Limitations in the Intraoral Demineralization of Bovine Enamel

Abstract

A model system was used to examine the relation between the duration of plaque pH fall and enamel demineralization following the intake of dietary carbohydrate in humans. Subjects wore palatal appliances containing blocks of bovine enamel covered with Streptococcus mutans IB 1600, and rinsed with 5 or 10% sucrose. Changes in iodide penetrability (delta Ip) of the enamel, and the pH and extracellular calcium and inorganic phosphate (Pi) concentrations of the streptococcal plaque were determined. Following rinses with 5% sucrose, delta Ip increased with time and reached a maximum (11.2 ± 2.2 units) at 45-60 min although the S. mutans plaque remained acidic (pH = 4.8 ± 0.6). After 10% sucrose, the maximum (14.7 ± 3.1 units) was reached while the plaque pH was 4.0 ± 0.3. Second rinses with sucrose increased delta Ip at most by 30%. Thus, demineralization did not persist throughout the period of low plaque pH, but occurred primarily during the early phase of plaque acidogenesis. Enamel demineralization appeared to be limited by factors other than the pH of the streptococcal plaque. Calcium concentrations in the S. mutans plaque rose to a maximum of 10.9 ± 2.8 mEq/1 at 30 min after the 5% sucrose rinses, then fell; Pi reached a stable level of 12.2 ± 2.3 mEq/1 by 60 min. Calculations showed that conditions approached saturation with respect to enamel and dicalcium phosphate dihydrate as demineralization reached a maximum. Demineralization appeared to be limited at low plaque pH, therefore, by the accumulation of high levels of mineral ions in the streptococcal plaque. These findings suggest that the effects on the natural dentition will be limited when consuming a number of carbohydrate-containing foods during a meal.

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

“…Interestingly, the results with the sweet cookies showed that demineralization reac hed a maximum, so that the entrapped cookie particles did not sustain a continued, progressive demineralization. This apparent limit to the degree of demineralization was similar to that encountered with repeated rinses of sucrose [Kashket and Yaskell, 1992], Evidently, the initial concentrations of plaque sugar are most important in determining the subse quent course and degree o f enamel demineralization.…”

Mineral Ions in the Fluid of Biofilms Formed on Enamel and Dentine Shortly after Sugar Challenge

“…Raw calculations of the ion activity products of the fluids suggest that saturation with respect to hydroxyapatite and fluorapatite is being reached (considering 40% of total Ca in the fluid free [Vogel et al, 1998[Vogel et al, , 2000a and ionic strength is 150 m M [Margolis et al, 1988], pKIAP HAp ; 119, pKIAP FAp ; 112, Chemist version 1.0.1, Salt Lake City, Utah, USA). This indicates that the increase in Ca concentration in the fluid would be a self-limiting step for dental demineralization soon after exposure of the biofilm to carbohydrates, as discussed previously [Kashket and Yaskell, 1992].…”

Effects of Fluoride-Supplemented Sucrose on Experimental Dental Caries and Dental Plaque PH

“…Using 10% sucrose+F at 10 ppm, we have noted no differences in plaque pH changes compared with using sucrose alone. Lack of F effect of these levels on the plaque pH response to sucrose supports the findings of Kashket and Yaskell (1992). Using intra-oral appliances and 10% sucrose rinses, Pearce et al (1992) reported pH drops to 4.0 and 4.8, but these changes did not correlate with enamel demineralization.…”