The relationship between bond strength and orthodontic bracket base surface area with conventional and microetched...

The aim of this study was to test the effects on the shear bond strength by sandblasting bracket base surfaces, reducing base surface area, and etching enamel with various acid types. Four different base sizes, used as either standard (untreated), sandblasted or microetched were bonded with Phase II resin (Reliance Orthodontic Products, Inc.) in four groups of 12 bovine enamel specimens after enamel etching with phosphoric acid gel (37%), 37% phosphoric acid aqueous solution, 10% maleic acid gel, or 10% maleic acid aqueous solution. Storage of samples was for 7 days in distilled water at room temperature before shear bond testing with an Instron universal testing machine with a crosshead speed of 0.5 mm/min. Statistical analyses included the analysis of variance, the Student t test, and the Chi-square test at p < 0.05. An increase in shear bond strength was associated with sandblasting and microetching of foil-mesh bases for all base sizes (p < 0.05). No statistically significant difference in shear bond strength existed between the three larger base sizes, which indicated that shear bond strength is independent of surface area between 6.82 and 12.35 mm2. A reduction in bond strength was associated with the reduction of base surface area from 6.82 to 2.38 mm2 (p < 0.05). There appears to be no need to increase base surface area beyond 6.82 mm2. Aqueous maleic acid (10%) etching of the enamel was associated with the highest shear bond strength, with no statistically significant difference between the other three acids used.