Delayed Effect of Wheat Starch in Foods on the Intraoral Demineralization of Enamel

Abstract

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. The present observations may help in understanding earlier conflicting reports on the cariogenic potentials of starch-containing foods.

Sugars – The Arch Criminal?

“…Some methods in particular, such as the indwelling plaque pH method, seem to be very sensitive to even low sugar foods that are not normally implicated in dental caries, and may accentuate Zero food retention, creating a worst case scenario [Edgar and Geddes, 1986]. Starches have also been shown to have cariogenic potential in many model systems, including in vitro models [Renz and Bibby, 1989], plaque acidity models [Lingström et al, 1993], animal caries models [Firestone et al, 1982;Mundroff et al, 1990] and in situ caries models [Brudevold et al, 1988;Kashket et al, 1994;Lingström et al, 1994;Pollard, 1995]. However, definitive data in humans are lacking [Lingström et al, 2000], suggesting that some degree of caution should be used when interpreting results from these models.…”

Food Starches and Dental Caries

“…An intra-oral method has been developed that follows de-or remineralization of blocks of human enamel or dentin, or of bovine enamel, that are covered by a layer of S. mutans cells so as to mimic dental plaque (Brudevold et al, 1985;Kashket et al, 1994). Studies with this model have shown that raw and cooked wheat starch induced negligible and mild demineralization, respectively (Brudevold et al, 1985), whereas boiled gelatinized wheat starch gels (10, 15, or 20% starch) induced significant demineralization and significant pH drops (minimum pH of 4.8-5.0) (Brudevold et al, 1988).…”

“…For example, the temperature at which rice starch begins to gelatinize increases from 85.3 to 111.3°C when the water-starch ratio drops from 2.0 to 0.75 (French, 1983;Lund, 1983Lund, , 1984. The starches in baked products such as bread are prepared with low levels of water and appear to be only partially gelatinized (Osman, 1967 (Neff, 1967;Imfeld, 1983;Kashket et al, 1994Kashket et al, , 1996. Maltose fermentation requires bacterial adaptation under certain conditions (Kashket et al, 1994).…”

“…The starches in baked products such as bread are prepared with low levels of water and appear to be only partially gelatinized (Osman, 1967 (Neff, 1967;Imfeld, 1983;Kashket et al, 1994Kashket et al, , 1996. Maltose fermentation requires bacterial adaptation under certain conditions (Kashket et al, 1994). In humans, however, plaque bacteria appear to be adapted and can ferment this sugar without delay (Neff, 1967;Imfeld, 1983;Lingstrbm et al, 1993a).…”

Effects of α-Amylase and Its Inhibitors on Acid Production from Cooked Starch by Oral Streptococci

“…Because of the adhesiveness of starchy foods, they are easily retained in the dentition [Lingström and Birkhed, 1993], and thus a continuous supply of carbohydrate derived from salivary starch digestion could help to maintain a low plaque pH for a long time [Lingström and Birkhed, 1993;Kashket et al, 1994]. To address the adhesiveness of starchy foods as well as the diffusion of starch and acidic end products within dental plaque, research using biofilm models could be valuable [Kashket et al, 1994;Duarte et al, 2008].…”