IADR Abstract Archives
Interaction of 10-MDP or its Analog With Dentin
Objectives: To investigate the interaction between two acidic phosphate resin monomers with different spacer groups and dentin.
Methods: Methacryloyloxy-decyl-dihydrogen-phosphate (MDP) or methacryloyloxy-penta-propyleneglycol-dihydrogen-phosphate (MDP-analog) (both from Designer Molecules Inc.) was mixed with ethanol and water in 15:45:40 wt% ratio to form experimental primers. Hydroxyapatite powder was dispersed in the experimental primers for 2 h, washed with ethanol, dried and examined by Fourier transform-infrared spectroscopy (FT-IR) and 31P cross polarization-magic angle spinning nuclear magnetic resonance spectroscopy (31P CP-MAS NMR). Untreated apatite was used as control. 0.5 mL of 0.5 mg/mL MDP, 0.5 mg/mL MDP-analog or 0.125 mg/mL HEMA (control) were added to a chromatography column filled with demineralized bovine dentin powder in water-ethanol mixture, ethanol or a salt buffer. Spectrophotometric absorbance of the eluent was monitored at 220 nm to establish the relationship between absorption and elution volume of each tracer in different eluents and to calculate the recovery rate.
Results: FT-IR results showed characteristic C=O stretching vibration (1716 cm-1) of methacrylate carbonyl groups on MDP-treated apatite but not on MDP-analog-treated apatite. NMR results showed peak at 0.6 to -0.8 ppm for MDP-treated apatite (MDP-Ca salt formation) and peak at 1.498 ppm for the MDP-analog-treated apatite (CaHPO4.2H2O). Chromatography data showed that all HEMA eluded from the column in all mobile phases. MDP showed longer retention time in all mobile phases than the MDP-analog. Recovery rates of MDP from column were 100%, 36.5% and 18.9% in mixture, salt buffer and ethanol respectively, while those of MDP-analog were 96.2%, 100% and 33.5% respectively. Only one third of the monomer eluded the dentin column in ethanol compared to 100% in the mixture or salt buffer.
Conclusions: MDP showed better affinity to apatite than MDP-analog. The adsorbed monomer on dentin may be reversible, depending on solvent environment.
Methods: Methacryloyloxy-decyl-dihydrogen-phosphate (MDP) or methacryloyloxy-penta-propyleneglycol-dihydrogen-phosphate (MDP-analog) (both from Designer Molecules Inc.) was mixed with ethanol and water in 15:45:40 wt% ratio to form experimental primers. Hydroxyapatite powder was dispersed in the experimental primers for 2 h, washed with ethanol, dried and examined by Fourier transform-infrared spectroscopy (FT-IR) and 31P cross polarization-magic angle spinning nuclear magnetic resonance spectroscopy (31P CP-MAS NMR). Untreated apatite was used as control. 0.5 mL of 0.5 mg/mL MDP, 0.5 mg/mL MDP-analog or 0.125 mg/mL HEMA (control) were added to a chromatography column filled with demineralized bovine dentin powder in water-ethanol mixture, ethanol or a salt buffer. Spectrophotometric absorbance of the eluent was monitored at 220 nm to establish the relationship between absorption and elution volume of each tracer in different eluents and to calculate the recovery rate.
Results: FT-IR results showed characteristic C=O stretching vibration (1716 cm-1) of methacrylate carbonyl groups on MDP-treated apatite but not on MDP-analog-treated apatite. NMR results showed peak at 0.6 to -0.8 ppm for MDP-treated apatite (MDP-Ca salt formation) and peak at 1.498 ppm for the MDP-analog-treated apatite (CaHPO4.2H2O). Chromatography data showed that all HEMA eluded from the column in all mobile phases. MDP showed longer retention time in all mobile phases than the MDP-analog. Recovery rates of MDP from column were 100%, 36.5% and 18.9% in mixture, salt buffer and ethanol respectively, while those of MDP-analog were 96.2%, 100% and 33.5% respectively. Only one third of the monomer eluded the dentin column in ethanol compared to 100% in the mixture or salt buffer.
Conclusions: MDP showed better affinity to apatite than MDP-analog. The adsorbed monomer on dentin may be reversible, depending on solvent environment.