Effect of Light Sources on Bond Strength of Different Composite Resins Repaired with Bulk-Fill Composite / Efecto del tipo de fuente luz en la resistencia adhesiva de distintas resinas compuestas reparados con una resina bulk-fill

Abstract: The aim of this study was to evaluate and compare the effects of different light sources on shear bond strength when bulk-fill composite was used for the repair of different composite resins. A total of 126 samples made from six resin composites with different properties were aged (thermal-cycling with 5000 cycle), exposed to the same surface treatments and adhesive procedure. Then, they were repaired with a bulk-fill composite. At the polymerization step, each group was divided into three subgroups (n=7) and light cured with a QTH light source for 40s and two different LED light sources for 20s. Subsequently, the specimens were aged in distilled water at 37 ºC for 4 weeks and then subjected to shear bond strength test. Then, the specimens were examined under a stereomicroscope to identify modes of failure and visualized by Scanning Electron Microscope. Data obtained from the study were analyzed using ANOVA and Tukey HSD Test (α=0.05). In all groups, the light curing units had an impact on shear bond strength (p<0.05). Among the study groups, the greatest bond strength values were observed in the specimens repaired using the LED and the specimens repaired with the QTH light curing unit had the lowest bond strength values. It was concluded that the content of composite resins and light curing units may influence bond strength of different composites repaired with the bulk-fill composite.

Resumen: El objetivo de este estudio fue evaluar y comparar los efectos de diferentes fuentes de luz sobre la resistencia de la unión al cizallamiento cuando se utiliza una resina bulk-fill para la reparación de diferentes resinas compuestas. Se envejecieron un total de 126 muestras fabricadas con seis compuestos de resina con diferentes propiedades (ciclo térmico con 5000 ciclos), expuestas a los mismos tratamientos de superficie y procedimiento adhesivo. Luego, fueron reparadas con una resina bulk- fill. En el paso de polimerización, cada grupo fue dividido en tres subgrupos (n=7) y fotopolimerizado con una fuente de luz QTH por 40s y dos fuentes de luz LED por 20s. Posteriormente, los especímenes se envejecieron en agua destilada a 37 ºC durante 4 semanas y luego se sometieron a una prueba de resistencia adhesiva de cizalla. Luego, los especímenes fueron examinados bajo un estereomicroscopio para identificar los modos de falla y visualizados por el Microscopio Electrónico de Barrido. Los datos obtenidos del estudio fueron analizados usando el ANOVA y la prueba Tukey HSD (α=0.05). En todos los grupos, las unidades de fotopolimerización tuvieron un impacto en la fuerza de adhesión al cizallamiento (p<0,05). Entre los grupos de estudio, los mayores valores de fuerza de adhesión se observaron en los especímenes reparados utilizando el LED y los especímenes reparados con la unidad de fotopolimerización QTH tuvieron los valores de fuerza de adhesión más bajos. Se llegó a la conclusión de que el contenido de las resinas compuestas y las unidades de fotopolimerización pueden influir en la fuerza de adhesión de los diferentes compuestos reparados con resinas bulk-fill.

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

Effect of different light curing methods on mechanical and physical properties of resin-cements polymerized through ceramic discs

OBJECTIVE: The aim of this study was to compare the polimerization ability of three different light-curing units (quartz tungsten halogen, light-emitting diodes and plasma arc) and their exposure modes (high-intensity and soft-start) by determination of microhardness, water sorption and solubility, and diametral tensile strength of 5 dual-curing resin cements. Material and methods: A total of 720 disc-shaped samples (1 mm height and 5 mm diameter) were prepared from different dual-curing resin cements (Duolink, Nexus, Bifix-QM, Panavia F and RelyX Unicem). Photoactivation was performed by using quartz tungsten halogen (high-power and soft-up modes), light-emitting diode (standard and exponential modes) and plasma arc (normal and ramp-curing modes) curing units through ceramic discs. Then the samples (n=8/per group) were stored dry in the dark at 37°C for 24 h. The Vickers hardness test was performed on the resin cement layer with a microhardness tester (Shimadzu HMV). For sorption and solubility tests; the samples were stored in a desiccator at 37°C and weighed to a constant mass. The samples were weighed both before and after being immersed in deionized water for different periods of time (24 h and 7 days) and being desiccated. The diametral tensile strength of the samples was tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed statistically by nonparametric Kruskal Wallis and Mann-Whitney U tests at 5 percent significance level. RESULTS: Resin cement and light-curing unit had significant effects (p<0.05) on microhardness, diametral tensile strength, water solubility and sorption. However, no significant differences (p>0.05) were obtained with different modes of LCUs. Conclusion: The study indicates that polymerization of resin cements with different light-curing units may result in various polymer structures, and consequently different mechanical and physical properties.

Effect of light curing unit on resin-modified glass-ionomer cements: a microhardness assessment

OBJECTIVE: To evaluate the microhardness of resin-modified glass-ionomer cements (RMGICs) photoactivated with a blue light-emitting diode (LED) curing light. MATERIAL AND METHODS: Thirty specimens were distributed in 3 groups: Fuji II LC Improved/GC (RM1), Vitremer/3M ESPE (RM2) and Filtek Z250/ 3M ESPE (RM3). Two commercial light-curing units were used to polymerize the materials: LED/Ultrablue IS and a halogen light/XL3000 (QTH). After 24 h, Knoop microhardness test was performed. Data were submitted to three-way ANOVA and Tukey's test at a pre-set alpha of 0.05. RESULTS: At the top surface, no statistically significant difference (p>0.05) in the microhardness was seen when the LED and QTH lights were used for all materials. At the bottom surface, microhardness mean value of RM2 was significantly higher when the QTH light was used (p<0.05). For RM1, statistically significant higher values (p<0.05) were seen when the LED light was used. No statistically significant difference (p>0.05) was seen at the bottom surface for RM3, irrespective of the light used. Top-to-bottom surface comparison showed no statistically significant difference (p>0.05) for both RMGICs, regardless of the light used. For RM3, microhardness mean value at the top was significantly higher (p<0.05) than bottom microhardness when both curing units were used. CONCLUSION: The microhardness values seen when a LED light was used varied depending on the restorative material tested.

UV-Vis spectrophotometric analysis and light irradiance through hot-pressed and hot-pressed-veneered glass ceramics

This study evaluated the irradiance of curing units through core and veneered hot-pressed ceramics as well as the transmittance of these materials. Discs of 0.7, 1.4 and 2 mm in thickness of Empress (EMP) and Empress Esthetic (EST), and 0.8 (n=5) and 1.1 mm (n=5) thickness of Empress 2 (E2) were obtained. For E2, two of the 0.8-mm-thick discs were covered with dentin (1.2- and 1.4-mm-thick) and two with dentin + enamel (1.5-mm-thick). The 1.1-mm-thick specimens were submitted to the same veneering procedures. Specimens were evaluated by UV-Vis transmittance analysis and the percentage of transmittance was recorded. Irradiance through each specimen was evaluated with a quartz-tungsten-halogen (QTH), used in continuous or intermittent exposure modes, or a blue light-emitting diode (LED). Data were analyzed by Dunnett's test, ANOVA and Tukey's test at 5 percent significance level. Exposure through ceramic decreased the irradiance for all ceramics. Irradiance through EST was significantly higher than through EMP. For E2, reduction in irradiance depended on the core and/or veneer thickness. The QTH intermittent mode showed higher irradiance than the continuous mode, and both showed higher irradiance than LED. The ceramic significantly influenced irradiance and transmittance, which were found to decrease with the increase in thickness.

Este estudo avaliou a irradiância de unidades de fotoativação através de cerâmicas para subestrutura com e sem cobertura, e a transmitância desses materiais. Discos de 0,7, 1,4 e 2 mm de espessura de Empress (EMP) e Empress Esthetic (EST), e de 0,8 (n=5) e 1,1 mm (n=5) de espessura de Empress 2 (E2) foram obtidos. Para E2, dois discos de 0,8 mm foram cobertos com dentina (1,2 e 1,4 mm de espessura) e dois com dentina + esmalte (1,5 mm de espessura). Os discos de 1,1 mm de espessura foram submetidos aos mesmos procedimentos de cobertura. Os espécimes foram avaliados por análise de transmitância UV-Vis e o percentual de transmitância foi registrado. A irradiância através dos discos foi avaliada com fonte de luz de lâmpada halógena de quartzo-tungstênio (QTH), utilizada nos modos contínuo ou intermitente, e diodo emissor de luz (LED). Os dados foram analisados com testes de Dunnett, ANOVA e Tukey com nível de significância de 5 por cento. A exposição através da cerâmica reduziu a irradiância para todas as cerâmicas. A irradiância através de EST foi maior que EMP. Para E2, a redução dependeu da espessura da subestrutura e/ou cobertura. O modo intermitente para QTH mostrou maior irradiância que o modo contínuo; ambos apresentaram maior irradiância que o LED. A cerâmica influenciou significativamente a irradiância e transmitância, que diminuíram com o aumento da espessura.

Microhardness of composite resins at different depths varying the post-irradiation time

OBJECTIVE: The purpose of this study was to assess the microhardness of posterior composite resins at different depths varying the post-irradiation time. MATERIALS AND METHODS: For each composite resin [Solitaire 2 (SO) - Heraus Kulzer, P60 (P) - 3M, Prodigy Condesable (PC) - Kerr, Surefil (S) - Dentsply and Alert (A) - Pentron], 6 specimens (3 mm in diameter; 4mm high) were prepared using a black polyurethane cylindrical matrix. The resins were inserted in a bulk increment and light cured for 40 seconds. Microhardness was analyzed at different depths (top, 0.4 mm, 1.0 mm, 2.0mm, 3.0 mm and 4.0 mm) and at two moments (20 minutes and 24 hours after light-curing). Data were analyzed by ANOVA and Tukey's test (p<0.05). RESULTS: Overall, microhardness means decreased significantly with the increase of depth, being lower in the first moment tested. P, S and PC showed the highest microhardness means. CONCLUSION: It may be concluded that the tested composite resins presented a gradual decrease of microhardness as depth increased and this drop was more accentuated for depths beyond 2 mm. For all materials, higher microhardness means were recorded 24 hours after light activation. P60 yielded the best results at the different depths evaluated.

The polymerization rate and the degree of conversion of composite resins by different light sources / 대한치과보존학회지

OBJECTIVES: The purpose of this study was to observe the reaction kinetics and the degree of polymerization of composite resins when cured by different light sources and to evaluate the effectiveness of the blue Light Emitting Diode Light Curing Units (LED LCUs) compared with conventional halogen LCUs. MATERIALS AND METHODS: First, thermal analysis was performed by a differential scanning calorimeter (DSC). The LED LCU (Elipar Freelight, 320 mW/cm2) and the conventional halogen LCU (XL3000, 400 mW/cm2) were used in this study for curing three composite resins (SureFil, Z-250 and AEliteFLO). Second, the degree of conversion was obtained in the composite resins cured according to the above curing mode with a FTIR. Third, the measurements of depth of cure were carried out in accordance with ISO 4049 standards. Statistical analysis was performed by two-way ANOVA test at 95% levels of confidence and Duncan's procedure for multiple comparisons. RESULTS: The heat of cure was not statistically different among the LCUs (p > 0.05). The composites cured by the LED (Exp) LCUs were statistically more slowly polymerized than by the halogen LCU and the LED (Std) LCU (p < 0.05). The composite resin groups cured by the LED (Exp) LCUs had significantly greater degree of conversion value than by the halogen LCU and the LED (Std) LCU (p = 0.0002). The composite resin groups cured by the LED (Std) LCUs showed significantly greater depth of cure value than by the halogen LCU and the LED (Exp) LCU (p < 0.05).