Transferring emergence profile and position of interim restorative implant fixture. A novel digital technique.

The present technical article describes a protocol to digitally reproduce the emergence profile of an interim implant prosthesis (IP) and to transfer its macrogeometry into the definitive restoration. The purpose of this protocol was to minimize alterations in the gingival architecture developed during the interim restorative phase of a single implant that could potentially jeopardize its esthetic outcome. The process included obtaining an intraoral scan with the interim IP in situ, a duplicate of this intraoral scan that was used to capture the exact position of the implant, and an extraoral scan of the prosthesis. These data could then be imported into IOS software to create a model where the patients' soft tissue was incorporated with precision, allowing for the fabrication of a definitive crown with an optimal soft tissue adaptation. As there are few articles in the scientific literature that have reported a consistent method to replicate the emergence profile of an interim IP, the present technical article aims to highlight the potential of utilizing the emergence profile of an interim IP created by IOS software.

Advanced digital planning approach using a 3D-printed mock-up. A case report.

OBJECTIVE: A diagnostic mock-up is a key tool that allows a preview of the outcome of an esthetic restoration. With recent developments in CAD/CAM technology, it is important to understand the pros and cons of chairside digital dentistry and the restorative materials used. The aim of the present case report is to describe in detail the use of a 3D-printed mock-up fabricated from a polymer-based material for an esthetic treatment plan within a fully digital workflow. CASE REPORT: A 45-year-old female patient presented at the clinic concerned about her esthetic appearance and the color of her anterior incisors. After a conclusive diagnosis, a restoration was planned using ceramic veneers from maxillary premolar to premolar. For a preview visualization of the outcome, an intraoral scanner was used to obtain 3D images and to allow the design of a digital smile. The template STL file was exported to a 3D printer and a 0.6-mm mock-up in A3-shade 3D resin was produced after 25 min. The mock-up was tested through a try-in and approved by the patient. As a result, the printed mock-up was considered predictable and reliable for the final restoration. CONCLUSIONS: The ease, speed, and reduced costs derived from the digital workflow, in conjunction with the accuracy of the mock-up, made the procedure highly efficient and recommendable.

A systematic review of factors impacting intraoral scanning accuracy in implant dentistry with emphasis on scan bodies.

PURPOSE: The purpose of this systematic review was to explore and identify the factors that influence the accuracy of intraoral scanning in implant dentistry, with a specific focus on scan bodies (ISBs). METHODS: Following the PRISMA 2020 guidelines, this study conducted a thorough electronic search across MedLine, PubMed, and Scopus to identify relevant studies. Articles were screened based on titles, abstracts, and full texts for relevance. The Robins I tool assessed the risk of bias in various study types. Data extraction occurred based on predetermined parameters for studying specimens and assessing outcomes. RESULTS: 16 studies met the specified criteria and were consequently included in the systematic review. Due to variations in variables and methods across the selected studies, statistical comparison of results was not feasible. Therefore, a descriptive review approach was chosen, acknowledging the substantial heterogeneity in the reviewed literature. CONCLUSIONS: The precision of virtual scan results is contingent upon diverse characteristics of ISBs and implants. These factors encompass their placement within the dental arch, structural design, shape, material composition, color, and the manufacturing system, all of which contribute to scan accuracy. Additionally, considerations such as the intraoral scanner (IOS) type, scanning technique, use of scan aids, inter-implant distance, scan span, and the number of implants warrant evaluation. In the context of capturing implant positions, intraoral scanning with ISBs demonstrates comparable accuracy to traditional impression methods, particularly in single and short-span scenarios. However, the existing data lacks sufficient information on in vivo applications to formulate clinical recommendations.

Does the choice of the measuring technique affect the comparison of fit between zirconia and cobalt-chromium prostheses?

AIMS: The objectives of the study were to compare the adaptation of presintered zirconia and cobalt- chromium prostheses using microcomputed tomography (µCT), scanning electron microscopy (SEM), and stereomicroscope (SM). MATERIALS AND METHODS: Twenty-four fixed dental prostheses (FDPs) were fabricated on metal abutments, duplicated from maxillary first premolar and first molar prepared on a typodont model. Teeth were reduced to obtain chamfer of 1.2 mm and reduction occlusaly of 2 mm occlusal. Scanning of the abutments was done with random assignment to two groups receiving the FDPs made from soft-milled Co-Cr (n = 12) and zirconia (n = 12). Marginal and internal gaps were assessed using three evaluation techniques (X-ray microcomputer tomography, SEM, and stereomicroscopy). STATISTICAL ANALYSIS USED: Comparison of the results was made using Levene and analysis of variance tests (α =0.05). RESULTS: Irrespective of the material tested, statistical differences were found between the measuring techniques (P = 0.001 overall); the obtained mean gaps were for CT scan (92.60 ± 13.31), for SEM (101.92 ± 23.03), and for SM (113.44 ± 14.68): the multiple comparisons between techniques found a significant difference between CT and SM (P < 0.001), and SEM and SM (P = 0.025). When materials were compared within each measuring technique, Co-Cr showed lower values compared to zirconia in SEM (P < 0.001) and Stereo (P = 0.049); similar results were found in CT. CONCLUSIONS: Results values differed with the chosen measuring technique. Co-Cr prostheses had a better fit than zirconia prostheses in SEM and Stereo. µCT showed comparable results to SEM, smaller than SM results.

Influence of CAD-CAM milling strategies on the outcome of indirect restorations: A scoping review.

STATEMENT OF PROBLEM: The influence of computer-aided manufacturing (CAM) parameters and settings on the outcomes of milled indirect restorations is poorly understood. PURPOSE: The purpose of this scoping review was to summarize the current CAM systems, parameters, and setting changes, and their effects on different outcomes of milled indirect restorations and aspects related to their manufacture. MATERIAL AND METHODS: The protocol of this review is available online (https://osf.io/x28ps/). Studies that used at least 2 different parameters (CAM units, number of axes, digital spacers, or protocols with different rotatory instruments, grit-sizes, milling speed, or others) for milling indirect restorations were included. A structured search up to July 2023 was performed by 2 independent reviewers for articles written in English in LILACS, MEDLINE via PubMed, EMBASE, Web of Science, and Scopus. RESULTS: Of 1546 studies identified, 22 were included in the review. Discrepancies were found between the planned and actual measured cement space, with a decreasing linear relationship impacting restoration adaptation at different points. The CEREC MC XL milling machine was the most used system in the included studies, with variations in bur types, milling modes, and number of burs uses affecting internal fit and surface trueness. The results demonstrated the better adaptation of restorations made with 5-axis over 3-axis milling machines. Lithium disilicate and zirconia were the most commonly used materials, and crowns and inlays were popular designs. Marginal and internal adaptation were the primary outcomes assessed using the various techniques. CONCLUSIONS: The study presented a comprehensive exploration of CAM systems and parameters, and their influence on indirect restorations. The planned cement space was not properly reproduced by the milling. Bur characteristics can affect restoration fit and trueness. The 5-axis units seem to result in better-adapted restorations compared with 3- and 4-axis units.

Trueness and precision of an intraoral scanner on abutments with subgingival vertical margins: An in vitro study.

OBJECTIVES: This study aimed to evaluate the accuracy of an intraoral scanner (IOS - Medit i700) on tooth abutments with vertical preparations at 2 depths below the free gingival margin, and to determine if the IOS can reproduce the area beyond the finish surface of the tested preparation geometry. METHODS: Two abutments for a maxillary first molar were designed by means of CAD software, with vertical preparations set at 1 and 2 mm below the gingiva. These abutments were subsequently printed in resin and placed on a reference model. The reference files consisted of scans made using a metrological machine on these abutments. Ten scans were made with the tested IOS on each sample, resulting in two study groups. The scans from the experimental groups were labeled "V-1″ for vertical preparation at 1 mm below the gingival margin and "V-2″ for 2 mm below. The analysis of these scans was performed using Geomagic Control X (3D SYSTEMS) to assess their trueness and precision in µm. Descriptive statistics with a 95 % confidence interval were employed, alongside independent sample tests, to ascertain any differences between the groups (α=0.05). RESULTS: Statistically significant differences were not found both for trueness (p=.104) and precision (p=.409), between the tested geometries. The mean values for trueness were V-1 = 37.5[31.4-43.6]; V-2 = 32.6[30.6-34.6]. About the precision, the mean values were V-1 = 20.5[8.4-32.5]; V-2 = 18.4[8.2-28.5]. In both the study groups, it was possible to detect the surface beyond the finish area. CONCLUSIONS: Within the limitations of this study, vertical preparation design allows for registration of the tooth anatomy beyond the finish area with IOS. Moreover, the mean accuracy values were clinically acceptable at both 1 and 2 mm below the gingival margin.

Accuracy of the intaglio surface of 3D-printed hybrid resin-ceramic crowns, veneers and table-tops: An in vitro study.

OBJECTIVES: The present study aims to examine the influence of the build angle on the accuracy (trueness and precision) of 3D printed crowns, table-tops and veneers with a hybrid resin-ceramic material. METHODS: One crown, on table-top and one veneer were printed in five different build angles (0°, 30°, 45°, 60°, 90°) (n = 50) with the digital light processing (DLP) system (Varseo XS, Bego) using hybrid resin (Varseo Smile Crownplus A3, Bego). All printed restorations were scanned using the laboratory scanner (D2000, 3Shape) and matched onto the initial reference design in metrology software (Geomagic Control X, 3D Systems). The root mean square error (RMSE) was calculated between the scanned and reference data. The data was statistically analyzed using the Tukey multiple comparison test and Wilcoxon multiple comparison test. RESULTS: The crown group showed higher trueness at 30° (0.021 ± 0.002) and 45° (0.020 ± 0.002), and table-tops at 0° (0.015 ± 0.001) and 30° (0.014 ± 0.001) (p < 0.0001). Veneers demonstrated higher trueness at 30° (0.016 ± 0.002) (p < 0.0001). All three restoration types demonstrated the lowest trueness at a 90° build angle and portrayed deviations along the z axis. The veneer and table-top groups showed the lowest precision at 90° (veneers: 0.021 ± 0.008; table-tops: 0.013 ± 0.003). The crown group portrayed the lowest precision at 45° (0.017 ± 0.005) (p < 0.0001). CONCLUSION: The build angle of DLP-printed hybrid resin-ceramic restorations influences their accuracy. CLINICAL SIGNIFICANCE: Considering the build angle is important to achieve a better accuracy of 3D-printed resin-ceramic hybrid restorations. This may help predict or avoid the interference points between a restoration and a die and minimize the clinical adjustments.

Precise tooth design using deep learning-based templates.

OBJECTIVES: In prosthodontic procedures, traditional computer-aided design (CAD) is often time-consuming and lacks accuracy in shape restoration. In this study, we combined implicit template and deep learning (DL) to construct a precise neural network for personalized tooth defect restoration. METHODS: Ninety models of right maxillary central incisor (80 for training, 10 for validation) were collected. A DL model named ToothDIT was trained to establish an implicit template and a neural network capable of predicting unique identifications. In the validation stage, teeth in validation set were processed into corner, incisive, and medium defects. The defective teeth were inputted into ToothDIT to predict the unique identification, which actuated the deformation of the implicit template to generate the highly customized template (DIT) for the target tooth. Morphological restorations were executed with templates from template shape library (TSL), average tooth template (ATT), and DIT in Exocad (GmbH, Germany). RMSestimate, width, length, aspect ratio, incisal edge curvature, incisive end retraction, and guiding inclination were introduced to assess the restorative accuracy. Statistical analysis was conducted using two-way ANOVA and paired t-test for overall and detailed differences. RESULTS: DIT displayed significantly smaller RMSestimate than TSL and ATT. In 2D detailed analysis, DIT exhibited significantly less deviations from the natural teeth compared to TSL and ATT. CONCLUSION: The proposed DL model successfully reconstructed the morphology of anterior teeth with various degrees of defects and achieved satisfactory accuracy. This approach provides a more reliable reference for prostheses design, resulting in enhanced accuracy in morphological restoration. CLINICAL SIGNIFICANCE: This DL model holds promise in assisting dentists and technicians in obtaining morphology templates that closely resemble the original shape of the defective teeth. These customized templates serve as a foundation for enhancing the efficiency and precision of digital restorative design for defective teeth.

Accuracy of Dental Restorations Fabricated Using Milling vs 3D-Printed Molds: A Pilot Study.

PURPOSE: To compare the accuracy of 12 different dental restorations fabricated with milling or 3D-printed molds and robotically controlled casting. MATERIALS AND METHODS: Twelve dental restorations (11 inlays and onlays and 1 crown) were made per restoration type, one per each of the 12 different teeth models (total of 24 restorations). On each tooth preparation, two restorations were manufactured using different CAD/ CAM techniques: (1) milling and (2) robotically controlled casting and 3D-printed molds. In addition, twolayer restorations were manufactured with 3D-printed molds. The marginal and internal gaps were evaluated at 120 points per restoration based on micro-CT 3D imaging. Internal gaps were evaluated using a replica technique with silicone. RESULTS: Median values (interquartile ranges) for marginal gaps, middle internal gaps, and central internal gaps were significantly lower for 3D-printed mold restorations (44.3 [65.4] µm, 95.4 [96.2] µm, and 104.6 [78.1] µm) compared to milled restorations (58.4 [93] µm, 145.9 [85.8] µm, and 138.6 [65.7] µm). Internal gaps in the 3D-printed mold group were 6% to 51% smaller than in the milled group. CONCLUSIONS: The accuracy of restorations fabricated with 3D-printed molds may be preferable compared to milled restorations, except in the case of crown restoration. However, additional studies with a larger number of samples and different types of restorations are needed to confirm the results.

Accuracy of Occlusal Contacts of All-Ceramic Single Crowns Designed by Virtual Articulators from a CAD/CAM System: A Preliminary Evaluation.

PURPOSE: To compare the static and dynamic occlusion of all-ceramic single crowns designed by mechanical and virtual articulators, by evalua6ng the accuracy of occlusal contacts of prostheses designed by virtual articulators and the feasibility of clinical application of CAD/CAM virtual articulators. MATERIALS AND METHODS: Nine subjects with an average age of 27 years who needed crown repair were recruited. After preparation of the all-ceramic crowns, two zirconia crowns were designed and fabricated through digital procedures and traditional methods. The intraoral scanner, Geomagic software, and T-Scan analyzer were used to analyze the occlusal contact points, areas, and the occlusal force percentage peak before the treatment and after the two crowns were temporarily fixed. RESULTS: There was a significant difference in the number of occlusal contact points and areas between the mechanical group and control group (preoperation group), but there was no obvious difference between the virtual group and control group. The occlusal contact overlapping areas of the virtual-control group were significantly larger than those of the mechanical-control group. The occlusal force percentage peak of the tested teeth was slightly larger in the mechanical group than in the virtual group. CONCLUSIONS: The posterior single crown designed by a virtual articulator restored the intercuspal occlusal better than one designed by a mechanical articulator, and it produced less dynamic occlusal interference. This finding suggests that virtual articulators can provide guidance for the design and adjustment of the occlusal surface of posterior single crown prostheses.

DIGITAL DENTISTRY AND ITS IMPACT ON ORAL HEALTH-RELATED QUALITY OF LIFE.

Over the past 50 years, digitization has gradually taken root in dentistry, starting with computer tomography in the 1970s. The most disruptive events in digital dentistry were the introduction of digital workflow and computer-aided manufacturing, which made new procedures and materials available for dental use. While the conventional lab-based workflow requires light or chemical curing under inconsistent and suboptimal conditions, computer-aided manufacturing allows for industrial-grade material, ensuring consistently high material quality. In addition, many other innovative, less disruptive, but relevant approaches have been developed in digital dentistry. These will have or already impact prevention, diagnosis, and therapy, thus impacting patients' oral health and, consequently, their oral health-related quality of life. Both software and hardware approaches attempt to maintain, restore, or optimize a patient's perceived oral health. This article outlines innovations in dentistry and their potential impact on patients' oral health-related quality of life in prevention and therapy. Furthermore, possible future developments and their potential implications are characterized.

Effect of ceramic materials and tooth preparation design on computer-aided design and computer-aided manufacturing endocrown adaptation and retentive strength: An in vitro study.

OBJECTIVES: To evaluate how various tooth preparation designs impact the adaptation-both at the margins and internally-and the retentive strength of computer-aided design and computer-aided manufacturing (CAD/CAM) produced endocrowns. MATERIALS AND METHODS: 60 extracted human mandibular first molars were endodontically treated and assigned into three groups (n = 20) according to the tooth preparation design: Group N: butt joint design, Group F and F1 received 1- and 2-mm circumferential ferrule preparation, respectively. Endocrowns were milled using either lithium disilicate glass-ceramic (IPS emax ceramic) or monolithic zirconia. The internal and marginal adaptation of the endocrowns were evaluated using the replica technique. After cementation, the endocrowns of all test groups were dislodged axially at 0.5 mm/min using a universal testing machine. A 2-way ANOVA and the independent samples t-test (α = .05) were performed to statistically analyze the data. RESULTS: The effect of changing the design of the tooth preparation (butt joint, ferrule) on the marginal and internal gap was shown to be statistically significant (p < .05); the lower gap values were recorded at the axial followed by cervical, marginal, and pulpal floor walls in both ceramic groups regardless of the teeth preparation design. The ANOVA test revealed similar average removal forces and stresses for the two types of tested ceramic materials. CONCLUSION: IPS emax ceramic adapted better than monolithic zirconia ceramic, regardless of the preparation design. Ferrule preparation design is more retentive than butt joint preparation, regardless of the type of ceramic material used.

Influence of glazing and aging on the marginal, axial, axio-occlusal, and occlusal fit of 3-unit monolithic zirconia restorations fabricated using additive and subtractive techniques.

STATEMENT OF PROBLEM: Studies are sparse on how glazing and aging influence the fit of additively fabricated monolithic zirconia restorations. PURPOSE: The purpose of this in vitro study was to assess the effect of glazing and aging on the fit of 3-unit monolithic zirconia restorations fabricated using different techniques. MATERIAL AND METHODS: A total of 32 monolithic zirconia restorations were fabricated for a typodont model by using 4 distinct techniques (subtractive fabrication [SF], stereolithography [SLA], digital light processing [DLP], and lithography-based ceramic manufacturing [LCM]). The silicone replica approach was adopted to measure the discrepancy values for premolar and molar abutments after sintering, glazing, and 1 year of aging. The silicone replicas were sliced into mesiodistal and buccopalatal cross-sections, and digital micrographs of the cross-sections were made with a ×80 stereomicroscope. An inherent measuring program was run to record the discrepancy values (µm). Repeated-measures 2-way ANOVAs with the Bonferroni post hoc test were used to statistically analyze the acquired data. (α=.05). RESULTS: From the repeated measures 2-way ANOVAs, both the glazing×fabrication technique and the aging×fabrication technique interactions were not statistically significant (P>.05). Glazing significantly influenced premolar abutment marginal (P=.022) and occlusal (P=.007) discrepancy values, as well as molar abutment marginal discrepancy values (P=.047). Aging had a statistically significant effect on premolar abutment marginal (P=.008) and occlusal (P=.011) discrepancy values, as well as molar abutment occlusal discrepancy values (P=.039). In both the glazing and aging data, for all areas of interest, statistically significant differences were detected among the fabrication techniques (P<.05). The LCM group had the lowest discrepancy values, followed by the SLA, SF, and DLP groups. CONCLUSIONS: The LCM and SLA groups outperformed the other groups in terms of fit accuracy. The glazing and aging procedures altered the discrepancy values. The marginal discrepancy values of all groups were below the threshold of clinical acceptability (<120 µm).

Marginal Fit and Internal Adaptation of Monolithic Zirconia 3-Unit Fixed Dental Prosthesis: In Vitro Study.

PURPOSE: To compare the marginal and internal fit of monolithic zirconia (MZ) 3-unit fixed dental prostheses (FDPs) fabricated using two CAD/CAM workflows: full-chairside (FCH) and lab (LAB). MATERIALS AND METHODS: The right maxillary first premolar and first molar were prepared for MZ 3-unit FDPs on a typodont. CEREC Primescan digitized the typodont model 15 Omes. A total of 30 FDPs was fabricated using two processes: FCH (n = 15) and LAB (n = 15). FCH and LAB FDPs were designed using CEREC SW 4.5.1 and Exocad and milled using CEREC MC X and Zirkonzhan 600/V3, respectively. A fast-sintering protocol was used in both groups. A dual-scan technique was used to assess the cement space at the occlusal surface (OC), axial wall (AX), and margin (MA). Statistical analysis of the results was performed using univariate ANOVA with Scheff. post hoc test (a = .05). RESULTS: Measurements in the FCH and LAB groups were within the clinically acceptable marginal and internal fit. The fit of FCH FDPs at MA, AX, and OC was 77.50 ± 29.99 µm, 99.67 ± 21.58 µm, and 150.03 ± 30.78 µm, respectively. The fit of LAB FDPs at MA, AX, and OC was 100.27 ± 27.06 µm, 116.53 ± 17.90 µm, and 142.30 ± 19.00 µm, respectively. The difference between the two groups was not statistically significant. CONCLUSIONS: MZ 3-unit FDPs fabricated using FCH have clinically acceptable marginal and internal fit. This result verifies the ability of FCH workflow to fabricate MZ mulOunit FDPs in a single visit.

Digitally manufactured partial coverage restorations: is it time to down the impression trays or still a work in progress?

DATA SOURCES: Pubmed, EMBASE, Scopus, Web of Science and Cochrane library databases were used as the data sources for this systematic review. Manual search of the reference lists of the included studies was also conducted. STUDY SELECTION: The aim of the systematic review was to compare a fully digital workflow to a fully conventional workflow in the fabrication of partial coverage restorations. Partial coverage restorations were defined as inlays, onlays, overlays and endocrowns. Four independent calibrated reviewers screened studies that fulfilled a predefined PICOS framework. Population was specified as an abutment tooth requiring a partial coverage restoration. The intervention was a fully digital workflow compared to a fully conventional workflow. Outcomes were accuracy, marginal and internal fit, success, survival, complication rates and patient-reported outcomes. Study design included both clinical and in vitro studies. DATA EXTRACTION AND SYNTHESIS: A total of 23 articles were included in qualitative synthesis ranging from 2007 to 2021. Twenty-one of these were in vitro studies. Two authors independently reviewed the included articles, performed data extraction, and evaluated the risk of bias via an adapted Checklist for Reporting In Vitro studies (CRIS) for in vitro studies and Reporting Randomised Clinical studies (RoB2) for clinical studies. RESULTS: Seventeen studies assessed the marginal and internal fit of onlay and inlay restorations, eight of which found that a conventional workflow demonstrated improved fit compared to digital, whilst the remaining nine studies found the contrary. Differing methods were utilised across the studies to assess fit, including: the silicone replica method, microcomputed tomography, microscopy and software-based measurements. Similar fracture strengths were reported between both conventional and digital workflows in three studies. One clinical study assessed survival rates of both pressed and CAD/CAM ceramic restorations and found the survival outcomes to be similar after seven years. No studies were found that investigated patient-reported outcomes or endocrowns. CONCLUSIONS: No consensus was reached as to whether the digital or conventional workflow is better.

Influence of different convergence angles of abutment teeth and cement spaces on internal adaptation of anterior CAD-CAM fixed dental prostheses.

PURPOSE: The aim of this study was to investigate the influence of different convergence angles of abutment teeth and different cement spaces on internal adaptation of anterior fixed dental prostheses (FDPs) fabricated with a computer-aided design-computer-aided manufacturing (CAD-CAM) system. METHODS: Composite resin FDPs for 99 standardized maxillary central incisors were fabricated according to nine parameters: three total convergence angles (4 [DG4], 12 [DG12], and 20 degrees [DG20]) and three cement space settings (10 [CS10], 50 [CS50], and 90 µm [CS90]). Internal space values were measured with a cement space replica technique. The Kruskal-Wallis and Steel-Dwass tests were used to evaluate differences in the total convergence angles and luting agent spaces, respectively (α = 0.05). RESULTS: For all three cement spaces tested, the median marginal gap values between abutment teeth and FDPs decreased significantly as the total convergence angle increased (P < 0.05). For the CS10 and CS50 groups, the internal space values at the axial area increased significantly as the total convergence angles increased (P < 0.05). CONCLUSION: Total convergence angles of the abutment teeth and cement spaces affected the marginal and internal adaptation of anterior FDPs fabricated with a CAD-CAM system.

Tooth morphology, internal fit, occlusion and proximal contacts of dental crowns designed by deep learning-based dental software: A comparative study.

OBJECTIVES: This study compared the tooth morphology, internal fit, occlusion, and proximal contacts of dental crowns automatically generated via two deep learning (DL)-based dental software systems with those manually designed by an experienced dental technician using conventional software. METHODS: Thirty partial arch scans of prepared posterior teeth were used. The crowns were designed using two DL-based methods (AA and AD) and a technician-based method (NC). The crown design outcomes were three-dimensionally compared, focusing on tooth morphology, internal fit, occlusion, and proximal contacts, by calculating the geometric relationship. Statistical analysis utilized the independent t-test, Mann-Whitney test, one-way ANOVA, and Kruskal-Wallis test with post hoc pairwise comparisons (α = 0.05). RESULTS: The AA and AD groups, with the NC group as a reference, exhibited no significant tooth morphology discrepancies across entire external or occlusal surfaces. The AD group exhibited higher root mean square and positive average values on the axial surface (P < .05). The AD and NC groups exhibited a better internal fit than the AA group (P < .001). The cusp angles were similar across all groups (P = .065). The NC group yielded more occlusal contact points than the AD group (P = .006). Occlusal and proximal contact intensities varied among the groups (both P < .001). CONCLUSIONS: Crowns designed by using both DL-based software programs exhibited similar morphologies on the occlusal and axial surfaces; however, they differed in internal fit, occlusion, and proximal contacts. Their overall performance was clinically comparable to that of the technician-based method in terms of the internal fit and number of occlusal contact points. CLINICAL SIGNIFICANCE: DL-based dental software for crown design can streamline the digital workflow in restorative dentistry, ensuring clinically-acceptable outcomes on tooth morphology, internal fit, occlusion, and proximal contacts. It can minimize the necessity of additional design optimization by dental technician.

Effect of a new support design on the marginal and internal gap of additively manufactured interim crowns using direct light deposition technology.

PURPOSE: To investigate the design and location of supporting structures on the marginal and internal gap of interim restorations. MATERIALS AND METHODS: A mandibular right first molar resin tooth was prepared for a full coverage crown and scanned using a laboratory scanner (3Shape D900). The scanned data were converted into standard tessellation language (STL) format and an indirect prosthesis was designed using computer-aided design (CAD) software (exocad DentalCAD). The STL file was used to fabricate a total of 60 crowns with a 3D printer (EnvisionTEC Vida HD). The crowns were printed using E-Dent C&B MH resin and divided into 4 groups based on four different support structure designs, including supports on the occlusal (0° group), buccal and occlusal (45° group), buccal (90° group), and a new design consisting of horizontal bars placed on all surfaces and line angles (Bar) (n = 15). The silicone replica technique was used to determine the gap discrepancy. Fifty measurements were obtained for each specimen to examine the marginal and internal gaps by using a digital microscope (Olympus SZX16) at ×70 magnification. Additionally, the marginal discrepancy at different locations of the tested crowns, including buccal (B), lingual (L), mesial (M), and distal (D), as well as the maximum and minimum marginal gap intervals among groups, were analyzed. The collected data were analyzed using factorial ANOVA, followed by the Tukey HSD test for multiple comparisons (a = 0.05). RESULTS: There was a significant difference in marginal and internal gaps among the groups (p < 0.001). The buccal placement supports (90° group) had the least marginal and internal discrepancies (p < 0.001). The new design group showed the highest marginal and internal gap. The marginal discrepancy in different locations of the tested crowns (B, L, M, D) was found to be significantly different among the groups (p < 0.001). The mesial margin of the Bar group had the largest marginal gap, whereas the buccal margin of the 90° group had the lowest marginal gap. The new design had a significantly smaller difference between the maximum and minimum marginal gap intervals than other groups (p < 0.001). CONCLUSION: The location and design of the supporting structures affected the marginal and internal gaps of an interim crown. The buccal placement of supporting bars (90° printing orientation) showed the smallest mean internal and marginal discrepancies.

CAD/CAM full-mouth rehabilitation of an elderly patient: One-piece digital complete denture meets multilayered zirconia with gradient technology.

OBJECTIVE: This article highlights a CAD/CAM complete-mouth rehabilitation in an 82-year-old patient by means of a complete maxillary prosthesis and mandibular implant- and tooth-supported fixed restorations made from multilayered zirconia. CLINICAL CONSIDERATIONS: Comprehensive complete-mouth rehabilitations in elderly patients with adaptation of the occlusal vertical dimension (OVD) often present particular challenges. This applies especially when exacting functional and esthetic requirements are to be met and the treatment should not cause the patient too much effort, still ensuring the highest level of quality and efficiency and a low intervention rate. CONCLUSION: The digital approach used for the present patient allowed for an efficient treatment procedure, facilitated virtual evaluations using a face-scan, and enhanced the predictability of the prosthodontic outcome. The approach enabled some steps required in the conventional protocol to be omitted, resulting in a straightforward clinical treatment with minimal strain on the patient. CLINICAL SIGNIFICANCE: Because of the comprehensive recording of extraoral and intraoral data, for example with a facial scanner, it was possible to transfer a digital replica of the patient to the dental laboratory technician. With this protocol, many steps can be performed in the absence of the real patient.

Fit and Strength of a Three-Unit Temporary Prosthesis Made by Different Manufacturing Techniques: An In Vitro Study.

PURPOSE: To compare the fit and fracture load of temporary fixed partial prostheses fabricated by means of a conventional direct technique, milling, or 3D printing. MATERIALS AND METHODS: A maxillary right first premolar and molar were prepared on a Frasaco cast, which was then duplicated 40 times. In total, 10 provisional three-unit fixed prostheses (Protemp 4, 3M) were made using the conventional technique with a putty mold. The 30 remaining casts were scanned to design a provisional restoration using CAD software. A total of 10 designs were milled (CEREC MC X5/shaded PMMA Disk, Dentsply Sirona), while the other 20 were 3D printed with one of the two 3D printers (Asiga UV MAX or Nextdent 5100, C&B, Nextdent). Internal and marginal fit were examined using the replica technique. Next, the restorations were cemented on their respective casts and loaded until fracture using a universal testing machine. The location and propagation of the fracture were also evaluated. RESULTS: 3D printing demonstrated the best internal fit. Nextdent (median internal fit: 132 µm) was significantly better compared to the milled (median internal fit: 185 µm; P = .006) and conventional restorations (median internal fit: 215 µm; P < .001), while the fit of Asiga (median internal fit: 152 µm) was only significantly better than the conventional restorations (P < .012). The lowest marginal discrepancy was found for the milled restorations (median marginal fit: 96 µm), but this was only significant when compared to the conventional group (median internal fit: 163 µm; P < .001). The conventional restorations demonstrated the lowest fracture load (median fracture load: 536 N), which was only significant when compared to Asiga (median fracture load: 892 N; P = .003). CONCLUSIONS: Within the present in vitro study's limitations, CAD/CAM demonstrated superior fit and strength compared to the conventional technique.