Trueness of digital implant impressions based on implant angulation and scan body materials

Effects of implant angulation on digital implant impression accuracy remain controversial. Therefore, this in vitro study aimed to compare the digital implant impression trueness among models with different implant angulations and scan body materials. Six partially edentulous mandibular models with dental implants on the right second premolar and second molar areas were categorized according to the implant angulation of the distal implant (parallel, or 15° mesially or lingually tilted compared to the mesial implant) and scan body materials (polyetheretherketone or titanium). After scanning each model with intraoral scanners, the root mean square and within-tolerance values were calculated with respect to the reference, and nonparametric statistical tests were performed (α = .05). Scan data from models with the mesially tilted distal implant showed better trueness than the corresponding parallel and lingually tilted groups in terms of root mean square values (p < .017). The root mean square value in the titanium scan body group was lower than that in the polyetheretherketone scan body group (p < .001). However, the percentage within a tolerance of ± .1 mm was higher in the polyetheretherketone scan body group than in the titanium scan body group (p = .001). Intraoral scan data of models where the terminal implant was mesially tilted showed better trueness.

Can transfer type and implant angulation affect impression accuracy? A 3D in vitro evaluation

Impression accuracy is fundamental to achieve a passive fit between implants and the superstructure. Three transfer types were tested to evaluate the differences in impression accuracy and their efficiency in case of different implant angles. A master model with four implant analogues placed at 0°, 15° and 35° was used. 27 impressions were taken with three different types of impression coping: closed tray technique coping (CT), open tray technique coping (COT) and telescopic open tray coping (TOT). The impressions were poured. Analogues were matched with scan bodies to be scanned and exported in STL. An implant bar was designed from each STL and another one from the master model. A comparison between these bars was obtained. Linear and angular measurements for every type of coping were calculated for different angulations. The collected data were analyzed with ANOVA test (95% of confidence). Student’s t test showed a significative discrepancy (p ≤ 0.001) on linear and angular measurements on Δx, Δy, Δz with different transfer types as well as diverse implant positioning angles (p ≤ 0.001). Within the limitations of this study, it can be concluded that the coping type and the implants divergence may be significant parameters influencing the impression accuracy.

Evaluation of the influence of the impression technique, scanning direction and type of scanner on the accuracy of the final model

Objective: The purpose of this study is to evaluate the influence of the type of scanner and scanning direction on the accuracy of the final cast. Material and Methods: A partial master cast was used as a reference. A total of 128 scans were obtained and divided into two groups: the conventional method and the digital method. The digital group was divided into three groups: TRIOS 3, Omnicam and CS 3600. Each of these groups was subdivided according to the scanning direction, and each scan was overlaid on the digital reference cast to measure the trueness and precision of the procedures. Results: The overall precision values for the type of impression were 59.89 ± 13.08 mm for conventional and 13.42 ± 4.28 mm for digital; the values for trueness were 49.37 ± 19.13 mm for conventional and 53.53 ± 4.97 mm for digital; the scanning direction trueness values were 53.05 ± 4.36 mm for continuous and 54.03 ± 5.52 mm for segmented; and the precision values were 14.18 ± 4.67 mm for continuous and 12.67 ± 3.75 mm for segmented (p> 0.05). For the scanner type, the trueness values were 50.06 ± 2.65 mm for Trios 3, 57.45 ± 4.63 mm for Omnicam, and 52.57 ± 4.65 mm for Carestream; and those for precision were 11.7 ± 2.07 mm for Trios 3, 10.09 ± 2.24 mm for Omnicam, and 18.49 ± 2.42 mm for Carestream (p <0.05). Conclusions: The digital impression method is the most favorable method regarding precision; in terms of trueness, there are no differences between the types of impressions. KEYWORDS Conventional impression; Intra oral impression; Accuracy; Trueness.

Role of Peroral Cholangioscopy for Diagnosis and Staging of Biliary Tumors

Objectives: Peroral cholangioscopy (POC) has shown to be a useful diagnostic procedure in the evaluation of biliary strictures; however, data regarding its role on preoperative staging are scarce. The aim of this study was to evaluate POC role in the diagnosis and preoperative intraductal staging of perihilar cholangiocarcinoma (CCA). Methods: Retrospective study that included all patients who underwent POC with SpyGlassTM Direct Visualization System for the diagnosis of biliary strictures or for preoperative evaluation of extrahepatic biliary tumors, between 2015 and 2019, in a single tertiary center. Results: Forty-three patients were included, 63% male with a median age of 62 years. Thirty-eight (88.3%) underwent POC due to indeterminate biliary strictures, 3 (7%) due to bile duct filling defect, and 2 (4.7%) for intraductal staging of perihilar CCA. In the follow-up, a final diagnosis of malignancy was established in 56% of the patients. Visual impression accuracy with SpyGlass was 95.1% (with 100% sensitivity and 89.5% specificity). SpyBite biopsies accuracy was 80.5% (63.6% sensitivity and 100% specificity). In the 19 patients with a final perihilar CCA diagnosis, intraductal evaluation with SpyGlass altered anatomic classification (Bismuth-Corlette) defined by previous imagiologic findings in 8 (42.1%) patients. Alteration in anatomic classification changed therapeutic approach in 4 (21%). Conclusions: POC use for evaluating intraductal spread in potentially resectable perihilar CCA can detect more extensive and change surgical management. In the future, preoperative staging of perihilar CCA with POC combined with imagiologic evaluation of vascular extension of the lesions may optimize surgical results.

A prospective clinical study on implant impression accuracy

Background An accurate impression is crucial to the long-term success of dental implants. This investigation evaluated the accuracy of the open and closed implant impression techniques in partially edentulous patients who received two adjacent implants. Material and methods Forty patients received Osstem Implants (Osstem Implant System, Seoul, Korea). Two impressions were made for each patient, one using an open tray and a second with a closed tray technique. The horizontal distances between two impression copings were measured and compared to similar measurements on the master casts. Also, under a stereomicroscope (AmScop14370, Myford Road, #150, Irvine, CA 92606 USA) at a 50-fold magnification, the presence or absence of the marginal discrepancies was evaluated. Results There were no statistically significant differences regarding horizontal measurements and in the marginal relationship for the two impression techniques, except between the anterior and posterior regions, for the closed tray technique. There were also no statistically significant differences in the impression accuracy between maxillary and the mandibular arches. In addition, there were no statistically significant differences for the intraoral horizontal distances, compared to similar horizontal measurements on master casts, between the open and closed tray techniques. Conclusions Within the limitations of the present study, there were generally no differences in the impression accuracy between the open and closed tray techniques in partially edentulous patients with two adjacent implants.