Shear Bond Strength and Bonding Properties of Orthodontic and nano Adhesives: A Comparative In-Vitro Study

Nano restorative composites have been successfully used in restorative dentistry and have high strength and wear resistance. Conventional orthodontic adhesives also possess optimal strength to withstand occlusal forces. This study was done to compare the shear bond strength (SBS) of orthodontic bracket after bonding with nanorestorative composite and orthodontic adhesives.

This in-vitro experimental study used sixty extracted teeth (divided into two groups). In Group A (n = 30), the brackets were bonded with Filtek Z350 (3M/Unitek, Monrovia, California, USA), a nano ceramic restorative composite, and in Group B (n = 30), the brackets were bonded with Transbond XT (3M/Unitek, Monrovia, California, USA), a conventional orthodontic adhesive. The SBS of the orthodontic brackets was measured using a universal testing machine. The modified 0-5-scale adhesive remnant index (ARI) was used to assess the amount of adhesive on enamel and bracket surfaces. The surface topography was observed to evaluate enamel damage.

The mean (standard deviation [SD]) SBS of 11.07 (1.96) Mega Pascal (MPa) was observed with Filtek Z350, whereas the group bonded with Transbond XT showed the mean (SD) SBS of 12.18 (1.69) MPa. The results showed that Transbond light curing adhesive produced higher SBS than Filtek, but the difference was statistically insignificant (P = 0.088). The comparison of ARI score between the two groups also showed statistically insignificant difference (χ² = 4.764, df = 5, P = 0.445), and most of the teeth in both groups exhibited score 3 (63%), showing the least damaging mode of bond failure to the enamel bracket interface.

There was no significant difference in the mean SBS of Filtek Z and Transbond XT adhesives. Both materials showed optimum bond strength to withstand occlusal forces.