Effect of 2-(Methacryloxy)ethyl Phenyl Hydrogen Phosphate on Adhesion to Dentin T. WANG' and N. NAKABAYASHI2 Division of Organic Materials, Institute for Medical and Dental Engineering, Tokyo Medical and Dental University, 2-3-10, Surmgadai, Kanda, Tokyo 101, Japan
A variety of methacrylate-based materials has been developed with the capacity of adhering to dentin. This study investigated the effectiveness of 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) for bonding 5% phenyl-P in methyl methacrylate (MMA) to dentinal surfaces. Polymerization of the phenyl-P/MMA monomer was initiated by partially oxidized tri-n-butyl borane catalyst (TBB). The mean tensile bond strength of 5% phenyl-P in MMA to dentin that was pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride, abbreviated as 10-3, was found to be 10.5 MPa. Scanning electron microscope examination demonstrated the formation of a transitional or "hybrid" layer of resin-reinforced dentin, created by the intermingling and entanglement of polymerized resin with collagen bundles exposed by dentin pre-treatment with 10-3, an effective remover of the dentinal smear layer. This "hybrid" layer or zone was essential for high tensile bond strength to be attained. Phenyl-P was found to be effective in promoting monomer diffusion and impregnating monomer into demineralized dentinal surfaces. The formation of the "hybrid" layer of resin-reinforced dentin followed in situ resin polymerization initiated by partially oxidized tri-n-butyl borane (TBB). Ferric (Fe3+) ions deposited on dentinal surfaces from the 10-3 solution also acted to improve monomer diffusion and entanglement with demineralized dentin, and facilitated the formation of the "hybrid" layer/zone.
J Dent Res 70(1):59-66, January, 1991
Introduction. Methacrylate monomers that contain both hydrophobic and hydrophilic groups have been developed. These groups improve the adhesive strength of resins to tooth structure by promoting the inter-penetration and entanglement of methacrylate-based monomers into dentinal surfaces (Nakabayashi et al., 1982a; Nakabayashi, 1984). Examples of such methacrylates include 4-(methacryloxyethyl) trimellitic anhydride (4-META) (Takeyama et al., 1978), 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) (Yamauchi, 1986), and phenyl-P derivatives (Nakabayashi and Kanda, 1988). An adhesive system designated as 5% 4-META/MMA-TBB [5% of 4-(methacryloxyethyl) trimellitic anhydride in methyl methacrylate and containing a partially oxidized tri-n-butyl borane as the initiator] has been widely studied as a bonding agent for tooth substrates (Nakabayashi, 1984), metals (Matsumura and Nakabayashi, 1988; Tanaka et al., 1988), and porcelains (Maeda et al., 1987). The reported adhesive strength of a poly(methyl methacrylate) (PMMA) rod bonded to dentin with 5% phenyl-P/MMAReceived for publication February 21, 1989 Accepted for publication September 14, 1990 'On leave from Dental Materials Laboratory, Stomatology Institute of Beijing Medical University, Hai Dian District, Beijing, China 2To whom correspondence and reprint requests should be addressed
TBB [5% of 2-(methacryloxy)ethyl phenyl hydrogenphosphate in TBB-initiated methyl methacrylate] resin was 13 MPa. These tested dentin samples had been pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride (10-3) (Nakabayashi et al., 1981; Kiyomura et al., 1987). In the present study, the influence of phenyl-P in MMATBB resin on dentin bonding was compared with that of 4META in MMA-TBB resin. The adhesive interface of phenylP/MMA-TBB resin and bovine dentin was examined by scanning electron microscopy, before and after chemical modifications of test specimens, to investigate the bonding mechanism.
Materials and methods. Bonding of a PMMA rod to bovint dentin with phenyl-PI MMA-TBB resin. -A flat surface was prepared on samples of freshly extracted or frozen bovine teeth. Specimens were ground with 600-grit Emery paper under a stream of water. These were then washed and blown dry with compressed air. The ground surfaces were treated with 40 ,uL of 10-3 solution (10% citric acid/3% ferric chloride, purchased from Tokyo Kasei Co., Tokyo, Japan) for 30 s, rinsed with water for 15 s, and blown dry. A piece of tape containing a 5.4-mm-diameter hole was attached securely to each test specimen. This served to standardize the area of dentin surface available for bonding. The bonding resin paste-a mixture of 0.1 g of 5% phenyl-P (Yamauchi, 1986)/MMA (Mitsubishi Rayon Co., Tokyo, Japan), TBB liquid (Sunmedical Co., Ltd., Kyoto, Japan), and 0.1 g of poly(methyl methacrylate) (PMMA) powder (Sunmedical Co., Ltd., Kyoto, Japan)-was then applied to the exposed dentin of test samples with a brush-on technique. Finally, a 6mm-diameter PMMA rod (Mitsubishi Rayon Co., Tokyo, Japan) was bonded perpendicularly to the adhesive resin on the flat dentin surfaces of the specimens to serve as a handle (Tanaka et al., 1988). This entire assembly was left standing at room temperature for 30 min before the test specimens were placed in 370C water for 24 h. Tensile bond strength was measured after the storage period with a universal testing machine (Autograph DSS 500, Shimadzu Co., Kyoto, Japan) at a cross-head speed of 2 mm/min. Each test was performed on six specimens. Differences among means of the four groups were tested for statistical significance by ANOVA and Duncan's New Multiple Range test (Table). Scanning electron microscope examination. -The CMS-501 TABLE
TENSILE BONDING STRENGTH OF PHENYL-P/MMA-TBB RESIN TO PRE-TREATED BOVINE DENTIN (MPa) (MEAN + S.D.) Phenyl-P Pre-treatment wt % 10-3 65% H3PO4* 0 3.6 + 1.0 4.1 + 1.3 5 10.5 ± 1.8** 2.7 ± 0.6 * 10 pL for 30 s. ** Significantly different (p
A variety of methacrylate-based materials has been developed with the capacity of adhering to dentin. This study investigated the effectiveness of 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) for bonding 5% phenyl-P in methyl methacrylate (MMA) to dentinal surfaces. Polymerization of the phenyl-P/MMA monomer was initiated by partially oxidized tri-n-butyl borane catalyst (TBB). The mean tensile bond strength of 5% phenyl-P in MMA to dentin that was pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride, abbreviated as 10-3, was found to be 10.5 MPa. Scanning electron microscope examination demonstrated the formation of a transitional or "hybrid" layer of resin-reinforced dentin, created by the intermingling and entanglement of polymerized resin with collagen bundles exposed by dentin pre-treatment with 10-3, an effective remover of the dentinal smear layer. This "hybrid" layer or zone was essential for high tensile bond strength to be attained. Phenyl-P was found to be effective in promoting monomer diffusion and impregnating monomer into demineralized dentinal surfaces. The formation of the "hybrid" layer of resin-reinforced dentin followed in situ resin polymerization initiated by partially oxidized tri-n-butyl borane (TBB). Ferric (Fe3+) ions deposited on dentinal surfaces from the 10-3 solution also acted to improve monomer diffusion and entanglement with demineralized dentin, and facilitated the formation of the "hybrid" layer/zone.
J Dent Res 70(1):59-66, January, 1991
Introduction. Methacrylate monomers that contain both hydrophobic and hydrophilic groups have been developed. These groups improve the adhesive strength of resins to tooth structure by promoting the inter-penetration and entanglement of methacrylate-based monomers into dentinal surfaces (Nakabayashi et al., 1982a; Nakabayashi, 1984). Examples of such methacrylates include 4-(methacryloxyethyl) trimellitic anhydride (4-META) (Takeyama et al., 1978), 2-(methacryloxy)ethyl phenyl hydrogenphosphate (phenyl-P) (Yamauchi, 1986), and phenyl-P derivatives (Nakabayashi and Kanda, 1988). An adhesive system designated as 5% 4-META/MMA-TBB [5% of 4-(methacryloxyethyl) trimellitic anhydride in methyl methacrylate and containing a partially oxidized tri-n-butyl borane as the initiator] has been widely studied as a bonding agent for tooth substrates (Nakabayashi, 1984), metals (Matsumura and Nakabayashi, 1988; Tanaka et al., 1988), and porcelains (Maeda et al., 1987). The reported adhesive strength of a poly(methyl methacrylate) (PMMA) rod bonded to dentin with 5% phenyl-P/MMAReceived for publication February 21, 1989 Accepted for publication September 14, 1990 'On leave from Dental Materials Laboratory, Stomatology Institute of Beijing Medical University, Hai Dian District, Beijing, China 2To whom correspondence and reprint requests should be addressed
TBB [5% of 2-(methacryloxy)ethyl phenyl hydrogenphosphate in TBB-initiated methyl methacrylate] resin was 13 MPa. These tested dentin samples had been pre-treated with an aqueous solution of 10% citric acid/3% ferric chloride (10-3) (Nakabayashi et al., 1981; Kiyomura et al., 1987). In the present study, the influence of phenyl-P in MMATBB resin on dentin bonding was compared with that of 4META in MMA-TBB resin. The adhesive interface of phenylP/MMA-TBB resin and bovine dentin was examined by scanning electron microscopy, before and after chemical modifications of test specimens, to investigate the bonding mechanism.
Materials and methods. Bonding of a PMMA rod to bovint dentin with phenyl-PI MMA-TBB resin. -A flat surface was prepared on samples of freshly extracted or frozen bovine teeth. Specimens were ground with 600-grit Emery paper under a stream of water. These were then washed and blown dry with compressed air. The ground surfaces were treated with 40 ,uL of 10-3 solution (10% citric acid/3% ferric chloride, purchased from Tokyo Kasei Co., Tokyo, Japan) for 30 s, rinsed with water for 15 s, and blown dry. A piece of tape containing a 5.4-mm-diameter hole was attached securely to each test specimen. This served to standardize the area of dentin surface available for bonding. The bonding resin paste-a mixture of 0.1 g of 5% phenyl-P (Yamauchi, 1986)/MMA (Mitsubishi Rayon Co., Tokyo, Japan), TBB liquid (Sunmedical Co., Ltd., Kyoto, Japan), and 0.1 g of poly(methyl methacrylate) (PMMA) powder (Sunmedical Co., Ltd., Kyoto, Japan)-was then applied to the exposed dentin of test samples with a brush-on technique. Finally, a 6mm-diameter PMMA rod (Mitsubishi Rayon Co., Tokyo, Japan) was bonded perpendicularly to the adhesive resin on the flat dentin surfaces of the specimens to serve as a handle (Tanaka et al., 1988). This entire assembly was left standing at room temperature for 30 min before the test specimens were placed in 370C water for 24 h. Tensile bond strength was measured after the storage period with a universal testing machine (Autograph DSS 500, Shimadzu Co., Kyoto, Japan) at a cross-head speed of 2 mm/min. Each test was performed on six specimens. Differences among means of the four groups were tested for statistical significance by ANOVA and Duncan's New Multiple Range test (Table). Scanning electron microscope examination. -The CMS-501 TABLE
TENSILE BONDING STRENGTH OF PHENYL-P/MMA-TBB RESIN TO PRE-TREATED BOVINE DENTIN (MPa) (MEAN + S.D.) Phenyl-P Pre-treatment wt % 10-3 65% H3PO4* 0 3.6 + 1.0 4.1 + 1.3 5 10.5 ± 1.8** 2.7 ± 0.6 * 10 pL for 30 s. ** Significantly different (p
