The effect of sucrose and fat in cookies on salivation and oral retention in humans.

Six adults were served accurately weighed portions (about 5 g) of cookies varying in sucrose and fat content. The cookies were chewed and spat out at the time the subjects were ready to swallow. Additional spittings were collected at intervals up to two, three, and four min. Chewing time decreased with increase in sucrose, or with increase in fat. The volume of saliva in each spitting was calculated from its wet and dry weights, and it was assumed either (a) that saliva produced during chewing was not carried over in the retained food, or (b) that saliva was incorporated in the retained food in the same proportion as in the first spitting. Both approaches revealed that salivary flow rates were independent of cookie formulation, with two exceptions: (1) The cookie highest in sucrose produced a significantly higher flow rate during chewing, and (2) the fat-free cookie, which was hard to chew, elicited an elevated flow rate up to two min. The total volume of saliva for the entire experimental period was similar for all formulations, except the latter. Masticatory effects, therefore, appeared to predominate over sweetness stimulation, unless sugar content was very high. The volume of saliva in the food bolus at the time of swallowing correlated with chewing time. Oral clearance of the cookies did not give straight lines when logarithms of retained material were plotted against time. Initial clearance rates appeared to diminish with increasing sucrose and fat content of the cookies. Effects of sugar and fat on all parameters may reflect changes in cookie texture and the sizes of particles produced within the mouth.

Increased permeability of enamel to iodide ions following the ingestion of cookies varying in sucrose or fat content.

Experiments showed that the intraoral iodide permeability (Ip) method can be used in a reproducible and sensitive manner with solid foods. Ingestion of 5-gram portions of cookies made with defined concentrations of sucrose or fat led to an increased Ip (due to demineralization) of Streptococcus mutans-covered bovine enamel blocks in vivo. Demineralization increased with time to a maximum of 45 min, and the pH of the plaque dropped accordingly. Continued exposure in the mouth beyond 45 min led to an elevation of the pH and a decrease in delta Ip consistent with remineralization of the enamel. Control blocks worn without ingestion of cookies exhibited negative delta Ip values. Demineralization increased with increasing sucrose content of the cookies and reached a plateau when cookies containing 1.08 g sucrose per morsel were administered. Cookies prepared without added sucrose gave a high delta Ip. High fat content raised the delta Ip when sucrose was low. These findings are consistent with clinical and other observations, and emphasize the complex relation between foods and enamel demineralization.

Demineralization potential of different concentrations of gelatinized wheat starch.

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 X 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.

Enamel demineralization and the length of intra-oral exposure to different concentrations of glucose or sucrose.

Six subjects wore intra-oral devices carrying eight bovine enamel blocks which were covered with a layer of S. mutans. They rinsed their mouths for five sec, one min, or multiples of one min with a 5 or 10% glucose (G) solution. Demineralization was measured after 45 min by determining the change in iodide permeability (delta Ip) of the enamel. In addition, saliva samples, taken at intervals during the test, were analyzed for G, and the time of clearance (tc) was calculated. Demineralization scores (delta Ip) were consistently greater from the 10% than from the 5% G solution. Both solutions produced an increase in delta Ip with an increase in the rinsing time (tr). The G remaining in saliva after the rinse did not significantly affect delta Ip. The delta Ip scores showed good correlation with the final pH of the S. mutants cell mass, r = -0.77. For each rinse solution, the scores also showed good correlations with tr (r = 0.87 and 0.79) and much weaker correlations with tr + tc (r = 0.44 and 0.53). Continuous in vitro exposure to 1, 5, or 10% solutions of sucrose (S) in saliva for 30 min or more caused a linear increase in delta Ip with time with no concentration effects. A linear increase was also observed in vivo when a one-minute mouth-rinse with 10% solution of S was administered every 30 min. The findings indicate that significant demineralization may occur while carbohydrate foods are consumed, and that brushing the teeth or rinsing the mouth after meals may not be as effective against caries as is generally believed.

Sugar clearance from saliva and intra-oral spaces.

The clearance of glucose from saliva was compared with that from spaces located in an intra-oral appliance. The spaces (N = 8) were similar in shape and size to posterior interdental spaces and could be sampled with a microsyringe without removing the appliance from the mouth. The subjects (N = 5) rinsed their mouths with solutions of 5, 10, or 25% glucose. Samples were obtained from a pair of spaces and from saliva at standard intervals and were analyzed for glucose. The rate of glucose clearance was consistently slower from the spaces than from bulk saliva, as shown by higher concentrations and longer clearance times for the spaces. The clearance curves were similar in shape and were rectilinear when the logarithms of the concentrations were plotted against time. The rate of clearance from the spaces appears to be characteristic for an individual, as was also true of salivary clearance.

Effect of some salts of calcium, sodium, potassium, and strontium on intra-oral enamel demineralization.

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.

Enamel demineralization by mouthrinses containing different concentrations of sucrose.

Intra-oral enamel demineralization tests, involving rinsing with sucrose solutions (5, 1, 0.5, or 0.3%) at varying frequencies during a 1.5-hour period, showed that demineralization was a function of the total sugar dose (frequency of rinsing times concentration). Two rinses with a 5% solution caused demineralization, nine rinses were needed in the case of a 0.5% solution, and none occurred after nine rinses with a 0.3% solution. Remineralization was also observed and apparently occurred after exhaustion of the sucrose supply.

Enamel demineralization potential of dietary carbohydrates.

Mouthrinses with 5% solutions of different sugars were tested for their demineralizing effect on blocks of bovine enamel covered with a layer of S. mutans cells and carried in a palatal prosthesis. The extent of demineralization, as measured by the permeability of the enamel to iodide, was similar for fructose, glucose, and sucrose, less for maltose and lactose, and least for galactose.

The effect of enamel de- and remineralization on permeability to iodide and urea.

Blocks of bovine enamel subjected to de- and remineralization were measured for changes in permeability to iodide and urea. Results were similar, indicating that the diffusion pathways for the two species were comparable, and that sites for iodide binding did not appear to exit.

The relationship among the permeability to iodide, pore volume, and intraoral mineralization of abraded enamel.

The results indicate that Ip measurements are fairly closely related to the pore volume of the enamel to a depth of about 13 micrometer. A previous finding - that intraoral exposure produced substantial mineralization of abraded enamel after one h, and a slower rate of mineralization during the next two h - was confirmed, and it was shown that the rate of mineralization decreased with a decrease in the pore volume of the enamel. The rapid rate of intraoral mineralization represents a powerful mechanism for maintaining a fully mineralized enamel surface. The sensitivity of the Ip method demonstrated in this study, and the finding that Ip measurements relate to the pore volume of the enamel, coupled with previous findings that the increase in Ip produced by mild acid etching of intact enamel is proportional with the amount of dissolved Ca, indicate that the method provides valid measurement of intraoral de- and remineralization.

Intraoral mineralization of abraded dental enamel.

The iodide permeability (Ip) of abraded bovine enamel increased after short exposure to an acid buffer and decreased after short exposure to a mineralizing solution. Intraoral exposure gave a marked decrease in Ip after one h and a continued lesser decrease after two and three h. In vitro exposure to fresh and dialyzed saliva and various undersaturated solutions indicated that the intraoral decrease was due to mineralization rather than to pellicle formation. Analysis of the data also indicated that part of the mineral formed intraorally was more loosely bound to the enamel than that formed from an inorganic mineralizing solution. The rapid rate of the initial phase of intraoral mineralization shown in this study reveals a powerful mechanism for protecting the dentition against demineralization.

Effect of initial demineralization on the permeability of human tooth enamel to iodide.

Blocks of intact human enamel were exposed for four successive periods of 5 min to 2 ml of 10(-2) M K-acetate at pH 4.0, 4.5 and 5.0. The permeability to iodide (Ip) and the amount of Ca dissolved were determined after each exposure. The Ip values varied considerably, but for each block there was a consistent increase in Ip with increase in acid exposures, and the Ca-Ip relationship was linear at all pH levels. The slope and intercept of the regression lines varied widely, but the correlation coefficients showed close fit of the data. The mean Ip values after the same period of exposure at pH 4.0 and 4.5 were statistically different from those obtained at pH 5.0, but the differences between the pH 4.0 and 4.5 values were not. This discrepancy is attributed to dissolution of surface enamel by the pH 4.0 buffer. Because loss of surface enamel is minimized by partial saturation of the buffer with Ca and phosphate, and oral fluids contain high concentrations of these ionic species, the iodide method should give valid measurements of the demineralization produced intarorally by acid and cariogenic foods.

Dental fluorosis as related to the concentration of fluoride in teeth and bone.

Rats (N = 58), given a diet low in fluoride, were stomach-fed solutions of NaF and (NH4)3AIF6 in amounts corresponding to 3.3, 8.3, and 16.5 microgram of fluoride per gram of body weight. After five weeks, the incisors were scored for fluorosis and samples of the incisors and mandibles were analyzed for fluoride. Less fluoride was deposited in teeth and bone from AIF6, than from NaF at all dosage levels. Less fluorosis also developed from AIF6, except at the lowest dosage level, which produced very little fluorosis in either group. Both incisor fluoride and fluorosis scores increased with increases in ingestion of fluoride. In a larger group of rats (N = 101) that had been on different fluoride regimens, the fluoride concentrations of the incisors were grouped according to the fluorosis scroes. There was a consistent trend of increase in fluoride with increase in fluorosis scores, but each score had a wide range and overlap in fluoride concentrations.

Lead in enamel and saliva, dental caries and the use of enamel biopsies for measuring past exposure to lead.

Enamel biopsies taken from schoolchildren in a community where exposure to lead was a health hazard were analyzed for lead and fluoride. The children with high enamel lead had significantly higher caries scores than the children with low enamel lead, in spite of the fact that the high lead group also was higher in enamel fluoride. There was no increase in enamel lead with age. The lead in saliva was only a fraction of that in blood. Infants with lead poisoning showed higher saliva lead than a normal infant. The use of the lead in enamel biopsies and in saliva for measuring exposure to lead is discussed.