The effects of pH on N-methacryloyl glycine primer on bond strength to acid-etched dentin.
To develop a more effective adhesive primer, it is imperative to understand the adhesion mechanisms of the resin to the demineralized dentin through a dentin primer. When the bonding agent was directly applied to the dentin etched by 40 wt % phosphoric acid without a primer pretreatment, the bond strength of the resin to the dentin was 5 MPa. Conversely, when the demineralized dentin was pretreated with the N-methacryloyl glycine (NM alpha A) primer solution with a pH value of 1.5, the bond strength increased considerably to 15 MPa. However, the bond strength dropped dramatically from 15 to 3 MPa when the sodium salt of NM alpha A was added, thereby increasing the pH value of the NM alpha A primer solution from 3.2 to 5.0. When the pH value was increased above 3.5 (pKa value), the number of ionized NM alpha A species increased in the solution. As a result, the bond strength of the resin fell to approximately 3 MPa. This result was obtained despite the 5-micron-thick hybrid layer that was created in the subsurface of the intertubular dentin. The number of unionized NM alpha A species increased by lowering the pH value below 3.5. As a result, the NM alpha A primer provided a higher bond strength of the resin to the demineralized dentin. In contrast, when 10 wt % citric acid containing 3 wt % ferric chloride was applied to the dentin, maximum bond strength was obtained when the pH value of the NM alpha A primer solution was 3.5. The pH dependency of the bond strength obtained following 10 wt % citric acid containing 3 wt % ferric chloride etching is different from the results obtained from 40 wt % phosphoric acid etching. This can be attributed to the difference in the characteristics of the demineralized collageous layer.
Nishiyama
N
N
Department of Dental Materials, Nihon University School of Dentistry at Matsudo, Chiba, Japan.
Suzuki
K
K
Asakura
T
T
Nakai
H
H
Yasuda
S
S
Nemoto
K
K
D000134:Acid Etching, Dental; D000818:Animals; D002417:Cattle; D002712:Chlorides; D003804:Dentin / Q000737:chemistry; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008689:Methacrylates / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry*; D013499:Surface Properties; D013718:Tensile Strength
D002712:Chlorides; D017220:Dentin-Bonding Agents; D005290:Ferric Compounds; D008689:Methacrylates; D019279:Resin Cements; C093041:N-methacryloyl glycine; D005998:Glycine; C024555:ferric chloride