EditorialPubMed ID (PMID): 32555763Pages 103-105, Language: German, English
SciencePubMed ID (PMID): 32555764Pages 109-117, Language: German, English
Aim: To evaluate width loss of the alveolar ridge three years after implant placement in a fresh extraction socket following two different tissue healing methodologies: conventional healing procedure vs CAD/CAM technology for a customized healing abutment.
Materials and methods: Post-extraction sockets underwent immediate dental implant placement without the voids being filled between the implant surface and the socket wall. Samples (one implant per patient) were retrospectively enrolled in each group according to the type of healing procedure: implants in the conventional group underwent standard closed healing with a cover screw, while in the customized group the healing abutment was immediately screwed onto the head of the implant, mimicking the look of the extracted tooth fabricated by CAD/CAM technology. The width of the alveolar ridge was measured on 3D radiographs at baseline (before surgery) and three years postsurgery. Nonparametric statistics were performed with a significance level of 0.01.
Results: A total of 54 dental implants were selected. An implant survival rate of 100% was reported for all implants after 36 months. Three years after implant placement, loss in bone width was registered for both the conventional and customized groups, being 2.2 (1.1) and 0.2 (0.7) mm, respectively. Changes in the customized group were significantly lower than in the conventional group. Significant differences were again found between the groups for each of the tooth sites. Loss of bone width appeared negligible (from incisor to premolar), with values ranging between 0.2 and 0.4 mm in the customized group, whereas in the conventional group all tooth sites underwent wide shrinkage (with a bone loss ranging from 1.6 to 3.0 mm).
Conclusion: The CAD/CAM procedure might provide the following advantages: 1) Stabilization of the gingival setting and bone volume in a fresh socket implant; 2) Maintaining the same emergence profile of teeth for restorative crowns, avoiding laboratory approximation of the emergence profile of the definitive restoration; and 3) Optimal prosthetic-surgical planning and minimally invasive extraction to preserve the integrity of the supporting tissue.
Keywords: dental implant, immediate implant placement, dental abutment, customized abutment, cone beam computed tomography
SciencePubMed ID (PMID): 32555765Pages 119-128, Language: German, English
Aim: To compare the accuracy and effort of digital workflow for guided endodontic access (GEA) procedures using two different software applications in 3D-printed teeth modeled to simulate pulp canal obliteration (PCO) in vitro.
Materials and methods: 32 3D-printed incisors with simulated PCO were fabricated and mounted, four each on maxillary and mandibular study arches. Cone beam computed tomography (CBCT) and 3D surface scans were matched and used to virtually plan and prepare GEA by one operator using two different methods: 1) CoDiagnostiX (CDX; Dental Wings) with 3D-printed templates, and 2) Sicat Endo (SE; Sicat) with subtractive CAD/CAM-manufactured templates. Postoperative CBCT and virtual planning data were superimposed for analysis. Accuracy was assessed by measuring the discrepancies between planned and prepared cavities at the tip of the bur (three spatial dimensions, 3D vector, angle). Virtual planning effort was defined as the time and number of computer clicks. A 95% confidence interval (CI) was computed for each sample.
Results: SE successfully located root canals for GEA in 16/16 cases (100%) and CDX in 15/16 cases (94%). SE resulted in less mean deviation at the tip of the bur with regard to distance in the labial-oral direction (0.12 mm), 3D vector (0.35 mm), and angle (0.68 degrees) compared with CDX (0.54 mm, 0.74 mm, 1.57 degrees, respectively; P < 0.001). CDX required less mean planning time and effort for each four-tooth arch (10 min 50 s, 107 clicks) than SE (20 min 28 s, 341 clicks; P < 0.05).
Conclusions: Both methods enabled rapid drill path planning, a predictable GEA procedure, and the reliable location of root canals in teeth with PCO without perforation.
Keywords: 3D printing, access cavity, accuracy, calcific metamorphosis, guided endodontics, pulp canal obliteration, root canal treatment, template
SciencePubMed ID (PMID): 32555766Pages 129-138, Language: German, English
Aim: Despite the expanding implementation of intraoral scanning (IOS) devices, indirect digitization of conventional impressions or casts still represents the primary access to CAD/CAM. The aim of this study was to evaluate the accuracy of data acquired from impression scans and cast scans with respect to impression material and type of cast used.
Materials and methods: A standardized titanium model for a four-unit fixed dental prosthesis (FDP) served as a testing model. Industrial computed tomography (CT) was applied, generating a reference data set. Four different impression materials were utilized (n = 12 per material): 1) Impregum Penta (polyether/group PE); 2) Imprint 4 Penta Super Quick Heavy + Super Quick Light (polyvinyl siloxane (PVS)/group PVS-I); 3) Dimension Penta H Quick + L (PVS/group PVS-D); and 4) Imprint 4 Preliminary Penta Super Quick (PVS/group PVS-P). Data were obtained from three different model situations, ie, impressions (group IMP), unsectioned plaster casts (group UNSEC), and sectioned casts (group SEC). The surfaces were digitized three times each using a laboratory scanner. The resulting test data were superposed with the reference data using a best-fit algorithm to evaluate accuracy. Statistical analysis was conducted using the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney tests (level of significance: P < 0.050).
Results: Imprint 4 Penta presented the highest overall accuracy, while Imprint 4 Preliminary Penta Super Quick displayed the poorest results. Regarding the model situation (impression scan vs cast scan), impression scans from Impregum Penta and Imprint 4 Penta showed superior results.
Conclusion: Impression scans in combination with high-precision impression material results in the most accurate data.
Keywords: accuracy, CAD/CAM, cast scan, digital impression, impression material, impression scan, STL data
SciencePubMed ID (PMID): 32555767Pages 139-148, Language: German, English
Frontal cephalometric radiography (frontal ceph) is one of the important diagnostic methods in orthodontics and maxillofacial surgery. It allows one to determine occlusion anomalies in the transverse and vertical planes and to evaluate the symmetry of the facial skeleton relative to the median plane, including analysis of the position of the jawbone.
Aim: The aim of this study was to develop an artificial neural network (ANN) for placing cephalometric points (CPs) on frontal cephs and to compare the accuracy of its performance against humans.
Materials and methods: The study included 330 depersonalized frontal cephs: 300 cephs for training ANNs and 30 for research. Each image was imported into the ViSurgery software (Skolkovo, Russia) and the 45 CPs were arranged. The CPs were divided into three groups: 1) precise anatomical landmarks; 2) complex anatomical landmarks; and 3) indistinct anatomical landmarks. Two ANNs were used to improve the accuracy of CP placement. The first ANN solved the problem of multiclass image segmentation, and the second regression ANN was used to correct the predictions of the first ANN. The accuracy of CP placement was compared between the ANN and three groups of doctors: expert, regular, and inexperienced. Then, using the Wilcoxon t test, the hypothesis that an ANN makes fewer or as many errors as doctors in the three groups of points was tested.
Results: The deviation was estimated by the mean absolute error (MAE). The MAE for the points placed by the ANN, as compared with the control, was close to the average result for the regular doctor group: 2.87 mm (ANN) and 2.85 mm (regular group); 2.47 mm (expert group), and 3.61 mm (inexperienced group). The results for individual groups of points are presented. On average, the ANN places CPs no less accurately than the regular doctor group in each group of points. However, calculating all points in total, this hypothesis was rejected because the P value was 0.0056. A different result was observed among the inexperienced doctor group. Points from groups 2 and 3, as well as all points in total, were placed more accurately by the ANN (P = 0.9998, 0.2628, and 0.9982, respectively). The exception was group 1, where the points were more accurately placed by the inexperienced doctors (P = 0.0006).
Conclusion: The results of the present study show that ANNs can achieve accuracy comparable to humans in placing CPs, and in some cases surpass the accuracy of inexperienced doctors (students, residents, graduate students).
Keywords: 2D cephalometry, frontal cephalogram, artificial neural network landmarking, keypoints detection, accuracy of cephalogram landmarking, cephalogram measurement accuracy
ApplicationPubMed ID (PMID): 32555768Pages 149-160, Language: German, English
The use of the latest digital technology is bringing about a fundamental change in diagnostic planning. Apps based on mobile devices such as IvoSmile (Ivoclar Vivadent) use augmented reality to make lasting improvements to therapy decisions on the basis of 'informed consent.' In addition to significantly facilitating work and saving resources, the possibilities of interactive communication are also being expanded. Further advances in this technology will also revolutionize the integration of design results into the definitive manufacturing process.
Keywords: smile design, esthetics, digital, veneer, augmented reality, therapy planning
ApplicationPubMed ID (PMID): 32555769Pages 161-181, Language: German, English
Aim: The purpose of this article is to present the preliminary clinical results obtained with a novel hybrid digital-analog technique, the solid index impression protocol (SIIP), which uses a solid index to capture accurate impressions of multiple implants for the fabrication of implant-supported fixed full arches (FFAs).
Materials and methods: This pilot study was based on five patients, each treated with a FFA supported by four implants. Three months after implant placement, impressions were taken for all patients with an intraoral scanner (IOS) (direct digital impression) and with the SIIP, using a custom tray consisting of four hollow cylinders connected with a bar. This index was linked to the implant transfers and transferred to the laboratory, and the definitive FFAs were fabricated based on it. The outcomes of the study were the passive fit of implant superstructures and the accuracy of the models generated by the SIIP, inspected using a coordinate measuring machine (CMM) and reverse engineering software, and compared with the accuracy of direct digital impressions.
Results: Excellent clinical precision and passive fit were obtained in all five implant-supported FFAs fabricated with the SIIP. One year after delivery, all FFAs were functional without any complication. Differences in accuracy were found between the SIIP and direct intraoral scanning.
Conclusions: The SIIP seems to represent a viable option for capturing accurate impressions for the fabrication of clinically precise implant-supported FFAs with a hybrid digital–analog workflow. Further studies are needed to confirm these results.
Keywords: digital workflow, intraoral scanners, fixed full arches, accuracy, passive fit
ApplicationPubMed ID (PMID): 32337516Pages 183-189, Language: German, English
Aim: To describe a method of digitally customizing 3D-printed face mask designs using 3D face scans and free software.
Materials and methods: The procedure of creating customized face masks initially involved importing and aligning STL files of face scans and mask components in free CAD software. The imported mask described in this article is composed of three different STL files (body, filter structure, and grid). The body of the mask was then edited to fit precisely into the face scan STL by using the software's offset tool, followed by adjustments and smoothening of the surfaces of the edges. The resulting customized body of the mask plus the filter and grid STL files were exported and 3D printed with polylactic acid (PLA) filament using a fused deposition modeling (FDM) 3D printer. For the purposes of comparison, a conventional 3D-printed mask (from the original STL files, without being customized for the face scan) was also 3D printed from the original STL files. Both face masks were tested on the same two volunteers.
Results: The customized 3D-printed face mask presented a higher adaptation compared with the conventional face mask. The area of facial contact matched the one digitally designed in the software. The 3D-printed grid could clip exactly into the filter, which in turn could be precisely screwed into the body of the face mask.
Conclusion: Within the limitations of this technical report, the present findings suggest that customized 3D-printed face masks with enhanced adaptation can be digitally designed using face scans and free CAD software.
Keywords: facial scanning, face mask, 3D printing, CAD/CAM, COVID-19