Antibacterial activity of yoghurt against viridans streptococci in vitro.

OBJECTIVE: Yoghurt consumption leads to a selective decrease in the oral level of mutans streptococci. It is not clear whether this decrease is due to the bactericidal activity of yoghurt or other mechanisms. The present study investigated the differences in susceptibility to yoghurt between several strains of viridans streptococci. DESIGN: The sources of variation were minimised, at the expense of the external validity of the study, using culture collection strains. Each strain was tested separately on five occasions in planktonic form and logarithmic growth phase. Two strains of each of the following Streptococcus species were tested: mutans, sobrinus, gordonii, oralis, parasanguinis and sanguinis. One millilitre [10(8) colony-forming units (cfu)] of each strain was incubated (37 degrees C, 60min) with 9mL of fat-free plain yoghurt containing Streptococcus thermophilus and Lactobacillus bulgaricus (10(8) and 10(7)cfu/g, respectively) in gently vortexed tubes. Survival rates were calculated every 15min by dividing the number of viable cells, obtained using conventional laboratory procedures, by the baseline number. RESULTS: Survival rates were 8% (S. mutans 6519T), 12% (S. mutans 31738), 35% (S. oralis 25671) and >50% (all other species tested) after 15min, and 0.01% (S. mutans) and >10% (all other species tested) after 30min. Overall, S. parasanguinis and S. sobrinus were the most resistant species. When heat-treated yoghurt (<10cfu/g bacteria and inactivated bacteriocins) was used, this antibacterial activity was not found. CONCLUSION: In vitro, yoghurt with live bacteria showed selective anti-mutans activity, suggesting that the overall decrease in mutans streptococci in vivo could be due to a bactericidal effect on S. mutans but not on S. sobrinus.

[Health-related behaviour and HCV prevalence among elderly and younger adults in an isolated community close to Rome (Italy)]. / Abitudini comportamentali e prevalenza di HCV in anziani e giovani di una comunità del frusinate.

The aim of this study has been to investigate the differences in the health-related behaviour by means of a questionnaire in a sample of elderly (>54 years, 1st generation) and younger adults (<54 years, 2nd generation, all of them sons/daughters of HCV positive subjects), given the high difference in HCV positive prevalence among the two groups (19.4% vs. 2.1%). Most (53.4% vs. 0.0%) of the 1st generation subjects used glass syringes while all the 2nd generation subjects used disposable syringes. Among the elderly, the frequency of hospitalisation (70% vs. 50%), transfusions (11.8% vs. 2.9%) and dental therapy by false dentists (52% vs. 0%) were higher. These results show that the use of non recyclable syringes is the main responsible for the drastic reduction of HCV circulation in the present community, and the consequent decrease in the risk for infection in younger subjects. Moreover, dental therapy was not related to an increased risk for infection, providing that the treatment has been made by a "true" dentist. Finally, the intrafamiliar transmission was not supported by the present data.

A randomized clinical trial of the effect of yoghurt on the human salivary microflora.

Yoghurt is active against some human pathogens, so this experiment tested whether it is also active against the salivary microflora. A clinical trial was designed, with volunteers aged between 23 and 37 years. Initially, for 8 weeks, they consumed neither yoghurt nor casein-free soybean ice cream (phase 1). They were then split randomly into test (yoghurt) and control (ice cream) groups and required to consume 125 g of these foods twice daily for 8 weeks (phase 2) and then to avoid them for the following 2 weeks (phase 3). Many potential sources of microbial fluctuation were standardized. Salivary samples were then collected at regular intervals of 2 weeks. For each group and phase, the mean logarithms of the salivary counts for total viable flora, oral streptococci, mutans streptococci, lactobacilli and Candida were calculated. The prevalence of Streptococcus thermophilus and Lactobacillus bulgaricus was also assessed. Twenty test and 22 control participants completed the study. At phase 2, the mean for mutans streptococci was lower in the test than in the control group (3.6 vs. 4.0 log colony-forming units/ml; P=0.02). Moreover, the mean had decreased in all test participants with high phase 1 means for lactobacilli as compared to only 36.4% of those with low phase 1 means (P=0.01). L. bulgaricus was transiently detected in three test participants during phase 2. These results suggest that yoghurt does have some activity against the salivary microflora, but this does not seem to be due to the installation of yoghurt microorganisms in the mouth.

The effect of milk and sucrose consumption on caries in 6-to-11-year-old Italian schoolchildren.

The effect of milk on dental caries was studied on a sample of 6-to-11-year-old Italian schoolchildren. The daily amount of milk consumed and the frequency of consumption of sucrose-containing foods were obtained by a 24-hour dietary diary. In the subsequent oral examination, the level of visible plaque and the number of decayed, extracted and filled teeth (both primary and permanent) of the children were recorded. 439 children (217 boys) who did not use fluoride prophylaxis and with poor oral hygiene were selected from among 890 children. They were divided into three groups according to the frequency of sucrose consumption. The data were statistically analysed using multiple logistic regression. The children consumed a daily average of 209 +/- 133 ml of milk and there were no differences among the three groups in this respect. As expected, the dental health of the children with low sucrose frequency was significantly better than that of the children with high sucrose frequency. The regression on the whole sample showed a weak, significant, negative association between milk consumption and caries (p < 0.05). In the group of high sucrose-consuming children a negative, highly significant association was found (p < 0.001), while in the two groups of low and moderate sucrose-consuming children no association was found. These data suggest that, in the present sample of children who did not use fluoride and with poor oral hygiene, milk has a caries preventive effect only on those subjects with a high daily sucrose-consuming frequency.

Restoration-related salivary Streptococcus mutans level: a dental caries risk factor?

OBJECTIVES: The salivary level of Streptococcus mutans related to filled teeth was compared with the levels related to decayed and sound teeth, in order to establish whether the presence of restorations may increase the risk of infection of other teeth by Streptococcus mutans. METHODS: The sound, decayed and filled teeth were recorded in 809, 6-7-year-old school-children. Salivary Streptococcus mutans detection (i.e. more than 1 x 10(4) CFU/ml) and counts were evaluated. Streptococcus mutans log count means and prevalence values of subjects with only sound teeth (group 1), with filled, without decayed teeth (group 2), with decayed, without filled teeth (group 3), were calculated and compared using the Student's t-test and the chi-square test. The effect of filled, decayed and sound teeth on Streptococcus mutans level was also evaluated using logistic regression. RESULTS: Log count means and prevalence values of group 2 subjects were significantly lower than values of group 3 subjects (means, 0.92 vs 1.66: prevalence, 73.17% vs 94.63%) and statistically not-different from values of group 1 subjects (mean. 0.75: prevalence, 70.06%). The logistic regression analysis showed that the factors significantly increasing the risk of Streptococcus mutans being detected in saliva were only primary and/or permanent decayed teeth. The risk of Streptococcus mutans being detected in saliva was not affected by filled teeth more than sound teeth. CONCLUSIONS: In the present study population, the salivary Streptococcus mutans level attributable to filled teeth was low; this suggests that treatment of a carious lesion would cause a lowering of Streptococcus mutans concentration to the same levels as those shown by healthy subjects, thus reducing the risk of infection to other teeth.

Effect of orthodontic therapy with fixed and removable appliances on oral microbiota: a six-month longitudinal study.

The present study evaluated microbiological and clinical changes occurring during the first six months of orthodontic therapy with fixed and removable appliances and the consequent risk for gingivitis and periodontal disease. This study was justified by the disagreement among different authors: only some of them reported gingivitis development and changes in dental plaque composition during orthodontic therapy with fixed appliances, others did not. Thirty, 7-to-15-year-old children, fifteen with fixed and fifteen with removable appliances, previously motivated to oral hygiene, completed the study. They were clinically examined by a dentist at baseline and at the end of the study. Three supra and subgingival microflora samples were collected from the first molars, when the appliances were inserted (T0), 6-8 weeks later (T1) and 6-7 months later (T2). Microflora was examined using dark-field and light microscopes and cultural methods. An indicator of healthy status (percentage of Gram positive cocci in total bacterial count) and some risk indicators for gingivitis (bacterial count evaluated with light microscope, percentage of Gram negative rods) and for periodontitis (motile rod and spirochete percentages, presumptive Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis prevalence) were investigated. Patients with fixed appliances were clinically healthy at T2; yet they showed significantly increased counts, motile rods, subgingival spirochetes and a decrease of Gram positive cocci. At T2, patients with removable appliances were clinically healthy and the only significant microbiological changes were supragingival motile rods and subgingival spirochetes. These data suggest that in the oral hygiene motivated patients of the present study, gingivitis and periodontitis do not occur, during the first six months of treatment: the significant modification of oral microbiota, shown by subjects with fixed appliances, however, suggests that the risk for gingivitis in the following months of therapy is still high and the risk for periodontitis cannot be excluded.

[Use of a microwave device for dental instrument sterilization: possibilities and limitations]. / L'impiego di un apparecchio a microonde nella sterilizzazione di strumentario odontoiatrico: possibilità e limiti.

BACKGROUND: The aim of the present study was the evaluation of the effectiveness as sterilizer of a modified version of a microwave device, which was previously tested by the same authors and found unsatisfactory. MATERIALS AND METHODS: Dental mirrors were contaminated by 10(4)-10(9) microorganisms of Stapbylococcus aureus and spores of Bacillus subtilis and Bacillus stearothermophilus. The inocula used were both wet and dry. The duration of the treatment was 4 minutes. Three series of tests were made: 1) microwaves and "adjuvant" solution (as suggested by the producer of the device); 2) microwaves only (in place of the "adjuvant" solution, a Na Cl 0.9% was used); 3) "adjuvant" solution only (into an oven at 25 degrees C). RESULTS: In the 1st and 3rd series of tests all the microorganisms and the spores were killed. In the 2nd series of tests a bactericidal effect against some, not all, microorganisms of the S. aureus species and against spores of B. subtilis and B. stearothermophilus was found. CONCLUSIONS: The results of this study suggest that the device tested has a sterilizing activity, which, however, is not due to the activity of microwaves only; but to the combined activity of microwaves, "adjuvant" solution and temperature (since inside the device, at the end of the treatment the temperature on the mirrors was 94 degrees C).

[Dental health and the state of oral hygiene in an elderly population in Rome]. / La salute dentale e i comportamenti di igiene orale in una popolazione anziana di Roma.

The purpose of this study was to investigate dental conditions and oral hygiene in a population of 369 elderly people residing in Rome--293 females and 76 males--aged between 60 and 99 years (mean 81.9 +/- 8.1). The sample was interviewed following a dental examination. Clinical tests revealed that 40% were totally edentulous, whereas subjects with natural teeth had a mean of 11.4, teeth, of which 1.5 were decayed. Oral hygiene habits were investigated by means of questions on use of dental tools (toothbrush, mouth-wash, dental floss), which were not much used. Moreover, many elderly people reported they had not been to the dentist's recently (86.2% during the last year) because they did not feel it necessary. From this study a rather low level of oral health has emerged, along with a limited knowledge of prevention for dental and periodontal diseases. These results show the need of dental treatment and prevention for the elderly population.

[A new device for the disinfection of handpieces and turbines]. / Su un nuovo apparecchio per la disinfezione di manipoli e turbine.

Dental handpieces are often difficult to disinfect. This is one of the main reasons for the considerable risk of cross-infections in dental offices. The aim of the present study was the evaluation of the disinfectant property of a recent, commercially available, automatic instrument, described as capable to clean, disinfect and lubricate dental handpieces. The following experimental evaluations were made: 1) antimicrobial activity of the disinfectant (glyoxalaldehyde) used. The method described by the European Committee for Standardization was followed. Test microorganisms were Pseudomonas aeruginosa and Staphylococcus aureus. 2) disinfection of dental handpieces (69 contra-angles and 97 turbines of different marks). They were naturally infected using them on patients for 30 minutes at least. 3) disinfection of dental handpieces infected with bacterial suspensions of Staphylococcus aureus, Streptococcus pyogenes (beta-haemolyticus, group A), Candida albicans and Pseudomonas aeruginosa. The results of the first experiment showed a strong bactericidal power of the disinfectant with both the tested strains, after a contact time of only 1 minute. A great proportion of the dental handpieces tested during the second experiment were found disinfected: from 84% through 89% out of the various models of turbine handpieces; from 89% through 100% out of the models of contra-angle handpieces. Even though bacterial contamination level was low (about 10(3) microorganisms per handpiece), a satisfactory disinfectant ability in natural conditions was found. The results of the third experiment were unclear. The tested instrument reduced 10(5)-10(8) times the original bacterial count when the gram positive microorganisms (Staphylococcus aureus, Streptococcus pyogenes) were used. On the other hand, when Pseudomonas aeruginosa and Candida albicans were used, the results were different: the bacterial count was reduced 10(6)-10(7) times in some cases, and only 10(2) times in other cases. This difference was found in the tests made using the same attachment and in those made using various attachments. In conclusion, the tested instrument showed, in most cases, a good disinfectant property, but the presence of unclear results suggests that some technical modifications are required.