Remineralizing effect of commercial fluoride varnishes on artificial enamel lesions

Abstract: The aim of this study was to evaluate soluble and insoluble fluoride concentrations in commercial varnishes, and their remineralization effect on artificial caries enamel lesions using surface and cross-sectional microhardness evaluations. Forty bovine enamel blocks were separated into four groups (n=10): control (no treatment), Enamelast (Ultradent Products), Duraphat (Colgate-Palmolive) and Clinpro White Varnish (3M ESPE). Surface enamel microhardness evaluations were obtained, artificial enamel caries lesions were developed by dynamic pH-cycling, and the varnishes were then applied every 6 days, after which the enamel blocks were submitted to dynamic remineralization by pH cycles. After removal of the varnishes, the enamel surfaces were reassessed for microhardness. The blocks were sectioned longitudinally, and cross-sectional microhardness measurements were performed at different surface depths (up to 300 μm depth). Polarized light microscopy images (PLMI) were made to analyze subsurface caries lesions. The fluoride concentration in whole (soluble and insoluble fluoride) and centrifuged (soluble fluoride) varnishes was determined using an extraction method with acetone. The data were analyzed to evaluate the surface microhardness, making adjustments for generalized linear models. There was a significant decrease in enamel surface microhardness after performing all the treatments (p<0.0001). Enamelast and Duraphat showed significantly higher enamel microhardness values than the control and the Clinpro groups (p = 0.0002). Microhardness loss percentage was significantly lower for Enamelast (p = 0.071; One-way ANOVA). PLMI showed that subsurface caries lesions were not remineralized with the varnish treatments. No significant differences in the in-depth microhardness levels (p = 0.7536; ANOVA) were observed among the treatments. Enamelast presented higher soluble and insoluble fluoride concentrations than the other varnishes (p < 0.0001; Kruskal-Wallis and Dunn tests). Enamelast and Duraphat varnishes promoted enamel surface remineralization, but no varnish remineralized the subsurface lesion body. Although insoluble and soluble fluoride concentration values did not correspond to those declared by the manufacturer, Enamelast presented higher fluoride concentration than the others.

Bond strength of different bracket bonding materials to the enamel subjected to thermal cycling / Resistência de união de diferentes materiais de colagem de bráquetes ao esmalte submetidos à ciclagem térmica

OBJECTIVE: The aim of this study was to evaluate in vitro the shear bond strength of metallic orthodontic brackets to enamel using different bonding materials followed by thermal cycling. METHODS: A fluid composite resin (Transbond XT / 3M Unitek) and a resin-modified glass ionomer (Fuji Ortho LC / GC America Inc.) were evaluated. Eighty sound human premolars were randomly divided into eight experimental groups (n = 10), according to the material used and the number of thermal cycles: zero, 1000, 2000 and 3000 cycles. Bracket bonding was performed on the buccal surface of the teeth. After 24 hours, they were subjected to thermal cycling at temperatures ranging between 5° C and 55° C for 15 seconds each immersion. Shear bond strength was performed using a universal testing machine with a chisel-type tip at a speed of 0.5 mm / min. The bond strength data was analyzed using two-way ANOVA. RESULTS: No difference on shear bond strength was observed regarding the number of thermal cycles for each specimen (p = 0.873). A significant difference was found in shear bond strength between the bonding materials (p = 0.022), with significantly higher values for Transbond XT regardless of the number of thermal cycles. CONCLUSION: The number of thermal cycles did not significantly affect the bond strength of the adhesive materials investigated. The bonding agent Transbond XT showed higher bond strength than Fuji Ortho LC regardless of the number of thermal cycles. .

OBJETIVO: Avaliar in vitro a resistência de união por cisalhamento de bráquetes ortodônticos metálicos ao esmalte utilizando diferentes materiais para colagem em função da quantidade de ciclos térmicos. MÉTODOS: Foram avaliados um sistema de união com resina composta fluida (Transbond XT/3M Unitek) e um ionômero de vidro modificado por resina (Fuji Ortho LC/GC America Inc.). Oitenta pré-molares humanos hígidos foram aleatoriamente divididos em oito grupos experimentais (n=10), de acordo com os tipos de material e quantidade de ciclos térmicos: zero, 1000, 2000 e 3000 ciclos. A colagem dos bráquetes foi realizada na face vestibular dos dentes. Após 24 horas, foram submetidos à ciclagem térmica com temperaturas de imersão entre 5ºC e 55ºC por 15 segundos. Os testes de resistência de união foram feitos em máquina de ensaios universal com ponta tipo cinzel com velocidade de 0,5 mm/min. Os dados foram submetidos à ANOVA a dois critérios. RESULTADOS: Não houve diferença na resistência de união entre bráquetes e o esmalte em função do número de ciclos térmicos (p = 0,873). Houve diferença significativa na resistência de união proporcionada entre os materiais para colagem (p = 0,022), sendo que valores significativamente superiores foram obtidos com a utilização do Transbond XT, independentemente do número de ciclos térmicos. CONCLUSÃO: A quantidade de ciclos térmicos não influenciou significativamente a resistência de união dos materiais. Transbond XT mostrou maior resistência de união do que o cimento Fuji Ortho LC, independentemente da quantidade de ciclos térmicos. .

Aplicação de sistemas adesivos nas diferentes profundidades do substrato dentinário: revisão de literatura / Application of adhesive systems on different dentin depths: a literature review

O desenvolvimento dos sistemas adesivos possibilitou maior conservação da estrutura dentária remanescente sadia, sendo essa a conquista mais significativa possibilitada pelo uso desse material. Sabe-se, no entanto, que a maioria dos procedimentos restauradores envolve o substrato dentinário que possui morfologia e fisiologia diferente do esmalte. Essas diferenças acarretaram no desenvolvimento de diversas gerações de adesivos dentinários, incluindo os que removem a smear layer, bem como aqueles que eliminam a etapa do condicionamento ácido da superfície a ser tratada, empregando-se os sistemas autocondicionantes. Esse trabalho teve por objetivo revisar a literatura sobre os sistemas adesivos, enfocando sua aplicabilidade nos diferentes substratos dentários. Foi observado que a variabilidade do substrato dentinário pode influenciar negativamente a adesão à dentina ao se utilizar sistemas adesivos convencionais; o uso de um forrador cavitário contribui para proteção pulpar em cavidades profundas, além de eliminar os problemas decorrentes das falhas de adesão devido à umidade das paredes pulpares e/ou axiais ao se utilizar sistemas adesivos convencionais. A profundidade do substrato dentinário não influencia a resistência de união quando sistemas adesivos autocondicionantes são empregados.

The development of dentin adhesive agents has changed drastically the Dentistry in the last few years, leading to conservative procedures of dental structures. However, most restorative procedures involve dentin bonding that represents a challenge because of the variation of their composition in comparison to enamel. These differences led to the development of a new generation of adhesive systems, and a new concept of bonding has been introduced with the aim of eliminating the step of acid conditioning, arising adhesives self-etching. The objective of this literature review was to analyze the adhesive systems and their relationship with different layer dentin. It was concluded that variability of dentin can negatively influence bonding when using conventional adhesive systems. The use of a cavity liner contributes to the protective pulp in deep cavities, besides eliminating problems arising from bond failures due to moisture from the pulp and/or axial walls when using conventional adhesive systems, the depth of dentin doesn't influence the bond

Resistência de união por push-out e selamento marginal de sistemas adesivos convencionais e autocondicionantes utilizados para cimentação de pinos de vidro intrarradiculares em diferentes profundidades / Push-out bond strength and sealing ability of etch-and-rinse and self-etching adhesives used for fiberglass dowel bonding at different depths of the root canals

O objetivo deste estudo foi avaliar a resistência de união por push-out e o selamento marginal de sistemas adesivos convencionais e autocondicionantes utilizados para cimentação de pinos de vidro intrarradiculares em diferentes profundidades. Noventa raízes de pré-molares humanos (45 para os testes de push-out e 45 para os de microinfiltração) tiveram os canais preparados com profundidades padronizadas e foram aleatoriamente distribuídas em 3 grupos(n = 15) de acordo com o sistema adesivo utilizado: Adper Scotchbond Multi Purpose (3M ESPE); Adper Single Bond 2 (3M ESPE); Clearfil SE Bond (Kuraray). As raízes receberam pino de fibra de vidro com cimento resinoso. Para os testes de push-out, as raízes foram cortadas radialmente em 3 diferentes profundidades para obter cortesseriados de aproximadamente 1 mm de espessura. Uma máquina de ensaios mecânicos (Emic) foi utilizada para os ensaios de push-out. Para os testes de microinfiltração, as raízes foram seladas e imersas em solução de azul de metileno a 2%, pH 7,0 por 2 horas. As raízes foram cortadas radialmente em 3 diferentes profundidades para obter cortes seriados com espessura de 1 mm e a microinfiltração foi avaliada em lupa estereoscópica por 3 examinadores calibrados que atribuíram escores de 0 a 3. A Análise de Variância e o teste de Tukey para os testes de push-out mostraram que não houve diferenças significativas entre os sistemas adesivos (p >0,05), mas houve entre as profundidades, com maiores valores de resistência de união para o terço cervical e apical. Para os ensaios de microinfiltração, os testes de Kruskal-Wallis e de Friedman mostram que não houve diferença significativa entre os adesivos e entre as profundidades (p > 0,05). Os sistemas adesivos convencionais e autocondicionantes apresentaram semelhante resistência de união e de selamento marginal para a cimentação de pinos de fibra de vidro, havendo maior resistência de união nos terços mais cervicais e apicais dos canais.

The aim of this study was to evaluate the push-out bond strength and sealing ability of etch-and-rinse and selfetching adhesives used for fiberglass dowel bonding at different depths of the root canals. Ninety human pre-molar roots (45 for the push-out tests and 45 for the microleakage tests) had their canals prepared with standardized depthsand were randomly allocated into 3 groups (n = 15) according to the adhesive system used: Adper Scotchbond Multi Purpose (3M ESPE); Adper Single Bond 2 (3M ESPE); Clearfil SE Bond (Kuraray). They were restored with fiberglass dowel and resin cement. For the push-out tests, the roots were radially cut at 3 different depths to obtain serial cutswith approximately a thickness of 1 mm. A universal testing machine (Emic) was used for the push-out test. For the microleakage group, roots were sealed, and immersed in a 2% methylene blue solution, pH 7.0, for a 2 hours period. Roots were radially sectioned at 3 different depths to obtain serial cuts with a thickness of approximately 1mm and microleakage was evaluated in stereoscopic loupe by three calibrated evaluators who attributed scores from 0 to 3. The Analysis of Variance and the Tukey test for the push-out tests showed no significant differences among adhesive systems (p > 0.05), but differences among the depths with higher bond strength at the cervical and apical depth.For microleakage, Kruskal-Wallis and Friedman tests showed that there was no significant difference among the adhesive systems tested or different depths of cut (p > 0.05). The total-etching and self-etching adhesive systems had similar bond strength and ability of marginal sealing for the cementation of fiberglass dowels and that higher bond strength was obtained at the most cervical and apical depths of the root canals.