Evaluating mechanical and surface properties of zirconia-containing composites: 3D printing, subtractive, and layering techniques.

This study assessed the monotonic and fatigue flexural strength (FS), elastic modulus (E), and surface characteristics of a 3D printed zirconia-containing resin composite compared to subtractive and conventional layering methods. Specimens, including discs (n = 15; Ø = 15 mm × 1.2 mm) and bars (n = 15; 14 × 4 × 1.2 mm), were prepared and categorized into three groups: 3D printing (3D printing - PriZma 3D Bio Crown, Makertech), Subtractive (Lava Ultimate blocks, 3M), and Layering (Filtek Z350 XT, 3M). Monotonic tests were performed on the discs using a piston-on-three-balls setup, while fatigue tests employed similar parameters with a frequency of 10 Hz, initial stress at 20 MPa, and stress increments every 5000 cycles. The E was determined through three-point-bending test using bars. Surface roughness, fractographic, and topographic analyses were conducted. Statistical analyses included One-way ANOVA for monotonic FS and roughness, Kruskal-Wallis for E, and Kaplan-Meier with post-hoc Mantel-Cox and Weibull analysis for fatigue strength. Results revealed higher monotonic strength in the Subtractive group compared to 3D printing (p = 0.02) and Layering (p = 0.04), while 3D Printing and Layering exhibited similarities (p = 0.88). Fatigue data indicated significant differences across all groups (3D Printing < Layering < Subtractive; p = 0.00 and p = 0.04, respectively). Mechanical reliability was comparable across groups. 3D printing and Subtractive demonstrated similar E, both surpassing Layering. Moreover, 3D printing exhibited higher surface roughness than Subtractive and Layering (p < 0.05). Fractographic analysis indicated that fractures initiated at surface defects located in the area subjected to tensile stress concentration. A porous surface was observed in the 3D Printing group and a more compact surface in Subtractive and Layering methods. This study distinguishes the unique properties of 3D printed resin when compared to conventional layering and subtractive methods for resin-based materials. 3D printed shows comparable monotonic strength to layering but lags behind in fatigue strength, with subtractive resin demonstrating superior performance. Both 3D printed and subtractive exhibit similar elastic moduli, surpassing layering. However, 3D printed resin displays higher surface roughness compared to subtractive and layering methods. The study suggests a need for improvement in the mechanical performance of 3D printed material.

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.

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.

Charcoal-based dentifrices and powders: analyses of product labels, Instagram engagement, and altmetrics

Abstract This study identified charcoal-based dentifrices and abrasive powders sold in Brazil and analyzed their label information. The products were searched in four online shopping platforms. The same products were searched on Instagram and their engagement metrics were investigated. Furthermore, a literature review of international publications assessing charcoal dentifrices and powders was conducted, and altmetrics were collected (Altmetric and PlumX). Thirty-six products were found with prices between $0.4-22 USD. Most frequent words in product description were sodium, stain, whitening, oil, xylitol, and coconut. Only 3 products contained fluoride. Bactericidal, antiviral, antifungal, and anti-inflammatory activities were indicated, in addition to non-scientific claims such as calming teeth or increasing oral immunity. In total, 72% of products had Instagram profiles, which generally showed low engagement rates (81%) and medium audience quality scores (65%). Twenty-two articles were found in the literature, from which 21 were in vitro studies. The single clinical study was sponsored by a charcoal product and had no control group. In total, 23% of studies showed positive results and 55% reported negative results for the charcoal products, which included no whitening ability, increased roughness, surface alterations, and lower demineralization prevention ability. Altmetric scores for the included articles varied from 0 to 55, with 40.9% of studies mentioned online. In conclusion, charcoal-based products are using marketing strategies on Instagram but their current engagement with the public is not high. Consumers are being exposed to charcoal products whose potential risks to health are still unknown.

Resumo Este estudo identificou dentifrícios e pós abrasivos de carvão vendidos no Brasil e analisou suas informações de rótulo. Os produtos foram pesquisados em quatro plataformas de compras online. Os mesmos produtos foram pesquisados no Instagram e métricas de engajamento dos perfis foram investigadas. Além disso, foi realizada uma revisão da literatura buscando publicações internacionais que avaliaram dentifrícios e pós de carvão; dados de altmetria foram coletados (Altmetric e PlumX). Foram encontrados 36 produtos com preços entre US$ 0,4-22. As palavras mais frequentes na descrição dos produtos foram sódio, mancha, clareamento, óleo, xilitol e coco. Apenas 3 produtos continham flúor. Foram indicadas atividades bactericidas, antivirais, antifúngicas e anti-inflamatórias, além de alegações não-científicas como acalmar dentes ou aumentar a imunidade oral. No total, 72% dos produtos tinham perfis no Instagram, que geralmente apresentavam baixas taxas de engajamento (81%) e média qualidade de audiência (65%). Vinte e dois artigos foram encontrados na literatura, dos quais 21 foram estudos in vitro. O único estudo clínico foi patrocinado por um produto de carvão e não tinha grupo controle. No total, 23% dos estudos apresentaram resultados positivos e 55% relataram resultados negativos para os produtos de carvão, que incluíram incapacidade de clareamento, aumento da rugosidade, alterações superficiais e menor capacidade de prevenção da desmineralização do esmalte. A altmetria dos artigos incluídos variou de 0 a 55, com 40,9% dos estudos sendo mencionados online. Em conclusão, os produtos à base de carvão estão usando estratégias de marketing no Instagram, mas seu engajamento atual com o público não é alto. Consumidores estão sendo expostos a produtos de carvão cujos potenciais riscos à saúde ainda são desconhecidos

Email vs. instagram recruitment strategies for online survey research

Abstract In this study, we describe a method for reaching a target population (i.e., dentists practicing in Brazil) to engage in survey research using traditional e-mail invites and recruitment campaigns created on Instagram. This study addresses methodological aspects and compares respondents reached by different methods. A pre-tested questionnaire was used and participants were recruited for 10 days via a source list of email addresses and two discrete Instagram organic open campaigns. A total of 3,122 responses were collected: 509 participants were recruited by email (2.1% response rate) and 2,613 by the two Instagram campaigns (20.7% and 11.7% conversion rates), respectively. Response/min collection rates in the first 24 h ranged between 0.23 (email) and 1.09 (first campaign). In total, 98.8% of all responses were received in the first 48 h for the different recruitment strategies. There were significant differences for all demographic variables (p< 0.001) between email and Instagram respondents, except for sex (p=0.37). Instagram respondents were slightly older, had more professional experience (years in practice), and a higher graduate education level than email respondents. Moreover, most email and Instagram respondents worked in the public sector and private practice, respectively. Although both strategies could collect responses from all Brazilian regions, email responses were slightly better distributed across the five territorial areas compared to Instagram. This study provides evidence that survey recruitment of a diverse, large population sample using Instagram is feasible. However, combination of email and Instagram recruitment led to a more diverse population and improved response rates.

Resumo Neste estudo, descrevemos um método para atingir uma população-alvo (dentistas atuando no Brasil) para se engajar em pesquisa do tipo enquete (survey) utilizando convites tradicionais por e-mail e campanhas de recrutamento criadas no Instagram. Este estudo aborda aspectos metodológicos e compara as pessoas entrevistadas alcançadas por diferentes métodos. Foi utilizado um questionário pré-testado e os(as) participantes foram recrutados(as) por 10 dias por meio de uma lista de endereços de e-mail e duas campanhas abertas orgânicas independentes no Instagram. Foram coletadas 3122 respostas: 509 participantes foram recrutados(as) por e-mail (taxa de resposta 2,1%) e 2613 pelas duas campanhas do Instagram (taxas de conversão 20,7% e 11,7%), respectivamente. As taxas de coleta de resposta/min nas primeiras 24h variaram entre 0,23 (e-mail) e 1,09 (primeira campanha). No total, 98,8% das respostas foram recebidas nas primeiras 48h para as diferentes estratégias de recrutamento. Houve diferenças significativas para todas as variáveis demográficas (p<0,001) entre recrutados(as) por e-mail e Instagram, com exceção de sexo (p=0,37). As pessoas recrutadas via Instagram eram um pouco mais velhas, tinham mais experiência profissional (anos na prática) e nível de pós-graduação superior às entrevistadas por e-mail. Além disso, a maioria dos entrevistados por e-mail e Instagram trabalhava no setor público e na prática privada, respectivamente. Embora ambas estratégias tenham sido capazes de coletar respostas de todas as regiões brasileiras, as respostas por e-mail foram ligeiramente melhor distribuídas nas cinco áreas territoriais em comparação ao Instagram. Este estudo fornece evidências de que o recrutamento de uma amostra de população diversificada e grande usando o Instagram é viável. No entanto, a combinação de e-mail e Instagram no recrutamento levou a uma população mais diversificada e melhores taxas de resposta.

Brazilian articles in top-tier dental journals and influence of international collaboration on citation rates

Abstract This study investigated the presence of co-authorship from Brazil in articles published in top-tier dental journals and analyzed the influence of international collaboration, article type (original research or review), and funding on citation rates. Articles published between 2015 and 2017 in 38 selected journals from 14 dental subareas were screened in Scopus. Bibliographic information, citation counts, and funding details were recorded for all articles (N=15619). Collaboration with other top-10 publishing countries in dentistry was registered. Annual citations averages (ACA) were calculated. A linear regression model assessed differences in ACA between subareas. Multilevel linear regression models evaluated the influence of article type, funding, and presence of international collaboration in ACA. Brazil was a frequent co-author of articles published in the period (top 3: USA=25.5%; Brazil=13.8%; Germany=9.2%) and the country with most publications in two subareas. The subjects with the biggest share of Brazil are Operative Dentistry/Cariology, Dental Materials, and Endodontics. Brazil was second in total citations, but fifth in citation averages per article. From the total of 2155 articles co-authored by Brazil, 74.8% had no co-authorship from other top-10 publishing countries. USA (17.8%), Italy (4.2%), and UK (3.2%) were the main co-author countries, but the main collaboration country varied between subjects. Implantology and Dental Materials were the subjects with most international co-authorship. Review articles and articles with international collaboration were associated with increased citation rates, whereas the presence of study funding did not influence the citations.

Resumo Este estudo investigou a presença de coautoria do Brasil em artigos publicados nos principais periódicos odontológicos e analisou a influência da colaboração internacional, tipo de artigo (artigo original ou revisão) e financiamento nas taxas de citação. Artigos publicados entre 2015 e 2017 em 38 periódicos selecionados de 14 subáreas foram pesquisados no Scopus. Informações bibliográficas, número de citações e detalhes de financiamento foram registrados para todos os artigos (N=15619). Colaboração com outros países no top-10 de publicações em odontologia foi coletada. Médias anuais de citação (MAC) foram calculadas. Um modelo de regressão linear avaliou as diferenças de MAC entre as subáreas. Modelos multinível de regressão linear avaliaram a influência do tipo de artigo, financiamento e presença de colaboração internacional nas MAC. O Brasil foi coautor frequente de artigos publicados no período (top 3: EUA=25,5%; Brasil=13,8%; Alemanha=9,2%) e o país com mais publicações em duas subáreas. As subáreas com maior participação do Brasil foram Dentística/Cariologia, Materiais Dentários e Endodontia. O Brasil foi o segundo no total de citações, porém quinto em citações médias por artigo. Do total de 2155 artigos de coautoria do Brasil, 74,8% não tiveram coautoria de outros países do top-10 de publicação. EUA (17,8%), Itália (4,2%) e Reino Unido (3,2%) foram os principais países coautores, porém o principal país de colaboração variou entre as subáreas. Implantodontia e Materiais Dentários foram as subáreas com mais coautoria internacional. Artigos de revisão e artigos com colaboração internacional foram associados a maiores taxas de citação, enquanto a presença de financiamento do estudo não influenciou as citações.

Characterization of Bis-Acryl Composite Resins for Provisional Restorations

Abstract This study investigated the in vitro performance of the commercial bis-acryl composite resins Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) and ProviPlast (PVP, Biodinamica). Characterization involved optical (color stability, translucency parameter, fluorescence), surface (roughness, morphology and elemental composition), physical-chemical (viscosity, polymerization kinetics) and mechanical analyses (Poisson ratio, biaxial flexural strength, flexural modulus). Most tests were carried out after 24 h, but optical and mechanical analyses were carried out after storage in water at 37 °C for 1, 15, and 30 days. Data were statistically analyzed (a=0.05). Most results were material dependent. SYS and PT4 showed stability in color and translucency over time. All materials had similar or higher fluorescence than human enamel. SC2 and PVP showed rougher surfaces than the other bis-acryl composites. Smaller filler particles were observed on the surface of PT4 and PVP compared with the coarser particles from ST2 and SYS. Viscosity readings indicated a thixotropic behavior for all tested materials. SYS had the lowest and PT4 the highest degree of C=C conversion after 10 min. In the polymerization kinetics, PT4 had the highest maximum polymerization rate and reached earlier the transition between polymerization autoacceleration and autodeceleration. PT4 and SYS had significantly higher flexural strength and modulus than ST2 and PVP for most storage times. Results for Poisson ratio varied between materials. Longer storage periods were generally associated with higher frequency of catastrophic failures in the flexural tests. In conclusion, the performance of bis-acryl composite resins varied largely among materials.

Resumo Este estudo investigou o desempenho in vitro de quatro resinas compostas bisacrílicas comerciais: Systemp C&B II (SYS, Ivoclar Vivadent), Protemp 4 (PT4, 3M ESPE), Structur 2C (ST2, Voco) e ProviPlast (PVP, Biodinamica). A caracterização envolveu análises ópticas (estabilidade de cor, parâmetro de translucidez, fluorescência), de superfície (rugosidade, morfologia e composição elementar), físico-químicas (viscosidade, cinética de polimerização) e mecânicas (razão de Poisson, resistência à flexão biaxial, módulo de elasticidade). A maioria dos testes foram realizados após 24 h, enquanto análises ópticas e mecânicas foram realizadas após armazenamento em água a 37 °C por 1, 15 e 30 dias. Os dados foram analisados estatisticamente (a=0,05). Grande parte dos resultados foi dependente do material. SYS e PT4 mostraram estabilidade de cor e translucidez ao longo do tempo. Todos os materiais apresentaram fluorescência similar ou maior que o esmalte humano. SC2 e PVP apresentaram superfícies mais rugosas que os outros materiais. Menores partículas de carga foram observadas na superfície de PT4 e PVP comparadas às partículas mais irregulares de ST2 e SYS. As leituras de viscosidade indicaram comportamento tixotrópico para todos os materiais testados. SYS teve a menor e PT4 o maior grau de conversão de C=C após 10 min. Na cinética de polimerização, PT4 teve a maior taxa máxima de polimerização e atingiu mais cedo a transição entre autoaceleração e autodesaceleração da polimerização. PT4 e SYS apresentaram resistência à flexão e módulo de elasticidade significativamente maiores que ST2 e PVP na maioria dos períodos de armazenamento. Resultados da razão de Poisson variaram entre os materiais. Períodos mais longos de armazenamento foram em geral associados a maior frequência de falhas catastróficas nos testes de flexão. Em conclusão, o desempenho das resinas compostas bisacrílicas variou amplamente entre os materiais.

Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions

OBJECTIVES: The aim of this study was to investigate the bond strength of ceramic restorations luted using a self-adhesive resin cement (RelyX Unicem, 3M ESPE) under different dentin conditions. MATERIAL AND METHODS: In the experimental groups, ceramic restorations were luted to bovine incisors with RelyX Unicem under the following conditions: [Dry dentin]: surface was dried using air stream for 15 s; [Moist dentin]: excess dentin moisture was removed with absorbent paper; [Bonding agent]: Clearfil SE Bond (Kuraray) self-etching adhesive system was previously applied to dentin. In the Control group, cementation was done using an etch-and-rinse adhesive (Excite DSC) and Variolink II resin cement (Ivoclar Vivadent). Photoactivation of the resin cements was performed with UltraLume LED 5 unit (Ultradent). The restorations (n=5 per group) were sectioned into beams and microtensile testing was carried out. Data were subjected to ANOVA and Tukey's test (p<0.05). Failure modes were classifed under Scanning Electron Microscopic (SEM) (x120 magnifcation). RESULTS: The bond strength was dependent on the moisture status of the dentin. Bond strength in the "dry dentin group" was signifcantly lower than that of all other groups, which showed similar results. A predominance of mixed failures was detected for the control group, while a predominance of adhesive failures was observed for the "bonding agent" and "dry dentin" groups. The "moist dentin" group presented predominantly cohesive failures within the luting material. The previous application of a self-etching adhesive showed no signifcant effect. CONCLUSIONS: Only excess dentin moisture should be removed for the cementation of ceramic restorations with self-adhesive resin cements.

Bonding to wet or dry deproteinized dentin: micro tensile bond strength and confocal laser micromorphology analysis

Aim: To investigate the influence of deproteinization and moisture condition (wet vs. dry) on the bond strength and micromorphology of resin-dentin bonding interfaces. Methods: Dentin surfaces were etched with 37% phosphoric acid for 15 s and rinsed with water. Four groups (n = 10) were tested: WET: dentin was left visibly moist; DRY: dentin was dried with compressed air; WET-D: dentin was deproteinized for 60 s using 10% NaOCl solution and left moist; DRY-D: dentin was deproteinized and dried. Prime&Bond 2.1 adhesive was applied and the teeth were restored with composite resin. Microtensile test was carried out after 24 h, and failure modes classified under magnification. Data were subjected to two-way ANOVAand Tukey’s test (P < 0.05). The bonding micromorphology was analyzed by confocal laser scanning microscopy. Results: The group DRY showed significantly lower bond strength (P < 0.05) than the other groups, which were similar to each other (P > 0.05). Adhesive failures were predominant. Analysis of micromorphology showed formation of a collagen-resin hybrid layer only for the non-deproteinizedgroups. Adhesive penetration into the dentinal tubules was deeper for the DRY-D compared to the WETD group. Conclusion: The bond strength was not dependent on the moisture condition and a more homogeneous hybridization was obtained when dentin was deproteinized.