Influence of customization and light-curing device on the bond strength of glass fiber posts - in vitro study / Influência da reanatomização e do aparelho fotopolimerizador na resistência de união de pinos de fibra de vidro - estudo in vitro

Introduction: Endodontically treated teeth are usually affected by extensive structure loss requiring the use of intraradicular posts to provide retention and restoration. Objective: An in vitro assessment was performed on the bonding of glass fiber posts to the root dentin. Material and method: Ninety (n = 10) single bovine roots were used in a 3 x 3 x 3 factorial study with subdivided plots: post customization varying the presence and type of resin (without customization, conventional resin, and Bulk Fill resin), light-curing device (Valo, Radii-Cal, Rainbow), and root third (cervical, middle, and apical). Result: For the customization factor, Tukey's test (5%) showed the superiority of the Bulk Fill (8.16 MPa) and Z350 (7.40 MPa) groups compared to the control group (4.92 MPa), without differing from each other. All light-curing devices differed, showing the superiority of Valo (9.36 MPa), Radii (6.96 MPa) as an intermediate, and the inferiority of Rainbow (4.17 MPa). The cervical root third (7.81 MPa) was superior, the apical third was inferior (5.80 MPa), and the middle third (6.88 MPa) was an intermediate without differing from the others. Conclusion: The customization of glass fiber posts increases the bond strength to the root dentin, regardless of the resin used. There was a compromise in the apical third and when using light-curing devices with lower light intensity.

Introdução: Dentes com extensa perda de estrutura podem comprometer a retenção das restaurações ao remanescente dental, onde pinos intraradiculares são indicados. Objetivo: Avaliou-se in vitro a união de pinos de fibra de vidro à dentina radicular em função de diferentes modos de reanatomização, fotopolimerizadores e regionalização radicular. Material e método: Noventa (n=10) raízes bovinas uniradiculares foram usadas num estudo fatorial 3 x 3 x 3 com parcelas subdivididas: Reanatomização do pino, variando a presença e tipo de resina (Sem reanatomização, Resina Convencional e Resina Bulkfill); Fotopolimerizador (Valo, Radii-cal, Rainbow); e Terço radicular (cervical, médio e apical). Resultado: O teste de Tukey (5%) evidenciou para o Fator Reanatomização superioridade dos grupos BulkFill (8.16MPa) e Z350 (7.40MPa) ao grupo Controle (4.92MPa), sem diferirem entre si. Todos os fotopolimerizadores diferiram entre si, com superioridade de Valo (9.36MPa), Radii (6.96MPa) intermediário, e inferioridade de Raiwbow (4.17MPa). O terço radicular cervical (7.81MPa) foi superior e o apical inferior (5.80MPa), com o terço médio (6.88MPa) intermediário e sem diferir dos demais. Conclusão: Conclui-se que a reanatomização de pinos de fibra de vidro aumenta a resistência de união à dentina radicular, independentemente da resina utilizada, havendo prejuízo no terço apical e quando são empregados fotopolimerizadores com menor intensidade luminosa.

Effect of ceramic thicknesses and opacities on water sorption and solubility of a light-curing resin cement by different units

Aim: This study evaluated the water sorption and solubility of a light-cured resin cement, under four thicknesses and four opacities of a lithium disilicate ceramic, also considering three light-emitting diode (LED) units. Methods: A total of 288 specimens of a resin cement (AllCem Veneer Trans ­ FGM) were prepared, 96 samples were light-cured by each of the three light curing units (Valo ­ Ultradent / Radii-Cal ­ SDI / Bluephase II ­ Ivoclar Vivadent), divided into 16 experimental conditions, according to the opacities of the ceramic: High Opacity (HO), Medium Opacity (MO), Low Translucency (LT), High Translucency (HT), and thicknesses (0.3, 0.8, 1.5, and 2.0 mm) (n = 6). The specimens were weighed at three different times: Mass M1 (after making the specimens), M2 (after 7 days of storage in water), and M3 (after dissection cycle), for calculating water sorption and solubility. Results: The higher thickness of the ceramic (2.0 mm) significantly increased the values of water sorption (44.0± 4.0) and solubility (7.8±0.6), compared to lower thicknesses. Also, the ceramic of higher opacity (HO) generated the highest values of sorption and solubility when compared to the other opacities, regardless of the thickness tested (ANOVA-3 factors / Tukey's test, α = 0.05). There was no influence of light curing units. Conclusion: Higher thicknesses and opacities of the ceramic increased the water sorption and solubility of the tested light-cured resin cement

Polywave And Monowave Light-Curing Units Effects On Polymerization Efficiency Of Different Photoinitiators / Efeito Da Unidade De Cura Por Luz Polywave E Monowave Na Eficiência De Polimerização De Diferentes Fotoiniciadores

Objective: The objective of this study was to characterize and correlate the absorption spectra of three photoinitiators [camphorquinone (CQ), diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) and phenylbis (2,4,6-trimethylbenzoyl)-phosphine oxide (BAPO)], using second or third-generation light curing units (LCU), and to evaluate the degree of conversion and the physical properties of an experimental resin adhesive. Material and methods: Second-generation (Radii-cal® and Emitter D®) and third-generation (Valo® Cordless and Bluephase N®) LCU were assessed regarding spectrum and irradiance rate of emitted light. Also, the photoinitiators (CQ, TPO and BAPO) were characterized by a light absorption spectrum assessed by UV-Vis spectroscopy, degree of conversion and yellowing effect. Statistical analyzes considered two-way ANOVA and post-hoc Tukey test. Results: BAPO presented higher reactivity compared to TPO. Regarding degree of conversion of the photoinitiators activated by different light-curing units, the Emitter D® device promoted a high degree of conversion. BAPO presented the highest yellowing effect values. Conclusions: The emission and absorption characteristics of the photoinitiators were different. The polymerization reaction activated by the second-generation light-curing unit was reduced when using an experimental resin with photoinitiator TPO, and the third-generation light-curing unit showed a higher polymerization potential regardless of the photoinitiator. (AU)

Objetivo: Caracterizar e correlacionar os espectros de absorção de três fotoiniciadores [canforoquinona (CQ), difenil 2,4,6-trimetilbenzil óxido de fosfina (TPO) e óxido de di (2,4,6-trimetilbenzil) difenil fosfina (BAPO)], com unidades de fotoativação (LCU) de segunda ou terceira geração, e avaliar o grau de conversão e as propriedades físicas de um adesivo experimental. Material e métodos: LCU de segunda geração (Radii-cal® e Emitter D®) e terceira geração (Valo® Cordless e Bluephase N®) foram avaliadas quanto ao espectro e taxa de irradiância da luz emitida. Além disso, os fotoiniciadores (CQ, TPO e BAPO) foram caracterizados por um espectro de absorção de luz avaliado por espectroscopia UV-Vis, avaliado o grau de conversão dos adesivos e efeito de amarelamento. A análise estatística empregada foi ANOVA duas vias e teste post-hoc de Tukey. Resultados: BAPO apresentou maior reatividade comparado ao TPO. Em relação ao grau de conversão dos fotoiniciadores ativados por diferentes aparelhos fotopolimerizadores, o dispositivo Emitter D® promoveu um alto grau de conversão. BAPO apresentou os maiores valores de efeito de amarelamento. Conclusões: As características de emissão e absorção dos fotoiniciadores foram diferentes. A reação de polimerização ativada pelas unidades de fotopolimerização de segunda geração foi reduzida com o uso de uma resina experimental com fotoiniciador TPO. As unidades de fotopolimerização de terceira geração apresentaram maior potencial de polimerização independentemente do fotoiniciador. (AU)

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.

Ultimate tensile strength of total and self-etch adhesives: effect of light irradiation distance

Objective: To evaluate the ultimate tensile strength (UTS) of total and self- etch adhesives irradiated at different distances. Materials and Methods: Sixty cylindrical specimens of 0.78mm diameter and 10 mm length were prepared of two types of adhesive systems total etch Excite DSC (EX ­ Ivoclar Vivadent, Schaan, Liechtenstein) and one-step self-etch Clearfil S3 Bond (S3, Kuraray Medical Inc., Tokyo, Japan). Specimens of each adhesive were divided into three groups according to the light irradiation distance (0, 2, 4mm) (n=10). Each specimen was attached to universal testing machine (Digital Force Gauge, IMADA CO., LTD, Japan) and loaded at cross head speed of 1mm/min until failure. Data were analyzed using two-way ANOVA and Independent Student t-test at p< 0.05. Results: Mean UTS for total etch (24.63, 18.19, 17.26 Mpa) and for self-etch (12.68, 8.53, 7.58Mpa) at (0, 2, 4mm) distances. Specimens irradiated directly show significantly the highest UTS while those irradiated at 4mm show the lowest values (p<0.05). Excite DSC total etch adhesive have higher UTS than Clearfil S3 self-etch adhesive regardless of irradiation distance (p<0.05).Conclusions: The UTS of the evaluated adhesives was light irradiation distance and adhesive system dependant.

Bond strength and marginal microleakage in restorations photopolymerized with LED and halogen light associated with three application modes of a universal adhesive system: in vitro study / Resistência de união e da microinfiltração marginal em restaurações fotopolimerizadas com LED e luz halógena associadas a três modos de aplicação de um sistema adesivo universal: estudo in vitro

ABSTRACT Objective: This study aimed to assess the bond strength and marginal microleakage in composite resin restorations, using the Single Bond Universal adhesive system associated with Ultralux (halogen) and Bluephase (LED) light curing units. Methods: For bond strength, 80 healthy human third molars were divided into halogen light (n=40) and LED (n=40), and subdivided according to the following application techniques for the adhesive system: etch-and-rinse (enamel), self-etching (enamel), etch-and-rinse (dentin), and self-etching (dentin). The teeth were subjected to the microtensile test and the fracture pattern was observed under an optical microscope at 40X magnification; they were analyzed by ANOVA, and Fisher and Tukey's tests (5%). For the marginal microleakage test, 120 class II cavities were prepared in 60 healthy human third molars that were randomly divided into halogen light (n=30) and LED (n=30), and subdivided according to the following application techniques for the adhesive system: etch-and-rinse, selective etching, and self-etching. The teeth were thermocycled 2000 times (±5/55°C), stained in 5% basic fuchsin and sectioned for qualitative and quantitative assessments; they were analyzed by Kruskall-Wallis and Dunn tests (5%). Results: For the bond strength of enamel and dentin, the adhesive application with prior acid etching was better than self-etching (p<0.0001), regardless of the type of light curing unit (p<0.05). Etch-and-rinse showed the lowest microleakage values (p<0.0001). Conclusion: Etch-and-rinse obtained the best results relative to the other application techniques for the adhesive system in both tests, regardless of the type of light curing unit.

RESUMO Objetivo: Avaliar a resistência de união e microinfiltração marginal em restaurações de resina composta, utilizando sistema adesivo Single Bond Universal associado com fotoativadores Ultralux (halógeno) e Bluephase (LED). Métodos: Para resistência de união, oitenta terceiros molares humanos hígidos foram divididos: Halógena (n=40); LED (n=40), sendo subdivididos de acordo com a técnica de aplicação do sistema adesivo: condicionamento total-esmalte; autocondicionante-esmalte; condicionamento total-dentina; autocondicionante-dentina. Os dentes foram submetidos ao teste de microtração e o padrão de fratura foi observado em microscópio ótico - 40X de aumento, analisadas pelos testes ANOVA, Tukey e Fisher (5%). Para o ensaio de microinfiltração marginal, 120 cavidades classe II foram preparadas em sessenta terceiros molares humanos hígidos, aleatoriamente divididos: Halógena (n=30); LED (n=30) e subdivididos de acordo com a técnica de aplicação do sistema adesivo: condicionamento total; condicionamento seletivo; autocondicionante. Os dentes foram termociclados 2000 vezes (±5/55ºC), corados em fucsina básica 5% e seccionados para avaliações qualitativa e quantitativa, analisados pelos testes Kruskall-Wallis e Dunn (5%). Resultados: Para resistência de união em esmalte e dentina, a aplicação do adesivo com condicionamento ácido prévio, foi melhor que o autocondicionante (p<0.0001), independentemente do tipo de fotoativador utilizado (p<0.05). O condicionamento total mostrou os menores valores de microinfiltração, (p<0.0001). Conclusão: O condicionamento total, obteve os melhores resultados em relação às outras técnicas de aplicação do sistema adesivo em ambos os testes, independentemente do tipo de aparelho fotoativador.

Minimization of polymerization shrinkage effects on composite resins by the control of irradiance during the photoactivation process

Abstract High levels of shrinkage stress caused by volumetric variations during the activation process are one of the main problems in the practical application of composite resins. Objective The aim of this study is to reduce the shrinkage stress and minimize the effects caused by composite resin volumetric variation due to the photopolymerization. In this way, this work proposes a systematic study to determine the optimal dimming function to be applied to light curing processes. Material and Methods The study was performed by applying mathematical techniques to the optimization of nonlinear objective functions. The effectiveness of the dimming function was evaluated by monitoring the polymerization shrinkage stress during the curing process of five brands/models of composites. This monitoring was performed on a universal testing machine using two steel bases coupled in the arms of the machine where the resin was inserted and polymerized. The quality of the composites cured by the proposed method was analyzed and compared with the conventional photoactivation method by experiments to determine their degree of conversion (DC). Absorbance measurements were performed using Fourier-transform infrared spectroscopy (FT-IR). A T-test was performed on DC results to compare the photoactivation techniques. We also used scanning electron microscopy (SEM) to analyze in-vitro the adhesion interface of the resin in human teeth. Results Our results showed that the use of the optimal dimming function, named as exponential, resulted in the significant reduction of the shrinkage stress (~36.88% ±6.56 when compared with the conventional method) without affecting the DC (t=0.86, p-value=0.44). The SEM analyses show that the proposed process can minimize or even eliminate adhesion failures between the tooth and the resin in dental restorations. Conclusion The results from this study can promote the improvement of the composite resin light curing process by the minimization of polymerization shrinkage effects, given an operational standardization of the photoactivation process.

Optimizing light-cured composite through variations in camphorquinone and butylhydroxytoluene concentrations

Abstract The use of a free-radical polymerization inhibitor, butylhydroxytoluene (BHT), and a common photo-initiator, camphorquinone (CQ), to reduce polymerization stress in dental composite was investigated in this study. Samples were prepared by mixing Bis-GMA, UDMA, and TEGDMA at a 1:1:1 ratio (wt%), and silanized borosilicate glass fillers at 70 wt% were added to form the composite. Sixteen groups of resin composite were prepared using combinations of four CQ (0.1%, 0.5%, 1.0%, and 1.5%) and four BHT (0.0%, 0.5%, 1.0%, and 1.5%) concentrations. For each group, six properties were tested, including flexural strength (FS), flexural modulus (FM), degree of conversion (DC), contraction stress (CS), stress rate, and gel point (GP). The effects of CQ and BHT combinations on each of these properties were evaluated using two-way analysis of variance (ANOVA) and Fisher's Protected Least Significant Differences test at the 5% significance level. Groups with low CQ and BHT showed moderate values for FS, FM, and CS with a 70% DC. Increasing the BHT concentration caused a decrease in CS and DC with an increase in GP values. Increasing the CQ content led to a steady increase in values for FS and FM. High CQ and BHT combinations showed the most promising values for mechanical properties with low stress values.

Long-term bond strength, degree of conversion and resistance to degradation of a HEMA-free model adhesive

Aim: To evaluate the long-term bond strength, degree of conversion and resistance to degradation in ethanol of HEMA-containing and HEMA-free model adhesive resins of a three-step etch-and-rinse adhesive system. Methods: The superficial dentin of 16 bovine incisor teeth was exposed, and the teeth were divided in two groups according to the HEMA concentration in the experimental adhesive (0% and 15%). In each tooth were made 6 cylindrical composite restorations. Half of the tooth restorations were submitted to microshear bond strength test after 24 h and the other half after 6 months. Degree of conversion of experimental resins was determined by Fourier transform infrared spectroscopy. Crosslink density was indirectly determined by the Knoop hardness of five specimens per group before and after immersion in ethanol for 6 h. Results: The group with 0% HEMA showed no difference in bond strength as compared to the group with 15% HEMA after 24 h or 6 months. There was no difference in degree of conversion and crosslink density between groups. Conclusions: HEMA content of the adhesive resin did not influence the bond strength to dentin, degree of conversion or resistance to degradation in ethanol.

Prototype of a new tip developed to be coupled to dental light-curing units for optimizing bonding of orthodontic brackets and accessories

OBJECTIVE: development of a new device to be coupled to light-curing units for bonding orthodontic brackets and accessories, and test its efficacy in an in vitro mechanical trial. The inner surface of the device is mirrored and is based on physical concepts of light refraction and reflection. The main advantage of such device is the reduced clinical time needed for bonding and the low possibility of contamination during the process. METHODS: One hundred and twenty specimens were used for testing the shear bond strength of brackets bonded with the device. The Adhesive Remnant Index (ARI) was also determined. The sample was divided into 2 groups. In group 1 a halogen light-curing unit was used while in group 2 a led light-curing unit was used. Each group was then subdivided. In subgroups H1 and L1, a conventional light guide rod was used while in subgroups H2 and L2 bonding was performed with the mirrored device coupled to the tip of the guide light rod. RESULTS: The values obtained for the shear bond strength and the ARI in the subgroups were compared. Results showed that there was no statistically significant difference for the shear strength (p > 0.05) and the ARI (p > 0.05) between the subgroups. CONCLUSION: The tests of mechanical trials and the ARI analysis showed that the new device fulfilled the requirements for bonding orthodontic accessories, and that the time for bonding was reduced to half, being necessary only one light exposure.

OBJETIVO: desenvolver uma nova ponteira para ser acoplada aos aparelhos fotopolimerizadores utilizados para colagem de braquetes e acessórios ortodônticos, e testar sua da efetividade em ensaio mecânico in vitro. A ponteira é espelhada na superfície interna e baseia-se em conceitos físicos de refração e reflexão de luz. Apresenta como principal vantagem o menor tempo clínico durante o procedimento de colagem, reduzindo a possibilidade de contaminação durante o processo. MÉTODOS: por meio de ensaio de resistência ao cisalhamento e determinação do índice remanescente de adesivo (IRA), testou-se a ponteira desenvolvida em 120 corpos de prova. A amostra foi dividia em dois grupos. No grupo 1, foi utilizado aparelho fotopolimerizador de fonte de luz halógena e, no grupo 2, fonte de LED. Cada grupo foi subdividido. Nos subgrupos H1 e L1, utilizou-se a ponteira convencional. Nos subgrupos H2 e L2 a colagem foi feita utilizando a ponteira desenvolvida para a polimerização do material de colagem. RESULTADOS: os valores dos testes de cisalhamento e IRA para os subgrupos foram comparados entre si. Os resultados mostraram que não houve diferença estatisticamente significativa para o ensaio de resistência ao cisalhamento (p > 0,05) nem para o IRA (p > 0,05) entre os subgrupos. CONCLUSÃO: os testes de ensaio mecânico, assim como a análise do IRA, mostraram que a nova ponteira desenvolvida cumpriu os requisitos necessários à colagem dos acessórios ortodônticos, e que o tempo de colagem foi reduzido pela metade, sendo necessária uma só incidência.

Eficácia do clareamento dentário em superfícies submetidas á colagem ortodôntica de brackets sob diferentes protocolos / Effectiveness of tooth bleaching of surfaces subjected to orthodontic brackets bonding under different protocols

Objetivo: Avaliamos in vitro as variações da sensação de cor (∆E) e suas correlações após o clareamento de dentes submetidos à colagem e remoção de brackets ortodônticos, considerando: 1) o tempo de condicionamento ácido (15, 30 e 60 segundos); 2) os sistemas adesivos (TransbondTMXT, Opal Seal/Bond e TransbondTM Plus SEP) e 3) o momento em que o clareamento foi realizado em relação à presença de brackets (antes, durante ou depois), bem como o índice de adesivo remanescente (IAR) após descolagem dos brackets. Materiais e Métodos: Este trabalho foi subdividido em três artigos para abordar cada um dos objetivos propostos. A amostra foi composta de 270 pré-molares humanos, distribuídos aleatoriamente em 9 grupos: controle negativo (reprodutibilidade); controle positivo (apenas clareamento dentário); e 7 grupos experimentais. A determinação da cor dentária foi obtida pelo sistema CIELab, a partir de dados do espectrofotômetro, em avaliações da cor prévia ao clareamento e em 1, 15 e 30 dias após. Para verificar se existia diferença entre os grupos foi aplicada ANOVA a um fator, uma vez que o tamanho da amostra de cada grupo foi de n=30 (p < 0,05). E quando ANOVA indicou diferença, para identificar quais grupos diferiam entre si, foi aplicado o teste de comparações múltiplas de Tukey para variâncias homogêneas, identificadas pelo teste de Levene (p < 0,05). Resultados: O ∆E desde o préclareamento até 15 e 30 dias após foi estatisticamente diferente entre: o controle e o grupo com condicionamento ácido durando 15 segundos (p<0,05); o controle e os grupos colados com sistema adesivo TransbondTM XT e TransbondTM Plus SEP; assim como entre o grupo colado com Opal Seal/Bond e TransbondTM Plus SEP. Quanto ao momento em o clareamento foi realizado, apenas a variável IAR apresentou diferença estatisticamente significante nos valores médios, entre os três grupos experimentais (p < 0,05). Quanto às correlações, a variação de cor verificada 1 dia após o clareamento estava fortemente correlacionada com a de 15 dias após, assim como 15 com 30 dias após clareamento. Conclusões: O tempo de condicionamento ácido e os sistemas adesivos para colagem de brackets influenciaram o ∆E após clareamento. O momento em que o clareamento foi realizado não influenciou o ∆E, mas afetou o IAR, modificando a interface de fratura do adesivo durante a descolagem de brackets. E, a variação de cor obtida após 1 dia de clareamento estava correlacionada com a verificada após 15 e 30 dias

Objective: To evaluate in vitro the degree of color changes (∆E) and their correlations after bleaching tooth surfaces subjected to orthodontic brackets bonding and debonding, regarding: 1) the etching time (15, 30 and 60 seconds); 2) the adhesive system (TransbondTM XT, Opal Seal/Bond and TransbondTM Plus SEP); 3) the time point in which bleaching was performed (before, during and after bonding of brackets) and the adhesive remnant index (IAR) after bracket debonbing. Materials and Methods: This study was divided in three articles to address each of the proposed objectives. The sample consisted of 270 extracted premolars randomly divided in 9 groups: negative control (reproducibility); positive control (tooth bleaching only); and 7 experimental groups. The tooth color was determined by the CIELab system using the spectrophotometer data, in evaluations prior to bleaching and 1, 15 and 30 days after bleaching. To test whether there was difference between the groups one-way ANOVA was used, since the sample size of each group was n=30 (p<0,05). When ANOVA indicated a difference, in order to identify which groups differed from each other, we applied the multiple comparison test of Tukey for homogeneity of variances, identified by the Levene test (p < 0,05). Results: The ∆E from pre-bleaching up to 15 and 30 days after bleaching was statistically different between: control and etching time group of 15 seconds (p < 0,05); control and groups bonded withTransbondTM XT and TransbondTM Plus SEP bonding systems; as well as the group bonded with Opal Seal/Bond and TransbondTM Plus SEP. Regarding the time when the bleaching was performed, only the variable IAR presented statistically significant difference in the mean values among the three groups (p < 0,05). As for correlations, the color variation observed 1 day after bleaching was strongly correlated with 15 days after bleaching, as well as 15 to 30 days after bleaching. Conclusion: The etching time and the bonding systems influenced the ∆E after bleaching. The time point in which bleaching was performed did not influence the ∆E, but affected the IAR, modifying the interface of adhesive fracture during bracket debonding. In addition, the ∆E obtained 1 day after bleaching was correlated with those observed 15 and 30 days after bleaching

Efeito da aplicação de adesivos de 2 passos e autocondicionantes fotoativados por luz halógena ou LED na microinfiltração marginal: estudo in vitro. / Effect of 2-step/self-each bond system and halogen light or LED on the microleakage: in vitro study.

O objetivo desse estudo foi analisar a efetividade de sistemas adesivos convencionais e autocondicionantes, e de diferentes métodos de fotoativação para redução da microinfiltração marginal. Foram utilizados 48 dentes incisivos bovinos nesse estudo. Os dentes foram divididos em quatro grupos de 12 amostras de acordo com o tipo de adesivo ou método de fotoativação utilizado: Grupo 1- Sistema adesivo de passos fotoativadas por luz halógena com intensidade de 700 mW/cm2 Grupo 2 - Sistema adesivo de dois passos fotoativados pelo LED com intensidade de 470 mW/cm2; Grupo 3 - sistema adesivo autocondicionante fotoativados por luz halógena; Grupo 4 - Sistema adesivo autocondicionante fotoativados por LED. Uma resina composta nanoparticulada foi utilizada para restaurar todas as cavidades. Em seguida, os grupos foram submetidos ao tratamento de ciclagem térmica e foram colocados por 24 horas em solução de azul de metileno. A microinfiltração foi avaliada de acordo com o grau de penetração do corante na interface dente-restauração. Para análise estatística, foi utilizado o teste não paramétrico de Kruskal Wallis complementado pelo teste de Mann-Whitney, no nível de 5% de significância. O grupo 1 apresentou estatisticamente menores índices de microinfiltração marginal que o grupo 2 na parece oclusal (p<0.05) e os grupos 1 e 4 apresentaram menores graus de microinfiltração marginal que o grupo 2 na parede cervical(p<0.05). A aplicação do sistema adesivo de dois passos associado a polimerização com luz halógena promoveram os menores graus de microinfiltração marginal.

The aim of this research was to analyze the effectiveness of conventional and self-etching bonding systems and different curing methods for reduction of marginal microleakage. 48 bovine incisor teeth were used in this study. The teeth were divided into four groups of 12 samples according to the type of adhesive system or curing method used: Group 1- Two-step bonding system photoactivated by halogen light with intensity of 700 mW/cm2; Group 2- Two-step bonding system photoactivated by LED with 470 mW/ cm2 of intensity; Group 3 - Self etch bonding system photoactivated by halogen light; Group 4- Self etch bonding system photoactivated by LED. A nanofilled composite resin was used to restore all the cavities. Then the groups were subjected to thermal cycling treatment and were placed for 24 hours in a methylene blue solution. The microleakage was assessed according to the degree ofpenetration of the colorant in tooth-restoration interface. For statistical analysis, the non-parametric Kruskal Wallis test complemented by Mann-Whitney were used with 5 % level of significance. The Group 1 showed lower marginal microleakage than Group 2 on occlusal wall (p<0.05). Adittionally, appears and the groups 1 and 4 had smaller degrees of marginal microleakage that the cervical wall 2 Group (p<0.05). The application of two-step bonding system associated with the polymerization by halogen light promoted the lowest degrees of marginal microleakage.

Influência de diferentes protocolos de fotoativação no grau de conversão e dureza de resinas ortodônticas / Influence of different curing protocols in degree of conversion and hardness the resins orthodontics

A presente Dissertação foi composta de dois estudos. O primeiro estudo avaliou in vitro a influência de diferentes tempos de exposição e potências, mantendo-se a mesma energia total, no grau de conversão (GC) e dureza superficial Knoop de três resinas ortodônticas (Transbond XT, Opal Bond MV e Transbond Plus Color Change) fotoativadas por um LED de 3a geração. A análise do GC foi realizada pelo método de Espectroscopia de infravermelho por transformada de Fourier (FT-IR) em nove grupos (n=5) e a dureza superficial Knoop também foi avaliada em nove grupos (n=15), sendo todos os grupos divididos de acordo com as resinas, potências e tempos utilizados. O segundo estudo comparou o GC de duas resinas ortodônticas (Transbond XT e Opal Bond MV) fotoativadas por um LED de 2a geração e um de 3a geração dada uma mesma densidade de energia. A análise do GC foi realizada pelo método de Espectroscopia infravermelho por transformada de Fourier (FT-IR) em quatro grupos (n=5) divididos de acordo com as resinas e gerações de LED utilizados. Os valores obtidos nos dois estudos foram analisados pelo teste ANOVA de dois níveis. No primeiro estudo, as resinas apresentaram iguais graus de conversão quando fotoativadas pelos tempos T1(8,5s) e T2(6s) e menor grau de conversão em T3 (3s). A resina Transbond Plus Color Change apresentou maior grau de conversão, seguido pela Opal Bond MV cujo grau de conversão foi maior que o da Transbond XT. As resinas apresentaram menor dureza quando fotoativadas pelo tempo T1 (8,5s), mas não houve diferença entre os tempos T2 (6s) e T3 (3s). A resina Transbond Plus Color Change apresentou maior dureza superficial do que a Opal Bond MV, sendo ambos os grupos mais duros do que Transbond XT. Foi detectada interação entre as resinas e os tempos utilizados na dureza das resinas. No segundo estudo, não houve diferença entre os graus de conversão das resinas testadas quando fotoativadas pelo LED de 2ª geração e 3ª geração, porém houve diferença entre os graus de conversão entre as duas resinas, a Opal Bond MV apresentou maior grau de conversão do que a Transbond XT. No primeiro estudo, pode-se concluir que, a polimerização com variação da potência e do tempo, mantendo a energia total constante, interfere no grau de conversão e dureza das três resinas ortodônticas estudadas. O tempo pode ser diminuído e a potência aumentada sem efeito negativo entre os tempos T1 e T2, porém, causando pequena diminuição no grau de conversão no tempo T3. Em relação à dureza superficial, há um efeito positivo quando o tempo é diminuído. No segundo estudo pode-se concluir que dada uma mesma densidade de energia, não houve influência do LED de 2ª e 3ª geração no grau de conversão das resinas ortodônticas testadas, porém, estas apresentaram diferentes graus de conversão entre si, sendo que a resina Opal Bond MV apresentou maior grau de conversão em relação à resina Transbond XT

The present dissertation consisted of two studies. The first study was aimed at assessing in vitro the influence of different exposure times and potencies, keeping the same total energy, on the degree of conversion and Knoop surface micro-hardness of three orthodontic resins (Transbond XT, Opal Bond MV, and Transbond Plus Colour Change) lightcured with a third-generation LED unit. The second study was aimed at comparing the degree of conversion of two orthodontic resins (Transbond XT and Opal Bond MV) light-cured by using 2nd and 3rd generation LED units operating at the same power density. In the first study, the degree of conversion was assessed by using the Fourier transform infrared spectroscopy (FT-IR) in nine groups (n = 15), whereas the Koop surface micro-hardness was assessed in nine groups, with groups being divided according to the resins, potency and exposure time. In the second study, the degree of conversion was also assessed by using FT-IF in four groups (n = 5) divided according to resins and LEDs used. The values obtained were analysed with two-tailed ANOVA. Resins light-cured at T1 (8.5s) and T2 (6s) showed the same values for degree of conversion, but a lower value at T3 (3s). The Transbond Plus Colour Change resin showed the highest degree of conversion, followed in the order by Opal Bond MV and Transbond XT ones. Resins showed a decreased micro-hardness when light-cured at T1 (8.5s), but no difference was found between T2 (6s) and T3 (3s). The Transbond Plus Colour Change resin showed a greater surface micro-hardness than the Opal Bond MV resin, with both groups being harder than the Transbond XT resin. A relationship between resins and exposure time was found regarding the micro-hardness of these materials. No difference was found between the degrees of conversion of the resins light-cured with 2nd and 3rd generation LEDs, although Opal Bond MV resin had a higher degree of conversion compared to the Transbond XT one. In the first study, one can conclude that variation in potency and exposure time interferes with the degree of conversion and micro-hardness of the three orthodontic resins during their polymerization, even keeping the total energy constant. Exposure time can be reduced and potency increased without having a negative effect between T1 and T2, despite causing a small decrease in the degree of conversion at T3. Also, there is a positive effect on the surface micro-hardness when exposure time is reduced. In the second study, one can conclude that 2nd and 3rd generation LEDs had no influence on the degree of conversion of orthodontic resins when operating at the same power potency, although the resins have different degrees of conversion compared to each other

How does duration of curing affect the radiopacity of dental materials?

PURPOSE: Clinicians commonly encounter cases in which it is difficult to determine whether adjacent radiopacities are normal or pathologic. The ideal radiopacity of composite resin is equal to or higher than that of the same thickness of aluminum. We aimed to investigate the possible effects of different curing times on the post-24-hour radiopacity of composite resins on digital radiographs. MATERIALS AND METHODS: One mm thick samples of Filtek P60 and Clearfil resin composites were prepared and cured with three regimens of continuous 400 mW/cm2 irradiance for 10, 20 and 30 seconds. Along with a 12-step aluminum step wedge, digital radiographs were captured and the radiopacities were transformed to the equivalent aluminum thicknesses. Data were compared by a general linear model and repeated-measures of ANOVA. RESULTS: Overall, the calculated equivalent aluminum thicknesses of composite resins were increased significantly by doubling and tripling the curing times (F(2,8)=8.94, p=0.002). Notably, Bonferroni post-hoc tests confirmed that the radiopacity of the cured Filtek P60 was significantly higher at 30 seconds compared with 10 seconds (p=0.04). Although the higher radiopacity was observed by increasing the time, other comparisons showed no statistical significance (p>0.05). CONCLUSION: These results supported the hypothesis that the radiopacity of resin composites might be related to the duration of light curing. In addition to the current standards for radiopacity of digital images, defining a standard protocol for curing of dental materials should be considered, and it is suggested that they should be added to the current requirements for dental material.

Uso de sal de iodônio em agentes resinosos para redução do tempo de fotoativação na colagem de braquetes ortodônticos: um estudo piloto / Use of iodomium salt in resin agents to reduce the photoactivation time for bonding of orthodontic brackets: a pilot study

Objetivo: Avaliar o efeito da incorporação de um sal de iodônio em cimentos resinosos experimentais em sua eficiência como agentes de fixação de braquetes ao esmalte. Materiais e Métodos: Uma mistura comonomérica de dimetacrilatos foi carregada com 35% de partículas de vidro. Três agentes foram obtidos pelo acréscimo do hexafluorfosfato de ditoliliodônio nas concentrações 0 (controle), 1 (R1) ou 2mol% (R2). Braquetes de aço inoxidável foram colados na face vestibular de incisivos bovinos, sendo fotoativados com fonte de luz de lâmpada halógena com irradiância de 400mW/cm2. Os cimentos foram fotoativados com duas exposições de luz (nas faces cervical e incisal do braquete), sendo testados dois tempos de fotoativação: 5s ou 20s. O teste de cisalhamento foi realizado 10min após a colagem. Os valores de resistência de união foram calculados em MPa e os dados submetidos a ANOVA de 2 critérios e teste de Student-Newman-Keuls (5%). O Índice de Adesivo Remanescente (IAR) foi avaliado sob aumento e submetido ao teste de Kruskal- Wallis (5%). Resultados: Para o tempo 20s houve diferenças entre todos os materiais: R1 > R2 > controle, enquanto para o tempo 5s R1 e R2 foram similares entre si, e superiores ao controle. A resistência de união para o tempo 5s foi inferior a o tempo 20s para os grupos controle e R1, e similar para R2. A redução dos valores na comparação entre os tempos 20s e 5s foi de 55% (controle), 45% (R1) e 15% (R2). Não houve diferenças significativas entre os grupos nos escores IAR. Conclusão: O desenvolvimento de agentes de fixação contendo sais de iodônio pode possibilitar a colagem de braquetes utilizando tempos reduzidos de fotoativação.(AU)

Aim: To evaluate the impact of adding an iodonium salt to experimental resin cements on their efficiency as agents for bonding brackets to enamel. Materials and Methods: A dimethacrylate co-monomer blend was loaded with 35% glass particles. Three agents were obtained by adding concentrations of 0 (control), 1 (R1) or 2mol% (R2) of ditolyliodonium hexafluorophosphate. Stainless steel brackets were bonded to the buccal faces of bovine incisors; photoactivation was carried out using a quartz-tungsten-halogen unit with 400mW/ cm2-irradiance. The cements were photoactivated using two exposures (on the cervical and incisal faces of the bracket), testing two photoactivation times: 5s or 20s. The shear test was carried out 10min after bonding. Bond strength values were calculated in MPa, and the data were submitted to a two-way ANOVA and Student-Newman-Keuls' test (5%). The Adhesive Remnant Index (ARI) was evaluated under magnification and submitted to the Kruskal-Wallis test (5%). Results: For the time 20s, significant differences among all materials were observed: R1 > R2 > control, whereas for the time 5s, R1 and R2 were similar, showing higher bond strength than the control. The bond strength for the time 5s was lower than for the time 20s for control and R1, but similar for R2. The reduction in bond strength values comparing the times 20s and 5s was 55% (control), 45% (R1) and 15% (R2). Conclusion: The development of bonding agents containing iodonium salts may produce a favorable atmosphere for bonding brackets using reduced photoactivation times.(AU)