In vitro evaluation of debonding pattern in bonding interface of orthodontic adhesive materials to impacted teeth enamel: 48-hour and 10-day shear bond strengths

Roberto Yoshio KAWAKAMI, Ary dos Santos PINTO, João Roberto GONÇALVES, Maurício Tatsuei SAKIMA, Luiz Gonzaga GANDINI JR

The aim of this study was to evaluate the shear bond strength and the debonding pattern of the bonding interface of orthodontic bonding materials to dental enamel of impacted teeth. The materials used were a conventional composite (Concise Orthodontic – 3M) and a resin-reinforced glass ionomer cement (Fuji ORTHO LC – GC). Maxillary and mandibular unerupted third molars were used, extracted due to orthodontic indication or lack of space in dental arch. The teeth were randomly divided into three groups (n=30): Group I – Concise Orthodontic; Group II – Fuji ORTHO LC with etching; and Group III – Fuji ORTHO LC without etching. After manufacturing of samples, shear bond strength tests were made after 48 hours and 10 days in all groups. Shear bond strength was measured in MegaPascal (MPa) and also the Adhesive Remnant Index (ARI) was evaluated, as well as the patterns of debonding according to Marra in the interface adhesive/dental enamel, checking the presence of enamel fractures. For the evaluation of shear bond strength, Analysis of Variance and Tukey’s test were used; for the analysis of IAR, MARRA variable and patterns of enamel fracture, Chi-square and Fisher’s tests were used. In Group III, ARI=0 and MARRA=1 indexes were regularly found after 48 hours and 10 days, showing that no remaining adhesive was found bonded to the dental enamel. In a different way, in Group II, where the same material was used (Fuji ORTHO LC) with enamel etching, both indexes showed a higher frequency of remaining adhesive on the enamel and also some teeth presented enamel fracture, which was not seen in Group III. Group I (Concise Orthodontic) showed a great number of partial or total enamel fractures in both periods of analysis, with a higher frequency for Marra indexes of 6 and 2, after 48 hours and 10 days, respectively. As to the evaluation of shear bond strength, all the groups presented statistically signiicant differences, with higher mean values for Group I (20.36+1.04 MPa) e shorter for Group III (7.01+0.42 MPa). A statistically signiicant raise from 48 hours to 10 days was seen in Groups II and III.

Keywords: Glass ionomer cements. Composite resins. Compressive strength. Shear bond strength.

Wednesday, May 01, 2024 00:11