SEM evaluation of marginal sealing on composite restorations using different photoactivation and composite insertion methods.

Aim: This in vitro study evaluates the influence of marginal sealing methods in composite restorations with different adhesive systems submitted to mechanical load. Materials and Methods: Eighty bovine incisor crowns were embedded in Polyvinyl chloride (PVC) molds with the buccal surface exposed, where cavities (4mm x 4mm x 3mm) were made. Samples had the adhesive systems, Single Bond or Clearfil SE Bond, applied according to the manufacturer's recommendations. The cavities were filled with a Z-250 composite according to the restoration technique (bulk filling or three increments) and photoactivation (conventional, soft start, pulsatile light or light-emitting diode [LED]). The samples were duplicated with epoxy resin for scanning electron microscopy observations. Samples were also submitted to mechanical load (200,000 cycles; 2 Hz) and new replicas were made. Results: The results, in percentages, were submitted to ANOVA followed by Tukey's test (P < 0.05). There was statistical difference between the cycle group (23.84%) and the non cycle group (18.63%). Comparing the restoration technique, there was no statistical difference between bulk filling (19.62%) and three increments (22.84%). There was no statistical difference among the groups: Pulsatile light (24.38%), soft start (22.75%), LED (21.47%) or conventional (16.34%). Furthermore, there were no statistical differences between the adhesive systems: Clearfil SE Bond (21.32%) and Single Bond (20.83%). Conclusions: The photoactivation methods, the restorative techniques and the adhesive systems did not influence gap formation.

Influência do protocolo de fotoativação no selamento de restaurações com compósitos / Influence of light-curing mode on the sealing of resin composite restorations

O propósito deste estudo foi avaliar a influência do protocolo de fotoativação no selamento de restaurações classe V com compósitos. Sessenta cavidades com margem oclusal em esmalte e margem apical em dentina, preparadas nas superfícies vestibular e lingual de pré molares humanos, foram hibridizadas com o sistema adesivo Single Bond e restauradas com três compósitos (A110, P60 e Point 4). Para cada compósito, foram produzidos dois grupos de acordo com os protocolos de fotoativação (n = 10): Convencional-500 mW/cm2/40 segundos e Softstart-250 mW/cm2/40 segundos + 500 mW/cm2/20 segundos. Após acabamento/polimento das restaurações e armazenagem durante 7 dias em água destilada a 37°C, os dentes foram submetidos à termociclagem. Os espécimes foram impermeabilizados com esmalte de unha e imersos em solução neutra de azul de metileno a 2 % por 24 horas. Os dentes foram seccionados e o grau de penetração do corante foi avaliado em uma escala ordinal de 0-3. Os dados foram submetidos aos testes de Kruskal-Wallis e Mann-Whitney (α = 0,05). Não houve diferença estatística entre os grupos ativados com os dois protocolos de fotoativação. A microinfiltração foi maior nas margens em dentina do que nas margens em esmalte (p < 0,01). Esses achados sugerem que o protocolo de fotoativação soft-start não apresentou influência no selamento de cavidades restauradas com compósitos fotopolimerizáveis

This study investigated the effect of light-curing modes on cervical sealing of resin composite restorations. Sixty cavities with the occlusal margins in enamel and the gingival margins in dentin, prepared on the labial and lingual surfaces of human premolars were treated with Single Bond adhesive system and restored using a bulk technique with three resin composites (A110, P60 and Point 4). For each composite, two groups of 10 cavities were created according to the two light-curing modes: Standard (S)-500 mW/cm2 / 40 seconds and Soft-start (SS) - 250 mW/cm2 / 40 seconds + 500 mW/cm2 / 20 seconds. The specimens were submitted to thermocycling prior to immersion in 2% neutral solution of methylene blue for 24 hours. The teeth were sectioned and the degree of dye penetration was scored on a 0-3 ordinal scale. The data were analyzed by Kruskal-Wallis and Mann-Whitney tests (α = 0.05). No significant difference in the microleakage scores was observed among the groups polymerized with the two light-curing modes. The microleakage was greater in dentin margins than in enamel margins (p < 0.01). These results suggest that soft-start light-curing mode did not have any influence on resin composite restoration sealing