Abstract
Problem statement: The purpose of the present study was to compare Shear Bond Strength (SBS) and bond failure site of conventional and Self-Ligating (SL) orthodontic brackets, bonded on dry and saliva contaminated enamel. Approach: One conventional and three different types of self ligating stainless steel brackets were bonded onto 160 bovine permanent mandibular incisors, divided randomly into 8 groups, using Transbond XT adhesive system. For each type of bracket, 20 samples were bonded on dry enamel and 20 after saliva contamination. After 24 h all specimens were tested for SBS using an instron universal testing machine and Adhesive Remnant Index (ARI) were evaluated. Results: Saliva contamination significantly lowered SBS of conventional brackets. For self-ligating brackets no significant strength reduction was recorded. Conclusion: All the groups showed clinically adequate mean shear bond strengths. ARI scores in contaminated groups resulted lower than in dry groups.
Highlights
Despite the continuous progresses in direct bonding technique, the brackets unexpected detachment is one of the biggest problems orthodontists have to face
Many studies have been conducted to improve brackets adhesion to enamel surfaces, working on the different variables that concur in bonding success: bracket base design
Concerning with saliva contamination, Shear Bond Strength (SBS) we recorded for each saliva group, were lower than SBS of the corresponding dry group
Summary
Despite the continuous progresses in direct bonding technique, the brackets unexpected detachment is one of the biggest problems orthodontists have to face. A critical factor that affects bond strength of adhesion is wetness due to water, saliva or blood contamination of the etched enamel surface. When etched enamel becomes wet, most of the porosities become plugged and resin penetration is impaired, resulting in resin tags of insufficient number and length; when contamination is produced after the primer application, it is the hydrophilic capacity of the primer that is important, and the bracket bonding resin (Vicente et al, 2009). Water contamination is more avoided than saliva or blood contamination because these two can deposit an organic adhesive coating within the first few sec of exposure that is resistant to washing (Sfondrini et al, 2004). Saliva is reported to be the most frequent encountered contamination in the clinic and even momentary saliva contact adversely affects the bond (Sfondrini et al, 2004)
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