Effect of using scan body accessories and inter-implant distances on the accuracy of complete arch implant digital impressions: An in vitro study.

PURPOSE: To introduce a novel design for scan body accessory parts that are reusable, easy to attach and detach without permanent change of the scan body, and can be used with different inter-implant distances to enhance the accuracy of complete arch implant scans. MATERIALS AND METHODS: A maxillary polymethylmethacrylate (PMMA) model with a soft tissue replica was fabricated with four implant analogs located at tooth positions 17, 13, 22, and 27 with 18, 25, and 30 mm inter-implant distances. Four scan bodies (SBs) were attached to the implants. The model was scanned with a laboratory scanner to be used as a reference scan. A total of 40 scans were made with the same intraoral scanner and they were divided equally into two groups. Group A: Complete arch implant scans without scan body accessories (n = 20), and Group B: Complete arch implant scans with scan body accessories (n = 20). Intraoral scans were exported and superimposed on the reference scan using reverse engineering inspection software to be evaluated for 3D deviations, angular deviations, and linear deviations. Statistical analysis was performed with student t-test and analysis of variance (ANOVA) with repeated measures followed by post hoc adjusted Bonferroni test. The level of significance was set at P = 0.05. RESULTS: The scan body accessories decreased both the 3D and linear deviations, with a statistically significant difference at SB4 for the 3D deviation (P = 0.043) and the linear inter-implant discrepancies between SB1-SB2 and SB3-SB4 (P = 0.029 and < 0.001), respectively. However, there was no statistically significant difference in angular deviation between the study groups. Implant positions had significant differences within each group. CONCLUSIONS:  A significant improvement in the accuracy of the complete arch implant digital impression was achieved by using the scan body accessories, particularly in reducing the 3D and linear deviations at the most distant implant positions.

Digitization accuracy and scannability of different prosthodontic materials: An in vitro trial.

STATEMENT OF PROBLEM: Digital scanning of different prosthodontic materials is commonplace in contemporary practice. However, the scannability of prosthodontic materials has not been thoroughly investigated. PURPOSE: The purpose of this in vitro study was to evaluate the scanning accuracy and measure the unscanned area in a preset time limit of commonly used framework materials. MATERIAL AND METHODS: A mandibular acrylic resin reference dental typodont with 3 teeth, with the central one prepared for a complete coverage crown, was digitized by using a desktop scanner. A complete coverage crown was generated in standard tessellation language (STL) format. Three groups were created from the digital design according to the crown material: milled polyetheretherketone (PEEK), milled airborne-particle abraded titanium, and milled polymethylmethacrylate (PMMA). They were scanned with the desktop scanner to be used as reference files for each group. The intraoral scanner Medit i700 was used to digitize each specimen 10 times (n=10). Using a nonmetrology grade software program, the deviations between the test STL file of the intraoral scanner and the reference STL file of the desktop scanner were assessed by using the RMS values. The unscanned surface area in a preset time limit of 6 seconds (scannability) was assessed. Groups were compared by using 1-way ANOVA followed by the Tukey post hoc test with Bonferroni correction when the results were significant. All tests were 2-tailed (α=0.05). RESULTS: Regarding deviation analysis, RMS discrepancies were computed, and significant differences in trueness were found (P<.001) among the 3 studied groups. The titanium group had the highest trueness followed by the PEEK and PMMA groups, which were statistically similar (P>.05). Precision differed significantly among the 3 studied groups (P<.001). PEEK was the most precisely scanned material followed by titanium, and the PMMA group had the least precision. Regarding scannability, there were overall significant differences (P<.001). Titanium was the most scannable, followed by PEEK and then PMMA. CONCLUSIONS: Airborne-particle abraded titanium had better trueness and scannability than PEEK and PMMA. However, PEEK was the most precisely scanned material.

Evaluation of the virtual cement gap parameter of different CAD software programs in designing a single crown restoration: An in vitro study.

STATEMENT OF PROBLEM: The accuracy of different virtual cement gap parameters in designing a single crown in a computer-aided design (CAD) software program is still unclear. PURPOSE: The purpose of this in vitro study was to evaluate and compare the virtual cement gap settings of 3 different CAD software programs used to design a single crown restoration. MATERIAL AND METHODS: Three different CAD software programs (exocad, Dental System, and B4D) were evaluated for designing single crowns with similar virtual cement gap settings. Three experimental groups were created based on the CAD software program used (n=10). Three-dimensional analysis software program was used to assess the virtual cement gap in the CAD restoration. The Shapiro-Wilk test of normality was used. Comparisons were carried out by using 1-way ANOVA and the Scheffé post hoc test (α=.05). RESULTS: The Dental System software program had the lowest statistical mean error values at both tooth margin (4.6 µm) and axial wall (1.5 µm), followed by B4D then exocad. At the occlusal surface, the lowest statistical mean error value of 5 µm was achieved by the Dental System followed by exocad then B4D. CONCLUSIONS: Accuracy of the virtual cement gap parameter in single crown design varies based on the CAD software used. The highest accuracy was attained by the Dental System software program at all tooth surfaces, followed by B4D at the tooth margin and axial wall and by exocad at the occlusal surface.

Retention of zirconia crowns to titanium bases with straight versus angled screw access channels: an invitro study.

BACKGROUND: The aim of this study was to assess the impact of abutments with angled screw access channel on the retention of zirconia crowns. METHODS: Seven implant replicas were inserted in epoxy resin blocks. Fourteen zirconia crowns for central incisor tooth were digitally fabricated and cemented to titanium bases (Ti-bases) with resin cement. Titanium bases were categorized into 2 groups (n = 7). Control group (Group STA) included straight screw access channel abutments. Study group (Group ASC) included angled screw access channel abutments. Following aging (5 °C-55 °C, 60 s; 250,000 cycles, 100 N, 1.67 Hz), the pull-off forces (N) were recorded by using retention test (1 mm/min). Types of failure were defined as (Type 1; Adhesive failure when luting agent predominantly remained on the Ti-base surface (> 90%); Type 2; Cohesive failure when luting agent remained on both Ti-base and crown surfaces; and Type 3; Adhesive failure when luting agent predominantly remained on the crown (> 90%). Statistical analysis was conducted by using (IBM SPSS version 28). Normality was checked by using Shapiro Wilk test and Q-Q plots. Independent t-test was then used to analogize the groups. RESULTS: Mean ± standard deviation of retention force records ranged from 1731.57 (63.68) N (group STA) to 1032.29 (89.82) N (group ASC), and there was a statistically significant variation between the 2 groups (P < .05). Failure modes were Type 2 for group STA and Type 3 for group ASC. CONCLUSIONS: The retention of zirconia crowns to abutments with a straight screw access channel is significantly higher than abutments with angled screw access channel.

Navigating the future of guided dental implantology: A scoping review.

BACKGROUND: The aim of this scoping review was to understand the development of robotics and its accuracy in placing dental implants when compared to other forms of guided surgery. METHODS: An electronic search was conducted on the electronic databases of PubMed, Cochrane, and Science direct with the following queries: ((robotics) AND (dental implant)) AND (accuracy). The search timeline was between 2017 and 2022. RESULTS: A total of 54 articles were screened for title and abstract, of which 16 were deemed eligible for inclusion. Thirty-one articles were excluded mainly because they were out of topic (not relevant) or not in English. In total, 16 articles were included for analysis. CONCLUSIONS: This review thoroughly analyses 5 years of literature concerning the evolution of robotics in dental implant surgery, underscoring the necessity for additional research on nascent technologies reported and a comparative study with static and dynamic systems for clinical efficacy evaluation.