A single sulfatase is required to access colonic mucin by a gut bacterium.

Humans have co-evolved with a dense community of microbial symbionts that inhabit the lower intestine. In the colon, secreted mucus creates a barrier that separates these microorganisms from the intestinal epithelium1. Some gut bacteria are able to utilize mucin glycoproteins, the main mucus component, as a nutrient source. However, it remains unclear which bacterial enzymes initiate degradation of the complex O-glycans found in mucins. In the distal colon, these glycans are heavily sulfated, but specific sulfatases that are active on colonic mucins have not been identified. Here we show that sulfatases are essential to the utilization of distal colonic mucin O-glycans by the human gut symbiont Bacteroides thetaiotaomicron. We characterized the activity of 12 different sulfatases produced by this species, showing that they are collectively active on all known sulfate linkages in O-glycans. Crystal structures of three enzymes provide mechanistic insight into the molecular basis of substrate specificity. Unexpectedly, we found that a single sulfatase is essential for utilization of sulfated O-glycans in vitro and also has a major role in vivo. Our results provide insight into the mechanisms of mucin degradation by a prominent group of gut bacteria, an important process for both normal microbial gut colonization2 and diseases such as inflammatory bowel disease3.

Diet-driven differential response of Akkermansia muciniphila modulates pathogen susceptibility.

The erosion of the colonic mucus layer by a dietary fiber-deprived gut microbiota results in heightened susceptibility to an attaching and effacing pathogen, Citrobacter rodentium. Nevertheless, the questions of whether and how specific mucolytic bacteria aid in the increased pathogen susceptibility remain unexplored. Here, we leverage a functionally characterized, 14-member synthetic human microbiota in gnotobiotic mice to deduce which bacteria and functions are responsible for the pathogen susceptibility. Using strain dropouts of mucolytic bacteria from the community, we show that Akkermansia muciniphila renders the host more vulnerable to the mucosal pathogen during fiber deprivation. However, the presence of A. muciniphila reduces pathogen load on a fiber-sufficient diet, highlighting the context-dependent beneficial effects of this mucin specialist. The enhanced pathogen susceptibility is not owing to altered host immune or pathogen responses, but is driven by a combination of increased mucus penetrability and altered activities of A. muciniphila and other community members. Our study provides novel insights into the mechanisms of how discrete functional responses of the same mucolytic bacterium either resist or enhance enteric pathogen susceptibility.

In silico analysis of alpha-synuclein protein variants and posttranslational modifications related to Parkinson's disease.

Parkinson's disease (PD) is among the most prevalent neurodegenerative disorders, affecting over 10 million people worldwide. The protein encoded by the SNCA gene, alpha-synuclein (ASYN), is the major component of Lewy body (LB) aggregates, a histopathological hallmark of PD. Mutations and posttranslational modifications (PTMs) in ASYN are known to influence protein aggregation and LB formation, possibly playing a crucial role in PD pathogenesis. In this work, we applied computational methods to characterize the effects of missense mutations and PTMs on the structure and function of ASYN. Missense mutations in ASYN were compiled from the literature/databases and underwent a comprehensive predictive analysis. Phosphorylation and SUMOylation sites of ASYN were retrieved from databases and predicted by algorithms. ConSurf was used to estimate the evolutionary conservation of ASYN amino acids. Molecular dynamics (MD) simulations of ASYN wild-type and variants A30G, A30P, A53T, and G51D were performed using the GROMACS package. Seventy-seven missense mutations in ASYN were compiled. Although most mutations were not predicted to affect ASYN stability, aggregation propensity, amyloid formation, and chaperone binding, the analyzed mutations received relatively high rates of deleterious predictions and predominantly occurred at evolutionarily conserved sites within the protein. Moreover, our predictive analyses suggested that the following mutations may be possibly harmful to ASYN and, consequently, potential targets for future investigation: K6N, T22I, K34E, G36R, G36S, V37F, L38P, G41D, and K102E. The MD analyses pointed to remarkable flexibility and essential dynamics alterations at nearly all domains of the studied variants, which could lead to impaired contact between NAC and the C-terminal domain triggering protein aggregation. These alterations may have functional implications for ASYN and provide important insight into the molecular mechanism of PD, supporting the design of future biomedical research and improvements in existing therapies for the disease.

Four-week experimental plus 1-week taper period using live high train low does not alter muscle glycogen content.

This study aimed to investigate the effects of a 4-week live high train low (LHTL; FiO2 ~ 13.5%), intervention, followed by a tapering phase, on muscle glycogen concentration. Fourteen physically active males (28 ± 6 years, 81.6 ± 15.4 kg, 179 ± 5.2 cm) were divided into a control group (CON; n = 5), and the group that performed the LHTL, which was exposed to hypoxia (LHTL; n = 9). The subjects trained using a one-legged knee extension exercise, which enabled four experimental conditions: leg training in hypoxia (TLHYP); leg control in hypoxia (CLHYP, n = 9); leg trained in normoxia (TLNOR, n = 5), and leg control in normoxia (CLNOR, n = 5). All participants performed 18 training sessions lasting between 20 and 45 min [80-200% of intensity corresponding to the time to exhaustion (TTE) reached in the graded exercise test]. Additionally, participants spent approximately 10 h day-1 in either a normobaric hypoxic environment (14.5% FiO2; ~ 3000 m) or a control condition (i.e., staying in similar tents on ~ 530 m). Thereafter, participants underwent a taper protocol consisting of six additional training sessions with a reduced training load. SpO2 was lower, and the hypoxic dose was higher in LHTL compared to CON (p < 0.001). After 4 weeks, glycogen had increased significantly only in the TLNOR and TLHYP groups and remained elevated after the taper (p < 0.016). Time to exhaustion in the LHTL increased after both the 4-week training period and the taper compared to the baseline (p < 0.001). Although the 4-week training promoted substantial increases in muscle glycogen content, TTE increased in LHTL condition.

Reliability of Anaerobic Contributions during a Single Exhaustive Knee-extensor Exercise.

The total anaerobic contribution (AC[La-]+PCr) is a valid and reliable methodology. However, the active muscle mass plays an important role in the AC[La-]+PCr determination, which might influence its reliability. Thus, this study aimed to investigate the effects of two exhaustive intensities on the reliability of the AC[La-]+PCr during a one-legged knee extension (1L-KE) exercise. Thirteen physically active males were submitted to a graded exercise to determine the peak power output (PPO) in the 1L-KE. Then, two constant-load exercises were conducted to task failure at 100% (TTF100) and 110% (TTF110) of PPO, and the exercises were repeated on a third day. The blood lactate accumulation and the oxygen uptake after exercise were used to estimate the anaerobic lactic and alactic contributions, respectively. Higher values of AC[La-]+PCr were found after the TTF100 compared to TTF110 (p=0.042). In addition, no significant differences (p=0.432), low systematic error (80.9 mL), and a significant ICC (0.71; p=0.004) were found for AC[La-]+PCr in the TTF100. However, an elevated coefficient of variation was found (13.7%). In conclusion, we suggest the use of the exhaustive efforts performed at 100% of the PPO with the 1L-KE model, but its elevated individual variability must be carefully considered in future studies.

Repair of monolithic zirconia restorations with different direct resin composites: effect on the fatigue bonding and mechanical performance.

OBJECTIVE: The study aims to evaluate the shear bond and flexural strength fatigue behavior of yttrium-stabilized zirconia (4YSZ) repaired using different resin composites. MATERIALS AND METHODS: Cylindric specimens of 4YSZ were obtained for the bond strength (Ø = 6 mm, 1.5 mm of thickness) and biaxial flexural strength (Ø = 15 mm, 1 mm of thickness) fatigue tests and divided into 3 groups according to the repair resin composite: EVO (nanohybrid), BULK (bulk-fill), and FLOW (flowable). The zirconia surface was air-abraded with alumina particles, a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) primer was applied, and the resin composite was build-up over the zirconia. Fatigue shear bond strength and flexural fatigue strength tests were performed (n = 15). One-way ANOVA and Tukey post hoc tests were carried out for both outcomes, besides scanning electron microscopy and finite element analysis. RESULTS: The repair material affected the fatigue shear bond strength of zirconia ceramic. The BULK group (18.9 MPa) depicted higher bond strength values than FLOW (14.8 MPa) (p = 0.04), while EVO (18.0 MPa) showed similar results to both groups. No effect was observed for the mechanical behavior (p = 0.53). The stress distribution was similar for all groups. CONCLUSION: The repair of yttrium-stabilized zirconia (4YSZ) ceramics with bulk-fill resin composites was the best option for high fatigue bond strength. However, the fatigue mechanical performance was similar regardless of the applied repair material. CLINICAL RELEVANCE: The repair of yttrium-stabilized zirconia (4YSZ) monolithic restorations may be performed with nanohybrid and bulk-fill resin composites in order to promote longevity in the treatment.

Trends in tracheal, bronchial and lung cancer attributed to smoking in South America: Global Burden of Disease analysis 1990-2019.

Objective: To investigate the burden of tracheal, bronchus, and lung (TBL) cancer due to tobacco exposure in the last 30 years in 12 South American countries. Methods: We used the Global Burden of Disease (GBD) 2019 exposure-response function to analyze the total tobacco, smoking, and secondhand smoke exposure-related TBL cancer deaths and disability-adjusted life years (DALYs), for 12 South American countries, between 1990 and 2019. Metrics were described as absolute numbers or rates per 100 000 individuals. The relative change in burden was assessed by comparing the 1990-1994 to 2015-2019 periods. Results: In 2019, the all-ages number of TBL cancer deaths and DALYs associated with tobacco exposure in South America was 29 348 and 658 204 in males and 14 106 and 318 277 in females, respectively. Age-adjusted death and DALYs rates for the region in 2019 were 182.8 and 4035 in males and 50.8 and 1162 in females, respectively. In males, 10/12 countries observed relative declines in TBL death rates attributed to tobacco exposure while only 4 countries reduced their mortality in females. Conclusion: While significant efforts on tobacco control are under place in South America, substantial burden of TBL cancer persists in the region with significant sex-specific disparities. Increased country-specific primary data on TBL cancer and tobacco exposure is needed to optimize healthcare strategies and improve comprehension of regional trends.

An In Silico Analysis of Genetic Variants and Structural Modeling of the Human Frataxin Protein in Friedreich's Ataxia.

Friedreich's Ataxia (FRDA) stands out as the most prevalent form of hereditary ataxias, marked by progressive movement ataxia, loss of vibratory sensitivity, and skeletal deformities, severely affecting daily functioning. To date, the only medication available for treating FRDA is Omaveloxolone (Skyclarys®), recently approved by the FDA. Missense mutations within the human frataxin (FXN) gene, responsible for intracellular iron homeostasis regulation, are linked to FRDA development. These mutations induce FXN dysfunction, fostering mitochondrial iron accumulation and heightened oxidative stress, ultimately triggering neuronal cell death pathways. This study amalgamated 226 FXN genetic variants from the literature and database searches, with only 18 previously characterized. Predictive analyses revealed a notable prevalence of detrimental and destabilizing predictions for FXN mutations, predominantly impacting conserved residues crucial for protein function. Additionally, an accurate, comprehensive three-dimensional model of human FXN was constructed, serving as the basis for generating genetic variants I154F and W155R. These variants, selected for their severe clinical implications, underwent molecular dynamics (MD) simulations, unveiling flexibility and essential dynamic alterations in their N-terminal segments, encompassing FXN42, FXN56, and FXN78 domains pivotal for protein maturation. Thus, our findings indicate potential interaction profile disturbances in the FXN42, FXN56, and FXN78 domains induced by I154F and W155R mutations, aligning with the existing literature.

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.

In-Stent Restenosis Overview: From Intravascular Imaging to Optimal Percutaneous Coronary Intervention Management.

Despite ongoing progress in stent technology and deployment techniques, in-stent restenosis (ISR) still remains a major issue following percutaneous coronary intervention (PCI) and accounts for 10.6% of all interventions in the United States. With the continuous rise in ISR risk factors such as obesity and diabetes, along with an increase in the treatment of complex lesions with high-risk percutaneous coronary intervention (CHIP), a substantial growth in ISR burden is expected. This review aims to provide insight into the mechanisms, classification, and management of ISR, with a focus on exploring innovative approaches to tackle this complication comprehensively, along with a special section addressing the approach to complex calcified lesions.

Multiple TonB homologs are important for carbohydrate utilization by Bacteroides thetaiotaomicron.

IMPORTANCE: The human gut microbiota, including Bacteroides, is required for the degradation of otherwise undigestible polysaccharides. The gut microbiota uses polysaccharides as an energy source, and fermentation products such as short-chain fatty acids are beneficial to the human host. This use of polysaccharides is dependent on the proper pairing of a TonB protein with polysaccharide-specific TonB-dependent transporters; however, the formation of these protein complexes is poorly understood. In this study, we examine the role of 11 predicted TonB homologs in polysaccharide uptake. We show that two proteins, TonB4 and TonB6, may be functionally redundant. This may allow for the development of drugs targeting Bacteroides species containing only a TonB4 homolog with limited impact on species encoding the redundant TonB6.

STAT-3 signaling role in an experimental model of nephropathy induced by doxorubicin.

The focal segmental glomerulosclerosis (FSGS) is one of the most frequent glomerulopathy in the world, being considered a significative public health problem worldwide. The disease is characterized by glomerular loss mainly due to inflammation process and collagen fibers deposition. STAT-3 is a transcription factor associated with cell differentiation, migration and proliferation and in renal cells it has been related with fibrosis, acting on the progression of the lesion. Considering this perspective, the present study evaluated the involvement of STAT-3 molecule in an experimental model of FSGS induced by Doxorubicin (DOX). DOX mimics primary FSGS by causing both glomerular and tubular lesions and the inhibition of the STAT3 pathway leads to a decrease in fibrosis and attenuation of kidney damage. We described here a novel FSGS experimental model in a strain of genetically heterogeneous mice which resembles the reality of FSGS patients. DOX-injected mice presented elevated indices of albuminuria and glycosuria, that were significantly reduced in animals treated with a STAT-3 inhibitor (STATTIC), in addition with a decrease of some inflammatory molecules. Moreover, we detected that SOCS-3 (a regulator of STAT family) was up-regulated only in STATTIC-treated mice. Finally, histopathological analyzes showed that DOX-treated group had a significant increase in a tubulointerstitial fibrosis and tubular necrosis, which were not identified in both control and STATTIC groups. Thus, our results indicate that STAT-3 pathway possess an important role in experimental FSGS induced by DOX and may be an important molecule to be further investigated.

MILACC study: could undetected lymph node micrometastases have impacted recurrence rate in the LACC trial?

OBJECTIVE: The etiology of inferior oncologic outcomes associated with minimally invasive surgery for early-stage cervical cancer remains unknown. Manipulation of lymph nodes with previously unrecognized low-volume disease might explain this finding. We re-analyzed lymph nodes by pathologic ultrastaging in node-negative patients who recurred in the LACC (Laparoscopic Approach to Cervical Cancer) trial. METHODS: Included patients were drawn from the LACC trial database, had negative lymph nodes on routine pathologic evaluation, and recurred to the abdomen and/or pelvis. Patients without recurrence or without available lymph node tissue were excluded. Paraffin tissue blocks and slides from all lymph nodes removed by lymphadenectomy were re-analyzed per standard ultrastaging protocol aimed at the detection of micrometastases (>0.2 mm and ≤2 mm) and isolated tumor cells (clusters up to 0.2 mm or <200 cells). RESULTS: The study included 20 patients with median age of 42 (range 30-68) years. Most patients were randomized to minimally invasive surgery (90%), had squamous cell carcinoma (65%), FIGO 2009 stage 1B1 (95%), grade 2 (60%) disease, had no adjuvant treatment (75%), and had a single site of recurrence (55%), most commonly at the vaginal cuff (45%). Only one patient had pelvic sidewall recurrence in the absence of other disease sites. The median number of lymph nodes analyzed per patient was 18.5 (range 4-32) for a total of 412 lymph nodes. A total of 621 series and 1242 slides were reviewed centrally by the ultrastaging protocol. No metastatic disease of any size was found in any lymph node. CONCLUSIONS: There were no lymph node low-volume metastases among patients with initially negative lymph nodes who recurred in the LACC trial. Therefore, it is unlikely that manipulation of lymph nodes containing clinically undetected metastases is the underlying cause of the higher local recurrence risk in the minimally invasive arm of the LACC trial.

Effect of calcium hypochlorite and sodium thiosulfate on the bond strength to pulp chamber dentin: A laboratory investigation.

This study aimed to compare the effect of sodium hypochlorite (NaOCl) and calcium hypochlorite [Ca(OCl)2 ] on the bond strength to pulp chamber dentin when followed or not by the use of sodium thiosulfate (Na2 S2 O3 ). The pulp chamber of fifty human molars were divided into five groups (n = 10) according to the immersion protocol: 2.5% NaOCl; 2.5% NaOCl + 5% Na2 S2 O3 ; 2.5% Ca(OCl)2 ; 2.5% Ca(OCl)2 + 5% Na2 S2 O3 ; and 0.9% sodium chloride (NaCl; control). Subsequently, the samples were restored with resin composite. Three sticks each were obtained and subjected to microtensile testing. SEM/EDS analyses of the pulp chamber roof (n = 8) were carried out for mineral quantification. Elemental analysis data were investigated via one-way ANOVA and Tukey's post hoc, and bond strength data by post hoc pairwise comparisons using the Kruskal-Wallis test. Use of 2.5% NaOCl was associated with the lowest value of bond strength, while 2.5% Ca(OCl)2 had similar bond strength to that of the 0.9% NaCl control. Using 5% Na2 S2 O3 was able to increase the bond strength after 2.5% NaOCl, but not after 2.5% Ca(OCl)2 . The group treated only with 2.5% Ca(OCl)2 had a higher Ca/P ratio on the dentin surface. Dentin treated with Ca(OCl)2 was not affected by Na2 S2 O3 and showed bond strength similar to the 0.9% NaCl.

Longevity of metal-ceramic single crowns cemented onto resin composite prosthetic cores with self-adhesive resin cement: an update of a prospective analysis with up to 106 months of follow-up.

OBJECTIVES: To evaluate the longevity of metal-ceramic single crowns cemented onto resin composite prosthetic cores using a self-adhesive resin cement in a prospective clinical descriptive study. METHODS: A total of 152 teeth were endodontically treated and received resin composite prosthetic cores and metal-ceramic crowns cemented with a self-adhesive resin cement. The patients included in the sample were recalled for clinical and radiography evaluation in an up-to-106-month period after the final cementation procedures, with an average of 62 months of follow-up. 91.5% of the sample (142 teeth) were evaluated regarding the treatment survival rate, analyzed considering the loss of crown retention (crown debonding) and tooth loss as the primary outcome. In addition, post debonding, and root fracture occurrences were also recorded as secondary outcomes to evaluate the success rate of the prosthetic treatment. The aesthetic parameters were also evaluated according to the FDI criteria. The Kaplan-Meier method and Cox regression with 95% confidence interval were applied for the statistical analysis. RESULTS: Regarding the primary outcome, the metal-ceramic crowns cemented with self-adhesive resin cement presented a high survival rate (91.5%), with 8 crown debondings and 3 tooth losses (1 due to caries and 2 due to periodontal disease) occurring after the evaluation period. For secondary outcomes, 9 root fractures and 4 post debondings occurred, generating a success rate of 72%. All crowns had a score 1 on the FDI criteria, indicating that they were clinically excellent or very good regarding the aesthetic parameters. CONCLUSION: The metal-ceramic crowns luted with a self-adhesive resin cement presented a survival rate of 91.5% after an average of 62 months of follow-up. Furthermore, the restorations remained aesthetically satisfactory over time, without changes that would indicate prosthetic retreatment. A success rate of 72% was obtained considering the secondary outcome, mainly related to intraradicular retainer failures (root fractures or post debonding). CLINICAL SIGNIFICANCE: The self-adhesive resin cement is clinically indicated for cementation of metal-ceramic crowns onto resin composite prosthetic cores.

Survival rate and treatment success of glass fiber posts cemented with two adhesive cementation strategies after up to 106 months: a randomized clinical trial.

OBJECTIVES: The objective of this study is to evaluate the longevity of two fiber post cementation strategies in a prospective, multicenter, non-inferiority, double-blind randomized controlled trial. METHODS: A total of 152 teeth, with adequate endodontic treatment and loss of coronal structure and bilateral simultaneous posterior occlusal contacts, were randomly allocated to receive glass fiber posts cemented with a conventional cementation strategy (CRC group: adhesive system + resin cement) (Adper Single Bond + RelyX ARC; 3 M-ESPE) or a self-adhesive cementation strategy (SRC group: self-adhesive resin cement; RelyX U100/U200; 3 M-ESPE). The patients were recalled annually for clinical and radiographical evaluation with a 93% recall rate (142 teeth, with 74 at CR groups and 68 at SRC group). The primary outcome was survival rate, considering the fiber post debonding (loss of retention). The secondary outcome included the success rate of the prosthetic treatment with crown debonding, post fracture, and tooth loss (not related to post failure). Both outcomes were evaluated annually. The Kaplan-Meier method and Cox regression with 95% confidence interval were used for the statistical analysis. RESULTS: For the primary outcome (failures directly related to fiber posts cementation strategy), there were 4 fiber post debondings (2 per group), 8 root fractures (3 for SRC group and 5 for CRC group), and one mixed failure (debonding combined with root fracture for CRC), with both strategies presenting similar survival rates (p = 0.331), with 88.9% for the CRC group and 90.9% for the SRC group. For the secondary outcome (failures not related to fiber post cementation strategies), there were 8 crown debondings, 3 post fractures, and 3 tooth losses, with no statistically difference between groups (p = 0.701), with 77% for SRC and 82% for CRC. CONCLUSION: Fiber post cementation strategies with conventional or self-adhesive resin cement presents similar tooth survival and success rates. TRIAL REGISTRATION: NCT01461239 CLINICAL RELEVANCE: Both adhesive cementation strategies led to high survival and success rates and are indicated for fiber post cementation, even after a long follow-up period (up to 106 months).

Fatigue behavior, failure mode, and stress distribution of occlusal veneers: influence of the prosthetic preparation cusp inclinations and the type of restorative material.

OBJECTIVE: To evaluate the effects of cusp inclination of the prosthetic preparation's occlusal surface and type of restorative material on the fatigue behavior, failure mode, and stress distribution of occlusal veneers. MATERIALS AND METHODS: Glass fiber-reinforced epoxy resin prosthetic preparations for occlusal veneers with three different occlusal surface cusp inclination degrees (0°, 15°, and 30°) were produced and assigned into six testing groups (n = 11) according to the cusp inclination (0°, 15°, or 30°) and type of restorative material (lithium disilicate-LD or resin composite-RC). Despite different substrate preparation cusp inclination degrees, the restorations were designed maintaining 30° inclination between the cusps at the occlusal surface and a thickness of 0.7 mm at the central groove region of the restorations to be machined in a CAD/CAM system. After cementation, the specimens were stored for about 7 days (under water at 37 °C), and subsequently submitted to a load to failure test (n = 2) and an intermittent cyclic fatigue test (n = 9) (initial load: 100 N; step size: 50 N; cycles/step: 10,000; loading frequency: 20 Hz; loading piston: 6-mm-diameter stainless steel) until observing cracks. The data were analyzed by two-way ANOVA, Kaplan-Meier, and Mantel-Cox post hoc tests. Finite element analysis (FEA) and fractographic analyses were performed. RESULTS: The fatigue performance of LD and RC occlusal veneers was evaluated based on different prosthetic preparation cusp inclinations. The 0° inclination showed the best fatigue performance for both materials (LD: 944N, RC: 861N), while the 15° and 30° inclinations had lower values (LD: 800N and 533N, RC: 739N and 717N, respectively). The study also found that for a 0° inclination, LD occlusal veneers performed better than RC ones (LD: 944 N > RC: 861N), while for a 30° inclination, RC occlusal veneers had better fatigue performance than LD ones (LD: 533N < RC: 717N). No significant difference was observed between the materials for a 15° inclination (LD: 800N = RC: 739N). The FEA results showed a higher tensile stress concentration on lithium disilicate than on resin composite occlusal veneers. All lithium disilicate occlusal veneers showed radial crack failures, while resin composite occlusal veneers showed Hertzian cone cracks and radial cracks combined. CONCLUSION: Considering mechanical perspective only, RC occlusal veneers should be indicated when prosthetic preparation cusps inclinations are 30°. When 0° prosthetic preparation cusps inclinations are observed, LD occlusal veneers will behave mechanically better. When a 15° cusp inclination is preserved, both restorative materials behave similarly.

Resin composite layering on discolored substrates ensures masking ability for monolithic ceramics.

OBJECTIVE: the aim of this study was to evaluate the effect of resin composite layering on discolored substrates to obtain masking ability with monolithic ceramics. MATERIALS AND METHODS: Four groups (n = 8) of computer-aided design/computer aided manufacturing (CAD/CAM) monolithic ceramics, shade A1, with thicknesses of 1.0 and 1.5 mm, were tested: feldspathic (FC), leucite-reinforced (LC), lithium disilicate-reinforced (LD), and translucent zirconia (5YSZ). Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as non-layered or layered (with flowable opaque resin composite (FL), white opaque restorative resin composite (WD), and A1-shaded opaque restorative resin composite (A1D)). Resin composite layers of 0.5 and 1.0 mm were tested. The try-in paste, shade A1, was used as a luting agent. Translucency parameter (TP00 ) was assessed for the ceramics. Color differences (∆E00 ) were assessed for the restorative ceramics and resin composite layers over discolored substrates with the CIEDE2000 formula. The results were compared statistically, and descriptively with acceptability (AT, 1.77) and perceptibility (PT, 0.81) thresholds. RESULTS: Feldspathic showed the highest TP00 (for both ceramic thicknesses) and LD the lowest (for 1.5 mm of ceramic thickness) (P < 0.001). For substrate A3.5, layering with 1.0 mm of A1D or WD ensured ∆E00 below PT for all ceramics tested (P < 0.001). The use of 0.5 mm of FL or 1.0 mm of A1D associated with ceramics LC, LD, and 5YSZ ensured ∆E00 below AT for substrates C4 and coppery metal (P < 0.001). Silvery background layered with 0.5 mm of FL presented ∆E00 below AT for all ceramics and ∆E00 below PT for lithium disilicate of 1.0 mm of thickness (∆E00 = 0.72). CONCLUSIONS: Layering severely discolored substrates with selected opaque resin composites ensures masking ability for restoration with CAD/CAM monolithic ceramics. CLINICAL SIGNIFICANCE: Severely discolored substrates are predictably restored with monolithic CAD/CAM ceramics by performing a previous layering of the substrate with opaque resin composite.

Masking ability of resin composites: A scoping review.

OBJECTIVE: To map the existing evidence regarding the masking ability of resin composites. OVERVIEW: The literature search was conducted electronically, based on the PRISMA Extension for Scoping Reviews-online protocol at https://osf.io/m2h67/ with no language or time restrictions. Two independent reviewers conducted the screening, and a third reviewer was consulted in case of disagreement. Studies that evaluated resin composite masking ability regardless of background, application technique, thickness, or number of layers were selected. The search found 2995 potentially eligible studies. After removal of duplicates (657), irrelevant articles (2323), 15 citations met the eligibility criteria based on title and abstract, and eight studies were included based on full text analysis (seven in vitro, and one case report). Acceptable masking ability is obtained by one layer of opaque shade resin composite or by the layering technique. A black background is masked with 1.0- to 2.0 mm-thick layers of opaque shade resin composites. Masking of the C4 background is achieved with one layer of 0.5- to 1.5 mm-thick opaque shade resin composite or by the layering technique using different combinations of enamel body and dentin shades with a final thickness of 1.5 mm. CONCLUSIONS: Acceptable masking of C4 shade background is achieved with one layer of opaque shade composite at least 0.5 mm-thick or by different combinations of the layering technique, with a final thickness of 1.5 mm. Acceptable masking of the black background of the oral cavity is achieved with a resin composite of at least 1.0 mm opaque shade. CLINICAL SIGNIFICANCE: The thickness of the resin composite layer required to achieve adequate masking is variable and depends on the translucency/opacity of the tested resin composites and the background shade.

Evaluation paste removal method and bond strength between resin cement and lithium disilicate ceramic: An in vitro study.

STATEMENT OF PROBLEM: After the use of evaluation paste, residue can remain on the bonding surface. However, how adhesion to lithium disilicate ceramic is affected is unclear. PURPOSE: The purpose of this in vitro study was to determine the effectiveness of lithium disilicate cleaning after contamination with an evaluation paste and before the application of a resin cement. MATERIAL AND METHODS: Rectangular lithium disilicate (IPS e.max CAD) specimens were obtained with a simulated milled surface, crystallized, etched with 5% hydrofluoric (HF) acid, and contaminated with an evaluation paste. The cleaning methods tested were air-water spray (SPRAY), 37% phosphoric acid (HPO), ultrasonic bath (ULT), cleaning paste (IVOC), and a conventional surface treatment (HF + silane-HF+SIL). The control (CTRL) group was not contaminated. After silane had been applied, resin cement cylinders were fabricated and light polymerized. Half of the cylinders (n=56) were tested for microshear bond strength at baseline (24 hours), and the other half after 210 days of water storage and 25 000 thermal cycles. Surface roughness, failure analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were performed. Statistical analysis was performed with the Kruskal-Wallis and Mann-Whitney tests for surface roughness and the 2-way ANOVA and Bonferroni post hoc tests for bond strength (α=.05). RESULTS: At baseline, only SPRAY did not restore the bond strength compared with CTRL. After aging, the bond strengths of SPRAY and IVOC were lower than of CTRL (P<.05); no significant difference was found between CTRL, HPO, ULT, and HF+SIL (P>.05). EDS demonstrated the presence of carbon in the SPRAY and ULT groups, probably remnants of the evaluation paste. SEM analysis identified such remnants in the SPRAY group only. CONCLUSIONS: For optimal bond strength between lithium disilicate and resin cement after evaluation paste use, cleaning the ceramic surface with 37% phosphoric acid, ultrasonic bath, or with hydrofluoric acid worked best.