Avaliação em microscopia óptica e eletrônica de varredura da influência do ácido cítrico como agente condicionante sobre o selamento marginal em cavidades classe II: um estudo “in vitro”

Abstract

The aim of this study was to evaluate the influence of the gels of citric acid and phosphoric acid on microleakage in class II cavities restored with composite nanoparticle. Thirty five human molars were used, in which were made cavities as vertical slots with gingival ending below the enamel-cementum junction. The teeth were randomly divided into seven groups according to the conditioning agent and application time to be used (n=10): Group I: 25% citric acid for 30 seconds; Group II: 35% citric acid for 30 seconds; Group III 10% citric acid for 15 seconds and Group IV: 10% citric acid for 30 seconds and Group V - 35% phosphoric acid for 15 seconds, Group VI: 35% citric acid for 15 seconds, Group VII: 25% citric for 15 seconds. The cavities were restored with Filtek Z350 composite nanoparticles; witch was introduced in the cavity by an incremental technique. The adhesive system was Scotchbond Multi Purpose (3M). The samples were subjected to thermocycling for 5000 cycles. Afterwards each group was immersed in a solution of ammoniacal silver nitrate for 24 hours. Then, the teeth were sectioned mesio-distal and microleakage was evaluated by the Optical Microscope (OM) using the scores. The Scanning Electron Microscope (SEM) was used for qualitative observation of the presence or absence of cracks in the restoration. For this analysis we selected the worst and the best result for each group. The results were submitted to a statistic analysis using the Kruskal Wallis Test and with the Mann-Whitney (p=0,05). The study concluded that the concentration and time of application of citric acid have statistically significant effect on microleakage. Citric acid proved to be a possible replacement of phosphoric acid etching on dentin.