A new primer for tooth-bonding was developed.This primer consists of phytic acid (PYA), which acts as both etchant and chelating agent, and SnF2 as a source of metallic ion. First, human teeth are treated with 7% aqueous solution of PYA and then with 3% aqueous solution of SnF2.It is expected that Sn2+is fixed on the tooth surface by chelation with PYA in this 2-step treatment, and then some interactions between phosphoric or carboxylic acid groups of functional monomers or polycarboxylic acid contained in cements and Sn2+contribute to bonding of cements to the teeth at cementing.
In order to confirm this hypothesis, this primer was applied to bonding of 4 adhesive resin and one glass ionomer cements to human dentin.The treatment effects were compared with those of the conditioner (control) attached to each product.
The following results were obtained:
1.The early shear bond strength (after 24 hours in an atomosphere of 100% RH at 37°C) obtained from specimens treated with PYA-SnF2 primer was equal to or higher than that of the controls in all cements examined.For Panavia 21, Imperva Dual/Bond and Fuji Bond, there were statistically significant differences between treatments with PYA-SnF2 primer and the attached conditioners.
2.After 5, 000 thermocycles, the shear bond strength to dentin treated with PYA-SnF2 primer was equal to or higher than that of the controls.For both treatments, however, the shear bond strength decreased significantly in comparison with that in early stage except for Panavia 21 with both treatments and Bistite Resin Cement with PYA-SnF2.
3. It is suggested that PYA-SnF2 primer effectively bonds both adhesive resin and glass ionomer cements to dentin and provides durable bonding.