International Journal of Computerized Dentistry, Pre-Print

In view of the rapid developments in digital dentistry (such as digital workflow and CAD/CAM processes), questions arise regarding digital occlusion, including the possibilities of occlusal analysis. This raises questions about definitions and terminology: What do we mean when we talk about occlusion in the context of digitization, especially in the case of digital models, and what are the potentials of digital occlusal analysis? Initial thoughts on this important topic will be presented in preparation for an upcoming guideline. Keywords: digital patient, digital articulator, Digital occlusion, digital occlusion analysis, virtual articulator

Purpose: This in vitro study investigates the accuracy of digital impressions taken with different dental materials. It compares the scan accuracy and trueness of a handheld scanner operated by an experienced clinician, a handheld scanner operated by a robotic arm, and a tabletop scanner. By measuring the number of triangles, average degree, and vertices within the three groups, conclusions about the accuracy of different scanning methods on digital models can be drawn. Materials and Methods: Standard-sized models made from various dental materials were used. The scanners tested included a tabletop scanner, a handheld scanner operated by an experienced clinician, and a handheld scanner operated by a robotic arm. The number of triangles, average degree, and number of vertices were recorded and compared. Statistical analysis was performed to identify significant differences between the groups. Results: The tabletop scanner produced the fewest triangles in the digital model, while the handheld scanner operated by the experienced clinician had the most. Significant differences were found in the number of triangles, average degree, and vertices among different dental restorations. The handheld scanner used by the experienced clinician produced the most accurate and true digital model, followed by the robotic arm-operated handheld scanner, and then the tabletop scanner. The use of different dental materials significantly affected the accuracy of digital impressions. Conclusion: This study highlights the accuracy and trueness of digital impressions using various dental materials and scanners. The findings suggest that the operator's experience and scanner type impact digital impression accuracy. These insights have implications for clinical practice, indicating the need for further studies to confirm these results and explore other influencing factors in dental digital impressions. Keywords: CAD/CAM, In Vitro, Intraoral Scanning , Precision, Trueness

Purpose: The purpose of the study was to investigate the accuracy of complete-arch intraoral scans for all-on-4 implant treatment under simulated intraoral variables. Materials and methods: A maxillary model designed to receive 4 implants in the regions of first molars and canines was used. Intraoral digital scans were completed in a simulation device by simulating two2 different clinical conditions: normal intraoral variables (NIV) and limited intraoral variables (LIV). Digital scans were obtained using five 5 different IOSs: Trios 3 (TRI), Primescan (PR), iTero 2 (ITE), Medit i500 (MDT), and Aadva IOS 100P (AAD). Ten scans of each IOS were made and exported as STL files. Assessment of precision and trueness was conducted with Geomagic 3D analysis software. Each STL file was individually aligned with the reference scan and 3D differences were calculated using the root mean square (RMS) value. Data was statistically analyzed using 2-way ANOVA and Tukey HSD tests (α=.05). Results: Regarding trueness, 2-way ANOVA and Tukey comparison tests revealed significant differences between different IOSs and intraoral variables. The AAD under LIV presented significantly higher RMS than TRI, PR, ITE, and MDT (p<.001). Regarding precision, the lowest mean RMS was obtained in the IOS group of PR under NIV. AAD presented significantly higher mean RMS in the groups of both NIV and LIV (p<.001). Limited intraoral variables significantly increased the RMS values for all IOSs tested (TRI, PR, ITE, MDT, and AAD). Clinical Significance: Accuracy of complete arch all-on-4 implant scans were affected by different IOSs and intraoral variables. Simulating intraoral variables while testing IOSs might help to better validate their clinical use. Keywords: All-on-4 implant treatment, Intraoral scanner, intraoral variables., Precision, Scanning accuracy, Trueness

Aim: This study investigated the accuracy of intraoral scanner (IOS) based on different image acquisition technologies in the field of presurgical-orthopedictreatment (PSOT) in neonates with cleft. Methods: Dental cast models of clinical situations representing unilateral cleft-lip-palate(UCLP), bilateral cleft-lippalate( BCLP) and cleft-palate(CP) with reference PEEK-scanbodies (Cares RC Mono-Scankörper, Straumann, Switzerland) were scanned utilizing four IOS systems: CareStream-CS3600®(CS), Medit-i500®(MD), Cerec-Omnicam®(SO), 3Shape-Trios-3®(TS). One calibrated operator made 5 scans from each model using each IOS (N=60). Reference digital impressions were obtained by an industrialgrade laboratory scanner (Sirona inEos-X5) and superimposed using best fit algorithm. The divergence measure was extracted and the scanners were compared in view of their accuracy using generalized least squares statistical models that account for variance heterogeneity. Additionally, comparative 3D analysis of scans was performed using the reverse engineering software (Geomagic-ControlX) in order to measure the discrepancy between intraoral scans and the reference scan in different anatomic regions of interest: alveolar-crest(AC), cleft(CL), palate(PL), vestibulum(VS), premaxilla(PM). Results: The four IOS showed relevant and significant differences in estimated trueness (P<0.001) and precision (P=0.009). Among all anatomical models and analysed area of interest TS had the best accuracy (trueness: -1.57μm; precision: 9.41μm), followed by MD (trueness: - 20.63μm; precision: 29.18μm), CS (trueness: -40.43μm; precision: 16.52μm) and SO (trueness: 81.27μm; precision: 40.32μm). Conclusions: Impression of the maxilla in cleft lip and palate patients is challenging for the operator. Relevant and significant differences in trueness and precision were found between the four IOS. TS showed the best accuracy and was least influenced IOS under different anatomical situations. Keywords: Accuracy, Cleft Lip and Palate, Digital Dentistry, Digital Impression, Feeding Plate, Intraoral Scanners, Presurgical orthopedic treatment, Prosthodontics

Aim: To compare the effect of the shape of the healing abutment, concave or straight, on the dimensions of the soft tissue after healing. Materials and methods: Patients needing implant therapy in the posterior area were treated with a 1-stage surgery protocol; concave (CONC) or straight (STR) healing abutments were randomly assigned after implant installation. Before surgery, a CBCT and an intra-oral scan were obtained (IOS#0); IOS#1 was taken after soft tissue healing. The CBCT, IOSs and STL of the abutments were merged; this allowed measuring the gained/lost gingival height (ΔH), the gingival width (GWAbut) and the emergence angles (ANG) of each group. Results: Twenty-seven implants (Ø 4.2 mm, SEVEN (MIS)) with 14 CONC and 13 STR healing abutments were available for analysis. ΔH of both groups did not differ statistically. The marginal gingiva of CONC either stayed within the abutment concavity (CONCin) or reached its straight portion beyond the concavity (CONCup). When GWAbut and ANG were measured without considering this feature, the differences between STR and CONC were not statistically significant. In contrast, once this feature was considered, the difference between the groups became statistically significant. For GWAbut, results were CONCup>STR>CONCin; for ANG it was STR≈CONCup>CONCin. Conclusion: Abutment shape did not affect the gingival height. Thickness of the gingiva at the concave abutment depended upon the position of the marginal gingiva, within or beyond the concavity. This exploratory pilot study might suggest that concave abutment height should be carefully chosen to ensure that the marginal gingiva reaches the level beyond the concavity. Keywords: CBCT, concave abutment, digital workflow, emergence angle, intra-oral scan, straight abutment, thickness of gingiva

Aim: This study aimed to evaluate OccluSense's reliability against conventional articulating films in assessing static occlusion. The study also targets to identify possible limitations and influencing factors when using this device to asses static occlusion. Materials and methods: This experimental research utilized twenty epoxy resin typodont models representing various occlusal discrepancies. They were mounted in a CP Artex articulator, and static occlusion was assessed in maximum intercuspal position using shimstock foil as a gold standard. The digitally generated occlusograms by OccluSense were compared with conventional occlusal indicators, including 40 μm articulating paper (AP) and 12μm articulating foil (AF). Intrarater Reliability was assessed using Cohen's kappa coefficient (κ). Result: AP and AF showed high reliability, with κ values of 0.94 and 0.93 respectively, indicating almost perfect agreement with the gold standard. In contrast, OccluSense demonstrated an overall reliability of κ = 0.22, signifying fair agreement. Notably, significant discrepancies in κ values were observed among different malocclusions, with deep bite exhibiting the lowest reliability at κ = 0.02, representing poor agreement (P<0.05). Conclusion: OccluSense is less reliable compared to traditional methods, such as articulating paper, for assessing static occlusion. Its limitations are particularly evident in patients with deep bite, making it unsuitable as a standalone tool at the present time. Keywords: Articulating paper, Dental occlusion, Digital occlusogram, OccluSense, shimstock foil

Aim: Fixed retention is the method of choice for permanent stabilization of the treatment outcome. In recent years, CAD/CAM techniques have been developed to produce retainers with high precision and tension-free fit. The aim of this retrospective study was to evaluate the suitability of a semi-industrial retainer manufacturing process (office-based construction, external laboratory manufacturing) in terms of positioning accuracy and post-treatment changes. Materials and methods: The accuracy of 41 retainers that were digitally designed and produced from a titanium plate by water jet cutting was analyzed. The patient received the retainer through fixation with dental flosses, without using a transfer tray. We compared the position in the mouth after insertion with the virtual setup using 3D software for superimposition. Intraoral scans of 25 CAD/CAM retainers and 25 0.0175" hand-bent retainers were evaluated after one year of usage. We measured the width between the canines, the angle between the lateral incisors, and the angle of contact between the canines and the lateral incisors. Results: The largest and significant positioning deviations occurred in the vertical position, whereas positional changes in the horizontal and sagittal were small. The CAD/CAM retainers and the hand-bent retainers showed similar and minimal post-treatment alterations, which were not statistically significant. Conclusion: Semi-industrial CAD/CAM titanium retainers offer good positioning accuracy in the mandible even without a transfer tray. Increased deviations between planned and actual position only occur in the vertical plane. In addition, these retainers offer good retention properties with minimal posttreatment changes, making them suitable for permanent retention. Keywords: Computer-aided design/computer-aided manufacturing retainer, fixed retention, long-term retention, multistranded retainer, orthodontic retainer, positioning accuracy, posttreatment changes, three-dimensional

Objective: The purpose of this study was to assess the accuracy of full coverage crowns produced by two manufacturing methods: additive 3D printing and subtractive milling utilizing three different predefined cement spaces. Materials and Methods: Six groups were allocated based on the manufacturing method and the predefined cement space: printed wax with a 20 µm space (PW1); printed wax with a 50 µm space (PW2); printed wax with a 100 µm space (PW3); milled wax with a 20 µm cement space (MW1); milled wax with a 50 µm cement space (MW2); milled wax with a 100 µm cement space (MW3); milled zirconia coping with a 20 µm cement space (MZ1); milled zirconia coping with a 50 µm cement space (MZ2); milled zirconia with a 100 µm cement space (MZ3). All fabricated specimens were scanned using an Identica Blue 3D scanner and saved as standard tessellation language (STL) files. A triple scan method was performed using 3-matic software to assess accuracy. The discrepancy values were recorded in micrometers, and the analysis was conducted using one-way ANOVA. Results: The wax printing method, with a cement gap design of 100 μm, demonstrated a significant improvement in the accuracy compared to the other methods (P<.01). In contrast, the zirconia milling method exhibited significantly lower accuracy relative to the other techniques (P<0.01). Moreover, different cement spaces resulted in various accuracy levels but the only statistically significant difference was observed for the 100 µm cement space in the printed wax group. Conclusion: The additive 3D printing method exhibited greater accuracy than the subtractive milling approach. Furthermore, altering the cement gap was found to impact the accuracy of both techniques, albeit without statistical significance. Clinical Significance: The accuracy of each CAM technique was investigated in this study, highlighting the promising accuracy of 3D-printed patterns for the lost-wax technique over direct crown milling. However, all methods produced reliable and accurate crown restorations. Keywords: CAD-CAM, 3D-printing, accuracy, additive manufacturing, CNC milling, zirconia

Aim: To report on a novel digital superimposition workflow that enables measuring the supra-crestal peri-implant soft tissue dimensions all along implant treatment and afterwards. Materials and Methods: A preoperative CBCT and intra-oral scans (IOS) are successively taken before surgery, at the end of the healing period, at prosthesis delivery, and over time; they are digitally superposed on a dedicated software. Then, the stereolithography files (STL) of the healing abutment, of the prosthetic abutment and the crown are successively merged into the superposition set of IOSs. Result: The workflow protocol of merging successively the STL of each item into the superposition set of IOSs enables capturing the dimensions of the height and width of the supra-crestal soft tissues, at every level of the healing abutment, the prosthetic abutment and the crown. In addition, it allows measuring the vertical distance that the crown exerts pressure on the gingiva and the thickness of the papillae at every level of the abutment. Conclusion: This novel digital superimposition workflow provides a straightforward method of measuring the vertical and horizontal dimensions of the supra-crestal peri-implant soft tissues, including the papillae, at each stage of the implant treatment process. It allows investigating a certain number of soft tissue variables that were previously inaccessible to clinical research. It should help enhancing our comprehension of the peri-implant soft tissue dynamics. Keywords: CBCT, clinical research, digital merging, gingival height, gingival width, intra-oral scan, papilla, peri-implant soft tissues

Purpose: Is to investigate how integrating intraoral scanners in routine oral diagnosis affects patient-clinician communication, patient perceptions and preferences, offering valuable insights into the patient experience and utility of intraoral scanners in clinical practice. Materials and Methods: A restorative dentistry specialist conducted intraoral examination on 300 patients, initially using conventional techniques and X-rays, followed by a 3D scanner (ITero®element, Align Technologies, San Jose, California, USA). The patient's existing oral issues and treatment plan were initially expressed verbally, and then repeated using a 3D scan. Subsequently, the patients were requested to respond to an 11-question survey, aimed at assessing both modes of examination and communication. Statistical analysis using SPSS v.22 software included employing the Wilcoxon test to compare the patients’ experiences on the same topic before and after the examination with the intraoral scanners, considering significance at p<0.05. Results: Majority (38%) of participants aged 25-35. Gender split was 52% female, 48% male. Patients statistically found it more comprehensible to visualize existing oral issues through 3D scans than through verbal explanation (p=0.000). Also, patients understood oral hygiene recommendations better when explained via 3D scanning by dentists (p=,000). The vast majority of the participants (94%) indicated that being examined with an intraoral scanner motivated them for treatment, while 6% remained undecided. A hundred percent of the participants stated that 3D scanners should be included in the routine oral examination. Conclusion: Intraoral 3D scans enhance patient understanding and communication during oral examination and participants show high preference. However, more research needed to replace conventional diagnostic methods. Keywords: 3D imaging, digital imaging, intraoral scanners, oral diagnosis, oral examination

Objective: To investigate the application of dynamic navigation guidance technology in different implantation scenarios, and to provide a scientific basis for the innovation and advancement of implantation techniques. Methods: Fifteen cases of patients with malocclusions admitted between January 2021 and February 2023 were selected as the study subjects. All patients underwent dynamic navigation-guided oral implantation interventions. CBCT scans were taken after implantation surgery to record deviations of implantation points, including implantation point deviation, endpoint deviation, and angle deviation. Results: Dynamic navigation guidance effectively improves the reliability and stability of implantation in oral implant patients. CBCT effectively evaluated the state of the patient's periodontal implant, analyzed the state of the patient's lesion area, and improved the quality of implant intervention through CBCT guidance. The implantation point deviation was (0.407±0.193) mm, the endpoint deviation was (0.492±0.201) mm, and the implant angle deviation was (2.162±0.283)°. There was no significant difference in implantation point deviation in the anterior and posterior parts of the upper and lower jaws after intervention (P>0.05). However, there were significant differences in endpoint deviation and implant angle deviation among the anterior and posterior parts of the upper and lower jaws (P<0.05). Conclusion: Dynamic navigation guidance effectively improves the reliability and stability of implantation in oral implant patients. However, there is relatively greater endpoint deviation and implant angle deviation in the posterior part of the upper jaw. Keywords: deviation, Dynamic navigation guidance, oral implantation, Oral Implantation, Stomatology

Aim: The current study aimed to compare the responses and satisfaction reported by users with varying levels of experience when using different types of computer-aided design (CAD) software programs to design crowns. Materials and methods: A questionnaire was used to evaluate user responses to five domains (software visibility, 3Dscanned data preparation, crown design and adjustment, finish line registration, and overall experience) of various CAD software programs. The study included 50 undergraduate dental students (inexperienced group) and 50 dentists or dental technicians from two hospitals (experienced group). The participants used four different CAD software programs (Meshmixer, Exocad, BlueSkyPlan, and Dentbird) to design crowns and recorded the features using the questionnaire. Statistical analyses included one-way and two-way analysis of variance (ANOVA) tests to compare scores and verify the interaction between user response and experience. Result: User evaluation scores in the domains of software visibility and 3D-scanned data preparation varied between software programs (P < 0.001), with Exocad being favored by the experienced group. When evaluating crown design and finish line registration, Dentbird and Exocad scored significantly higher than the other software in both groups as they offered automation of the process using deep learning (P < 0.001). Two-way ANOVA showed that prior experience of using CAD significantly affected the users’ responses to all queries (P < 0.001). Conclusion: User response and satisfaction varied with the type of CAD software used to design dental prostheses, with prior experience of using CAD playing a significant role. Automation of design functions can enhance user satisfaction with the software. Keywords: CAD, deep learning, experience, prosthesis, satisfaction

Aim: Condylar hyperplasia (CH) is a progressive and deforming disease that modifies anatomy of the temporomandibular joint (TMJ) structures. This study aims to correlate the metabolic bone activity of the condyle measured by SPECT with the volumetry anatomic information from the condyle, fossa and joint space provided by CT images, in patients with CH in active and inactive forms. Materials and methods: A cross-sectional comparative study was performed with a set of 116 images from healthy and diagnosed CH patients to compare volumetric measures of the TMJ. Images were acquired through a bone tissue mask using a three-dimensional DICOM reconstruction for SPECT/CT and CBCT images and the Threshold option for segmentation with standardized values for each tissue on the HU scale. Results: there are differences (p<0.01), with greater condylar volume on the affected side in patients with active CH compared to passive CH. The volume of the glenoid cavity shows no differences in either form of CH (p>0.05), however, there were differences for the volume of the joint space on the affected right side of hemimandibular elongation (HE) in the active form. The volume of the mandibular condyle on the affected side in CH cases were larger in HE cases in active and inactive form (p<0.01) compared to healthy patients. Similar results were presented for the glenoid cavity and joint space. Conclusions: Volumetric anatomical evaluation of TMJ structures, as well as information on condylar metabolic activity, can be obtained from SPECT/CT. The study shows a greater condylar volume on the affected side of the CH compared to the contralateral side, but there are more significant differences in the active than in the inactive form. Keywords: CBCT, Condylar hyperplasia, Condylar volume, SPECT/CT, Temporomandibular Joint, tomographic segmentation

Aim: The aim of this scoping review was to identify the scientific evidence related to the utilization of Optical See- Through Head-Mounted Display (OST-HMD) in dentistry, and to determine future research needs. Methods: The research question was formulated using the "Population" (P), "Concept" (Cpt), and "Context" (Cxt) framework for scoping reviews. Existing literature was designated as P, OST-HMD as Cpt, and Dentistry as Cxt. An electronic search was conducted in PubMed, Embase, Web of Science, and CENTRAL. Two authors independently screened titles and abstracts and performed the full-text analysis. Results: The search identified 286 titles after removing duplicates. Nine studies, involving 138 participants and 1760 performed tests were included in this scoping review. Seven of the articles were preclinical studies, one was a survey, and one was a clinical trial. The included manuscripts covered various dental fields: three studies in orthodontics, two in oral surgery, two in conservative dentistry, one in general dentistry, and the remaining one in prosthodontics. Five articles focused on educational purposes. Two brands of OST-HMD were used: in eight studies HoloLens Microsoft was used, while Google Glass was utilized in one article. Conclusions: The overall number of included studies was low; therefore, the available data from this review cannot yet support an evidence-based recommendation for the clinical use of OST-HMDs. However, the existing preclinical data indicate a significant capacity for clinical and educational implementation. Further adoption of these devices will facilitate more reliable and objective quality and performance assessments, as well as more direct comparisons with conventional workflows. More clinical studies must be conducted to substantiate the potential benefits and reliability for patients and clinicians. Keywords: augmented reality, dental education, digital dentistry, mixed reality, scoping review, virtual reality

Aim: Malocclusion has emerged as a burgeoning global public health concern. Individuals with an anterior crossbite face an elevated risk of exhibiting characteristics such as a concave facial profile, negative overjet, and poor masticatory efficiency. In response to this issue, we proposed a convolutional neural network (CNN)-based model designed for the automated detection and classification of intraoral images and videos. Materials and Methods: A total of 1865 intraoral images were included in this study, 1493 (80%) of which were allocated for training and 372 (20%) for testing the CNN. Additionally, we tested the models on 10 videos, spanning a cumulative duration of 124 seconds. To assess the performance of our predictions, metrics including accuracy, sensitivity, specificity, precision, F1-score, area under the precision-recall (AUPR) curve, and area under the receiver operating characteristic (ROC) curve (AUC) were employed. Results: The trained model exhibited commendable classification performance, achieving an accuracy of 0.965 and an AUC of 0.986. Moreover, it demonstrated superior specificity (0.992 vs. 0.978 and 0.956, P < 0.05) in comparison to assessments by two orthodontists. Conversely, the CNN model displayed diminished sensitivity (0.89 vs. 0.96 and 0.92, P < 0.05) relative to the orthodontists. Notably, the CNN model accomplished a perfect classification rate, successfully identifying 100% of the videos in the test set. Conclusion: The deep learning (DL) model exhibited remarkable classification accuracy in identifying anterior crossbite through both intraoral images and videos. This proficiency holds the potential to expedite the detection of severe malocclusions, facilitating timely classification for appropriate treatment and, consequently, mitigating the risk of complications. Keywords: computer aided diagnosis, convolutional neural networks, deep learning, image detection, malocclusion, oral diagnosis

Aim: The purpose of this study is to develop software at a low cost that enables the detection of tooth colors by capturing photographs using various devices, and to compare its effectiveness with existing expensive methods. Material and Methods: A total of 60 anterior central incisor teeth from 30 individuals were included in the study. The CIELAB values (L,a,b) of each tooth were measured using a spectrophotometer, which is considered the gold standard. Subsequently, photographs of the teeth were taken using four different smartphones (iPhone- Xiaomi) and one digital camera (Canon). These images were then subjected to image processing techniques and compared with measurements obtained through computer-based analysis in order to assess the correlation. Data with three or more groups, the Kruskal-Wallis H test was utilized, and multiple comparisons were conducted using the Dunn test. A significance level of p<0.05 was considered. Results: Upon examining the results of multiple comparisons, a statistically significant difference was observed (p<0.001) between the DeltaE values obtained from the camera of the iPhone and those obtained from the Canon DSLR and Xiaomi cameras. The iPhone cameras yielded result values ranging from 2.68 to 2.90 for DeltaE. Conclusions: It is reported that color determination methods based on image processing of photographs taken with iPhone mobile phones could potentially gain an advantageous position in routine clinical practice, as compared to spectrophotometry. Keywords: Color Detecting, Image Processing, Shade Matching, Smartphones, Spectrophotometer

Aim: The aim of this study was to evaluate the physical-mechanical behavior of the occlusal veneers when subjected to thermomechanical cycling. Materials and Methods: Sixty specimens were divided into 04 groups (n=15 per group), according with the different restorative materials and thicknesses: material – lithium dissilicate LD (IPS e.max CAD, Ivoclar Vivadent) and nano- ceramic-resins NCR (ESPE Lava Ultimate, 3M); thickness - 0.6 and 1.2mm. The occlusal veneers were bonded over human flattened fresh extracted molars with dual-polymerizing luting agent (Variolink N, Ivoclar Vivadent and RelyX Ultimate 3M) using the respective adhesive system following the selective-etch technique (self-etch in dentin and total etch in enamel). The resin cement was light cured for 40 seconds each face, using a LED light cure equipment (BlueStar II, Microdont, 1100 mW/cm2). The response variables consisted of veneer survival rates (crack formation, catastrophic cracks and debonding) when subjected to thermal cycling from 5° to 55° C and simultaneous mechanical cycling performed at load intensities of 100, 200, 300, 400 and 450N for 20,000 cycles each. Result: Data were submitted to the Kruskall Wallis test and Pairwise Comparison, adopting a significance level of 5%. NCRs presented a lower incidence of failures (p<0.05) when compared to LD. According to thickness factor, 1.2mm thick occlusal veneers withstand higher cycling loads. Conclusion: NCR occlusal veneers with 1.2mm thickness presented superior physical-mechanical behavior than lithium disilicate and 0.6mm restorations. Keywords: CAD/CAM, Ceramics, Digital Dentistry, Minimally Invasive Dentistry, Occlusal veneers, Resin Composite

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 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

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 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