Bonding ability of Resin-bonding Systems containing Phosphonic acid Adhesive Monomer

Objectives: The characteristics of our S-PRG filler-containing, self-etching 2-step bonding system (FL-BOND II), developed with the introduction of Pre-Reacted Glass-ionomer technology (PRG technology) and a new phosphonic acid adhesive monomer (6-MHPA), were previously reported (#1589, IADR2007). This study aimed to evaluate the effectiveness of 6-MHPA on bonding strength to tooth structure by extensively comparing the bonding properties of three kinds of bonding systems which contain 6-MHPA and employ different bonding components/procedures.

Methods:An experimental material used was a new experimental self-etching 1-component bonding system (SI-R20603:B) containing 6-MHPA. For comparison, 6-MHPA-containing bonding systems (FLUORO BOND SHAKE ONE:FS, FL-BOND II:FL) were used. Bovine incisors were flat-ground into enamel or dentin using 600-grit abrasive paper. Bonding systems(B,FS,FL)/restorative(BEAUTIFIL II) were adhered to enamel or dentin. The specimens were stored in water at 37°C for 24h., and evaluated for shear bond strength (SBS) using a universal testing machine (Instron 5567).

Results: Although there was no significant difference in SBS among 3 bonding systems that contain 6-MHPA and employ different bonding components/procedures, the 2-step system FL showed the highest SBS. There was no significant difference in SBS between enamel and dentin for each bonding system, either SBS to enamel and to dentin were nearly equal and stable for each system.

Material	Component	Bonding procedure	Cure mechanism	SBS [MPa]
				To enamel	To dentin
B	1-component: Bond	1-step	Light-cure	16.58* (2.50)	19.20* (3.16)
FS	2-component : Bond A, Bond B	1-step	Light&Chemical-cure Acid-base reaction	17.05* (4.57)	16.28* (2.39)
FL	2-component: Primer, Bond	2-step	Light-cure	21.73* (4.08)	21.28* (3.71)

*No significant difference (ANOVA, Tukey's test, p<0.05), ( ):S.D.

Conclusion: It is suggested that being less subject to the influence of curing modes attributable to coexisting components such as water and polymerization catalysts, 6-MHPA is an effective adhesive monomer that provides stable bonding strength to tooth structure.