Interproximal contact loss in a retrospective cross-sectional study of 4325 implants: Distribution and incidence and the effect on bone loss and peri-implant soft tissue.

STATEMENT OF PROBLEM: Interproximal contact loss (ICL) is a common finding between implant restorations and teeth, yet few reports have been published on incidence or related complications. PURPOSE: The purpose of this cross-sectional retrospective study was to measure the ICL of 4325 implants, including single and multiple splinted restorations. MATERIAL AND METHODS: Data on 4325 implants were extracted from patient records on ICL, time of follow-up, implant location, and sex of the participant for whom implants were placed in a private practice between 1999 and 2016. Periapical radiographs were used to evaluate the crestal bone level (CBL), whereas peri-implant soft tissues were evaluated with the implant mucosal index (IMI). Measurements (ICL, IMI, and CBL) were evaluated with an average follow-up of 4.5 years (range: 0.25 to 21 years). ICL was assessed in relation to the implant location and sex and grouped by the last clinical recall (1, 2-3, 4-5, 6-7, or 8+ years) to evaluate the effect of time. Data were analyzed by the chi-square test (α=.05). RESULTS: Overall, 17% of implants had ICL, and this significantly increased over time from 11% at 1 year to 29% at ≥8 years (chi-square: 123.8, P<.001). Mandibular implants had more ICL (20%) than maxillary implants (15%) (chi-square: 17.5, P<.001), whereas no difference was found between molar and premolar sites or male and female participants. There was no significant effect of ICL on CBL over time, but there was an increase in inflammation with higher IMI scores at ICL sites. CONCLUSIONS: The incidence of implant ICL was found to be 17%, and ICL was found to increase over time up to 27% at ≥8 years of follow-up. ICL was more common in posterior and mandibular sites. ICL was shown to increase soft tissue inflammation but was not found to affect implant CBLs.

Clinical remounting of complete dentures: A systematic review.

STATEMENT OF PROBLEM: A recent trend has been to reduce the procedural complexity of complete denture fabrication. Whether the clinical remount step is necessary is unclear. PURPOSE: The purpose of this systematic review was to assess the relevance of the clinical remount procedure on complete denture outcomes. MATERIAL AND METHODS: Five electronic databases were searched through to May 2018. The terms "denture*", "dental prosthes*", "equilibrat*", and "remount*" were chosen. The titles and abstracts were screened, and those which met the inclusion criteria were selected for full-text assessment. Studies that only performed the laboratory remount or were not randomized controlled studies were excluded. RESULTS: After duplicate removal, the database search strategy resulted in a total of 226 potential studies. After the titles and abstracts had been screened and the inclusion and exclusion criteria applied, 10 studies were retrieved for full-text assessment. Four randomized controlled clinical studies were included in the systematic review. A meta-analysis could not be performed because of variation in outcome measures after the clinical remount. CONCLUSIONS: A clinical remount for complete dentures is recommended on delivery to reduce clinically observed areas of discomfort and reduce the number of recall appointments. The development of a reliable and valid patient satisfaction questionnaire is necessary to determine conclusively whether the clinical remount also improves patient-perceived satisfaction and mastication.

Performance of zirconia abutments for implant-supported single-tooth crowns in esthetic areas: a retrospective study up to 12-year follow-up.

OBJECTIVE: The aim of this clinical study was to assess complications, success, and survival rates of zirconia abutments from different implant designs. MATERIAL AND METHODS: Anterior implant-supported single-tooth restorations, after 1-12 years of clinical function, were evaluated. One hundred and fifty-eight zirconia implant abutments placed in 141 patients were evaluated. Mechanical complications were observed, such as presence or absence of abutment fractures and loss of retention. In addition, the peri-implant parameters were observed. Statistical analysis was performed using Fisher's exact tests, and bone level was analyzed using the nonparametric Mann-Whitney U-test for non-normally distributed data. RESULTS: Sixteen restorations exhibited different complications. However, no significant difference was observed between the standard and platform switching. The standard platforms exhibited higher marginal bone loss than platform switching design followed up to 5 years. Platform switching has a potentially higher risk of fracture in some designs. In our study, one standard platform as well as two-platform switch designs seem to withstand fracture in the anterior area, regardless of the implant width. Survival and success rates were 93.8% and 81.2% (up to >7 years ≤12), respectively, for standard platform; and 90 and 84% (up to >2 years ≤5), respectively, for platform switching. CONCLUSIONS: In general, standard platform implants restored with zirconia abutments were successful for the longest periods of observation and are a viable treatment alternative in anterior areas. Some of the studied designs of platform switching implants with zirconia abutments performed well for up to 5 years.

In vitro fracture toughness of commercial Y-TZP ceramics: a systematic review.

PURPOSE: The aim of this review was to assess research methods used to determine the fracture toughness of Y-TZP ceramics in order to systematically evaluate the accuracy of each method with regard to potential influencing factors. MATERIALS AND METHODS: Six databases were searched for studies up to April 2013. The terms "tough*," "critical stress intensity factor," "zirconi*," "yttri*," "dent*," "zirconia," "zirconium," and "stress" were searched. Titles and abstracts were screened, and literature that fulfilled the inclusion criteria was selected for a full-text reading. Test conditions with potential influence on fracture toughness were extracted from each study. RESULTS: Ten laboratory studies met the inclusion criteria. There was a significant variation in relation to test method, ambient conditions, applied/indentation load, number of specimens, and geometry and dimension of the specimen. The results were incomparable due to high variability and missing information. Therefore, 10 parameters were listed to be followed to standardize future studies. CONCLUSIONS: A wide variation in research methods affected the fracture toughness reported for Y-TZP ceramics among the selected studies; single-edge-precracked beam and chevron-notched-beam seem to be the most recommended methods to determine Y-TZP fracture toughness; the indentation methods have several limitations. CLINICAL SIGNIFICANCE: The accurate calculation of toughness values is fundamental because overestimating toughness data in a clinical situation can negatively affect the lifetime of the restoration.

In vitro wear behavior of zirconia opposing enamel: a systematic review.

PURPOSE: The aim of this systematic review was to assess enamel wear on teeth opposing zirconia restorations and to evaluate factors related to the wear of natural teeth opposing zirconia restorations. MATERIALS AND METHODS: Five electronic databases were searched through May 2013 without limitations. The terms "antagonist*," "enamel," "wear," and "zirconi*" were used. Titles and abstracts were initially screened, and those that fulfilled the inclusion criteria were selected for a full-text assessment. Studies that evaluated only the material wear were not included. RESULTS: The database search strategy retrieved 142 potentially eligible studies. After the duplicate studies were removed, 62 studies were obtained. Titles and abstracts that fulfilled the inclusion criteria were selected for a full-text assessment (25). Seven laboratory studies met the inclusion criteria. In addition, reference lists from the finally selected studies were also screened. CONCLUSIONS: There was a large variation in relation to wear test method quantification, applied force, lateral movement, number and frequency of cycles, number of specimens, and enamel specimen preparation. In all studies, enamel wear rates were lower against polished zirconia. Differences in the test methods did not allow for comparisons of wear rates among the studies. CLINICAL SIGNIFICANCE: Polishing the surface is recommended for a full-contour zirconia restoration because polished zirconia presents favorable wear behavior opposing natural teeth.

Effect of MDP-Based Primers on the Luting Agent Bond to Y-TZP Ceramic and to Dentin.

PURPOSE: The aim of this study was to evaluate the influence of multimode MDP-based primers and different application protocols on the bond strength of a representative resin cement to an yttrium stabilized tetragonal zirconia (Y-TZP) ceramic. MATERIALS AND METHODS: The occlusal dentin from 60 human molars was exposed. The teeth and zirconia cylinders (N = 60) (3 mm of diameter; 4 mm of height) were divided into six groups (n = 10) according to the ceramic surface conditioning: (1) air abraded with SiO2 particles; (2) Z-Prime Plus; (3) air abraded with SiO2 particles + Z-Prime Plus; (4) air abraded with SiO2 particles + All-Bond Universal; (5) air abraded with SiO2 particles + ScotchBond Universal Adhesive; and (6) untreated zirconia. The luting agent (Duo-Link cement) was applied on the treated dentin surface. Specimens were stored in water (37°C, 24 h) and tested in shear bond strength. Data were statistically analyzed using 2-way ANOVA and Post hoc Tukey tests (α = 0.05). RESULTS: Significant effects of ceramic conditioning were found (p < 0.0001). The specimens sandblasted with silica particles followed by the application of Z-Prime Plus or All-Bond Universal presented greater bond strength values. For the untreated zirconia, several specimens failed prematurely prior to testing. CONCLUSIONS: Sandblasting with silica particles combined with Z-Prime Plus increased the bond strength.

Improving the compatibility of an Y-TZP/porcelain system using a new composite interlayer composition.

The aim of this study was to evaluate the effects of different cooling procedures and a new composite interlayer composition on the flexural strength, and veneer delamination resistance, of an all-ceramic veneered translucent Y-TZP core. One hundred twenty bar-shaped specimens of a translucent Y-TZP ceramic were prepared and divided into three groups: (1) no composite interlayer; (2) a glass interlayer (silica-based glass); (3) a mixed composite interlayer of glass and porcelain veneer material. A veneering porcelain (with and without a composite interlayer) was applied on the specimen surface and sintered. Each core-veneer group was cooled using a rapid or a slow cooling rate. All specimens were tested in four-point bending. Data were statistically analyzed using two-way ANOVA, followed by Post-Hoc tests with Bonferroni correction (α=0.05) and Weibull analysis. The group with no interlayer using the rapid cooling technique exhibited the highest flexural strength. However, with low reliability and the greatest delaminated area of porcelain under tension. A glass interlayer between porcelain veneer and zirconia core presents as a good alternative for maintaining flexural strength and porcelain veneer delamination resistance in zirconia based restorations.

The effect of air-abrasion and heat treatment on the fracture behavior of Y-TZP.

OBJECTIVES: This study evaluated how the flexural strength and fracture behavior of a zirconia-based ceramic (Y-TZP) were affected by pre- and post-sintering mechanical and thermal treatments. METHODS: Treatments included sandblasting with different particle size and type (30µm SiO2; 50 and 110µm Al2O3) and thermal conditioning. Two hundred bar-shaped specimens of pre-sintered Y-TZP ceramic (Lava Frame, 3M) were prepared (specimen dimensions: 25mm length×4mm width×0.7mm thickness) and divided into three groups (before sintering, after sintering and after sintering with heating treatment). The before sintering group specimens were airborne-particle abraded prior to dense sintering. Specimens from the after sintering group were airborne-particle abraded after sintering. The after sintering with heating treatment group specimens were submitted to a heating procedure after airborne-particle abrasion. The controls were the specimens that were sintered and not treated with any conditioning procedures. The specimens from all experimental conditions were analyzed by SEM, CLSM and XRD. All specimens were tested in four-point bending. Data were statistically analyzed using one-way ANOVA and Post Hoc tests (α=0.05). A Weibull analysis was used to analyze the strength reliability. RESULTS: Sandblasting pre-sintered zirconia before sintering significantly decreased the flexural strength, except when the smallest blasting particles were used (30µm SiO2). Phase transformation (t-m) was observed after sandblasting and reverse transformation (m-t) was observed after heating. SIGNIFICANCE: Sandblasting with 30µm SiO2 and 50µm Al2O3 allowed lower phase transformation. However, 30mm SiO2 presented better reliability.