Influence of Different Manipulation Methods on the Microhardness of Nanoparticulate Restorative Composites

Abstract

The aim of this study was to evaluate the influence of different manipulation techniques on the microhardness of two nanoparticulate restorative composites. Sixty-six specimens were prepared, which were distributed into 8 groups according to the restorative material (Filtek Z350 XT ® and Evolu-X ®) and manipulation technique: digital manipulation; digital manipulation and rubbing of gloves with 70% alcohol; glass plate manipulation; glass plate manipulation previously rubbed with 70% alcohol. Resin increments were inserted into a bipartite Teflon matrix with orifice (5mmx3mm) and photopolymerized with 750mW/ cm² laser apparatus for 40 seconds and stored in deionized water at 37°C for 24 hours. Specimens were then included in polyvinyl chloride rings for subsequent surface planing and microhardness testing (Vickers penetrator, 50g/15s). Data were submitted to descriptive and inferential statistical analysis (significance level of 5%). In groups where Filtek Z350 XT ® resin was used, hardness variation from 30 HV to 89.00 HV was observed, while for Evolu-X ® resin, the lowest averages were obtained in groups whose manipulation was digital with (59.27HV) and without (58.85 HV) use of 70% alcohol. Nanoparticulate composites, manipulated by different techniques, did not present a similar mechanical behavior when evaluated by the microhardness test. The highest hardness values were obtained for Filtek Z350 XT ® resin, manipulated in glove previously rubbed with 70% alcohol.