Long-term Microtensile Bond Strength of Experimental Fluoride-Releasing Bonding Agent

Objective: To test the microtensile bond strength of an experimental fluoride-releasing bonding agent after storage in water for 3 months and 6 months. Methods: A long-chain chelating monomer containing bis(carboxymethyl)-L-lysine and its zirconium-fluoride chelate (fluoride-releasing monomer) were synthesized and used to formulate an experimental fluoride-releasing bonding agent (Exp Bond) as previously reported (IADR 07, Abst #137). Exp Bond has shown significantly higher fluoride release than the commercial bonding agents Clearfil SE Bond and Clearfil Protect Bond (Kuraray) when they are used with fluoride-releasing composites. Microtensile bond strengths (MTBS) of the above three bonding agents on ground enamel or dentin of extracted human teeth were tested after the sectioned bar specimens (1x1 mm cross-section, n=15) were stored in distilled water at 37^oC for 24 hours, 3 months and 6 months, respectively. The data were analyzed using ANOVA and post hoc tests. Results: Microtensile bond strength (mean±SD)

Time	SE Bond Enamel	Protect Bond Enamel	Exp Bond Enamel	SE Bond Dentin	Protect Bond Dentin	Exp Bond Dentin
24 hours	20.76±5.97	16.37±2.94	26.35±6.99	34.18±10.20	53.67±11.60	31.35±6.72
3 Months	18.16±3.01	17.05±2.21	24.35±6.52	21.15±7.19	26.23±7.60	24.70±4.43
6 Months	19.60±9.04	17.21±3.15	─	21.75±5.81	18.43±7.84	18.34±5.80

The MTBS of all three bonding agents on enamel have no significant change after 3 and 6 months. However, the MTBS of all three bonding agents on dentin decreased significantly (p<0.05). The Exp Bond has higher MTBS on enamel after 3 months than SE Bond and Protect Bond (p<0.05). Exp Bond has MTBS on dentin similar to SE Bond and Protect Bond after 3 months and 6 months. Conclusion: The experimental fluoride-releasing bonding agent has long-term bond strength similar to commercial bonding agents. Supported by NIH/NCRR-COBRE grant (P20RR020160-1).