Correlation between dental enamel chemical composition and bracket debonding, comparing adhesive systems through a scanning electron microscope.

Literature reports indicate that during bracket removal there can be enamel damage. We compare the shear bond strength (SBS) and tooth enamel loss of four adhesive systems and identify the Ca/P ratio. Then a total of 20 premolars were divided into four groups of five each. After prophylaxis, photographs were taken at 35x with a scanning electron microscope (SEM) and analyzed with X-ray spectroscopy (EDS) at 250x. Brackets were bonded with Transbond MIP(G1), Transbond PLUS SEP(G2), Enlight(G3) and Stylus(R)(G4) adhesives, 24 h after were debonded with a Instron universal testing machine at 1 mm/min. All the brackets were photographed with the SEM. The amount of lost enamel was measured with AutoCad. All the results were measured with a significance level p < .05. The SBS general average at debonding was 7.94 +/- 2.26 MPa, meanwhile the SBS for G1, G2, G3 and G4 was 9.38 +/- 1.46, 6.28 +/- 0.69, 9.08 +/- 2.45 and 7.04 +/- 2.64 MPa respectively. 90% of the samples had no enamel loss, 10% had enamel loss. Only two samples in G1 presented an enamel loss area of 0.34mm(2) and 0.80mm(2) respectively. From EDS analysis, the Ca/P ratio was 1.6 +/- 0.05, 1.61 +/- 0.03, 1.64 +/- 0.83 and 1.59 +/- 0.07 for G1, G2, G3 and G4 respectively; no statistically significant differences were found. We conclude that no association was found between the Ca/P ratio and enamel damage when brackets are removed. HIGHLIGHTS: Where enamel is lost, we observe fractures, steps, horizontal and vertical enamel loss. There is a loss of tooth enamel from 0.34 to 0.80 mm(2) with Transbond PLUS SEP. Structural loss of enamel is almost inevitable during the separation of the bracket.