DELAYED-EFFECT OF WHEAT-STARCH IN FOODS ON THE INTRAORAL DEMINERALIZATION OF ENAMEL

There is considerable evidence for an association between dental carie s and food starches. However, the intraoral utilization of starch may be quite complex, giving rise to conflicting results. Demineralization induced by unsweetened cookies was examined in an intraoral model sys tem that utilized palatal appliances containing blocks of bovine ename l. The enamel surfaces were covered with either a filter paper disc to trap sugars or a layer of Streptococcus mutans to metabolize the suga rs and bring about enamel demineralization. Demineralization was deter mined as an increase in porosity with respect to iodide ions (delta Ip ). Measurements revealed a rapid elevation and maintenance of high lev els of maltose in the plaque space after ingestion of the unsweetened or sweet cookies. Entrapped food particles appeared to serve as a rese rvoir of maltose. Unsweetened cookies brought about enamel demineraliz ation, but the pH of the streptococcal plaque fell slowly and the init iation of demineralization was delayed. Thus, delta Ip and plaque pH w ere -0.3+/-1.3 U and 6.1+/-0.3, respectively, after 15 min. The delay was shown to be related to the need to induce the acidogenic streptoco cci to metabolize maltose. Once induced, delta Ip rose rapidly and rea ched a maximum at 45 min. Sweet cookies released sucrose and maltose a nd brought about a rapid onset of demineralization. In summary, the da ta demonstrated (1) that maltose was released rapidly from unsweetened cookie particles and diffused into the plaque space of the model syst em and (2) that maltose-dependent demineralization of enamel required time for the induction of the streptococcal cells. The present observa tions may help in understanding earlier conflicting reports on the car iogenic potentials of starch-containing foods.