Comparison of Shear Bond Strength of Bonded and Rebonded Orthodontic Brackets Following Removal of Adhesive Remnants by Four Different Methods

The aim of the in vitro study was to examine the enamel surface after the application of four different methods for adhesive removal following the bracket debonding procedure, as well as to compare their effects on enamel surface.

Premolars (n=60) were randomly assigned to four groups. After initial debonding and recording the shear bond strength (SBS), adhesive remnant index (ARI) scores were assessed. The removal method for each of the four groups was the use of 1) a round bur, 2) rubber wheel bur, 3)12 fluted tungsten carbide bur, and 4) scaler. After that, teeth in all four groups were kept in artificial saliva for one month. After rebonding with a new bracket, again the SBS and ARI scores were measured. Two representative samples from each group were examined under a scanning electron microscope. ……. P-value <0.05 was considered as significant. ANOVA test was used to assess the SBS association within the group. Paired T test was used to assess the SBS between the group. fisher’s exact test was performed to compare ARI index before and after.

There was significant decrease in secondary SBS value in group 1 but significant increase in secondary SBS value in group 3, and a slight decrease in SBS value in group 4. In SEM images, there were composite remnants in all the four groups with fewer remnants in group 2. Enamel surface damage was observed in the SEM image of group 3. ARI scores showed no significant difference.

Adhesive remnant removal efficiency of the round bur and scaler are less. Rubber wheel bur is a good choice of instrument for removal of adhesive remnants from tooth surface as it does not affect the bond strength. Tungsten carbide bur shows good results, as secondary bonding SBS value increased. Significant difference between ARI scores did not exist, indicating a higher number of mixed type failure in all groups.