Further characterization of tetracycline's quantitative binding to dentin

Unerupted human third molar crown segments were used to measure the change in the concentration of ³H-tetracycline that occurs when it moves across dentin from pulpal to occlusal surfaces. When 1.25, 2.5, and 5×10^-5M³H-tetracycline were filtered across dentin, binding increased by 21, 51, and 69%, respectively. When the same concentrations of ³H-tetracycline were preloaded onto crown segments and eluted with 1.1×10^-3M nonradioactive tetracycline, the percentage of elution of ³H-tetracycline was not significantly different over time. When preloaded ³H-tetracycline was displaced by diffusion with water or 1.1×10^-3M nonradioactive tetracycline, there were no significant differences. There was a significant difference between the rate of displacement of 1.25×10^-5M³H-tetracycline and the other two preloaded concentrations when 5.8×10^-4M³H-tetracycline/tetracycline was used as the eluant. These data suggest that the binding of ³H-tetracycline to dentin was concentration dependent and that ³H-tetracycline binds nonspecifically and reversibly.