Análise da formação de fendas internas na interface adesiva e dureza de resinas bulk fill em restaurações de cavidades Classe I utilizando diferentes estratégias de fotoativação

Abstract

The aim of the study was to analyze gap formation at the adhesive interface and Vickers hardness (VHN) of low- and high- viscosity bulk fill resin restorations using different light-curing strategies. The study, previously approved by the CEP (4,881,321/2021), used 80 third molars (n=5) where standardized Class I cavities were made and restored according to the following groups: Tetric N-Ceram Bulk Fill (TNC - Ivoclar Vivadent) and SureFill SDR Plus (SDR - Dentsply Sirona) both inserted in a single increment. The resins were light cured with a polywave LED curing light (Bluephase 20i - Ivoclar Vivadent) according to each experimental group: 10” occlusal (Technique 1); 40” occlusal (Technique 2); 20" occlusal, 10" buccal, 10" lingual (Technique 3); 10" buccal, 10" lingual, 20" occlusal (Technique 4). The restored teeth were evaluated in two conditions, 72 h after the restorative procedure and after thermocycling The buccal surface was ground along the long axis of the tooth until exposing the inner surface of the restoration. Caries Evidencing Solution (Maquira Dental Group) was applied over the exposed adhesive interface. The length of the interface gaps was measured and the percentage calculated based on the total length of the interface. To analyze the VHN, three indentations were made in the area of the top of the inner surface of the restoration, close to the occlusal surface, as well as at the base, close to the interface created in the pulp wall: in the mesial region, center The gap formation results were analyzed by means of 2-way ANOVA followed by the Bonferroni test (α=0.05).The VHN results were evaluated by means of 2-way ANOVA followed by the d test and Tukey (α=0.05). For TNC and SDR resins, no significant differences were observed when comparing the different light curing techniques. After thermocycling, Photoactivation Techniques 1 and 2 promoted significantly higher values of gap formation when compared to the 72 h interval for both TNC and SDR resins (p=0.03 and p<0.01, respectively). There was no significant difference between the regions evaluated in the same group in the case of Technique 2, 3 and 4 and in the comparison of the regions evaluated between the different techniques in both intervals. In the SDR resin, the hardness values observed when using Technique 3 were higher than those obtained when using Technique 1 (p=0.034). It can be concluded that the techniques that comprise higher values of radiant exposure did not influence the gap formation, regardless of the type of Bulkfill composite resin. However, the chosen technique can influence the hardness values depending on to the composite. Likewise, the impact of thermocycling on gap formation is related to the photoactivation technique.