THE RELATIONSHIP BETWEEN BOND STRENGTH AND ORTHODONTIC BRACKET BASE SURFACE-AREA WITH CONVENTIONAL AND MICROETCHED FOIL-MESH BASES

The aim of this study was to test the effects on the shear bond streng th 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 fo ur groups of 12 bovine enamel specimens after enamel etching with phos phoric acid gel (37%), 37% phosphoric acid aqueous solution, 10% malei c acid gel, or 10% maleic acid aqueous solution. Storage of samples wa s for 7 days in distilled water at room temperature before shear bond testing with an Instron universal testing machine with a crosshead spe ed of 0.5 mm/min. Statistical analyses included the analysis of varian ce, the Student t lest, and the Chi-square test at p < 0.05. An increa se in shear bond strength was associated with sandblasting and microet ching of foil-mesh bases far all base sizes to < 0.05). No statistical ly significant difference in shear bond strength existed between the t hree larger base sizes, which indicated that shear bond strength is in dependent of surface area between 6.82 and 12.35 mm(2), a reduction in bond strength was associated with the reduction of base surface area from 6.82 to 2.38 mm(2) (p <. 0.05). There appears to be no need to in crease base surface area beyond 6.82 mm(2). Aqueous maleic acid (10%) etching of the enamel was associated with the highest shear bond stren gth, with no statistically significant difference between the other th ree acids used.