Oral malodour--a review.

Halitosis is a very common condition which may affect up to 30% of the population. In most cases the aetiology of the condition is from local oral causes (oral malodour). Oral malodour is the result of the action of anaerobic bacteria in producing a range of malodorous molecular species including volatile sulphur compounds. Whilst malodour is often associated with the presence of periodontitis, in many cases there is no such link, and the evidence points to the importance of these anaerobic bacteria in tongue coatings which results in the clinical presentation of oral malodour. Management of oral malodour is directed at managing and reducing the bacterial load both in periodontitis and in tongue coatings by instituting proper oral hygiene measures, control of tongue flora by brushing or scraping, and possibly the adjunctive use of antiseptic agents. Treatments have also been proposed to neutralise malodorous compounds by chemical agents to mask the presence of the condition. Further evidence is required to demonstrate the long-term efficacy of therapies for this troublesome condition.

Impact of different tongue cleaning methods on the bacterial load of the tongue dorsum.

OBJECTIVE: To assess the extent and duration of the effect of tongue cleaning procedures on bacterial load on the dorsal surface of the tongue. METHODS: 19 subjects participated in this blinded crossover study. Subjects abstained from oral hygiene, eating and drinking from 22:00 h the previous evening. Tongue samples were collected at baseline and within 15 minutes of one of three procedures: teeth brushing alone; teeth brushing plus tongue scraping; teeth brushing plus tongue cleaning using a high speed vacuum ejector and irrigation with 20 ml antibacterial mouthwash. Subjects then brushed twice daily for 3 days apart from the second group who additionally scraped their tongue twice daily. On day 4, baseline and post-treatment samples were collected as per day 1. Bacteria (total anaerobes, Gram-negative anaerobes, VSC-producing bacteria and Streptococcus saliuarius) were enumerated using appropriate selective media. RESULTS: The tongue dorsum was colonized by all 4 bacterial categories (log(10) 6-8 cfu/sample). For subjects who brushed their teeth only, there was a significant reduction from baseline for S. saliuarius only. In contrast, tooth brushing plus tongue scraping resulted in statistically significant reductions from baseline for all bacterial categories (range log(10) 0.11-0.40 cfu/sample). Highly statistically significant reductions (log(10) 1.11-1.96 cfu/sample) were observed for subjects who underwent thorough tongue cleaning with the saliva ejector/mouthwash. To determine longevity of treatment effects, baseline bacterial loads for days 1 and 4 were compared. Only daily tongue scraping resulted in statistical significant reduction in baseline microbial loads on day 4. CONCLUSION: While mechanical tongue cleaning with or without chemical intervention can reduce bacterial load on the tongue, this effect is transient, and regular tongue cleaning is required to provide a long lasting (overnight) reduction in bacterial numbers. Nevertheless, tongue cleaning is an oral hygiene procedure that is little practiced due to discomfort and/or lack of awareness on the part of dental professionals and their patients.

Removal of oral debris and bacteria during supervised tooth brushing.

OBJECTIVE: To investigate foam generation during brushing, and the oral debris and bacteria removal efficacy of an experimental gel-to-foam dentifrice compared to a commercially-available dentifrice after brushing. METHODS: Thirty-four subjects participated in this blinded, crossover study. After a wash-out period prior to each session of product use, subjects reported to the site having abstained from oral hygiene, eating and drinking from 22:00 h on the evening prior to treatment visits. The subjects brushed with a weighed dose of assigned paste and were asked to expectorate their toothpaste slurry into a collection vessel at 30 and 60 seconds during supervised brushing. The expectorated foam was measured immediately, after which subjects rinsed with 10 ml of sterile water and expectorated into the same vessel. Samples were placed on ice and immediately transported to the laboratory for analysis. Bacteria (total anaerobes and VSC-producing bacteria) were enumerated using appropriate selective media. To calculate the amount of debris, a measured portion of the sample was deposited onto a pre-weighed dish and weighed. Dishes were dried thoroughly and weighed again after cooling. RESULTS: Use of the gel-to-foam dentifrice resulted in 105% greater foam volume compared with use of the control dentifrice (p < 0.0001). Further, the gel-to-foam dentifrice removed 15.77% more debris than the control dentifrice (p-value = 0.0342). There was greater removal of total anaerobes and VSC-producing bacteria by the gel-to-foam dentifrice versus the control dentifrice (p-value < 0.0001). CONCLUSION: Single use of a gel-to-foam dentifrice generated a greater volume of foam and removed a greater amount of oral debris and bacteria during brushing than a standard dentifrice.

Topographic distribution of bacteria associated with oral malodour on the tongue.

OBJECTIVE: To investigate the topographic distribution of bacterial types and loads associated with mid-morning oral malodour on the tongue surface. DESIGN: Fifty subjects with good oral health and at least 20 natural uncrowned teeth were included. Samples were taken with sterile brushes from the dorsal anterior (DA), dorsal middle (DM), dorsal posterior (DP), dorsal posterior to the circumvallate papillae (DPCP), lateral posterior (LP) and ventral posterior (VP) tongue surfaces. Samples were cultured on appropriate media for anaerobic bacteria, aerobic bacteria, Gram-negative anaerobic bacteria, volatile sulphur compound (VSC)-producing bacteria and Streptococcus saliuarius. Malodour was assessed by trained judges on an intensity basis. RESULTS: The counts of all bacterial groups were consistently highest at the DPCP surface. Mean VSC-producing bacterial counts (colony forming units/brush x10(5)) were 1.45, 5.67, 32.52, 88.94, 6.46 and 0.33 at DA, DM, DP, DPCP, LP and VP surfaces, respectively. Anaerobic, Gram-negative and VSC counts at DPCP surfaces increased with malodour intensity, whereas aerobic and S. saliuarius counts decreased; however these differences were not statistically significant. CONCLUSION: It is concluded that the DPCP area consistently carries the highest load of bacteria capable of contributing to oral malodour. The study demonstrates that tongue surfaces not accessible to routine oral hygiene procedures can significantly contribute to oral malodour.

Control of brushing variables for the in vitro assessment of toothpaste abrasivity using a novel laboratory model.

OBJECTIVES: Design and construct a tooth-brushing simulator incorporating control of brushing variables including brushing force, speed and temperature, thereby facilitating greater understanding of their importance in toothpaste abrasion testing methodologies. METHODS: A thermostable orbital shaker was selected as a base unit and 16- and 24-specimen brushing rigs were constructed to fit inside, consisting of: a square bath partitioned horizontally to provide brushing channels, specimen holders for 25 mm diameter mounted specimens to fit the brushing channels and individually weighted brushing arms, able to support four toothbrush holders suspended over the brushing channels. Brush head holders consisted of individually weighted blocks of Delrin, or PTFE onto which toothbrush heads were fixed. Investigating effects of key design criteria involved measuring abrasion depths of polished human enamel and dentine. RESULTS: The brushing simulator demonstrated good reproducibility of abrasion on enamel and dentine across consecutive brushing procedures. Varying brushing parameters had a significant impact on wear results: increased brushing force demonstrated a trend towards increased wear, with increased reproducibility for greater abrasion levels, highlighting the importance of achieving sufficient wear to optimise accuracy; increasing brushing temperature demonstrated increased enamel abrasion for silica and calcium carbonate systems, which may be related to slurry viscosities and particle suspension; varying brushing speed showed a small effect on abrasion of enamel at lower brushing speed, which may indicate the importance of maintenance of the abrasive in suspension. CONCLUSIONS: Adjusting key brushing variables significantly affected wear behaviour. The brushing simulator design provides a valuable model system for in vitro assessment of toothpaste abrasivity and the influence of variables in a controlled manner. Control of these variables will allow more reproducible study of in vitro tooth wear processes.

Determining the antibiotic resistance potential of the indigenous oral microbiota of humans using a metagenomic approach.

Studies of the prevalence and identity of genes encoding resistance to antibiotics in a microbial community are usually carried out on only the cultivable members of the community. However, it is possible to include the as-yet-uncultivable organisms present by adopting a metagenomic approach to such studies. In this investigation, four metagenomic libraries of the oral microbiota were prepared from three groups of 20 adult humans and screened for antibiotic-resistant clones. Clones resistant to tetracycline and amoxycillin were present in all four libraries while gentamicin-resistant clones were found in three of the libraries. The genes encoding tetracycline resistance in the clones were identified and found to be tet(M), tet(O), tet(Q), tet(W), tet37 and tet(A). However, only the first three of these were detected in all three groups of individuals investigated.

Microbial dinner-party conversations: the role of LuxS in interspecies communication.

Bacteria have a tendency to be gregarious by nature. Whether on abiotic surfaces in the environment or on the mucosal surfaces of humans, bacteria accumulate in complex multi-species communities. In these dynamic accretions, bacteria can be densely packed and often depend on each other for the provision of metabolic substrates. Under these circumstances, it will be advantageous for bacteria to be able to detect the presence of their neighbours, to communicate with them and to co-ordinate various physiological activities. Such cell-cell sensing and communication systems can be established through the release and detection of chemical signalling molecules. While originally considered a feature characteristic of eukaryotes, the exchange of chemical signals has now been demonstrated in many bacterial species and ecosystems. Indeed, it has even been suggested that assemblages of bacterial species can be considered as proto-multicellular organisms, whereby biological processes are controlled for the benefit of the entire community. Regardless of the extent to which bacterial communication represents a step on the road to multicellularity, it is becoming increasingly apparent that the signalling systems devised by bacteria are essential for successful relationships with other bacteria and with eukaryotic hosts.

Streptococcus sanguis secretes CD14-binding proteins that stimulate cytokine synthesis: a clue to the pathogenesis of infective (bacterial) endocarditis?

Streptococcus sanguis is the major causative organism of infective (bacterial) endocarditis but, surprisingly, almost nothing is known about how it induces endocardial inflammation. In earlier studies we have shown that many bacteria secrete potent cytokine-inducing or -inhibiting proteins. We have therefore isolated the material secreted by S. sanguis grown on blood agar or in broth culture and have tested its ability to induce human peripheral blood monocytes to synthesize pro-inflammatory cytokines. The activation of monocytes by the secreted components of S. sanguis was almost totally blocked by heat and trypsin treatment but not by the lipopolysaccharide-inactivating antibiotic, polymyxin B, suggesting that activity is due to secreted proteins. The activity of the secreted material was significantly reduced by anti-CD14 monoclonal antibodies suggesting that the active protein (or proteins) was binding to the CD14/Toll-like receptor (TLR)4 complex. Fractionation of the secreted proteins by high performance liquid chromatography (HPLC) identified two proteins as being responsible for the majority of the cytokine induction: a manganese-dependent superoxide dismutase and a 190 kDa protein, which could not be sequenced, but which was neither CshA nor the PI/II proteins. These proteins, or the receptors to which they bind, may be therapeutic targets and may allow the development of adjunctive therapies to prevent endocardial damage during the often prolonged treatment of infective endocarditis with antibiotics. In addition, blocking of CD14 may have some therapeutic benefit.

Interruption of the Streptococcus gordonii M5 sspA/sspB intergenic region by an insertion sequence related to IS1167 of Streptococcus pneumoniae.

Streptococcus gordonii M5 and DL1 each express two related adhesin polypeptides, SspA and SspB, which are members of the antigen I/II family of streptococcal surface proteins. The sspA and sspB genes are tandemly arranged in both strains, with sspA residing upstream of sspB. The genes are separated by approximately 400 nucleotides in S. gordonii DL1 and 1300 nucleotides in S. gordonii M5. The nucleotide sequence of the sspA/sspB intergenic region of strain M5 is reported and the difference in length compared to S. gordonii DL1 shown to arise from the presence of an insertion sequence, designated ISSg1, consisting of 1197 bp. The nucleotide sequence of ISSg1 is highly homologous to IS1167 to Streptococcus pneumoniae and is related to a lesser extent to other members of the IS1096 family of bacterial insertion sequences. It contains a single ORF of 1026 bp, encoding a putative transposase polypeptide of 342 amino acids. The deduced transposase sequence exhibits 93% identity with the transposase polypeptides encoded by IS1167. However, the S. gordonii protein lacks a 90 residue central domain that is present in the IS1167 transposase and in the transposase polypeptides encoded by the related IS elements. In addition, the organization of the inverted repeats flanking the transposase gene in S. gordonii differs from IS1167. Extension products generated from a sspB-specific primer indicated that transcription initiates within the intergenic region in both S-gordonii strains, suggesting that sspA and sspB are independently transcribed. Transcription appears to initiate 42 bases upstream of sspB in S. gordonii DL1. In contrast, sspB transcription in M5 initiates at least 125 bases upstream of sspB, in close proximity to the terminal inverted repeat of ISsg1. These results indicate that the sspB promoter of S. gordonii M5 and DL1 are not conserved and suggest that ISSg1 sequences may play a role in directing the expression of sspB in S. gordonii M5.