International Journal of Computerized Dentistry, 03/2021

Aim: The purpose of this article is to present a novel method for the CBCT subtraction analysis of 3D changes following alveolar ridge preservation (ARP) with the application of a semi-automatic segmentation workflow and spatial registration. The study hypothesis was that by utilizing our novel approach, better 3D visualization and improved volumetric and linear evaluations of alveolar reconstructive procedures could be achieved following ARP compared with existing methodologies. Materials and methods: Ten surgical sites of 10 partially edentulous patients were treated with a tunneled guided bone regeneration approach for ARP. Spatial registration and a semi-automatic segmentation method were utilized to create 3D digital models of pre- and postoperative CBCT datasets for subtraction analysis. The primary outcome variable of the study was the volumetric difference between pre- and postoperative CBCT scans. Secondary outcome variables were horizontal and vertical linear measurements at the mesial, distal, and middle aspects of the alveolus. Results: Change of hard tissue volume averaged at 0.34 ± 0.99 cm3. The mean change of vertical hard tissue dimension was 5.97 ± 3.18 mm at the mesial, 6.40 ± 3.03 mm at the distal, and 7.01 ± 3.02 mm at the middle aspect of the extraction sites. Horizontal linear changes averaged at 6.19 ± 0.68 mm at the mesial, 6.32 ± 1.52 mm at the distal, and 6.90 ± 1.48 mm at the middle aspects of the extraction sites. Conclusion: The digital reconstruction of CBCT datasets with the presented approach may provide a better understanding of the healing mechanisms following ARP. Not only the direct effect on extraction socket healing, but also the indirect positive effect on adjacent teeth can be visualized. Keywords: 3D modelling, alveolar ridge preservation, extraction site development, radiographic image reconstruction, segmentation, volumetric analysis

Aim: Most of the intra- and postoperative patient discomfort related to complex mandibular third molar (M3M) extraction is proportional to the invasiveness of the surgery. This can be minimized through the support of dynamic navigation (DN) technology, which can be successfully applied in dental implantology.  Materials and methods: Three patients, one female (aged 25 years) and two males (aged 18 and 51 years, respectively) underwent the DN-supported extraction of partially impacted M3Ms with a flapless approach that required minimal bone removal. The patients’ discomfort and the speed of recovery were considered to be proof of the quality of the adopted procedure. Results: No postoperative discomfort such as pain or swelling was recorded in the immediate postoperative period, and no complications were reported within a month of the surgery. No medications were prescribed. The procedure lasted no longer than 20 min in all cases. Conclusion: Using DN technology, the real-time 3D monitoring of the clinical situation in each surgical phase enabled the surgeon to avoid soft tissue detachment as well as limit bone loss and intraoperative bleeding, thanks to a precise multi-­section of the tooth and important nearby anatomical structures, respectively. Keywords: dynamic navigation, computerized technology, mandibular third molar, tooth extraction

Aim: One-piece ceramic implants (O-PCIs) have proven to be clinically useful, with high survival rates. The biocompatibility and bio-inert characteristics of ceramics in addition to the fact that minimal plaque deposits occur on these materials provide esthetic advantages and justification for their use in the anterior maxilla. The objective of the present study was to investigate the suitability of O-PCI use in the anterior maxilla. Materials and methods: The data of patients who had received conventional two-piece titanium implants were analyzed. Virtual planning was performed to determine whether O-PCIs could have been used. Three groups were formed: single-tooth gap (group A); multiple-tooth gap treated with two implants (group B); and complex treatments with at least three implants (group C). In addition to assessing the feasibility of O-PCIs, their usefulness as well as additional procedures such as augmentation and a change in the implant quantity or position were evaluated. Values of the location of the virtual cementation line were summarized for all cases. Results: Without additional procedures, O-PCIs could be used in 97.9% of group A, 77.3% of group B, and 59.1% of group C. For group B, 18.2% of the cases could have been managed with additional augmentation. For the complex cases (group C), 18.2% of the patients would have been treatable if the planning had been altered, augmentation had been performed or implants with an inclined abutment had been available. The mean value of the lowest point of the cementation line was 2.9 mm (standard deviation 1.23; 0.0 to 7.2 mm). Conclusion: O-PCIs can be used in the anterior maxilla with planning. The esthetic advantages of ceramics can be leveraged for this part of the mouth, especially for single-tooth gaps. Keywords: dental implant, maxillary, one-piece implant, zirconia, ceramic implant, digital treatment simulation

Aim: The present prospective clinical study aimed to validate the Greifswald Digital Analyzing System (GEDAS) as a method for digital assessment of the occlusion in primary and mixed dentition. Materials and methods: The reproducibility of GEDAS in primary and mixed dentition was assessed using the intraclass correlation coefficient (ICC). In addition, the acceptability of the method to the dentist, the child, and the parent/caregiver was assessed using a modified visual analog scale of faces, the Frankl behavior scale, and the 10-point Likert scale. In total, 20 participants aged between 3 and 9 years (mean age: 6; standard deviation: ± 1.74) with primary (n = 10) and mixed (n = 10) dentition were recruited. Results: The ICC for the number of contact points in all teeth was 0.94 and for the area of contact points was 0.97, indicating good to excellent reproducibility. The average total number of contacts per bite registration per arch in the primary and mixed dentition was 36.5 (17 to 66) and 37.9 (9 to 74), respectively. The average of the total area of interocclusal contact area in the primary and mixed dentition was 25.55 mm2 (5.39 to 70.20) and 29.59 mm2 (2.80 to 78.53), respectively. During the procedure, the majority of dentists reported the child’s behavior to be positive (85%) and found the procedure easy to perform (80%), short (6.0 min), and tolerable (80%). Conclusion: GEDAS is an occlusal analysis tool with good acceptability and reproducibility in children and could be considered for the planning and assessment of restorative and orthodontic treatment in the intermediate stages. Keywords: GEDAS, occlusion, digital, primary dentition, mixed dentition, bite registration

Aim: Recording maximum intercuspal position (ICP) is critical for many dental procedures. Digital ICP from intraoral scanners (IOSs) produces variable results. This study investigated the sources of error in recording ICP using an IOS and a recently reported method. Materials and methods: A set of dentate models was scanned three times in a Rexcan DS2 scanner. The models were then scanned six times with a Cerec Omnicam IOS. For each scan, 10 bilateral ‘bite’ scans were performed (n = 6 x 10 bite registrations). Three key points were identified on the first intraoral scan and automatically transplanted onto all subsequent scans. The key point method was validated by using a ‘secondary’ key point transplantation from each scan back to the three laboratory scans, where the location of each point was compared using one-way analysis of variance. Full-arch errors on the intraoral scans were identified by comparing the intermolar key point distances on all intraoral scans against the ‘gold standard’ model scans. Precision of the virtual occlusion was identified by comparing the distance between all upper-lower key point pairs for all intraoral scans using intraclass correlation. Results: Automatic key points were transplanted to model scans with standard deviations (SDs) in location of ≤ 0.003 mm (upper [maxillary]) and ≤ 0.004 mm (lower [mandibular]) arch. The intermolar width of the intraoral scans had a mean error of 0.183 (± 0.061) mm (upper) and 0.017 (± 0.092) mm (lower) arch. Interocclusal key point separation showed poor reliability across groups, but good precision (SD < 0.022 mm) within groups. Conclusion: Automatic key points allowed valid linear distance comparisons across repeated scans. Poor trueness and precision in the full-arch intraoral scans adversely affected interocclusal registrations. Bite scan precision had a less detrimental effect on interocclusal registration. Keywords: occlusion, articulation, intraoral scanner, accuracy, precision, measurement

The present article introduces a new digital workflow for the fabrication of an immediate implantation prothesis. With this technique, based on the surgical planning, the positioning tray and the restoration shell are predesigned and premanufactured together with the implant guide before the physical surgery. After implantation, the restoration shell is placed and bonded with a temporary abutment guided by the positioning tray, which acts as a type of tooth-borne device to guide the placement and bonding of the immediate restoration. The restoration shell acts as a type of hollowed out restoration in the tissue surface to improve the implantation error tolerance. Keywords: 3D modeling, immediate restoration, positioning tray, restoration shell

Background: Dynamic navigation has important potential advantages over the static approach for fully edentulous patients. To the best of the authors’ knowledge, this is the first published case report describing the use of a dynamic implant navigation technique for a fully edentulous patient. Case report: A 55-year-old female presented for the replacement of missing teeth. Treatment with an implant-supported fixed dental prosthesis was proposed. A digital navigation implant surgery/immediate provisionalization protocol was used. An acrylic resin denture was fabricated as a radiographic guide. Digital data were obtained through the double scan technique, and a prosthetically driven 3D implant positioning was designed. Four titanium mini screws were inserted into the mandible for registration. The first implant was inserted in a freehand manner and attached to a patient tracker. After calibration and registration, the navigation system was set up. The other five implants were inserted using the navigation system. The procedure followed for the maxilla was similar. After surgery, a loading procedure was performed within 24 h. Results: Following implant placement, a postoperative CBCT scan was performed. The results showed that all implants were placed precisely, in accordance with the treatment plan. Conclusion: From the results obtained it appears that a fully digital workflow for prosthetically driven implant navigation surgery is suitable for the treatment of fully edentulous patients requiring an implant-supported fixed restoration. High-level evidence is needed to determine the accuracy and precision of this workflow. Keywords: dynamic navigation, dental implant, oral implant­ology, digital workflow, case report, fully edentulous jaw

3D printing is a process whereby a given material is deposited in successive layers to create a 3D object. In dentistry, this technology involves three steps: digital data acquisition using a scanner and/or CBCT, data processing and design within a software application, and manufacturing through 3D printing. The aim of the present article is to discuss the clinical application of 3D printing in endodontics through the presentation of three specific and original endodontic clinical cases. Innovative approaches were utilized in these cases for the treatment of a calcified root canal, periapical surgery, and autotransplantation. The results of all three cases were promising regarding proper case selection and in the design process. 3D-printing technology may be helpful to reduce surgical time, operator bias, and the risk of procedural errors. 
 Keywords: endodontics, 3D printing, stereolithography, calcification, root channel, apical surgery, autotransplantation, surgical guide

Objectives: To present a solid index (SI), a 3D-printed replica of a patient’s preexisting complete denture, which allows the dentist to accurately capture the position of the implants and the dental technician to model a bar for overdenture (OD) in CAD software with the use of reverse implant libraries. Materials and methods: A patient in need of rehabilitation of a fully edentulous mandible was restored with an implant OD supported by a polyetheretherketone (PEEK) milled bar. The position of the implants was captured through a physical impression using an SI, with the transfers screwed in. The analogs were then connected, and the SI was scanned upside down to directly capture the position of the implants in the space. This scan was used to design the bar in CAD software using reverse implant libraries, without the need for pouring any SI-derived cast or for using any scanbody. The bar was milled in PEEK. Results: When delivered to the patient, the bar was clinically precise, screwing perfectly onto the implants without any tension or misfit. Conclusions: The present proof-of-concept article supports the use of an SI and reverse implant libraries for the fabrication of a bar for OD. Further clinical studies are needed to confirm these results. Keywords: solid index, reverse implant library, intraoral scanner, accuracy