International Journal of Computerized Dentistry, Pre-Print

Objectives: To evaluate the peri-implant marginal bone loss (MBL) and prosthodontic complications of maxillary screw-retained implant prosthesis fabricated from digital versus conventional full- arch implant impression. Material and Methods: 28 participants with edentulous maxillary arches were randomly selected and enrolled in two equal groups; Group I conventional impression group (CIG) and Group II Digital impression group (DIG). All patients were rehabilitated with maxillary screwretained implant prosthesis retained by 6 implants. Peri-implant MBL and prosthodontic complications and were registered at 6, 12, and 24 months (m). Data was collected and statistically analyzed. Results: Regarding the effect of time, there was a statistically significant increase in MBL at 6, 12 and 24 m follow-up periods (P<.001). As for the effect of groups, there was no statistically significant difference in MBL between CIG and DIG at 6, 12 and 24 m where P value was 0.083, 0.087 and 0.133 respectively. Prosthetic complications were recorded 19 times in the conventional group and 12 times in the digital group with no significant difference between both groups (P=.303). Conclusion: Digital full -arch implant impression is a reliable impression technique and may represent an alternative to conventional impression technique in the fabrication of maxillary screw-retained implant prosthesis. Keywords: conventional implant impression, digital implant impression, full- arch implant impression, marginal bone loss, maxillary screw-retained prosthesis, prosthodontic complications

Objective: The aim of this study was to examine the color stability of laminate veneer restorations restored with CAD/CAM material applied to bleached teeth. Material and methods: In this study, 80 upper central teeth extracted because of periodontal, orthodontic or trauma problems were used. The teeth were embedded in acrylic blocks and divided into 8 groups (n=10). Groups A, B, C and D were bleached with vital bleaching agent before preparation, and teeth were prepared for laminate veneer restorations. Groups E, F, G and H were prepared without bleaching. Groups A and E were restored with A1 GC LiSi İnitial HT blocks, Groups B and F were restored with A1 GC LiSi İnitial LT blocks, Groups C and G were restored with A1 IPS Emax CAD HT blocks, Groups D and H were restored with A1 IPS Emax CAD LT blocks. All restorations were adhesively cemented and aged for 2 and 5 years with thermal cycle. Color measurements of the restorations at the beginning, after 2 and 5 years of aging were measured with a spectrophotometer. Results:All bleached groups had more color changes than the unbleached groups. The least color change after 2 years of aging was observed in GC LiSi Initial LT (ΔE00=0.81) and IPS Emax CAD LT (ΔE00=0.81) materials which were used on unbleached teeth and the most color change was observed in GC Initial LiSi HT (ΔE00=0.93) and IPS Emax CAD HT material (ΔE00=0.92) which were used on bleached teeth. After 5 years of aging, the least color change was observed in IPS Emax CAD LT (ΔE00=0.83) and GC LiSi Initial LT material (ΔE00=0.84) which were used on unbleached and the highest color change was observed in GC Initial LiSi HT (ΔE00=0.96) and IPS Emax CAD HT material (ΔE00=0.94) which were used on bleached teeth. Conclusion: Bleaching and translucency affect the color stability. No difference was detected between the color changes of GC LiSi Initial and IPS Emax CAD materials. The increase in aging time increased the color changes of all materials. Clinical Significance: Bleaching and laminate veneer restorations may be preferred in many patients. For this reason, the long-term color change of laminate veneer restorations applied to bleached teeth is clinically very important. This study aimed to evaluate the effect of tooth bleaching on the long-term color change of laminate veneer restorations produced with different translucent CAD/CAM materials. Keywords: Bleaching, CAD/CAM, Color, Laminate veneer, Spectrophotometer

Aim: The aim of this in vitro study is to investigate the effects of different sintering procedures on the fit, color parameters, and fracture load of monolithic fixed partial prosthesis. Materials and Methods: Metal model was scanned and fixed partial prosthesis was designed. Groups were created by fabricating fixed partial prosthesis by using four different sinterization procedures (Prettau-Standard (PST), Prettau-Slow (PSL), Ice-Speed (IS), Ice-Standard (IST), n=10). PST-PSL (Group P, N=20) and IS-IST (Group I, N=20) were colored with different coloring liquids. The marginal and internal fit were measured using the silicone replica method. CIELAB values of the samples were measured using a spectrophotometer. Then, for each sample, the die was obtained from polymethyl methacrylate. The specimens were cemented into dies and tested in a universal testing machine for fracture load. One-way ANOVA were performed to assess the effect of the sintering procedure on the marginal and internal fit, fracture load, and ∆E00, ∆L', ∆C', and ∆H' values of fixed partial prosthesis. Results: PSL and PST groups showed significantly smaller internal and marginal fit compared to the IS group. Additionally, IST group internal fit values were significantly higher than Prettau groups. Sintering time reduction led to a decrease in ∆E00 values. Fracture loads values were not statistically significantly affected by the different sintering procedures in both brands. Conclusion: Different sintering procedures did not have a clinically significant effect on fit and fracture load. Different sintering procedures were found to have an impact on the color change of monolithic zirconia restorations. Keywords: Color, Fit, Fracture load, Sintering, Zirconia

Aim: The aim of this in vitro study was to investigate the influence of scan paths on the accuracy (trueness and precision) of intra-oral scanning of an implant impression on an edentulous patient. Material and methods: An epoxy resin maxillary model was made with 6 bone level implants (NobelParallel Conical Connection RP, NobelBiocare®). The implants were placed at the spot of the first incisor, the canine and the first molar. The trans gingival component (Multi-unit, NobelBiocare®) was screwed onto the implants. The scanbodies (IO 2C-A, Elos Accurate®) were then screwed onto the multi-units. The model was run through a coordinate measurement machine to obtain a control cast. Then, five different scanning paths, respectively the zigzag technique (ZZT), the zigzag technique with palatal (ZZTP), the wrap technique (WT), the wrap technique with palatal (WTP), and the big zigzag technique (BZZT), were applied by a single operator. Finally, each scan was compared to the control model. Results were assessed by one-way ANOVA and linear mixed effects models at P<0.05. Results: The study showed that scan paths ZZT and ZZTP had significantly lower absolute positioning errors and residual mean square errors than the others (P<0.0001). For distances between consecutive implant axes and for absolute vertical errors, their superiority was borderline (P<0.10). Overall, techniques ZZT and ZZTP were equally performant and proved to be the most accurate. Conclusions: This in vitro experimental study demonstrates that the scan path can have an influence on the accuracy of the optical impression for full arch rehabilitation on implants. Keywords: Accuracy, Dental implants, Digital impression, Edentulous, Intra-oral scanner, Scan path

Objectives: Mandibular single-implant overdenture is a well-established treatment modality for the management of completely edentulous patients. The use of CAD/CAM printing technology to fabricate complete dentures and overdentures is burgeoning. The trial aimed to clinically evaluate 3D-printed single-implant overdentures and compare outcomes to those of overdentures manufactured using conventional techniques. Materials and Methods: A randomized clinical trial (RCT) was designed. Twenty-eight participants were randomly allocated into two equal groups. Participants in the control group received conventionally manufactured single-implant overdentures, while participants in the printed group received digital light processing (DLP) printed single-implant overdentures. An evaluation was conducted to assess the rates of implant survival and success, as well as overdenture survival and success, along with the measurement of maximum biting force (MBF) over a one-year follow-up period. Data was collected and subjected to statistical analysis. Statistical significance was determined using a two-sided p-value with a threshold of less than 0.05. Results: The printed denture group had higher implant survival (100%) and success rates (92.8%) compared to the conventional denture group (85.7% survival, 85.7% success). Overdenture survival and success rates were 100% in the printed group and 78.6% in the conventional group. Both groups showed a significant increase in maximum biting force (MBF) at 3, 6, and 12 months of follow-up (P<0.001). The printed group demonstrated a statistically significant improvement in MBF compared to the conventional group (P<0.001). Conclusions: 3D-printed mandibular single-implant overdentures may represent an alternative to conventionally fabricated ones. Keywords: 3D printing, Biting Force, Denture Survival, Implant, Implant Survival, Overdenture

Medical imaging technology has greatly improved over the last 40 years. A good example of this is the improved 3D reconstruction capabilities of CTs, which enable photorealistic reconstructions. This technological advancement has also taken place in the computer industry, and the development of modern graphics cards has fueled progress in video games. In art, many of the techniques used to improve three-dimensionality have been known for centuries. At first sight, these fields seem unrelated, but there is actually considerable confluence. This paper focuses on three areas: fine arts, video games and radiology. The art section illustrates different drawing techniques used to create three-dimensionality. The section on video games shows the development of video games from the 1980s to the present day. Finally, the medical imaging section focuses on the first 3D radiography reconstructions in the 1980s and the improvements to the present day. Contemporary video games and 3D reconstructions of CTs enable photorealistic impressions of 3D anatomical structures. An important factor is shadow casting and light, which has been known in fine arts for centuries. The effect on the observer of photorealistic 3D reconstructions in video games and in medical imaging can be largely explained by the knowledge of 3D techniques in drawings and paintings. Keywords: 3D-reconstruction, Anatomy, Fine arts, Radiology, Video Games

Objective: To compare the accuracies among three oral implant surgical techniques: freehand (FH), static computer-assisted implant surgery (sCAIS), and robotic computer-assisted implant surgery (rCAIS). Methods: The polyurethane and bovine femur implant models were fabricated, and 126 and 96 implant sites were designed on them. The implant sites were divided into three groups: FH, sCAIS, and rCAIS, according to the implantation method. The deviation between the actual implant position and the planned position was analyzed and compared by cone beam computed tomography. Results: In the polyurethane model test, the entry deviation, entry-level deviation, apical deviation, apical level deviation, and angle deviation in sCAIS and rCAIS groups were significantly reduced compared with those in the FH group (P<0.05). No significant differences were observed in all kinds of deviations between the sCAIS and rCAIS groups (P>0.05). In the bovine femur model test, the entry deviation, entry-level deviation, apical deviation, apical level deviation, and angle deviation in both sCAIS and rCAIS groups were significantly reduced compared with those in the FH group (P<0.05). No significant differences were observed in all kinds of deviations between the sCAIS and rCAIS groups (P>0.05). Conclusion: This in vitro study shows that the rCAIS technique is superior to the freehand, but has the same accuracy as the sCAIS. Keywords: robotic computer-assisted implant surgery, accuracy, dental implants, freehand, static computer-assisted implant surgery

Aim: To develop a periodontal disease prediction software and a patient-based gingival recession simulator for clinical practice aiming at improving oral hygiene motivation of patients with periodontal problems. Materials and Methods: Periodontal Disease Prediction (PDP) software has three components: a) Data Loading Window (DLW) b) Three-Dimensional Mouth Model (3DM) and c) Periodontal Attachment Loss Indicator (PLI). Demographic and clinical examinations of 1057 volunteers were recorded to DLW. An unsupervised machine learning K means clustering analysis was used to categorize the data obtained from the study population and identified the periodontal risk groups. An intraoral scanner was utilized to capture direct optical intraoral data of a patient and transferred to the 3DM. The intraoral model went under two algorithm steps for obtaining a recessed model. First, gingival curves separating gingiva and tooth were extracted using a Dijkstra’s algorithm. Limit curves determining boundaries of recessed regions in the intraoral model were then obtained using gingival curves. Results: Study participants were divided into three different periodontal risk categories defined as low risk (n=462), medium risk (n=336) and high risk (n=259). Gingival curves separating gingiva and tooth were extracted, and recessed models were obtained given inputs for the expected amount of recession via the proposed method. Furthermore, the user can also demonstrate the gingival recession gradually via the slider method attached to the developed programme. Conclusions: User-friendly computer-based periodontal risk estimation tool and patient-specific gingival recession simulator was developed and presented for clinical usage of dentists. Keywords: Computer-aided design, Dijkstra's algorithm, Gingival recession, Oral hygiene motivation, Periodontitis

Aim: To assess the agreement rates of dental records derived from intraoral scan-based digital three-dimensional models (3DM) and 3DM + panoramic radiographs (3DM+PAN-X) compared to clinical findings. Materials and Methods: Based on the 3DM/3DM+PAN-X of 50 patients undergoing supportive periodontal therapy (SPT), ten remote raters (inexperienced in using IOS or 3DM) assessed for each site of the dental scheme (32 sites) whether a tooth was missing (M), filled (F), restoration- and caries-free (H), replaced by an implant (I) or decayed (D). Remote records were compared to the clinical reference record of each patient at tooth-level. The clinical records were assessed by an experienced dentist who supplemented the clinical findings with information from available radiographs and the patient records to define the clinical reference record. Results: The agreement-rates for 3DM/3DM+PAN-X at tooth-level are: M: 93%/94%, F: 84%/88%, H: 92%/92%, I: 65%/96%, D: 29%/29%. The overall agreement-rate is 88% for the 3DM-based dental records (14093 of 16000 entries true) and 91% for 3DM+PAN-X (14499 of 16000 entries true). Using 3DM for dental record assessment, posterior teeth had higher odds of correct findings compared to anterior teeth (upper jaw OR=2.34, lower jaw OR=1.27). Conclusions: The remote detection of healthy, missing and filled teeth and implants by raters inexperienced in using IOS or 3DM shows a high agreement-rate with the clinical findings. The additional evaluation of PAN-X increased the agreement-rate significantly for implants. Thus, the remote assessment of dental records using 3DM+PAN-X has a high accuracy when applied in SPT-patients with low caries activity. Keywords: dental record remote assessment, digital dentistry, digital imaging, full-arch impression, intraoral scanners, supportive periodontal therapy

Aim: The aim is to record the surface roughness of monolithic chairside CAD/CAM zirconia materials to evaluate the influence of milling speed on the ability to achieve a clinically desirable surface. The null hypothesis is that there is no significant difference in the surface roughness of different zirconia materials based on the speed of subtractive milling. Materials and Methods: All test samples were milled from four different monolithic CAD/CAM zirconia blocks including CEREC Zirconia (Dentsply Sirona), CEREC Zirconia+ (Dentsply Sirona), CEREC MTL Zirconia (Dentsply Sirona), and Katana Zirconia (Kuraray Noritake). Four different dry milling speeds, Super Fast/Good, Super Fast/Very Good, Fast, and Fine were used to dry mill the specimens in a CEREC Primemill (Dentsply Sirona). A 3D measuring laser microscope (OLS4100 LEXT by Olympus) was used to measure surface roughness. Results: An Analysis of Variance (ANOVA) was used to analyze the surface roughness data for each material and milling speed. There was a significant difference for milling speed (p < 0.05) but not between zirconia materials (p > 0.05). Conclusion: Based on the limitations of this study, the milling speed influenced the surface roughness of dry milled and sintered zirconia with slower speeds resulting in smoother surfaces. The largest improvement in surface roughness occurred between Super Fast and Fast milling with a smaller incremental improvement in surface roughness with Fine milling for the Primemill. All recorded surface roughness values are within the expected range of values to be able to efficiently hand polish a clinically acceptable surface finish. Keywords: CAD/CAM, CEREC, mill speed, Surface Roughness, zirconia

Aim: To evaluate the failure rate of palatal computer-guided miniscrews, placed in paramedian and parapalatal regions for orthodontic purposes. In addition, to investigate the presence of a learning curve using computer guided miniscrew insertion, and to evaluate the peri-implant soft tissues response at 2-, 6- and 12- month follow-ups. Materials and Methods: 202 palatal computer-guided miniscrews were inserted in 78 subjects for orthodontic purposes. A surgical guide was designed after planning the appropriate insertion sites on three-dimensional images created by the fusion of cone-beam computed tomography (CBCT) and digital dental model images. The devices were disassembled monthly to perform the percussion test and to evaluate the mobility of each miniscrew. To determine the presence of a learning curve, the time of miniscrew failures and the number of surgeries were evaluated. Bleeding on probing (BOP) and probing pocket depth (PPD) were recorded for each miniscrew, at 2- (T0), 6- (T1), and 12-month follow ups (T2). Results: An immediate failure rate of 4.95%, due to lack of primary stability immediately following miniscrew insertion, was recorded, with statistically significant higher failure rate of parapalatal miniscrews (P= 0.00). Miniscrew failure occurred at random time, with an absence of a learning curve. The BOP (mean: 3.13%) and PPD (mean: 1.68mm) measurements remained stable over time. Conclusions: Computer-guided miniscrew insertion in the palatal vault showed a low failure rate without a determined learning curve to obtain predictable results and with long-term stability of peri-implant soft tissues indexes. Keywords: computer-guided surgery, failure rate, Orthodontics, skeletal anchorage, TADs

Aim: To evaluate the accuracy and reproducibility of real and virtual occlusal contact points in implant-supported, fixed complete dentures. Materials and methods: The study included 19 participants using mandibular interim complete-arch fixed prosthesis supported by 3 or 4 implants as opposed to conventional removable complete dentures. At installation, an examiner installed the prostheses and verified the occlusal contact points through 2 methods: recording the real contact points with carbon paper (RC) followed by occlusal photography and intraoral scanning (VC) to record the virtual contact points to obtain a screen print of the software. Then, the two images were randomized to determine the order to be inserted into Microsoft PowerPoint for blind and paired evaluation. The independent variables consisted of the distribution of occlusal contacts points (qualification through pre-defined scores based on the position of the contact points on the surfaces of the teeth) and the reproducibility of the methods by verifying the number of occlusal points. For this, a descriptive analysis was used to evaluate the distribution of occlusal contacts points and the Wilcoxon test for the reproducibility of the occlusal contact points between the methods (p<0.05). Results: The methods had 100% and 73.6% real and virtual occlusal contact points, respectively, which is considered clinically excellent. There was no significant difference regarding the reproducibility of the methods by the number of occlusal contact points (RC: x̅13.32; VC: x̅13.68; p=0.715). Conclusion: The use of the tested intraoral scanner can be an easy and fast tool for studying and mapping the occlusion, and storing data for future treatment, with the conventional method being the preferred method for performing the occlusal adjustment. Keywords: implant-fixed dental prosthesis, dental occlusion, edentulous, jaw, Occlusal adjustment, three-dimensional imaging

Aim: Even though today, many fields in dentistry allow digital processes, analogue procedures are still widely used. This cross-sectional pilot study aimed to survey insights on the digitalisation of dental practices using the example of Hesse. Materials and Methods: Between April and June 2022, 4840 active practicing dentists registered by the State Dental Association of Hesse were invited via e-mail to fill out an online questionnaire regarding their technical requirements in dental practice, dental treatment procedures, and attitude towards digitalisation in dentistry. Demographic questions were asked. Besides descriptive statistics, correlations were analyzed (P < 0.05). Result: Questionnaires of 937 dentists (279 female, 410 male, four inter/divers, 244 no answer; mean age of 51.4 ± 10.4 years) were examined representing a respond rate of 19.36%. In the area of practice administration and dental radiography, the majority of the dentists surveyed is already working digitally, which is predominantly assessed as a positive development. Already one third of the respondents state that they use an intraoral scanner for dental treatments, but the indication is mainly limited to smaller restorations. However, many dentists rate the use of social media accounts and telemedicine rather negative. Conclusion: Within the limitation of this pilot study, many processes especially in dental treatments are still analogue. However, 60% of the participants plan digitalisation of their dental practices within the next five years, which indicates a clear shift from analogue to digital dentistry. Keywords: Analog-Digital Conversion, CAD/CAM, Dental Practice Pattern, Digital Technology, Intraoral Scanner, Organisation and Administration, Real World Data on Dentistry, Surveys and Questionnaires

Aim: There is an ongoing debate about the benefits of the facebow and individual articulator settings in prosthodontics when compared to simpler methods. This study aims to determine whether the implementation of novel algorithmic articulator concepts may be an alternative to avoid dynamic interference contacts during the design process of fixed posterior restorations and to which extent the occlusal morphology of the restoration is affected. Materials and methods: From a chairside CAD database, a total of 50 clinical patient cases documenting 61 planned fixed restorations in the posterior tooth region were selected. A common CAD software was used for the automated knowledge-based design process. When designing the restorations, functional concepts including the pure static occlusion, average articulation, 3 different articulator settings as a control, and a combination of a broad range of articulation parameters (full range dynamic articulation) were applied. The resulting dynamic contact points were both compared visually and metrically with a monitoring software. Results: There is a highly significant difference in avoiding dynamic interference contacts when applying the full range dynamic articulation in comparison to the pure static occlusion (p<0.001) and the average articulation (p<0.001). Furthermore, the superimposition revealed that the surface of the restorations showed nearly no visual morphologic changes after virtually grinding-in the interpenetrating contact points. Conclusion: The full range dynamic articulation can be used for the design of small fixed posterior restorations to avoid most dynamic interference contacts, without the need for determining individual parameters for each patient. Keywords: average articulation, CAD/CAM, facebow, full range dynamic articulation, virtual articulation, virtual FGP

Aim: This randomized controlled clinical study focused on graft volume alterations after sinus floor augmentation with a deproteinized bovine bone mineral (DBBM, Geistlich Bio-Oss®), deproteinized porcine bone mineral (DPBM, THE GRAFT®) or a biphasic calcium phosphate (BCP, OSOPIA®). Material and Methods: 28 patients with edentulous situations in the posterior maxilla with less or equal to 5 mm of residual bone height received a two- staged external sinus grafting procedure with DBBM, DPBM or BCP. CBCT scans were performed prior surgery (CBCT1), directly after surgery (CBCT2) and after a healing period of 4-6 months prior implant placement (CBCT3). CBCT scans were used to analyze volumetric alterations of the sinus grafts by virtual 3D model matching of CBCT1- CBCT2 (situation after sinus grafting) and CBCT1 and CBCT2 (situation prior implant placement). Results: The volume of the bone graft in the maxillary sinus (volume (VOL%) directly after grafting rated as 100%) was stable after the healing period in the DBBM (VOL%: 103±4%) and the PBBM groups (VOL%: 112± 23) with no statistically significant differences concerning 3D measurements. In the BCP group, the grafted volume declined to 66± 25% (VOL%), statistically inferior to the DBBM and DPBM groups. Conclusion: Concerning bone graft stability/ 25 volume DBBM and DPBM show comparable outcomes. Due to resorption, BCP showed inferior bone graft volume after healing (statistically significant) compared to DBBM and DPBM. Keywords: 3D evaluation, Bone substitute, CBCT, Sinus grafting, volumetric stability

Aim: To evaluate and compare the marginal adaptation and fracture resistance of resin matrix ceramic crowns fabricated using 3-dimensional (3D) printing and computer aided design/computer aided manufacturing (CAD/CAM) milling technology. Materials and Methods: Thirty extracted human maxillary first premolars were prepared to receive crown restorations and grouped into 3 groups according to 3 different crown materials (n = 10): VE: teeth restored with milled Vita Enamic, CS: teeth restored with milled Cerasmart 270 and VSC: teeth restored with 3D-printed VarseoSmile Crown Plus. Marginal analysis was performed with the aid of a digital microscope at (230x) magnification, both before and after cementation with self-adhesive resin cement and analyzed with Image J analysis software. The fracture loads for each sample were then recorded using a universal testing machine in a single load-to-failure test up until the crowns failed. Results: The lowest marginal gap values were recorded for VSC before (8.03 μm) and after (15.07 μm) cementation with significant difference compared to the other crown materials (p <0.05), while the differences between the milled groups were non-significant both before, (CS (11.35 μm) and VE (11.86 μm)), and after cementation, (CS (20.01 μm) and VE (21.08 μm)). In terms of fracture resistance, VE recorded significantly lower fracture load values (727.8 N) (p <0.05) than the crowns fabricated from CS (1213.8 N) and VSC (1181.5 N), which showed no statistically significant differences between each other. Conclusion: 3D printed definitive crowns outperformed CAD/CAM milled crowns in terms of marginal adaptation, along with comparable fracture resistance values. Keywords: 3D printing, CAD/CAM milling, Fracture resistance , Marginal adaptation , Resin matrix ceramics

Aim: The adjustment and transfer of a stable occlusion can be a major challenge in prosthetic rehabilitations. The aim of this study was to assess a non-invasive treatment option for complex prosthetic rehabilitations and occlusal analyses using 3D-printed restorations clinically. Materials and Methods: Eleven patients received a partial or complete rehabilitation with the aid of 3D-printed restorations (n=171). After 12 months of clinical service, all restorations were analyzed using the United States Public Health Service (USPHS) criteria. Results: The 12-month clinical data revealed that 3D-printed restorations showed a survival rate of 84.4%. Complications occurred mostly regarding the anatomical form (7%) or marginal integrity (6AC%) and were consequently rated “Charlie” or “Delta.” Color stability and color match of 3D-printed restorations were rated “Alpha” in 83% and 73%, respectively, of all restorations. Marginal inflammation was rated “Alpha” in 89% of all restorations. An excellent surface texture and no secondary caries or postoperative sensitivities (100%) were observed. Conclusions: 3D-printed restorations might be an alternative treatment option for initiating complex prosthetic rehabilitations. Technical complications rarely occurred. Biological complications did not occur at all. The color stability showed promising results after 12 months of clinical service. However, the results should be interpreted with caution. Long-term results with a high number of restorations should be awaited. Keywords: 3D-printing, additive manufacturing, CAD/CAM, color stability, in vivo, wear behavior

Learning tooth preparation techniques and the finesse required is an important part of preclinical dental education. Being able to practice surgical skills without loss of Frasaco® teeth while being provided with performance analysis data is a boon to students and educators. We investigated the combination of haptics-enhanced virtual reality (Simodont®) and conventional phantom head practice in a preclinical dental course, evaluating the students’ performances and perceptions. Forty students were randomized into two groups: Group One began within a VR-haptic setting while Group Two worked with Frasaco® teeth. Halfway through the course the scenarios were switched. A crown preparation test on Frasaco® teeth was conducted at the end of the course. Students’ performances and satisfaction were assessed anonymously. Analysis of the students’ performances included clinical metrics (occlusal and axial reduction, convergence angle, damage to adjacent teeth). The perceived usefulness of VR-haptic and phantom head simulations was assessed. In Group One, the tooth preparation metrics were more in line with the requested parameters compared to Group Two. All students ranked VR-haptics highly regarding manual dexterity improvement. In conclusion, this study shows that by combining VR-haptics with conventional dental procedures, it is possible to improve important preparation metrics in fixed prosthodontics tooth preparation. Keywords: dental training, manual dexterity, practice-based learning and improvement, survey, VR-haptic simulation

Objectives: Virtual Reality (VR) technologies can be used as a content-delivery system for the purposes of both entertainment and education. Remote and digital education has become ever so important in a world where global disruptive events such as pandemics and natural disasters can define access to a face-to-face learning environment. An important aspect of VR technologies for dentistry is the creation of digital 3D models. The primary of this review was to answer the focused research question, “What software techniques are used in the creation of digital 3D models for use in dental education.” Methods: This study systematically evaluates current software and techniques used for creating digital 3D models in dental education using the Preferred Reporting Items for Systematic Reviews (PRIMSA). Results: The search strategies did not find any studies specific to the creation of dental-related 3D models. Therefore, this study for the first time provided an overview of common techniques of 3D model fabrication is discussed. Further some examples of methods of creating 3D models relevant to dentistry such armamentarium and anatomical oral structures have been discussed in considerable detail. Conclusion: The creation of 3D modelling is a rapidly evolving field with software updates and new programs being continually released. This work highlights fundamental lack of published work in the creation of 3D dental models for educational applications. Keywords: 3D modelling, dental education; , dentistry, digital modelling, Virtual Reality

Aim: New technologies such as tactile robots and artificial intelligence are about to find their way into clinical practice in dentistry and may contribute to the improvement of oral health care in the future. In this study we hypothesized that a collaborative, tactile robot programmed by a dental student removes interproximal artificial plaque as effectively as a human operator in an in vitro pilot trial. Material and Methods: Model teeth were fully covered with artificial plaque and set into phantom jaws. First, a robot was programmed by a dental student to perform interproximal cleaning with an interproximal brush. Second, teeth were covered with artificial plaque again and the dental student performed the interproximal cleaning manually. Both experiments were repeated five times. Residual plaque was measured with binary pictures. Surface coverage was reported and comparison of methods was performed with significance defined at a= 0.05. Results: No statistically significant difference was found in the cleaning result between the robot and the human operator. Conclusion: The results of this in vitro pilot study indicate that a tactile robot with integrated artificial intelligence programmed by a dental student can perform interproximal cleaning as effectively as the dental student. Practical lmplications: In the future, the use of robot assistants to support oral hygiene, e.g., in patients with reduced motor skills or impaired vision may be further investigated. Keywords: Dental robots, Dentistry, Dentronics, Human-machine-interaction, Interdental brush, Interdental cleaning, Interproximal, Oral hygiene, Robotics

Aim: The purpose of this systematic review and meta-analysis is to evaluate the marginal adaptation of single unit full coverage lithium disilicate fixed dental restorations fabricated with the conventional heat pressed technique and the digital CAD/CAM workflow. Materials and Methods: This study is according to the Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) statement. study research was conducted in MEDLINE via PubMed and Cochrane Library databases together with a hand search of studies published until June 2022. The search terms were combining suitable Medical Subject Headings (MeSH terms) together with free text words in single or multiple conjunctions. A modified methodological index was used to assess the risk of bias of the included studies. A random effect model was applied to pool the effect estimates, and further assessment of the heterogeneity across studies using the Q test and the I2 metric was conducted. All statistical analyses were performed using Rstudio software, version 4.1.2, using the “meta” package. Results: The electronic search and hand search identified 51 articles. Eighteen met the inclusion criteria and were included in the systematic review, 17 of which were in vitro and only one was an in vivo study. However, 17 of the initial 18 could be included in the meta-analysis, due to lack of statistical data in one of the in vitro studies. Statistical analyses were conducted by using the Rstudio software program. Meta-analysis was performed with the random effects model (α=.05). No statistical difference was found between the two fabrication methods (p-value=0.49). Conclusions: Although the mean marginal adaptation of lithium disilicate single crowns was found to be better with the heat-pressed technique, there was no statistical significance with the CAD/CAM fabricated restorations and both resulted in a clinically acceptable result. Nonetheless, more clinical studies are needed for safer conclusions. Keywords: all-ceramic restoration, CAD/CAM, dental ceramics, glass-ceramics, lithium disilicate crown, marginal fit, single crown

Artificial intelligence (AI) based systems are used in dentistry to make the diagnostic process more accurate and efficient. The objective of this study was to evaluate the performance of a deep learning program for detection and classification of dental structures and treatments on panoramic radiographs of pediatric patients. In total, 4821 anonymized panoramic radiographs of children aged between 5 and 13 years old were analyzed by YOLO V4, a CNN (Convolutional Neural Networks) based object detection model. The ability to make a correct diagnosis was tested samples from pediatric patients examined within the scope of the study. All statistical analyses were performed using SPSS 26.0 (IBM, Chicago, IL, USA). The YOLOV4 model diagnosed the immature teeth, permanent tooth germs and brackets successfully with the high F1 scores like 0.95, 0.90 and 0.76 respectively. Although this model achieved promising results, there were certain limitations for some dental structures and treatments including the filling, root canal treatment, supernumerary tooth. Our architecture achieved reliable results with some specific limitations for detecting dental structures and treatments. Detection of certain dental structures and previous dental treatments on pediatric panoramic x-rays by using a deep learning-based approach may provide early diagnosis of some dental anomalies and help dental practitioners to find more accurate treatment options by saving time and effort. Keywords: artificial intelligence, deep learning, oral diagnosis, panoramic radiography, pediatric dentistry

Aim: To investigate the effect of using different materials for the fabrication of implant abutments and crowns on the mechanical behavior of implant-supported single crowns after artificial aging. The materials were tested in different combinations to reveal whether using stiff or resilient materials as an abutment or a crown material might influence the fracture strength of the whole structure. Materials and Methods: A total of 40 implants (blueSKY, bredent GmbH & Co. KG) were restored with identical custom-made CAD/CAM abutments milled out of lithium disilicate or ceramic-reinforced PEEK and were divided into 5 test groups (n = 8 each). Forty crowns made of three different materials (zirconia, lithium disilicate, and ceramic-reinforced PEEK) were used to restore the abutments. Specimens were subjected to mechanical load up to 1,200,000 cycles in a chewing simulator (Kausimulator, Willytech) with additional thermal cycling. The surviving specimens were subjected to quasi-static loading using a universal testing machine (Z010, Zwick). Results: PEEK abutments with zirconia crowns showed the highest median failure load (3890.5 N), while PEEK abutments with lithium disilicate crowns exhibited the lowest (1920 N). Fracture and deformation occurred in both crowns and abutments. Conclusion: The failure load of the restorations was influenced by the material of the abutment and the crown. Restoring PEEK abutments with zirconia crowns showed a high failure load and no screw loosening. Keywords: CAD/CAM, Custom-made implant abutment, implant abutment, Lithium disilicate, PEEK, Zirconia

Aim: To determine the 3-year clinical and dimensional change of the soft tissue following implant placement in healed sites before and after loading with either customized or conventional healing abutments. Materials and Methods: Premolar/molar implants were immediately loaded with either provisional and customized abutments without finishing lines according to principles of the Biologically Oriented Preparation Technique (BOPT), test group, or conventional healing abutments, control group. Three months later, the definitive crowns were fabricated. Primary outcomes (changes in the soft tissue) and secondary outcomes (adverse events) had been registered. Result: Fifty out of 87 subjects originally included were finally selected for this retrospective analysis: 23 in the test and 27 in the control group. During the first days after surgery 2 adverse events of mucositis, one for each group, occurred. A Few technical complications such as unscrewing 4 screw-retained crowns were recorded. A significant increase in the alveolar width was observed in both groups (test = +2.5±0.5mm, and control = +1.0±0.9mm). The widths appeared to not be merely changed from 3 months to 3 years in both groups. There were no significant differences regarding the width of the keratinized mucosa measured at baseline and after follow-up. Jemt papilla index showed a higher increase in the test group compared with that of the control group. Conclusion: Within 3 years of the follow-up period, peri-implant soft tissue outcomes of single, immediately loaded implants with customized healing abutments showed better results in terms of thickness and width when they were compared with those of the conventional group. Side effects count (mucositis and dehiscence) appeared to be very similar between the two groups. In addition, customized healing abutments led to significant augmentation of the alveolar width more than twice that registered in the conventional group. Keywords: anatomical cap, customized abutment, dental abutment, dental implant, implant placement

Aim: The digital workflow used to manufacture an adjusted oral splint will be demonstrated in a patient case. Materials and Methods: A 25-year-old female patient presented for management of her bruxism. Therefore, an adjusted oral splint was manufactured. A computer-aided motion analysis of the patient was conducted (JMA Optic, Amann Girrbach) and full-arch scans of the maxilla and mandible, a biocopy of the maxilla with bite fork as well as buccal scans of the centric jaw relation (Primescan, Dentsply Sirona). The jaw relation was determined beforehand by ballistic closing on a chairside fabricated anterior jig. The digital construction of a Michigan splint took place in the laboratory. The design was nested and milled from a polymethyl methacrylate (PMMA)-containing blank (CLEARsplint Disc, Astron Dental Corporation). Result: The oral splint was inserted into the patient’s mouth and checked to ensure a tensionfree fit. The static and dynamic contact relationship was checked. During the follow-up visit, the patient reported an improvement in tension in the masticatory muscles. Conclusion: The procedure described allows for an adjusted oral splint to be manufactured in a purely digital workflow. Keywords: bruxism, centric relation, mandibular movement recordings, oral splint, therapy

Occlusal splint is a commonly prescribed dental appliance in the dental office for the management of bruxism or temporomandibular disorder. The use of digital dental technology facilitates fabrication of this therapeutic device. The digital technology improvement had helped in designing and producing occlusal splints that show better precision and accuracy, ease of manufacturing in terms of time-consuming and materials, in addition to the option of simple and straightforward duplication process. This technical report describes the digital workflow steps that need to be followed to design an occlusal device in a fully digital protocol. Maxillary and mandibular models’ scans were acquired in centric relation, and a virtual 3D occlusal device was designed using a free, open-source 3D modelling software program. Keywords: 3D dentistry, Autodesk Meshmixer, digital dentistry, Occlusal splint, open source software

Aim: Aim of this study comprised the software-supported evaluation of measurement accuracy between cone-beam computed tomography (CBCT) and panoramic radiographs in the assessment of the periodontal bone level in patients with periodontitis and comparison with clinical periodontal parameters. Material and methods: Twenty patients with severe periodontitis (stage III-IV) were evaluated clinically and radiographically (panoramic and CBCT). Diagnostic interpretation comprised three blinded investigators with different levels of experience. Specific software-basing measurement procedure evaluated radiological distances for the mesial, central, and distal bone levels on the oral and vestibular sides of the teeth investigated and furcation upper and lower boundary. Jaw localization, anatomical region-of-interest, the number of roots and experience of the observers were evaluated. All measurements were carried out twice by the same observers within a 6-week interval. Results: Slightly higher measurement deviations (SD) in the range of 0.47 (0.40) mm were found for CBCT evaluation compared to panoramic imaging. Pearson correlation analysis showed statistically strong positive correlation for the mesial and distal aspects, moderate positive correlation was found for the investigated furcations between both radiographic modalities. Compared to the clinical reference, the mean total error of measurement (SD) was larger for panoramic imaging (0.66 (0.48) mm) than CBCT (0.27 (0.08) mm) for all three observers. Conclusions: Software-supported CBCT analysis delivers better diagnostic information about the bony periodontal conditions of the patient compared to two-dimensional radiographs. However, it remains unclear if these additional information lead to better periodontal outcomes. Keywords: alveolar bone losses , cone-beam CT, diagnostic imaging, dimensional measurement accuracy, Periodontitis, radiography

Aim: The aim of this study was to evaluate the segmentation accuracy of dentition testing four free-source semi-automatic software. Materials and methods: A total of 20 cone-beam computed tomography (CBCT) were selected to perform semi-automatic segmentation of maxillary and mandibular dentition. The software tested were Invesalius, ITK-Snap, 3D Slicer and Seg3D. Each tooth model was also manually segmented (Mimics software) and set as the gold standard (GS) reference of the investigation. A specific 3D imaging technology was used to perform the superimposition between the teeth models obtained with semi-automatic software and the GS model, and to perform the surface-to-surface matching analysis. The accuracy of semi-automatic segmentation was evaluated calculating the volumetric mean differences (mean bias and limits of agreement) and the percentage of matching of the tooth models compared to the manual segmentation (GS). Qualitative assessments were performed using color-coded maps. All data were statistically analysed to perform software comparisons. Result: Statistically significant differences were found in the volumetric and matching percentage data (p < 0,05). Invesalius was the most accurate software for 3D rendering of the dentition with a volumetric bias (Mimics) ranging from 4,59 mm3 to 85,79 mm3; instead, ITK-SNAP showed the higher volumetric bias, ranging from 30,22 mm3 to 319,83 mm3. The dis-matched area was mainly located at the radicular region of the teeth. Volumetric data showed excellent inter-software reliability with coefficient values ranging from 0,951 to 0,997. Conclusio: Different semi-automatic software algorithms could generate different patterns of inaccuracy error in the segmentation of teeth. Keywords: 3D rendering, CBCT, cone-beam computed tomography, digital dentistry, digital orthodontics, oral surgery, orthodontics, segmentation

Aim: A total occlusal convergence angle φ of 6° is a typical crown preparation requirement. It was shown that it is hard to achieve clinically. The present study aimed to compare ability of students to judge different steepnesses including a -1° undercut of prepared canines and molars under clinical conditions with different analogue tools. Materials and methods: The complete dentures of a patient were duplicated without the teeth 16, 23, 33, 46. For each of these gaps, 6 crown stumps were milled with φ/2 = -1°, 3°, 6°, 9°, 12° and 15°, each of which was insertable using mini-magnets. 48 students each from the 1st, 6th and 9th semester estimated these angles intraorally with various aiding tools: In addition to basic dental instruments, a parallelometer mirror, an analogue clock dial with a 6° visualization and a scale of tooth stumps with φ/2 between -1° and 15°. Results: The widely demanded 3° were hardly recognized, but assumed to be steeper or even undercut. In contrast, the -1° divergent stump walls were predominantly estimated as parallel-walled or slightly conical. With increasing taper, the stumps tended to be classified as steeper, i.e. "better". The additional tools did not result in a general improvement of the estimation performance. Students from higher semesters did not achieve better results. Conclusion: We question the objectivity of an exclusively visual assessment of crown stump taper. It appears, that dental training should at least focus on avoiding undercuts as minimal prerequisite for an accurate intraoral scanning procedure. Digital control of the preparation angle by an intraoral scan and immediate clinical implementation of these results could help to produce appropriate preparations. Keywords: crown stumps, dental students, intraoral estimation, preparation angle, visualization tools

Aim: Quantitative dental plaque evaluation is necessary for clinical and scientific work. This study aimed to examine the reliability of this 3D image analysis method by digitally analysing the colour 3D images obtained from an intraoral scanner, and then detecting and quantifying the plaque information and comparing it with the clinical examination results. Materials and methods: A total of 140 teeth from 5 subjects with a standard dentition were enrolled in this study, and plaque examination was performed at two different stages: after 24 hours without oral hygiene (T1) and after habitual brushing (T2). At each time point, the Quigley-Hein plaque index of each tooth surface was recorded separately, followed by colour 3D images obtained using an intraoral scanner, and image analysis and calculation using Geomagic Wrap 2021. Results: It was found that the percentage of plaque staining area calculated from the 3D image analysis correlated well with the plaque index recorded during the clinical examination: the Spearman correlation coefficients were 0.9136 and 0.9061 (p<0.001) for all tooth surfaces at T1 and T2, respectively. The measurements of the three investigators were in good agreement, with intraclass correlation coefficients of 0.989 and 0.992 (P<0.001) for the vestibular and lingual surfaces at T1, and 0.964 and 0.983 (P<0.001) for the vestibular and lingual surfaces at T2. Conclusion: In this study, we initially developed a digital 3D evaluation system of dental plaque suitable for research and clinical practice and demonstrated its reliability. Keywords: 3D image processing, dental plaque, intraoral scanner, plaque index, quantitative evaluation

Purpose: Endodontically treated teeth are more susceptible to fractures than vital teeth because of significant coronal and radicular dentin loss during endodontic therapeutic procedures. The objective of this study was to estimate and compare the influence of length and post type on the fracture strength of endodontically treated maxillary central incisors. Material and methods: In this in vitro study, sixty extracted human maxillary central incisors were decoronated 2 mm above the cemento-enamel junction.They were selected and subjected to standard endodontic treatment ,resulting in preparation with lengths of 5 mm (group 5mm),7,5 mm (group 7,5 mm) and 10 mm (group 10mm). Each group was randomly divided into 2 subgroups according to the post type , zirconia and fiber post. After appropriate surface treatment,they were cementet with resin adhesive cement and restored with zirconia crowns. Thermocycling (5 -55°C, 60 seconds, 1500 cycles) was performed after cementing the zirconia crowns on each tooth. Prepared samples were subjected to compresive static load of 0.5mm / min, at an angle of 130° to the long axis of the roots, using Universal Testing Machine (Matest ) at an cross head speed of 0.5 mm / min, until fracture.The significance of the results was assessed using 2-way ANOVA and the Tukey-Kramer test (α=0.05) Results:The ANOVA analysis indicated significant differences (P<0.05) between the groups. Tukey test revealed no significant difference among the zirconia posts of 5-mm length (26.5 N ±13.4) 7,5-mm length (25.2 N ±13.9), and 10-mm length (17.1 N ±5.2). Also, in the fiber post group, there was no significant difference when posts of 7.5-mm length (13.4 N ±11.0) were compared with the 5-mm (6.9 N ±4.6) and 10-mm (31.7 N ±13.1) groups. The 10-mm long post displayed superior fracture strength, and the 5mm-long post showed significantly lower mean values (P<0.001). Conclusion: The fracture strength of zirconia posts (5-mm and 7,5- mm length)was found to be significantly higher than those of fiber posts (5-mm and 7,5- mm length). The 10-mm long fiberpost group demonstrated significantly higher values of fracture strengths and the 5-mm long fiberpost group showed the lowest values for the force resulting in root fracture; these groups were significantly different from each other (P<.001).The fracture strength analysis with Universal Testing Machine is the only method that enables us to estimate the differences between zirconia and fiber posts with different lengths on endodontically treated teeth. Keywords: Endodontically treated teeth, fiber post, fiberpost, fracture strength, universal testing machine, zirconia post

Aim: This study aimed to evaluate the intaglio surface trueness and fit of zirconia crowns depending on the different machining strategies used with the CEREC system. Materials and methods: Thirty duplicate tooth models for a single zirconia crown were randomly assigned to the three groups (n = 10) according to the machining mode used for fabrication: grinding, wet milling, and dry milling. The scan data of the final crowns were compared to their design data to evaluate the intaglio surface trueness. The marginal and internal fits were evaluated using the cross-sectional method. The time required for the machining and sintering processes was measured for each group. Result: The wet milling group showed better trueness (RMS, 13.8 ± 1.0 μm) than the grinding and dry milling groups (p < 0.001). The marginal gap was greater in the grinding group (58.6 ± 28.9 μm) than that in the wet milling and dry milling groups (p < 0.001). The dry milling group required the shortest time for the manufacturing process. Conclusion: All machining modes fabricated crowns with a clinically acceptable trueness and fit. However, the dry milling mode was advantageous for the chairside CAD/CAM system with respect to time efficiency. Keywords: 3D printing, CEREC, comparative 3D analysis, dry milling, grinding, marginal gap

Aim: The accuracy and reproducibility of occlusal contact points visualized by articulation foil (AF) should be investigated and then compared with contact points calculated by three different intraoral scanners (IOS). Materials and Methods: Occlusal contact points were visualized on a standardized resin dental tooth model using AF 50 times with maximum intercuspidation and constant biting force. The points were photographed from a vertical position above the model and superimposed on a screen in order to test the reproducibility of the model. This was followed by fifty-fold repetition by scans and computation of the occlusal contact points by the respective IOS CS3600 (CS ScanFlow v.1 4th version), TRIOS 3 (Basic 2019), and CEREC Omnicam (Software version 5.1). The results of computation were captured with screenshots, and were then overlaid with the photographs of the AF. The image overlays were classified into five categories: category 1 = total overlapping of contact points, category 2 = partly overlapping, category 3 = adjacent contact points without overlapping, category 4 = contact points identified only by IOS, category 5 = contact points identified only by AF. All data were statistically evaluated (95% CI). Results: In total, the visualisation of the occlusal contact points by the IOS were significantly less accurate and less reproducible compared to the AF (p < 0.05). In the combination of sensitivity and accuracy, the TRIOS3 by 3Shape showed significantly better results than the other IOS tested (p < 0.05). Conclusion: In vitro, AF displayed a significantly more accurate visualisation of the occlusal contact points than IOS. Keywords: articulating foil, digital intraoral scanners, occlusion, occlusal contact point, reproducibility, visualisation