Shear Bond Strength Of Orthodontic Brackets Bonded With A Self-etching Adhesive

Objective The purposes of this study was to evaluate the effects of using a new self-etching adhesive on the shear bond strength (SBS) of orthodontic brackets and on the bracket/adhesive failure mode in the dry and saliva-contaminated conditions.Methods 120 extracted human promolars which had been extracted for orthodontic purposes were collected and were divided randomly into ten groups(12 each). Brackets were bonded to the teeth according to one of the following protocols. Group A0, B0:The enamel surface of each tooth was etched for 30 seconds with 37% phosphoric acid, followed rinsing with water for 60 seconds and drying with an air syringe, then jing-jin enamel adhesive was used for bonding brackets according to the manufacturer' s directions. Group. A1, B1: A self-etch acidic primer, Prompt L-Pop (3M/ESPE) was placed on the enamel and rubbed for 3 seconds, gently dried with an syringe air. Precoated brackets TransbondXT (3M Unitek) were then placed on the teeth and light cured for 40 seconds. Group A2, B2: The enamel surface was first contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The bonding procedure was then repeated as in group A1, B1. Group A3, B3: The self-etch primer was applied for 3 seconds, gently dried with an syringe air. The surface was then contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The precoated brackets were then bonded as in group A1, B1 Group A4, B4: The enamel surface was contaminated with human saliva for 10 seconds, blown off with an air syringe for five seconds. The self-etch primer was applied. The surface was then re-contaminated with human saliva for 10 seconds, blown off with an air-syringe for five seconds. The precoated brackets were then bonded as in group A1, B1. All the specimens were stored in 37C waterafter bonding . The shear bond strength and the adhesive remnant index(ARI) were determined in the first 30 minutes(groups B0-B4) and 24 hours (groups A0-A4) respectively after bonding.Results The results of the analysis of one-way ANOVA and Tamhane' s T2 indicated that the new acid-etch adhesive can maintain adequate shear bond strength as jing-jin enamel adhesive in dry (At=9. 86+2. 01 Mpa> B,=9. 87 + 2. 45 Mpa) or contamination occurs either before (A2=9. 76 + 2. 65Mpa, B2=9. 69 + 2. 50 Mpa) or after (A3=9. 55 + 2. 18 Mpa, B3=9. 50 + 2. 07Mpa) the application of the primer. On the orther hand, the combined contamination both before and after the application of the primer resulted in a significantly lower (A4=5.47 + 1. 68Mpa , B4=5.38 + 1. 19Mpa) (p<0. 01) shear bond strength than either of other groups . The adhesive remnant index scores indicated that significant less residual adhesive was remained on the teeth in the group using self-etching adhesive(p<0. 01).Conclusions The self-etching adhesive can maintain adequate bonding strength in bonding orthodontic brackets as jing-jin enamel adhesive in dry and lightly saliva-contamination conditions. On the other hand, the combined contamination both before and after the application of the primer significantly reduced the mean shear bond strength. Less residual adhesive was remained on the teeth in the groups using self-etching adhesive and it will save time and protect the enamel from frature and crazing when removing brackets.