Build angle effect on 3D-printed dental crowns marginal fit using digital light-processing and stereo-lithography technology: an in vitro study.

BACKGROUND: The effect of 3D printing technology and build angle on the marginal fit of printed crowns is unclear. The objective of this research was to use digital light processing (DLP) and stereo-lithography (SLA)-based 3D printing to construct single restorations with varied build angles and to analyze the crowns' marginal fit. METHODS: A prepared resin first molar was scanned utilizing an optical scanner. Three build orientations were used to construct the specimens: 0, 45, and 90º. DLP and SLA technology were used to produce the casting patterns. A digital microscope was used to measure the marginal gaps. The effect of build orientation was statistically analyzed by using Two-way ANOVA followed by pair-wise Tukey test. RESULTS: Two-way ANOVA revealed a significant effect of printer technology and build angle on the marginal discrepancy of 3D printed crowns (p < 0.001). One-way ANOVA revealed that SLA printers (55.6 [± 13.59]) showed significantly better mean [± SD] marginal discrepancy in µm than DLP printers (72 [± 13.67]) (p < 0.001). Regarding build angle, one-way ANOVA revealed significant differences between the different angles. Tukeys post-hoc test revealed that 0° (48.5 [± 9.04]) had the significantly smallest marginal discrepancy followed by 45° (62.5 [± 8.05]) then 90° (80.5 [± 8.99]) (p < 0.001). CONCLUSION: The build orientation affects the marginal discrepancy of single crowns manufactured utilizing DLP and SLA.

Effect of different fabrication workflows on the passive fit of screw-retained bar splinting two interforaminal implants: a parallel blinded randomised clinical trial.

BACKGROUND: To clinically compare the effect of the conventional and the digital workflows on the passive fit of a screw retained bar splinting two inter-foraminal implants. METHODS: The current study was designed to be a parallel triple blinded randomised clinical trial. Thirty six completely edentulous patients were selected and simply randomized into two groups; conventional group (CG) and digital group (DG). The participants, investigator and outcome assessor were blinded. In the group (CG), the bar was constructed following a conventional workflow in which an open top splinted impression and a lost wax casting technology were used. However, in group (DG), a digital workflow including a digital impression and a digital bar milling technology was adopted. Passive fit of each bar was then evaluated clinically by applying the screw resistance test using the "flag" technique in the passive and non passive situations. The screw resistance test parameter was also calculated. Unpaired t-test was used for intergroup comparison. P-value < 0.05 was the statistical significance level. The study protocol was reviewed by the Research Ethics Committee in the author's university (Rec IM051811). Registration of the clinical trial was made on clinical trials.gov ID NCT05770011. An informed consent was obtained from all participants. RESULTS: Non statistically significant difference was denoted between both groups in all situations. In the passive situation, the mean ± standard deviation values were 1789.8° ± 20.7 and1786.1° ± 30.7 for the groups (CG) and (DG) respectively. In the non passive situation, they were 1572.8° ± 54.2 and 1609.2° ± 96.9. Regarding the screw resistance test parameter, they were 217° ± 55.3 and 176° ± 98.8. CONCLUSION: Conventional and digital fabrication workflows had clinically comparable effect on the passive fit of screw retained bar attachments supported by two dental implants.

Influence of polyether ether ketone coping crown on the adaptation of implant abutment.

OBJECTIVE: To evaluate the influence of polyether ether ketone coping crown on the adaptation of implant abutment. Methods: The vitro study was conducted at the department of Prosthodontics, Hainan Stomatological Hospital, China, from October 2021 to March 2022, and comprised patients undergoing implant surgery on first molar. Patients were divided into two groups, with group A patients receiving polyether ether ketone coping crowns, and group B receiving zirconia crowns. Replica technique was used to replicate the gap between the crowns and the abutments. The thickness of the silicone film was measured under the stereomicroscope, and the gap between the groups was compared. Data was analysed using SPSS 22. RESULTS: In group A, mean marginal gap was 82.43±25.00µm, and mean overall gap was 85.45±33.75µm. In group B, the corresponding values were 65.09±11.69µm and 78.04±26.67µm. There was a significant difference in the adaptation between the groups at the marginal and overall measurement points (p<0.05). Conclusion: Marginal and internal adaptations of polyether ether ketone coping crown for abutment could be considered clinically acceptable.

Hot isostatic pressing as an alternative thermo-mechanical treatment for metallic full-arch implant-supported frameworks obtained by additive and subtractive manufacturing technology: Vertical and horizontal fit, screw removal torque, and stress analysis.

PURPOSE: To assess vertical and horizontal fit, screw removal torque, and stress analysis (considered biomechanical aspects) of full-arch implant frameworks manufactured in Ti-6Al-4V through milling, and additive manufacturing Direct Metal Laser Sintering (DMLS) and Electron Beam Melting (EBM), and the effect of the thermo-mechanical treatment Hot Isostatic Pressing (HIP) as a post-treatment after manufacturing. MATERIAL AND METHODS: Maxillary full-arch implant frameworks were made by milling, DMLS, and EBM. The biomechanical assessments were screw removal torque, strain-gauge analyses, and vertical and horizontal marginal fits. The vertical fit was assessed by the single-screw test and with all screws tightened. All frameworks were submitted to a standardized HIP cycle (920°C, 1000 bar pressure, 2 h), and the tests were repeated (α = 0.05). RESULTS: At the initial time, milled frameworks presented higher screw removal torque values, and DMLS and EBM frameworks presented lower levels of strain. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally, higher fit values were found for milled frameworks, followed by DMLS and EBM. After HIP, milling and EBM frameworks presented higher screw removal torque values; the lowest strain values were found for EBM. Using the single-screw test, milled and DMLS frameworks presented higher vertical fit values, and with all screws tightened and horizontally no differences were found. CONCLUSIONS: DMLS and EBM full-arch frameworks presented adequate values of screw removal torque, strain, and marginal fit, although the worst values of marginal fit were found for EBM frameworks. The HIP cycle enhanced the screw removal torque of milled and EBM frameworks and reduced the strain values of milled frameworks. The HIP represents a reliable post-treatment for Ti-6Al-4V dental prostheses produced by milling and EBM technologies.

Effect of blood contamination on marginal adaptation of cold ceramic and MTA angelus: a scanning electron microscopic study.

BACKGROUND: This study aimed to assess the effect of blood contamination on marginal adaptation of cold ceramic (CC) and mineral trioxide aggregate (MTA) Angelus using scanning electron microscopy (SEM). METHODS: This in vitro experimental study was conducted on 24 extracted single-rooted human teeth. After cleaning and shaping, the root canals were filled with lateral compaction technique. The apical 3 mm of the roots was cut, and cavities with 3 mm depth were created at the apex. The teeth were randomly assigned to two group (n = 12) for the application of CC and MTA Angelus as retrograde filling materials. CC and MTA Angelus were prepared by mixing the powder with blood, and applied in the cavities. After 24 h, their marginal adaptation to the canal walls was assessed by SEM. Data were statistically analyzed by t-test (alpha = 0.05). RESULTS: The mean marginal gap was 8.98 µm in the CC, and 16.26 µm in the MTA Angelus group; this difference was statistically significant (P < 0.001). CONCLUSIONS: The present in vitro study revealed that following complete blood contamination of powder, CC showed significantly superior marginal adaptation than MTA Angelus as shown by SEM assessment.

Comparison of marginal accuracy in two different materials used in provisional crown and bridge - an in vitro experimental study.

OBJECTIVE: To determine the difference in the marginal accuracy at buccal, lingual, mesial and distal margins of temporary crowns fabricated with bisacryl-based temporary crown material. METHODS: The in-vitro, experimental, laboratory-based study was conducted at the Aga Khan University, Karachi, from September to December 2019, and comprised two bisacryl-based temporary crown material, Integrity and Protemp 4, which were used to fabricate a sample of 24 temporary crowns. A pre-operative polyvinyl siloxane impression served as a template for temporary crown fabrication. A right mandibular molar tooth on a typodont was prepared to receive a crown. The provisional crown material was syringed onto the template and was allowed to cure. All four surfaces of the crown were observed under a stereomicroscope equipped with digital single-lens reflex camera at 25.6x magnification. An image of each surface was captured and a photographic record was maintained. An image processing software was used for the measurement of marginal discrepancy. Marginal accuracy among the four surfaces was assessed. Data was analysed using SPSS 23. RESULTS: Mean marginal discrepancy for provisional crowns fabricated with Protemp 4 and Integrity was 410±222µm and 319±176µm, respectively. The marginal discrepancy between the two groups was statistically significant (p=0.027), with buccal margin exhibiting the most discrepancy (p<0.01). CONCLUSIONS: Integrity showed less microleakage than Protemp 4. Among all the walls, the buccal wall showed the most microleakage. Marginal accuracy was found to be dependent upon the type of provisional crown material and the side of the prepared axial wall.

Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials.

AIMS: This study aimed to assess the marginal and internal adaptation of provisional crowns fabricated from polymethyl methacrylate (PMMA) blocks by the computer-aided design/computer-aided manufacturing (CAD/CAM) system, autopolymerizing PMMA, and acrylic base composite resin. MATERIALS AND METHODS: In this in vitro experimental study, a brass die was obtained, and provisional crowns were fabricated in three groups using Teliocad PMMA blocks by the CAD/CAM system, Tempron GC auto-polymerizing PMMA, and Bisico acrylic base composite resin (n = 7 in each group). The provisional crowns were coded and randomly placed on the die. Their marginal adaptation was evaluated under a stereomicroscope at 40× magnification, while their internal adaptation was assessed by the replica technique. Data were analyzed by one-way analysis of variance (ANOVA) (α = 0.05). RESULTS: The mean marginal gap was the highest in autopolymerizing PMMA and the lowest in the CAD/CAM PMMA group (p < 0.05). The mean marginal gap in the autopolymerizing PMMA group was significantly higher than that in the resin material (p = 0.014) and CAD/CAM PMMA (p = 0.000) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.13). The mean internal gap was the highest in autopolymerizing PMMA group and the lowest in CAD/CAM PMMA group (p < 0.05). The mean internal gap in autopolymerizing PMMA group was significantly higher than that in composite resin (p = 0.002) and CAD/CAM PMMA (p = 0.00) groups. The difference between the resin material and CAD/CAM PMMA groups was not significant (p = 0.322). CONCLUSION: Computer-aided design/Computer-aided manufacturing PMMA provisional crowns showed the highest marginal and internal adaptation followed by acrylic base resin material crowns. CLINICAL SIGNIFICANCE: Computer-aided design/computer-aided manufacturing PMMA crowns demonstrate superior marginal and internal adaptation compared with autopolymerizing PMMA and acrylic base composite resin crowns, suggesting CAD/CAM technology's potential for enhancing clinical outcomes. How to cite this article: Jalalian E, Younesi F, Golalipour S, et al. Assessment of Marginal and Internal Adaptation in Provisional Crowns Utilizing Three Distinct Materials. J Contemp Dent Pract 2023;24(11):853-858.

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 training on time efficiency and marginal adaptation of computer-aided design/computer-aided manufacturing crowns among dental students.

INTRODUCTION: The computer-aided design/computer-aided manufacturing (CAD/CAM) technology has revolutionised dentistry at present. An operator's skills can affect the overall clinical duration and marginal accuracy of the prosthesis fabricated through this workflow. The aim of this study was to assess the effect of CAD/CAM hands-on training compared with that of a self-instructional video on the performance of dental students in digital impression and fabrication of a CAD/CAM crown. METHODS: In this cross-sectional study, 30 undergraduate dental students were shown a CEREC demonstration video. Each operator then captured a digital impression using the intra-oral scanner, and a crown was subsequently milled. All participants underwent a training course before repeating the process. Marginal discrepancy for each crown on its abutment tooth was measured before and after training using a stereomicroscope and was evaluated using Wilcoxon signed rank test. The duration taken for the process was recorded before and after training and evaluated using paired t-test. RESULTS: The overall mean ±standard deviation marginal adaptation for the CEREC crowns was 78.15 ± 42.83 µm before training and 52.41 ± 17.12 µm after training. The Wilcoxon signed rank test found significant difference (p < .05) in terms of marginal adaptation of crowns fabricated before and after training. Paired t-tests showed that the time efficiency after training significantly improved compared with that before training. CONCLUSIONS: Training with guided feedback is crucial to improve the time efficiency of making a digital impression and marginal adaptation of fixed prosthesis using the CAD/CAM technology.

[Marginal features of CAD/CAM laminate veneers with different materials and thicknesses].

OBJECTIVE: To analyze the marginal roughness and marginal fitness of chairside computer-aided design and computer-aided manufacturing (CAD/CAM) laminate veneers with different materials and thicknesses, and to provide a reference for the clinical application of laminate veneers. METHODS: The butt-to-butt type laminate veneers were prepared on resin typodonts, the preparations were scanned, and the laminate veneers were manufactured by chairside CAD/CAM equipment. The laminate veneers were divided into four groups (n=9) according to the materials (glass-matrix ceramics and resin-matrix ceramics) and thickness (0.3 mm and 0.5 mm) of the veneers, with a total of 36. The marginal topo-graphies of each laminate veneer were digitally recorded by stereomicroscope, and the marginal rough-nesses of the laminate veneers were determined by ImageJ software. The marginal fitness of the laminate veneers was measured by a fit checker and digital scanning and measuring method. At the same time, the mechanical properties of glass-matrix ceramic and resin-matrix ceramic bars (n=20) were tested by a universal testing device. RESULTS: The marginal roughness of 0.3 mm and 0.5 mm glass-matrix ceramic laminate veneers was (24.48±5.55) µm and (19.06±5.75) µm, respectively, with a statistically significant difference (P < 0.001). The marginal roughness of 0.3 mm and 0.5 mm resin-matrix ceramic laminate veneers was (6.13±1.27) µm and (6.84±2.19) µm, respectively, without a statistically significant difference (P>0.05). The marginal roughness of the glass-matrix ceramic laminate veneers was higher than that of the resin-matrix ceramic laminate veneers with a statistically significant difference (P < 0.001). The marginal fitness of 0.3 mm and 0.5 mm glass-matrix ceramic laminate veneers were (66.30±26.71) µm and (85.48±30.44) µm, respectively. The marginal fitness of 0.3 mm and 0.5 mm resin-matrix ceramic laminate veneers were (56.42±19.27) µm and (58.36±8.33) µm, respectively. There was no statistically significant difference among the 4 groups (P>0.05). For glass-matrix ceramics, the flexural strength was (327.40±54.25) MPa, the flexural modulus was (44.40±4.39) GPa, and the modulus of resilience was (1.24±0.37) MPa. For resin-matrix ceramics, the flexural strength was (173.71±16.61) MPa, the flexural modulus was (11.88±0.51) GPa, and the modulus of resilience was (1.29±0.27) MPa. The flexural strength and modulus of glass-matrix ceramics were significantly higher than those of resin-matrix ceramics (P < 0.001), but there was no statistically significant difference in the modulus of resilience between the two materials (P>0.05). CONCLUSION: The marginal roughness of CAD/CAM glass-matrix ceramic laminate veneers is greater than that of resin-matrix ceramic laminate veneers, but there was no statistically significant difference in marginal fitness among them. Increasing the thickness can reduce the marginal roughness of glass-matrix ceramic laminate veneers, but has no effect on the marginal roughness of resin-matrix ceramic laminate veneers.

A Comparative Study of the Accuracy of Dental CAD Programs in Designing a Fixed Partial Denture.

PURPOSE: Error testing at each stage of prosthetic manufacturing remains relatively underdeveloped for computer-aided design/computer-aided manufacturing methods, and no experimental studies have validated the computer-aided design programs. This study aimed to test the accuracy and trueness of the computer-aided design of a three-unit fixed prosthesis. MATERIALS AND METHODS: Three computer-aided design programs (Exocad, Dental System™, and inLab 16) were tested on the designs of a three-unit fixed partial denture, and a three-dimensional analysis program was used to calculate the internal clearance error for the computer-aided design prostheses. The Kruskal-Wallis and Dunn's post hoc tests were used to reveal significant differences in trueness between the three computer-aided design programs (α < 0.05). RESULTS: Dental System™ showed the lowest mean error values for #24 and #26 at the mesial margin (both 0 µm), mesial wall (0.10, 0.12 µm, respectively), occlusal surface (-0.05, 0.10 µm), distal wall (0.23, -0.02 µm), and distal margin (both 0 µm). In sum, except for the mesial margin and distal margin site of tooth #26, the mean error value of Dental System™ was statistically the lowest, followed by those of Exocad and inLab 16 (p < 0.003). CONCLUSIONS: The accuracy of computer-aided design differed according to the type of computer-aided design program. Dental System™ achieved the best trueness at the margins, axial walls, and occlusal surface, followed by Exocad and inLab 16.

The Influence of a Flexible Model on the Marginal Adaptation of Inlay Composite Restorations: A MicroCT Analysis.

The aim of this study was to evaluate the influence of flexible models on the marginal adaptation of indirect resin composite restorations. Thirty-six cavity preparations were made for class II restorations in permanent molar teeth. Three groups (n=12) were defined following three impressions/model material combinations: G(STONE), polyvinylsiloxane, and type IV stone model, as a control group; G(IMPRESSIONPVS), alginate and flexible polyvinylsiloxane; G(MODELPVS), alginate and flexible polyvinylsiloxane for models. All restorations were positioned on their respective teeth and evaluated by micro-computed tomography. Absolute marginal discrepancies were measured digitally (ImageJ). The results were compared using one-way ANOVA (p⟨ 0.05). The mean ± SD absolute marginal discrepancy of indirect resin composite restorations made from flexible and rigid stone models was as follows: G(STONE), 206 (±79.95) µm; G(IMPRESSIONPVS), 221.50 (±61.73) µm; G(MODELPVS), 203.25 (±65.93) µm. Absolute marginal discrepancies were not significantly influenced by the flexible and rigid stone models (p=0.78). The flexible or rigid stone model did not influence the marginal adaptation of the indirect resin composite restorations.

Bonding and wear properties of self-adhesive flowable restorative materials.

The purpose of this study was to evaluate the bonding and wear properties of self-adhesive flowable restorative materials. Five self-adhesive flowable restorative materials were used. The study parameters were: (i) shear bond strengths; (ii) microleakage; (iii) occlusal wear; and (iv) qualitative evaluation of the bonding interface. The range of shear bond strengths of the materials was as follows: 7.4-12.2 MPa to ground enamel, 22.5-32.5 MPa to etched enamel, and 1.3-4.2 MPa to dentin. The microleakage scores of the materials did not show any statistically significant differences regardless of the presence or absence of etching. The wear facets on the materials showed 0.099-0.447 mm3 of volume loss and 148.6-365.3 µm maximum depth, with statistically significant differences between materials. Scanning electron microscopic images of the interfaces of the materials showed good adaptation regardless of substrate. The bonding and wear properties of self-adhesive flowable restorative materials were still limited and showed lower values than previously reported results for nanofilled composites with an adhesive system. Selective enamel etching can improve the bonding performance of these materials.

Micro-CT and Microscopy Study of Internal and Marginal Gap to Tooth Surface of Crenelated versus Conventional Dental Indirect Veneers.

Background and Objectives: Ceramic veneers represent the most appropriate treatment option for minimally invasive aesthetic rehabilitation. For long-term clinical success, the accurate marginal and internal adaptation of dental restorations are of paramount importance. The aim of this in vitro study is to assess the effect of a novel (patented) design of veneers compared to conventional ones on their marginal and internal gap to the prepared tooth surface. Materials and Methods: Twenty-four lithium disilicate ceramic veneers are obtained using Computer-Aided-Design (CAD) and then milled using Computer-Aided-Manufacturing (CAM). The samples are divided into two groups: 12 conventional (CO) veneers (i.e., with a linear marginal contour) and 12 crenelated (CR) veneers, the latter with the novel sinusoidal marginal design. All samples are bonded to frontal teeth, and the adhesive interfaces are analyzed using two methods, optical microscopy and micro-Computed Tomography (CT): the former for the accuracy of the marginal gap and the latter for the internal gap (as well as for the homogeneity of the luting cement) of ceramic veneers. Results: STATA and one-way ANOVA tests reveal significant differences between CO and CR veneers: (i) the marginal gap is smaller for CR (64 µm) than for CO veneers (236 µm); (ii) the internal adaptation is better for CR veneers: for a cement width of up to 120 µm, the covered surface for the CR group is 81.5%, while for the CO group it is 64.5%; (iii) the mean of the porosities within the cement is not significantly different (3.4·106 µm3 for CO and 3.9·106 µm3 for CR veneers), with a higher standard deviation for the CO group. Analytical modeling is achieved for internal gaps using the micro-CT results. The characteristic functions obtained allow us to compare the volume of luting cement for the two types of veneers. Conclusion: The novel veneers design produces an improvement in the marginal and internal adaptation of the restorations to the prepared tooth surface. Thus, it provides favorable premises for better clinical performances.

Synthesis, characterization, and aging resistance of the polyurethane dimethacrylate layer for dental restorations.

In this study, polyurethane dimethacrylate (PUDMA) was synthetized from different components and incorporated into a direct resin composite restoration system with the aim to buffer tooth-resin interfacial stresses and maintain the marginal adaptation. The tensile strength, elongation at fracture (ε), and thermal stability of the PUDMA layer were characterized, showing a tensile strength of 22 MPa, an ε of 112%, and a thermal decomposition temperature of about 282°C. In addition, the degree of conversion, water sorption/solubility, hydrophobicity, microtensile bond strength (µTBS), marginal leakage, and cytotoxicity in vitro were evaluated for the PUDMA layer. The data were analyzed using one-way ANOVA, except for leakage depths (which were analyzed using the Wilcoxon paired-rank test). The level of significance was set at 0.05. Compared with dental adhesives, PUDMA displayed a higher degree of conversion, lower water sorption/solubility, and improved hydrophobicity and biocompatibility in vitro. After thermocycling, the µTBS of the restoration system containing PUDMA had increased compared with the µTBS at 24 h. Restorations containing PUDMA showed lower leakage depths than those which did not contain PUDMA. In conclusion, because of its hydrophobic and elastic nature, the PUDMA layer, when used as an intermediate between tooth and resin restoratives, may buffer interfacial stresses, improve the stability and durability of the bonding interface, and reduce microleakage.

Four-year clinical prospective follow-up of resin composite restoration after selective caries removal using Er:YAG laser.

OBJECTIVES: The aim of this study was to longitudinally evaluate, after a 4-year period, the clinical longevity of composite resin restoration compared to the baseline, after selective caries removal in permanent molars using Er:YAG laser or bur preparation with biomodification of dentin with the use of chlorhexidine. METHODS: Selective caries removal was performed on 80 teeth of 20 individuals who each had at least four active carious lesions. These lesions, located on occlusal surfaces of permanent molar counterparts, were removed using (i) Er:YAG laser biomodified with chlorhexidine, (ii) Er:YAG laser and application of deionized water, (iii) bur preparation biomodified with chlorhexidine, and (iv) bur preparation and application of deionized water. At the end of 4 years, 64 of the 80 restorations were evaluated in 16 individuals (n = 16). The restorations were evaluated, both clinically and photographically, using scanning electron microscopy (SEM) and pulp vitality analysis. The experimental data were statistically evaluated by kappa, Fisher's, and chi-square tests, with a significance level of 5%. The Kaplan-Meier test and the Cox regression analysis were used to evaluate the survival of the restorations. RESULTS: After 4 years of follow-up, there was a statistically significant difference in marginal discoloration criteria for all of the groups evaluated. For marginal adaptation criteria, there was a statistically significant difference for the Er:YAG laser group biomodified with chlorhexine (p = 0.050). For clinical and radiographic evaluation of pulp vitality, there were no statistically significant differences among the groups (p = 0.806). CONCLUSION: Er:YAG laser can be used for selective caries removal, regardless of dentin biomodification with chlorhexidine or application of deionized water, once it produced promising results in composite resin restorations after 4 years of follow-up, according to the criteria evaluated. The selective caries removal using Er:YAG laser or bur and the biomodification of dentin with the use of chlorhexidine did not influence the survival of composite resin restorations after the 4-year follow-up period. CLINICAL RELEVANCE: Composite resin restorations applied after selective caries removal using Er:YAG laser or burs, regardless of dentin biomodification with the use of chlorhexidine or application of deionized water, showed adequate clinical behavior after 4 years of follow-up.

Adaptation accuracy of milled lithium disilicate crowns: A 2D and 3D microCT analysis.

OBJECTIVE: Evaluate the effects of the scanning techniques and the crystallization in the internal and marginal adaptation of milled lithium disilicate crowns by two techniques computer microtomography analysis. MATERIALS AND METHODS: Sixteen polyurethane teeth prepared for a complete crown were divided into two groups according to the scanner method (n = 8): indirect (IND), dental stone models were scanned with laser-surface scanner, and direct (DIR), digital typodont creates with an intraoral scanner. Internal and marginal gap were evaluated by micro-computed tomography (microCT). The replica technique (RT) was applied for analysis of total volume (TV) and marginal volume (MV) gap in microCT. The data showed normal distribution (Shapiro-Wilk test). One-way ANOVA (scanner techniques) with repeated measures (crystallization) was performed. Multiple comparisons were performed with Bonferroni adjustment (α = .05). RESULTS: The axial gap showed a significant difference between the times (P = .017) for lower values after crystallization. The vertical marginal gap presented a significant difference in times for higher value after crystallization (P = .001). The marginal horizontal gap IND was greater than DIR after crystallization (P = .001) and IND before lower than after crystallization. For TV was not significant difference and MV in DIR was reduction (P = .002) after crystallization. CONCLUSION: Crystallization changes the relationship between the crown and tooth, reducing internal gap and preventing the adequate fit in indirect and direct scanning. CLINICAL SIGNIFICANCE: The measure gap under technological methodology is useful for adjust clinical parameters prosthetic in the CAD/CAM and the applicability of the new possibilities of analysis.

Evaluation of the dimensional accuracy of a manufactured dental prosthesis in relation to its computer-aided model.

AIM: Currently, there is no reliable methodology to evaluate the dimensional conformity of dental prostheses manufactured through a digital shaping process. In the CAD/CAM method, the digital design of the prosthesis is considered as a reference, and it is crucial to reproduce it perfectly during the manufacturing process. Therefore, the aim of this study was to offer a comparison between a CAM prosthesis and its design model by superimposing the CAD model with the digitization of the manufactured prosthesis. MATERIALS AND METHODS: The metrological inspection developed in this study and presented in this article involved a comparison of the points cloud obtained by micro-computed tomography (micro-CT) and the CAD model of the prosthesis. First, an estimation of all inspection-method induced measurement errors was carried out, in which the measurement errors were assessed by proceeding to the dimensional inspection of a reference object of known dimensions. Then, the metrological inspection was extrapolated to a dental prosthesis. RESULTS: The estimation of measurement errors presented satisfying results compared with the usual metrological protocols developed by the dentistry research community. The dimensional deviation was estimated at 0.31% and the form deviation at 0.165 µm between the Gaussian sphere and the certified ball. The inspection of the manufactured surfaces revealed under-milled areas on the occlusal face, particularly on the anatomical fossae, and an irregular margin limit compared with its smooth design. CONCLUSION: A reliable micro-CT evaluation of the dimensional accuracy of a manufactured dental prosthesis compared with the CAD model demonstrated the performance level of CAD/CAM systems. The evaluation reliability was confirmed by the estimation of prior measurement errors. This estimation is essential for the metrological analysis.

Vertical Marginal Discrepancy of Retrievable Cement/Screw-retained Design and Cement-retained Implant-supported Single Metal Copings.

AIM: To compare the vertical marginal discrepancy of retrievable cement/screw-retained design (RCSRD) and cement-retained (CR) implant-supported single metal copings cemented on implant abutments. MATERIALS AND METHODS: Single metal copings were fabricated for 20 4.5 × 10 mm titanium dental implants. Two groups of 10 implants each were randomly allocated. One group received RCSRD metal copings and the other group received CR metal copings. Both types of restorations were fabricated on solid abutments with 5.5 mm of diameter. The copings were cemented with resin cement. After the cementation procedure, cement excess was carefully removed in both groups. Inspections of coping-abutment vertical marginal discrepancy were measured using scanning electronic microscopy (SEM) under 800× magnification. The independent sample Student's t test was used to detect differences between groups (p < 0.05). RESULTS: The RCSRD implant-supported metal coping group (57.80 ± 2.34 µm) showed statistically better vertical marginal discrepancy than the CR implant-supported metal coping group (64.40 ± 2.23 µm) (p = 0.001). CONCLUSION: The RCSRD implant-supported metal copings offer less vertical marginal discrepancy than the CR copings group. This new technique would decrease the marginal discrepancy with less bacterial filtration and biomechanical problems. CLINICAL SIGNIFICANCE: Retrievable cement/screw-retained design is another alternative technique for dental implant rehabilitation that combines the advantages of CR and SR prostheses. The hybrid design offers less vertical marginal discrepancy for better control of bacterial filtration and biomechanical problems.

In Vivo and In Vitro Comparison of Internal and Marginal Fit of Digital and Conventional Impressions for Full-Coverage Fixed Restorations: A Systematic Review and Meta-analysis.

PURPOSE: This study aims to evaluate digital and conventional impressions for full-coverage restorations in terms of marginal and internal discrepancies. STUDY SELECTION: The analysis included in vivo and in vitro studies reporting the marginal or internal gap of full-coverage restorations that provide both the conventional and digital impression. The PubMed, Cochrane Trials, and Scopus databases were searched. The quality of clinical trials was rated using Cochrane Collaboration's tool, and the quality of the evidence was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation tool. Heterogeneity among the studies was evaluated, and a meta-analysis with subgroup analysis was conducted whenever it was possible. RESULTS: Thirty-three articles (8 prospective clinical trials and 26 in vitro studies) were selected to extract data after applying the predefined selection criteria. The standard mean difference (SMD) of the meta-analysis for marginal adaptation was -0.76 (95% confidence interval: -1.23 to -0.29) and -0.59 (95% confidence interval: -0.93 to -0.24) for in vitro and in vivo studies, respectively, indicating digital impressions provided significantly less marginal gap than conventional impressions in in vitro studies (P = .002). The impression technique did not significantly influence the internal adaptation. CONCLUSIONS: Differences in marginal adaptation between the digital and conventional groups are not significant for in vivo studies, but for in vitro studies, the digital impression resulted in better marginal adaptation. Based on the Grading of Recommendations, Assessment, Development, and Evaluation approach for marginal adaptation, clinical studies were classified as high confidence and in vitro studies were graded moderate because of the inconsistency. Furthermore, high-quality studies are needed to confirm our results (the International Prospective Register of Systematic Reviews; CRD42017077925).