Materials and methods: Access cavities were prepared in 75 non–carious human pre-molars. Except for control group (Cont), bleaching agent (TiON office, GC) was applied to the access cavity according to the manufacturer's instructions. One of the bonding systems (Clearfil SE Bond; SE, Kuraray Medical, G Bond Plus; GBP, GC, Single Bond Plus; SBP, 3M ESPE) was applied using four different clinical strategies; apply immediately (Im), remove bleached surface 1 mm deep with a steel bur (Im/R), temporize and store in water for 1 week (1w), temporize, store for 1 week and remove the bleached surface (1w/R). They were filled with a resin composite (Clearfil AP-X, Kuraray Medical) incrementally. After 1 day storage in water, they were subjected to microtensile bond strength (µTBS) testing. Data was statistically analyzed using one-way ANOVA and LSD post hoc comparison test.
Results: Results of the µTBS are listed in the table below. Im/R and 1w/R improved the µTBSs significantly (p<0.05) regardless of the bonding systems used. SE produced a significantly higher µTBSs (p<0.05) than the other dentin bonding systems, when 1 mm dentin substance was removed Code SE GBP SBP Cont 61.9 ± 8.0a 45.9 ± 4.9 47.2±5.9d Im 22.3 ± 2.8 26.16 ± 3.0 30.3 ±2.3 Im/R 51.3 ± 3.1 35.9 ± 2.6b 40.1 ±3.7 1w 38.6 ± 3.11 37.5±2.61,2,b,c 44.6 ±5.32 1w/R 59.6 ± 4.1a 39.7 ± 4.8c,3 46.8 ±4.03,d Groups with same superscript letters in each column and numbers in each row are not significantly different (p<0.05)
Conclusion: Removal of the bleached dentin immediately or 1 week after bleaching improved the µTBSs to dentin in non-vital teeth.