Reactivity of the components of tooth structure

Abstract

Abstract A restorative material capable of adhering to tooth structure is greatly needed. Bonding is complicated by the complex nature of tooth structure as well as the mechanical, toxicologic, and bacteriologic conditions which occur in the oral cavity. Heats of immersion (-δ H w ) measurements for dentin, enamel, and anorganic whole tooth tissue of known specific surface have been used to study the reactivity and degree of surface modification produced by various ions and functional groups in an aqueous environment. A decrease in the - δH w value of dentin in water from 10.3 cal/gm (4100 ergs/cm 2 ) to 4.02 cal/gm (1590 ergs/cm 2 ) in 2–40% aqueous solutions of organic solvents suggests the strengthening of electrostatic bonds between polar groups of the collagenous matrix of dentin. In absolute ethanol and hexane, dentin absorbs heat indicating the weakening of hydrophobic bonds. The - δH w values for anorganic whole tooth in aqueous solutions of organic solvents are not appreciably different from those obtained in water (109 ergs/cm 2 ). The presence of NO 2 − , NO 2 − , CNS − , SO 4 2− , and I − , at pH 5 depressed the - δH w of dentin to 4.8 cal/gm (1910 ergs/cm 2 ). Other anions (F − and Cl − ) had no effect. At pH 8, however, anions did not alter the - δH w of dentin. The addition of aldehyde groups to the liquid adsorbate at pH 8 resulted in the lowering of the apparent - δH w value of dentin. Significant changes in - δH w values for anorganic whole tooth were not observed in the presence of anions or aldehyde groups. The surface of dentin may be modified by treatment with nonpolar solvents. Ionic bonding to exposed polar groups can be achieved at the optimal pH.