Cytotoxicity evaluation, antibacterial effect, and degree of conversion of QAM-containing adhesives

Abstract The aim of this study was to evaluate the influence of adding quaternary ammonium methacrylates (QAMs) to experimental adhesives by assessing the degree of conversion (DC), cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. Two QAMs were added to an experimental adhesive: dimethylaminododecyl methacrylate bromododecane (DMADDM) or dimethylaminododecyl methacrylate bromohexadecane (DMAHDM) at three concentrations each: 1, 2.5, and 5 wt.%. Experimental adhesive without QAMs (control group) and commercially available Transbond XT Primer (3M Unitek, Monrovia, California, USA) were used for comparisons. The adhesives were tested for DC, cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. DC, cytotoxicity against fibroblasts, and antibacterial activity were analyzed using one-way ANOVA and Tukey's multiple comparisons. Cytotoxicity against keratinocytes was evaluated using the Kruskal Wallis and Dunn's post-hoc (α = 5%) tests. Transbond showed lower DC as compared to 5% DMAHDM, 1% DMADDM, and 5% DMADDM (p < 0.05). However, all groups presented proper DC when compared to commercial adhesives in the literature. In the evaluation of cytotoxicity against keratinocytes, Transbond induced higher viability than 2.5 wt.% groups (p < 0.05). Against fibroblasts, Transbond induced higher viability as compared to 5 wt.% groups (p < 0.05). DMAHDM at 5 wt.% reduced biofilm formation when compared to all the other groups (p < 0.05). Despite their cytotoxic effect against keratinocytes, gingival fibroblasts showed higher viability. DMAHDM at 5 wt.% decreased Streptococcus mutans viability. The incorporation of DMAHDM at 5 wt.% may be a strategy for reducing the development of white spot lesions.

Cost-related variables in the public purchase of dental materials for endodontic application: 10-year analysis

Aim: This study analyzed public procurements for different endodontic materials used in the Brazilian public health system and evaluated the variables related to their cost. Methods: A time-series study was performed by screening materials for endodontic application in the public Brazilian Databank of Healthcare Prices from 2010 to 2019. Data were categorized according to material composition and clinical application. The collated variables were used in a multiple linear regression model to predict the impact of unit price in procurement processes. Results: A total of 5,973 procurement processes (1,524,693 items) were evaluated. Calcium hydroxides were found in 79% of the observations (4,669 processes). Prices drop each year by US$1.87 while MTAs and epoxy resins are increasingly purchased at higher prices (US$50.87; US$67.69, respectively). The microregion, the procurement modality, and the type of institution had no influence on unit prices in the adjusted model (p > 0.05). Conclusions: Calcium hydroxide-based materials were the cheapest and most frequently purchased endodontic materials in the public health care system. Novel formulations are being implemented into clinical practice over time and their cost may be a barrier to the broad application of materials such as MTAs, despite their effectiveness

Impact of economic factors and knowledge translation on public procurement for dental adhesive systems

Abstract: This study aimed to screen the public procurement for dental adhesives in a public health system and evaluate the variables associated with the type and cost of purchased materials. A time series was conducted with secondary data collated from the Brazilian Databank of Healthcare Prices (BDHP). All public procurements for adhesive systems registered from 2010 to 2019 were collated. The frequency of purchase was described, and a multiple linear regression model was used to assess the influence of unit price on predictor variables. Multinomial logistic regression was conducted to describe the influence of selected variables on the probability of purchase for different classes of adhesive systems. A total of 2,752 purchases were analyzed, and the total cost of these materials reached US$ 7,022,659.00 in the 10 analyzed years. The 3-step Etch & Rinse adhesives corresponded to 45.63% of the processes, with increased probability of being purchased over time. The process conducted by public universities in recent years, using the auction modality, presented lower unit prices. The year of purchase, the type of institutions, the institution's location, and the procurement modality influenced the procurement process. The performed analyses contribute to the understanding of the variables associated with the procurements for adhesive systems, providing valuable information for rationalizing public expenditure and for implementing evidence-based practices to guarantee cost-effective and clinically effective procedures for users of the Brazilian public healthcare system.

The influence of the particle's size on the setting reaction of sol-gel derived calcium silicate particles / A influência do tamanho de partícula na reação de presa de cimentos de silicate de cálcio produzidos por sol-gel

Introduction: This study aims to analyze the influence of particles size of sol-gel derived calcium silicate particles in the setting reaction of bioactive endodontic cements. Materials and Methods: Sol-gel derived calcium silicate particles were synthesized and sieved to separate the particles in different sizes: CS400, CS200, and CS100. A commercial MTA (Control) was used as control. The particle size and the specific surface area were assessed by laser diffraction and nitrogen adsorption. The cements were prepared with water as the liquid for the reaction. The setting time was conducted according to ISO 6876, and the setting kinetics was analyzed by Fourier trans-formed infrared spectroscopy (FTIR) at different time points between 120s to 72h. Results: The particle size varied from 9.45µm (CS400 ) to 31.01 (Control). The higher specific surface area valuer reached 15.14g/cm2 in the CS400. The smallest particle sizes, the higher specific surface area, and the lowest setting time were found for CS400 (p < 0.05). Control presented the highest setting time (p < 0.05). The FTIR analyses showed the differences in materials structure over time, with faster hydration and crystallization for CS400. The setting kinetics was slower for Control even when compared to a sol-gel derived group with similar particle size. Conclusion:The route of synthesis and the particle size influences the setting reaction of calcium silicate-based cements. The reduction of particle size for sol-gel derived calcium silicates lead to the acceleration of the setting reaction of the produced bioactive endodontic cement.

Introdução: Este estudo tem como objetivo analisar a influência do tamanho de partículas de silicato de cálcio derivadas de sol-gel na reação de presa de cimentos endodônticos bioativos. Materiais e Métodos: Partículas de silicato de cálcio derivadas de sol-gel foram sintetizadas e peneiradas para separar as partículas em diferentes tamanhos: CS400, CS200 e CS100. Um MTA comercial (Controle) foi usado como controle. O tamanho das partículas e a área superficial específica foram avaliados por difração a laser e adsorção de nitrogênio. Os cimentos foram preparados com água como líquido para a reação. O tempo de presa foi conduzido de acordo com a ISO 6876, e a cinética de presa foi analisada por espectroscopia de infravermelho transformada de Fourier (FTIR) em diferentes pontos de tempo entre 120s a 72h. Resultados: O tamanho de partícula variou entre 9,45µm (CS400) e 31,01 (Controle). A maior área de superfície foi encontrada nas partículas do grupo CS400 (15.14g/cm2). Os menores tamanhos de partícula, a maior área de superfície específica e o menor tempo de presa foram encontrados para CS400 (p < 0,05). O Control apresentou o maior tempo de presa (p < 0,05). As análises de FTIR mostraram as diferenças na estrutura dos materiais ao longo do tempo, com hidratação e cristalização mais rápidas para CS400. A cinética de presa foi mais lenta para Control mesmo quando comparado a um grupo derivado de sol-gel com tamanho de partícula semelhante. Conclusão: A rota de síntese e o tamanho das partículas influenciam a reação de endurecimento dos cimentos à base de silicato de cálcio. A redução do tamanho de partícula para silicatos de cálcio derivados de sol-gel leva à aceleração da reação de pega do cimento endodôntico bioativo produzido.

Physicochemical properties and biological effects of quaternary ammonium methacrylates in an experimental adhesive resin for bonding orthodontic brackets

Abstract Fixed orthodontic appliances may lead to biofilm accumulation around them that may increase caries risk. This study aimed to evaluate the influence of quaternary ammonium methacrylates (QAMs) on the physicochemical properties, cytotoxicity, and antibacterial activity of adhesive resins for orthodontic purposes. Methodology: A base resin was prepared with a comonomer blend and photoinitiator/co-initiator system. Two different QAMs were added to the base adhesive: dimethylaminododecyl methacrylate at 5 wt.% (DMADDM) or dimethylaminohexadecyl methacrylate (DMAHDM) at 10 wt.%. The base adhesive, without QAMs, (GC) and the commercial Transbond™ XT Primer 3M (GT) were used as control. The resins were tested immediately and after six months of aging in the water regarding the antibacterial activity and shear bond strength (SBS). The antibacterial activity was tested against Streptococcus mutans via metabolic activity assay (MTT test). The groups were also tested for the degree of conversion (DC) and cytotoxicity against keratinocytes. Results: The resins containing QAM showed antibacterial activity compared to the commercial material by immediately reducing the metabolic activity by about 60%. However, the antibacterial activity decreased after aging (p<0.05). None of the groups presented any differences for SBS (p>0.05) and DC (p>0.05). The incorporation of DMADDM and DMAHDM significantly reduced the keratinocyte viability compared to the GT and GC groups (p<0.05). Conclusion: Both adhesives with QAMs showed a significant reduction in bacterial metabolic activity, but this effect decreased after water aging. Lower cell viability was observed for the group with the longer alkyl chain-QAM, without significant differences for the bonding ability and degree of conversion. The addition of QAMs in adhesives may affect the keratinocytes viability, and the aging effects maybe decrease the bacterial activity of QAM-doped materials.

Avaliação de soluções antifúngicas de guanidina para resina base de dentadura: um estudo in vitro / Evaluation of guanidine antifungal solutions for denture base resin: an in vitro study

Background: The purposes of this study were: (1) to formulate polyhexamethylene guanidine hydrochloride (PHMGH) solutions at different concentrations; (2) to evaluate their antifungal activity against a mature biofilm of Candida albicans on acrylic resins; (3) to evaluate possible effects on acrylic resins flexural strength and surface roughness. Methods: PHMGH solutions were formulated with distilled water and 0.125, 0.250, or 0.5 wt.% of PHMGH. One group without PHMGH was used as control. For antifungal activity analysis, acrylic resin specimens were contaminated with C. albicans. Specimens were immersed in PHMGH solutions or distilled water for 5 or 10 min. Ultimate flexural strength and surface roughness of acrylic resins were evaluated. Results: All PHMGH solutions at 5 or 10 min showed antifungal activity compared to the control group (p<0.05). The group with 0.5 wt.% of PHMGH showed no countable colonies regardless of the time of contact with the acrylic resins. After 10 min, all PHMGH solutions had antifungal effect without differences from 0.125 to 0.5 wt.% of PHMGH. All groups showed high flexural strength after contact with the solutions compatible with ISO 20795-1:2013 recommendation. The values of surface roughness always remained low, from 0.01 to 0.04 µm for all groups. Conclusion: Within the limitations of this study, it was concluded that the use of a solution composed by distilled water and 0.5 wt.% of PHMGH for 5 min was effective as a disinfectant agent against mature biofilm of C. albicans , maintaining acceptable roughness and flexural strength.

Antecedentes: Os objetivos deste estudo foram: (1) formular soluções de cloridrato de polihexametileno guanidina (PHM-GH) em diferentes concentrações; (2) avaliar sua atividade antifúngica contra biofilme maduro de Candida albicans em resinas acrílicas; (3) avaliar efeitos na resistência à flexão e rugosidade da superfície. Métodos: Soluções de PHMGH foram formuladas com água destilada e 0,125, 0,250 ou 0,5% em peso de PHMGH. Um grupo sem PHMGH foi usado como controle. Para análise da atividade antifúngica, amostras de resina acrílica foram contaminadas com C. albicans, e imersas em soluções de PHMGH ou água destilada por 5 ou 10 min. Resistência à flexão final e rugosidade da superfície foram avaliadas. Resultados: Todas as soluções de PHMGH aos 5 ou 10 minutos apresentaram atividade antifúngica em comparação ao grupo controle (p <0,05). O grupo com 0,5% em peso de PHMGH não mostrou colônias contáveis, independentemente do tempo. Após 10 minutos, todas as soluções de PHMGH tiveram efeito antifúngico sem diferenças de 0,125 a 0,5% em peso de PHM-GH. Os grupos apresentaram alta resistência à flexão após o contato com as soluções compatíveis com a recomendação ISO 20795-1: 2013. Os valores de rugosidade da superfície permaneceram baixos, de 0,01 a 0,04 µm para todos os grupos. Conclusão: Dentro das limitações deste estudo, concluiu-se que o uso de uma solução composta por água destilada e 0,5% em massa de PHMGH por 5 min foi eficaz como agente desinfetante contra o biofilme maduro de C. albicans, mantendo rugosidade e resistência à flexão aceitáveis.

Development of resin-based bioactive endodontic cements with glycerol salicylate and calcium silicate / Desenvolvimento de cimentos endodônticos bioativos à base de resina com salicilato de glicerol e silicato de cálcio

Introduction: The combination of sol-gel derived calcium silicate particles and glycerol salicylate resins may enhance the pyhisico-chemical properties contribute to the unders-tanding of the interaction between these materials. This study aims to evaluate the physical-chemical properties of resin-based bioactive endodontic cements with glycerol salicylate resins and calcium silicate particles. Materials and methods: Calcium silicate was produced by the sol-gel route, while the resin was produced by mixing 60wt% glycerol salicylate, 30wt% methyl salicylate and 10wt% distilled water. Calcium silicate was added in three different concentrations, 50, 40 and 25% by weight. The cement was tested for setting time, flow, radiopacity and pH. Results: The 50:50 group shows the time of 15min8s while the 75:25 shows the time of 256min13s (p < 0.05). The 50:50 group has a lower flow (15.156mm) compared to 60:40 (23.588 mm) and 75:25 (25.396 mm). All radiopacity values were below 3mmAl. All groups showed a pH increase up to 24 hours and the pH value drop was inversely proportional to the amount of calcium silicate. Discussion: Bioactive calcium silicate particles were used in a composite material with a glycerol salicylate resin. Among the tested cements, the combination of 50wt% calcium silicate particles to 50wt% glycerol salicylate resin showed adequate setting time and promoted an increase in water pH. Conclusion: The 50:50 group showed the setting time and the pH, showing that these materials may be able to promote enhanced biological response. The adjustment of flow and radiopacity should be considered for its clinical application.

Introdução: A combinação entre partículas de silicato de cálcio e glycerol salicilato tem potencial para melhorar as propriedades físico-químicas de cimentos endodônticos bioativos. O objetivo deste estudo foi avaliar as propriedades físico-químicas de cimentos resinosos contendo glicerol salicilato e silicatos de cálcio. Materiais e métodos: O silicato de cálcio foi produzido pelo método sol-gel, en-quanto o líquido foi obtido pela mistura de 60% de salicilato de glicerol, 30% de salicilato de metila e 10% de água destilada em peso. O silicato de cálcio foi adicionado em três diferentes concentrações, sendo elas 50, 40 e 25% em peso. O cimento foi testado em relação ao tempo de presa, escoamento, radiopacidade e pH. Resultados: O grupo 50:50 apresentou tempo de presa de 15min8s enquanto o 75:25 apresentou um tempo de 256min13s (p < 0,05). O grupo 50:50 apresentou menor escoamento (15,156mm) em comparação ao 60:40 (23,588mm) e 75:25 (25,396mm). Quanto à radiopacidade, todos obtiveram valores menores que 3mmAl. Todos apresentaram aumento de pH até 24h, e após esse período tiveram quedas inversamente proporcionais a quantidade de silicato de cálcio em cada um. Discussão: Partículas bioativas de silicato de cálcio foram utilizadas em um compósito com base resi-nosa de glicerol salicilato. Dentre os cimentos utilizados, a combinação de 50:50 entre os componentes tem resultados promissores para a aplicação destes materiais. Conclusão: O grupo 50:50 apresentou adequado tempo de presa e pH, indicando que o material pode manter suas propriedades biológicas. A radiopacidade e o escoamento, no entando, devem ser adequadas para aplicação do material.

Brazilian dentistry research productivity: state level socioeconomic, educational and structural factors

Aim: To explore socioeconomic, educational and research factors associated with dental research productivity at the state level in Brazil. Methods: The authors used the Scopus database to identify dental articles published from 2006 to 2016 associated with Brazilian universities at the state level. Several social, economic, educational and research structure variables were obtained from the census and National Research Council to predict the rate of articles per 100 thousand inhabitants among the 27 Brazilian states. Rates were fitted in linear weighted least-squared regression with stepwise technique. Twenty-two variables were grouped in six blocks (social, economic, general education, dental education, research workforce and structure). Results: A total of 21189 articles were published, and the state of São Paulo accounted for 46%, followed by Rio Grande do Sul with 9.4%; four states did not publish any articles. There were an average (± standard deviation) of 2.6 (±1.98) published articles per 100 researchers and 13.4 (±9.6) articles per 100 thousand inhabitants. Research structure and workforce explained 92.4% and 87.2% of state variability, respectively, while the final model explained 94.5%. One extra PhD and one extra undergraduate researcher per 100 thousand inhabitants were associated with 11.3 more and 3.5 fewer articles, respectively, while every 10 points (range 0-100) on the Human Development Index (Education Component) was associated with 3.3 more articles. Conclusion: State scientific output has several associated factors, but research workforce and general education variables seem to be good predictors. Large disparities among state research outputs have been described and must be addressed by research and development policies

Surface and mechanical properties of adhesives with calcium phosphates challenged to different storage media

Aim: To evaluate the behavior of experimental dental adhesives with hydroxyapatite (HAp), alpha-tricalcium phosphate (α-TCP) or octacalcium phosphate (OCP) after storing them in three different media: dry storage, distilled water, or lactic acid. Methods: An experimental adhesive resin was formulated with bisphenol A glycol dimethacrylate, 2-hydroxyethyl methacrylate, and photoiniciator/co-initiator system. HAp(GHAp), α-TCP (Gα-TCP), or OCP (GOCP) were added to the adhesive resin at 2 wt.%, and one group remained without calcium phosphates to be used as a control (GCtrl). The adhesives were evaluated for surface roughness, scanning electron microscopy (SEM), and ultimate tensile strength (UTS) after storing in distilled water (pH=5.8), lactic acid (pH=4) or dry medium. Results: The initial surface roughness was not different among groups (p>0.05). GHAp showed increased values after immersion in water (p<0.05) or lactic acid (p<0.05). SEM analysis showed a surface variation of the filled adhesives, mainly for Gα-TCP and GHAp. GHApshowed the highest UTS in dry medium (p<0.05), and its value decreased after lactic acid storage (p<0.05). Conclusions: The findings of this study showed that HAp, OCP, and α-TCP affected the physical behavior of the experimental adhesive resins in different ways. HAp was the calcium phosphate that most adversely affected the surface roughness and the mechanical property of the material, mainly when exposed to an acid medium

Nanoneedle-like zinc oxide as a filler particle for an experimental adhesive resin

Aim: The aim of this study was to develop an experimental adhesive resin with nanoneedle-like zinc oxide (N-ZnO), an inorganic filler, that could avoid particle agglomeration and lead to a homogeneous stress distribution within the material and characterize it. Materials and Methods: N-ZnO particles obtained by a thermal evaporation technique were characterized regarding size and surface area and added at 0 (control), 1, 2, 5, and 10 wt%, to an experimental adhesive resin. The following experimental adhesive resins' properties were assessed: radiopacity, contact angle to conditioned enamel and dentin, color, degree of conversion, flexural strength, resistance to degradation, and cytotoxicity. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test and paired Student's t-test. Results: Particles presented a mean particle size of 40 nm and a specific surface area of 16 m2/g. N-ZnO10%showed an increased radiopacity when compared to N-ZnO0%. Contact angles were significantly higher for N-ZnO10%at enamel and N-ZnO2%, N-ZnO5%, and N-ZnO10%at dentin. All groups showed color change when compared to N-ZnO0%. Higher the N-ZnO concentration, lower the degree of conversion. There were no significant differences between the groups for flexural strength and resistance to degradation. The addition of N-ZnO showed no difference in cytotoxicity when compared to positive control, N-ZnO0%, and all groups showed higher values than negative control. Conclusions: N-ZnO possibly exceeded potential limitations due to particles' agglomeration and improved the transference and distribution of stress within the material. It could be effectively used as a filler for adhesive resins.

Evaluation of an antibacterial orthodontic adhesive incorporated with niobium-based bioglass: an in situ study

Abstract This in situ study aimed to evaluate the antibacterial and anti-demineralization effects of an experimental orthodontic adhesive containing triazine and niobium phosphate bioglass (TAT) around brackets bonded to enamel surfaces. Sixteen volunteers were selected to use intra-oral devices with six metallic brackets bonded to enamel blocks. The experimental orthodontic adhesives were composed by 75% BisGMA and 25% TEGDMA containing 0% TAT and 20% TAT. Transbond XT adhesive (TXT) was used as a control group. Ten volunteers, mean age of 29 years, were included in the study. The six blocks of each volunteer were detached from the appliance after 7 and 14 days to evaluate mineral loss and bacterial growth including total bacteria, total Streptococci, Streptococci mutans, and Lactobacilli. Statistical analysis was performed using GLM model - univariate analysis of variance for microhardness and 2-way ANOVA for bacterial growth (p<0.05). The 20% TAT adhesive caused no difference between distances from bracket and the sound zone at 10-µm deep after 7 and 14 days. After 14 days, higher mineral loss was shown around brackets at 10- to 30-µm deep for TXT and 0% TAT adhesives compared to 20% TAT. S. mutans growth was inhibited by 20% TAT adhesive at 14 days. Adhesive with 20% TAT showed lower S. mutans and total Streptococci growth than 0% TAT and TXT adhesives. The findings of this study show that the adhesive incorporated by triazine and niobium phosphate bioglass had an anti-demineralization effect while inhibiting S. mutans and total Streptococci growth. The use of this product may inhibit mineral loss of enamel, preventing the formation of white spot lesions.

Antibacterial, chemical and physical properties of sealants with polyhexamethylene guanidine hydrochloride

Abstract The aim of this study was to evaluate the influence of polyhexamethylene guanidine hydrochloride (PHMGH) in the physico-chemical properties and antibacterial activity of an experimental resin sealant. An experimental resin sealant was formulated with 60 wt.% of bisphenol A glycol dimethacrylate and 40 wt.% of triethylene glycol dimethacrylate with a photoinitiator/co-initiator system. PHMGH was added at 0.5 (G0.5%), 1 (G1%), and 2 (G2%) wt.% and one group remained without PHMGH, used as control (GCTRL). The resin sealants were analyzed for degree of conversion (DC), Knoop hardness (KHN), and softening in solvent (ΔKHN), ultimate tensile strength (UTS), contact angle (θ) with water or α-bromonaphthalene, surface free energy (SFE), and antibacterial activity against Streptococcus mutans for biofilm formation and planktonic bacteria. There was no significant difference for DC (p > 0.05). The initial Knoop hardness ranged from 17.30 (±0.50) to 19.50 (± 0.45), with lower value for GCTRL (p < 0.05). All groups presented lower KHN after immersion in solvent (p < 0.05). The ΔKHN ranged from 47.22 (± 4.30) to 57.22 (± 5.42)%, without significant difference (p > 0.05). The UTS ranged from 54.72 (± 11.05) MPa to 60.46 (± 6.50) MPa, with lower value for G2% (p < 0.05). PHMGH groups presented no significant difference compared to GCTRL in θ (p > 0.05). G2% showed no difference in SFE compared to GCTRL (p > 0.05). The groups with PHMGH presented antibacterial activity against biofilm and planktonic bacteria, with higher antibacterial activity for higher PHMGH incorporation (p < 0.05). PHMGH provided antibacterial activity for all resin sealant groups and the addition up to 1 wt.% showed reliable physico-chemical properties, maintaining the caries-protective effect of the resin sealant over time.

Effect of immersion in various disinfectant solutions on the properties of a heat-cured acrylic resin / Efeito da imersão em diferentes soluções desinfetantes nas propriedades de uma resina acrílica de termoativação

ABSTRACT Objective: The aim of the present study was to evaluate the influence, of immersion in different disinfectant solutions, on microhardness and surface roughness of a heat-cured acrylic resin. Methods: Specimens were immersed in distilled water, commercial vinegar for domestic use, sodium hypochlorite and hydrogen peroxide, for 150 hours or 300 hours (n=10). After periods of immersion, Knoop microhardness and surface roughness were evaluated using a microhardness tester and a roughness tester, respectively. The data were analyzed using two-way ANOVA and Holm-Sidak, at a level of significance of 5%. Results: The microhardness values ranged from 16.90 ± 0.33 to 17.80 ± 0.51 and roughness values from 0.05 ± 0.01 to 0.08 ± 0.02. There is no difference in microhardness and roughness between groups and times (p>0.05). Conclusion: Within the limitations of this study, it is possible to conclude that vinegar and hydrogen peroxide, as alternative disinfectant solutions for acrylic resin devices, did not promote deleterious effects on microhardness and polishing of a heat-cured acrylic resin used for the fabrication of prostheses, neither in the medium term nor the long term.

RESUMO Objetivo: Avaliar a influência da imersão em diferentes soluções desinfetantes na microdureza e rugosidade de uma resina acrílica de termoativação. Métodos: Corpos de prova de resina acrílica termopolimerizável foram imersos em água destilada, vinagre comercial de uso doméstico, hipoclorito de sódio e peróxido de hidrogênio, por períodos de 150 h ou 300 h (n=10). A microdureza Knoop e a rugosidade superficial dos corpos de prova foram avaliadas com o uso de microduro?metro e rugosímetro, respectivamente. Os dadosforam analisados com o teste análise de variância a dois critérios e Holm-Sidak, com nível de significância de 5%. Resultados: Osvalores de microdureza variaram de 16,90 ± 0,33 a 17,80 ± 0,51 e a rugosidade, de 0,05 ± 0,01a 0,08 ± 0,02. Não houve diferença nos resultados de microdureza e rugosidade entre os grupos e tempos (p>0.05). Conclusão: Dentro das limitações do estudo, é possível concluir que a utilização de vinagre ou de peróxido de hidrogênio, como alternativas para a desinfecção de resina acrílica, não provocam efeitos deletérios na dureza e no polimento da resina acrílica termoativada utilizada para confecção de próteses, nem a médio nem a longo prazo.

Performance of progressive and constant tapered instruments rotary systems at canal preparation / Desempenho de sistemas endodônticos rotatórios constante e progressivo no preparo do canal radicular

ABSTRACT Objective: The aim of this study was to compare the performance of two nickel-titanium rotary systems regarding the preparation time, final shape of canal, incidence of aberration, transportation, and fracture of instrument. Methods: A total of 40 simulated canals in resin blocks with 30o curves and a length of 17 mm were divided randomly into two groups: preparation with ProTaper and BioRaCe systems up to F5 and BR5 respectively. Pre- and post-operative canal images were taken and superimposed in order to identify aberrations, transportation, and to take measurements of the canal width. In addition, the preparation time and instrument fractures were recorded. The data were analyzed using Student's t test. Results: There is no difference (p>.05) comparing the systems regarding preparation time, canal aberration, and instrument fracture rates. The progressive tapered instruments of ProTaper prepared significantly larger canal widths in the apical third (p<.05). Conclusion: Overall, both systems provided safe canal preparation, associated with few canal aberrations and instrument fractures.

RESUMO Objetivo: Comparar o desempenho de dois sistemas rotatórios em relação ao tempo de preparo, formato final e alterações do canal, desvio e fratura de instrumento. Métodos: Um total de 40 canais simulados em blocos de resina com curvatura de 30o e comprimento de 17 mm foram divididos randomicamente nos sistemas ProTaper e BioRaCe preparados até F5 e BR5 respectivamente. Imagens pré e após o preparo dos canais foram obtidas e superpostas para identificação de alterações de forma, desvios e largura. O tempo de preparo e fratura de instrumentos também foram avaliados. Os dados foram analisados por teste t de Student. Resultados: O tempo de preparo, alterações de forma e taxa de fratura de instrumentos não teve diferença entre os dois sistemas avaliados (p>0,05). Os instrumentos progressivos do ProTaper resultou em canais significativamente mais largos no terço apical (p<0,05). Conclusão: Os dois sistemas rotatórios avaliados resultaram em preparo endodôntico seguro, com poucas alterações e fratura de instrumento.

Effect on adhesion of a nanocapsules-loaded adhesive system

Abstract This study aimed to evaluate the in situ degree of conversion, contact angle, and immediate and long-term bond strengths of a commercial primer and an experimental adhesive containing indomethacin- and triclosan-loaded nanocapsules (NCs). The indomethacin- and triclosan-loaded NCs, which promote anti-inflammatory and antibacterial effects through controlled release, were incorporated into the primer at a concentration of 2% and in the adhesive at concentrations of 1, 2, 5, and 10%. The in situ degree of conversion (DC, n=3) was evaluated by micro-Raman spectroscopy. The contact angle of the primer and adhesive on the dentin surface (n = 3) was determined by an optical tensiometer. For the microtensile bond strength µTBS test (12 teeth per group), stick-shaped specimens were tested under tensile stress immediately after preparation and after storage in water for 1 year. The data were analyzed using two-way ANOVA, three-way ANOVA and Tukey's post hoc tests with α=0.05. The use of the NC-loaded adhesive resulted in a higher in situ degree of conversion. The DC values varied from 75.07 ± 8.83% to 96.18 ± 0.87%. The use of NCs in only the adhesive up to a concentration of 5% had no influence on the bond strength. The contact angle of the primer remained the same with and without NCs. The use of both the primer and adhesive with NCs (for all concentrations) resulted in a higher contact angle of the adhesive. The longitudinal μTBS was inversely proportional to the concentration of NCs in the adhesive system, exhibiting decreasing values for the groups with primer containing NCs and adhesives with increasing concentrations of NCs. Adhesives containing up to 5% of nanocapsules and primer with no NCs maintained the in situ degree of conversion, contact angle, and immediate and long-term bond strengths. Therefore, the NC-loaded adhesive can be an alternative method for combining the bond performance and therapeutic effects. The use of an adhesive with up to 5% nanocapsules containing indomethacin and triclosan and a primer with no nanocapsules maintained the long-term bond performance.

Effect of beverages on surface properties of resin-based sealants

Aim: The aim of this study was to determine degree of conversion of resin-based sealants and the effect of beverages on surface roughness and color change of materials. Methods: Two commercial resin-based sealants were evaluated (Defense Chroma® and BioSeal®). Degree of conversion (DC) was initially measured using Fourier-transformed infrared (FTIR). Specimens of each sealant were maintained in distilled water and immersed one hour daily in grape juice and cola drink for 30 days. One group was maintained only in distilled water, as a control. Surface roughness and color change were measured before immersion, after seven days of immersion and after 30 days of immersion. Results were analyzed using t-test, paired t-test, one-way repeated measures ANOVA, one-way ANOVA and post-hoc tests (0.05 level of significance). Results: There was no significant difference regarding degree of conversion and initial surface roughness comparing both commercial sealants. Surface roughness increased for BioSeal® immersed in cola drink for 30 days. After 30 days, all groups presented significant color change. Conclusions: The effect of beverages on color stability and surface roughness of resin-based sealants depended on exposure time and kind of beverage (AU)

Triazine Compound as Copolymerized Antibacterial Agent in Adhesive Resins

Abstract The aim of this study was to formulate and evaluate an experimental adhesive resin with the addition of 1,3,5-triacryloylhexahydro-1,3,5-triazine at different concentrations. Experimental adhesive resins were obtained by mixing 50% wt bisphenol A glycol dimethacrylate (BisGMA), 25% wt triethylene glycol dimethacrylate (TEGDMA), 25% wt 2-hydroxyethyl methacrylate (HEMA) and photoinitiator system. The triazine compound was added in 1, 2.5 and 5% wt to a base adhesive resin and one group remained with no triazine as control group. The experimental adhesive resins were analyzed for antibacterial activity (n=3), degree of conversion (n=3) and softening in solvent (n=3). Data distribution was evaluated by Kolmogorov-Smirnov test, paired t test, one-way ANOVA and Tukey’s with a 0.05 level of significance. All groups with added triazine compound showed antibacterial activity against Streptococcus mutans (p<0.05). All groups achieved more than 70% degree of conversion, but there was no difference in this chemical property (p>0.05). The initial Knoop hardness was higher in 2.5 and 5% wt groups (p<0.05) and both groups present lower percentage variation of Knoop hardness after solvent degradation. The present study formulated an antibacterial adhesive resin with a non-releasing agent able to copolymerize with the comonomeric blend, improving the restorative material’s properties.

Resumo O objetivo desse estudo foi desenvolver e avaliar a adição de 1,3,5-triacryloylhexahydro-1,3,5-triazine a uma resina adesiva experimental em diferentes concentrações. Resinas adesivas experimentais foram obtidas a partir da mistura de 50% em peso de bisphenol A glycol dimethacrylate (BisGMA), 25% em peso de triethylene glycol dimethacrylate (TEGDMA), 25% em peso de hidroxietil metacrilato (HEMA) e sistema fotoiniciador. O composto de triazina foi adicionado em proporções de 1; 2,5 e 5% em peso a resina adesiva base e um grupo permaneceu sem a adição do composto de triazina como grupo controle. As resinas adesivas experimentais foram analisadas por atividade antibacteriana (n=3), grau de conversão (n=3) e degradação em solvente (n=3). A distribuição dos dados foi avaliada por teste de Kolmogorov-Smirnov, teste t pareado, ANOVA de uma via e Tukey, considerando nível de significância de 5%. Todos os grupos com adição de composto de triazina demonstraram atividade antibacteriana contra Streptococcus mutans (p<0,05). Todos os grupos atingiram mais de 70% de grau de conversão, mas não houve diferença estatística para essa propriedade química (p>0,05). A dureza Knoop inicial foi maior para os grupos com 2,5 e 5% de triazina (p<0,05) e ambos os grupos apresentaram menor variação percentual de dureza Knoop após degradação em solvente. No presente estudo, foi produzida uma resina adesiva antibacteriana com agente sem liberação para o meio, capaz de copolimerizar com a blenda comonomérica, melhorando as propriedades do material restaurador.

Influence of dye and nylon fibers on microwave-cured acrylic resin properties / Influência de corante e fibras de nylon nas propriedades de uma resina acrílica polimerizada por micro-ondas

ABSTRACT Objective: The aim of this study is to analyze if both color and nylon fibers have an influence on microwave-cured acrylic resin properties. Methods: Rectangular and disk-shaped specimens were prepared using acrylic resins; medium pink with and without nylon fibers and colorless without nylon fibers. To obtain the rectangular specimens, a stainless steel die was used with the following dimensions: 64 X 10 x 3 mm (± 0.5mm). To obtain disk-shaped specimens, a die 50mm (±0.5mm) in diameter and 0.5mm (±0.05mm) thick was employed. They were randomized to form groups: control (colorless acrylic) and experimental (medium pink, with and without nylon fibers), with each group consisting of ten (10) specimens rectangular in shape and five (5) disk-shaped. They were analyzed in six (6) assays (izod impact strength, n=10; Knoop hardness, n=10; glass transition temperature, n=3; water sorption and solubility, n=5; degree of monomer/polymer conversion, n=1; flexural strength and flexural modulus, n=10). All variables were subjected to the analysis of variance test followed by Tukey's multiple comparison test, at a 5% level of significance. Results: The analysis of the monomer/polymer degree of conversion did not reveal any difference between the three groups of resins (medium pink, with and without nylon fibers and colorless resin); it was approximately 88%. The results did not show significant differences between the groups for each variable (p>0.05). Conclusion: The results showed that color and presence of nylon fibers in acrylic resins did not affect the properties analyzed in this study.

RESUMO Objetivo: Analisar se corantes e fibras de nylon influenciam nas propriedades de uma resina acrílica ativada por energia de micro-ondas. Métodos: Espécimes retangulares e em forma de disco foram confeccionados em resina acrílica rosa médio com e sem fibras de nylon e incolor sem fibras. Para obter os espécimes retangulares, foi utilizada uma matriz de aço inoxidável com as seguintes dimensões: 64 X 10 X 3 (± 0,5mm) e para obter os espécimes em forma de disco, foi utilizada uma matriz com 50mm (± 0,5mm) de diâmetro e 0,5mm (±0,05mm) de espessura. Os mesmos foram randomizados para formar os grupos controle (acrílico incolor sem fibras) e experimentais (rosa médio com e sem fibras), sendo cada grupo composto por dez (10) espécimes retangulares e cinco (5) em forma de disco. Foram os mesmos então submetidos a seis (6) ensaios (resistência ao impacto izod, n=10; dureza knoop, n=10; temperatura de transição vítrea, n=3; sorção e solubilidade, n=5; grau de conversão, n=1; resistência à flexão e módulo de flexão, n=10). Todas as variáveis foram submetidas à análise de variância seguida pelo teste de comparações múltiplas de Tukey, com nível de significância de 5%. Resultados: O grau de conversão foi de 88% para os 3 grupos de resinas e os resultados não mostraram diferença estatisticamente significativa entre os mesmos para cada variável (p>0,05). Conclusão: Os resultados mostraram que o corante e a presença de fibras de nylon em resina acrílica não afetaram as propriedades analisadas nesse estudo.

Influence of addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride to an experimental adhesive

Abstract The aim of this study was to develop an experimental adhesive with addition of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (METAC) and to evaluate its mechanical and biological properties and its in vitro antibacterial activity. An experimental adhesive resin was formulated with Bis-GMA, TEGDMA, and HEMA. The antibacterial monomer was added at concentrations of 1%, 2.5%, and 5% (METAC groups). A group without METAC addition was used as control. The experimental adhesives were evaluated as to their antibacterial potential against Streptococcus mutans, degree of conversion, and softening in ethanol for 2 hours. The data were analyzed by one-way ANOVA, Tukey’s post-hoc test, and the paired Student’s t-test (significance level of 0.05). METAC showed antibacterial activity against S. mutans at all concentrations (p < 0.05). There was no statistical difference across METAC groups (p > 0.05). The 1%, 2.5%, and 5% groups yielded the highest mean values for degree of conversion (p < 0.05). The 1% group did not differ from the control group (p > 0.05). There was no statistical difference in baseline microhardness values (p > 0.05) and microhardness values after immersion in ethanol were lower than at baseline for all groups (p < 0.05). There was no statistical difference in the reduction of Knoop hardness number (KHN) after immersion in ethanol for any of the groups (p > 0.05). The results of the present study indicate that METAC is a promising antibacterial agent when added to an adhesive system.