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An Investigation of the Effects of Chemical Reagents on the Shear Bonding Forces of Orthodontic Metal Brackets

Chien-Chih Yu,Jian-Hong Yu*,Hsiu-Ju Lin

The bonding of brackets is an essential part during the course of orthodontic treatment. A good bonding between the brackets and enamel surface is highly anticipated in the orthodontic treatment period with dynamic state. Debracketing at the end of orthodontic treatment is the critical moment for making a perfect endpoint. 4-META with superior bonding forces is an adhesive material commonly used in clinical practice. However, a good bonding force can cause increased difficulties in clinical practice and even result in pain or discomfort during the debracketing procedure. Therefore, this study aimed to find ways to reduce bonding forces during debracketing for the ultimate purposes of reducing the difficulties in clinical practice, as well as to eliminate pain and discomfort for patients. Super-Bond C and B (Sun Medical Company, Kyoto, Japan) as an adhesive resin in combination with metal brackets (Tomy Company, Tokyo, Japan) was used for bond strength tests in the present study. Fifty human premolars extracted due to orthodontic treatment were collected, randomly divided into five groups and immersed in different reagents as follows: no treatment (control group), ethanol (experimental group 1), eucalyptus oil (experimental group 2), peppermint oil (experimental group 3) and hot water (experimental group 4). After 10 min of immersion for each group, the specimens were subjected to debonding tests using a material testing machine (Model JSV H1000, vertical, an automated test station utilizing the features of Handy Force Gauge (HF-100)). The distributions of residual resin were examined by an optical microscopy after debonding and then analyzed according to the recorded Adhesive Remnant Index (ARI) score. The results showed that the bonding forces of 4-META / MMA-TBB resin was reduced to the lowest level after 10 minutes of immersion with eucalyptus oil (experimental group 2). In comparison with the control group, there was a statistically significant difference (experimental group, 2: 8.88 ± 2.61 Mpa vs. control group, 13.81 ± 3.04 MPa). Peppermint oil (experimental group 2) also caused reduction in the bonding forces but less effective than eucalyptus oil. Ten minutes of immersion with ethanol or hot water showed no effect on the bonding forces for Super-Bond C and B resin. There was no difference in the distributions of residual resin among all groups. The use of chemical reagents could lead to a reduction in shear bonding forces of orthodontic resin. However, more in-depth studies are necessitated to compare with the other reagents and improve formulations so that can be used in the mouth.