Acid Corrosion Area Of Influence Of Orthodontic Braces Bonding Strength

Objective:To compare the shear bond strength of orthodontic brackets between different etching area, and to provide experimental evidence for clinical orthodontic brackets bonding.Methods:120 extracted human premolars were randomly divided into 8 groups (n=15): A1, A2, B1, B2, C1, C2, D1, D2. Control the etching area with the tailor-made membrane: group A1 and A2, etching area 25mm2(5mm×5mm); groupB1 and B2, etching area 9mm2(3mm×3mm); group C1 and C2, etching area 4mm2(2mm×2mm); group D1 and D2, etching area 1mm2(1mm×1mm). The first premolar standard edgewise brackets (base area 12.18mm2) were bonded with Jingjin enamel adhesive system. For group A1, B1, C1 and D1, after 0.5h solidification in drying condition, shear bond strength was measured, and the adhensive remnant index was recorded. For group A2, B2, C2 and D2, after 0.5h solidification in drying condition and thermocycled(1000 times at 5℃and 55℃), shear bond strength was measured, and the adhensive remnant index was recorded.Results:①In group A1, B1, C1 and D1, which were not thermocycled, the shear bond strength showed significant differences (P＜0.05). In group A1 and B1, group C1 and D1, the shear bond strength showed significant differences (P>0.05), and in the other mated groups the shear bond strength showed significant differences (P＜0.05). In the four groups the adhensive remnant index showed significant differences (P<0.05). In group A1 and B1 the adhensive remnant index showed no significant differences (P>0.05), and in the other mated groups the shear bond strength showed significant differences (P<0.05).②In group A2, B2, C2 and D2, which were thermocycled, the shear bond strength showed significant differences (P＜0.05). In group C2 and D2, group C1 and D1, the shear bond strength showed no significant differences (P>0.05), and in the other mated groups the shear bond strength showed significant differences (P＜0.05). In the four groups the adhensive remnant index showed significant differences (P＜0.05). In group A2 and B2, group A2 and C2, group A2 and D2, the adhensive remnant index showed significant differences (P＜0.05), and in group B2 and C2, group B2 and D2, group C2 and D2, the adhensive remnant index showed no significant differences (P>0.05).③For the groups with the same arching area, in group A1 and A2 the shear bond strength showed no significant differences (P>0.05), and in group B1 and B2, group C1 and C2, group D1 and D2, the shear bond strength showed significant differences (P＜0.05). In group A1 and 12, group D1 and D2, the adhensive remnant index showed no significant differences (P>0.05), and in group B1 and B2, group C1 and C2, the adhensive remnant index showed significant differences (P＜0.05).Conclusion:①Without thermocycled, the brackets shear bond strength are the same in group with a little bit small etching area and group with bigger etching area then the bracket baseboards.When the arching area decrease to 2mm×2mm, the bond strength can satisfy the clinic need of orthodontics.②fter thermocycled, the brackets shear bond strength will decrease along with the decreasing of arching area. When the arching area decrease to 3mm×3mm, the bond strength can satisfy the clinic need of orthodontics.③he thermocycle could significantly reduce the brackets shear bond strength. There was more influence for the groups with smaller area then the bracket baseboards.④hen the etching area a little bit small then the bracket base area, the bond strength can satisfy the clinic need of orthodontics.