International Journal of Computerized Dentistry, 01/2024

Aim: To compare the accuracy of three impression methods by comparing the distance between the reference points of the implant fixture, especially in curved maxillary anterior teeth. Materials and methods: Implant fixtures were placed in the maxillary central incisor and canine regions. A maxillary master cast was made using a model scanner and 3D printer. Ten impressions were taken from the three experimental groups constructed (group P: pick-up impression coping; group I: scan body with an intraoral scanner; group B: bite impression coping). The distance between the reference points, the angle between the scan bodies, and displacement of the 3D surface area were measured. Results: The distances between the reference points were significantly different between groups I and B in the maxillary incisors, and between group P and the other two groups in the maxillary canines. Group P had the least amount of displacement in both fixtures. Both fixtures showed the highest displacement in group B. Displacement of the 3D surface area in the maxillary incisors showed no significant difference between the groups. There was a significant difference in the maxillary canines between groups P and I. Conclusions: In the present study, all three implant impression methods showed changes in the position and angle of the fixture compared with the master cast. The highest accuracy was shown by the impression method using the pick-up impression coping, but the impression method using the intraoral scanner also showed clinically acceptable accuracy. It should be noted that errors may occur when taking impressions using a bite impression coping. Keywords: implant impression, implant angulation, bite impression coping, scan body, intraoral scanner

Aim: The aim of the present in vivo study was to compare the clinical trueness of primary mucostatic impressions obtained either by a classical alginate or an optical intraoral scanner technique in patients with a fully edentulous maxilla. Materials and methods: A total of 30 patients with a fully edentulous maxilla were included in the study and underwent both conventional impressions and intraoral optical impressions (Trios 3). The conventional impressions were casted and the resulting plaster casts were digitized using a desktop scanner (Imetric D104i). These digitized impressions were superimposed over the optical impressions to compare the differences between the two data sets. Statistical analyses were performed to identify relevant deviations. Results: For the 30 intraoral impressions, 80.88% of the surface areas were below the tolerance threshold of 25 µm and were thus considered similar to the areas scanned with the desktop scanner from the reference plaster cast. Interestingly, the differences (19.12% of the surface areas) were localized in depressible areas such as the vestibule, soft palate, incisive papilla, and flabby ridges. These locations were consistent with the mean of positive differences of +22.8 µm, indicating deformation or less compression with the use of the intraoral scanner. Conclusions: The digital primary impression of the fully edentulous maxilla can be considered similar to the conventional alginate impression except in the depressible areas. Considering the mucostatic objective of such a primary impression, one may consider the optical impression to be more accurate than the conventional one. Keywords: digital impression, conventional impression, intraoral scanner, clinical trial, edentulous patients, maxilla

Aim: The present in vitro study aimed to evaluate the depth of reading of intraoral scanners (IOSs) within the gingival sulcus. Materials and methods: A knife-edge preparation for a full crown was performed on a Frasaco model. The gingival sulcus of the scanned model was modified using a dedicated software program (Model Creator, exocad DentalCAD 2.4 Plovdiv) by setting the apical width (AW), coronal width (CW), and gingival sulcus depth (D). Two dental models with different gingival sulcus depths (1 or 2 mm) were printed using the digital light processing (DLP) technique. Each model was scanned 10 times. Seven different IOSs were used: Emerald, Trios 3, Carestream 3600, Dental Wings DWIO, CondorScan, True Definition Scanner (TDS), and Cerec Omnicam. Measurements of D values were performed using 3Shape 3D viewer software. The normality of the data distribution was evaluated using the Shapiro-Wilk test (P < 0.05). The nonparametric Levene’s test was used to check for homoscedasticity. The data were statistically analyzed using the Kruskal-Wallis test (α = 0.05) and the Nemenyi test. Results: All IOSs were able to read within the 1-mm–deep gingival sulcus, albeit with some statistically significant differences (P < 0.001). TDS and Trios 3 were able to read within the 2-mm–deep gingival sulcus (P < 0.001). Conclusions: The depth of reading of different IOSs can vary significantly. In the model with a 2-mm gingival sulcus, even in the absence of oral fluids, the depth of reading was incomplete, suggesting that deep preparations into the gingival sulcus are difficult to detect with IOSs. Keywords: intraoral scanner (IOS), gingival sulcus, depth of reading, knife-edge preparation, digital light processing

Aim: To summarize the features of condylar kinematics in patients with condylar reconstruction using a mandibular motion simulation method based on intraoral scanning registration. Materials and methods: Patients undergoing unilateral segmental mandibulectomy and autogenous bone reconstruction as well as healthy volunteers were enrolled in the study. Patients were grouped based on whether the condyles were reconstructed. Mandibular movements were recorded using a jaw tracking system, and kinematic models were simulated after registration. The path inclination of the condyle point, margin of border movement, deviation, and chewing cycle were analyzed. A t test and one-way analysis of variance (ANOVA) were carried out. Results: A total of 20 patients, including 6 with condylar reconstruction and 14 with condylar preservation as well as 10 healthy volunteers were included. The patients with condylar reconstruction showed flatter movement paths of the condyle points. The mean inclination angle of the condylar movement paths of the patients with condylar reconstruction (0.57 ± 12.54 degrees) was significantly smaller than that of those with condylar preservation (24.70 ± 3.90 degrees, P = 0.014) during both maximum opening and protrusion (7.04 ± 12.21 degrees and 31.12 ± 6.79 degrees, respectively, P = 0.022). The inclination angle of the condylar movement paths of the healthy volunteers was 16.81 ± 3.97 degrees during maximum opening and 21.54 ± 2.80 degrees during protrusion; no significant difference compared with the patients. The condyles of the affected side tended to deviate laterally in all patients during mouth opening and protrusion. Patients with condylar reconstruction showed more severe symptoms of mouth opening limitation and mandibular movement deviation as well as shorter chewing cycles than patients with condylar preservation. Conclusion: Patients with condylar reconstruction showed flatter movement paths of the condyle points, greater lateral motion range, and shorter chewing cycles than those with condylar preservation. The method of mandibular motion simulation based on intraoral scanning registration was feasible to simulate condylar movement. Keywords: digital technology, patient-specific ­modeling, electromyography, mandibular neoplasms, mandibular condyle, joint range of motion

Statement of the problem: Occlusion is associated with all disciplines of dentistry and plays a major role in the longevity of both implant- and tooth-borne restorations. Achieving occlusal harmony ensures balance is established between the dental and myofascial structures, which can be measurably established to high numerical tolerances with the T-Scan digital occlusal analysis system. Purpose: To describe and evaluate the known and proven applications of T-Scan digital occlusal analysis in various dental practice disciplines through a systematic review of the literature. Materials and methods: An electronic, English-language PubMed/MEDLINE and Cochrane Central Registry of Controlled Trials database search using the keywords “T-Scan,” “TMD,” “Occlusion,” “Implant Protected Occlusion,” and “Orthodontics” was conducted without any date restrictions. The related journal findings were hand searched to determine studies that met the eligibility criteria for inclusion in the present systematic review. Results: The PubMed/MEDLINE search identified 423 articles. After removing duplicates, the titles and abstracts of the remaining 421 studies were screened. 274 ineligible articles were excluded, leaving 147 articles. Of those, 33 articles were not in English, 27 full-text articles were not available, 4 were comments and letters to editors, 1 was a review, and 2 described techniques. A total of 86 articles met the eligibility criteria for inclusion. Conclusion: Much scientific evidence supports the use of T-Scan, as it measures relative occlusal contact forces and the time sequence durations of occlusal contacts objectively, accurately, and repeatedly for improved treatment outcomes. The system’s hardware, sensor, and software evolution from T-Scan I to today’s T-Scan 10 Novus system has overcome early sensor and system drawbacks to improve the clinical performance of T-Scan in many disciplines of dental medicine. Keywords: T-Scan, digital occlusal analysis

Purpose: A reference method for quantifying contaminations on two-piece abutments manufactured using CAD/CAM has not yet been established. In the present in vitro study, a pixel-­based machine learning (ML) method for detecting contamination on customized two-piece abutments was investigated and embedded in a semiautomated quantification pipeline. Materials and methods: Forty-nine CAD/CAM zirconia abutments were fabricated and bonded to a prefabricated titanium base. All samples were analyzed for contamination by scanning electron microscopy (SEM) imaging followed by pixel­-based ML and thresholding (SW) for contamination detection; quantification was performed in the postprocessing pipeline. Wilcoxon signed-rank test and Bland-Altmann plot were applied to compare both methods. The contaminated area fraction was recorded as a percentage. Results: There was no statistically significant difference between the percentages of contamination areas (median = 0.004) measured with ML (median = 0.008) and with SW (median = 0.012), asymptotic Wilcoxon test: P = 0.22. The Bland-Altmann plot demonstrated a mean difference of -0.006% (95% confidence interval [CI] from -0.011% to 0.0001%) with increased values from a contamination area fraction of > 0.03% for ML. Conclusion: Both segmentation methods showed comparable results in evaluating surface cleanliness; pixel-based ML is a promising assessment tool for detecting external contaminations on zirconia abutments. Further studies are required to investigate the clinical performance of this tool. Keywords: computer-aided design, scanning electron microscopy, machine learning, ultrasonics, hygiene, dental implant abutments

Aim: The purpose of this study was to present the use of computer-assisted periodontal surgery utilizing a novel surgical guide for cases with severe gingival enlargement through a clinical application in a patient with hereditary gingival fibromatosis. Materials and methods: The treatment plan included nonsurgical periodontal therapy, surgical periodontal treatment, and regular periodontal maintenance before the initiation of orthodontic treatment. Due to the increased soft tissue thickness, a surgical guide with a novel design was fabricated to facilitate the periodontal surgery since most of the patient’s teeth were malpositioned and underexposed due to fibromatosis. For this purpose, the patient’s intraoral scan was merged with a CBCT image in order to plan surgical excisions based on the anatomy of the teeth and the bone contour. Results: The customized surgical guide facilitated the gingivectomy by controlling not only the shape of the initial incisions but also their orientation toward the level of the cementoenamel junction, improving the efficiency of the clinical time compared with freehand surgery and assisting in the verification of the final soft tissue shape, based on the treatment plan. Conclusion: Digital technology through the superimposition of multiple data sets can assist in the diagnosis and multidisciplinary management of cases with gingival fibromatosis. The proposed design of the surgical guide can facilitate soft tissue surgery based on the digital treatment plan, leading to more predictable management of the soft tissue, especially in patients with severe gingival enlargement, as in cases with hereditary gingival fibromatosis or drug-induced gingival overgrowth Keywords: periodontal surgery, 3D surgical guide, hereditary gingival fibromatosis, surgical crown lengthening, digital data set

Aim: The aim of the present study was to demonstrate that fully digital workflows can provide predictable esthetic and functional outcomes. Materials and methods: The present clinical case report provides a step-by-step documentation of a full-mouth rehabilitation planned and performed with a fully digital approach utilizing an adhesive and no-prep method. After assessing the patient’s needs, a treatment plan was established that considered the patient’s functional and esthetic requests. The overlap of 2D images and 3D models and facial scans of the patient allowed the digital previsualization of the esthetic result by implementing the “copy-paste” approach to restore the maxillary anterior sextant. Conclusion: The final outcome was satisfactory in terms of esthetics, function, and soft tissue health. Keywords: tooth wear, dental occlusion, digital workflow, esthetics, digital wax-up, facial scan