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Statement of Problem: Screwmentable prostheses were developed to combine the benefits of screw retention and cement retention. However, data are limited on the clinical performance of this type of prosthesis., Purpose: The purpose of this systematic review was to collect scientific evidence on screwmentable prostheses and evaluate their long-term clinical behavior., Material and Methods: An electronic search was conducted by 2 independent reviewers for articles published in scientific dental journals in English from 2004 to April 2020. The search strategy followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inclusion criteria were scientific studies concerning the screwmentable type of prosthesis., Results: The search provided 494 records. Of these, 24 studies fulfilled the inclusion criteria and were included in the review. The included articles presented significant heterogeneity concerning the manufacturing process and the materials used. One randomized clinical trial, 2 prospective clinical studies, 14 in vitro studies, 3 protocol descriptions, 1 case series, and 3 case reports were included., Conclusions: Based on the systematic search of the literature, it is concluded that the screwmentable prosthesis combines advantages of both cement-retained and screw-retained restorations, including passive fit, retrievability, excess cement control, tissue-friendly emergence profile, and improved esthetics. Nevertheless, data from well-designed clinical trials are limited, and further research is required to provide evidence on their long-term clinical behavior., (Copyright © 2021 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: This study aimed to investigate the biological effects of yttria-stabilized zirconia (Y-TZP) compared to other dental implant abutment materials, i.e. lithium disilicate (LS2) and titanium alloy (Ti), as well as the effects of aging of Y-TZP on viability/proliferation and attachment properties of Human Gingival Fibroblasts (HGFs)., Methods: Cylindrical specimens of each material were prepared as per manufacturer's instructions. Y-TZP specimens were divided into three groups: 1. no aging (Zr0), 2. aging for 5 h, 134 °C, 2 bars, 100% humidity (Zr5), 3. aging for 10 h under the same conditions (Zr10). Surface roughness was evaluated by optical profilometry; cell metabolic activity/viability by MTT assay, morphological changes by Scanning Electron Microscopy (SEM) and ratio of live/dead cells by confocal microscopy., Results: Results showed statistically significant reduction of HGF metabolic activity/viability in contact with Y-TZP after aging. Nevertheless, non-aged zirconia showed no significant differences compared with LS2, Ti and control cultures. In contrast, significant stimulation of cell metabolic activity/viability was observed in HGFs exposed to LS2 eluates. Differential morphological patterns were observed for HGF in contact with different materials/treatments, with obviously increased number of dead cells and sparser distribution of HGFs cultured on Zr10 specimens. These effects were not correlated with surface topography, since Y-TZP aging did not alter surface micro-roughness., Significance: These findings indicate that Y-TZP shows comparable biological properties to Ti and LS2 as implant abutment material. Nevertheless, Y-TZP aging might influence gingival cell attachment and proliferation properties, providing an alert to a potentially negative effect on the long-term maintenance of gingival architecture., (Copyright © 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Making implant impressions with different angulations requires a more precise and time-consuming impression technique., Purpose: The purpose of this in vitro study was to compare the accuracy of nonsplinted, splinted, and snap-fit impression techniques of internal connection implants with different angulations., Material and Methods: An experimental device was used to allow a clinical simulation of impression making by means of open and closed tray techniques. Three different impression techniques (nonsplinted, acrylic-resin splinted, and indirect snap-fit) for 6 internal-connected implants at different angulations (0, 15, 25 degrees) were examined using polyether. Impression accuracy was evaluated by measuring the differences in 3-dimensional (3D) position deviations between the implant body/impression coping before the impression procedure and the coping/laboratory analog positioned within the impression, using a coordinate measuring machine. Data were analyzed by 2-way ANOVA. Means were compared with the least significant difference criterion at P<.05., Results: Results showed that at 25 degrees of implant angulation, the highest accuracy was obtained with the splinted technique (mean ±SE: 0.39 ±0.05 mm) and the lowest with the snap-fit technique (0.85 ±0.09 mm); at 15 degrees of angulation, there were no significant differences among splinted (0.22 ±0.04 mm) and nonsplinted technique (0.15 ±0.02 mm) and the lowest accuracy obtained with the snap-fit technique (0.95 ±0.15 mm); and no significant differences were found between nonsplinted and splinted technique at 0 degrees of implant placement., Conclusions: Splinted impression technique exhibited a higher accuracy than the other techniques studied when increased implant angulations at 25 degrees were involved., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Although dental implants exhibit only limited failure rates, their fracture is associated to major modifications of the prosthetic treatment and complex surgery for the removal of the remaining embedded implant part. This investigation aims to assess the developing stress fields in the bone-implant interface during mastication and asses the failure modes of oral implants.In order to achieve this, a FEM model of an implant was reverse engineered and virtually loaded at the top of the crown for a force spectrum ranging from 75-225 N in a vertical, horizontal and oblique occlusal direction. The calculated stress fields were compared with clinically retrieved fractured implants with identical geometrical characteristics and the fracture modes of both cases were correlated. The developing stress patterns facilitated the interpretation of the implant failure as the maximum stresses, indicated critical values in both, lingual and buccal sides of the implant-bone interface at a certain critical level of bone resorption, in which failure occurs.

Purpose: The purpose of this in vitro study was to investigate the effect of impression technique and implant angulation on the impression accuracy of external- and internal-connection implants using a novel experimental device., Materials and Methods: An experimental device was designed and fabricated to make in vitro impressions by means of open- and closed-tray techniques. Impressions of eight implants with two different connections (four external-hex and four internal-hex) at three angulations (0, 15, and 25 degrees) were made using a medium-consistency polyether material. Evaluation of implant impression accuracy was carried out by directly measuring the difference in coordinate values between the implant body/impression coping positioned on the base and the impression coping/laboratory analog positioned in the impression using a touch-probe coordinate measuring machine. Experimental data were analyzed by two-way analysis of variance. The significance level of all hypothesis testing procedures was set at P<.05., Results: The results showed that: (1) for implants with external connections, impression accuracy is not significantly affected by the impression technique, implant angulation, or their interaction; and (2) for implants with internal connections, impression accuracy is significantly affected only by implant angulation: Impression inaccuracy was greater at the 25-degree implant angulation., Conclusions: Within the limitations of this in vitro study, the open- and closed-tray techniques had no effect on the accuracy of multiple implant impressions. The interaction between impression technique and implant angulation was also not significant. However, implant angulation significantly affected the impression accuracy when implants with internal connections were used.