International Journal of Computerized Dentistry, 01/2021

Aim: The transfer of 3D implant position planning to the clinical site is challenging. The aim of this study was to compare in vitro this transfer accuracy by using dynamic real-time navigation or static surgical guides. Materials and methods: Deviations between planned and actual pilot drill positions were calculated (Denacam and NobelGuide; each n = 90), matching pre- and postoperative CBCT images: entry point, angle, tip (each 3D); depth, mesiodistal/bucco-oral entry points, and angles (each 1D). The influence of the maxilla and mandible, implant region (anterior/posterior), and marker position (ipsilateral/contralateral, Denacam only) was investigated (Mann-Whitney U test). Results: No significant differences occurred regarding entry point (3D), mesiodistal/bucco-oral entry points (1D) or mesiodistal angle (1D) (P > 0.05). The angular and tip deviations (3D) were significantly smaller using Denacam (2.16 ± 0.59 degrees, 0.80 ± 0.55 mm; NobelGuide 2.54 ± 1.19 degrees, 1.09 ± 0.56 mm; P = 0.024, P < 0.0001). The deviations in depth and bucco-oral angle (1D) were significantly smaller using NobelGuide (1.05 ± 0.50 mm, 1.02 ± 1.16 degrees; Denacam 1.50 ± 0.64 mm, 1.51 ± 0.82 degrees; P < 0.0001). Significantly smaller deviations occurred within the mandible (Denacam, 5/8 parameters). Region and marker position showed no influence. No distinct influences were found with the use of NobelGuide. Conclusion: Denacam might possibly be a promising alternative to static surgical guides. Keywords: dynamic navigation, dental implantology, surgical guide, implant planning

Aim: To conduct an observational study evaluating the efficacy of a partially guided system for implant surgery. Materials and methods: The study included 48 implant placements in 24 patients. Following virtual implant planning with designated software, a surgical guide was fabricated using a 3D desktop printer. Each surgically placed implant was compared with its planned position in the software. The coronal and apical distance and angular errors of the implants were evaluated. The correlation between the errors and the variables (residual bone height, surgeon, implant placement site, guide support type, implant diameter) was analyzed using multiple regression analysis. Results: The coronal and apical mean distance errors were 1.28 ± 0.85 and 1.8 ± 0.97 mm, respectively. The mean angular error was 3.66 ± 3.37 degrees. The correlation coefficients (coronal: 0.285; apical: 0.308) indicated a significant linear correlation between the anterior and posterior implant placement positions (P < 0.05). Conclusion: A partially guided system with in-office guide fabrication using a 3D desktop printer is a useful option for implant placement. Keywords: computer-guided surgery, dental implants, printing, three-dimensional, surgical guide

Aim: The purpose of this study was to compare the accuracy of intraoral scanning on a tooth model according to four finish line conditions (supragingival, equigingival, subgingival, and subgingival with gingival cord). Materials and methods: To simulate the clinical situation, the abutment was fabricated using ceramic materials. A pigment was added to the transparent orthodontic silicone to create a translucent gingiva. A CAD reference model (CRM) was obtained using a contact scanner. Finish lines on the tooth preparation were placed at the subgingival (0.5 mm below the level of the gingiva), equigingival, and supragingival (0.5 mm above the level of the gingiva) locations. In addition, a gingival cord was packed into the gingival sulcus below the subgingival finish line. A CAD test model (CTM) was obtained using two types of intraoral scanners (IOSs), i500 (Medit) and EZIS PO (DDS; N = 20 per locations). CRM and CTM were superimposed and analyzed using 3D analysis software. In the statistical analysis, the comparison of accuracy according to the finish line locations was confirmed by one-way ANOVA (α = 0.05). The differences between the groups were analyzed using the Tukey HSD post-hoc test. Result: There was a significant difference in the accuracy of intraoral scanning according to the finish line locations of the tooth preparations (P < 0.001). The equigingival and subgingival finish lines showed poor accuracy. The use of gingival cords significantly improved the accuracy (P < 0.05). There were significant differences between the two types of IOSs, with the i500 showing better accuracy than the EZIS PO (P < 0.001). Conclusion: Supragingival finish lines or the use of gingival displacement cords is recommended for clinically acceptable accuracy (< 100 µm) of the marginal region captured with an IOS. Keywords: finish line, tooth preparation, intraoral scanner, accuracy

Aim: To evaluate the fracture resistance and failure pattern of endodontically treated teeth with post and cores made of different CAD/CAM materials in comparison with cast post and cores.Materials and methods: A total of 40 maxillary central incisors were divided into four groups. Post and cores were fabricated using the following materials: fiber-reinforced composite, high-density polymer, polymer-infiltrated ceramic network, and nonprecious metal alloy as a control group. Specimens were covered with lithium disilicate crowns and subjected to thermomechanical cyclic loading followed by fracture resistance testing until failure. One-way ANOVA followed by Bonferroni multiple comparison tests were used to determine significant differences between the four groups. The significance level was set at 0.05. 3D finite element analysis was then performed, and results were analyzed based on the von Mises stress distribution criteria and the maximum principal stress for the possible failure areas.Results: No statistically significant differences were found in the fracture resistance between the four groups. In terms of unrestorable failures, no significant differences were found among the tested groups.Conclusion: The tested post and cores have comparable fracture resistance to that of metallic cast post and cores in the anterior region.Clinical significance: Post and cores made of CAD/CAM materials offer an acceptable alternative for the restoration of anterior teeth. Keywords: post and cores, fracture resistance, hybrid ceramics, fiber-reinforced composite, finite element analysis

Aim: Limited data are available on the fitting properties of prototyped occlusal appliances. The aim of the present study was to assess the fitting of prototyped splints digitally designed with different offset values and generated with two different biocompatible resins. Materials and methods: Ten dental digital models were included, and occlusal splints were designed with different offset values (0.0, 0.05, 0.10, 0.15, 0.20, and 0.25 mm). Each splint was 3D printed using two different biocompatible resins, and the gap between the splint and the teeth was recorded by placing impression material. A specific 3D technology was used to assess the gap volume between the splint and the teeth and to calculate the Euclidean distance between the surface points of two digital models, with and without the gap volume. Results: The splints with a 0.20-mm offset value showed smaller gap volume and deviation analysis values compared with those with offset values of 0.15 and 0.25 mm (P < 0.05). These results were consistent with both types of biocompatible resins used. For each offset value tested, the gap volume and deviation value analysis did not significantly differ between the splints printed with the two different resins. Conclusion: According to the present findings, the 0.20-mm offset value would be the best choice when digitally designing occlusal appliances. Keywords: 3D printing, CAD/CAM, splint, occlusal appliance, digital dentistry, digital orthodontics

Introduction: Mixed reality (MR) represents a new evolution in technological development that combines both virtual reality (VR) and augmented reality (AR) to create a blend of the physical and digital worlds. However, the potential role of MR in preoperative diagnostics in oral and maxillofacial surgery has not been scientifically investigated and remains generally unclear. This article presents a workflow that integrated MR in its scheme. It also evaluates the potential benefit of MR compared with its predecessors, VR and AR.Material and methods: MR technology was used to plan the surgical treatment of a clinical case with an extensive tumor of the left maxilla. A workflow proposal incorporating both the surgeon and radiation oncologist is presented based on this experience. A total of 10 examiners rated the usability and applicability of MR for daily routines.Results: MR showed good results during preoperative planning for a surgically extensive case in terms of displaying 3D structures and enhancing the physical and virtual interactions among the examiners. Previously described drawbacks of other VR/AR applications such as nausea and motion sickness were not observed with MR. However, MR seems to lack intraoperative usability, which is a drawback.Conclusion: MR shows great potential in improving the preoperative assessment of 3D DICOM datasets and thus facilitating diagnostic measures. However, further improvements should be made to implement an MR workflow and incorporate it into the clinical treatment planning tree. Keywords: mixed reality, virtual reality, augmented reality, preoperative planning

For restoring extensive cavities in severely damaged or decayed posterior teeth, especially those with thin walls, indirect restorations are recommended rather than direct fillings. Regarding indirect restorations for inlays and onlays, composite resin-based CAD/CAM materials are considered to have several advantages over ceramics such as easy manufacturing, lower cost, and simpler repairability. A case is presented in this article in which the treatment plan and protocol combine multiple evidence-based clinical techniques such as immediate dentin sealing (IDS), cavity design optimization (CDO), and cervical margin relocation (CMR). For CDO and CMR, two different types of flowable composite resins with different viscosities were used. Restoring such extensively damaged teeth using a defect-oriented adhesive technique is considered a challenge both in terms of the preservation of healthy tooth structure and the proper isolation for adhesive luting. The IDS technique was used to enhance the bonding to the remaining dentin, while CDO was performed to avoid unnecessary removal of vital tooth structure, for example, undercuts. The deep subgingival margins were elevated using the CMR technique to facilitate the impression taking and a contamination-free luting of the final restoration. Combining the aforementioned techniques enabled a defect-oriented, minimally invasive restoration of a severely decayed tooth. The aim of this article is to present those techniques in a simplified way through a clinical case as a step-by-step guide for the practitioner. Keywords: onlay, minimally invasive, immediate dentin sealing, cavity design optimization, cervical margin relocation, flowable composite, CAD/CAM, composite blocks

Aim: This case report describes a digital workflow for prosthetically driven surgical planning, implant placement, and the fabrication of two screw-retained, complete-arch, implant-supported dentures in an edentulous patient. The purpose of this case report is to present and discuss the digital steps in the workflow, especially the scanning technique to obtain the centric relation, through a clinical case. The limitations of the workflow are also discussed.Materials and methods: Static computer-aided implant surgery (s-CAIS) was planned three-dimensionally, based on cone beam computed tomography, intraoral optical scanning, and digital bite registration. Using s-CAIS, four and six implants were placed in the edentulous mandible and maxilla, respectively. The final screw-retained complete-arch monolithic zirconia restorations were manufactured based on a digital workflow, using the pre-existing modified radiologic guide for the digital maxillomandibular record. Conclusions: The evolution of digital processing methods allows for design, processing, and fabrication of implant-supported fixed complete dentures using a surgical, prosthetic, and technical workflow based on 3D restorative backward planning. A digital prosthetic setup and CAD/CAM can be used for the fabrication of intraoral try-ins that serve as a model for the final monolithic zirconia superstructure. Keywords: backward planning, edentulous, complete-arch, implant-supported, fixed complete denture, CAD/CAM, monolithic zirconia, radiologic guide

Aim: The aim of the study was to compare the success and reliability of an artificial intelligence (AI) application in the detection and classification of submerged teeth in panoramic radiographs. Materials and methods: Convolutional neural network (CNN) algorithms were used to detect and classify submerged molars. The detection module, based on the stateof- the-art Faster R-CNN architecture, processed a radiograph to define the boundaries of submerged molars. A separate testing set was used to evaluate the diagnostic performance of the system and compare it with that of experts in the field. Result: The success rate of the classification and identification of the system was high when evaluated according to the reference standard. The system was extremely accurate in its performance in comparison with observers. Conclusions: The performance of the proposed computeraided diagnosis solution is comparable to that of experts. It is useful to diagnose submerged molars with an AI application to prevent errors. In addition, this will facilitate the diagnoses of pediatric dentists. Keywords: artificial intelligence, deep learning, infraocclusion, panoramic images, submerged teeth