International Journal of Computerized Dentistry, 03/2020

Aim: To assess the accuracy of DigiBrain4, Inc (DB4) Dental Classifier and DB4 Smart Search Engine* in recognizing, categorizing, and classifying dental visual assets as compared with Google Search Engine, one of the largest publicly available search engines and the largest data repository. Materials and methods: Dental visual assets were collected and labeled according to type, category, class, and modifiers. These dental visual assets contained radiographs and clinical images of patients' teeth and occlusion from different angles of view. A modified SqueezeNet architecture was implemented using the TensorFlow r1.10 framework. The model was trained using two NVIDIA Volta graphics processing units (GPUs). A program was built to search Google Images, using Chrome driver (Google web driver) and submit the returned images to the DB4 Dental Classifier and DB4 Smart Search Engine. The categorical accuracy of the DB4 Dental Classifier and DB4 Smart Search Engine in recognizing, categorizing, and classifying dental visual assets was then compared with that of Google Search Engine. Results: The categorical accuracy achieved using the DB4 Smart Search Engine for searching dental visual assets was 0.93, whereas that achieved using Google Search Engine was 0.32. Conclusion: The current DB4 Dental Classifier and DB4 Smart Search Engine application and add-on have proved to be accurate in recognizing, categorizing, and classifying dental visual assets. The search engine was able to label images and reject non-relevant results. Keywords: dental visual assets, artificial intelligence, dental radiographs, dental clinical images, dental classifier, smart search engine, machine learning, deep learning, convolutional neural network

Aim: To present a minimally invasive approach to solve the impaction of palatal canines using computer-guided orthodontic miniscrews. Materials and methods: Miniscrew-supported appliances for palatal canine disimpaction are performed with CAD/CAM technology. With adequate software, it is possible to match the STL files of the dental arch with the DICOM images of the maxilla, previously transformed into STL files. The ideal points for miniscrew insertion can be identified on the STL 3D model file on the basis of the width and thickness of the palatal vault. A software application allows for the design of the surgical guide, which is printed using a 3D printer. The virtual position of the planned miniscrews is transferred onto a printed dental cast on which the orthodontic device is realized. On the day of surgery, both the surgical guide and the orthodontic appliance are ready for use. Results: Miniscrew insertion and palatal canine disimpaction can be achieved in one surgical procedure. Conclusion: The use of computer-guided skeletal anchorage allows for both the reduction of the biomechanical side effects typical of conventional treatment and the risk of damaging adjacent anatomical structures, increasing the effectiveness of treatment. Controlled clinical trials are necessary to evaluate more fully any advantages of this minimally invasive technique. Keywords: TADs, canine impaction, CAD/CAM, miniscrew, orthodontics, surgical template

Aim: To evaluate the fracture resistance and failure pattern of 3D-printed and milled composite resin crowns as a function of different material thicknesses. Materials and methods: Three typodont tooth models were prepared to receive a full coverage composite resin crown with different thicknesses (0.5, 1.0, and 1.5 mm). The prepared master casts were digitally scanned using an intraoral scanner, and the STL files were used to fabricate 60 nanocomposite crowns divided into two groups according to the material thickness (n = 10) and fabrication method: a 3D-printed group (3D) using an SLA printer with nanocomposite, and a milled group (M) using a milling machine and composite blocks. All crowns were adhesively seated on stereolithography (SLA)-fabricated dies. All samples were subjected to thermomechanical loading and fracture testing. The load to fracture [N] was recorded and the failure pattern evaluated. Data were statistically analyzed using a two-way ANOVA followed by a Bonferroni post hoc test. The level of significance was set at α = 0.05. Results: The 3D group showed the highest values for fracture resistance compared with the milled group within the three tested thicknesses (P 0.001). The 3D and M groups presented significantly higher load to fracture for the 1.5-mm thickness (2383.5 ± 188.58 N and 1284.7 ± 77.62 N, respectively) compared with the 1.0-mm thickness (1945.9 ± 65.32 N and 932.1 ± 41.29 N, respectively) and the 0.5-mm thickness, which showed the lowest values in both groups (1345.0 ± 101.15 N and 519.3 ± 32.96 N, respectively). A higher incidence of irreparable fractures was observed for the 1.5-mm thickness. Conclusion: 3D-printed composite resin crowns showed high fracture resistance at different material thicknesses and can be suggested as a viable solution in conservative dentistry. Keywords: additive manufacturing, 3D printing, composite crowns, CAD/CAM, fracture resistance, failure pattern

Aim: The traditional hinge axis theory of temporomandibular joint (TMJ) dynamics is increasingly being replaced by the theory of instantaneous centers of rotation (ICR). Typically, ICR determinations are based on theoretical calculations or three-dimensional approximations of finite element models. Materials and methods: With the advent of real-time magnetic resonance imaging (MRI), natural physiologic movements of the TMJ may be visualized with 15 frames per second. The present study employs real-time MRI to analyze the TMJ biomechanics of healthy volunteers during mandibular movements, with a special emphasis on horizontal condylar inclination (HCI) and ICR pathways. The Wilcoxon rank sum test was used to comparatively analyze ICR pathways of mandibular opening and closure. Results: Mean HCI was 34.8 degrees (± 11.3 degrees) and mean mandibular rotation was 26.6 degrees (± 7.2 degrees). Within a mandibular motion of 10 to 30 degrees, the resulting x- and y-translation during opening and closure of the mandible differed significantly (10 to 20 degrees, x: P = 0.02 and y: P 0.01; 20 to 30 degrees, x: P 0.001 and y: P = 0.01). Rotation of both 0 to 10 degrees and > 30 degrees showed no significant differences in x- and y-translation. Near occlusion movements differed only for y-translation (P 0.01). Conclusion: Real-time MRI facilitates the direct recording of TMJ structures during physiologic mandibular movements. The present findings support the theory of ICR. Statistics confirmed that opening and closure of the mandible follow different ICR pathways, which might be due to muscular activity discrepancies during different movement directions. ICR pathways were similar within maximum interincisal distance (MID) and near occlusion (NO), which might be explained by limited extensibility of tissue fibers (MID) and tooth contact (NO), respectively. Keywords: temporomandibular joint, jaw dynamics, biomechanics, real-time magnetic resonance imaging, instantaneous center of rotation

Aim: The aim of the present study was to evaluate the number, strength, and position of occlusal contacts shown using an intraoral scanner (IOS) and a digital occlusal analysis system (T-Scan) compared with the current gold standard using occlusal foil (OF). Materials and methods: Occlusal contacts were analyzed for 70 volunteers using OF in maximum intercuspation (MI). The contact points obtained using the IOS were evaluated using a screenshot from Zirkonzahn.Modellier CAD software. Finally, the volunteers were asked to bite on the sensor sheet of the T-Scan system. For the evaluation of these data, the contact points of the OF and the IOS were graded as light, medium, and strong. Furthermore, the positions of the contact points were analyzed for the anterior region (premolars and molars). Parametric statistical tests were applied to analyze the differences among the three methods. Results: The mean number of all contact points was similar: 29 ± 8 with the OF, 30 ± 12 with the IOS, and 24 ± 10 with the T-Scan. However, results were different in terms of the grading of the strength of contact points: mean number of light contacts: 8 ± 4 OF vs 17 ± 8 IOS and 17 ± 6 T-Scan; medium contacts: 12 ± 5 OF vs 8 ± 4 IOS and 5 ± 4 T-Scan; and strong contacts: 9 ± 5 OF vs 6 ± 6 IOS and 4 ± 2 T-Scan. The positions of the occlusal contact points were also different. Conclusion: The data sets showed that there were differences in the distribution of occlusal contact points evaluated using the OF, the IOS, and the T-Scan system. Although the number of detected occlusal contacts was similar, different occlusal contact protocols were determined by the three different methods. Keywords: occlusal contacts, intraoral scanner, T-Scan, occlusal foil, contact strength

Aim: Surgically facilitated orthodontic treatment is increasingly being used, especially for adults, to facilitate tooth movements and reduce the duration of orthodontic treatment. The present article reports on an innovative, safe, and minimally invasive technique to perform flapless corticotomies using a dedicated surgical guide produced with a complete digital intraoral and laboratory workflow. Materials and methods: A 51-year-old man presented with maxillary and mandibular anterior crowding. He required rapid treatment with limited use of braces. Corticotomies were planned for both arches before the use of orthodontic appliances. The matching of the stereolithographic files obtained from the digital prints of the full arches and the cone beam computed tomography images allowed for the positioning of the cutting planes for corticisions. The guide was printed with a transparent, biocompatible, and photopolymerizable resin, and cold sterilized. Minimally invasive corticotomies were performed using a piezoelectric instrument. The orthodontic treatment started immediately after surgery. Results: No adverse events were recorded during surgery. The piezoelectric instrument was guided accurately, and precise application of the corticisions prevented all the anatomical elements from being injured. The healing was uneventful and the patient experienced no pain. Conclusion: The present report shows that a surgical guide specifically and digitally produced for corticotomies allowed for the performance of a minimally invasive flapless technique and accurate piezosurgery. The use of such a guide was easy to implement, made the procedure safer, and reduced postoperative pain. Keywords: guided surgery, corticotomies, surgical guide, computer-aided design, surgically facilitated orthodontic treatment, piezoelectric surgery

The utilization of digital 3D surface images (STL format) for planning cases of computer-guided implant surgery is very useful in partially edentulous cases. In fully edentulous cases, however, the absence of teeth makes it necessary to add reference markers. The proposed protocol demonstrates a simple procedure that allows for the superimposition of STL and radiologic data (DICOM format). In the presented patient case, the tissue-bearing area of the prosthesis was relined with a polysulfide impression material and sent to the laboratory. A master cast was produced. The prosthesis was relined to improve intraoral stability and was provided with at least three radiopaque 3D markers. An STL copy of the prosthesis and the model was generated through a laboratory scanner. The patient wore the prosthesis with the attached markers during the 3D radiologic examination. In the planning software (CoDiagnostiX; Dental Wings), the prosthesis markers on the STL were matched to the corresponding markers visible on the DICOM data. Then, the STL of the model was matched to that of the prosthesis. Once the STL of the mucosa and the prosthesis were imported into the software, new possibilities arose, ie, the option to add other digital or traditional tooth setups to the same radiologic data or to design a surgical guide based on the actual mucosa of the patient. Keywords: coDiagnostiX, DICOM, fully edentulous patients, guided surgery, smart fusion, STL

For decades, double crowns in different variations have proven to be reliable attachments in removable prosthetics. Supported by teeth and implants, they provide proper retention, a considerable degree of chewing comfort, and satisfying esthetics. A wide range of applications, optimal oral hygiene capabilities, and almost unlimited expandability are just some of the advantages of double crown anchored dentures. Among other things, abutment tooth loss is a frequent complication. If an abutment tooth is lost, the secondary crown is usually filled with resin and the denture can continue to be used. However, since the loss of one or more abutment teeth changes biomechanical load ratios, a decline in stability and comfort is likely to occur as well as overloading of the remaining abutment teeth. The concept presented in this article provides for the application of computer-assisted technologies that enable the preservation of the denture according to its original design. For this purpose, a lost or hopelessly decayed tooth is replaced with an implant using digital preplanning and guided implant surgery. The original primary crown is then reattached in its exact former position applying a CAD/CAM-fabricated meso-abutment. In effect, the number of abutment teeth can be preserved, the functionality of the denture maintained with reasonable effort, and further damage prevented. Keywords: CAD/CAM, double crowns, guided surgery, implant dentistry, implant prosthetics, removable denture, telescopic crowns

Aim: The aim of this case report is to present the minimally invasive replacement of a missing molar in the presence of considerable proximal undercuts of the adjacent abutment teeth. The use of two single-retainer resin-bonded fixed dental prostheses (RBFDPs) made this therapy possible. Materials and methods: A missing mandibular right first molar required replacement. Two single-retainer RBFDPs were digitally designed in the shape of half a molar each and were milled using CAD/CAM from monolithic 3Y-TZP zirconia ceramic. The posterior RBFDP portion retained by the second molar was designed in the pontic contact area to create a common path of insertion for the anterior RBFDP portion with the distal surface of the second premolar. A slight interlocking between the proximal contact surfaces of the two pontics was designed to prevent future migration between the split restorations. Precise placement of the two RBFDPs during adhesive luting was ensured with the aid of a positioning splint. Results: The patient was recalled after 10 months and was very satisfied with the minimally invasive molar replacement. Conclusion: Using two single-retainer RBFDPs to replace a molar in a split design enables a minimally invasive posterior tooth replacement despite considerable proximal undercuts of the adjacent abutment teeth. Keywords: resin-bonded fixed dental prostheses (RBFDPs), minimally invasive treatment, split molar, CAD/CAM, proximal undercut, monolithic zirconia (3Y-TZP)