamic loading (200 N). By contrast, all investigated implant systems with a flat IAC showed measurable gaps under dynamic and static loading. X-ray video sequences revealed that a representative conical IAC had sufficient sealing capacity. CONCLUSION: Within the limits of the present in vitro study, X-ray imaging showed reduced formation of microgaps and consecutive micromovements in implants with conical IAC compared to flat IACs.

The prosthetic abutment height can affect marginal bone loss around dental implants.

BACKGROUND: Marginal bone loss (MBL) is considered an important determinant of implant success, and establishing the peri-implant biological width has been regarded to influence MBL around implants. However, few studies have attempted to show the relationship between the crown/abutment gap and MBL. PURPOSE: To evaluate the effect of the prosthetic abutment height on MBL of dental implants. MATERIALS AND METHODS: This study evaluated data which were retrospectively collected through chart and panoramic radiographs of 145 patients (78 males and 67 females; aged 19 to 79 years, mean age 54.1 years) in whom 273 implants were placed by a single clinician between June 2009 and December 2014. The abutment height and the bone level were measured in digital panorama radiographs. All correlations between abutment height and MBL were analyzed using Spearman's test (P < .05). RESULTS: The 273 implants comprised 126 in 67 female patients and 147 in 78 male patients. The mean age of the patients was 54.1 years (range 19-79 years). The prevalence of MBL and the mean MBL decreased as the abutment height increased. Spearman's test showed a significant negative correlation between abutment height and MBL (P < .05). CONCLUSION: The present study suggests that implants with a higher prosthetic abutment show less MBL, with the abutment height recommended to not exceed 4 mm.

Evaluation of volumetric wear of abutments on the retention loss of ball attachment systems in implant-retained overdentures: An in vitro study.

BACKGROUND: There is a lack of studies evaluating the wear of the male components of the ball attachment systems of implant-retained overdentures. PURPOSE: The purpose of this study was to compare the volumetric wear patterns four commercially used ball abutments. MATERIALS AND METHODS: Forty-eight identical polyethylene and acrylic blocks were fabricated and four groups consisting of 12 polyethylene blocks with two implants and 12 acrylic blocks, which were used as overdentures, were generated (two groups with plastic females, one group with gold and one group with titanium females). Every specimen underwent 5000 insertion and removal cycles (~4.5 years) and retention forces were measured. For the evaluation of volumetric wear, all the ball abutments were scanned before and after the 5000 cycles using a three-dimensional scanner and the data were analyzed using the software supplied by the manufacturer. RESULTS: Statistically significant retention force differences were observed between the groups at each cycle (P < .05). Among the four groups, retention force was lowest in the group with titanium females (5.59 ± 2.27) and highest in the group with gold females (43.0 ± 6.3) at the end of 5000 cycles. Statistically significant dimensional changes in the male components were observed between the groups (P < .05). Volumetric losses were 11%-13% in Group I and II, 1% in Group III, and 25% in Group IV. Group III showed significantly lower volumetric wear whereas Group IV showed significantly higher volumetric wear than all the other groups (P < .001). No significance was detected between Group I and II (P > .05). CONCLUSION: Within the limitations, it can be concluded that although clinical studies are needed to ensure the findings of the present study, due to severe retention loss and volumetric abutment wear, ball attachments with titanium female components should be used with caution.

Biological effect of the abutment material on the stability of peri-implant marginal bone levels: A systematic review and meta-analysis.

OBJECTIVES: The primary aim of this systematic review was to evaluate the available evidence on the effect of the abutment material on the stability and health of the peri-implant hard tissues. METHODS: A protocol was developed to answer the following focused question: "Which is the effect of the abutment material on stability and health of the peri-implant hard tissues?" Randomized controlled trials (RCTs), controlled clinical trials (CCTs) or prospective case series (CS) with at least 6 months of follow-up were included, and meta-analyses were performed to compare abutment materials vs. titanium and to evaluate the impact of various abutment materials on bone changes (primary outcome), probing depth, plaque levels and peri-implant mucosal inflammation. RESULTS: Twenty-nine publications from 33 investigations were included. Results from the meta-analyses demonstrated no significant differences between the different abutment materials when compared to titanium, in regard to the changes in marginal bone levels (MBLs) (n = 15; WMD = 0.034; 95% CI [-0.04, 0.10]; p < 0.339). The meta-analysis reported a significantly greater increase in bleeding on probing for titanium compared to zirconia abutments (n = 3; WMD = -26.96%; 95% CI [-45.00%, -8.92%]; p = 0.003). When evaluating the behaviour of each material different to titanium, there was a significant bone loss over time (n = 31; WMD = 0.261; 95% CI [0.18, 0.35]; p < 0.001) for all the individual materials except for titanium nitride. CONCLUSIONS: This systematic review has shown that the abutment material had minimal impact on marginal bone levels when compared to the standard titanium.

The influence of implant-abutment connection to peri-implant bone loss: A systematic review and meta-analysis.

PURPOSE: Different implant-abutment connections are available and it has been claimed they could have an effect on marginal bone loss. The aim of this review is to establish if implant connection configuration influences peri-implant bone loss (PBL) after functional loading. METHODS: A specific question was formulated according to the Population, Intervention, Control, and Outcome (PICO): Does the type of implant-abutment connection (external, internal, or conical) have an influence on peri-implant bone loss? A PubMed/MEDLINE electronic search was conducted to identify English language publications published in international journals during the last decade (from 2006 to 2016). The search was conducted by using the Medical Subject Headings (MeSH) keywords "dental implants OR dental abutment AND external connection OR internal connection OR conical connection OR Morse Taper." Selected studies were randomized clinical trials and prospective studies; in vitro studies, case reports and retrospective studies were excluded. Titles and abstracts and, in the second phase, full texts, were evaluated autonomously and in duplicate by two reviewers. RESULTS: A total of 1649 articles were found, but only 14 studies met the pre-established inclusion criteria and were considered suitable for meta-analytic analysis. The network meta-analysis (NMA) suggested a significant difference between the external and the conical connections; this was less evident for the internal and conical ones. Platform-switching (PS) seemed to positively affect bone levels, non-regarding the implant-connection it was applied to. CONCLUSIONS: Within the limitations of this systematic review, it can be concluded that crestal bone levels are better maintained in the short-medium term when internal kinds of interface are adopted. In particular, conical connections seem to be more advantageous, showing lower peri-implant bone loss, but further studies are necessary to investigate the efficacy of implant-abutment connection on stability of crestal bone levels.