Impact of adhesive and photoactivation method on sealant integrity and polymer network formation

We evaluated the influence of photoactivation method and hydrophobic resin (HR) application on the marginal and internal adaptation, hardness (KHN), and crosslink density (CLD) of a resin-based fissure sealant. Model fissures were created in bovine enamel fragments (n = 10) and sealed using one of the following protocols: no adhesive system + photoactivation of the sealant using continuous light (CL), no adhesive system + photoactivation of the sealant using the soft-start method (SS), HR + CL, or HR + SS. Marginal and internal gaps and KHN were assessed after storage in water for 24 h. The CLD was indirectly assessed by repeating the KHN measurement after 24 h of immersion in 100% ethanol. There was no difference among the samples with regard to marginal or internal adaptation. The KHN and CLD were similar for samples cured using either photoactivation method. Use of a hydrophobic resin prior to placement of fissure sealants and curing the sealant using the soft-start method may not provide any positive influence on integrity or crosslink density.

Effect of light curing methods on microleakage and microhardness of different resin sealants.

PURPOSE: This study's purpose was to evaluate the effect of light curing methods on the microleakage and microhardness of sealants. METHODS: The Elipar Free Light 2 light emitting diode (LED) with 10- and 20-second curing times, and the Elipar 2500 halogen light with a 20-second curing time were compared. Four different sealants were used: (1) Delton Clear; (2) Delton Opaque; (3) UltraSeal XT Clear; and (4) UltraSeal XT Opaque. Specimens were fabricated in a silicone mold (2-mm thick) and cured. Knoop hardness was measured at the bottom and top surfaces. For the microleakage evaluation, 120 human molars were divided into 12 groups and sealed with the sealants and curing methods, as stated previously. The teeth were thermocycled and immersed in 2% methylene blue for 24 hours. Each tooth was sectioned and examined for dye penetration. RESULTS: There were no statistically significant differences in the microleakage of sealants polymerized by either the halogen or LED curing methods. The microhardness of sealants varied according to the type of material and curing method. CONCLUSIONS: A 10-second polymerization time with light emitting diodes was not sufficient to cure the 2-mm-thick opaque or high filler loaded sealants. Decreasing the curing time, however, had no effect on the microleakage of the sealants.

Effect of irradiation times on the polymerization depth of contemporary fissure sealants with different opacities

The aim of this study was to evaluate the depth of curing of 10 contemporary blue light-activated dental flowable materials at several opacities, influenced by different irradiation times using FT-IR spectroscopy. Fifty-five specimens (n = 5) with a 5-mm diameter and 1-mm thickness of translucent (Opallis Flow T), yellowed (Master Flow A2; Opallis Flow A2; Natural Flow A2; Fluroshield Yellowed), and opaque materials (Master Flow OA2; Natural Flow O; Opallis Flow OA3.5; Opallis Flow OP; Fluroshield White) were obtained at six curing times (10s, 20s, 30s, 40s, 50s, and 60s) using a high-intensity LED (Coltolux, Coltène/Whaledent). The degree of conversion (DC) ( percent) was obtained using the Nexus 470 FTIR Spectrometer (Nicolet Instruments, USA). The FTIR-ATR spectra for uncured and cured samples were analyzed using a ZnSe crystal. The top and bottom surfaces of the cured specimens were analyzed to obtain the depth of curing. Two-way ANOVA was used to analyze the data. The highest curing depth was obtained by Natural Flow OA2, while the lowest was shown by Master Flow OA2. The shortest curing time generated similar depths of cure in comparison with the most extensive for Opallis Flow A2 and Fluroshield Yellowed. Therefore, depth of curing, influenced by the irradiation time, was dependent on the materials. Using the Natural Flow OA2 opaque sealant and the 10-s curing time for Opallis Flow A2 and Fluroshield Yellowed may represent alternative approaches to sealing tooth fissures.

Effect of light curing units and storage time on the degree of conversion of fissure sealants / Efeito das unidades fotopolimerizadoras e do tempo de armazenamento no grau de conversão dos selantes de fissuras

OBJECTIVE: To investigate the effect of light curing units and storage time on the degree of conversion of fissure sealants. MATERIAL AND METHOD: Three different fissure sealants were used: a resin-based pit and fissure sealant (Clinpro SealantTM), a polyacid modified resin composite (Dyract SealTM), and a resin modified glass ionomer cement (VitremerTM). Each fissure sealant was polymerized with a halogen, high intensity quartz tungsten halogen, LED. Half of the specimens were tested to assess the degree of conversion immediately after polymerization and the others after one month’s storage in artificial saliva. The degree of conversion was measured by FTIR. The data were analyzed using two way ANOVA. RESULTS: Statistical analysis of Dyract SealTM showed significant differences between the DC values of samples tested immediately and again after one month’s storage (p < 0.05). The DC values of ClinproTM increased after the storage period (p < 0.05). The DC of VitremerTM showed no change after storage (p > 0.05). Results of the curing units testing showed no significant differences among the DC of samples polymerized with LED, HQTH, OTH tested immediately and again after one month for Dyract SealTM, VitremerTM and Clinpro SealantTM (p > 0.05). CONCLUSION: Light curing units had no effect on the degree of conversion of the fissure sealants. But storage after initial light activation and polymerization for one month in artificial saliva can affects on DC of fissure sealants.

OBJETIVO: Investigar o efeito de unidades de polimerização por luz no grau de conversão dos selantes de fissuras. MATERIAL E MÉTODO: Três diferentes selantes foram utilizados: um selante resinoso de fissuras (Clinpro SealantTM, uma resina composta poliácida modificada (DyractSealTM) cimento de ionômero de vidro modificado (VitremerTM). Cada selante de fissura foi polimerizado por LED halógeno de quartzo/tungstênio. Metade dos espécimes foi testada para assegurar o grau de conversão imediatamente após polimerização e outros após um mês de armazenamento em saliva artificial. O grau de conversão foi medido por FTIR. Os resultados foram analisados por meio do ANOVA. RESULTADOS: A análise estatística do Dyract SealTMdemonstrou diferenças estatisticamente significantes entre os valores DC dos espécimes testados imediatamente e novamente após um mês de armazenamento (p < 0,05). Os valores do ClimproTM aumentaram após o período de armazenamento (p < 0.05). O DC do VitremerTM não demonstraram alterações após o armazenamento (p > 0.05). Os resultados das unidades de fotopolimerização não mostraram diferenças significantes ente DC de amostras polimerizadas com LED, HQTH, O TH testados imediatamente e novamente após um mês para o Diract SealTM, VitremerTM e Climpro SealantTM. CONCLUSÃO: Unidades de fotopolimerização não tiveram efeito no grau de conversão dos selantes de fissuras. Porém, armazenamento após ativação inicial e polimerização por um mês em saliva artificial pode afetar o DC dos selantes de fissuras.

Effect of gamma irradiation on fluoride release and antibacterial activity of resin dental materials

This study evaluated the effect of gamma irradiation on fluoride release and antibacterial activity of FluroShield (FS) and Clearfil Protect Bond (CPB). Four groups were formed: G1-FS + gamma; G2-FS without gamma; G3-CPB + gamma; G4-CPB without gamma. For fluoride release analysis, 12 disks of each material were prepared and covered with nail polish, except for one side (50.4 mm² area). G1 and G3 were sterilized with a 14.5 KGy dose at 27ºC for 24 h, while G2 and G4 (controls) were not sterilized and were maintained under the same time and temperature conditions. Fluoride release measurements were made in duplicate (n=6) by an ion specific electrode. The antibacterial activity of the CPB and FS against Streptococcus mutans after gamma sterilization was evaluated by the agar-disc diffusion method. The diameter of the zones of microbial growth inhibition was recorded after 48 h. Data were analyzed statistically by ANOVA and Tukey's test (α=5 percent). Gamma sterilization decreased the fluoride release of FS by approximately 50 percent, while CPB was not affected. There was no statistically significant difference (p>0.05) in the antibacterial effect of CPB between gamma and non-gamma sterilization groups. FS presented no antibacterial activity. Gamma irradiation decreased the fluoride release of FS, but did not affect the antibacterial activity of the studied materials.

Este estudo avaliou o efeito da esterilização com raios-gama na liberação de flúor e atividade antibacteriana de materiais resinosos, Fluroshield (FS) e Clearfil Protect Bond (CPB). Quatro grupos foram formados: G1-FS e gama; G2-FS sem gama; G3-CPB e gama; G4-CPB sem gama. Doze discos de cada material foram preparados para análise de liberação de flúor, os quais foram cobertos com esmalte de unha, exceto em um lado com 50,4 mm² de área. G1 e G3 foram esterilizados com dose de 14,5 KGy por 24 h/27ºC, enquanto G2 e G4 (controles) não foram esterilizados e foram mantidos sob as mesmas condições de tempo e temperatura. As leituras de liberação de flúor foram feitas em duplicata (n=6) por um eletrodo específico. A atividade antibacteriana foi avaliada pelo teste de difusão em agar. Os halos de inibição foram medidos após 48 h. Os dados foram analisados pelos testes ANOVA e Tukey (α=5 por cento). A esterilização gama diminuiu a liberação de flúor de FS em cerca de 50 por cento, enquanto CPB não foi afetado. Não houve diferença estatisticamente significante entre os grupos esterilizados e controle no efeito antibacteriano do CPB. FS não apresentou atividade antibacteriana. A esterilização gama diminuiu a liberação de flúor de FS, mas não afetou a atividade antibacteriana dos materiais estudados.