The impact of digitization and conventional techniques on the fit of fixed partial dentures FPDs: systematic review and Meta-analysis.

PURPOSE OF THE STUDY: The goal behind this study is to answer the question "In tooth-supported fixed partial dentures (FPDs), does the digital impression techniques compared to fabrications using conventional impression methods improve the marginal and internal fit? BACKGROUND: The incorporation of digital technology in the fabrication of fixed partial dentures (FPDs) has accelerated over the past decade. This study is directed at evaluating the marginal and internal fit of FPDs manufactured using digital approaches compared to conventional techniques. The need for updated data has encouraged this review. MATERIALS AND METHODS: An electronic search was conducted in PubMed, Scopus, Web of Science, and the Grey Database to identify relevant studies. The Modified Methodological Index for Non-Randomized Studies (MINORS) was used to assess the risk of bias in in vitro experiments. The key results of this meta-analysis were the standard mean differences (SMDs) and 95% confidence intervals (CI) of each main variance, marginal fit, and internal fit between the digital and conventional techniques. Additional analyses were performed to assess the significance of three subgroup parameters: method of digitalization, cement spacer thickness, and span length, and their influence on the fit of the FPDs. RESULTS: Based on predefined criteria, of the seven articles included in this systematic review, only five were selected for the quantitative data analysis. The marginal fit results were (P = 0.06; SMD: -1.88; 95% CI: - 3.88, 0.11) (P > 0.05) and the internal fit results were (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.10) (P < 0.05). Regarding the subgroup analyses, the method of digitalization subgroup results were (P = 0.35; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.80; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively. The span length results were (P = 0.10; SMD: -1.89; 95% CI: - 3.89, 0.11) for marginal fit and (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.11) for internal fit. The cement spacer thickness (P = 0.01; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.04; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively. CONCLUSION: Tooth-retained fixed partial dentures FPDs produced by digital scanning and computer-aided design/computer-aided manufacturing (CAD/CAM) systems can significantly enhance the internal fit compared with those manufactured by traditional methods. Intraoral scanners can replace conventional impressions for the fabrication of FPDs because they minimize the operating time and reduce patient pain. Further clinical studies are required to obtain more conclusive results. SYSTEMATIC REVIEW REGISTRATION: This systematic review and meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42021261397.

An in vivo study to assess and compare the angular, linear, and depth deviation as well as the difference in bone density of implants placed using computer-aided design/computer-aided manufacturing fabricated three-dimensional guides versus the implants placed using bone pen kit in maxillary and mandibular ridges.

Aim: The aim is to assess and compare angular, linear, and depth deviation and difference in bone density of dental implants placed using computer aided design/computer aided manufacturing (CAD/CAM) fabricated surgical guides versus implants placed using Bone Pen Kit. Till now, no original research exists in the search engines such as Pubmed, Google Scholar, Science Direct, and Research Gate on this kit. Settings and Design: In vivo- Randomised control trial. Materials and Methods: Twenty clinical cases were selected and split into two distinct groups. Group 1 involved the placement of 10 implants using CAD/CAM fabricated three dimensional guides and Group 2 involved the placement of 10 implants using Bone Pen Kit. Four deviation parameters were evaluated, which included: (a) Angular deviation, (b) Linear deviation at implant platform, (c) Linear deviation at implant apex, and (d) Depth deviation and difference in bone density before and after implant placement was also evaluated. Statistical Analysis Used: SPSS software version 23 was utilized for the analysis of the data. The comparison was made using the Whitney test, and Wilcoxon signed rank test. Results: When comparing angular deviation, the results indicated a statistically significant difference with a P < 0.05. The values observed for angular and linear deviation in Group 2 were significantly greater than those in Group 1. No statistically significant difference in depth and linear deviation was found at the implant platform among the two groups. Bone density before and after implant placement was significantly higher in Group 1. Conclusions: (1) Angular and linear deviation at the apex in Group 2 exhibited higher values in comparison to Group 1, (2) No difference in depth and linear deviation at the implant platform was found among the two groups, and (3) There was no difference in change in bone density among two groups.

Comparative analysis on efficiency and accuracy of parallel confocal microscopy and three-dimensional in motion video with triangulation technology-based intraoral scanner under influence of moisture and mouth opening - A crossover clinical trial.

Aim: The intraoral scanners are digital devices used to digitise the oral tissues. The accuracy of the intraoral scanners has been studied under different environmental conditions, but there might be differences that occur in the actual oral environment, which is still in question. The aim of the study was to evaluate the accuracy and efficiency of Parallel Confocal Microscopy and 3D in motion video with triangulation technology-based intraoral scanners under the influence of moisture and mouth opening. Settings and Design: This was an Cross over clinical controlled study. Materials and Methods: The controlled in vivo study included healthy subjects who were in need of CBCT for the purpose of locating the position of unerupted third molars before going abroad for a job. The subjects were exposed to scans in the upper and lower jaws with two intraoral scanners based on 3D motion video technology with triangulation (Medit) and parallel confocal microscopy (Trios) under the influence of two oral conditions, which were moisture (presence and absence of moisture) and mouth opening (30 mm and 50 mm, respectively). A total of 96 scans were obtained and superimposed individually over the reference CBCT scans to find the deviations in the Geomagic Rapidform (version 2020, USA) software. The efficiency of the scanners was calculated by recording the time taken and the number of images obtained after each scan. Statistical Analysis Used: The significance was calculated by using the independent and paired sample t test in SPSS software (IBM, version 23). Results: Based on the surface analysis, the trueness of the intra-oral scanners had statistically significant differences when compared between 3D in motion video technology with Triangulation and Parallel Confocal Microscopy (P < 0.05) whereas no statistical significance was observed in precision. There was a significant difference observed in the efficiency of the intra-oral scanners (P < 0.05). Conclusion: There is a significant difference in the accuracy and efficiency of the intraoral scanners under the influence of oral conditions, such as different moisture levels and mouth opening conditions. 3D in motion video technology with Triangulation showed better results with the least deviation than Parallel Confocal Microscopy.

Computer-aided design software-enabled preclinical prosthodontic training: A digital education technique.

The prosthodontics preclinical training modules involve textbook-based two-dimensional (2D) ideal images and practicing on manikin models to emulate ideal tooth preparations and teeth arrangements. Relying solely on 2D images as objectives for preclinical exercises limits the trainee's creative skills to instructions of textbooks and clinical instructions received. With advancements in digital dentistry, dental trainees should have early exposure to the three-dimensional (3D) rendering of ideal preclinical objectives. A dental education technique using computer-aided design software and smartphones is described that will allow 3D rendering of ideal prosthodontic training assignments allowing early exposure to digital dentistry for dental training students.

Effect of simulated gastric acid on aesthetical restorative CAD-CAM materials' microhardness and flexural strength.

Background: Gastric acid, which is among erosive substances, gradually rises to the mouth in individuals with reflux and bulimia nervosa disorders, and this causes various effects on dental restorations. Aim: The objective of this study is in vitro investigation of gastric acid's effect on flexural strength and hardness on aesthetic restorative computer-aided design and computer-aided manufacturing (CAD-CAM) materials. Materials and Methods: For this study, four materials have been used, namely Enamic (Vita), Superfect Zir (Aidite) Zirconia, IPS e.max CAD (Ivoclar Vivadent), and Mark II (Vita). From these four different materials, 24 samples with 14 × 4 × 1 dimensions in rectangular prism form are used, which makes a total of 96 samples. One group was separated as the control group, while the rest was allowed to wait at 37°C, 5 ml gastric acid for 96 hours. Hardness value and flexural strengths were measured as pre-exposure and post-exposure to gastric acid. Results: There is a statistically significant difference between the groups in terms of the amount of decrease in the mean hardness after exposure to gastric acid compared to pre-exposure values (p: 0,000; P < 0,05). There was no statistically significant difference between the groups in terms of the amount of decrease in the post-exposure average flexural strength compared to the pre-exposure value (p: 0.063; P > 0.05). There is a statistically significant difference between the groups in terms of the average flexural strength after exposure to the acid. Conclusions: According to the data obtained, it was concluded that exposure to gastric acid affects the hardness and flexural strength properties of dental restorative ceramic materials.

Novel CAD-CAM fabrication of a custom-made ball attachment retentive housing: an in-vitro study.

PURPOSE: This study aims to evaluate the digitally designed ball attachment housing in its initial retentive force and after 2 years of simulated clinical use and to compare it with the regular nylon ball attachment housing. MATERIALS AND METHODS: Twenty implants with their corresponding ball abutments (diameter 4.5 × 4.0 mm) were inserted in resin blocks. They were divided into two groups. In Group I, ten ball abutments each received their corresponding conventional attachment with nylon rings. In Group II, ten ball abutments received the novel CAD-CAM polyetheretherketone ball attachment housing. A universal testing machine was used to measure the retention force. The achieved maximum values of retention force were recorded at the beginning of the study (initial retention) and after 2 years of artificial ageing (2000 cycles of insertion and removal). Results were statistically analyzed using an independent sample T test. RESULTS: The PEEK attachment housing showed high retention forces (25.12 ± 0.99 N) compared to the conventional attachment with a nylon ring (15.76 ± 0.93 N) in the initial dislodgement test. There was a statistically significant difference in mean retention at the initial retention test and after 2 years of stimulated usage between the two studied groups, p = 0.000. CONCLUSIONS: Within the limitations of this study, the novel CAD-CAM-PEEK attachment showed high retention characteristics compared to the conventional attachment with nylon rings, initially and after simulated long-term use.

Digital measurement method for comparing the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using conventional and digital technologies.

BACKGROUND: In clinical practice, control of the marginal fit of fixed dental prostheses is hindered by evaluation method, which needs to be further improved to increase its clinical applicability. This study aimed to quantitatively analyze the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated by conventional and digital technologies using a digital measurement method based on the digital impression technology and open source software. METHODS: A digital workflow and the conventional impression combined with the lost-wax heat-pressed technique were adopted to separately fabricate 10 glass ceramic fixed dental prostheses. Three-dimensional data for the abutments, fixed dental prostheses, and fixed dental prostheses seated on the abutments, were obtained using a dental scanner. The two datasets were aligned using registration technology, specifically "multi-points registration" and "best fit alignment," by reverse engineering software. Subsequently, the three-dimensional seated fit between the fixed dental prostheses and abutments were reconstructed. The margin of the abutment and crown was extracted using edge-sharpening and other functional modules, and the absolute marginal discrepancy was measured by the distance between the margin of the abutment and crown. One-way analysis of variance was used to statistically analyze the measurement results. RESULTS: Using the digital measurement method, the mean value of absolute marginal discrepancy for fixed dental prostheses fabricated by the conventional method was 106.69 ± 6.46 µm, and that fabricated by the digital workflow was 102.55 ± 6.96 µm. The difference in the absolute marginal discrepancy of three-unit all-ceramic fixed dental prostheses fabricated using the two methods was not statistically significant (p > 0.05). CONCLUSIONS: The digital measurement method for absolute marginal discrepancy was preliminarily established based on open source software and applied in three-unit ceramic fixed dental prostheses. The absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using digital technology was comparable to that of conventional technique.

Influence of an internal firing of feldspathic porcelain before or after sintering on adaptation of high-translucent zirconia laminate veneers.

The aim of the present study was to evaluate the influence of two different internal surface treatments, namely, the firing of feldspathic porcelain before or after zirconia sintering, on the marginal and internal adaptation of laminate veneers (LVs) made of high-translucent zirconia. A total of 33 zirconia LVs were fabricated using a CAD/CAM system and divided into three groups based on the internal surface treatment method: the pre-firing (PRE) group involved firing feldspathic porcelain before zirconia sintering, the post-firing (POS) group involved firing feldspathic porcelain after zirconia sintering, and the no treatment (NT) group involved no application of feldspathic porcelain. The adaptation of the LVs was measured using a silicone replica technique. Data were analyzed using the Kruskal-Wallis and Steel-Dwass tests (α = .05). The POS group showed significantly higher marginal discrepancy values than the PRE group across all sites. The internal space values of the PRE groups were significantly lower than those of the NT group at all sites. The internal firing of feldspathic porcelain before zirconia sintering resulted in better marginal adaptation of the high-translucent zirconia LVs than the internal firing of feldspathic porcelain after zirconia sintering. The internal firing of feldspathic porcelain before zirconia sintering can achieve uniform internal adaptation of high-translucent zirconia LVs.

Evaluation of the Effects of Digital Manufacturing, Preparation Taper, Cement Type, and Aging on the Color Stability of Anterior Provisional Crowns Using Colorimetry.

BACKGROUND Replicating the 3-dimensional (3D) color of natural teeth in artificial substitutes is challenging. Fixed dental prosthodontics require aesthetic, color-stable provisional restorations. Recent milling and 3D printing digital manufacturing techniques offer improved outcomes. This study assesses color stability in various digital manufacturing methods, tapers, and aging effects on anterior provisional resin restorations. MATERIAL AND METHODS Two all-ceramic tooth preparations on typodont teeth with 10° and 20° tapers were converted into experimental dies. Forty temporary crowns were manufactured using 3D printing and computer-aided design/computer-aided manufacturing (milling). Within these 2 groups, 10 crowns were cemented using a regular and clear provisional cement. All samples were thermocycled to simulate clinical use of 6 months. Color difference formula (CIEDE2000) indicated changes between before and after cementation (ΔE00) and between after cementation and after thermocycling (ΔE00[II]). The color change was considered significant in terms of clinically perceptible (ΔE00 ≤0.62) and acceptable (ΔE00 ≤2.62) changes. One-way ANOVA (P value of less than 0.05) calculated overall differences, which were established using a Fisher post hoc test. RESULTS Crowns cemented with clear cement showed fewer color changes irrespective of the manufacturing technique or taper. Notably, only the 10° 3D-printed crown with clear cement had an imperceptible color change at the pre-/post-cementation phase. Meanwhile, the 10° and 20° milled crowns with regular cement exhibited unacceptable color changes after thermocycling. CONCLUSIONS For long­term temporization in the aesthetic zone, properly optimized 3D-printed provisional restorations cemented with clear cement had better color stability.

Three-Dimensional Scanning Accuracy of Intraoral Scanners for Dental Implant Scan Bodies-An Original Study.

Background and Objectives: With the increased trend towards digitalization in dentistry, intraoral scanning has, to a certain extent, replaced conventional impressions in particular clinical settings. Trueness and precision are essential traits for optical impressions but have so far been incompletely explored. Materials and Methods: We performed a study to evaluate the differences in the three-dimensional spatial orientations of implant analogs on a stone cast when using an intraoral scanner compared to a dental laboratory scanner. We assessed the deviation of the intraoral scans compared to the laboratory scan for three standardized implant measurement plans and compared these results with control scans of the neighboring natural teeth. Results: We found no statistically significant correlation between the measurements at the scan body level and the landmarks chosen as controls on the neighboring natural teeth (p = 0.198). The values for the implant scans presented wider variation compared to the control scans. The difference between the implant and the control planes ranged from -0.018 mm to +0.267 mm, with a median of -0.011 mm (IQR: -0.001-0.031 mm). While most values fell within a clinically acceptable margin of error of 0.05 mm, 12.5% of the measurements fell outside of this acceptable range and could potentially affect the quality of the resulting prosthetic work. Conclusions: For single-unit implant-supported restorations, intraoral scanning might have enough accuracy. However, the differences that result when scanning with an intraoral scanner may affect the quality of prosthetic work on multiple implants, especially if they are screw-retained. Based on our results, we propose different adaptations of the prosthetic protocol to minimize the potential effect of errors that may occur during the digital workflow.

THE MARGINAL ACCURACY OF LITHIUM DISILICATE SINGLE CROWNS IS COMPAREABLE WHEN MADE FROM CONVENTIONAL OR DIGITAL (DIRECT OR INDIRECT) WORKFLOWS.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Tabesh M, Nejatidanesh F, Savabi G, Davoudi A, Savabi O. Marginal accuracy of lithium disilicate full coverage crowns made by direct and indirect digital or conventional workflows: a systematic review and meta-analysis. J Prosthodont. 2022;31(9):744-753. doi:10.1111/jopr.13515. SOURCE OF FUNDING: Dental Research Center, Isfahan University of Medical Sciences Research Grant #298095. TYPE OF STUDY/DESIGN: Systematic review with meta-analysis of data.

Effect of thickness and shade of CAD/CAM composite on the light transmission from different light-curing units.

The thickness and shade of a restoration will affect the transmission of light from the light-curing unit (LCU). This study determined the power (mW), spectral radiant power (mW/nm), and beam profile of different LCUs through various thicknesses and shades of a CAD-CAM resin composite (BRAVA Block, FGM). Five thicknesses: 0.5; 0.75; 1.0; 1.5, and 2.0 mm, in three shades: Bleach; A2 and A3.5 of a CAD-CAM resin (n = 5). Two single-peak LCUs: EL, Elipar DeepCure-S (3M Oral Care); and OP, Optilight Max (Gnatus), and one multiple-peak LCU: VL, VALO Grand (Ultradent), were used. The LCUs were positioned touching the surface of the BRAVA Block. The power and emission spectrum were measured using a fiberoptic spectrometer attached to an integrating sphere, and the beam profiles using a laser beam profiler. The effect of the material thickness on the light attenuation coefficients was determined. VL and EL delivered more homogeneous beam profiles than OP. The type of the BRAVA Block had a significant effect on the transmitted power, and wavelengths of transmitted light (p < 0.001). There was an exponential reduction in the power and emission spectrum as the thickness of the BRAVA Block increased (p < 0.001). The light transmission through the A2 shade was least affected by the thickness (p < 0.001). The attenuation coefficient was higher for the violet light and higher for A3.5 than the A2 or Bleach shades. No violet light from the VL could be detected at the bottom of 2.0 mm of the BRAVA Block.

Accuracy of fit for cobaltchromium bar over two implants fabricated with different manufacturing techniques: an in-vitro study.

OBJECTIVE: The purpose of the invitro research was to compare the fit of Cobalt Chromium customized bar fabricated with different manufacturing processes cast metal bar, milled bar and 3D printed bar using scanning electron microscope. MATERIALS AND METHODS: Clear epoxy resin molds were prepared. In each mold two parallel implants with a 14 mm distance from each other were embedded. Thirty Co-Cr custom bars were constructed and were divided equally into three groups: Group (I) (Co-Cr conv), group (II) milled bar (Co-Cr milled), and group (III) printed bar (Co-Cr print). The marginal fit at implant-abutment interface was scanned using scanning electron microscope (SEM). RESULTS: There was a significant difference between the three studied groups regarding marginal misfit the between implant and fabricated bars with p-value < 0.001. The highest value of micro-gap distance was found in Co-Cr conventional group (7.95 ± 2.21 µm) followed by Co-Cr 3D printed group (4.98 ± 1.73) and the lower value were found in Co-Cr milled (3.22 ± 0.75). CONCLUSION: The marginal fit of milled, 3D printed and conventional cast for Co-Cr alloy were within the clinically acceptable range of misfit. CAD/CAM milled Co-Cr bar revealed a superior internal fit at the implant-abutment interface. This was followed by selective laser melting (SLM) 3D printed bar and the least fit was shown for customized bar with the conventional lost wax technique.

Clinical application of a digital semi-rigid bridge space maintainer fabricated from polyetheretherketone for premature loss of primary molars.

BACKGROUND: Premature loss of primary molars can be treated with a band loop space maintainer (SM). However, fabricating a conventional band loop SM requires multiple clinical and laboratory procedures, which can potentially affect the accuracy of the SM. Moreover, the conventional SM is unable to fully restore masticatory function and maintain the vertical dimension of the edentulous space. In this current study, a fully digital workflow to fabricate a semi-rigid bridge SM made from polyetheretherketone (PEEK) has been described and evaluated for its clinical effectiveness. METHODS: A total of 15 children (eight males and seven females) between the ages of 4-8 years, who experienced the premature loss of a single primary molar, were included in this study. Digital impressions were taken using the CEREC CAD/CAM chair system and imported into CAD software to design the semi-rigid bridge SM, which was fabricated using PEEK block as the maintainer material. The digital SM was tried-in and bonded to the abutment with resin cement. The edentulous space was measured immediately after bonding (T0) and 1 month (T1), 3 months (T2), and 6 months (T3) after treatment. The periodontal condition and mobility of the SM and abutment were also examined. RESULTS: The use of digital impressions resulted in a decreased occurrence of the pharyngeal reflex. The digital semi-rigid bridge SM, fabricated with PEEK, was both convenient and aesthetically pleasing, and successfully restored the anatomy and masticatory function of the missing primary molar. None of the 15 semi-rigid bridge SMs or abutments became loose or fell off during the study, and only one child presented with gingivitis. Furthermore, the difference in the edentulous space at T0, T1, T2, and T3 was not statistically significant (all P > 0.05). CONCLUSIONS: The digital semi-rigid bridge SM fabricated with PEEK was clinically effective in maintaining the missing space and had advantages over the traditional band/crown loop SM.

CAD/CAM-assisted ablative surgery and intraoperative brachytherapy for pediatric skull-base sarcomas.

BACKGROUND: Head and neck (H&N) sarcomas in children can poise numerous challenges to the surgical oncologist and require multidisciplinary input and meticulous surgical planning. The application of computer-assisted design/computer-assisted manufacturing (CAD/CAM) has been extensively examined in H&N reconstruction in adults, but its utility in ablative oncologic surgery in children warrants further examination. We present preliminary results utilizing CAD/CAM techniques to assist in planning tumor resections and the application of intra-operative radiation in children with skull-base sarcomas. METHODS: A retrospective cohort review of all pediatric patients who presented to a tertiary care cancer center for surgical resection of a skull-base malignancy was performed between 1980 and 2021. All children under 18 years of age with diagnosis of a skull-base sarcoma as confirmed with imaging and pathology were analyzed. RESULTS: A total of 21 children were identified but only four children with skull-base sarcomas had diagnostic imaging available in whom computer-assisted volumetric analyses were generated. In these cases, CAD/CAM was used to plan surgical approaches and intraoperative radiotherapy, significantly aiding in treatment for these complicated pediatric cases. CONCLUSION: CAD/CAM planning for oncologic resection has huge potential. Here we have shown its utility in pre-operative surgical planning and for administration of intraoperative radiation therapy. Future studies are needed to examine its value in facilitating intraoperative surgical management and patient outcomes, as well as cost effectiveness.

In Vitro Affinity Maturation of Nanobodies against Mpox Virus A29 Protein Based on Computer-Aided Design.

Mpox virus (MPXV), the most pathogenic zoonotic orthopoxvirus, caused worldwide concern during the SARS-CoV-2 epidemic. Growing evidence suggests that the MPXV surface protein A29 could be a specific diagnostic marker for immunological detection. In this study, a fully synthetic phage display library was screened, revealing two nanobodies (A1 and H8) that specifically recognize A29. Subsequently, an in vitro affinity maturation strategy based on computer-aided design was proposed by building and docking the A29 and A1 three-dimensional structures. Ligand-receptor binding and molecular dynamics simulations were performed to predict binding modes and key residues. Three mutant antibodies were predicted using the platform, increasing the affinity by approximately 10-fold compared with the parental form. These results will facilitate the application of computers in antibody optimization and reduce the cost of antibody development; moreover, the predicted antibodies provide a reference for establishing an immunological response against MPXV.

Role of Computer-Aided Drug Design in Drug Development.

The introduction of computational techniques to pharmaceutical chemistry and molecular biology in the 20th century has changed the way people develop drugs [...].

3D-Printed Implant Sliding Guide: A New Dental Implant Surgical Guide.

PURPOSE: To compare the linear and angular deviations of sites prepared for implants with the proposed 3D-printed sliding guide vs a 3D-printed conventional sleeveless static guide. MATERIALS AND METHODS: This study consisted of two groups: a control group of 14 3D-printed conventional sleeveless static guides, and a test group of 37 3D-printed sliding guides. The guides were designed to drill 37 implant sites in each group. Linear and angular deviations were determined after scanning the drilled casts. Linear deviations were measured at the coronal and apical aspects of the drilled implant sites at 5-, 10-, 15-, and 20-mm distances. RESULTS: There were no significant differences between the control and study groups regarding the coronal and 5-mm apical linear deviations. The angular and 10-, 15-, and 20-mm linear deviations of the 3D-printed sliding guide were significantly smaller than the control group. CONCLUSIONS: The proposed 3D-printed sliding guide could reduce the angular deviation of drilled implant sites from the planned positions, which is reflected in reducing the linear apical deviation of prepared implant sites longer than 5 mm.

Effect of substrate adjacent to the scan region on the trueness of four intraoral scanners: An in vitro study.

OBJECTIVES: The purpose of this in vitro study was to evaluate the trueness of four commercially available intraoral scanners (IOSs) on scanning different substrates that existed in the adjacent proximal contact area. METHODS: Four IOSs (TRIOS 4, TRIOS 3, Primescan, Omnicam) were used for scanning the intact enamel surface of a molar tooth, and six restorative materials (zirconia, lithium disilicate glass-ceramic, composite resin, hybrid ceramic, feldspathic ceramic, metal) that were located at the adjacent proximal contact area of the same tooth. Reference scans were obtained using an extraoral scanner (inEos X5). A 3-dimensional analyzing software (Geomagic Control X) was used to compare the reference and tested scans. The two-way analysis of variance (ANOVA) followed by Bonferroni correction was performed for statistical analyses (α=0.05). RESULTS: TRIOS 3 and TRIOS 4 showed higher trueness than Primescan, and Primescan showed higher trueness than Omnicam (p<0.001), while there were no differences between TRIOS 3 and TRIOS 4. Metal showed significantly higher Root Mean Square values (0.273 ± 0.24 mm) than other substrates. No difference was found between the scanners' zirconia, lithium disilicate glass-ceramic, composite, and feldspathic ceramic scans (p > 0.05). For the metal, TRIOS 3 and TRIOS 4 showed higher trueness than Primescan and Omnicam, while Omnicam showed lower trueness among all scanners. For the hybrid ceramic, TRIOS 3 showed higher trueness than Omnicam (p<0.001). For the enamel, TRIOS 3 showed higher trueness than Primescan and Omnicam (p<0.001). CONCLUSIONS: The trueness of IOSs can be affected by the substrates that exist in the proximal contact area. Amongst all, the metal substrate affected most the trueness of the IOSs. CLINICAL SIGNIFICANCE: The clinician should decide on the impression system, taking into account that the IOS and the surfaces to be scanned affect the trueness of the digital data. The deviation of the digital impression would be high in the presence of a metal restoration on the adjacent proximal surface.