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Sorbitol-fermenting strains of Streptococcus sanguis and Streptococcus mitior were grown both anaerobically and in the presence of oxygen in a sorbitol-containing complex medium. Washed-cell suspensions were incubated with an excess of sorbitol, and the production of lactate, formate, ethanol, and acetate was analyzed. Moreover, we determined the lactate dehydrogenase and pyruvate formate-lyase activities in cell-free extracts of anaerobically grown cells. The anaerobically grown cells produced lactate, formate, ethanol, and acetate under anaerobic conditions. When these cells were exposed to air, the amounts of formate, ethanol, and acetate were reduced in comparison with those of the strictly anaerobic cells. Cells grown in the presence of oxygen only produced detectable levels of lactate and acetate. Anaerobically grown cells possessed lactate dehydrogenase and pyruvate formate-lyase activities under strictly anaerobic conditions. The level of pyruvate formate-lyase was dramatically reduced when cells were exposed to air, while the level of lactate dehydrogenase was about the same as that under strictly anaerobic conditions. Thus, the results indicate that S. sanguis and S. mitior both metabolize sorbitol differently under anaerobic and aerobic conditions. This difference may depend on the oxygen-sensitivity of the pyruvate formatelyase of these micro-organisms.

A strict vegetarian diet [vegan diet (VD)] was investigated. Six middle-aged vegans (three men and three women) collected copies of 24-h diets using the duplicate portion sampling technique. By chemical analyses, the nutrient composition was determined in detail and compared with corresponding figures of a normal mixed Swedish diet. In the VD 30% of the energy originated from fat compared with 40% in normal Swedish mixed diet (MD). Linoleic acid was the dominant fatty acid (60% of total fat in VD versus 8% in MD). The VD contained 24 g protein/1000 kcal compared to 30 g/1000 kcal in MD, but the intake of essential amino acids by the vegans exceeded the recommendations. Dietary fiber was about 5 times higher in the vegan diet (29 versus 6 g/1000 kcal) and sucrose similar to MD (18 versus 21 g/1000 kcal). Among the inorganic nutrients the concentration of calcium (351 versus 391 mg/1000 kcal) and sodium (53 versus 49 mmol/1000 kcal) were similar in both types of diets but the amount of potassium (56 versus 30 mmol/1000 kcal, magnesium (300 versus 110 mg/1000 kcal), iron (9 versus 6.5 mg/1000 kcal), zinc (6.5 versus 4.7 mg/1000 kcal), and copper (2 versus 0.7 mg/1000 kcal) were nearly doubled. Iodine (39 versus 156 micrograms/1000 kcal and selenium (5 versus 17 micrograms/1000 kcal) were much lower in the VD, selenium even being undetectable in several 24-h diets. The VD was rich in folic acid (301 versus 90 micrograms/1000 kcal in MD) but the intake of vitamin B12 was only 0.3 to 0.4 microgram/day (MD: 3 to 4 micrograms/day). No clinical signs of nutritional deficiency were observed in the vegans. Serum protein levels of the vegans as well as their serum lipoproteins were near the lower range of the reference group. In addition, none of the vegans was overweight and their blood pressures were low for their age.

The aim of the investigation was to evaluate the effect of chlorhexidine gel treatment on caries development of approximal tooth surfaces and on salivary counts of Streptococcus mutans. 220 12-year-old schoolchildren, divided into three groups, participated: (1) chlorhexidine gel group (n = 72), (2) placebo gel group (n = 77), and (3) control group (n = 71). The study was carried out double blind with respect to the two gel groups. Group 1 was treated 4 times/year with 1% chlorhexidine gel and group 2 with a placebo gel. Approximately 1 ml of gel was applied interdentally by means of a flat dental floss. The control group did not receive any gel treatment or flossing. Number of S. mutans in the saliva was estimated on five occasions during the study with the spatula method. After 3 years, the mean approximal caries increment, expressed as new DFS, was 2.50 in the chlorhexidine gel group and 4.30 in the placebo gel group (p less than 0.05). The corresponding figure in the control group was 5.25 (p less than 0.001 when compared to group 1). 44% of the children in the chlorhexidine gel group and 32% in the placebo gel group did not develop any new approximal caries lesion during the 3-year observation period compared to 18% in the control group (group 1-3 p less than 0.001; group 2-3 p less than 0.05). The number of new approximal fillings (FS) was 0.24 in the chlorhexidine gel group, 0.75 in the placebo gel group and 0.82 in the control group (group 1-3 p less than 0.01; group 2-3 p less than 0.05). There was no statistically significant difference between the groups with respect to numbers of S. mutans in saliva. However, there were more individuals with low numbers of S. mutans in the chlorhexidine gel group at the final examination compared to the baseline level (p less than 0.05).

A longitudinal study on the effect of an individualized preventive program was carried out on 10-11 year old children with higher caries and/or gingivitis prevalence than the average. The program was based on bimonthly professional toothcleaning as well as hygiene and dietary instructions. After an introductory period of 3 months the frequency of visits was individualized according to the gingival condition of the children (every 2nd to 4th week). For one group this program was supplemented by instruction in dental flossing for proximal tooth cleaning on a daily basis. The effects of the preventive measures were evaluated after an experimental 2 year period. Two years after withdrawal of the preventive measures, the longitudinal effects were recorded. In all 627 children were examined and of these 87 children were selected for the study on gingival and cariological indications. It was possible to follow 74 children throughout the 4 year period. After 2 years the number of new caries lesions was significantly reduced in the test groups as compared to the controls. The caries increment in the test group was 1.7 new surfaces per individual and in the control 4.5. The corresponding figures at the follow-up examination was 8.5 and 5.9 respectively. Thus any prolonged effect of the preventive program could not be confirmed. An improved cariological status was also recorded among the children selected on gingival indications. The increment was 0.8 in the test and 3.8 in the control group during the experimental period. The corresponding figures at the supervisory control was 1.8 and 4.6 new surfaces respectively indicating a prolonged effect among these children. The interpretation of the results from the "flossing" group was not clear-cut, since the flossing was performed unsupervised. However, no new decayed tooth surfaces were recorded in those children who had claimed that they had used floss at least every second day. The gingival situation improved in all test groups and was visible even in the follow-up study.

The pH-decrease in dental plaque in vivo after mouth rinses with solutions of sucrose and maltose has been compared. No statistically significant differences were found between the results obtained with these two disaccharides. Pooled samples of parotid saliva, centrifuged whole saliva and dental plaque supernatants were separated with the isoelectric focusing technique. The results suggest that maltose is hydrolysed in parotid saliva by the salivary alpha-amylase and in dental plaque by enzymes from sources other than the salivary glands, probably microorganisms. No bacterial alpha-amylases, separated from salivary alpha-amylase, were found in whole saliva specimens or in dental plaque supernatants. Quantitative determinations of "maltase" and amylase activities in parotid saliva, centrifuged whole saliva and dental plaque supernatants from 10 subjects were carried out. The highest enzyme activity of "maltase" was found in the samples of dental plaque and the highest amylase activity in parotid saliva specimens.

Caries development on exposed root surfaces was evaluated in 31 patients who had been subjected to surgical and/or nonsurgical periodontal treatment 8 years earlier due to advanced chronic periodontitis. Besides assessments for evaluation of the periodontal treatment, a number of examinations and tests were carried out in order to assess variables presumed to influence the root surface caries development. Both statistical and graphical analyses were carried out to test differences between groups of subjects and to evaluate the variables studied as possible risk factors for root surface caries. The variables studied were: salivary lactobacillus count, salivary Streptococcus mutans count, plaque score, salivary secretion rate, salivary buffer effect, oral sugar clearance time, dietary habits and the age of the subject. The final results support previous findings from an initial 4-year period that root surface caries occurs, though to a minor extent, in this patient category demonstrating good or excellent periodontal conditions after periodontal treatment. A positive correlation was found between the baseline and final root surface caries scores. After the second 4-year period, the salivary counts of S. mutans and lactobacilli, the plaque score and the dietary habits differed significantly between groups of subjects who had developed 0 or greater than 5 new DFS %. Root surface caries was far more prevalent when risk values of the variables studied were present than when they were absent. The important variables in this respect differed considerably between the subjects. No single variable was found to be discriminative in all subjects.

As part of a series of postgraduate courses in Cariology for dentists, a section designed to stimulate the interest in quality evaluation of fillings was included. Thus, 75 private practitioners were asked to evaluate a number of anterior restorations on their own patients. The method used was a modification of the California Dental Association (CDA) quality evaluation system. By use of a four-graded scale the following five properties were evaluated: (1) color of the filling, (2) color of the margin, (3) surface structure and anatomic form, (4) marginal integrity, and (5) caries. The criteria were related to practical-clinical measurements. Altogether 1147 fillings were assessed, most of them 2-4 years old (n = 949). The results showed that 25 different brands had been used, of which 4 composites constituted 68% of all fillings. With the exception for one composite material, no obvious difference in the quality evaluation between the materials was observed. Of the 2-4 year old fillings, approximately every fourth was rated as "not acceptable", i.e. with need for clinical treatment "soon" or "within reasonable time". Our impression was that the system used in this study is suitable for an assessment of the quality of anterior fillings in a private practice and that it should stimulate dentists to a quality thinking in dentistry in general.

The capacity of the oral bacteria Streptococcus mitior, S. mutans and S. sanguis to methylate mercury was investigated in vitro. Mercuric chloride and pulverized dental amalgam in distilled water, respectively, were used as sources of mercury. Methylmercury was found in the bacterial cells of all three tested strains. The results indicate that organic mercury compounds may be formed in the oral cavity.

The main purpose was to study various factors with respect to predicting dental caries. From a population of 442 employees at a shipyard, 68 patients with an average age of 56 yr were selected for the present investigation. They were examined once a year during a 2-yr period with respect to: 1) number of new caries lesions, and 2) a series of caries related factors, i.e., DMFS, oral hygiene status, dietary habits, numbers of Streptococcus mutans and lactobacilli in saliva, and secretion rate and buffer effect of saliva. The median values of all studied variables as found at the baseline examination were more favorable in the caries inactive (n = 30) than in the caries active group (n = 38), but only DMFS (P less than 0.001), dietary score (P less than 0.05), and number of S. mutans in saliva (P less than 0.05) differed significantly between the two groups. Number of S. mutans showed the highest sensitivity value, followed by dietary score. The main conclusion from this study is, however, that in spite of a relationship between caries activity and unfavorable values, especially for DMFS, dietary score, and number of S. mutans in saliva, it would have been difficult to predict the caries active patients on an individual level.

Six middle-aged lactovegetarians (three men and three women) collected copies of four 24-h diets using the duplicate portion sampling technique. By chemical analyses, the nutrient composition of the lactovegetarian diet was determined in detail and compared with that of a mixed Swedish diet (normal) and a vegan diet (vegan) studied previously. The nutrient composition of the lactovegetarian diet expressed per 1000 kcal represented an average between normal and vegan diets. It was in closer agreement with Swedish recommended dietary allowances than the normal Swedish diet. Thus, the lactovegetarian diet contained 35% of the energy as fat and was rich in polyunsaturated fatty acids, especially linoleic acid, which resulted in a polyunsaturated/saturated fat ratio of 0.6. The lactovegetarian diet had a cholesterol concentration only half of that of a normal diet. Protein content and amino acid composition were well above recommendations. The lactovegetarian diets contained less sucrose than normal and vegan diets, but the sum of the intake of low molecular weight carbohydrates was comparable to normal and vegan diets. Dietary fiber was three times higher than in a normal diet. Essential minerals and trace elements, ie, Ca, Mg, Na, K, Fe, Zn, Cu, Se, satisfied current requirements. The intake of vitamin B12 by the lactovegetarians was around 1.4 micrograms daily, which is below the recommendations. The intake of folates was high, 300 to 400 micrograms daily. The clinical and biochemical investigation of the subjects revealed no signs of nutritional deficiency. Their plasma lipoproteins and the blood pressures were low for their age, in agreement with observations made earlier in a group of vegans.

Several caloric sugar substitutes are available today, e.g. maltitol, Lycasin, sorbitol, xylitol, palatinit, sorbose, coupling sugar, palatinose, fructose and invert sugar. When evaluating the cariogenicity of these sugar substitutes from a bacteriological point of view, different analytical procedures should be considered. In vitro studies on the capacity of pure oral bacterial strains and dental plaque material to decompose the substitute to acid. Studies on the catabolism of the substitute. Possible adaptation of the oral microflora to metabolize the substitute in vivo as well as in vitro. Studies on any inhibitory effect of the substitute on the microbial activities in dental plaque and on the oral microflora. The capacity of oral bacteria, e.g. Streptococcus mutans, to induce caries in animal experiments should also be considered. Results from such microbiological studies make it possible to classify the caloric sugar substitutes into different groups. The first, most suitable, group seems to consist of xylitol and sorbose. These substitutes are fermented by few oral bacteria and no negative adaptation of the oral flora has been observed. A reducing effect upon dental plaque formation and on acid production from glucose has been reported. A second group consists of maltitol, palatinite, palatinose, sorbitol and Lycasin. These substitutes are fermented by certain groups of organisms within the oral genera Actinomyces, Lactobacillus and Streptococcus. Adaptation of oral bacteria to palatinose and to sorbitol, resulting in a more pronounced acid production, has been observed. No inhibitory effects have been reported. The results from experimental studies suggest that these sugar substitutes have no or little cariogenic action in rodents inoculated with S. mutans.(ABSTRACT TRUNCATED AT 250 WORDS)

The aim of the study was to assess the relationship between the consumption of sweets in the preceding three years and the occurrence of proximal caries in the posterior regions of 15-year-old schoolchildren. Information on proximal restorations, excluding the mesial surface of the 1st molar, was obtained from records of about 1,700 children. Thirty children with 0-2 restorations and another 30 with 6-8 were randomly selected, together with the 22 children who had 12-14 restorations. Later, recent bitewing radiographs were used to register the total number of DF surfaces in the relevant regions. The children were interviewed about average consumption of sweets: amount, money spent and frequency. The subjects were cross-tabulated according to the variables amount and frequency. The dependence of cost on each of these variables was found to be statistically significant. Combinations were constructed to give three consumption classes. The mean values of DF surfaces for the three classes appeared in a logical order but, owing to a wide dispersion around the means, the correlation between individual DF surfaces and consumption of sweets was statistically not significant. It was concluded that nowadays the consumption of sweets does not seem to be as strong a factor for the occurrence of caries as it used to be.

In a double blind cross-over study, 20 subjects were given either a sugar free chewing gum containing 0.25 mg fluoride or the same chewing gum without fluoride, eight times a day for 7 days. The pH of 3-day-old plaque was determined before and after each experimental period following a 30-s mouth-rinse with 10 ml 15% sucrose. The pH-decrease was significantly less pronounced after using the fluoride gum than after the placebo gum (P less than 0.001). In a second study, 20 subjects participated in a similar study. In this experiment the acid production activity from sucrose in dental plaque in vitro was determined with the aid of a titration method. In addition, the dental plaque wet weight and the total number of cultivable organisms, Streptococcus mutans and lactobacilli, expressed as the number of colonies per mg plaque, were determined. No significant effect was found on any of these parameters after using the fluoride gum compared to the placebo gum. Thus, the results indicate that slightly elevated levels of fluoride in saliva during daytime, achieved by repeated intake of fluoride gums for 7 days, are sufficient to influence the acidogenicity of dental plaque in vivo.

The aim was to study the effect of different salivary secretion rates on glucose clearance in saliva and on pH changes in dental plaque in man. Eighteen dental students, 21-33 yr old, participated. Dry mouth was induced by injecting methylscopolamine-nitrate submucosally in the labial sulcus. When dry mouth was established, two variables were measured at 1 h intervals, while the salivary flow was recovering: (1) secretion rate of resting and paraffin wax-stimulated whole saliva, and (2) glucose clearance in saliva after ingestion of a glucose tablet. pH changes in dental plaque were studied in 9 of the 18 subjects after a mouth rinse with 10% glucose at two separate occasions, once before and once after an injection of methylscopolamine-nitrate. Higher glucose concentration levels in saliva were found at low than at normal salivary secretion rate. After logarithmic transformation of the salivary glucose concentration values, a biphasic elimination pattern could be seen, with a steeper initial phase followed by a slower one. A critical value for the secretion rate with respect to the salivary glucose clearance time was found to be 0.14 ml/min for resting and 0.62 ml/min for stimulated whole saliva (mean values). The pH changes in dental plaque after the mouth rinse with glucose at extremely low secretion rate were significantly more pronounced than at normal flow rate. Thus, salivary secretion rate affects both the glucose clearance in saliva and the pH changes in dental plaque in man.

The purpose of this study was to elaborate a model for estimating the caries-reducing effect of a preventive measure with due consideration of background factors. The material comprised 50 children, who had consumed NaF tablets regularly during preschool age, and 76 comparable children who had never consumed NaF tablets. They were all examined at 12 and 13 yr of age. Information on caries and, as confounding factors, dietary habits, oral hygiene and microbiologic variables, was obtained on both occasions. Correlations between the parameters and caries, their discriminating effects and interaction between them were studied. The results showed that correction for confounding diminished the crude caries-reducing effect of NaF tablets. Streptococcus mutans and lactobacilli turned out to be the strongest confounders to discriminate well as single variables and to behave logically in analyses of interaction. Therefore, these factors are recommended in the first place for inclusion in a correction model. If the material is sufficiently large for a further breakdown, oral hygiene (represented by bleeding on probing) could be added. The model will be used in future studies of the preeruptive effect of NaF tablets on caries in permanent teeth in the same population.

Sorbitol is a commonly used sweetener in many so called sugar-free products, like chewing-gums, lozenges and medicines. It is also used as a stabilizer in tooth pastes and is found naturally in some fruits and berries. Many methods have been used to evaluate the cariogenicity of sorbitol, e.g. short and long term studies in man, animal experiments and pH-measurements in dental plaque in vivo and in vitro. Most of these studies indicate that sorbitol has a low or no cariogenicity. However, there are some data showing that frequent consumption of sorbitol may result in an increased acid production in dental plaque and in an increased number of sorbitol-fermenting microorganisms. This adaptation is probably of no or only minor clinical importance, at least for persons with a normal salivary function and for people with a moderate consumption of sorbitol-containing products. Thus, present knowledge shows that sorbitol might be considered as a "low cariogenic" sugar substitute.

Forty-two adults, visiting a Swedish health home, participated in the investigation, which included a 6-day period of fasting, followed by a 6-day period with a lactovegetarian diet. The results obtained indicated only a minor and mostly not significant influence on secretion rate, buffer effect, concentration of various electrolytes, and number of lactobacilli and S. mutans of whole saliva.

The aims of the present investigation were, first, to follow the secretion of free glucose in parotid saliva in various subjects after a single oral intake of different carbohydrates, and second, to compare the salivary glucose concentration with the concentration in blood. Twenty healthy subjects, three women and 17 men, 20-35 yr of age, participated. They were asked not to eat or drink anything from 10 p.m. the night before the examination. 75 g of carbohydrate (glucose, fructose, or sucrose) dissolved in 300 ml water was ingested the next morning at 8 a.m. One experimental series with glucose was performed in triplicate in 10 of the subjects. Approximately 1.5 ml of citric acid-stimulated parotid saliva was collected before (0 min) and 15, 30, 45, 60, and 120 min after the intake. Salivary concentration of glucose was analyzed enzymatically. Most of the 0-min samples showed a variation in glucose concentration from 5 to 25 mumol/l. After the glucose, fructose, and sucrose intakes, the salivary glucose level increased about 2-4 times, especially in the 30-min samples. A large inter- as well as intra-individual variation was found both in the 0-min samples and in the samples collected after the different intakes. The correlation between the glucose concentration in saliva and blood was higher after than before the carbohydrate intakes.

The aim of this investigation was to compare dietary habits, plaque and gingival scores, and the dental caries prevalence of 16-yr-olds in 1979 with those of individuals of the same age 5 yr later, i.e. in 1984. Students from two high schools in Kristianstad, Sweden, participated, 273 in 1979 and 228 in 1984. The same two dentists treated the children in 1979 and 1984. The students were asked to fill in a questionnaire concerning breakfast, school-lunch and between-meal habits. Information about the number of decayed (D) and filled (F) approximal tooth surfaces (Sa), DFSa, dental plaque and gingival bleeding scores was obtained from records at the Public Dental Clinics. The prevalence of caries lesions was also determined on 116 and 110 randomly selected pairs of bitewing radiographs from the participants in 1979 and 1984, respectively. The mean DSa was 0.9 in 1979 and 0.3 in 1984. The corresponding values for FSa were 3.6 and 1.5, respectively. In 1979, the DFSa was zero in 28% of the children, compared to 54% in 1984. All these differences were statistically significant (P less than 0.05). When analyzing the distribution of enamel and dentin caries lesions diagnosed on radiographs, the same tendency was found, i.e. that dental health had improved from 1979 to 1984. The dietary habits, however, were on the whole the same on both occasions, as judged from the answers given in the questionnaire. The distribution of plaque and gingival scores did not change during the 5-yr period.(ABSTRACT TRUNCATED AT 250 WORDS)

The bioavailability of cereal fructans (fructooligosaccharides) was investigated both in vitro and in vivo. In vitro studies indicated very slow hydrolysis by human gastric juice and by homogenate of the intestinal mucosa (rat). After intubation of fructans into the stomachs of rats, the recovery of fructans in the small intestine and colon was approximately the same as that of an unabsorbed marker (polyethylene glycol), indicating no or very low disappearance of fructans in the small intestine. In vivo studies of the small intestine in rats showed that the rate of disappearance of fructans was lower than that of mannose, which is known to be absorbed through passive diffusion. In addition the cariogenic effect of cereal fructans was compared to that of glucose. Acid formation from low molecular-weight fructans was found in human dental plaque in vitro. A mouth rinse with unfractionated fructans, containing some quantities of sucrose, fructose and glucose, resulted in relatively low pH values in human plaque in vivo, even if the decrease in pH was somewhat less pronounced when compared with a mouth rinse with glucose.

Similar alpha-(1-->6) linkage-rich, soluble, extracellular glucans have been isolated from six strains of two genetically distinct groups of Streptococcus sanguis and three strains of Streptococcus mitior.

The efficacy of autoclaving high-speed dental handpieces was tested in two types of downward displacement steam sterilizers (instrument autoclaves), commonly used in the dentist's office. Eight series of experiments were performed with various sterilization schedules. Lubrication oils with or without antimicrobial agent were used in four of the series. Each handpiece was inoculated with 1 ml of a suspension containing equal amounts of saliva and spores of Bacillus stearothermophilus (approx. 10(6) spores/ml). Neither sterilization at 120-124 degrees C for 20 min nor at 134-136 degrees C for 10 min resulted in complete inactivation of the spores in series in which the instruments were tested without oil or with oil containing no antimicrobial agent. However, when the handpieces were lubricated with oil containing isopropanol and formaldehyde and the schedule 134-136 degrees C/10 min was used, no growth was observed. The results indicate that instrument autoclaves with built-in programs of 120-124 degrees C/20 min and 134-136 degrees C/10 min could have insufficient capacity to sterilize lubricated or unlubricated dental handpieces. The use of oils containing an antimicrobial agent can overcome this problem.

Lozenges containing hydrogenated starch hydrolysate (Lycasin), maltitol, sorbitol or xylitol were consumed 4 times daily during 3 months by 4 groups of persons (in all 85 subjects). In the maltitol-, sorbitol- and xylitol-group the plque wet weights were of the same magnitude before and after the test period. In the Lycasin-group, a higher value was found after than before the 3-month period (p less than 0.01). The acid production in suspensions of dental plaque material from Lycasin, maltitol and sorbitol expressed as per cent of that from glucose was approximately the same before and after the test period. From xylitol no acid production could be demonstrated either before or after the 3-month period. There were no statistically significant differences between the plaque pH-changes induced by rinsing with 50% solutions of Lycasin, maltitol, sorbitol or xylitol before and after the test period. However, there was a tendency (p less than 0.05) towards lower pH-values induced by the maltitrol and sorbitol rinse after the 3-month period compared with before. No difference in the relative numbers of facultative anaerobic streptococci. Streptococcus mutans or facultative anaerobic lactobacilli before and after the test period was found.

Duplicate determinations of secretion rate and buffer effect of resting and stimulated whole saliva were made in 629 adults (286 males and 343 females) within an interval of 1-2 weeks. The subjects were arbitrarily classified into four separate age-groups. For all variables studied, a highly significant correlation was obtained between the duplicate tests. The secretion rate of resting as well as stimulated saliva was significantly lower for females than for males. For females, the resting secretion rate was negatively correlated with age. The buffer effect was also significantly lower in the females for both resting and stimulated saliva. For the females, the buffer effect was positively correlated with age and therefore, with advancing age, the females tended to catch up with the males. Irrespective of sex, the secretion rate of resting saliva was highly correlated to that of stimulated saliva. This relationship was established also for the buffer effect. However, between secretion rate and buffer effect a correlation was observed only for stimulated saliva.

Both marginal quality and oral hygiene status have strong effects on the risk of recurrent caries. Although there was no statistically significant interaction between these two parameters in this study, the influence of each variable was dependent on its severity. There is a difference between the behavior or the likelihood of recurrent caries on occlusal surfaces as compared with smooth surfaces. On the smooth surfaces, there is a continued increased risk with decreasing marginal quality; the occlusal surfaces, however, show no change in vulnerability beyond a modified marginal quality score of 3. Variation in oral hygiene had a more pronounced effect on the probability of recurrent caries of restorations with moderate margin scores than it did on restorations with either very poor or very good cavosurface margins. This work further emphasizes the importance of technically good restorative care at the operative visit, which, coupled with conscientious oral hygiene, should have a positive effect on increasing the longevity of restorations and decreasing the need for replacement.

The purpose of the present study was to give a clinical and biochemical characterization of two groups of individuals with different rates of plaque formation. From 133 individuals, 9 "heavy" and 10 "light" plaque formers were selected. The mean plaque index after 3 days of plaque accumulation, on buccal surfaces of premolars and first molars, was 2.6 for the "heavy" and 0.6 for the "light" plaque formers. The following variables were determined: periodontal status, DFS, dietary habits, salivary secretion rate and buffer effect, S. mutans and lactobacillus counts in saliva, salivary content of IgA, lactoferrin, lactoperoxidase and lysozyme, saliva-induced aggregation of certain oral streptococci, gel electrophoresis of saliva, amino acid composition of saliva and the acquired pellicle and retention depth of the dentogingival area. Comparing the two groups of plaque formers, statistically significant differences were found for the following three variables: parotid saliva-induced aggregation of a strain of S. sanguis, content of glutamic acid in the acquired pellicle and retention depth of the dentogingival area for maxillary premolars. Large variations for all studied variables were found, both within and between the groups. Several factors may be involved in plaque formation and none of the studied variables alone could explain the large difference in the amount of plaque formed after 3 days between the "heavy" and "light" plaque formers.