No-primer adhesive vs. self-adhesive resin: bonding strength following LED curing

The goal of this study was to compare the shear bond strength (SBS) and failure modes of three different adhesive resins following the use of two different dental curing light units.

A total of 160 human premolars were randomly divided into four groups (N = 40 for each): group 1, Transbond™ XT (3M Unitek, Monrovia, CA, USA) adhesive paste; group 2, Heliosit Orthodontic paste with no primer; group 3, Maxcem Elite (Kerr, Orange, CA, USA) self-adhesive resin with prior etching; group 4, Maxcem Elite self-adhesive resin with no etching. Each group was further divided into 2 subgroups: half (named "a") were cured with VALO LED (Ultradent Products, South Jordan, UT, USA), and the other half (named "b") with the Elipar LED unit (3M Unitek LED, Monrovia, CA, USA). The brackets were submitted to SBS testing 24 h after bonding. Adhesive Remnant Index (ARI) scores and bonding time were also measured. Two-way analysis of variance (ANOVA) and Kruskal-Wallis tests were used for statistical analysis.

No significant differences in SBS were observed when comparing the two different LED devices within the same bonding material. The mean SBS of group 1 was significantly higher compared to groups 2, 3, and 4 (p < 0.001). Mean SBS values of groups 2 and 3 were significantly higher than that of group 4 (p < 0.001). ARI scores were significantly different in groups 4a and 4b compared to the other groups (p < 0.05). Group 4a showed significantly lower bonding time/tooth compared to the other groups except to groups 3a and 4b (p < 0.001).

Decreasing curing time using high-power LED device did not significantly affect SBS. However, the composite type did affect SBS.