The effect of different enamel surface preparations on microleakage under orthodontic brackets

Microleakage is caused by many factors, including polymerization shrinkage of the resin, thermal expansion differences between the enamel and the adhesive, and inadequate adherence. This study aims to assess the microleakage value under orthodontic brackets after three distinct enamel surface preparations and compare the results to the traditional procedure. Fifty-four intact upper premolars were randomly distributed into three groups. First group 18 teeth etched with 36% phosphoric acid Dentsply. Second group 18 teeth etched with %1.23 acidulated phosphate fluoride (APF) incorporated phosphoric acid 25%APF 75%phosphoric acid Dentsply. Third group 18 teeth etched with Trans Bond TM Plus Self-Etching prime 3M Unitek, Monrovia, USA. Then, according to the manufacturer's instructions, all groups bonded to stainless steel brackets RAZOR, IOS, USA, using light-cured composite 3M Unitek/ Monrovia, USA. Then, each subgroup was divided into 3 subgroups, 6 teeth each. The first subgroup thermocycled 500 cycles between 5 C and 55 UC in deionized water and tested after 24 hours of water storage. The second subgroup was also thermocycled and tested after 2 months of water storage. The third subgroup was subjected to cyclic acid attack for 2 months by an acidic solution pH=2.5. Microleakage was evaluated using a dye penetration technique. All samples are sectioned and evaluated under a stereomicroscope. For statistical analysis, the Kruskal-Wallis test was employed. P=0.05 was the level of significance. A significant difference was between etching groups following a thermocycler and a twenty-four-hour water storage, no significant difference after thermocycling and two months of water storage, and significant difference at the occlusal side and between overall means of compared etching groups. This study revealed that the highest microleakage values were in the SEP self-etch prime group, then EF 1.23% APF incorporated phosphoric acid group and the ER 36% phosphoric acid group. The gingival side had more microleakage than the occlusal side. Adding around 20-25 percent of 1.23 percent of phosphoric acid for enamel preparation before orthodontic bonding increases microleakage values, but SEP remains the highest. Keywords: Microleakage, Self-etch prime, Acidulated phosphate fluoride, Stainless steel brackets