Using ApoE Genotyping to Promote Healthy Lifestyles in Finland - Psychological Impacts: Randomized Controlled Trial.

Common health recommendations often incite very little public response, as people instead require individualized information. The purpose of this study was to assess the psychological effects of personal genetic information, provided by different apoE genotypes, as a tool to promote lifestyle changes. This study was a one-year intervention study using healthy adults, aged 20-67 years (n = 107). Their experiences of state anxiety, threat and stage of change were measured three times over a 12 months period. These psychological experiences were assessed, during the genetic information gathering, for three groups: a high-risk group (Ɛ4+, n = 16); a low-risk group (Ɛ4-, n = 35); and a control group (n = 56). The psychological effects of personal genetic risk information were shown to be short-term, although the levels of state anxiety and threat experiences in the high-risk group both remained at a slightly higher level than in the baseline. Threat experiences differed almost significantly (alpha = 0.017) between the Ɛ4+ and Ɛ4- groups (p = 0.034). Information on the apoE genotype impacted the experience of cardiovascular threat; this effect was most intense immediately after genetic feedback was received. However, fears of threat and anxiety may not be an obstacle for using gene information to motivate healthy, stable adults towards making lifestyle changes. Further studies should thus focus on how to utilize genetic screening in prevention of lifestyle-related diseases.

Seven weeks feeding of magnesium and fluoride modifies plasma lipids of hypercholesterolaemic rats in late growth phase.

Recent findings indicated that a low fluoride supplement, especially with a low magnesium supplement in the basically low magnesium diet of genetically hypercholesterolaemic male RICO rats, may prevent the generation of atherosclerotic serum lipid profile. In the present study, several plasma lipids/lipoproteins were measured in the same strain of rats after a later growth phase. The control group C was fed an adequate diet with 45 per cent sucrose plus some cholesterol while the dietary fluoride was very low (1.1 mg F/kg of diet). In diet of group D, the Mg content was reduced to about one seventh of Mg of group C, i.e. to 122 mg/kg. Diet of group E was as that of group D with F content elevated to 17.2 mg/kg. Diet of group G was as that of group E with Mg content elevated to 220 mg/kg. The feeding period was terminated at 12 h deprivation of food and following exsanquination. Total plasma cholesterol in group C was 4.5 mmol/L. The central factor in causing reduction in growth rate and several plasma lipids and their lipoprotein subfractions appeared to be the magnesium deficiency. However, the greatest significant reductions in plasma cholesterol, plasma free cholesterol, plasma and VLDL esterified cholesterol and also HDL cholesterol, HDL esterified cholesterol and plasma triglycerides from those levels of the control group C were found in group G (fluoride and magnesium supplements). Supplementation of fluoride alone in group E reduced only plasma and VLDL esterified cholesterol. In the present male RICO rats, low dietary F and Mg supplements, separately, and especially together, may participate in the regulation of the outcome of atherosclerosis via affecting several plasma lipid risk factors known to associate with the development of atherosclerosis.

Effects of dietary fluoride and magnesium supplements on cyclic adenosine monophosphate (cAMP), calcium and magnesium levels in aorta of genetically hypercholesterolaemic RICO rats.

Previous observations have suggested that low intakes of fluoride prevent pathological calcifications of internal organs, including the aortic wall, in experimental animals, fed a basically low magnesium diet. Our group found recently that fluoride has some potentially preventive effect against atherosclerotic serum lipid profiles in genetically hypercholesterolaemic rats. To study whether the apparently positive potential of fluoride against atherosclerosis is also reflected in aortic tissue, through its well known activation of adenylate cyclase, the aortic cAMP content of the rats used in our recent study was determined. Out of a total of 56 male RICO rats, mean weight 160 g, the control group C was fed an adequate diet, with 44% sucrose, a magnesium content of 883 p.p.m. and with 0.5% cholesterol. Group D had the same diet as group C except that the magnesium content was reduced to 200 p.p.m. Group E had the same diet as group D but with the fluoride content elevated from 1.9 to 12 p.p.m. Group G had the same diet as group E but with the magnesium content elevated from 200 to 300 p.p.m. After a feeding period of 6 weeks, the aortas of the animals were removed, cleaned and kept at -70 degrees C until analysed. The mean cAMP content of the aortas, measured by radioimmunoassay, in groups C, D E and G was 439, 546, 681, and 1394 mumol mg-1 protein, respectively. In group G only, the cAMP content was significantly higher than that of the other groups (p < 0.001). The mean calcium and magnesium contents of the aortas of different groups did not significantly differ from each other. Thus in RICO rats, fed a high-sugar low-magnesium diet with cholesterol, supplementation of the diet with a small amount of fluoride elevates the cAMP content of the aorta, provided that the intake of Mg is not very low.

High strontium addition to chlorhexidine-fluoride gel does not increase its caries-preventive effect in rats.

One hundred Osborne-Mendel rats were weaned at the age of 21 to 22 days, inoculated with Streptococcus mutans in the mouth, and fed a semisynthetic diet for the next 43 days. The control group received no treatment. The study groups received gel applications on their molars with placebo, chlorhexidine-fluoride (CXF), CXF plus 50 ppm Sr, or CXF plus 250 ppm Sr daily for the first 21 days of the experiment Although caries was significantly reduced by CXF and CXF plus 50 ppm Sr treatments, the Sr additive did not significantly improve the caries-preventive effect of CXF. The addition of 250 ppm Sr to the CXF gel seemed markedly to weaken the effect of CXF.

Serum lipoprotein levels in genetically hypercholesterolaemic RICO rats: effects of a high-sucrose-cholesterol diet without or with altered magnesium and fluoride content.

Genetically hypercholesterolaemic RICO rats (male, 6 weeks old) were randomly distributed into 6 experimental groups. The zero-time basal group A was sacrificed at the start of the experiment while the other groups were fed for 6 weeks and then sacrificed. Group B was fed a stock diet. Control group C was fed a high-sucrose (45%) diet with 0.5% added cholesterol. In the diet of group D, only the magnesium (Mg) content was reduced from the level of group C (883 ppm) to 200 ppm. The diet of group E was the same as that of group D with the addition of 12 ppm of fluoride (F) and the diet of group G was the same as that of group E, but with its Mg content elevated from 200 ppm to 300 ppm. Analysis of aortic blood samples, taken before sacrifice, indicated significant increases in total serum cholesterol (p < 0.01), very low density lipoprotein (VLDL) (p < 0.001) and low density lipoprotein (LDL), (p < 0.001) cholesterol, and a trend to lower high density lipoprotein (HDL) cholesterol in group C, as compared to group B. Significantly lower total (p < 0.05), VLDL (p < 0.01) and LDL (p < 0.01) triglycerides were observed in group C when compared to group B. The LDL phospholipids were significantly higher in group C (p < 0.001) than in group B. When cholesterol levels in groups D, E and G were compared with group C, the VLDL cholesterol in group E and the LDL cholesterol in group G were slightly but significantly (p < 0.05) reduced, while total cholesterol and the other subfractions were unaltered. The LDL triglycerides of groups E and G were significantly smaller still than the already small fraction in group C. The VLDL triglyceride in group E was significantly lower than that of group C (35% reduction, p < 0.001), D and G (p < 0.05). Phospholipids were slightly but significantly reduced in the VLDL fraction of group E and in the LDL fraction of group G (p < 0.05 and 0.01, respectively), as compared to those of group C.

Chlorhexidine susceptibilities of mutans streptococcal serotypes and ribotypes.

The susceptibilities of 379 clinical mutans streptococcal isolates to chlorhexidine (CHX) were tested by agar dilution according to the standards of the National Committee for Clinical Laboratory Standards. Isolates were obtained from saliva samples of 34 young mothers who had high or moderate salivary levels of mutans streptococci at baseline. Samples were collected on three occasions, before childbirth, when each child was 6 months old, and 1 year later. Of these isolates, 50% were inhibited at 1 microgram of CHX per ml, 90% were inhibited at 2.0 micrograms/ml, and all were inhibited at 4.0 micrograms/ml. The MICs for Streptococcus mutans isolates (serotypes c, e, and f) were lower than those for Streptococcus sobrinus isolates (serotypes d and g). In some subjects, the MICs for isolates of the same serotype were different. This phenomenon was studied by ribotyping isolates (n = 45) from selected subjects (n = 7). It was found that if there were intraindividual differences in the MICs for isolates of the same serotype, then the ribotypes of these isolates were different. In order to decrease the mutans streptococcal infection risk for children, 24 mothers (test group) brushed their teeth periodically with a gel that contained 0.3% CHX digluconate and 0.2% NaF, pH 5.8, between the second and third sampling occasions. The gel was used twice a day for the first 10 days of each month. Development of resistant strains during CHX-NaF gel use was not detected. The serotype distribution of isolates from the test group after 1 year of periodic CHX-NaF gel use did not differ from that at baseline. Periodic CHX-NaF gel brushing did not lead to lower salivary mutans streptococcal counts.

Fluoride and sugar intake among adults and youth in Mauritius: preliminary results.

The potential use of different vehicles for delivering fluoride to prevent dental caries has been discussed recently in Mauritius. Water fluoridation was found not to be feasible, and extending the fluoride tablet program would not be easy. Thus, sugar fluoridation as one possibility was considered. For these purposes, the average fluoride and sugar intake was estimated in Mauritius. The results are based on two studies--a Survey on Diet, Health and Lifestyle of Youth in Mauritius (1990) and the Mauritius Diet and Health Survey. Information was collected by trained interviewers using food-frequency and 24-hour-recall questionnaires. The daily total sugar intake, manufactured and natural, was found to be 62 g per day in young people and 50 g per day in adults. In the younger groups, daily frequencies of raw sugar, sweets, and biscuit (cookie) consumption were 1.5, 0.2, and 0.2 times a day, respectively. For adults, the mean daily frequency of consuming sugar-containing foods was 2.6 (SD = 1.3). The daily sucrose intake was rather high, representing about 10% of the daily energy intake. The fluoride levels of foods were calculated by use of Finnish and other available fluoride tables. The mean fluoride intakes per day were 0.64, 0.72, and 0.62 mg per day for 8-17-year-, 18-24-year-, and 30-64-year-old groups, respectively. The median fluoride intake for the oldest group was 0.62 mg/day. The estimated fluoride intake from food did not correspond with the proposed level for the prevention of caries (Murray, 1986) except for the 18-24-year-olds, where it might have been just above the lower recommended limit. However, further data based on analysis of the fluoride contents of Mauritian food samples, especially of whole daily diet, are needed.

Efficacy of chlorhexidine solution with fluoride varnishing in preventing enamel softening by Streptococcus mutans in an artificial mouth.

For study of the enamel-protective effect of chlorhexidine-fluoride applications, the labial surfaces of pieces of bovine incisors were treated with 0.2% chlorhexidine gluconate solution, with Duraphat fluoride varnish, or with both of the above agents, while one group was treated with distilled water and one was left as an untreated control. Furthermore, a placebo varnish was used in the chlorhexidine- and distilled-water-treated groups; all the varnishes were removed after 24 h. The enamel slabs were mounted pairwise in an artificial mouth to form approximal contacts. The teeth were continuously rinsed with a common pool of artificial saliva to which was added 3% sucrose, and which was infected on the first day with Streptococcus mutans, "Ingbritt". The saliva was renewed daily and the incubation at 37 degrees C lasted for 10 days. The appreciable softening found in the distilled-water- and placebo-varnish-treated group tended to be prevented by the chlorhexidine and even more by the fluoride treatment, while the chlorhexidine-fluoride treatment prevented enamel softening completely. The saliva, infected only on the first day, and renewed daily, tended to become more acidified toward the end of the experimental period, obviously because the fermenting organisms had infected the surfaces of the model and formed plaque-like coatings on the enamel.

Dental caries and mutans streptococci in relation to plasma ascorbic acid.

Ascorbic acid (AA) affects in vitro growth of bacteria and may also act in vivo to decrease caries activity. The aim of this study was to evaluate the possible association of AA level in plasma with number of caries lesions, relative numbers of some species of oral cariogenic flora, and rate of salivary secretion. The caries status and some bacteriologic variables of dentulous adult subjects with a low level of AA in the plasma (< or = 25 mumol/l; n = 75) were compared with those of controls (plasma level > or = 50 mumol/l; n = 75) matched for age, sex, and number of teeth. For each subject, site-specific recordings of the presence or absence of plaque, dental caries, fillings, and erosions were recorded clinically by the same dentist in a double-blind system. The amounts of visible plaque and numbers of decayed tooth surfaces were significantly higher in the low AA group than in the controls. No between-group differences were found in the number of fillings and the amount of oral bacterial growth. The frequencies of consumption of vegetables, berries, and other fruit were significantly lower in the low AA group than in the controls.

Enamel dissolution in relation to fluoride concentrations in the fluid of dental plaque-like layers of precultured Streptococcus sobrinus.

Two experiments were conducted to find out what concentration of fluoride (F), when added as NaF to the fluid of an in vitro caries model, would be sufficient for full protection of the underlying enamel during a long (20 or 40 h) fall in 'plaque' pH. An existing caries model with bovine enamel and Streptococcus sobrinus 'plaque' was employed, while the fluid phase was initially either fully or partially saturated with tricalcium phosphate. In the model with fully saturated and more strongly buffered fluid, a 10 parts/10(6) addition of F to the fluid phase caused no inhibition of the pH fall. In the model with partially saturated and weakly buffered fluid, prevention of the pH fall increased along with increase of added F from 2 to 20 parts/10(6). In each model, the 10 parts/10(6) addition of F was associated with complete prevention of the increase of calcium (Ca) in the fluid phase. In the partially saturated, weakly buffered model, findings on the inorganic P of the fluid phase agreed with findings on Ca. The findings for microhardness of the enamel surface indicated a complete prevention of the enamel softening through the 10 parts/10(6) F additive. Enamel F content was elevated by the fermentation, and even more so when F was added with sugar to the fluid phase. The Ca content of Strep. sobrinus cells was reduced when incubated with sucrose for 40 h and, especially, with sucrose and F.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of different strontium concentrations on the efficacy of chlorhexidine-fluoride-strontium gel in preventing enamel softening in vitro.

The effects were compared of strontium concentrations of 0, 15, 50 and 250 parts/10(6) in chlorhexidine(0.20%)-fluoride(0.16%) gel in preventing the softening of bovine enamel during bacterial fermentation. Fresh Streptococcus sobrinus cells were suspended in a buffer solution (pH 6.0) with 3.3% sucrose and centrifuged as a plaque-like layer on the top of enamel slabs covered with 10 microliters gel. AFter 24 h incubation, the pH fall of the fluid was significantly smaller in all test groups than in the placebo group. Strontium seemed to have an inhibitory effect on the pH fall. All test gels significantly prevented softening and dissolution of enamel during bacterial fermentation, which was directly related to strontium concentration. The amounts of calcium and phosphorus in the cells and fluid after incubation were the smallest in the group with 250 parts/10(6) strontium. In a second experiment without bacteria, new enamel slabs were covered with 10 microliters gel containing chlorhexidine and NaF with 0 and 250 parts/10(6) strontium to study the protective effect of strontium. After 24 h gel treatment, each enamel slab was dissolved in 1 ml 0.1 M lactic acid, pH 5.0, for 2 h. Significantly less calcium and phosphorus were dissolved from the enamel in both test groups than in the control and placebo groups. However, the placebo gel also prevented calcium and phosphorus dissolution significantly. These results suggest that the addition of strontium to chlorhexidine-fluoride gel improves the ability of this combination to prevent caries-like enamel softening. The inhibition of bacterial acid production by the strontium-containing gel may explain this enhanced protection of enamel.

Effect of different glass ionomers on the acid production and electrolyte metabolism of Streptococcus mutans Ingbritt.

In order to study the effects of different glass ionomers on the metabolism of Streptococcus mutans, test slabs of freshly mixed conventional glass ionomer (Fuji), silver glass ionomer (Ketac-Silver), composite (Silux), and 2-week-old Fuji were fitted into the bottom of a test tube. A plaque-like layer of S. mutans strain Ingbritt was centrifuged onto the test slabs, and the samples were incubated for 20 h in 1.7% (w/v) sucrose solution. For freshly mixed Fuji and Ketac-Silver, the pH fall was significantly smaller than for old Fuji and composite. These materials also released the largest amount of fluoride into the fluid phase. Incubation with glass ionomer materials led to an increase in the cellular concentration of fluoride in bacteria, but intracellular fluoride did not correlate with the fall in pH. The lowest pH was associated with the lowest cellular magnesium content. Ketac-Silver released large amounts of calcium in the fluid phase, and the cellular calcium content was doubled in this group. The results show that freshly mixed glass ionomers affect acid production and electrolyte metabolism of S. mutans in vitro. The effect of conventional glass ionomer, however, seems to disappear after a few weeks. The effects of calcium and silver released by cermet glass ionomer deserve further study.

Chlorhexidine solutions, gels and varnishes in caries prevention.

To combat dental caries, a chemical has been sought that possesses stronger antimicrobial properties than fluoride in support of its physicochemical tooth-protecting properties. These searches have led to several agents, of which chlorhexidine (CH) appears most effective. To reduce local side effects of the well-known 0.2% CH mouthwash, a 0.05% CH gluconate + 0.04% NaF solution, pH 5.9, has been developed. Use of this combination over a 2-year period resulted in a 53% reduction in caries increment and a 75% reduction in gingival bleeding, i.e. a clear duality of prevention of oral disease (Luoma et al. 1978). Staining of teeth was minimal and easily removable in about one third of the subjects. To lessen the contribution of patients, chlorhexidine gels, without but more especially with fluoride have been professionally administered. Reductions in salivary mutans streptococci after short periods of gel applications have been found to persist longer than reductions after brief periods of mouthwashing. Reductions of approximal caries increment by about 50% in children, and root surface caries in adults have been obtained through use of CH gels. The effect on root surface caries in adults was equal to that obtained through use of local fluoride applications. Dental CH varnish seems promising, especially because a very short contact time with a tooth may be sufficient to reduce mutans streptococci. No simultaneous effects against caries and gingivitis of CH gels or varnishes has been reported. Comparisons of CH solutions, gels and varnishes, with or without fluoride, in relation to their potentials for preventing oral disease in subjects at risk remain to be accomplished.

Effects of a chlorhexidine-fluoride-strontium rinsing program on caries, gingivitis and some salivary bacteria among Finnish schoolchildren.

In order to find out if it is possible to prevent caries and gingivitis by periodical use of chlorhexidine-fluoride mouthrinses with or without strontium, and to find out what effects they have on salivary mutans streptococci and lactobacilli counts, a total of 243 schoolchildren aged 11 yr with high DMFS scores were randomly divided into four groups. One group (C) served as a basic control. Subjects in the second group (CXF) rinsed their mouths twice a day every third week with a rinsing solution containing 0.05% chlorhexidine gluconate and 0.04% NaF. In the third group (CXFS) the rinsing solution contained 500 ppm Sr during the first and second year and 15 ppm during the last 6 months, in addition to chlorhexidine and fluoride. In the fourth group (CX) the solution contained only 0.05% chlorhexidine gluconate. All the rinsing solutions had pH 5.8 buffered with succinic acid-NaOH buffer. After 2 yr and 9 months, the mean DMFS (SD) increments in the C, CXF, CXFS, and CX groups were 3.8 (5.7), 2.5 (3.2), 3.5 (4.8), and 3.4 (5.5), respectively. The percentage of subjects with bleeding gingival units had decreased from initial to final values as follows: C, 81-38; CXF, 88-42; CXFS, 89-56; CX, 89-37. The number of lactobacilli and mutans streptococci in saliva remained virtually unchanged throughout the study. For caries increment and gingival bleeding, the differences between groups were not statistically significant. The chlorhexidine-fluoride combination tended to prevent caries, but the effect on gingival bleeding and salivary counts of mutans streptococci and lactobacilli was negligible.

Experience and views of caries research and oral health.

The main clinical and theoretical studies on caries etiology and prevention and on general health published by the author and his coworkers since the beginning of the 1960s are briefly reviewed. Among the caries prevention methods published by previous authors, the Finnish trials on fissure sealing and fluoride varnishing showed distinct preventive effects. On the basis of these and later supporting findings, these methods were rapidly and widely adopted in the dental health care of Finnish children and adolescents. A chlorhexidine-fluoride mouthrinsing solution, developed by the author, exhibited simultaneous reduction of both caries and gingivitis among high -risk children and this preparation or chlorhexidine-fluoride gels have been widely prescribed for risk subjects, especially those with a caries risk. Despite the good caries prevention results obtained through fluoridation of sugar products and in respective model studies, this procedure has not been passed for commercial use in Finland. The translocation of phosphorus, potassium and fluoride between microbes of dental plaque origin and their environment, including the respective elements of enamel origin, were presented as a partial explanation for the role of phosphates and fluoride in caries etiology and/or prevention. Animal experiments elucidated the killing mechanism of a high single fluoride intake and its prevention by magnesium with explanatory changes in cardiac calcium. On the other hand, experiments on prolonged intakes of low dietary fluoride by rats confirmed earlier findings on the potential of fluoride in preventing calcium salt imbalances in internal organs. This was accomplished with a fluoride intake sufficient for caries reduction. The ability of two strains of the mutans streptococci and a Lactobacillus to invade enamel and dentine and to destory these structures from the inside before the cavitation phase of caries was demonstrated with gnotobiotic rats. The marked caries reduction among Finnish children and adolescents within the past 20 years appears to be due to a number of factors.

Fluoride and mutans streptococci in plaque grown on glass ionomer and composite.

The aim of this study was to compare the levels of fluoride and mutans streptococci in plaque grown on glass ionomer (Ketac-Fil) and composite (Silar) restorations in vivo. From tunnels left under the brackets bonded either with glass ionomer or composite, 14-day-old plaque samples were collected 14, 28, and 42 days after bonding. For glass ionomer the mean counts of mutans streptococci in plaque were 0.5 x 10(3), 6.7 x 10(3), and 8.8 x 10(3) CFU at the first, second, and third collection, respectively, whereas for composite restorations the corresponding values were 32.1 x 10(3), 14.6 x 10(3), and 120.6 x 10(3) CFU. For glass ionomer the mean concentrations of fluoride were 19,985, 5,788, and 5,019 ppm at first, second, and third collections of 14-day-old plaque samples, respectively, whereas for composite restorations the mean concentrations of fluoride were about 200 ppm throughout the study. The results show that the fluoride level in plaque growing on glass ionomer is much higher than that on composite restorations which seems to affect the level of mutans streptococci in dental plaque.

A new method for studying the effect of glass ionomer on plaque in vivo.

In order to study the amount of fluoride originating from glass ionomer, a test appliance was constructed and set on upper molars of sixteen volunteers using glass ionomer. The control appliance was set on the contralateral tooth using composite. Six weeks after the setting of appliances, plaque samples were taken and analysed. Mean amounts of protein corresponding to the amounts of plaque were equal in the test and the control groups. The mean fluoride/protein ratio in plaque was 80 times higher in the glass ionomer group than in the composite group. With this sampling method it is possible to collect sufficient amounts of plaque for quantification of plaque fluoride.

The LD50, excretion and serum and bone levels of F after a high single F and F + Mg dose in rats with findings on cardiac Ca and Mg.

The LD50 for fluoride was elevated from less than 60 mg F/kg body weight to 172 mg F/kg when magnesium (as MgCl2), equivalent to 3 times that of F, was administered by gavage 30 min after the F dose. A dose of 30 mg F/kg elevated the mean steady state of F in serum nearly 1.5-fold and in femoral bone nearly 2-fold when administered with or without the subsequent Mg dose and observed 24 h after the electrolyte dosages. Also, in 24-hour urine the mean F excretion was highest in the F and FMg groups. The total F excretion (fecal + urinary) was elevated 8- and 10-fold when fluoride was administered with or without magnesium, as compared to control levels. Magnesium administration with fluoride did not significantly modify the above mean values of the group given fluoride alone. This suggests that interference with the absorption of fluoride was not the primary protective function of magnesium against the acute toxicity of fluoride. Additional experiments, conducted to further clarify the toxic mechanism of fluoride and the protective mechanism of magnesium, resulted in the following findings: An intraperitoneal dose of 20 mg F/kg elevated fluoride concentration in serum in 1 h about 20 times compared to the controls. Magnesium injected simultaneously with fluoride did not modify the effect of fluoride alone. No significant changes were found in the concentrations of K, Mg, Na or Ca of the lung, skeletal muscle, kidney or liver after these injections except for some trend of elevation of Ca in the heart. However, after a dose of 30 mg F/kg i.p., the heart Ca/Mg mole ratio was elevated within 1 h from 0.037 to 0.194, while all of these rats died within 1 h after the injections. When magnesium, equivalent to 3 times the amount of fluoride was injected, this mole ratio was only 0.095, and all rats in this group survived over 1 h. These results suggest that the lethality of fluoride may be dominantly mediated by the elevated Ca (Ca/Mg ratio) in the heart muscle and that this is correctable by Mg.

Protection by F, I, Sr, and combinations against fermentation attack by Streptococcus sobrinus artificial plaque on bovine enamel.

Labial surfaces of 64 bovine incisors (8 teeth/treatment) were subjected to 1-min treatment with (1) 500 ppm Sr, (2) 0.5% I2 plus 1% KI solution, (3) F varnish treatment (Duraphat) for 24 h, or (4) combined treatments. The treated teeth were incubated under an artificial Streptococcus sobrinus plaque for 10 days. The 'oral fluid' with maleate buffer (pH 5.8) partially saturated with Ca3(PO4)2 and with or without 3.3% sucrose or sucrose plus 25 ppm F, was replaced by a mixture containing thioglycolate broth and the buffer for 4 h daily. This was done in an attempt to maintain the viability of the plaque as it was not renewed. Analysis of the Ca and inorganic P in the fluid phase taken after the 1st and the 10th day of incubation indicated that complete protection was obtained with F varnishing plus 25 ppm F in the fluid, with added sucrose. The Sr plus F treatment was more protective than F or Sr alone. The iodine treatment was slightly protective when combined with F varnishing. The results of the enamel surface and subsurface F and Sr as well as measurements of surface microhardness also indicated the highest protective effect with the double-F treatment and a marked protection provided by the Sr plus F treatment. The efficacy of the double-F treatment was partly explained by the prevention of a fall in 'plaque' pH and partly by the release of bacterial inorganic P in the extracellular fluid. The present caries model is versatile in quantification of changes in numerous parameters (14 parameters measured) involved in the caries-like process and its inhibition.