An influence of finishing procedures and protective coating on the ultrastructure of conventional and hybrid glass ionomer cement restorations

Introduction. In addition to the advantages of glass ionomer cements that have led to their wide application, hybrid glass ionomer cements have been developed to overcome the shortcomings in mechanical resistance. The aim of the study was to perform an ultrastructural analysis of restorations made from conventional and hybrid glass ionomer cements after recommended finishing procedures and application of a protective coating. Materials and Methods. This study analyzed 30 samples of conventional glass ionomer cement Fuji IX? and 30 samples of hybrid glass ionomer cement EQUIA Forte HT Fil?. The samples were prepared in cylindrical molds and divided into the three groups. The first group of samples, after adaptation, was left untreated and served as a control group. The second group consisted of samples that were finished with a cylindrical diamond bur with water cooling. The samples in the third group were finished and protected with appropriate coatings (G-COAT PLUS? and EQUIA Forte Coat?). The samples were analyzed using scanning electron microscopy. Results. The finishing procedures of Fuji IX? samples significantly reduced crack width (t = 3.42, p < 0.005; Z = 3.25, p = 0.001). Similarly, the crack width in EQUIA Forte HT Fil? samples was also significantly smaller in treated samples (t = 4.78, p < 0.001; Z = 4.28, p < 0.001). Ultrastructural analysis of both materials showed the complete absence of cracks in finished samples protected by coatings. Conclusion. Finishing of conventional and hybrid glass ionomer cements results in a reduction in the number of cracks as well as a decrease in their widths, and the protective coatings completely cover remaining cracks.