There is considerable evidence for an association between dental caries 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 system that utilized palatal appliances containing blocks of bovine enamel. The enamel surfaces were covered with either a filter paper disc to trap sugars or a layer of Streptococcus mutans to metabolize the sugars and bring about enamel demineralization. Demineralization was determined as an increase in porosity with respect to iodide ions (delta Ip). Measurements revealed a rapid elevation and maintenance of high levels of maltose in the plaque space after ingestion of the unsweetened or sweet cookies. Entrapped food particles appeared to serve as a reservoir of maltose. Unsweetened cookies brought about enamel demineralization, but the pH of the streptococcal plaque fell slowly, and the initiation of demineralization was delayed. Thus, delta Ip and plaque pH were -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 streptococci to metabolize maltose. Once induced, delta Ip rose rapidly and reached a maximum at 45 min. Sweet cookies released sucrose and maltose and brought about a rapid onset of demineralization. In summary, the data demonstrated (1) that maltose was released rapidly from unsweetened cookie particles and diffused into the plaque space of the model system and (2) that maltose-dependent demineralization of enamel required time for the induction of the streptococcal cells.(ABSTRACT TRUNCATED AT 250 WORDS)