Degradation of single bottle type self-etching primer effectuated by the primer's storage period.
OBJECTIVE
To examine the hydrolytic stability of the functional methacrylate monomer utilized in single bottle type self-etching primers, by using the 13C nuclear magnetic resonance (NMR) technique in order to understand why the bond strength of resin to the dentin decreased, when the primer's storage duration was prolonged.


METHODS
After deuterium oxide was added to the Mega Bond Primer (MB), or Unifil Bond Primer (UB), the MB or UB solutions were then stored at 37 degrees C for 0, 3, and 10 weeks, respectively. At the end of the storage periods, 13C NMR observations of the MB or UB solution were performed at 25 degrees C by using an EX-270 spectrometer.


RESULTS
The acidic and/or hydrophilic methacrylate monomer utilized in single bottle type self-etching primers became altered during the primer's storage period. Alteration of the functional monomer was possible since the acidic monomer, utilized in the self-etching primer, could supply sufficient amounts of hydronium ions, which were the result of the dissociation of the acidic group in the acidic monomer. The degradation of the primer, caused by the alteration of the functional monomer, would result in the degradation of the etching and/or priming efficacy on the tooth. The bond strength, as a result, would become decreased as the storage period was prolonged.
Fujita
Kou
K
Department of Dental Caries Control and Aesthetic Dentistry, Nihon University School of Dentistry at Matsudo, Chiba, Japan. fujita.kou@nihon-u.ac.jp
Nishiyama
Norihiro
N
D000134:Acid Etching, Dental; D000180:Acrylic Resins / Q000737:chemistry; D004355:Drug Stability; D004356:Drug Storage; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D013997:Time Factors
D000180:Acrylic Resins; C472989:Megabond self-etching primer; D008689:Methacrylates; D011109:Polymethacrylic Acids; D019279:Resin Cements; C407402:Unifil Bond; C005044:hydroxyethyl methacrylate; C031172:4-META resin