Impact of photoinitiator quality on chemical-mechanical properties of dental adhesives under different light intensities / Impacto da qualidade de fotoiniciadores nas propriedades químico mecânicas de adesivos dentais sob diferentes intensidades de luz

Objective: Evaluate the mechanical properties of experimental adhesive models with different photoinitiators (PI) polymerized by LED units of different power densities. Material and Methods: Three groups of adhesive models based on HEMA/BisGMA (45/55) were prepared in association with different PI combinations: G2 (control) ­ 2 PI: 0.5% CQ, 0.5% EDMAB; G3 - 3 PI: 0.5% CQ; 0.5% DMAEMA, 0.5% DPIHP; G4 - 4 PI: 0.5% CQ; 0.5% EDMAB; 0.5% DMAEMA; 0.5% DPIHP. The three formulations were polymerized at two different LED power densities: 550 mW/cm2 and 1200 mW/cm2. The degree of conversion (DC) of adhesive monomers was monitored in situ through the FTIR for 600 s. Specimens were prepared for each formulation for analysis mong adhesive systems (G2

Objetivo: Avaliar as propriedades mecânicas de modelos adesivos experimentais com diferentes fotoiniciadores (PI) polimerizados por unidades de LED de diferentes densidades de energia. Material e Métodos: Três grupos de modelos adesivos baseados em HEMA/BisGMA (45/55) foram preparados em associação com diferentes combinações de PI: G2 (controle) ­ 2 PI: 0,5% CQ, 0,5% EDMAB; G3 - 3PI: 0,5% CQ; 0,5% DMAEMA, 0,5% DPIHP; G4 - 4 PI: 0,5% CQ; 0,5% EDMAB; 0,5% DMAEMA; 0,5% DPIHP. As três formulações foram polimerizadas em duas densidades de potência de LED: 550 mW/cm2 e 1200 mW/cm2. O grau de conversão (DC) dos monômeros adesivos foi monitorado in situ através do FTIR durante 600 s. Amostras foram preparadas para cada formulação para análise de resistência à flexão (FS), módulo de elasticidade (ME), sorção (SOR) e solubilidade (SOL). Os dados foram submetidos aos testes ANOVA 2-fatores e Tukey (5%). Resultados: DC: houve diferença significativa entre os sistemas adesivos (G2

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 MDP concentration and addition of iodonium salt on the dentin bond strength of experimental adhesives / Efeito da concentração de MDP e adição de sal de iodônio na resistência de união à dentina de adesivos experimentais

Objetivo: O objetivo foi avaliar a resistência de união de seis adesivos experimentais contendo sistemas fotoiniciadores binários ou ternários, associados a três diferentes concentrações de MDP (0-12% em peso) após 12 meses de armazenamento em água destilada. Material e Métodos: Adesivos experimentais foram preparados com: bis-GMA, UDMA, bis-EMA, TEGDMA, HEMA, BHT e etanol, contendo sistemas fotoiniciadores binários (CQ/amina) ou ternários (CQ/amina/DPIHFP ­ 0,5% em peso). Foi adicionado a esta composição 0%, 6% ou 12% em peso de MDP. Os sistemas adesivos foram aplicados seguindo o protocolo com condicionamento ácido. Moldes cilíndricos transparentes foram colocados sobre a dentina hibridizada, preenchidos com resina composta e fotopolimerizados. Os corpos-de-prova foram armazenados em água destilada a 37oC por 24h ou 12 meses e submetidos ao ensaio de microcisalhamento (n=6). Os dados foram analisados por ANOVA de três fatores e teste de Tukey (α=5%). Resultados: Para o sistema binário, após 12 meses de armazenamento, todos os valores de resistência de união foram semelhantes. Em relação à degradação da resistência de adesão ao longo do tempo, as formulações de MDP de 6% e 12% mostraram resistência de união mais estável do que 0% de MDP. Para o sistema ternário, todas as formulações (0%, 6% e 12% em massa de MDP) mostraram resistência de união estável em função do tempo. Conclusão: Para o sistema binário, as concentrações de 6 e 12% em massa de MDP foram capazes de manter a resistência de união em função do tempo, enquanto que para o sistema ternário, a estabilidade de união foi obtida independentemente da concentração de MDP. Pode-se concluir que, para a formulação dos adesivos utilizados neste estudo, independente do sistema fotoiniciador, a concentração de 12% MDP apresentou valores de resistência de união mais estáveis após 12 meses de armazenamento em água (AU)

Objective: The aim was to evaluate the bond strength of six experimental adhesives containing binary or ternary photoinitiator systems, associated with three different MDP concentrations (0-12wt%) after 12 months of storage in distilled water. Material and Methods: Experimental adhesives were prepared with: bis-GMA, UDMA, bis-EMA, TEGDMA, HEMA, BHT, and ethanol, containing binary (CQ/amine) or ternary (CQ/amine/DPIHFP (diphenyliodonium hexafluorophosphate) ­ 0.5wt%) photoinitiator systems. It was added to this composition 0wt%, 6wt%, or 12wt% of MDP. The adhesive systems were applied following the etch-and-rinse protocol. Transparent cylindrical molds were placed on the hybridized dentin, filled with composite resin and light-cured. The specimens were stored in distilled water at 37oC for 24h or 12 months and submitted to a microshear bond strength test (n=6). Data were analyzed by three-way ANOVA and Tukey's test (α=5%). Results: For the binary system, after 12 months of storage, all bond strength values were similar. Regarding bond strength degradation over time, 6wt% and 12wt% MDP formulations showed more stable bond strength than 0wt% MDP. For the ternary system, all formulations (0wt%, 6wt% and 12wt%) showed stable bond strength over time. Conclusion: For the binary photoinitiator system, the 6wt% and 12wt% MDP concentrations were able to keep bond strength stable over time, while for the ternary system, bond strength stability was achieved regardless the MDP concentration. (AU)

Effect of light attenuation through veneers on bond strength of adhesives with photoinitiator combinations

Abstract This study aimed to evaluate the effect of light attenuation through ceramic veneers and resin cement on degree of conversion (DC), cohesive strength (CS), and microshear bond strength (μSBS) of experimental adhesive systems. Experimental etch-and-rinse and self-etch adhesives were combined with different ratios of camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiators: CQ-only; 3CQ:1TPO; 1CQ:1TPO; 1CQ:3TPO and TPO-only. Square-shaped ceramic veneer (IPS Empress Esthetic, Ivoclar Vivadent) (n = 10; 10mm long x 10mm wide x 0.5mm thick) and resin cement specimens (Variolink Esthetic LC, Ivoclar Vivadent) (n = 10; 10 mm long x 10 mm wide and 0.3 mm thick) were prepared. Light transmittance of a multiple-peak LED (Bluephase G2, Ivoclar Vivadent) was measured through restorative materials using a spectrometer (n = 5). Adhesive specimens were analyzed for DC, CS, and μSBS by light-curing the adhesive with or without (control) ceramic veneer, and with resin cement fixed to output region of the light-curing tip (n = 10). Data were submitted to ANOVA and Tukey's test (α = 0.05). Total light transmittance through the restorative materials was attenuated, and this attenuation was more evident for the violet spectrum. The DC for the TPO groups in ratios up to 1CQ:1TPO was similar to the control. 1CQ:3TPO showed lower values for CS. μSBS was reduced for all groups with light attenuation, but lower values were observed for 1CQ:3TPO and TPO-only. In conclusion, light transmission was reduced with interposed restorative materials. Adhesives combined with CQ and TPO up to 1CQ:1TPO showed greater cure efficiency and mechanical properties compared with a higher amount of TPO.

Evaluation of the Light Intensity Emitted by the Light-curing Devices of a Dental School Clinic in the North of Brazil: a Pilot Study / Avaliação da Intensidade de Luz Emitida Pelos Fotopolimerizadores de uma Clínica-Escola da Região Norte do Brasil: um Estudo-Piloto

Photoactivated composite resins are among the most widespread restorative materials in dentistry, particularly in cosmetic dentistry. To obtain the best properties of the material, the resins must have their polymerization reaction initiated by means of the light-curing device, which activates the photoinitiators present in the composites. For this process to occur in the desired way, it is essential that the light-curing device emits light at the intensity necessary to properly activate the photoinitiators. Thus, a pilot study was carried out to assess the light intensity emitted by the light-curing devices used in a school clinic. To assess the light intensity emitted by the devices, a radiometer was used. Twentyfour light-curing devices were evaluated, 13 Optilight Max devices, 8 Optilight LD MAX 440 devices, 3 Emitter C. devices. All the devices had an emitted light below 400 mW / cm² and 67% of the devices had intensity above 300 mW/cm². The average light emission values of the light-curing devices were Optilight Max 334mW/cm², Emitter C 275mW/cm², Optilight LD MAX 440 296mW/cm². It was concluded that no light-curing device emitted light at the recommended intensity (400 mW/cm²), two thirds of the devices emitted light in intensity above the minimum required for photopolymerization of composite resin increments of up to 2mm and one third emitted light in intensity below the required minimum. There was no difference among the light-curing device models tested in this study. (AU)

As resinas compostas fotoativadas estão entre os materiais restauradores mais difundidos em odontologia, particularmente na odontologia estética. Para obtenção das melhores propriedades do material, as resinas precisam ter sua reação de polimerização iniciada por meio do fotopolimerizador, que ativa os fotoiniciadores presentes nos compósitos. Para que esse processo ocorra da forma desejada, é fundamental que o fotopolimerizador emita a luz na intensidade necessária para ativar adequadamente os fotoiniciadores. Assim, foi realizado um estudo piloto para avaliadar a intensidade da luz emitida pelo fotopolimerizadores utilizados em uma clínica-escola. Para avaliar a intensidade da luz emitida pelos dispositivos, foi utilizado um radiômetro. Vinte e quatro fotopolimerizadores foram avaliados, 13 aparelhos Optilight Max, 8 aparelhos Optilight LD MAX 440, 3 aparelhos Emitter C. Todos os dispositivos tiveram a luz emitida em intensidade inferior a 400 mW/ cm² e 67% dos dispositivos apresentaram intensidade acima de 300 mW/cm². As médias de valores de emissão de luz dos fotopolimerizadores foram, Optilight Max 334mW/cm², Emitter C 275mW/cm², Optilight LD MAX 440 296mW/cm²Concluiu-se que nenhum fotopolimerizador emitiu luz na intensidade recomendada (400 mW/cm²), dois terços dos aparelhos emitiram luz em intensidade acima da mínima necessária para fotopolimerização de incrementos de resina composta de até 2mm e um terço emitiu luz em intensidade abaixo da mínima necessária. Não houve diferença entre os modelos de fotopolimerizador testados neste estudo.(AU)

Effect of combining photoinitiators on cure efficiency of dental resin-based composites

Abstract Camphorquinone is the most conventionally used photoinitiator in Dentistry. Although different alternative photoinitiators have been proposed, no photoinitiator was capable of completely substituting camphorquinone. The combination of photoinitiators has been considered the best alternative. Objectives: To evaluate the effect of combining Norrish type I and II photoinitiators on the cure efficiency of dental resin-based composites. Methodology: Experimental composites were produced containing different photoinitiator systems: Norrish type I-only, mono-alkyl phosphine oxide (TPO); Norrish type II-only, camphorquinone (CQ); or its combination, CQ and TPO, in a 1: 1 molar ratio. UV-vis absorption spectrophotometry was performed to assess the consumption of each photoinitiator after curing (n=3). A multi-wave LED (Bluephase® G2, Ivoclar Vivadent) was pre-characterized and used with a radiant exposure of 24 J/cm2. The degree of conversion was evaluated by Raman spectrometry, and the elution of the monomers by nuclear magnetic resonance analysis (n=3). Data were analyzed using ANOVA and Tukey's test (α=0.05; β=0.2). Results: The combination of CQ and TPO increased the consumption of the photoinitiator system compared to CQ-only (p=0.001), but presented similar consumption compared to TPO-only (p=0.52). There was no significant difference in the degree of conversion between the composites regardless of the photoinitiator system (p=0.81). However, the elution of the monomers was reduced when both photoinitiators were combined. TPO-based material presented the highest elution of monomers. Conclusions: The combination of the photoinitiator systems seems to be beneficial for the cure efficiency of dental resin-based composites.

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)

Influence of different types of light curing units and photoinitiators in microhardness and color of composite resins after immersion in wine / Influencia dos diferentes tipos de unidade fotoativadoras e fotoiniciadores na microdureza e cor de resinas compostas após imersão em vinho

Objective: the aim of this study is to evaluate the microhardness and color change (∆E) of composite resins, that were light-cured with different LEDs, after being immersed in a staining drink. Material and Methods: Two composite resins with Lucerin-TPO (Tetric N-Ceram/ Vit-l-escence) and camphorquinone (Filtek Z350) were selected. The specimens (n=120) were prepared and lightcured with LED of monowave or polywave lightemitting diode (LED) devices. Microhardness and color evaluations were measured before and after immersion in staining drink. Microhardness data were evaluated by Kruskal-Wallis test, MannWhitney and Wilcoxon tests. Color changes were evaluated by two-way analysis of variance (ANOVA) and Tukey test (p ≤ 0.05). Results: No statistically significant difference between the two generations of LEDs was found for microhardness data. Regarding the ∆E, a statistical difference between the two LEDs was observed for Tetric NCeram and Filtek Z350. Conclusion: The compostion of composites appears to have more influence on analyses than the type of LEDs used. A decreased microhardness occurred to Vit-lescence for monowave and to Filtek Z350 for both LED devices. A clinically perceptible color change was observed for Tetric-N Ceram and Filtek Z350 when polywave LED were used. (AU)

Objetivo: o objetivo deste estudo foi aviliar a microdureza e alteração de cor (∆E) de resinas compostas, fotoativadas com diferentes LEDs, imergidas em bebidas pigmetadas. Material e métodos: Duas resinas compostas com Lucerina-TPO (Tetric N-Ceram/ VIt-l-essence) e canforoquinona (Filtek Z350) foram selecionadas. Os espécimes (n=120) foram preparados. Os mesmos foram fotopolimerizados com LED monowave ou polywave. Microdureza e cor foram avaliadas antes e após a imersão em bebidas pigmentadas. Os dados de microdureza foram avaliados pelos testes de Kruskal-Wallis, Mann-Whitney e Wilcoxon. As alterações de cor foram avaliadas por análise de variância a dois critérios (ANOVA) e Tukey (p ≤ 0,05). Resultados: Não foi encontrada diferença estatística entre as duas gerações de LEDs, para os dados da microdureza. Quanto ao ∆E, foi encontrada diferença estatisticamente significante entre os dois LEDs, sendo observadas na Tetric N-Ceram na FIltek Z350. Conclusão: A composição das resinas compostas parece ter mais influencia nas análises do que o tipo de LEDs. Uma redução na microdureza ocorreu para Vit-lescence para monowave e para Filtek Z350 para ambos os dispositivos LED. Uma mudança de cor clinicamente perceptível foi observada em Tetric-N Ceram para polywave e Filtek Z350 para ambos os dispositivos LED. (AU)

Effect of diphenyliodonium hexafluorphosphate in the yellowing and properties of experimental resin cements

Aim: The yellowing effect is undesirable and can occur in the dental restoration margins when light-cured resin cements containing camphorquinone as photoinitiator is used. This study aimed to evaluate the effect of diphenyliodonium hexafluorphosphate (DPI) in photoinitiator systems that contained different concentrations of camphorquinone (CQ) and dimethylamino ethyl benzoate (EDAB) on resin cements. Methods: A base (1:1) of bisphenol A diglycidyl methacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA) was obtained, and 60wt% of glass fillers was added. Eight formulations were obtained: RC1 (0.5mol% CQ / 1mol% EDAB), RC2 (0.5mol% CQ / 2mol% EDAB), RC3 (1mol% CQ / 1mol% EDAB), RC4 (1mol% CQ / 2mol% EDAB), and RC5 to RC8, which contained the same bases plus 0.5mol% DPI. Experimental resin cements were evaluated by the degree of conversion (DC), L*a*b* color analysis, water sorption (WS) and solubility (S), flexural strength, and Elastic Modulus. The data were analyzed by three-way ANOVA, Tukey's and Mann-Whitney tests (α = 0.05). Results: The combination of DPI and 0.5mol% CQ increased DC in RC6 and L* in RC5 without increasing the WS and a* b* values. CQ at 1mol% showed higher values of b* and lower values of a*, except for RC3. Groups with 2mol% EDAB showed higher DC. Conclusion: The addition of DPI reduces CQ, generating a decreased yellowing effect, while maintaining adequate properties in the resin cements, especially with 2mol% EDAB

Impacto de la luz operatoria sobre las resinas compuestas: evaluación de su contracción / The impact of operative light on composite resins: evaluation of their shrinkage

El objetivo de este estudio fue analizar el comportamiento, contracción volumétrica, de diferentes resinas compuestas de fotopolimerización, expuestas a variadas condiciones de incidencia lumínica. Se tomaron volúmenes estandarizados de 7 resinas compuestas (microhíbridas y nanohíbridas y nanoparticulados) que se colocaron sobre una línea de referencia en portaobjetos, cubriéndose luego con otro y aplicando una fuerza previamente establecida. Se midió luego con un calibre electrónico la variaciones en el diámetro de la muestra bajo tres situaciones diferentes: luz ambiente (natural), luz foco (halógena), luz artificial (tubos fluorescentes) y sus combinaciones. Resultados: Se observó la mayor variación porcentual al exponer a las muestras simultáneamente a la luz ambiente, artificial y operatoria, siendo los valores más altos de reducción para las resinas compuestas Brilliant NG Coltene (Dentina) y Miris 2 Coltene (Dentina) con -2.52% y -2.7% respectivamente. Conclusión: existieron modificaciones en el volumen de todos los materiales expuestos a las diferentes condiciones de luz y tiempo de exposición. Comparando los resultados con el estudio previo (2007) se pude inferir que los materiales usados en el presente estudio resultaron más fotosensibles, dado que a similar exposición, aumentaron y/redujeron su tamaño en mayor medida (AU)

Light curing in dentistry and clinical implications: a literature review

Abstract Contemporary dentistry literally cannot be performed without use of resin-based restorative materials. With the success of bonding resin materials to tooth structures, an even wider scope of clinical applications has arisen for these lines of products. Understanding of the basic events occurring in any dental polymerization mechanism, regardless of the mode of activating the process, will allow clinicians to both better appreciate the tremendous improvements that have been made over the years, and will also provide valuable information on differences among strategies manufacturers use to optimize product performance, as well as factors under the control of the clinician, whereby they can influence the long-term outcome of their restorative procedures.

Effects of radiant exposure values using second and third generation light curing units on the degree of conversion of a lucirin-based resin composite

Abstract Alternative photoinitiators with different absorption wavelengths have been used in resin composites (RCs), so it is crucial to evaluate the effectiveness of light-curing units (LCUs) on these products. Objective Using Fourier transform infrared analysis (FTIR) in vitro, the effects of varying radiant exposure (RE) values generated by second and third generation LED LCUs on the degree of conversion (DC) and maximum rate of polymerization (Rpmax) of an experimental Lucirin TPO-based RC were evaluated. Material and Methods 1 mm or 2 mm thick silicon molds were positioned on a horizontal attenuated total reflectance (ATR) unit attached to an infrared spectroscope. The RC was inserted into the molds and exposed to varying REs (18, 36 and 56 J/cm2) using second (Radii Plus, SDI) and third generation LED LCUs (Bluephase G2/Ivoclar Vivadent) or a quartz tungsten based LCU (Optilux 501/SDS Kerr). FTIR spectra (n=7) were recorded for 10 min (1 spectrum/s, 16 scans/spectrum, resolution 4 cm-1) immediately after their application to the ATR. The DC was calculated using standard techniques for observing changes in aliphatic to aromatic peak ratios both prior to, and 10 min after curing, as well as during each 1 second interval. DC and Rpmax data were analyzed using 3-way ANOVA and Tukey’s post-hoc test (p=0.05). Results No significant difference in DC or Rpmax was observed between the 1 mm or 2 mm thick specimens when RE values were delivered by Optilux 501 or when the 1 mm thick composites were exposed to light emitted by Bluephase G2, which in turn promoted a lower DC when 18 J/cm2 (13 s) were delivered to the 2 mm thick specimens. Radii Plus promoted DC and Rpmax values close to zero under most conditions, while the delivery of 56 J/cm2 (40 s) resulted in low DC values. Conclusions The third generation LCU provided an optimal polymerization of Lucirin TPO-based RC under most tested conditions, whereas the second generation LED-curing unit was useless regardless of the RE.

Influence of Different Photoinitiators on Polymerization Kinetics and Marginal Microleakage in Restorations using Photopolymerizable Dental Composites

Objective: To evaluate the influence of four different photoinitiators on the polymerization kinetics and marginal microleakage in class V restorations using photopolymerizable dental composites. Material and Methods: Four photopolymerizable dental composites based on Bis-GMA (14.5 wt %), UDMA (6.5 wt %) and silanized filler particles (79 wt %) containing different photoinitiators were formulated. Camphorquinone (CQ)/amine, phenyl-propanedione (PPD), monoacylphosphine oxide (Lucirin® TPO) and bisacylphosphine oxide (Irgacure® 819) were used as photoinitiators. Sixteen intact human third molars were selected and divided into four groups. All teeth received class V cavity preparations in their buccal and lingual surfaces and were submitted to a dye leakage test. Data were independently analyzed for both enamel and dentin, and the results were assessed by a Kruskal-Walis test. The polymerization reactions of the four composites were evaluated by differential scanning calorimeter coupled with photocalorimeter accessory. Results: Lucirin® TPO presented the highest scores for microleakage in enamel, whereas the other photoinitiators have not demonstrated statistical differences. The lowest scores were obtained for PPD in dentin while the highest scores have been achieved by Irgacure® 819 and Lucirin® TPO. Photocalorimetric measurements demonstrated a correlation between polymerization reaction rate and marginal leakage, showing that faster reactions cause greater marginal leakage. Conclusion: Marginal microleakage scores in photopolymerizable dental composites can be greatly influenced by different types of photoinitiators through their distinct reaction rates.

Evaluation of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental dental resin-based materials

ABSTRACT Objective To evaluate the influence of phenyl-propanedione on yellowing and chemical-mechanical properties of experimental resin-based materials photoactivated using different light curing units (LCUs). Material and Methods Experimental resin-based materials with the same organic matrix (60:40 wt% BisGMA:TEGDMA) were mechanically blended using a centrifugal mixing device. To this blend, different photoinitiator systems were added in equimolar concentrations with aliphatic amine doubled by wt%: 0.4 wt% CQ; 0.38 wt% PPD; or 0.2 wt% CQ and 0.19 wt% PPD. The degree of conversion (DC), flexural strength (FS), Young’s modulus (YM), Knoop hardness (KNH), crosslinking density (CLD), and yellowing (Y) were evaluated (n=10). All samples were light cured with the following LCUs: a halogen lamp (XL 2500), a monowave LED (Radii), or a polywave LED (Valo) with 16 J/cm2. The results were analysed by two-way ANOVA and Tukey’s test (α=0.05). Results No statistical differences were found between the different photoinitiator systems to KNH, CLS, FS, and YM properties (p≥0.05). PPD/CQ association showed the higher DC values compared with CQ and PPD isolated systems when photoactivated by a polywave LED (p≤0.05). Y values were highest for the CQ compared with the PPD systems (p≤0.05). Conclusion PPD isolated system promoted similar chemical and mechanical properties and less yellowing compared with the CQ isolated system, regardless of the LCU used.

Influence of Photoinitiator and Light-Curing Source on Bond Strength of Experimental Resin Cements to Dentin

Abstract This study evaluated the bond strength (BS) of experimental resin cements formulated with different photoinitiators when activated by two kinds of light-curing units (LCUs) through a ceramic material. Seven resin blends with different camphorquinone (CQ) and/or phenylpropanedione (PPD) concentrations (weight) were prepared: C5: 0.5% CQ; C8: 0.8% CQ; P5: 0.5% PPD; P8: 0.8% PPD; C1P4: 0.1% CQ and 0.4% PPD; C4P1: 0.4% CQ and 0.1% PPD; C4P4: 0.4% CQ and 0.4% PPD. Two LCUs were used: one quartz-tungsten-halogen (QTH - 850 mW/cm²) and one light-emitting diode (LED - 1300 mW/cm²). The microtensile bond strength of each blend was assessed. Data were submitted to two-way ANOVA and Tukey's test (α=0.05). The BS values did not exhibit significant differences for LCUs, regardless of the photoinitiator type. Three cements showed significant differences: P5 and C5 had higher BS with QTH, and C4P1 with LED. For QTH, P5 showed the highest and C1P4 the lowest BS. For the LED, C4P1 showed the highest BS of all the cements. The results indicated that PPD was a viable alternative in the formulation of photocured resin cements, reducing or eliminating CQ that is yellowish without impairing the bond strength. Furthermore, both LED and QTH were effective in curing resin cements that contain PPD or CQ.

Resumo Este estudo avaliou a resistência de união (BS) de cimentos resinosos experimentais formulados com diferentes fotoiniciadores, quando ativados através de cerâmica, por dois tipos de fontes luminosas (LCUs). Foram preparadas sete formulações com diferentes concentrações em peso (wt) de canforquinona (CQ) e/ou fenilpropanodiona (PPD): C5: 0,5%CQ; C8: 0,8%CQ; P5: 0,5%PPD; P8: 0,8%PPD; C1P4: 0,1%CQ e 0.4%PPD; C4P1: 0,4%CQ e 0,1%PPD; C4P4: 0,4%CQ e 0,4%PPD. Duas LCUs foram usadas: uma com luz halógena (QTH - 850 mW/cm²) e uma com diodo emissor de luz (LED - 1300 mW/cm²). A BS foi avaliada por teste de microtração. Os dados foram submetidos a ANOVA a dois fatores e Teste de Tukey (α=0,05). Isolando o tipo de fotoiniciador, não houve diferenças significativas na BS. Três cimentos mostraram diferenças significativas: a BS foi maior para P5 e C5 com QTH; e para C4P1 com LED. Para a QTH, P5 exibiu a maior e C1P4 a menor BS. Para LED, C4P1 exibiu a maior BS de todos os outros cimentos testados. Conclusão: PPD é altamente viável em formulações de cimentos resinosos fotopolimerizáveis, reduzindo ou eliminando a CQ que é amarelada, sem comprometer a resistência de união. Além disso, tanto LED quanto QTH são efetivas para polimerizar os cimentos contendo PPD ou CQ.

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.

Influence of photoinitiators and light sources on the degree of conversion of experimental resin cements / Influência de fotoiniciadores e fontes de luz no grau de conversão de cimentos resinosos experimentais

Objetivo: O objetivo deste estudo foi avaliar o grau de conversão (DC) de sete cimentos resinosos experimentais formulados com diferentes fotoiniciadores, quando ativados por duas fontes luminosas (LCUs) atravessando a cerâmica. Material e Métodos: Sete formulações foram preparadas com diferentes concentrações (em peso) de Canforoquinona (CQ) e/ou Fenilpropanodiona (PPD): C5: 0,5% CQ; C8: 0,8% CQ; P5: 0,5% PPD; P8: 0,8% PPD; C1P4: 0,1% CQ e 0,4% PPD; C4P1: 0,4% CQ e 0,1% PPD; e C4P4: 0,4% CQ e 0,4% PPD. Cada mistura foi carregada com 65% em peso de partículas de carga silanizada. Foram usadas duas fontes luminosas para a fotoativação: uma de luz halógena de quartzo-tungstênio (QTH) e uma de diodo emissor de luz (LED). A irradiância (mW/cm²) foi calculada pela potência média de saída dividida pela área da ponta do aparelho. DC foi obtido por espectroscopia de infravermelho transformada de Fourier. Os dados foram submetidos a ANOVA 2-Fatores e ao teste de Tukey (5%). Resultados: Os valores de DC não exibiram diferenças significativas para LCUs, independente do tipo de fotoiniciador. O maior DC foi observado para o cimento P8, e o menor para C5. Valores intermediários de DC foram observados nos demais cimentos. No entanto, quando usado QTH, P8 diferiu dos cimentos C1P4, C4P1 e C5; e quando o LED foi empregado, P8 diferiu apenas de C4P1 e C5. Conclusão: Portanto, PPD é uma alternativa viável para o desenvolvimento de cimentos resinosos fotoativados, e a associação PPD/CQ também pode ser viável, uma vez que C4P4 foi semelhante a P8.

Objective: The aim of this study was to evaluate the degree of conversion (DC) ofseven experimentalresin cements formulated with different photoinitiators when activated by two light-curing units (LCUs) through ceramic material. Material and Methods: Seven resin blends with different camphorquinone (CQ) and/or phenyl propanedione (PPD) ratios were prepared: C5: 0.5% wt CQ; C8: 0.8% wt CQ; P5: 0.5% wt PPD; P8: 0.8% wt PPD; C1P4: 0.1% wt CQ and 0.4% wt PPD; C4P1: 0.4% wt CQ and 0.1% wt PPD; and C4P4: 0.4% wt CQ and 0.4% wt PPD. Each mixture was loaded with 65% wt of silanized filler particles. For photoactivation procedures, two LCUs were used: a quartz-tungsten-halogen (QTH) and a light emitting diode (LED). Irradiance (mW/ cm²) was calculated by the ratio of the output power by the area of the tip. DC was assessed by Fourier transformed infrared spectroscopy. Data were submitted to a two-way ANOVA and Tukey’s test (5%). Results: DC values do not show significant differences for LCUs regardless of the photoinitiator type. The highest DC was found for experimental cement P8 and the lowest for C5. Intermediate DC values were found for the other cements. However, when QTH was used, P8 exhibited differences among C1P4, C4P1 and C5; whereas when LED was used, P8 differed only for C4P1 and C5. Conclusion: Thus, PPD is a viable alternative for the manufacture of photoactivated cements, and the PPD/CQ association may also be viable since C4P4 was similar to P8.

Photoelastic evaluation of the effect of composite formulation on polymerization shrinkage stress

We compared polymerization stress in two commercial composites and three experimental composites made using camphorquinone (CQ) and/or phenylpropanedione (PPD) as photoinitiators. The internal surfaces of photoelastic resin discs with cylindrical cavities were roughened and treated with adhesive. Composites were divided into five groups: two commercial composites (Filtek Silorane and Filtek Z250) and three experimental composites with CQ/amine, CQ/PPD/amine, and PPD/amine. Composites were photopolymerized inside cavities, and subjected to photoelastic analysis immediately and at 24 hours and 7 days later using a plane polariscope. Stress created by Silorane (3.08 ± 0.09 MPa) was similar to that of Z250 (3.19 ± 0.13 MPa) immediately after photopolymerization (p > 0.05). After 24 hours and 7 days, Z250 (3.53 ± 0.15 and 3.69 ± 0.10 MPa, respectively) showed higher stress than Silorane (3.19 ± 0.10 and 3.16 ± 0.10 MPa, respectively). Qualitative analysis immediately after photopolymerization showed composite/CQ promoted higher stress than PPD, but stress levels at other evaluated times were statistically similar, varying between 3.45 ± 0.11 MPa and 3.92 ± 0.13 MPa. At 24 hours and 7 days, Silorane created the lowest stress. All photoinitiators created comparable tensions during polymerization.

Influence of different light sources on the conversion of composite resins.

Aims: The purpose of this paper was to evaluate the influence of different light curing units on the conversion of four composite resins with different compositions (Durafill VS® - Heraeus-Kulzer, Tetric Ceram® - Ivoclar/Vivadent, Filtek™ Supreme XT - 3M ESPE™ e Aelite™ LS Packable - Bisco), using differential scanning calorimetry. Materials and Methods: A stainless steel matrix was used to prepare 48 cylindrical composite test samples (n=6), measuring 3 mm in diameter and 1 mm in thickness. The samples were photoactivated using a halogen lamp (Optilux™ 500 - Demetron/Kerr) and three different generations of light-emitting diodes (LEDs) (LEC-470 I - MMOptics, Radii Plus - SDI and Ultra-Lume™ LED 5 - Ultradent). After removal of the matrix, each sample was weighed and hermetically sealed in an aluminum pan and analyzed. The amount of heat liberated by thermopolymerisation of residual monomers after photoactivation was measured in Joules/gram (J/g). The data were submitted to Analysis of Variance (ANOVA) test (P ≤ 0.002) and the Tukey test (P < 0.05). Results: The Ultra-Lume™ LED 5 was superior on degree of conversion for all resins. The Radii Plus was equal to the Ultra-Lume™ LED 5, except for the resin Tetric Ceram® , were the Optilux™ 500 was superior. The LEC-470 I was inferior for the conversion of all resins. Conclusion: The study proves the importance of the compatibility of the different photoinitiators in resin composites with the different light sources.

Effect of the difference in spectral outputs of the single and dual-peak LEDs on the microhardness and the color stability of resin composites / 대한치과보존학회지

OBJECTIVES: To determine the effect of the spectral output of single and dual-peak light emitting diode (LED) curing lights on the microhardness and color stability of commercial resin composites formulated with camphorquinone and alternative photoinitiators in combination. MATERIALS AND METHODS: Three light-polymerized resin composites (Z100 (3M ESPE), Tetric Ceram (Ivoclar Vivadent) and Aelite LS Posterior (Bisco)) with different photoinitiator systems were used. The resin composites were packed into a Teflon mold (8 mm diameter and 2 mm thickness) on a cover glass. After packing the composites, they were light cured with single-peak and dual-peak LEDs. The Knoop microhardness (KHN) and color difference (DeltaE) for 30 days were measured. The data was analyzed statistically using a student's t-test (p < 0.05). RESULTS: All resin composites showed improved microhardness when a third-generation dual-peak LED light was used. The color stability was also higher for all resin composites with dual-peak LEDs. However, there was a significant difference only for Aelite LS Posterior. CONCLUSIONS: The dual-peak LEDs have a beneficial effect on the microhardness and color stability of resin composites formulated with a combination of camphorquinone and alternative photoinitiators.