Self-curing, self-etching adhesive cement systems.
OBJECTIVE
To investigate the influence of the acid-base reaction between acidic monomers and amines on the polymerization behavior of self-etching, self-curing adhesives, determine the effect of the application mode on the shear bond strength and morphology, and elucidate the adhesion performance of such systems by shear bond strength measurements.


METHODS
The amine redox-initiator system N,N-di(2-hydroxyethyl)p-toluene (DEPT)/dibenzoyl peroxide (BPO) was selected to investigate the influence of the amine-base reaction on polymerization behavior. The PKa value of DEPT hydrochloride was measured by titration with NaOH. The influence of the pH value and DEPT concentration on the polymerization rate of methacrylates was investigated by exotherm time measurements. Three different application protocols of Multilink Primer (Ivoclar Vivadent) and Panavia 21 ED-Primer (Kuraray) were tested, 15 s passive vs 15 s agitation vs 60 s passive in combination with the corresponding resin luting material. The effects of these three application protocols were evaluated and monitored by both shear bond strength tests and SEM characterization of the surface morphology. The adhesion potential of these self-etching, self-curing luting systems was compared on enamel and dentin both directly after application and after 24 h.


RESULTS
The pKa of DEPT-HCl is 4.45. The polymerization rate of the DEPT-containing, self-etching, self-curing adhesive system is highly influenced by both the amine concentration and the pH value. In the case of Multilink, agitation of the primer mixture for 15 s, especially on dentin, resulted in a higher bond strength and a more pronounced removal of the smear layer. Multilink resulted in statistically higher bond strengths (p < 0.05) than Panavia 21 for both the enamel and dentin directly after application and for the dentin after 24 h.


CONCLUSIONS
Radical polymerization initiators used in self-curing systems are strongly adversely affected by acidic monomers incorporated in self-etching adhesives. However, if there is a good adjustment of these components and effects of adhesive application are taken in account, high bond strengths can be achieved.
Salz
Ulrich
U
Ivoclar Vivadent AG, Bendererstr 2, Schaan FL 9494, Liechtenstein. Ulrich.salz@ivoclarvivadent.com
Zimmermann
Jörg
J
Salzer
Tobias
T
D000134:Acid Etching, Dental / Q000379:methods*; D000269:Adhesives / Q000737:chemistry*; D000588:Amines / Q000737:chemistry; D000704:Analysis of Variance; D001840:Dental Bonding; D003745:Dental Enamel Permeability; D003799:Dental Stress Analysis; D003806:Dentin Permeability; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D044367:Phase Transition; D010710:Phosphates / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength; D013729:Terpenes / Q000737:chemistry; D014052:Toluidines / Q000737:chemistry
D000269:Adhesives; D000588:Amines; C093719:Panavia TPN-S; D010545:Peroxides; D010710:Phosphates; D019279:Resin Cements; D013729:Terpenes; D014052:Toluidines; C502351:multilink adhesive system; C048339:camphoroquinone; C038496:N,N-bis(2-hydroxyethyl)-4-toluidine