Mel Rosenberg

Reproducibility and Sensitivity of Oral Malodor Measurements with a Portable Sulphide Monitor

Forty-one subjects with bad breath were assessed for oral malodor and periodontal status on three occasions, at intervals of approximately one week. Oral malodor was assessed by measurement of peak and steady-state volatile sulphide levels with a portable sulphide monitor and by organoleptic measurement of whole-mouth, tongue dorsum, and interproximal dental odors by two independent judges. Reproducibility of measurements, assessed by paired t tests and Kappa testing, demonstrated no significant differences between any ofthe test results from the first and second appointments. Steady-state sulphide levels were the most reproducible of all tests. The ability of the tests to detect an expected reduction of malodor following a 0.2% chlorhexidine mouthrinse regimen was investigated by comparison of test values between the second and third appointments. Following the mouthrinsing treatment, 43% reductions of peak, 47% reductions of steady-state volatile sulphide levels, and 15-58% reductions in all other measurement categories were observed. The majority of the participants (22/41) had no pockets greater than 5 mm and exhibited both moderate gingival inflammation (Mean Gingival Index = 1.17) and moderate plaque accumulation (Mean Plaque Index = 1.84). Plaque Index and presence of pockets greater than 7 mm were weakly related to sulphide measurements. Whereas assessment of steady-state sulphide levels by the sulphide monitor does not constitute a direct measure of oral malodor, its relation to organoleptic measurement, superior reproducibility, objectivity, and sensitivity support the use of the sulphide monitor in clinical studies.

Hydrophobic Interactions: Role in Bacterial Adhesion

The last decade has seen a dramatic rise in scientific interest in the field of bacterial adhesion and related subjects. Much of this interest has been directed in search of “specific interactions” between bacterium and substratum, such as those that are inhibited by specific sugar moieties. A second avenue of research has been the study of the role of less specific, hydrophobic interactions. Since it appears that this second avenue of research is being increasingly followed, reviews dealing with bacterial hydrophobicity and adhesion should be of use. The aims of the present chapter are to (1) present some relevant aspects of hydrophobic interactions; (2) describe the methodology available for measurements related to bacterial cell-surface hydrophobicity and the parameters they may measure; (3) discuss investigations dealing with surface components that promote or reduce bacterial hydrophobicity; and (4) survey studies related to the role of hydrophobic interactions in mediating bacterial adhesion to interfaces, traversing areas of environmental and medical interest.

Cadaverine as a Putative Component of Oral Malodor

Whereas previous studies have shown correlations between volatile sulphur compounds (VSC) and bad breath levels, it is probable that other compounds found in the oral cavity may contribute to oral malodor. In the present investigation, the possibility that diamines (cadaverine and putrescine) are associated with oral malodor parameters was assessed. Saliva samples from 52 subjects were analyzed for cadaverine and putrescine by HPLC. Oral malodor of whole mouth, tongue, and saliva of the subjects was recorded by an experienced judge on a continuous 10-cm scale; peak and steady-state VSC intraoral levels were measured by the Interscan 1170 sulphide monitor. Log-transformed VSC and diamine levels were compared with odor judge measurements by Pearson analysis and stepwise forward multiple regression. Putrescine scores were not significantly associated with odor judge parameters or with VSC levels (p > 0.1). However, highly significant correlations (p ≤ 0.003) were found between cadaverine levels and all three odor judge assessments. In contrast, associations between cadaverine and VSC measurements were non-significant. In an attempt to correlate odor judge results in terms of both VSC and diamines, we carried out stepwise forward multiple regression. Results showed that VSC and cadaverine both factor significantly in explaining each of the odor judge measurements, with multiple r values ranging from 0.545 (p = 0.0002) to 0.604 (p < 0.0001). The results suggest that cadaverine levels are associated with oral malodor, and that this association may be independent of VSC.

Study on the Organoleptic Intensity Scale for Measuring Oral Malodor

The 0–5 organoleptic scale is used widely in breath research and in trials to measure the efficacy of anti-odor agents. However, the precise relationship between odor scores and gas concentrations of target odorants is unknown. The purpose of this study was to relate mean organoleptic scores from odor judges (n = 7) for pure odorants (n = 8) representative of those found in oral malodor. Judges used a common 0–5 scale to report the odor intensity of sample sets in random order of concentration. Regression analysis of data showed that odor score was proportional to the log concentration of odorant, and comparison of slopes showed H2S to be the most significant in terms of odor power. Detection thresholds (mol.dm−3) were: Skatole (7.2 × 10−13) < methylmercaptan (1.0 × 10−11) < trimethylamine (1.8 × 10−11) < isovalerate (1.8 × 10−11) < butyrate (2.3 × 10−10) < hydrogen sulphide (6.4 × 10−10) < putrescine (9.1 × 10−10) < dimethyl disulphide (5.9 × 10−8). The study demonstrates the exponential nature of the olfactory response and shows that any single compound’s contribution to malodor depends on odor power and threshold in addition to concentration.

Correlation between the BANA Test and Oral Malodor Parameters

The purpose of the present investigation was to test the association between the BANA test (Perioscan®, Oral-B), and oral malodor parameters. The subject population consisted of 52 Israeli adults, 43 of whom complained of oral malodor. Oral malodor measurements consisted of peak and steady-state volatile sulphide measurement by a portable sulphide monitor (Interscan Corp., model 1170), as well as organoleptic measurements of malodor from whole mouth, tongue, and saliva. Samples for the BANA test were obtained from four loci (shallow pocket, deep pocket, tongue dorsum, saliva); results were scored as negative (0), weak (1), or strong (2). BANA scores were significantly associated with odor-judge ratings, with the highest association obtained when BANA saliva scores and odor-judge saliva assessment were compared (r = 0.500; p < 0.001). BANA tests from the different loci were not significantly associated with sulphide monitor levels. Stepwise multiple-regression analysis of odor-judge measurements in terms of sulphide levels and average BANA scores showed that both log peak sulphide levels as well as BANA scores were significantly factored into the equations, yielding, in all cases, highly significant correlations (multiple r = 0.57, 0.50, and 0.59, respectively, with significance levels of 0.0001, 0.001, and < 0.0001, for whole mouth, tongue, and saliva malodor, respectively). The results suggest that the BANA scores are associated with a component of oral malodor which is independent of volatile sulphide measurements and suggest its use as an adjunct test to volatile sulphide measurement.

Basic and Applied Aspects of Microbial Adhesion at the Hydrocarbon: Water Interface

Microbial hydrophobicity has been studied since 1924. During the last decade, various techniques have become available for measuring hydrophobic surface properties of microbial cells. This has led to a surge in investigations suggesting a role for hydrophobicity in adhesion of bacteria to an array of surfaces (oral surfaces, mineral particles, fatty meat, epithelial cells, phagocytes, biomaterials), partitioning at interfaces, as well as gliding mobility. The present manuscript comprises a critical, chronological look at the origins of microbial hydrophobicity research, its development, origins, and applications. Emphasis is placed on microbial adhesion to hydrocarbons, a technique with which the author has the most experience and research interest.

Isolation of Enterobacteriaceae from the Mouth and Potential Association with Malodor

Bad breath is a common phenomenon, usually the result of bacterial metabolism in the oral cavity. It is generally accepted that Gram-negative bacteria are responsible for this problem, largely through degradation of proteinaceous substances. In initial experiments, screening of malodorous isolates following outgrowth of samples obtained from saliva, periodontal pockets, and the tongue dorsum yielded enterobacterial isolates. Clinical studies were conducted to examine the prevalence of such bacteria in four different populations: orthodontic patients, malodor clinic patients, complete-denture wearers, and a healthy young population. The prevalence of Enterobacteriaceae in the oral cavities of the denture-wearing population was very high (48.0%) as compared with the other groups: 27.1% in the malodor clinic patients, 16.4% in the normal population, and 13% among orthodontic patients. Isolates of Klebsiella and Enterobacter emitted foul odors in vitro which resembled bad breath, with concomitant production of volatile sulfides and cadaverine, both compounds related to bad breath. When incubated on a sterile denture, enterobacterial isolates produced typical denture foul odor. Isolates exhibited cell-surface hydrophobic properties when tested for adhesion to acryl and aggregation with ammonium sulphate. The results, taken together, suggest that Klebsiella and related Enterobacteriaceae may play a role in denture malodor.

Self-estimation of Oral Malodor

Bad breath (halitosis, oral malodor) is a common condition, usually the result of microbial putrefaction within the oral cavity. Often, people suffering from bad breath remain unaware of it, whereas others remain convinced that they suffer from foul oral malodor, although there is no evidence for such. The purpose of the present investigation was to determine whether objective self-measurement of oral malodors is possible. Each of 52 volunteers was asked to sample the odor from his/her mouth, tongue, and saliva. Results were compared with (i) self-assessments prior to (preconception) and following (post-measurement) self-measurements; (ii) odor judge scores; (iii) dental measurements (plaque index, gingival index, and probing depth); (iv) volatile sulphide levels; (v) salivary cadaverine levels; and (vi) intra-oral trypsin-like activity. Among the self-measurements, only saliva self-scores yielded significant correlations with objective parameters. Despite the partial objectivity of saliva self-estimates, subsequent post-measurement self-assessments failed to correlate with objective parameters. The results suggest that (i) preconceived notions confound the ability to score ones own oral malodors in an objective fashion; and (ii) partial objectivity can be obtained in the case of saliva self-measurement, presumably because the stimulus is removed from the body proper.

Cell-surface hydrophobicity of adherent oral bacteria

Adherent bacteria were released from the surfaces of four freshly extracted teeth by mild sonic oscillation, and screened for cell-surface hydrophobicity on the basis of their ability to adhere to hexadecane. Of the 103 tooth isolates examined, 82 adhered to the test hydrocarbon. Hydrophobic bacteria could similarly be isolated from the stainless steel dental matrix bands following brief incubation in the mouth of a volunteer; 30 of 52 isolates examined adhered to hexadecane. Among those strains which adhered to hexadecane, streptococci were the most frequent type isolated. Various other morphological types were also observed, including cocci, bacilli, coryneforms, and filamentous bacteria. The high overall proportion of hydrophobic bacteria found in this study (72%) suggests that cell-surface hydrophobicity may play a role in adherence of certain oral species to the tooth surface.

Bacterial adherence at the hydrocarbon-water interface

Large differences were observed in the ability of eight Acinetobacter calcoaceticus strains to adhere to liquid hydrocarbon. Four strains exhibited extremely high affinity for hexadecane, two strains were moderately adherent and two other strains exhibited low affinity for the test hydrocarbon. Adherence of A. calcoaceticus RAG-1 to hexadecane was a function of culture age and growth conditions. In general, late exponential and stationary phase cells were more adherent than exponential phase cells. A. calcoaceticus RAG-1 cells cultured on hexadecane in flasks were adherent throughout growth. In contrast, a hydrocarbon-degrading strain of Pseudomonas aeruginosa adhered poorly to hydrocarbons, even following growth on hexadecane. Adherence of bacteria to hydrocarbons is discussed in terms of the bacterial cell surface, microbial growth on oil, and microbial contamination of surfaces.