Probiotics and oral health

Over recent years ‘Probiotics’ have emerged on to the scene. Available in a variety of forms including yogurt, milk powders and tablet supplements they have been promoted as ‘the friendly bacteria’ brigade. This archival research review looks at probiotics and oral health and whether the promotion of these probiotic products should be included in our delivery of oral health advice to patients.

It was many years ago when the first signs of the positive role some bacteria had was noted. In 1907, Nobel Prize winner Eli Metchnikoff, made reference to the positive affects of some bacteria, particularly intestinal microbes. However the specific term ‘probiotic’ was not used until 1960 and in 1985 was later redefined by Fuller. A more recent definition by Guarner and Schaafsma in 1998 refers to probiotics as ‘live micro-organisms, which when consumed in adequate amounts, confer a health effect on the host’.

There are many strains of bacteria, estimated somewhere between 5-10 million. The strains which have been noted as probiotics are mainly from the genera Lactobacillus and Bifidobacterium. In the joint FAO/WHO expert consultation it was agreed that ‘for use in foods, probiotic micro-organisms should not only be capable of surviving passage through the digestive tract but all have the capability to proliferate in the gut’. In order to do this the bacteria need to be ‘resistant to gastric juices and be able to grow in the presence of bile under conditions in the intestines, or be consumed in a food vehicle that allows them to survive passage through the stomach and exposure to bile’.

Probiotic bacteria are known to have positive effects on a number of conditions and illnesses, some being:

·         Prevention and treatment of diarrhoea,

·         Crohn’s disease,

·         Constipation,

·         Modulation of immune response and prevention of allergy,

·         Urogenital tract disorders.

The main aim of this review is to consider the research available relating to probiotics and oral health. The oral health categories will focus on dental caries, periodontal diseases, candida and halitosis.

Dental Caries

There have been a number of studies that observe the effect of probiotic bacteria on dental caries. Näse et al. investigated whether milk containing Lactobacillus rhamnosus GG (ATCC 53103) or LGG for short, has an effect on caries and the risk of caries in children when compared with normal milk. The study had a sample size of 594 and was a randomised double-blinded placebo controlled intervention study. The main finding of this study included that less dental caries was seen in the LGG group along with lower mutans streptococcus counts at the end of the study. LGG was found to reduce the risk of caries significantly, with the effect being clearer in the 3-4 year olds. They conclude that milk containing the probiotic bacteria LGG, may have beneficial effects on children’s dental health.

In 2002 Ahola et al. produced a study with the aim to examine whether short term consumption of cheese containing LGG and Lactobacillus rhamnosus LC 705 would diminish caries-associated salivary counts in young adults. This was a double-blinded randomised placebo controlled study involving 74 participants. After the intervention there was no statistically significant difference between the groups in streptococcus mutans counts. However in the post treatment period there was a significant greater reduction in counts in the intervention group. On conclusion it was noted that there had been a ‘trend indicating that probiotic interventions might reduce the risk of the highest level of streptococcus mutans and salivary yeasts’.

Hillman in 2009 reported on the recent study ‘A spontaneous lactate dehydrogenese deficient mutant of streptococcus rattus for use as a probiotic in the prevention of caries’. This was an animal study which involved daily applications of streptococcus rattus strain JH145 to affect the numbers of an implanted streptococcus mutans strain in a rat model. The animals that were treated with JH145 showed a statistically significant decrease in the proportions of implanted streptococcus mutans.

A small (n=10) in-situ study which looked at evaluating fermented milk containing a probiotic on dental enamel and the biofilm found the two experimental groups did not differ significantly but they had smaller mineral losses than the control group.

In 2010, Lexner et al. reported on their recent study entitled ‘microbiological profiles in saliva and supragingival plaque from caries active adolescents before and after a short-term daily intake of milk supplement with probiotic bacteria’. This study took the form of a randomised placebo-controlled double-blind pilot design with two parallel arms. The probiotic bacteria used in this study was Lactobacillus rhamnosus LB21 which showed no significant effect on the microbial profiles or the levels of caries-associated bacteria in the saliva or supragingival plaque samples collected.

More recently in 2011, the probiotic Lactobacillus paracasei was tested to see what effects it had on cariogenic bacterial flora. This was a double-blind randomised placebo-controlled study with 78 participants. The results didn’t show any differences in Streptococcus mutans and lactobacilli counts in either the control or experimental group. However there was some reduction of Streptococcus mutans counts at completion and two weeks later for the probiotic group. This important reduction highlighted that the L. paracasei GMNL-33 may need to be administered for a minimum of two weeks orally for an effective probiotic action to be seen.

Around the same time Lee et al. investigated the ‘antimicrobial activity of bifidobacterium spp. isolated from healthy adult Koreans against cariogenic microflora’. The study highlighted that there are certain species of bifidobacterium ‘which may be a useful probiotic microorganism for prevention of dental caries with no adverse effects’.

A study conducted in early 2012 entitled ‘An in-vitro investigation of Lactococcus lactis antagonising cariogenic bacterium streptococcus mutans’, aimed to evaluate the feasibility of the application of L. lactis for the inhibition of S. mutans in the oral cavity. The results showed that L. lactis competitively inhibited S. mutans growth under nutritional deficiency. They also noted that ‘L. lactis effectively colonised the surface of tooth enamel, which showed substantially less decay with L. lactis adhesion compared to S. mutans adhesion’. Further research is required in this area which potentially could reduce or even eliminate S. mutans adhesion on the surfaces of teeth.

Many other studies have looked at the effect probiotic bacteria have on Streptococcus mutans. Çaglar et al. in 2005 presented a study analysing the effect of yoghurt with Bifidobacterium DN-173 010 on salivary mutans streptococci and lactobacilli in young adults. 21 participants were involved in the double-blind randomised cross-over study. The study had positive results with a statistically significant reduction of salivary mutans streptococci recorded after the probiotic consumption. Similar results were seen for lactobacilli but not of statistical significance.

O’Conner et al. conducted a study which tested the theory of ‘A lacticin 3147 enriched food ingredient reduces Streptococcus mutans from the human oral cavity in saliva’. This study involved saliva samples and S. mutans isolated and characterised. These were then assessed for sensitivity to food grade preparation of lantibiotic, lacticin 3147. Again positive results were seen as concentrated preparations of lacticin 3147 caused rapid killing of S. mutans strains.

Another study by Çaglar et al. entitled ‘Salivary mutans streptococci and lactobacilli levels after ingestion of the probiotic bacterium Lactobacillus reuteri ATCC 55730 by straws or tablets’, involved 120 participants in the randomised placebo-controlled study. The results produced a statistically significant reduction of S. mutans after ingestion of the probiotic bacteria with the straw or tablets. The overall conclusion was that ‘a short-term daily ingestion of lactobacilli-derived probiotics delivered by prepared straws or lozenges reduced the levels of salivary mutans streptococci in young adults’.

In 2008, Haukioja et al. investigated whether ‘in vitro if the probiotic bacteria used in commercial products affect the protein composition of the salivary pellicle and the adherence of other oral bacteria’. Results showed that probiotic bacteria bound to saliva-coated hydroxyapatite which in turn reduced adhesion of S. mutans. It was also noted that the salivary pellicle protein composition was modified by all strains tested, again affecting the adherence of S. mutans.

A further study by Çaglar et al. in 2008 ‘investigated the effect of the probiotic Lactobacillus reuteri, delivered by a new medical device, on levels of salivary mutans streptococci and lactobacilli in young women with high S. mutans counts.’ This randomised, double-blind placebo controlled study involved 20 participants. The results showed a significant reduction of salivary S. mutans levels in the probiotic test group. In 2009 Çaglar investigated ‘whether Lactobacillus reuteri ATCC 55730 can be detected in the oral cavity after discontinuation of administration of a product prepared with this bacterium’. The results showed that the levels of L. reuteri carriers decreased gradually with only 8% of subjects harbouring the bacterium after 7 days. After 5 weeks L. reuteri could not be detected. It was concluded that ‘consuming L. reuteri for 2 weeks does not seem to be sufficient for permanent colonisation of L. reuteri in the oral cavity’.

In 2011 a study was conducted by Samot et al. looking into the adherence capacities of 70 lactobacilli for potential probiotic purposes. There were three tests carried out; biofilm formation on a glass surface and on saliva-coated hydroxyapatite discs and the microbial adhesion to solvent method. Among the 70 strains, 57 didn’t form any biofilm on the glass surface and all strains formed on the hydroxyapatite discs. The most abundant biofilm was formed by Lactobacillus buchneri. It was noted that ‘this work paves the way for the selection of probiotics that could be used for oral health purposes with the aim to reduce carious risk’.

Glavina et al. in 2012 observed the effect of LGG yoghurt on S. mutans and Lactobacillus spp. Salivary counts in children. The study involved 25 children between the ages of 6 and 10 years of age. During the study each participant ‘consumed 200g of yoghurt daily, containing LGG bacteria’ for a period of 14 days. Counts for S. mutans and Lactobacilli were taken before the start of the yoghurt consumption and at 14 and 30 days after the study started. The results showed a ‘statistically significant reduction of S. mutans, after 30 days of daily yoghurt consumption’. For the Lactobacilli there was no significant difference. To conclude, the results from this study showed that a daily intake of LGG yoghurt could have an ‘inhibitory effect on oral pathogenic microflora’. The authors noted that ‘daily consumption of LGG yoghurt can be recommended as a beneficial procedure in caries prevention’.

Periodontal disease

There have been a few studies report on the effect of probiotic bacteria on periodontal health. However these are limited in number and more research is required into this area.

Shumauchi et al. conducted a randomised clinical study ‘to evaluate the effect of probiotic intervention using Lactobacilli on the periodontal condition of volunteers without severe periodontitis’. 71 volunteers took part in this study which involved the administration of a tablet containing Lactobacilli salivarius WB21 and xylitol. The placebo tablet was identical in every way except it only contained xylitol. The participants took a dose of 3 tablets every day throughout the study which was eight weeks in duration. The selection criteria for participants involved:

·         Not currently visiting the dentist for treatment;

·         Not using probiotic supplements;

·         Free from adverse reactions to lactose or fermented milk products;

·         Antibiotics not taken within the last month.

4 of the 71 were excluded, leaving 67 eligible subjects for the study with an age range of 32-61 years. A randomisation process followed to assign the participants to the relevant study groups. To measure the success of the study various outcome measures were introduced. These involved a selection of indices along with saliva and plaque sampling, measurements of lactoferrin in saliva and detection of L. salivarius in the collected saliva and plaque samples.  Firstly they compared the amount of Lactobacilli in the saliva and plaque samples for both groups. The amount of L. salivarius present in the saliva initially decreased for both groups. However a significant difference was noted at 8 weeks between both groups. In the supra- and subgingival plaque samples there was a decrease seen for both groups at 4 and 8 weeks. Salivary lactoferrin levels decreased significantly in the test group after the 8 week study. When reviewing the indices, both groups saw a reduction in BOP, Gingival index (Löe and Silness) and Plaque index (Silness and Löe) at 4 and 8 weeks. It was also noted that there was a significant decrease in the plaque index and PPD at 4 and 8 weeks for the current smokers when compared with the placebo group. The main findings from this study showed using an orally administered tablet of ‘L. salivarius WB21 significantly decreased the plaque index and PDD of smokers suggesting clinical improvement of the periodontal condition by probiotic intervention’. The levels of salivary lactoferrin were also found to be significantly different in smokers. They conclude that their ‘results suggest that a probiotic intervention could be a useful tool for the treatment of inflammation and clinical symptoms of periodontitis, especially in high risk subjects’. The study was conducted on a small scale (n=67), further studies of RCT design would be useful to determine whether probiotics should be incorporated into treatment plans for periodontal disease patients.

Tsubura et al. observed the effect of Bacillus subtilis mouth rinsing in patients with periodontitis. 54 non-smoking participants were involved in this study, with an age range of 44-62 years. All participants had chronic periodontitis but no general diseases. All participants had 20 or more teeth and probing depths of >4mm on molar teeth in at least 8 sites. The test group rinsed with the E-300, Bacill s subtilis mouth rinse, twice a day for 1 month. Various measurements were recorded for all participants, PPD, BOP and gingival index at baseline, 2 weeks and 1 month. In addition to this a plaque test was also carried out to establish the presence of periodontal pathogens. The results showed that E-300 had no effect on PPD and BOP at 1 month recording. However the gingival index reduction was evident although this was not statistically significantly different with the control group. When the results were reviewed it showed that E-300 was significantly more effective on these scores for the duration of the study compared with the control. The authors note the positive effects that E-300 had on the gingival index and plaque test scores, which may lead to the control of chronic or acute periodontitis.

In 2011, Slawik et al. examined how ‘probiotics affect the clinical inflammatory parameters of experimental gingivitis in humans’. A total of 28 participants were involved in this clinical study, all of which had healthy gingiva. The test group consumed the probiotic milk drink, Yacult, every day for 1 month. ‘After 2 weeks of consumption of the probiotic drink, participants were advised not to brush their teeth for 14 days’, to induce experimental gingivitis. Indices were recorded at baseline, day 1, 3, 5, 7 and 14. On review of the results it was noted that ‘at baseline, the plaque index was significantly higher in the test group compared with the controls’. When individuals ceased oral hygiene this saw an increase in the clinical parameters, for both groups. The BOP levels and gingival crevicular fluid volume ‘were significantly lower in the test group compared with the control group’ at day 14. The authors conclude that ‘a daily consumption of a probiotic milk drink reduces the effects of plaque-induced gingival inflammation associated with higher plaque scores due to the high-carbohydrate content of the probiotic milk beverage’.

A recent study by Iniesta et al. observed the probiotic effects of orally administered Lactobacillus reuteri containing tablets on the subgingival and salivary microbiota in patients with gingivitis’. This randomised clinical trial involved 40 healthy subjects with gingivitis. One tablet was chewed per day for a total of 28 days. The test tablet contained 2 strains of L. reuteri. Clinical examinations took place at baseline, 4 and 8 weeks recording plaque and gingival indices. In addition, saliva and subgingival plaque samples were also taken at the same intervals. No significant differences were recorded in the indices. However changes were noted in the saliva and subgingival plaque samples, mostly a ‘reduction in the number of selected target periodontal species’. Overall the results of this study ‘indicate that the use of L. reuteri containing tablet was associated with a significant reduction in total bacterial counts and P. intermedia in saliva and with a clear reduction in the counts of different target periodontal pathogens in subgingival samples, such as P. gingivalis’. However ‘these microbiological changes did not translate into a significant clinical impact’.

As previously mentioned the amount of studies conducted looking at probiotics and periodontal disease are limited. Few have taken place and those that have are often involving low numbers of participants. Further research is required in this area before adequate conclusions can be drawn on the suitability of probiotics in the management and treatment of periodontal diseases.

Other oral manifestations

Along with periodontal disease and dental caries, Scientists are investigating the use of probiotics for the treatment of candida and halitosis. In 2007, Hatakka et al. produced a clinical research report entitled ‘probiotics reduce prevalence of oral candida in the elderly ­ a randomised clinical trial’. This study involved ‘independent elderly people aged 70-100 years’ who were living in ‘old people’s homes and sheltered housing’. The study took place in Helsinki, Finland with 276 participants. ‘This randomised, double blind, placebo-controlled study with two parallel groups, was carried out between January 2001 and March 2002. The intervention lasted for 16 weeks with participants consuming either 50g of Emmental type probiotic cheese or 50g of Edam type control cheese. The probiotic cheese contained Lactococcus lactis, Lactobacillus helveticus, L. rhamnosus GG (ATCC 53103) L. rhamnosus LC705 and Propionibacterium freudenreichii ssp shermanii JS. The control cheese contained Lactococcus lactis but no probiotic strains. Participants underwent a clinical examination at the start and end of the intervention. Details were recorded on DMFT, number of prosthetic appliances, community periodontal index (BPE) and mucosal lesions. Oral yeast saliva sampling was also undertaken four times during the study. The results of the intervention showed:

·         30.4% of the probiotic group had high yeast counts at baseline;

·         28% of the control group had high yeast counts at baseline;

·         At 8 and 16 weeks yeast counts had diminished to 25% and 20.7% respectively for the probiotic group;

·         At 8 and 16 weeks yeast counts had increased to 31% and 34% respectively for the control group;

·         On completion of the study, yeast count risk for the probiotic group had decreased for the probiotic group compared with the control group.

In the discussion the authors note that the ‘probiotic treatment reduced the risk of the high yeast counts by 75%’. This particular study also highlighted that ‘probiotic treatment reduced the prevalence of hyposalivation and a subjective feeling of dry mouth’. The increase in yeast counts in the control group was speculated to be caused by ‘the absence of the protective effects of probiotics, together with increased hyposalivation, might explain the increase in candida growth in the control group.’ This particular study showed ‘that probiotic bacteria can reduce the prevalence of oral candida in the elderly, therefore probiotics could be used by patients regularly to reduce candida’. In addition to this probiotics could be used by patients to help with dry mouth as this study showed that probiotics reduce the risk of hyposalivation. Although positive results were seen in this particular study which involved a large sample size, further studies are required to confound this evidence.

Probiotics have also been investigated as to their ability to effect oral malodour or halitosis. Burton et al. in 2006 reported ‘a preliminary study of the effect of probiotic Streptococcus salivarius K12 on oral malodour parameters’ It was a relatively small study involving 23 participants with an age range of 18-69 years. Volatile sulphur compound (VSC) levels were measured and those having VSC scores higher than 200 ppb on 2 separate visits were included in the study. Both groups followed the same oral hygiene regime. The test group sucked on a lozenge which contained S. salivarius K12 at 2 hour intervals over 8 hours. The control group sucked a placebo lozenge that contained no bacteria. At various intervals, VSC levels and saliva samples were taken and analysed. The results of the study appear to be promising as ‘the VSC readings of 11 of the 13 test subjects had decreased by more than 100 ppb’ with a further 8 participants having reduced their levels at day 14. There were a small number of subjects involved in this study and for further evidence more studies of similar design but with an increased number of subjects would be required.

Whilst studies have been conducted for a number of years on the efficacy of probiotics in the treatment of dental diseases and oral manifestations; the use of probiotics in the prevention of dental caries has been the area where most of the research has taken place. There have been positive effects observed with Lactobacillus and Bifidobacterium genera in the prevention of dental caries. Again positive results have been seen in the prevention and treatment of periodontal disease, however further research is required in this area with results gathered from robust studies. Using probiotics in the treatment of candida and halitosis have shown positive signs but studies in this area are lacking.

The treatment and prevention of dental disease is ever evolving. In the future the prescription of probiotics for patients may become the norm, or maybe we will just be sending our patients to Sainsburys for a supply of Yacult!


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