Evaluation of the effect of three bonding systems (Acetone based, Alcohol based, Water based) on shear bond strength of composite to bleached enamel

Many patients refer to dentists for bleaching discolored tooth. Regarding the different uses of composite and bleaching for esthetic purposes, this study investigated the effect of three bonding systems (Acetone based, alcohol based, water based) on shear bond strength of composite to bleached enamel. Method & Materials: 30 human intact premolar teeth extracted for orthodontic reasons were used for this experimental study which were mounted with self-cured Acryle 2mm below CEJ and divided into 6 groups each group containing 5 specimens randomly. Silicone discs were used for smoothing buccal and lingual surfaces. In the 1st group, after bleaching with 35% Hydrogen Peroxide, composite cylinders with 2mm height and diameter were bonded to buccal and lingual surfaces with Scotch bond-Mp. In the 2nd group, all specimens stored in Physiologic Serum for 10 days after bleaching, and then bonded with Scotch bond-Mp. In the 3rd group, all specimens bonded with Excite bond immediately after bleaching and in 4th group, all specimens stored in Physiologic Serum for 10 days after bleachin and then bonded with Excite. In 5th group, all teeth bonded with Stae immediatley after bleaching. And all specimens stored in Physiologic Serum for 10 days after bleaching and then banded with Stae in 6th group. SBS of the groups was measured with an Instron machine with speed of 0.5 mm/min after 24 hours. Shear bond strength of the first group was 16.71± 1.54 Mpa, for the third and fifth groups it was 36.14± 2.12 Mpa and 19.26± 1.75 Mpa respectively. It was 22.44 ±1.90 Mpa, 35.35± 2.56 Mpa and 30.57± 5.13 Mpa in the second, fourth and sixth groups respectively. The overal significant differences existed among the groups (ANOVA test, P<0.0001). The t-test showed a statistical difference between the first and second groups and also the fifth and sixth groups (P<0.0001) but there was no statistical difference between the third and fourth groups (P>0.463). The results of this in vitro study indicated that the shear strength of composite resin to bleached enamel with alcohol – based dental bonding agents was more than Acetone-based and water-based bondings. Also it was possible to bond with alcohol-based bondings immediately after bleaching but there must be a post bleaching stage of 10 days when water-based or Aceton-based bondings were used.