Blocks of bovine enamel covered with a layer of Streptococcus mutans cells were mounted in specially-designed holders in a prosthesis and carried intraorally for 2 h. Measurements of the iodide permeability (Ip) of the blocks before and after intra-oral exposure showed an increase in Ip (+ΔIp), suggesting demineralization when the mouth was rinsed with a 10% sucrose solution at 0 and 60 min, but a decrease in Ip (––ΔIp), suggesting remineralization, after interoral exposure without rinsing. Repeated tests with sucrose rinses in 5 subjects showed good within and between-subject reproducibility of ΔIp. Acid production in the S. mutans cells layer from sucrose caused a typical decrease and subsequent increase in pH (‘Stephan’ curve). S. mutans cells released from the appliance during the test became eliminated from the mouth within 1 to 2 weeks.

No abstract

The ability of cooked starch (CS) and raw starch (RS)to cause intraoral enamel demineralization was determined by the iodide permeability (Ip) test which registers demineralization of enamel by an increase in Ip (+ΔIp) and mineralization by a decrease in Ip (––ΔIp). 5 subjects, who wore a palatal prosthesis holding 8 bovine enamel blocks covered by a layer of Streptococcus mutans swished 15 g of a 10% jelly of CS or 15 ml of a suspension of RS in the mouth for 1 min, and the change in Ip was determined after a period of 45 min. The salivary clearance of maltose during the experiment was also determined. CS gave + ΔIps which were statistically significant in 2 of the 5 subjects. The mean ± SE was +3.6 ± 1.47·10^––10 M of I, indicating mild demineralization. RS gave ΔIps in 4 of the 5 subjects (mean ––6.7 ± 1.87). The rate of salivary clearance of maltose varied considerably among the subjects but CS consistently showed higher initial concentrations than RS. Maximal salivary maltose concentrations ranged from 1,920 to 3,052 mg% for CS and from 523 to 1,041 mg% for RS. The range of the clearance time was from 19.3 to 44.9 min for CS and from 14.7 to 48.2 min for RS. Plotting maltose concentrations against time gave curves which followed an exponential equation. The areas under the curves were calculated, and correlation with the respective Δlps gave r = 0.78. It was concluded that RS had no demineralization potential, and that the demineralizing ability of CS was related to rapid hydrolysis and high early concentrations of maltose in saliva, and unrelated to clearance time.

A newly-developed intra-oral enamel demineralization test was used to evaluate the effect of supplementation of a 10% sucrose solution with various components on enamel demineralization induced by the sucrose. Five human subjects wore a palatal prosthesis holding eight blocks of subsurface bovine enamel covered with a layer of S. mutans cells. The test involved rinsing with sucrose solution or with sucrose solution supplemented with 0.162 mol/l of different calcium salts or equivalent concentrations of Na-, K-, and Sr salts; rinsing was for one min at times zero and 45 min of the 90-minute test period. Ca-propionate, Ca-acetate, and Ca-levulinate completely inhibited sucrose-induced enamel demineralization; Ca-chloride, Ca-lactate, and Ca-ascorbate gave from 65-75%, and K-acetate, Na-lactate, and Sr-lactate 39, 25, and 18% inhibition, respectively. Consideration of the anion dissociation constants and the Ca-anion association constants of the salts suggests that the observed inhibition is caused mainly by common ion effects and, to a lesser extent, by buffer effects.

Six subjects wore intraoral devices carrying bovine enamel blocks covered with a layer of Streptococcus mutans. They swished solutions of 5% glucose or maltose, or sols or gels of 3, 5, 10, 15, or 20% gelatinized wheat starch in the mouth for 3 × 1 min. Demineralization was measured after 45 min by determining the change in iodide permeability (delta Ip) of the enamel. Spittings of the administered materials and samples of saliva, taken at intervals during the test, were analyzed for maltose, and the time of clearance was calculated. Demineralization was greatest for glucose followed by maltose, the starch gels, and the sols. The latter gave close to zero scores. The salivary clearance time increased with increase in concentration of the starch. Although the starch was hydrolyzed rapidly in the mouth, its oral retentiveness was greater than that of the maltose rinse. Demineralization was closely correlated with the final pH of the S. mutans cell layer. The data indicate that the starch in baked or cooked foods may have a significant demineralization potential and that it enhances oral retentiveness.