Marginal Accuracy of Lithium Disilicate Full-Coverage Single Crowns Made by Direct and Indirect Digital or Conventional Workflows: A Systematic Review and Meta-Analysis.

PURPOSE: Several studies have compared digital intraoral scanners and conventional impressions. The accuracy of these two methods in terms of marginal accuracy of lithium disilicate crowns is not well-established, yet. The purpose of this study was to systematically review available publications on marginal fit of single-unit, full-coverage, tooth-supported lithium disilicate restorations. METHODS: Pubmed, Web of Science, Cochrane, EMBASE, and Scopus were electronically searched along with a manual search. After critical appraisal, data from selected studies were extracted and mean marginal difference with a 95% confidence interval was calculated. Meta-analysis of the collected data was conducted using STATA software. RESULTS: The meta-analysis revealed similar marginal gap values in intraoral scanners with conventional groups (p>0.05) and in intraoral scanners with extraoral canners (p>0.05). CONCLUSION: No significant difference was seen between digital and conventional impressions or intra- and extraoral scanners for marginal accuracy of lithium disilicate crowns.

Marginal adaptation of zirconia complete-coverage fixed dental restorations made from digital scans or conventional impressions: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Intraoral scanners have been increasingly used in recent years. However, the accuracy of digital scans as it affects marginal adaptation is unclear. PURPOSE: The purpose of this systematic review and meta-analysis was to compare the marginal adaptation of single-unit zirconia crowns fabricated with digital scans or with conventional impressions. MATERIAL AND METHODS: The electronic databases PubMed (MEDLINE), Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science (ISI), Scopus, and EMBASE were searched and complemented by a manual search. Risks of bias were assessed by using a modified methodological index for nonrandomized studies (MINORS). Mean ±standard deviation (SD) values of marginal accuracy of studies were extracted for both methods. Mean marginal difference and 95% confidence interval (CI) were calculated to evaluate the marginal accuracy of each method. Pooled data were statistically analyzed by using a random-effect model. RESULTS: Seventeen studies were used to perform the meta-analysis. Subgroup analysis was performed based on intraoral scanners. Standardized mean marginal difference and 95% CI of each subgroup were as follows: Lava: -0.85 µm (95% CI: -1.67, -0.03) (P=.043); CEREC: -1.32 µm (95% CI: -2.06, -0.59) (P<.001); iTero: -0.44 µm (95% CI: -1.35, 0.47) (P=.338); TRIOS: -1.26 µm (95% CI: -2.02, -0.51) (P=.001); unknown scanner: -0.21 µm (95% CI: -1.14, 0.72); all studies: -0.89 µm (95% CI: -1.24, -0.54) (P<.001). CONCLUSIONS: Digital scanning of prepared teeth for single-unit zirconia restorations resulted in better marginal accuracy than conventional techniques using elastomeric impression materials.

Relation of CAD/CAM zirconia dental implant abutments with periodontal health and final aesthetic aspects; A systematic review.

Background: Using dental implants to replacing missing teeth and satisfy both functional and aesthetic needs is one of the mainstream dental treatments. New approaches including computer-aided design and computer-assisted manufacture (CAD/CAM) have been introduced to improve these elements. This systematic review aimed to compare CAD/CAM zirconia (Zr) implant abutments with other available abutments in terms of peri-implant health and aesthetics. Material and Methods: Five electronic databases (PubMed, Web of Science, Scopus, ProQuest, and Embase) were scoured for clinical studies evaluating Zr abutments reporting on the outcomes of interest including interproximal papilla stability (PS), papilla recession (REC), pink and white esthetic score (PES, WES), marginal bone level (MBL), color, and soft tissue contour. A hand searches in English language journals until September 2020 complemented the search. Two tools of Joanna Briggs Institute and Jaded Score calculation were used for the risk of bias assessment. No quantitative synthesis of the data was done due to high heterogeneity. Results: A total of six studies from the 412 ones obtained from the search were included. The study designs were either prospective cohort (n=3) or randomized clinical trial (n=3). Papilla fill, WES, PES, and the distance from the bone crest of adjacent teeth to the contact point (CPB) and inter-tooth-implant distance (ITD) was not significantly different between Zr CAD/CAM and Zr stock abutments. However, soft tissue stability and REC index were better in Zr CAD/CAM abutments. Conclusions: Higher soft tissue stability can be achieved for Zr compared to titanium abutments with either stock or CAD/CAM abutments. Key words:Dental implants, Dental abutment, Computer-Assisted Design, Computer-Aided Manufacturing, Zirconia abutment, Soft tissue stability.

Internal and Marginal Fit Accuracy of Pre-sintered CAD/CAM Implant-Supported Frameworks Before and After Porcelain Layering.

PURPOSE: Internal and marginal fit accuracy of an implant-supported fixed partial denture (I-FPD) along with passive fit are required for long-term clinical success. This study compared the fit accuracy of three-unit CAD/CAM-fabricated cementretained I-FPDs milled from pre-sintered cobalt-chromium (Co-Cr) and zirconia (Zr) and evaluated the effect of applying porcelain. MATERIALS AND METHODS: Two implant analogs were positioned parallel at first premolar and first molar sites in an acrylic model. Their corresponding abutments were tightened with 25-Ncm torque force. Four groups were designed: two groups of I-FPD frameworks with pre-sintered Zr (ZrF) and soft millable Co-Cr alloy (SF) blocks, and two groups by applying porcelain to the Co-Cr (SP) and Zr (ZrP) frameworks (n = 4 in each group). Absolute marginal gap (AMG), marginal gap (MG), and internal discrepancies were measured. Kolmogorov-Smirnov, Levene, one-way analysis of variance (ANOVA), and Scheffe tests were used for statistical analysis using SPSS software version 22 at a significance level of .05. RESULTS: All measured criteria were significantly different from each other (all P values < .001). The rankings from the lowest gap to the highest gap for the main criteria were as follows: MG: SF < SP < ZrF < ZrP; AMG and internal discrepancies: SF < SP < ZrP < ZrF. Comparing molars and premolars, molars had smaller MGs, larger internal discrepancies, and smaller AMG in ZrP but larger AMG in SP. CONCLUSION: All three-unit CAD/CAM-fabricated cement-retained I-FPDs were in the clinically acceptable range of fit accuracy. The lowest and highest misfit values were observed in the SF and ZrF groups, respectively.

Laser Treatment of Fiber Post and Final Push-Out Bond Strength: A Systematic Review and Meta-Analysis.

Purpose: This review article tries to answer this question: "What are the effects of laser surface treatment of fiber posts (FPs), compared with other surface roughening methods, on bond strength of cemented FPs?" Methods: Search was carried out in six electronic databases by focusing on defined key words. Related titles and abstracts, up to March 2019, were collected, read, and selected for quality assessments. A total of 2408 articles were included in the study at the initial stage of the searching phase. Results: Finally, seven studies were recognized to be reliable to be reviewed and meta data analysis in the study. All the studies were in vitro with a total of 340 samples. None of the Er:YAG (-0.27, 95% CI: -2.29 to 1.76; p = 0.79) and Er,Cr:YSGG (-0.04, 95% CI: -1.43 to 1.35; p = 0.95) treated samples showed any significant overall mean differences in final push-out bond strength (PBS) compared with the control groups. Conclusions: Laser pretreatment of FP surfaces might not be effective in providing high PBS. FP surface are susceptible to damage of high-level laser irradiation and might show decreased bond strength.

A Comparison of implant impression precision: Different materials and techniques.

BACKGROUND: Precision of implant impressions is a prerequisite for long-term success of implant supported prostheses. Impression materials and impression techniques are two important factors that impression precision relies on. MATERIAL AND METHODS: A model of edentulous maxilla containing four implants inserted by All-on-4 guide was constructed. Seventy two impressions using polyether (PE), polyvinyl siloxane (PVS), and vinyl siloxanether (VSE) materials with direct and indirect techniques were made (n=12). Coordinates of implants in casts were measured using coordinate measuring machine (CMM). Data were analyzed with ANOVA; t-test and Tukey test were used for post hoc. RESULTS: With two-way ANOVA, mean values of linear displacements of implants were significantly different among materials and techniques. One-way ANOVA and Tukey showed significant difference between PE and VSE (P=0.019), PE and PVS (P=0.002) in direct technique, and between PVS and PE (P<0.001), PVS and VSE (P<0.001) in indirect technique. One-way ANOVA and t-test showed significant difference between the two techniques in PVS groups (P<0.001) and in PE groups (P=0.02). Two-way ANOVA showed mean values of rotational displacement of implants were significantly different among materials. One-way ANOVA and Tukey test showed significant difference between PVS and PE (P=0.001) and between PVS and VSE (P=0.012) in indirect groups. CONCLUSIONS: On the basis of the results, when deciding on the material to make an impression of implants, PE is recommended for direct technique while PE and VSE are recommended for indirect technique. Recommended technique for VSE is either direct or indirect; and for PE and PVS is direct. Key words:Polyvinyl siloxane, polyether, vinyl siloxanether, direct technique, indirect technique, All-on-4, coordinate measuring machine.