3D printed, subtractive, and conventional acrylic resins: Evaluation of monotonic versus fatigue behavior and surface characteristics.

This study assessed the mechanical properties and surface characteristics of dental prosthetic acrylic resin fabricated by 3D printing, comparing it with subtractive, pressing, and molding techniques. Bar-shaped specimens (N= 90; 65 × 10 × 3.3 mm; ISO:207951) were prepared and assigned into six groups: PRINT (3D printing vis stereolithography with PriZma 3D Bio Denture, Makertech Labs); SUB (subtractive manufacturing with Vipiblock Trilux, Vipi); PRESS Base (pressing using muffle with Thermo Vipi Wave, Vipi for base); PRESS Tooth (pressing with Onda-cryl, Clássico for tooth); MOLD Base (molding using addition silicone with Vipi Flash, Vipi for base); and MOLD Tooth (molding with Dencor, Clássico for tooth). Monotonic flexural strength (FS) and elastic modulus (E) were measured using a three-point bending approach (n= 5) on a universal testing machine at a crosshead speed of 5 mm/min. Fatigue testing (n= 10) followed similar geometry and settings, with a frequency of 2 Hz, initial stress level at 20 MPa, and stress increments of 5 MPa every 2,500 cycles. Surface roughness (n= 10) was assessed through profilometry, and fractographic and topographic analyses were conducted. Statistical analyses included One-Way ANOVA for monotonic FS, roughness, and E, along with Kaplan-Meier with Mantel-Cox post-hoc and Weibull analysis for fatigue strength. PRINT showed lower monotonic FS than the SUB and PRESS Tooth but comparable fatigue strength to these groups and superior to PRESS Base and MOLD (Base and Tooth) groups. All groups had similar Weibull moduli. Surface roughness of the PRINT group was comparable to most techniques but higher than the PRESS Tooth group. Fractographic analysis revealed fractures originating from surface defects under tensile stress, with SEM showing scratch patterns in all groups except PRINT, which had a more uniform surface. Despite its lower monotonic strength, 3D printed resin demonstrated comparable fatigue strength to subtractive and pressing methods and similar surface roughness to most methods, indicating its potential as a viable option for dental prosthesis.

Cannabidiol-loaded microparticles embedded in a porous hydrogel matrix for biomedical applications.

In this study, poly (lactic-co-glycolic acid) (PLGA) microparticles loaded with cannabidiol (CBD) were synthesized (PLGA@CBD microparticles) and embedded up to 10 wt% in a chondroitin sulfate/polyvinyl alcohol hydrogel matrix. In vitro chemical, physical, and biological assays were carried out to validate the potential use of the modified hydrogels as biomaterials. The microparticles had spherical morphology and a narrow range of size distribution. CBD encapsulation efficiency was around 52%, loading was approximately 50%. Microparticle addition to the hydrogels caused minor changes in their morphology, FTIR and thermal analyses confirmed these changes. Swelling degree and total porosity were reduced in the presence of microparticles, but similar hydrophilic and degradation in phosphate buffer solution behaviors were observed by all hydrogels. Rupture force and maximum strain at rupture were higher in the modified hydrogels, whereas modulus of elasticity was similar across all materials. Viability of primary human dental pulp cells up to 21 days was generally not influenced by the addition of PLGA@CBD microparticles. The control hydrogel showed no antimicrobial activity against Staphylococcus aureus, whereas hydrogels with 5% and 10% PLGA@CBD microparticles showed inhibition zones. In conclusion, the PLGA@CBD microparticles were fabricated and successfully embedded in a hydrogel matrix. Despite the hydrophobic nature of CBD, the physicochemical and morphological properties were generally similar for the hydrogels with and without the CBD-loaded microparticles. The data reported in this study suggested that this original biomaterial loaded with CBD oil has characteristics that could enable it to be used as a scaffold for tissue/cellular regeneration.

Impact of try-in paste removal on the fatigue behavior of bonded lithium disilicate ceramics.

This in vitro study assessed the effectiveness of three cleaning protocols (air-water spray, 37% phosphoric acid, or Ivoclean) on lithium disilicate restorations' fatigue behavior after try-in paste application, compared to a clean condition. Lithium disilicate discs (IPS e.max CAD, Ivoclar) with Ø-= 12 mm and 1 mm thickness were prepared from prefabricated CAD-CAM blocks, polished, subjected to CAD-CAM milling topography simulation and crystallization. After, etching with 5% hydrofluoric acid and the application of try-in paste (Variolink try-in paste shade white; load of 2.5 N for 5 min) was performed. Discs that received try-in paste were divided into three groups according to the removal protocol: SPRAY - air-water spray for 30 s; HPO - active application of 37% phosphoric acid for 60 s; IVOC - application of Ivoclean for 20 s. Control group (CTRL group) did not receive the try-in paste application. Half of the specimens (n= 15) were tested in the baseline condition (24 h up to 7 days), and the others underwent 25,000 thermal cycles (5 - 55 °C) + 210 days of distilled water storage (37 °C). Additional specimens (n= 3) underwent monotonic testing (1 mm/min). Fatigue testing involved a cyclic fatigue approach (20 Hz, initial load = 100 N - 5000 cycles, step size = 50 N - 10,000 cycles) until a visible crack appeared. Fractographic and topographic analyses were performed. Fatigue data were statistically analyzed with two-way ANOVA, Kaplan-Meier log-rank (Mantel-Cox), and independent t-test (α= 0.05). In the baseline condition, the IVOC group resulted in a superior fatigue behavior compared to the CTRL and SPRAY groups, but similar to the HPO group. The HPO and SPRAY presented a similar fatigue behavior to the CTRL group. It was noticed a decrease in fatigue behavior after aging, which resulted in all the cleaning protocols leading to similar fatigue behavior compared to the CTRL group. On the SPRAY group surface, try-in pastes remnants were noticed. In summary, despite a detrimental impact at baseline conditions, all tested cleaning protocols seem proper to remove the try-in paste from the ceramic's surface in the long-term evaluation.

Effects of solvent type and UV post-cure time on 3D-printed restorative polymers.

OBJECTIVES: This study evaluated the impact of different solvents and UV post-curing times on properties of 3D printing resins for provisional restorations. METHODS: The post-processing methods were tested using two solvents (isopropyl alcohol or absolute ethanol) and three UV times (5, 10, or 30 min). The resins tested were Resilab 3D Temp, Printax Temp, and Prizma Bioprov. Microhardness (kgf/mm2), fracture toughness (KIC, MPa√m), surface roughness (Ra, µm), gloss (gloss units), and degree of CC conversion (%DC) were measured (n = 8). All response variables were collected from the same specimen. The specimens were 3D printed using an SLA/LCD printer (150° angulation, 50 µm layer thickness). Light exposure times were adjusted for each material, and the post-processing methods were applied using an all-in-one machine immediately after printing. Data were analyzed using Three-Way ANOVA (α = 0.05). RESULTS: Microhardness was affected by UV post-cure time and 3D resin. Resilab showed higher microhardness with isopropyl alcohol and 30-min UV time, while Printax had higher microhardness with absolute ethanol. KIC was influenced by solvent type, UV time, and 3D resin, with varying effects on different resins. Roughness was affected by 3D resin and UV time, but no significant differences were seen for Resilab or Prizma. Gloss was influenced by 3D resin, and for Prizma, it was lower with specific solvent/UV time combinations. DC was influenced by 3D resin, with each resin behaving differently. SIGNIFICANCE: Tailoring the combination of 3D resin, solvent washing type, and UV post-curing time is important to achieve optimal mechanical and aesthetic outcomes for restorations.

Bonding stability of universal adhesives to feldspathic ceramic with or without prior silane application.

PURPOSE: This study aimed to assess the bonding stability of three universal adhesives to a CAD-CAM feldspathic ceramic with or without prior silane application. MATERIALS AND METHODS: The universal adhesives tested were Ambar Universal (FGM), Single Bond Universal (3M), and Ybond Universal (Yller). Scotchbond Multipurpose Plus (3M) was used as a control. The silane used was RelyX Ceramic Primer (3M). Microtensile bond strength (µTBS) to Vitablocs Mark II was measured after 24 h or 6 months of water aging (n = 20). Failure modes were observed through scanning electron microscopy, and pH and degree of C=C conversion (DC) of the adhesives were measured (n = 3). Data were analyzed using one-, two-, and three-way ANOVA. RESULTS: The pH values differed significantly among the adhesives (p < 0.001), while the DC was similar (p = 0.141). The universal adhesives showed significant differences in µTBS, with higher immediate results when using silane and lower results after aging. Notably, a significant decrease in µTBS was observed after 6 months when silane was applied. In contrast, the control adhesive exhibited consistent results between the 24-h and 6-month storage periods. The universal adhesives showed a decrease in µTBS ranging from 25.5% to 40.1% after prolonged storage. Adhesive failures were predominant in all groups. The presence or absence of silane in the adhesive composition did not affect the bonding performance. CONCLUSIONS: The application of a separate silane coupling agent improved the immediate bond strength of universal adhesives to CAD-CAM feldspathic ceramic. However, this bond strength significantly decreased after 6 months of water aging. The bond strength remained stable for universal adhesives when applied without silane after 6 months of aging.

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.

Longevity of composite restorations is definitely not only about materials.

OBJECTIVES: This review study provides an overview of factors that influence the longevity of all types of direct resin composite restorations. METHODS: A systematic search was performed in PubMed, Scopus, and Web of Science databases for articles reporting data from primary longitudinal clinical studies on composite longevity published 2011-2021. Prospective or retrospective studies with restorations in permanent dentition, with follow-up periods of at least 5 years were included. RESULTS: In total, 33 articles were included with different study designs, practice settings, datasets, countries of origin, and sample sizes. Annual failure rates of restorations ranged from 0.08% to 6.3%. Survival rates varied between 23% and 97.7%, success rates varied between 43.4% and 98.7%. Secondary caries, fractures, and esthetic compromise were main reasons for failures. Risk factors for reduced restoration durability included patient-level factors (e.g., caries risk, parafunctional habits, number of check-ups per year, socioeconomic status), dentist factors (different operators, operator's experience), and tooth/restoration factors (endodontic treatment, type of tooth, number of restored surfaces). Patient gender and the composite used generally did not influence durability. SIGNIFICANCE: A number of risk factors are involved in the longevity of composite restorations. Differences between composites play a minor role in durability, assuming that materials and techniques are properly applied by dentists. Patient factors play a major role in longevity. The decision-making process implemented by dentists relative to the diagnosis of aging or failed restorations may also affect the longevity of restorations. Clinicians should treat patients comprehensively and promote a healthy lifestyle to ensure longevity.

Resin Composites in Posterior Teeth: Clinical Performance and Direct Restorative Techniques.

Resin composites are the most versatile restorative materials used in dentistry and the first choice for restoring posterior teeth. This article reviews aspects that influence the clinical performance of composite restorations and addresses clinically relevant issues regarding different direct techniques for restoring posterior teeth that could be performed in varied clinical situations. The article discusses the results of long-term clinical trials with resin composites and the materials available in the market for posterior restorations. The importance of photoactivation is presented, including aspects concerning the improvement of the efficiency of light-curing procedures. With regard to the restorative techniques, the article addresses key elements and occlusion levels for restoring Class I and Class II cavities, in addition to restorative strategies using different shades/opacities of resin composites in incremental techniques, restorations using bulk-fill composites, and shade-matching composites.

COVID-19 incidence, severity, medication use, and vaccination among dentists: survey during the second wave in Brazil.

OBJECTIVE: This cross-sectional study with dentists in Brazil assessed the COVID-19 incidence and severity, its vaccination status, and the level of confidence in vaccines in May 2021 (COVID-19 second wave). The medications used to prevent or treat COVID-19, including controversial substances (vitamin D, ivermectin, zinc, and chloroquine), were analyzed. METHODOLOGY: Dentists were recruited by email and responded to a pretested questionnaire until May 31, 2021. Bivariate and multivariate regression analyses were performed (α=0.05). Prevalence ratios were calculated for the association between professional characteristics and two outcomes: SARS-CoV-2 infection and use of controversial substances. RESULTS: In total, 1,907 responses were received (return rate of 21.2%). One third of dentists reported intermediate levels of confidence in the safety and efficacy of COVID-19 vaccines, but 96% had received at least one vaccine dose, mainly CoronaVac. The effect of the pandemic on dental practice was classified as lower/much lower, in comparison with the first wave, by 46% of participants. Moreover, 27% of dentists had already tested positive for SARS-CoV-2 and about 50% had relatives or friends who had been hospitalized or died from COVID-19. At least one medication was used by 59% of participants and 43% used two or more substances. Vitamin D (41%), ivermectin (35%), and zinc (29%) were the most frequent substances. More experienced dentists (≥21 years of professional experience) were 42% more likely to use controversial substances than less experienced dentists. The prevalence of use of controversial substances was 30% higher among dentists with residency or advanced training, such as postgraduate degrees, in comparison with participants holding MSc or PhD degrees. Participants with low confidence in vaccines were 2.1 times more likely to use controversial substances than participants with a very high confidence. CONCLUSION: The results of this study show the high severity of the COVID-19 pandemic in Brazil and raised questions about the use of scientific evidence by dentists in their decision to use controversial substances.

Cannabidiol in Dentistry: A Scoping Review.

Cannabidiol (CBD) has been gaining increased attention in contemporary society but seems to have been little explored in dentistry. This scoping review mapped the scientific and technological scenarios related to the use of CBD in dentistry. Peer-reviewed publications were searched in five international databases, patents were searched in five technological platforms. In total, 11 articles and 13 patents involving CBD in dentistry-related applications were included. The countries contributing to most articles were Brazil (27.3%) and USA (18.2%). The studies involved experiments on animals (63.6%) and/or using bacteria or cells (36.4%), and no clinical study was found. Three different applications of CBD were observed: periodontal therapy (45.4%), aid for bone regeneration (27.3%), and general use in oral therapies (27.3%). Patent inventors were based in China (53.8%) or USA (46.2%). The patent claims were mainly compositions for oral care, tooth whitening, injury repair, antifungal, anti-inflammatory, and analgesic effects. A total of 76.9% of the patents were filed in association with a company. In general, research suggests that CBD has promising biological properties for applications in dentistry, whereas patents indicate that the current interest of industry relies on compositions for oral care. There appears to be extensive room available for research and technological applications of CBD in dentistry.

Deterioration of anterior resin composite restorations in moderate to severe tooth wear patients: 3-year results.

OBJECTIVES: Deterioration in anterior resin composite restorations placed in tooth wear patients was investigated after 36 months. MATERIALS AND METHODS: Data collected prospectively for 47 participants of the Radboud Tooth Wear Project were used (41 ± 8 years, 90% male, n = 270 restorations). Restorations were individually evaluated using intraoral photographs and 3D scans to rate modified FDI scores and to record the presence of degradation features. Four groups with distinct combinations of composites and techniques were assessed, and multivariable logistic regression models were used to analyze the data (p < 0.05). RESULTS: For all groups together, early degradation signs were present at 1 month: irregularities (41.5%) and ditching (7.4%) were observed at the surface and adhesive interfaces. The frequency of irregularities decreased in the 36-month evaluation (37%), but ditching (12.2%) and fractures (10.7%) were more common. The most frequent deterioration (based on photographs) was observed for staining (44%) and loss of luster (31%). In 3D scans, the most frequent were for wear (25%), marginal adaptation (24%), and the presence of irregularities (19%). Canines had 5.5 times more chances of deterioration by ditching than incisors (p < 0.001). The differences between composites and restorative techniques were minor. CONCLUSIONS: A continuous degradation process of restorations placed in tooth wear patients was observed in anterior teeth restored with different composites, with a progression of the deterioration over 36 months. CLINICAL RELEVANCE: When placing anterior resin composite restorations in tooth wear patients, it could be important to establish realistic expectations and the need for checkup appointments.

Effect of ultrasound on preheated resin composites used as ceramic luting agents.

This study investigated the effect of ultrasound application when luting ceramic using two preheated composites that show distinct responses to preheating at 69°C: Filtek Z100 and Z350XT. RelyX Veneer was the control. Feldspar disks were luted using the resin-based luting agents (RBLAs), and ultrasound was tested. Biaxial flexure strength (σbf) was calculated at z-axial positions of the luted disks (z=0; z=-t2). Microtensile bond strength (µTBS) to ceramic was tested (n=30). Data were analyzed at α=0.05. At z=0, the σbf was higher for Z350 when ultrasound was not used. When ultrasound was applied, the σbf was similar between Z350 and Z100. At z=-t2, differences across the RBLAs were observed: Z350 was superior than Z100 and control without ultrasound. Ultrasound increased σbf for Z100 at both axial positions. The preheated composites yielded higher µTBS than the control. Ultrasonication increased the mechanical performance of ceramic luted with Z100 without influencing the film thickness.

A multi-country survey on the impact of COVID-19 on dental practice and dentists' feelings in Latin America.

BACKGROUND: The COVID-19 pandemic has significantly influenced the routine of healthcare workers. This study investigated the impact of the pandemic on dental practice and dentists' feelings in Latin America. METHODS: A survey was conducted with dentists from 11 Spanish-speaking Latin American countries in September-December 2020. Professionals were invited by email and via an open campaign promoted on social media. The questions investigated dental care routines, practice changes, and feelings about the pandemic. Descriptive statistics were used to identify frequencies and distributions of variables. Proportions were compared using chi-square tests. RESULTS: A total of 2127 responses were collected from a sample with diverse demographic, sex, work, and education characteristics. The impact of COVID-19 was considered high/very high by 60% of respondents. The volume of patients assisted weekly was lower compared with the pre-pandemic period (mean reduction = 14 ± 15 patients). A high rate of fear to contracting the COVID-19 at work was observed (85%); 4.9% of participants had a positive COVID-19 test. The main professional challenges faced by respondents were reduction in the number of patients or financial gain (35%), fear of contracting COVID-19 (34%), and burden with or difficulty in purchasing new personal protective equipment (22%). The fear to contracting COVID-19 was influenced by the number of weekly appointments. A positive test by the dentists was associated with their reports of having assisted COVID-19 patients. The most cited feelings about the pandemic were uncertainty, fear, worry, anxiety, and stress. Negative feelings were more prevalent for professionals who did not receive training for COVID-19 preventive measures and those reporting higher levels of fear to contract the disease. CONCLUSION: This multi-country survey indicated a high impact of the pandemic on dental care routines in Latin America. A massive prevalence of bad feelings was associated with the pandemic.

The Ability of Two Chewing Simulation Devices in Emulating the Clinical Deterioration of Anterior Composite Restorations in Severely Worn Teeth.

PURPOSE: This study investigated the ability of two chewing simulation devices to emulate in vitro the clinical deterioration observed in anterior composite restorations in severe tooth-wear patients. MATERIALS AND METHODS: Advanced tooth wear was simulated in bovine incisors, which were restored with palatal and buccal direct composite veneer restorations. The incisal edges of restorations were subjected to 960K cycles of either compressive loading (Biocycle-V2; 125 N at 2 Hz) or wear and mechanical loading (Rub and Roll; 30 N at 20 rpm). Surface degradation was rated using FDI scores to compare the chewing devices (Fisher's test, a = 0.05). Topography and deterioration of restorations was analyzed using SEM. The ability to emulate the deterioration was investigated by comparing the surface degradation observed in vitro with the clinical degradation observed in restorations placed in severe tooth-wear patients after 3.5 years. RESULTS: Distinct degradation patterns were observed between the simulation devices: Biocycle-V2 generated deterioration that was not comparable to the clinical situation, including contact damage, minor wear, and localized roughening. The degradation caused by Rub and Roll was more similar to the in vivo situation, including wear facets, chipping, delamination, staining, and marginal ditching. The FDI scores were different between the chewing devices for surface/marginal staining, material/retention, and marginal adaptation (p = 0.003). SEM analysis showed microcracking at the interface between composite layers at the incisal edges. CONCLUSIONS: The Rub and Roll chewing device was able to emulate the clinical deterioration observed in anterior restorations in severe tooth-wear patients and thus may be used as an oral-cavity simulation method, contributing to translational research.

Clinical performance of posterior resin composite restorations after up to 33 years.

OBJECTIVES: This retrospective study evaluated the performance of posterior composites after up to 33 years of clinical service and investigated factors associated with the risk of failures over time including patient- and tooth-related variables. METHODS: Patients who received at least one Class I or Class II direct composite restoration in a private office in 1986-1992 and had follow-up appointments were included. Failures and interventions over time were investigated using the dental records. A follow-up clinical recall was carried out in 2020. Two scenarios were considered: restorations that did not require any intervention (success) or restorations that were repaired and still functional (survival). Multivariate Cox regression analyses and Kaplan-Meier curves were performed using success and survival rates (p < 0.05). RESULTS: One hundred patient records and 683 restorations were included. A total of 353 failures were reported (success rate= 48%). Main reasons for failure were fracture and secondary caries. Most interventions after failures were repairs. Replacements were registered in 183 cases (survival rate= 73%). Annual failure rates were below 2.5% (success) and 1.1% (survival). Larger restorations and maxillary molars had higher failure risks. No significant differences in success rates among different resin composites was observed. A typical observation in this sample of restorations was the presence of moderate to advanced signs of aging, including marginal and surface staining, wear, chipping, changes in anatomical shape and translucency. Clearly aged restorations were still clinically satisfactory. SIGNIFICANCE: This long-term, practice-based study indicates that resin composites can be used to restore posterior teeth with a long-lasting durability.

Bond strength of self-adhesive flowable composite resins to dental tissues: A systematic review and meta-analysis of in vitro studies.

STATEMENT OF PROBLEM: Although the clinical use of self-adhesive flowable composite resins is convenient, the decision to use flowable or conventional composite resin remains controversial. PURPOSE: The purpose of this systematic review and meta-analysis was to assess the in vitro bond strength of self-adhesive flowable composite resins to enamel or dentin compared with conventional composite resins using etch-and-rinse or self-etch adhesive systems. MATERIAL AND METHODS: Two independent reviewers performed searches in the PubMed (MEDLINE), Cochrane Wiley, Web of Science, Scopus, and Google Scholar databases for studies reporting on the bond strength of self-adhesive flowable and conventional composite resins to enamel and dentin published from January 2010 up to September 2020. A meta-analysis software program was used for the meta-analysis. Comparisons were conducted using standardized mean differences considering the random-effects model (α=.05). RESULTS: Twenty-two studies were considered for the meta-analysis. Immediate and long-term bond strength to enamel was improved when a conventional composite resin was used in combination with an adhesive system (P<.001). Bond strength to dentin was improved by using an adhesive system in combination with a conventional composite resin (P<.001). CONCLUSIONS: The bond strength of self-adhesive flowable composite resins is lower than that of conventional composite resins, indicating limited ability to bond to enamel and dentin.

Laboratory methods to simulate the mechanical degradation of resin composite restorations.

OBJECTIVES: This study reviewed the literature to identify in vitro approaches that have been used to simulate the mechanical degradation and fatigue of resin composite restorations. METHODS: A search for articles was carried out in 4 databases and included studies in which composite restorations were bonded to teeth and subject to cyclic loading. Articles were assessed for eligibility, and the following items were the extracted from the included studies: authors, country, year, materials tested, simulation device and details including load magnitude and frequency, number of cycles, type of antagonist, test medium, and temperature. Data were analyzed descriptively. RESULTS: The 49 studies included showed a high level of heterogeneity in methods, devices, and test parameters. Nineteen different simulation devices were used, applying loads varying between 30 and 2900 N, and frequencies varying between 0.4 and 12 Hz. The load and frequency used most often were ~ 50 N (63.3%) and 1.5-1.7 Hz (32.7%). The number of cycles varied between 10 K and 2.4 M, 1.2 M was the most prevalent (40.8%). The majority of studies combined cyclic loading with at least one additional aging method: static liquid storage, thermo-mechanical cycling applied simultaneously, and thermal cycling as a discrete aging step were the three most frequent methods. The overall evidence indicated reporting problems, and suggested a lack of clinical validation of the research methods used. SIGNIFICANCE: Validation studies, underlying clinical supporting data, and better reporting practices are needed for further improving research on the topic. Specific suggestions for future studies are provided.

COVID-19 incidence, severity, medication use, and vaccination among dentists: survey during the second wave in Brazil

Abstract Objective This cross-sectional study with dentists in Brazil assessed the COVID-19 incidence and severity, its vaccination status, and the level of confidence in vaccines in May 2021 (COVID-19 second wave). The medications used to prevent or treat COVID-19, including controversial substances (vitamin D, ivermectin, zinc, and chloroquine), were analyzed. Methodology Dentists were recruited by email and responded to a pretested questionnaire until May 31, 2021. Bivariate and multivariate regression analyses were performed (α=0.05). Prevalence ratios were calculated for the association between professional characteristics and two outcomes: SARS-CoV-2 infection and use of controversial substances. Results In total, 1,907 responses were received (return rate of 21.2%). One third of dentists reported intermediate levels of confidence in the safety and efficacy of COVID-19 vaccines, but 96% had received at least one vaccine dose, mainly CoronaVac. The effect of the pandemic on dental practice was classified as lower/much lower, in comparison with the first wave, by 46% of participants. Moreover, 27% of dentists had already tested positive for SARS-CoV-2 and about 50% had relatives or friends who had been hospitalized or died from COVID-19. At least one medication was used by 59% of participants and 43% used two or more substances. Vitamin D (41%), ivermectin (35%), and zinc (29%) were the most frequent substances. More experienced dentists (≥21 years of professional experience) were 42% more likely to use controversial substances than less experienced dentists. The prevalence of use of controversial substances was 30% higher among dentists with residency or advanced training, such as postgraduate degrees, in comparison with participants holding MSc or PhD degrees. Participants with low confidence in vaccines were 2.1 times more likely to use controversial substances than participants with a very high confidence. Conclusion The results of this study show the high severity of the COVID-19 pandemic in Brazil and raised questions about the use of scientific evidence by dentists in their decision to use controversial substances.

Ceramic Laminate Veneers Luted with Preheated Resin Composite: A 10-Year Clinical Report.

Resin cement and preheated restorative resin composite may be used for luting laminate veneers. The main advantage of resin composite is increased wear resistance, which could lead to better marginal performance in long term. This article reports a clinical treatment with feldspar laminate veneers luted to the maxillary teeth with preheated resin composite in a private practice. Case was finalized in May 2009 and followed by 10 years. Excellent clinical service and remarkable long-lasting marginal integrity were observed after 123 months. Scanning electron microscopy analysis showed no wear, gaps, or ditching at the margins. Restorative margins showed a smooth transition between ceramic and tooth with no signs of degradation. Preheated resin composite for luting ceramic laminate veneers may be considered an excellent clinical option.