Marginal Discrepancy Research Articles

Effect of virtual cement space and restorative materials on the adaptation of CAD-CAM endocrowns.

This study aimed to evaluate the effect of virtual cement space and restorative materials on the fit of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns. A mandibular first molar tooth model received a butt joint margin endocrown preparation with a 2-mm occlusal thickness. Then, using a 3D-printing system, 120 copies of this prepared die were printed and assigned equally to three groups with different cement space settings (30, 60, and 120μm) during the chairside CAD design. In the milling process, CAD-based models with a particular space setting were subdivided into four groups (n = 10) and fabricated from different CAD-CAM materials: Vita Suprinity (VS), Celtra Duo (CD), Lava Ultimate (LU), and Grandio blocs (GR). Finally, the endocrowns were stabilized over their corresponding models with siloxane and subjected to micro-computed tomography to measure the fit. The cement space that was predesigned at 30μm generated the largest marginal discrepancy (from 144.68 ± 22.43μm to 174.36 ± 22.78μm), which was significantly different from those at 60μm and 120μm (p < 0.001). The combination of VS or CD with a pre-setting cement space of 60μm and the combination of LU or GR with a cement space of 120μm showed better agreement between the predesigned and actual measured marginal gap widths. For internal adaptation, only the cement space set to 30μm exceeded the clinically acceptable threshold (200μm). The setting of the cement space and restorative material significantly affected the marginal adaptation of CAD-CAM endocrown restorations. Considering the discrepancy between design and reality, different virtual cement spaces should be applied to ceramic and resin composite materials.

Effect of Preparation Design on Marginal Integrity and Fracture Resistance of Endocrowns: A Systematic Review.

Objectives: Endocrown restorations were introduced for endodontically treated teeth as a conservative treatment. However, data about the effect of preparation design on marginal integrity and fracture resistance of endocrowns are lacking. The purpose of this systematic review was to investigate the effect of preparation design of endocrown restorations on marginal integrity and fracture resistance. Materials and Methods: Based on PICO question and the search terms, PubMed, Embase, Scopus, and the Cochrane Library were searched. After including studies matched to predefined inclusion and exclusion criteria, the extracted data were tabulated in a table provided by the authors. Two reviewers assessed the methodological quality of each included study independently. Ten articles were selected for extracting the quantitative data. All included studies were in vitro. The potential risk of bias of the selected studies was assessed using the modified MINORS scale. Results: Four studies assessed the marginal adaptation, five studies evaluated the fracture resistance and just one investigated both the marginal integrity and fatigue resistance of the specimens. The evaluated influencing items in preparation design were as follows: cavity depth, occlusal thickness, ferrule effect, internal divergence angle, type of finish line, and adding vents inside pulp chamber. Meta-analysis could not be done due to heterogeneity of preparation designs and evaluation methods. Conclusion : Marginal discrepancy of endocrowns is intensified with adding preparation features, higher cavity depth and increasing the divergence. Fracture resistance of endocrowns is increased with more occlusal reduction and cavity depth. However, it is still beyond the normal clinical force range.

Comparison of the accuracy of resin-composite crowns fabricated by three-dimensional printing and milling methods.

This study aimed to compare the dimensional accuracies of three-dimensional (3D)-printed and milled resin-composite crowns, and to determine acceptable abutment-tooth shapes for printing. Four first-molar abutment models were prepared: the master model form and three models with sharp occluso-axial line angles. Crowns were designed on each abutment using computer-aided design software. The drill-offset value was set at 0.0 or 0.5 mm to evaluate the effect on the dimensional accuracy of milling. A digital light processing-based 3D printer was used to fabricate 3D-printed crowns. Milled crowns were fabricated by wet-milling. The trueness was evaluated by superimposing the design data. Regardless of the abutment form, 3D-printed crowns showed higher accuracy with fewer marginal discrepancies than milled crowns. Milled crowns showed significant dimensional deviations, especially at cusps. Moreover, offset correction resulted in grooves on the internal surface of milled crowns with negative deviations, which were especially evident in crowns for the sharp models.

Reliability of Polyetherketoneketone as Definitive Implant-Supported Bridges in the Posterior Region—An In Vitro Study of the Ultimate Fracture Load and Vertical Marginal Discrepancy after Artificial Aging

Purpose: This study aims to investigate the ultimate fractural strength and marginal integrity of a three-unit implant-supported fixed partial denture (FPD) framework fabricated of polyetherketoneketone (PEKK) after simulated five-year clinical aging. Materials and Methods: Twelve FPD frameworks were milled (n = 6 per group). All experimental frameworks were cemented on identical stainless-steel abutment models and subjected to five years of clinically simulated thermomechanical aging. The vertical marginal gap values were analyzed using a scanning electron microscope before and after being subjected to each aging condition. A universal testing machine was used to evaluate the ultimate fracture load. Results: A significant increase in marginal gap values of the PEKK group was observed after five years of simulation aging (p &lt; 0.001), while no significant difference was seen in the titanium group (p = 0.071). After thermocycling, the PEKK group showed a higher statistically significant mean marginal gap value (84.99 + 44.28 μm) than before (81.75 + 44.53 μm). The titanium group exhibited superior mechanical strength, with a fracture load significantly higher than that of the PEKK group (3050 + 385.30 and 1359.14 + 205.49 N, respectively). Conclusions: Thermocycling affects the marginal gap discrepancy of PEKK restoration. However, the mean vertical marginal gap values in PEKK and titanium groups after a five-year clinical aging simulation were clinically acceptable. The ultimate fracture load values were higher than the maximum bite force reported in the posterior region. Thus, PEKK could serve as a suitable alternative material to metal in the framework of fixed dental prostheses.

Marginal and Internal Misfit of Occlusal Veneers Made in Resin-matrix Ceramics.

Considering that misfit is a significant predictor of the clinical success of indirect restorations, the objective of this study was to evaluate the marginal and internal misfit of two computer-aided design and manufacturing (CAD/CAM) RMC ceramic materials used as occlusal veneers (OVs) of different thicknesses. A CAD model of a mandibular first molar was obtained and OV preparations 0.5-, 1.0-, and 1.5-mm thick were modeled and milled in two different materials (n=10/group): resin nanoceramic (RNC) and polymer-infiltrated ceramic network (PICN). Using the same CAD model, tooth preparations were milled in fiber-reinforced epoxy resin (n=20/thickness). The marginal and internal misfit of the restorations was assessed by X-ray microtomography. The measurements of the marginal gap (MG) and absolute marginal discrepancy were performed in two locations on each slice, whereas internal gap (IG) measurements were performed at ten locations on each slice. The data obtained were analyzed using two-way analysis of variance and Tukey post-hoc tests (α=0.05). No significant effect was attributable to the material type or material-thickness interaction for the MG, absolute marginal discrepancy (AMD), or IG (p>0.05). However, the thickness significantly affected the IG of the restorations (p<0.05). CAD/CAM RNC and PICN systems presented similar MG and AMD for OVs 0.5-, 1.0-, and 1.5-mm thick. However, the IG varied between thicknesses.

Marginal discrepancy and fracture load of thermomechanically fatigued crowns fabricated with different CAD-CAM techniques.

To assess the effect of CAD-CAM technique (monolithic, CAD-on, or CAD-on cemented) and thermomechanical fatigue on the marginal discrepancy and fracture load of ceramic crowns. A total of 90 brass master dies were fabricated to investigate marginal adaptation and fracture load. A mandibular first molar crown's median measurements were loaded into CAD software and divided into 2 crown design groups: Monolithic (M)(IPS e.max zirCAD)(n= 30) or CAD-on core (IPS e.max zirCAD) and lithium disilicate veneer (IPS e.max CAD) (n= 60). The crowns and cores were milled, seated on their respective dies, and marginal discrepancy values were measured by using microcomputed tomography. After veneers were milled, the cores in the veneer groups were divided into 2 groups; veneers bonded with fusion glass-ceramic (IPS e.max CAD Crystal) in CAD-on group (CO) and CAD-on cemented group (CO-C) where veneers were cemented (RelyX U200) onto cores (CO-C). The marginal discrepancy measurements were remade and the crowns were subjected to thermomechanical fatigue (TMF) by using a chewing simulator and thermocycling (5-55°C, 1,200,000 cycles). Marginal discrepancy measurements were repeated and the crowns were subjected to fracture load test by using a universal test device. Data were analyzed statistically by analysis of variance (ANOVA) and Tukey's honestly significant difference test (α= 0.05). All crown groups had similar marginal discrepancy before veneering. Veneering and cementation on die increased the marginal discrepancy of crowns in cemented CAD-on group. Thermomechanical fatigue increased the marginal discrepancy of both CAD-on groups. Monolithic crown group had the lowest marginal discrepancy after thermomechanical fatigue (p < 0.001), and the highest fracture load (p < 0.001) CONCLUSIONS: Fabrication technique affected the marginal fit and fracture load of CAD-CAM crowns after thermomechanical fatigue. All crowns survived the thermomechanical fatigue test without dislodgement or fracture. Monolithic crowns had the best fit and highest fracture load after fatigue testing. The CAD-on systems had similar marginal discrepancies, and static loading reproduced veneer chipping.

Vertical Marginal Discrepancy Performance of a CAD-CAM System with Multiple Users.

The purpose of this evaluation was to evaluate the vertical marginal discrepancies of a computer-aided design-computer-aided manufacture (CAD-CAM) system used by different providers at separate time intervals. Lithium disilicate monolithic crowns on mandibular third molars were fabricated by three different providers inexperienced in digital dentistry. Using a precision rotary stage mounted on a digital recording microscope, the crown vertical marginal discrepancy was assessed using 160× magnification at 5-degree intervals around the crown marginal circumference for a total of 72 measurements per specimen. In addition to mean vertical marginal discrepancy, the maximum vertical marginal discrepancy, and its location as well as the percent of closed marginal assessments, were assessed. Mean data was analyzed using Kruskal-Wallis and Dunn post hoc testing at a 95% level of confidence (α=0.05). The mean marginal vertical discrepancy for all specimens was 21.1 ± 5.5 μm and a significant difference (p=0.0016) existed between groups but with noted wide similarity overlap. No difference (p=0.65) was observed with the mean closed margin percentage, but a significant difference (p=0.0012) existed in the observed maximum marginal discrepancy between groups. The 2-mm axial wall height (AWH), 20-degree total occlusal convergence (TOC) had significantly less (p<0.017) mean vertical marginal discrepancies than the 4-mm AWH, 20-degree TOC, and the 3-mm AWH, 16-degree TOC groups with the remaining groups similar (p>0.147). The plotted location of the specimen's maximum vertical discrepancy suggests a potential pattern amid the 360-degree margin circumference. Under the conditions of this study, CAD-CAM-derived monolithic lithium disilicate ceramic crowns fabricated by different clinicians demonstrated mean vertical marginal discrepancy results that were less than the suggested maximum clinically acceptable values. A potential for patterns of marginal discrepancy results was identified and deserves further evaluation. Results should be interpreted with caution as in vitro methodologies vary and do not directly correlate with clinical conditions.

Domain Adaptation Preconceived Hashing for Unconstrained Visual Retrieval.

Learning to hash has been widely applied for image retrieval due to the low storage and high retrieval efficiency. Existing hashing methods assume that the distributions of the retrieval pool (i.e., the data sets being retrieved) and the query data are similar, which, however, cannot truly reflect the real-world condition due to the unconstrained visual cues, such as illumination, pose, background, and so on. Due to the large distribution gap between the retrieval pool and the query set, the performances of traditional hashing methods are seriously degraded. Therefore, we first propose a new efficient but transferable hashing model for unconstrained cross-domain visual retrieval, in which the retrieval pool and the query sample are drawn from different but semantic relevant domains. Specifically, we propose a simple yet effective unsupervised hashing method, domain adaptation preconceived hashing (DAPH), toward learning domain-invariant hashing representation. Three merits of DAPH are observed: 1) to the best of our knowledge, we first propose unconstrained visual retrieval by introducing DA into hashing for learning transferable hashing codes; 2) a domain-invariant feature transformation with marginal discrepancy distance minimization and feature reconstruction constraint is learned, such that the hashing code is not only domain adaptive but content preserved; and 3) a DA preconceived quantization loss is proposed, which further guarantees the discrimination of the learned hashing code for sample retrieval. Extensive experiments on various benchmark data sets verify that our DAPH outperforms many state-of-the-art hashing methods toward unconstrained (unrestricted) instance retrieval in both single- and cross-domain scenarios.

Optical coherence tomography systems for evaluation of marginal and internal fit of ceramic reconstructions

Purpose To evaluate the marginal and internal fit of lithium disilicate and zirconia crowns using two optical coherence tomography (OCT) systems in order to estimate inter-system variations. Materials and methods Ten lithium disilicate and 10 cubic stabilized zirconia crowns were placed on prepared artificial teeth without cement. Marginal discrepancy and internal cement gap of the crowns were assessed on images obtained using a swept source OCT (SS-OCT) and a spectral domain OCT (SD-OCT). Medians and interquartile ranges were calculated for both materials and OCT systems. Thereafter, Wilcoxon signed rank test was carried out. Results No significant difference was found between the two OCT systems for absolute marginal discrepancy of either lithium disilicate (SS-OCT: 182 µm, SD-OCT: 214 µm; p = .922) or zirconia crowns (SS-OCT: 116 µm, SD-OCT: 121 µm; p = .232). Regarding internal cement gap, no significant difference was found between the two OCT systems for lithium disilicate crowns (SS-OCT: 128 µm, SD-OCT: 128 µm; p = .064). However, for zirconia crowns the SD-OCT showed significantly higher (p = .027) internal cement gap (92 µm) than the SS-OCT (68 µm). Moreover, it was not possible to assess the internal fit of zirconia crowns in 47% and 34% of the sites using SD-OCT and SS-OCT, respectively. Conclusions No significant difference was noted in the ability of SS-OCT and SD-OCT to assess the marginal and internal fit of lithium disilicate crowns, nor the marginal fit of zirconia crowns. On the contrary, drawbacks regarding the assessment of internal fit of zirconia crowns using both OCT systems were observed.

Marginal and Internal Gap of Metal Copings Fabricated Using Three Types of Resin Patterns with Subtractive and Additive Technology: An In Vitro Comparison.

This study analyzes the evidence of the marginal discrepancy and internal adaptation of copings fabricated using three types of resin patterns with subtractive (milling) and additive technology (3D printing), as it is not widely reported. Working casts (n = 15) were scanned and patterns were completed using computer-aided designing (CAD). Resin patterns were fabricated using the designed data and divided into three groups according to the method of fabrication of patterns: subtractive technology–CAD milled polymethyl methacrylate resin (Group-PMMA), additive technology [digital light processing (DLP) technique]–acrylonitrile–butadiene–styrene (ABS) patterns (Group-ABS), and polylactic acid (PLA) patterns (Group-PLA). Resin patterns were casted with Cobalt–Chromium (Co–Cr) alloy (lost wax technique). Internal and marginal gaps of the metal copings were analyzed with the replica technique under optical microscope. The Kruskal–Wallis test was used to compare values among the groups, and post hoc multiple tests confirmed the specific differences within the groups. The median marginal gap was least for CAD milled resin patterns, followed by PLA printed resin patterns and ABS printed resin patterns. There were significant differences between Group-PMMA and Group-PLA and Group-ABS (p = 0.0001). There was no significant difference between Group-PLA and Group-ABS (p = 0.899). The median internal gap was least for metal copings fabricated from Group-PLA, followed by Group-ABS and Group-PMMA. The differences were not statistically significant (p = 0.638) for the internal gap. Full metal Co–Cr copings fabricated from the milled PMMA group had a better marginal fit, followed by the PLA and ABS printed groups. Copings fabricated with the PLA printed group had the best internal fit, though the values were statistically insignificant between the groups.

Alignment between biology curriculum standards and five textbook editions: a content analysis

ABSTRACT This study investigates the alignment between curriculum standards and textbooks, based on a standards-based science education context. The analysis sample includes the High School Biology Curriculum Standards and five editions of biology textbooks in China. Porter's alignment model is used to construct a two-dimensional (content areas and cognitive levels) matrix of curriculum standards and textbooks to calculate alignment indices and marginal discrepancies between the two dimensions. The results show that 1) alignment between curriculum standards and textbooks has not been achieved; 2) textbooks are highly consistent and statistically significant, but independent of curriculum standards; 3) the distribution of curriculum standards and textbooks across various core concepts and cognitive levels is unbalanced; 4) both curriculum standards and textbooks overemphasise the cognitive levels of remembering and understanding, while minimally representing the applying, analysing, evaluating, and creating levels. This study examines the development of curriculum alignment in the context of current worldwide standards-based science education reforms and provides a framework for alignment research based on content analysis.

Eighteen-month clinical evaluation of a new universal adhesive applied in the "no-waiting" technique: a randomized clinical trial.

ObjectiveThe aim of this double-blind, randomized clinical trial was to evaluate the 6- and 18-month clinical performances of a new universal adhesive applied in the “no-waiting” (NW) technique to non-carious cervical lesions (NCCLs) using two evaluation criteria.Materials and methodsOne hundred and seventy-six restorations were assigned to four groups according to the adhesive system, adhesive strategy, and application mode: Prime&Bond Active (PB) applied using the etch-and-rinse (ER) and self-etch (SE) strategies with 20 s applications and Clearfil Universal Bond Quick (CQ) applied using the ER and SE strategies with the NW technique. The composite resin restorations were evaluated at baseline and after 6 and 18 months using the World Dental Federation (FDI) and US Public Health Service (USPHS) criteria. The Friedman repeated measures analysis of variance and Wilcoxon test were used for statistical analyses (α = 0.05).ResultsNo significant differences were observed among any of the groups or criteria after 6 months (p > 0.05). After 18 months, 10 restorations were lost (p > 0.05) (2 with PB-ER [95.5%; 95%CI: 92–100%], 4 with PB-SE [90.9%; 95%CI: 82–98%], 0 with CQ-ER [100%; 95%CI: 92–100%], and 4 with CQ-SE [90.9%; 82–98%]). The restorations performed with the SE strategy showed more marginal discrepancies than those performed with the ER strategy, mainly when the FDI criteria were used (p < 0.05). Those that used the PB-SE showed fewer marginal discrepancies than those that used the CQ-SE (FDI; p < 0.05). A few restorations showed marginal discrepancies after the USPHS analysis (p > 0.05).ConclusionsThe results when using the CQ-SE and -ER strategies with the NW technique were similar to those when using the PB-SE and -ER strategies in standard applications to non-carious cervical lesions after 6 and 18 months of clinical evaluation.Clinical relevanceAfter 6 and 18 months, the application of Clearfil Universal Bond Quick with the “no-waiting” technique showed similar clinical performance compared to the standard application of Prime & Bond Active applied using the standard application time (20 s).Trial registrationClinicalTrials.gov identifier RBR-5f9gps.

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.

MicroCT evaluation for CAD/CAM occlusal veneer fit using two materials and three cement space settings.

This study was aimed to evaluate the fit of occlusal veneer restoration for two CAD/CAM materials with different cement space settings, using microCT scans. Sixty resin dies were made and divided into two groups (n=30) according to the materials, (I): Hybrid all-ceramic, and (II): zirconia-reinforced lithium silicate glass-ceramic. Each group was subdivided into three subgroups (n=10) according to the cement space parameters (30, 40, and 50 µm). Occlusal veneers for the six subgroups were milled. A circle with 20 different sections was placed at the center of every scanned specimen to measure four different locations (Occlusal, Axial, Marginal, and Absolute marginal discrepancy). Data were analyzed using two-way ANOVA at a 0.05 level of significance. There was no statistically significant effect of material type on the mean values of internal and marginal gaps for the three cement space parameters (P>0.05). There were no statistically significant differences in the occlusal and axial gap between the cement space parameters, furthermore, there were statistically significant differences in marginal gap distances and absolute marginal discrepancies (P>0.05). Hybrid all-ceramic showed smaller marginal and internal discrepancies than zirconia-reinforced lithium silicate glass-ceramic without statistically significant differences, and, for both materials, 50 µm cement space significantly improved the marginal fit and absolute marginal discrepancy.

Comparison of the Marginal and Internal Discrepancy of Metal-Ceramic Restorations Produced by Milling for Soft Metal, Direct Metal Laser Sintering and Casting Methods: An In Vitro Study

Aim: To evaluate the effect of ceramic firing cycles on the internal and marginal discrepancy of restorations fabricated using conventional lost wax casting (LW), direct metal laser sintering (DMLS), and milling for soft metal (MS). Materials and Methods: A total of 45 restorations were produced by LW, DMLS, and MS methods ( n = 15), according to the digital impression on the metal die representing the prepared first molar. The internal discrepancy (ID) was measured through the silicon weight method and the marginal discrepancy (MD) was measured using a light microscope. ID and MD measurements were repeated following the metal manufacturing, ceramic application, and glazing. Statistical analyses were conducted by means of two-way analysis of variance and Tukey-HSD ( α = 0.05) tests. Results: Statistically significant differences were found between the fabrication methods ( P ≤ 0.001) both for MD and ID. The mean MD values of the restorations were 31.4 ± 13.8 µm for MS, 20.8 ± 14.4 µm for LW, and 7.3 ± 6 µm for DMLS. A statistically significant increase was observed in the mean MD values of metal frameworks ( P ≤ 0.001) following ceramic and glaze applications. However, no statistically significant difference was found between the ceramic and the glaze applied stages ( P = .072). The mean ID values were 37 ± 5.7 mg for LW, 28 ± 6.1 mg for DMLS, and 21.6 ± 7.3 mg for MS. Unlike the manufacturing method, ceramic firing cycles had no effects on the ID ( P &gt; 0.05). Conclusion: MS had the highest mean MD, but it had the lowest ID. The ceramic firing had a significantly negative effect only on MD.

Search for a distance-dependent Baryonic Tully-Fisher Relation at low redshifts

A recent work (arXiv:2104.14481) has found a statistically significant transition in the Baryonic Tully-Fisher relation (BTFR) using low redshift data ($z<0.1$), with the transitions occurring at about 9 and 17 Mpc. Motivated by this finding, we carry out a variant of this analysis by fitting the data to an augmented BTFR, where both the exponent as well as normalization constant vary as a function of distance. We find that both the exponent and normalization constant show only a marginal variation with distance, and are consistent with a constant value, to within $2\sigma$. We also checked to see if there is a statistically significant difference between the BTFR results after bifurcating the dataset at distances of 9 and 17 Mpc. We find that almost all the sets of subsamples obey the BTFR with $\chi^2$/dof close to 1 and the best-fit parameters consistent across the subsamples. Only the subsample with $D<17$ Mpc shows a marginal discrepancy (at $1.75\sigma$) with respect to the BTFR. Therefore, we do not find any evidence for statistically significant differences in the BTFR at distances of 9 and 17 Mpc.

The Effect of Various Cementing Agents on Occlusal Discrepancy Using an Intra-Oral Scanner: An In Vivo Study

A marginal fit of all-ceramic crowns is a prerequisite for the long-term clinical success of a dental restoration. Few in vivo studies have investigated the effect of the film thickness of various luting agents on vertical discrepancy. This in vivo study evaluated the influence of three luting cements on the occlusal vertical discrepancy of milled crowns using a complete digital workflow. Forty-three patients treated in a students’ clinic in Tel-Aviv University with 45 single posterior digitally prepared monolithic crowns were included in the study. The crowns were randomly divided into three groups using different resin luting agents: self-adhesive resin cement, resin-modified glass ionomer cement and adhesive resin cement. The crowns were intra-orally scanned before and after cementation. The two standard tessellation language (STL) files for each crown were superimposed using digital software, and between four and six measurements were made at the occlusal surface to demonstrate the occlusal and marginal discrepancies. One-way ANOVA (α = 0.05) was used. The vertical occlusal discrepancy ranged from 2 to 38 μm. The mean vertical discrepancy values were (µm): self-adhesive resin = 12.93 ± 4.74, resin-modified glass ionomer = 19.05 ± 4.60 and adhesive resin = 13.69 ± 5.17. There were significant differences between resin-modified and self-adhesive cement groups (p = 0.004), and between resin-modified and adhesive resin cement groups (p = 0.013). Distal marginal ridge measurements were significantly different between resin-modified glass ionomer cement and self-adhesive resin cement group (p &lt; 0.001) and the adhesive resin cement group (p = 0.021). There were no significant differences between the discrepancy values at the two measurement points in the self-adhesive cement group (p = 0.377), nor the resin-modified glass ionomer group (p = 0.388), or the adhesive resin cement group (p = 0.905). The cementation procedure with various resin cements results in occlusal vertical discrepancies within standard clinical acceptability. Resin-modified glass ionomer cement produced more vertical discrepancy than adhesive and self-adhesive resin cements did.

Assessment of the readiness of restorations manufactured by CAD/CAM in terms of marginal fit (Part I).

BackgroundThe master cast is the gold standard for the control and eventual adjustment of restorations produced by conventional procedures. Some digital workflow bypasses the master cast and relies completely on the precision of the CAD/CAM restoration.AimTo examine the reproducibility of the margins of CAD/CAM restorations generated from a single digital scan. Also, to check the readiness of these restorations for delivery directly after fabrication without adjustment on a master cast and thereby eliminate the need for the master cast.MethodsA total of 18 metal substructures made from cobalt chrome alloy were fabricated utilizing a single STL file. The circumference was divided into eight zones. The vertical marginal discrepancy (VMD) was measured at each zone of each metal substructure, with optical microscopy at ×200 magnification.ResultsMeasurements of vertical marginal discrepancy were in a range of (−94: 300) with a mean of 62 ± 60 μm. A one-way ANOVA test revealed that the mean VMD is significantly different among the 18 substructures (F17, 1,134 = 63.948, p < 0.001).ConclusionAlthough all the received substructures were fabricated from the same scan file, they were not identical and varied widely, and they were going outside the acceptable range in some zones. Within the limitations of this study, the marginal fit can be improved by extraoral adjustments on the master cast. Thus, skipping the master cast deprives the dentist of delivering a restoration of higher quality.

Universal Simplified Adhesive applied under different bonding technique's: 36-month Randomized Multicentre Clinical Trial

To evaluate the clinical performance of a new dual-cure universal adhesive system (Futurabond U, Voco) when applied using different application strategies in non-carious cervical lesions (NCCLs) after 36 months. Futurabond U was applied in NCCLs of 50 subjects using four adhesion strategies (n=50 restorations per group): only self-etch (SEE); selective enamel etching+self-etch (SET); etch-and-rinse with dry dentin (ERDry); and etch-and-rinse with wet dentin (ERWet). All cavities were restored using Admira Fusion composite resin (Voco). Restorations were evaluated after 36 months using the World Federation criteria (FDI) and the modified United States Public Health Service (USPHS) criteria. The after 36-month retention rates were 87% (75-92%) for SEE, 94% (83-98%) for SET, 91% (80-97%) for ERDry, and 94% (83-98%) for ERWet. Forty-three restorations were considered to have minor discrepancies in marginal adaptation at the 36-month recall (18 for SEE, 12 for SET, 7 for ERDry, and 6 for ERWet; p > 0.05). One restoration was detected as a minor marginal discoloration at the 36-month recall (1 for SET; p > 0.05). No restorations showed postoperative sensitivity and caries recurrence at 36 months. The clinical performance of the Futurabond U did not depend on the employed bonding strategy, and it was considered reliable after 36 months of clinical evaluation. However, greater marginal discrepancy was observed in the self-etch groups. NCCLs restorations using a dual-cure universal adhesive in self-etch and etch-and-rinse modes showed satisfactory clinical performance after 36 months.

Accuracy of Fixed Implant-Supported Dental Prostheses Additively Manufactured by Metal, Ceramic, or Polymer: A Systematic Review.

Additive manufacturing (AM) in prosthodontics is used as an alternative to casting or milling. Various techniques and materials are available for the additive manufacturing of the fixed and removable tooth-supported restorations, but there is a lack of evidence on the accuracy of AM fixed implant-supported prostheses. Recent studies investigated the accuracy of ceramic AM prostheses. Therefore, the aim of this systematic review was to evaluate the accuracy of additively manufactured metal, ceramic or polymers, and screw- or cement-retained fixed implant-supported prostheses. Two calibrated investigators performed an electronic search of relevant publications in the English language following selected PICOS criteria and using a well-defined search strategy (latest search date-1st of June, 2021). Based on the exclusion criteria (no control group, less than five samples per group, 3D printing of the implant abutment part, only subjective evaluation of accuracy, etc.) studies were not included in the review. Quantitative data of accuracy evaluation such as marginal gap, strain analysis, and linear measurements was extracted and interpreted. QUADAS-2 tool was used to assess the risk of methodological bias of all included studies. Sixteen in vitro studies were selected for the final analysis. Six of the selected studies evaluated screw-retained restorations and 10 cement-retained implant-supported restorations. Only 4 publications concluded that AM restorations were more accurate than conventionally made (cast or milled) ones. The most common finding was that AM restorations were more accurate than cast and demonstrated less or similar accuracy compared to milled ones (n = 10 studies). Detected marginal discrepancies mean values of the AM prosthesis varied from 23 to more than 200 µm, but most of them were categorized as clinically acceptable. AM implant-supported fixed prostheses demonstrate similar accuracy compared to conventional and computer-aided design and computer-aided manufacturing techniques in vitro. Detected inaccuracies of AM restorations do not exceed clinically acceptable limits. Clinical studies with longer follow-up periods are needed to show the reliability of AM prostheses.