Assessment of influence of LED curing units used on microhardness of resin-modified glass ionomer sealants

Aim: Resin modified glass ionomer (RMGI) is class of material that can be used as sealant for preventing and arresting the progression of caries in pits and fissures. As these are hybrid materials, their properties can be affected by factors related to the polymerization process. Therefore, this study aimed to evaluate the influence of different generations of LED curing units (Elipar DeepCure-L and VALO Grand) on Knoop microhardness values (KHN) of RMGI sealants (Clinpro XT and Vitremer). Methods: Forty cylindrical specimens (6mm ø x 1 mm high) were prepared according to the manufacturer's instructions and divided into four groups (n=10) according to the type of RMGI and LED used. The KHN of the top surface of each sample was calculated 7 days after light-curing. Data were submitted to two-way ANOVA (α = 0.05). Results: Vitremer had higher KHN values than Clinpro XT after using both LEDs (p<0.0001), but especially when light-cured with the use of VALO Grand (p<0.0001). Whereas the KHN value of Clinpro was not influenced by the LED device (p>0.05). Conclusions: Top surface microhardness values of RGMI sealants were affected by both material composition and generations of LED curing units used. Third generation LED curing units seemed to be more efficient for the polymerization of RMGI-based sealants

Effect of conventional and power office bleaching with diode laser and led light on enamel microhardness

Aim: The present study aimed to asses enamel microhardness after office bleaching with diode laser and LED light compared to the conventional bleaching procedure. Methods: Thirty-nine human premolar teeth were collected and randomly divided into three groups regarding of the bleaching technique. Group 1: Snow O bleaching gel with LED light-curing unit; Group 2: Snow L bleaching gel with diode laser irradiation; and Group 3: Opalescence Boost bleaching gel with no light source in group 3. Enamel surface changes were evaluated in one tooth in each study group and one intact tooth as a reference under a scanning electron microscope (SEM). In the remaining samples (n=12), enamel microhardness was determined by Vickers microhardness test before and after bleaching. Data were analyzed with repeated-measures ANOVA to compare microhardness changes, followed by post hoc Tukey tests at the 0.05 significance level. Results: Enamel microhardness decreased in all the groups after bleaching, with the maximum decrease in microhardness in the Snow O bleaching group with LED light, which was significantly higher than the other groups (P=0.002). The two other groups did not exhibit any significant difference in microhardness decrease (P>0.05). Conclusion:Based on the limitations of this study, it can be concluded power bleaching with 980nm diode laser was less time-consuming compare to conventional bleaching procedure and yielded better outcomes in terms of enamel surface microhardness compared to the use of an LED light-curing unit

Influência de um novo dispositivo acessório de fotopolimerização com fibra óptica e pino de fibra de vidro experimental nas propriedades mecânicas, físicoquímicas e adesão dos cimentos resinosos / Influence of a new light curing device with optical fiber and an experimental glass fiber post on the physicochemical, mechanical properties and adhesion of resin cement

O objetivo deste estudo foi avaliar in vitro a influência de um novo dispositivo fotopolimerização e pino de fibra de vidro nas propriedades mecânicas, físicoquímicas e adesão dos cimentos resinosos. Foram utilizados oitenta dentes bovinos, submetidos ao tratamento endodôntico, distribuídos em 5 grupos (n=16): CD (Pino fibra vidro e cimento dual); PF (Pino perfurado e cimento fotoativado); PD (Pino perfurado e cimento dual); POF (Pino perfurado iluminador de fibra óptica e cimento fotoativado); POD (Pino perfurado iluminador de fibra óptica e cimento dual). Os dentes foram preparados para colocação de um protótipo de pino em fibra de vidro que possui um canal interno de diâmetro regular e com conicidade progressiva. A perfuração permite a inserção da fibra óptica ao longo da extensão do pino a fim de possibilitar a ação da luz ao longo de todo o comprimento do conduto radicular. Após a cimentação, os espécimes foram seccionados perpendicularmente, e obtida 1 fatia de 2 mm de espessura do terço apical, médio e cervical. A avaliação mecânica foi realizada através do ensaio de push-out para determinação da resistência adesiva nos terços cervical, médio e apical seguido pela análise da fratura em estereomicroscópio. Os retentores intrarradiculares foram também submetidos ao teste de flexão de 3 pontos para análise do material preenchedor do pino de fibra (n=10). As análises físico - químicas foram realizadas através da determinação do grau de conversão dos cimentos (RAMAN) e análise em espectroscopia de energia dispersiva (EDS) dos monômeros presentes. A adesão foi analisada pela interface de cimentação pelo MEV e reconstrução 3D do novo sistema através do Micro-CT. Os dados obtidos foram analisados estatisticamente pelo ANOVA (um e dois fatores) e comparação múltipla de Tukey, (p<0,05). Os resultados de resistência adesiva evidenciaram que o terço apical obteve o maior valor de resistência adesiva em comparação ao terço médio (p<0,001), o grupo POD do terço apical foi estatisticamente significante em relação ao grupo CD do terço médio (p<0,001). Na analise individual de cada terço, não houve diferença entre os grupos experimentais e o controle (p>0,05). A falha adesiva entre cimento e dentina foi a mais predominante entre todos os grupos e terços. O pino de fibra de vidro (controle) obteve o maior valor de resistência à flexão (p<0,001), seguido do pino de fibra de vidro perfurado preenchido com cimento resinoso (p<0,001). Os maiores valores de GC foram alcançados pelo grupo POD com 82,3% (cervical) 69,9 % (médio) e 76,21% (apical) e o EDS comprovou a presença de componentes químicos adequados. A análise da adesão do novo pino de fibra de vidro comprova uma excelente adaptação no interior do canal radicular nas regiões cervical, médio e apical. Portanto o novo dispositivo com fibra óptica e pino de fibra de vidro experimental aumentaram as propriedades mecânicas, físico-químicas e adesão do cimento resinoso (AU)

The aim of this study was to evaluate in vitro the influence of a new light curing device with optical fiber and experimental glass fiber post on the physicochemical, mechanical, and adhesion properties of resin cements. Eighty bovine teeth were used, submitted to an endodontic treatment, distributed in 5 groups (n=16): CD (Glass fiber post and dual cement); PF (Perforated post and light-cured cement); PD (Perforated post and dual cement); POF (Fiber optic illuminating with a perforated post and lightcured cement); POD (Fiber optic illuminating with a perforated post and dual cement). The teeth were prepared for placement of a glass fiber post prototype, which has an internal canal of regular diameter and progressive taper. The internal perforation extension allows the insertion of the optical fiber along the entire length of the post in order to allow the action of light along the entire length of the root canal.The specimens were sectioned perpendicularly for the tests, and 1 slice approximately 2 mm thick was obtained from the apical, middle and cervical thirds. The mechanical evaluation was carried out through the push-out test to determine the adhesive bond strength, in the cervical, middle and apical thirds, followed by the fracture analysis under a stereomicroscope, the intraradicular post were also submitted to the 3-point bending test for material analys of the fiber post filler (n=10). The physicochemical analyzes were performed by determining the degree of conversion of the cements (RAMAN) of each sample and the analysis of energy dispersive spectroscopy (EDS) of the monomers present. Adhesion was analyzed by the cementation interface and 3D reconstruction of the new system through micro-CT, and finally, SEM analysis of the adhesive interface. The data obtained were analyzed for normality and statistically by ANOVA (one and two ways) and Tukey's multiple comparison (p<0.05). The adhesive bond strength results showed that the apical third had the highest value of adhesive strength compared to the middle third (p<0.001), and the POD group of the apical third was statistically significant in relation to the CD group of the middle third (p<0.001). In the individual analysis of each third, there was no difference between the experimental and control groups (p>0.05). Adhesive failure between cement and dentin was the most prevalent among all groups and thirds. The conventional post (control) had the highest flexural strength value (p<0.001), followed by the perforated fiberglass post filled with resin cement (p<0.001). The POD group achieved the highest GC values with 82.3% (cervical), 69.9% (medium), and 76.21% (apical) and EDS confirmed the presence of adequate chemical components. The analysis of the adhesion of the new fiberglass post proves an excellent adaptation inside the root canal in the cervical, middle and apical regions. Therefore, the new light curing device with optical fiber and experimental glass fiber post improved the resin cement's mechanical, phycochemical, and adhesion. (AU)

Novo sistema de retentor pré-fabricado perfurado e de iluminador em fibra óptica: estudo da resistência mecânica frente a variação dos cimentos resinosos / New system of hollow prefabricated post and optical fiber illuminator: study of the mechanical strength by varying resin cements

O presente estudo teve por objetivo avaliar a resistência à flexão de um pino experimental de fibra de vidro vazado, e a resistência adesiva entre este pino experimental à dentina radicular, associando a utilização de um dispositivo iluminador em fibra óptica, sob o processo de envelhecimento, além de determinar a distribuição de tensão pela Análise de Elementos Finitos (FEA). O pino experimental e o dispositivo iluminador de fibra óptica têm por finalidade aumentar a efetividade de fotoativação dos cimentos resinosos nos terços médios e apicais dos canais radiculares. Para o teste de flexão de 3 pontos, estritamente do pino de fibra de vidro, as amostras foram divididas em 4 grupos (n=10): pino convencional (pc), pino experimental sem preenchimento (pp), com preenchimento de cimento resinoso (ppc) e com preenchimento de fibra óptica (ppf). Para o teste de resistência adesiva Pull-out, 100 raízes de dentes bovinos foram restauradas com retentores intrarradiculares e coroas de resina composta, distribuídos em 10 grupos (n=10), tendo como variáveis: o tipo de pino de fibra de vidro [convencional (C) ou perfurado (P)], o sistema de fotoativação [com ou sem o iluminador de fibra óptica (O)], o tipo de cimento resinoso [fotoativado (F) ou polimerização dual (D)] e o envelhecimento das amostras [com e sem ciclagem mecânica (C)]. O processo de envelhecimento foi realizado através da ciclagem mecânica e as amostras foram submetidas ao teste de resistência adesiva Pull-out. A análise do modo de falha foi realizada em Estereomicroscópio. A Análise em Elementos Finitos avaliou a distribuição de tensão pela análise de von Mises, deformação total e tensão máxima principal no Software Ansys 19.3. A análise estatística foi constituída pelo teste de normalidade Shapiro-Wilk, análise de variância (ANOVA) 1, 2 e 3 fatores e teste Tukey 5%. As médias e desvios padrão de resistência à flexão foram (MPa): pc = 677 ± 81,1; ppc = 419 ± 23,2; ppf = 200 ± 32,5 e pp = 177 ± 32,8. As médias e desvios padrão de resistência adesiva foram (MPa): CD = 12,2 ± 1,21; PD = 11,1 ± 1,32; PF = 10,9 ± 1,29; POD = 13,7 ± 1,16; POF = 11,9 ± 1,48; CDC = 10,1 ± 1,33; PDC = 9,25 ± 1,11; PFC = 8,37 ± 1,25; PODC = 10,8 ± 0,95 e POFC = 9,82 ± 1,02. Os resultados do modo de falha foram: adesiva entre pino e cimento (56%), mista predominantemente adesiva entre cimento e dentina (22%), adesiva entre cimento e dentina (14%) e a mista predominantemente adesiva entre pino e cimento (8%). Concluiu-se que entre os pinos experimentais, o grupo do pino perfurado preenchido com cimento resinoso obteve o maior valor de resistência à flexão, a utilização do dispositivo iluminador aumentou os resultados de resistência adesiva nos grupos dos pinos perfurados e não houve diferença na distribuição de tensões entre os grupos. (AU)

The present study aimed to evaluate the flexural strength of an experimental hollow glass fiber post, and the bond strength between this experimental post and root dentin, associating the use of an optical fiber illuminating device, under the aging process, in addition to determine the stress distribution by Finite Element Analysis (FEA). The experimental post and optical fiber illuminating device are intended to increase the polymerization effectiveness of resin cements in the middle and apical regions of root canals. For the 3-point bending test, strictly of the fiber post, the samples were divided into 4 groups (n=10): conventional post (pc), experimental post without filling (pp), with resin cement filling (ppc) and with optical fiber filling (ppf). For the Pull-out test, 100 roots of bovine teeth were restored with intraradicular retainers and composite resin crowns, distributed into 10 groups (n=10), with the following variables: glass fiber post type [conventional (C) or hollow (P)], the photocuring system [with or without the optical fiber illuminating device (O)], the type of resin cement [light cured (F) or dual cured (D)] and aging of the samples [with and without mechanical cycling (C)]. The aging process was performed by mechanical cycling and the samples were submitted to the Pull-out bond strength test. Failure mode analysis was performed using a stereomicroscope. Finite Element Analysis evaluated the stress distribution by von Mises analysis, total strain and maximum principal stress in Ansys Software 19.3. Statistical analysis consisted of the Shapiro-Wilk normality test, 1-, 2- and 3-way analysis of variance (ANOVA) and Tukey test 5%. The means and standard deviations of flexural strength were (MPa): pc = 677 ± 81.1; ppc = 419 ± 23.2; ppf = 200 ± 32.5 and pp = 177 ± 32.8. The means and standard deviations of bond strength were (MPa): CD = 12.2 ± 1.21; PD = 11.1 ± 1.32; PF = 10.9 ± 1.29; POD = 13.7 ± 1.16; POF = 11.9 ± 1.48; CDC = 10.1 ± 1.33; PDC = 9.25 ± 1.11; PFC = 8.37 ± 1.25; PODC = 10.8 ± 0.95 and POFC = 9.82 ± 1.02. The failure mode results were: adhesive between post and cement (56%), mixed predominantly adhesive between cement and dentin (22%), adhesive between cement and dentin (14%) and mixed predominantly adhesive between post and cement (8 %). It was concluded that among the experimental posts, the hollow post group filled with resin cement obtained the highest flexural strength value, the use of the illuminating device increased the results of bond strength in the hollow post groups and there was no difference in the stress distribution among the groups (AU)

Effect of Light-Curing Unit Type and Bulk-Fill Composite Resins with Different Photoinitiators on Marginal Gaps of Class II Restorations

Abstract Objective: To evaluate the effect of two types of light-curing units (second and third generations) and two types of bulk-fill composite resins with different photoinitiators - Tetric N-Ceram Bulk Fill (TNCB) and Xtra Fil (XTF) on gap formation at the gingival margins of Cl II restorations. Material and Methods: Fifty-six standard Cl II cavities were prepared on the mesial and distal surfaces of premolar teeth, with the gingival margin of the cavities 1 mm apical to the CEJ. The samples were randomly assigned to two groups based on the composite resin type and two subgroups based on the light-curing unit type and restored. After 5000 rounds of thermocycling, gingival margin gap in each sample was measured in µm under an electron microscope at ×2000 magnification. Data were analyzed by two-way ANOVA and Tukey tests (α=0.05). Results: Marginal gaps of TNCB composite resin were significantly smaller than those of XTF composite resin (p<0.001). There were no significant differences between the two light-curing units in each group (p=0.887 with XTF and p=0.999 with TNCB). Conclusion: The gaps at gingival margins of Cl II cavities with TNCB bulk-fill composite were smaller than XTF composite resin. Both composite resins can be cured with both the second- and third-generation LEDs (AU).

Fuentes de luz de uso clínico en el pre grado: 7 años de seguimento / Light curing units in the undergraduate dental clinics: 7 years of follow-up

RESUMEN Objetivo: Realizar, durante siete años ininterrumpidos, un control y seguimiento de las fuentes de luz disponibles en las clínicas odontológicas de pre graado de una Institución de Enseñanza Superior Pública Brasileña. Material y métodos: Durante el período comprendido entre 2011-2017 se evaluó el control de calidad de las fuentes de luz de la Facultad de Odontología de la Universidad Federal de Goiás a través del análisis de su estado de conservación y de su densidad de potencia (mW/cm2). Los datos obtenidos se sometieron a un análisis estadístico descritpivo y a las pruebas de Levene, Shapiro-Wilk, Kruskal-Wallis, Dunn y Chi-cuadrado (P<0,05). Resultados: No se observaron diferencias estadísticas significativas del estado de conservación de las fuentes de luz entre los años 2012, 2016 y 2017 (p>0,05). Sí se observaron diferencias estadísticas significativas entre los valores de densidad de potência entre dichos años (p<0,0001). En las comparaciones por pares, los valores de densidad de potencia para los años 2011 (p<0,01) y 2012 (p<0,05) fueron estadísticamente diferentes de los años 2015, 2016 y 2017. Conclusiones: Comparativamente se observó una mejora sustancial del estado de conservación de las fuentes de luz en los cuatro años iniciales de evaluaciones, con una disminución en el quinto año y una estabilización en los dos últimos años. Durante los siete años de estudio de la densidad de potencia de las fuentes de luz se observó en un aumento gradual de la misma con una estabilización de los resultados a partir del quinto año de control de calidad.

SUMMARY Objetive: To monitor the light curing units available at undergraduate dental clinics of a Brazilian Public Higher Education Institution for seven uninterrupted years. Materials and methods: In the period between 2011-2017, the quality control of light curing units at the Faculty of Dentistry, Federal University of Goiás, was evaluated by analyzing their state of conservation and power density (mW/cm2). Data obtained were subjected to descriptive statistical analysis and Levene, Shapiro-Wilk, Kruskal-Wallis, Dunn and Chi-square tests (P <0.05). Results: Regarding the conservation status of the light curing units, comparatively, there was no statistically significant difference between the years 2012, 2016 and 2017 (p> 0.05). Statistically significant differences were found for power density values between years (p <0.0001). In pairwise comparisons, the power density values for the years 2011 (p <0.01) and 2012 (p <0.05) were statistically different from the years 2015, 2016 and 2017. Conclusions: A significant improvement in the state of conservation of light curing units was observed in the initial four years of evaluations, with a decline in the fifth year and stabilization in the last two years. Regarding the power density of the light curing units, a gradual increase was observed in the seven years of study, with stabilization of the results after the fifth year of quality control.

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 radiant exposure values from two third generation LED curing units on polymerization profile and microhardness of orthodontic composite under ceramic and metallic brackets

ABSTRACT Introduction: Third generation of LED light curing units might be used in short exposure periods for orthodontic brackets bonding. Objective: This study evaluated the effect of the different radiant exposure (RE) values: Manufacturers' instructions (MI), ½ MI, 1/4 MI and Turbo mode. Two third-generation LED curing units were used: VALO® and Bluephase 20i® . The degree of conversion (DC) and Vickers hardness (VHN) of an orthodontic composite (OC) (Transbond XT) under metallic (MB) or ceramic brackets (CB) were measured. Methods: OC was applied to the bracket base, which was then placed over an attenuated total reflectance (ATR) table coupled to an infrared light spectroscope, or to a glass surface for the VHN analysis. The specimens were light-cured and DC values were calculated. The VHN was obtained in a microhardness tester. The data were analyzed with 2-way ANOVA followed by Tukey's post-hoc test (pre-set α=0.05). Linear regression analysis evaluated the relationship between RE values and dependent variables. Results: CB allowed higher DC and VHN values than MB (p< 0.001). No significant difference was noted among groups when CB were used. For MB, MI groups showed the highest DC and VHN values. A significant, but weak relationship was found between delivered RE values and dependent variables. Conclusions: The decrease in RE values from third generation LED CU did not jeopardize the DC values when CB were used, but can compromise DC and VHN values when MB are used.

RESUMO Introdução: A terceira geração de LEDs fotopolimerizadores pode ser utilizada em curtos períodos de exposição para a colagem de braquetes ortodônticos. Objetivo: O presente estudo avaliou o efeito dos diferentes valores de irradiância (IR): instruções do fabricante (IF), ½ IF, » IF e modo Turbo. Dois fotopolimerizadores LED de terceira geração (VALO® e Bluephase20i®) foram utilizados. Foram mensurados o grau de conversão (GC) e a dureza Vickers (VHN) de um compósito ortodôntico (CO) (Transbond XT) sob braquetes metálicos (BM) ou cerâmicos (BC). Métodos: O compósito ortodôntico foi aplicado na base do braquete e foi posicionado sobre uma mesa de refletância total atenuada (ATR) acoplada a um espectroscópio de infravermelho ou a uma superfície de vidro para análise de VHN. As amostras foram fotopolimerizadas e os valores de GC foram calculados. O VHN foi obtido em um microdurômetro. Os dados foram analisados com ANOVA de 2 fatores seguida do teste post-hoc de Tukey (predefinido α = 0,05). A análise de regressão linear avaliou a relação entre os valores de IR e as variáveis dependentes. Resultados: BC permitiu valores maiores de GC e VHN do que BM (p<0,001). Nenhuma diferença significativa foi observada entre os grupos quando BC foi utilizado. Para BM, os grupos de IF mostraram os maiores valores de GC e VHN. Uma relação significativa, mas fraca, entre os valores de IR entregue e as variáveis dependentes foi encontrada. Conclusões: A diminuição dos valores de IR dos fotopolimerizadores LED de terceira geração não prejudicou os valores de GC quando BC foram utilizados, mas pode comprometer os valores de GC e VHN quando BM são utilizados.

Produção científica em laser / LED na odontologia brasileira no período de 2015 a 2019 / Scientific production in laser / LED in Brazilian dentistry from 2015 to 2019

Objetivo:Investigar o perfil das publicações brasileiras em laser/LED de 2015 a 2019. Métodos: Foi realizado um estudo observacional, por meio de documentação indireta, através da análise dos trabalhos apresentados nas reuniões do SBPqO de 2015 a 2019. Os estudos foram classificados quanto à instituição de ensino dos pesquisadores, estado de origem da pesquisa, especialidade odontológica e tipo de estudo. Resultados: Foram identificados 563 resumos. A maior parte foi concentrada em 2019 (21,7%), sendo os lasers operando em baixa potência os mais utilizados (54,1%). O Estado de São Paulo concentrou a maioria dos resumos (67,3%), com a região Sudeste contendo o maior número de trabalhos (76,9%). Em relação à instituição de ensino, as universidades estaduais produziram a maioria dos estudos (47.8%). A especialidade de Dentística foi a que mais realizou pesquisas em laser/LED (21,7%). A maioria dos resumos (73,7%) era do tipo de pesquisa laboratorial básica. A maioria dos trabalhos selecionados não recebeu apoio financeiro (54,7%). Dentre as agências financiadoras mencionadas, as Fundações de Amparo à Pesquisa foram as mais prevalentes (26,6%). Grande parte dos trabalhos não citou o Comitê de Ética em Pesquisa (97,5%). Houve associação estatisticamente significativa entre as instituições públicas e o recebimento de fomento (p < 0,005). Conclusão: A maior parte dos resumos foi concentrada em 2019, com maior número de pesquisas no Estado de São Paulo, realizadas em instituições Públicas e na especialidade de Dentística. Foi observado um número maior de estudos do tipo laboratorial. Além disso, a maioria dos estudos não recebeu fomento para pesquisa.

Aim: To determine the profile of Brazilian publications in laser/ LED from 2015 to 2019. Methods: A retrospective observational study was conducted, using indirect documentation to analyze the papers presented at SBPqO meetings from 2015 to 2019. Results: 563 abstracts involving the use of laser/LED were evaluated and subsequently classified according to higher education research institution, state where the research was conducted, dental specialty, and type of study. Most of the abstracts involving the laser/LED were concentrated in 2019 (21.7%), with low-power lasers being the most frequently used (54.1%). Most of the abstracts were concentrated in the State of São Paulo (67.3%), with the Southeast region containing the largest number of works (76.9%). Regarding the higher education institution, the state universities produced a larger number of the studies (47.8%). Restorative dentistry was the specialty that most developed studies in the laser/LED area (21.7%). Most abstracts (73.7%) were classified as basic laboratory research. Most of the selected studies received no financial support (54.7%). Among the funding agencies mentioned, the Research Support Foundations were the most prevalent (26.6%). Most studies did not mention the Research Ethics Committee (97.5%). There was a statistically significant association between public institutions and the receipt of funding (p < 0.005). Conclusion: Most of the abstracts were identified in 2019, with a greater number of studies conducted in the State of São Paulo, in state institutions across the country, and in the specialty area of restorative dentistry. Laboratory-type studies were the most prevalent. Moreover, most studies received no funding for research.

Effect of flowable composite or glass ionomer liners on shrinkage stress of a composite resin / Efecto de recubrimientos con resinas de baja viscosidad o ionómero vitreo sobre la tensión por contracción de una resina compuesta

ABSTRACT The aim of this study was to evaluate the effect of flowable composite or glass ionomer liners on the shrinkage stress of a restorative composite resin. Fifteen previously sandblasted metal boxes were attached to a universal mechanical testing machine (INSTRON 1011, Instron Corporation). Five of these boxes were filled with Filtek Z350 XT (FXT) Universal Restorative A2 (3M ESPE) (Group 1 or Control). Two further groups of 5 boxes were prepared by interposing a layer of Vitrebond Light Cure Glass Ionomer 3M ESPE (VGI) (Group 2 or G.I.) or Filtek Z350 XT Flowable Restorative A2 3M ESPE (FFR) (Group 3 or Flowable) between the box and the composite resin, completing with the same volume of composite as in Group 1. Upon activating lightcuring, the filled boxes mounted on the testing machine were videoed for 60 seconds (40 s photoactivation and 20 s postcuring), timed with a digital chronometer. Force values were recorded in newtons and converted into stress according to contact surface. Stress values were recorded every 10 s. Results were analyzed using repeated measures ANOVA. Mean and standard deviation in kPa (stress) recorded for each group were: Control group: 126.2 (30.8); G.I.: 48.4 (18); Flowable: 27.9 (19.5). Statistical analysis showed significant differences between the control group and the rest (p<0.01), with no significant difference between groups with glass ionomer liners and flowable resin liners (G.I. and Flowable). Under the experimental conditions of this study, it can be concluded that polymerization shrinkage stress can be reduced by the presence of a liner between the preparation and the restorative material.

RESUMEN El objetivo de este trabajo fue evaluar el efecto de la colocación de una capa de Composite flow o Ionómero vítreo sobre la tensión de contracción de un composite para restauración. Se utilizaron 15 cajas metálicas previamente arenadas y conectadas a la máquina universal para ensayos mecánicos (INSTRON 1011, Instron Corporation). Cinco de estas cajas (G1) se rellenaron con Filtek Z350 XT (FXT) Universal Restorative A2 3M ESPE. Al iniciar la activación de la unidad de curado se comenzaba a registrar con una cámara de video y un cronómetro digital desde el comienzo de la activación de la lámpara hasta 60 s después, registrando los valores post curado durante 20 s. Los valores de fuerza generados por la polimerización fueron registrados en newton de cada 10 s para los 15 ensayos. Los valores fueron convertidos en tensión de contracción según la superficie de contacto. Se realizaron además dos grupos de cajas (5 en cada una) en los cuales se colocaron una capa inicial de Vitrebond Light Cure Glass Ionomer 3M ESPE (VGI) (G2 o IV) y Filtek Z350 XT Flowable Restorative A2 3M ESPE (FFR) (G3 o Flow) y se completó con el mismo volumen de composite de las del GI. Los resultados obtenidos fueron analizados por medio de ANOVA para mediciones repetidas. La media y la desviación estándar en kPa (tensión o estrés de contracción) registrado para cada grupo fueron: Grupo control: 126.2 (30.8); IV: 48.4(18); Flow: 27.9(19.5). El análisis estadístico mostró diferencias estadística mente significativas entre el grupo control y el resto (p=0.00), pero no hubo diferencias significativas entre la presencia de Ionómero vítreo o Composite Flow (IV y Flow). En las condiciones experimentales de este trabajo puede concluirse que la tensión de contracción generada durante la polimerización puede ser disminuida por la presencia de algún material interpuesto entre la preparación y el composite restaurador.

Accuracy of irradiance and power of light-curing units measured with handheld or laboratory grade radiometers

Abstract This study measured and compared exitance irradiance and power of 4 commercial dental light-curing units (LCU) (Elipar S10, Elipar DeepCure-S, Corded VALO and Bluephase Style) using different types of radiometers. The devices used to analyze the LCU were classified as either handheld analog (Henry Schein, Spring, Demetron 100A, Demetron 100B and Demetron 200), handheld digital (Bluephase 1, Bluephase II, Coltolux, CureRite and Hilux), or laboratory instruments (Thermopile and Integrating Sphere). The laboratory instruments and the Bluephase II radiometer were also used to measure the LCU's power (mW). The LCU's were activated for 20 s (n=5). Data were analyzed using Kruskal-Wallis and Student-Newman-Keuls multiple comparison test (a=0.05). Among the LCU, the laboratory instruments presented different irradiance values, except for Corded VALO. The Coltolux and Hilux radiometers measured greater irradiance values compared to the laboratory instruments for the four LCUs tested. Within a given LCU, handheld analog units measured lower irradiance values, compared to handheld digital and laboratory instruments, except using the Spring radiometer for the Elipar S10 LCU. None of the handheld radiometers were able to measure similar irradiance values compared to laboratory instruments, except for Elipar S10 when comparing Bluephase 1 and Thermopile. Regarding power measurement, Bluephase II always presented the lowest values compared to the laboratory instruments. These findings suggest that the handheld radiometers utilized by practitioners (analog or digital) exhibit a wide range of irradiance values and may show lower outcomes compared to laboratory based instruments.

Resumo Esse estudo mensurou e comparou a irradiância e a energia de quatro fotopolimerizadores comerciais (Elipar S10, Elipar DeepCure-S, Corded VALO e Bluephase Style) utilizando diferentes tipos de radiômetros. Os dispositivos utilizados para analisar os fotopolimerizadores foram classificados em portáteis analógicos (Henry Schein, Spring, Demetron 100A, Demetron 100B e Demetron 200), portáteis digitais (Bluephase 1, Bluephase II, Coltolux, CureRite e Hilux), ou instrumentos laboratoriais (Thermopile e Integrating Sphere). Os instrumentos laboratoriais e o radiômetro Bluephase II também foram utilizados para medir a energia dos fotopolimerizadores (mW). Os fotopolimerizadores foram ativados por 20 s (n=5). Os dados foram analisados utilizando Kruskal-Wallis e teste de Student-Newman-Keuls (a=0,05). Dentre os fotopolimerizadores, os instrumentos laboratoriais apresentaram diferentes valores de irradiância, exceto para o Corded VALO. O Coltolux e o Hilux mensuraram uma irradiância maior comparado aos instrumentos de laboratório para os quatro fotopolimerizadores testados. Para o mesmo fotopolimerizador, os radiômetros analógicos portáteis mensuraram menores valores de irradiância quando comparados aos digitais portáteis ou aos instrumentos laboratoriais, exceto quando utilizado o Spring para o Elipar S10. Nenhuma diferença foi observada entre os instrumentos laboratoriais na irradiância do Corded VALO. Para a medição da energia, nenhuma diferença foi observada usando Thermopile e a Integrating Sphere para o Corded VALO. Para os outros fotopolimerizadores, cada instrumento indicou uma energia diferente. Esses achados sugerem que radiômetros portáteis utilizados pelos cirurgiões-dentistas (analógico ou digital) exibem uma ampla gama de valores de irradiância e podem mostrar medidas inferiores comparados aos instrumentos de laboratório.

Evaluation of intensity standards of tungsten-halogen and led curing units / Evaluación de estándares de intensidad de unidades de curado tugsteno-halógenas y leds

Current evidence indicates that the minimum light intensity of photo curing units required to polymerize in a reliable way a composite resin, in increments of 2mm, is 300mW/cm2. The recent introduction of new generations of composite resin materials for large volume increments, partially contrasts with ISO 4049 (2009), calling for the use of light intensity of 1,000mW/cm2. Therefore, it is considered relevant to carry out periodic measurements of the emission intensity of light-curing units of clinical use. The aim of this study was to test the intensity [mW/cm2] of a representative sample of tungsten-halogen and LED photopolymerization units used in private and public health service in different areas of the Valparaíso Region in Chile. This was achieved through the use of dental radiometers, without considering the variables of intensity modification over time (either spontaneously, by undesirable inherent characteristics of the device, or by programs of intensity modification in time), or the density of accumulated power needed. This in vitro diagnostic test, evaluated a sample of 507 units, 107 halogen and 400 LED, for a period of around one month, using two radiometers as measuring instruments. For LED units the Bluephase Meter® radiometer, from Ivoclar-VivadentTM was used, and for halogen units we used the Coltolux® from ColténeTM. As a result, 85% of the LED and halogen units achieved the minimum requirements of intensity needed for the polymerization of conventional dental biomaterials. However, only 25% from the tested units achieved a power density of 1,000mW/cm2.

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)

Comparison of in vivo and in vitro models to evaluate pulp temperature rise during exposure to a Polywave® LED light curing unit

Abstract Objectives: To measure and compare in vivo and in vitro pulp temperature (PT) increase (ΔTEMP) over baseline, physiologic temperature using the same intact upper premolars exposed to the same Polywave® LED curing light. Methodology: After local Ethics Committee approval (#255,945), local anesthesia, rubber dam isolation, small occlusal preparations/minute pulp exposure (n=15) were performed in teeth requiring extraction for orthodontic reasons. A sterile probe of a temperature measurement system (Temperature Data Acquisition, Physitemp) was placed within the pulp chamber and the buccal surface was sequentially exposed to a LED LCU (Bluephase 20i, Ivoclar Vivadent) using the following exposure modes: 10-s low or high, 5-s Turbo, and 60-s high. Afterwards, the teeth were extracted and K-type thermocouples were placed within the pulp chamber through the original access. The teeth were attached to an assembly simulating the in vivo environment, being similarly exposed while real-time temperature (°C) was recorded. ΔTEMP values and time for temperature to reach maximum (ΔTIME) were subjected to two-way ANOVA and Bonferroni's post-hoc tests (pre-set alpha 0.05). Results: Higher ΔTEMP was observed in vitro than in vivo. No significant difference in ΔTIME was observed between test conditions. A significant, positive relationship was observed between radiant exposure and ΔTEMP for both conditions (in vivo: r2=0.917; p<0.001; in vitro: r2=0.919; p<0.001). Conclusion: Although the in vitro model overestimated in vivo PT increase, in vitro PT rise was close to in vivo values for clinically relevant exposure modes.

Irradiance and radiant exposures delivered by led light-curing units used by a left and right-handed operator

Abstract The combination of the restoration location, the hand preference of the operator using the light-curing unit (LCU), and the design of the LCU all can have an impact on the amount of the light delivered to the restoration. To evaluate the effect of left-handed or right-handed users, the position of the operator (dentist or assistant), and the LCU design on the irradiance, radiant exposure and emission spectrum delivered to the same posterior tooth. Two light emitting diode (LED) LCUs were tested: an angulated monowave LCU Radii-Cal (SDI, Victoria, Australia) and a straight aligned multi-peak LCU Valo Cordless (Ultradent, South Jordan, UT, USA). The irradiance values (mW/cm2), radiant exposure (J/cm2) and emission spectrum were measured using a sensor in maxillary left second molar tooth. The irradiance and radiant exposure were analyzed using three-way ANOVA followed by Tukey test (a=0.05). The emission spectra (nm) were analyzed descriptively. The interaction between LCU design, operator position, and hand preference significantly influenced the irradiance and radiant exposure (P<0.001). In all cases, Valo delivered significantly higher irradiance than Radii-Cal. The handedness and the operator position affected the irradiance and radiant exposure delivered from Valo. Operator position and access affect the irradiance and radiant exposure delivered to the maxillary left second molar. The irradiance and radiant exposure can be greater when a right-hand operator is positioned on the right side of the chair and a left-hand operator is positioned on the left side of the chair. This may result in better resin composite polymerization.

Resumo A combinação da localização da restauração, a preferência de mão do operador ao utilizar aparelhos fotopolimerizadores (AFP) com luz emitida por diodo (LED) e o formato do AFP podem afetar a quantidade de luz fornecida à restauração. O objetivo foi avaliar o efeito de operadores canhotos e destros, a posição do operador (dentista ou auxiliar), e o formato do AFP na irradiância, energia radiante e espectro de luz entregue ao mesmo dente posterior. Dois AFP foram testados: um com formato angulado, onda única Radii-Cal (SDI, Victoria, Australia) e um formato reto multi-pico Valo Cordless (Ultradent, South Jordan, UT, USA). Os valores de irradiância (mW/cm²), energia radiante (J/cm²) e espectro de luz foram medidos utilizando um sensor no segundo molar superior esquerdo. A irradiância e energia radiante foram analisados utilizando ANOVA 3 fatores seguido por teste de Tukey (a=0.05). O espectro de luz (nm) foi analisado de forma descritiva. A interação entre o formato do AFP, posição do operador e preferência de mão foram significativamente influentes na irradiância e energia radiante (P<0.001). Em todos os casos, Valo teve irradiância significativamente maior que Radii-Cal. A mão dominante e a posição do operador afetaram a irradiância e energia radiante com o Valo. Posição do operador e acesso afetou a irradiância e exposição radiante entregue ao segundo molar superior esquerdo. A irradiância e exposição radiante teve melhores resultados quando AFP foi utilizado com a mão direita pelo operador posicionado na cadeira do lado direito e mão esquerda do operador posicionado do lado esquerdo da cadeira. Estes resultados podem levar a uma melhor polimerização da resina composta.

Light transmittance of CAD/CAM ceramics with different shades and thicknesses and microhardness of the underlying light-cured resin cement

OBJECTIVES: The aim of this in vitro study was to evaluate the effects of the thickness and shade of 3 types of computer-aided design/computer-aided manufacturing (CAD/CAM) materials. MATERIALS AND METHODS: A total of 120 specimens of 2 shades (A1 and A3) and 2 thicknesses (1 and 2 mm) were fabricated using VITA Mark II (VM; VITA Zahnfabrik), IPS e.max CAD (IE; IvoclarVivadent), and VITA Suprinity (VS; VITA Zahnfabrik) (n = 10 per subgroup). The amount of light transmission through the ceramic specimens was measured by a radiometer (Optilux, Kerr). Light-cured resin cement samples (Choice 2, Bisco) were fabricated in a Teflon mold and activated through the various ceramics with different shades and thicknesses using an LED unit (Bluephase, IvoclarVivadent). In the control group, the resin cement sample was directly light-cured without any ceramic. Vickers microhardness indentations were made on the resin surfaces (KoopaPazhoohesh) after 24 hours of dark storage in a 37°C incubator. Data were analyzed using analysis of variance followed by the Tukey post hoc test (α = 0.05). RESULTS: Ceramic thickness and shade had significant effects on light transmission and the microhardness of all specimens (p < 0.05). The mean values of light transmittance and microhardness of the resin cement in the VM group were significantly higher than those observed in the IE and VS groups. The lowest microhardness was observed in the VS group, due to the lowest level of light transmission (p < 0.05). CONCLUSION: Greater thickness and darker shades of the 3 types of CAD/CAM ceramics significantly decreased the microhardness of the underlying resin cement.

Impact of Material Shade and Distance from Light Curing Unit Tip on the Depth of Polymerization of Composites

Abstract This study aimed to evaluate the effect of the composite shade and distance from the light-curing unit (LCU) tip on the irradiance reaching the bottom of composite disks and on the depth of polymerization. Composites of three shades (opaque - OXDC, bleach - BXL, and A2) were inserted into molds with 3-mm of thickness positioned over a spectrometer and photo-activated with the LCU (Bluephase) tip placed at 0 or 1 cm from the composite surface. The mean irradiance reaching the bottom of composite was recorded during the entire photo-activation (30 s). Specimens (2 x 2 x 4 mm) were polymerized and used to map the degree of conversion achieved in different depths from irradiated surface. Specimens were sectioned into slices that were positioned over the platform of the infra-red microscope connected to the spectrometer to map the conversion. The conversion was measured in eight different depths every 500-µm. Increasing the distance of LCU tip reduced the irradiance only for A2. Interposing OXDC disks resulted in lowest values of irradiance and A2 the highest one. A tendency to decrease the conversion was observed towards the bottom of specimens for all experimental conditions, and the slope was more accentuated for OXDC. Differences among shades and distances from LCU tip were evident only beyond 1.5-2.0 mm of depth. In conclusion, both composite shade and distance from LCU tip might affect the light-transmission and depth of polymerization, while the effect of last was more pronounced.

Resumo Este estudo objetivou avaliar o efeito da cor do compósito e da distância da ponta do aparelho fotopolimerizador (AFP) na irradiância alcançando a base do disco de compósito e na profundidade de polimerização. Compósitos de três cores (opaca - OXDC, clareado - BXL, e A2) foram inseridos em moldes com 3 mm de espessura posicionados sobre um espectrômetro e fotoativados com a ponta do AFP (Bluephase) colocada a 0 ou 1 cm da superfície do compósito. A irradiância média alcançando a base do compósito foi registrada durante toda a fotoativação (30 s). Amostras (2 x 2 x 4 mm) de compósito polimerizado também foram confeccionadas e usada para mapear o grau de conversão obtido em diferentes profundidades da superfície irradiada. As amostras foram seccionadas em fatias que foram posicionadas sobre a plataforma de um microscópio infra-vermelho conectado ao espectrômetro para mapear a conversão. A conversão foi mensurada em oito diferentes profundidades com 500-µm entre elas. Aumentando a distância da ponta do AFP reduziu a irradiância apenas para A2. Interpondo discos de OXDC resultou em menores valores de irradiância e A2 nos maiores. Uma tendência de redução na conversão foi observada em direção a base das amostras para todas as condições experimentais, com uma redução mais acentuada para OXDC. Diferenças entre as cores e distâncias da ponta do AFP foram evidentes apenas a partir de 1,2-2,0 mm de profundidade. Como conclusão, tanto a cor do compósito como a distância da ponta do AFP podem afetar a transmissão de luz e a profundidade de polimerização, enquanto que o efeito do último foi mais pronunciado.

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.

Efficiency of polymerization of bulk-fill composite resins: a systematic review

Abstract This systematic review assessed the literature to evaluate the efficiency of polymerization of bulk-fill composite resins at 4 mm restoration depth. PubMed, Cochrane, Scopus and Web of Science databases were searched with no restrictions on year, publication status, or article's language. Selection criteria included studies that evaluated bulk-fill composite resin when inserted in a minimum thickness of 4 mm, followed by curing according to the manufacturers' instructions; presented sound statistical data; and comparison with a control group and/or a reference measurement of quality of polymerization. The evidence level was evaluated by qualitative scoring system and classified as high-, moderate- and low- evidence level. A total of 534 articles were retrieved in the initial search. After the review process, only 10 full-text articles met the inclusion criteria. Most articles included (80%) were classified as high evidence level. Among several techniques, microhardness was the most frequently method performed by the studies included in this systematic review. Irrespective to the "in vitro" method performed, bulk fill RBCs were partially likely to fulfill the important requirement regarding properly curing in 4 mm of cavity depth measured by depth of cure and / or degree of conversion. In general, low viscosities BFCs performed better regarding polymerization efficiency compared to the high viscosities BFCs.

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.