The impact of staff and service user gender on staff responses towards adults with intellectual disabilities who display aggressive behaviour.

BACKGROUND: The impact of staff and service user gender on responses of staff in intellectual disability (ID) services is poorly understood. The present study set out to assess the role of gender in influencing staff emotions, attributions and behavioural intentions in response to aggression displayed by adults with ID. METHOD: A new scale measuring staff behavioural intentions was developed. A two × two (staff gender × service user gender) between subjects design was used to compare the responses of day and residential support staff to physical aggression by a hypothetical service user. In response to a vignette depicting a service user with ID assaulting a member of staff, 160 respondents completed measures of affective responses, causal attributions and behavioural intentions while imagining themselves as the target of the service user's assault. RESULTS: Female participants reported feeling more fear/anxiety, more depression/anger and less confident/relaxed than male participants. The longer staff had worked with people with ID, the more likely they were to favour safety-focused behaviours. More confident female participants were less likely to favour safety-focused behaviours, but confidence had no effect on male participants' endorsement of these behaviours. Increased confidence in both was associated with lower agreement of safety-focused behaviours in relation to the female vignette, regardless of participant gender. The more control women believed the service user had over their behaviour, the more likely they were to choose safety-focused behaviours. Punitive behaviours were favoured more in response to the male rather than the female service user. Punitive behaviours were also favoured more by more junior staff and by participants who expected feeling more depressed/angry in response to the vignettes. CONCLUSIONS: Both staff and service user gender influenced staff responses to aggression, yet the latter played a smaller role than expected. The role of gender in staff-service user interactions should be the focus of further research and should be considered in service delivery.

Generation of indole/skatole during malodor formation in the salivary sediment model system and initial examination of the oral bacteria involved.

Gram negative anaerobic microbial degradation of proteins, peptides and amino acids in saliva leads to production of oral malodor. Volatile sulfur compounds (VSCs) from cysteine and indole/skatole (I/S) from tryptophan are two major components of breath odor. In this study, salivary mixed bacteria and oral pure cultures were compared for their ability to produce odor from cysteine, tryptophan and salivary supernatant. The VSC malodor inhibitor, zinc, was used to help identify the malodor processes involved. Salivary sediment and salivary supernatant were both obtained from wax-stimulated whole saliva. Gram positive (13) and Gram negative (12) oral pure cultures of common salivary bacteria were each grown in appropriate media and harvested. Incubation mixtures were prepared with salivary sediment at 16.7% (v/v) or bacterial pure cultures at 8.3% (v/v). Cysteine or tryptophan at 6 mM or salivary supernatant at 33.3% (v/v) was added. When included, zinc as ZnCl(2) was added at 6 mM. All incubations were carried out for 24 h at 37 °C. Odor generation was assessed organoleptically (0-4 severity scale); VSC was determined with a Halimeter (Interscan Corp., Chatsworth, CA) and I/S was determined using Kovac's colorimetric method. Organoleptic odor levels produced by salivary sediment mixed bacteria with the three substrates tested were comparable, though tryptophan and cysteine generated distinct and characteristic odors. With cysteine and supernatant, rapid and substantial VSC was generated; with tryptophan no such VSC formation was observed. Zinc inhibited VSC generation from cysteine and from salivary supernatant but had no effect on I/S from tryptophan. Surprisingly though, zinc which had no effect on I/S production from free tryptophan, reduced I/S production from supernatant. Of the 12 Gram negative bacteria, 75% produced I/S (mean 3.1 ± 1.5 SEM mg ml(-1)); most was generated by Porphyromonas intermedia, Porphyromonas gingivalis and Fusobacterium nucleatum. Gram positive pure cultures produced none. Comparable levels of organoleptic odor were produced by Porphyromonas gingivalis from tryptophan and cysteine. Malodor produced orally is complex because multiple microbial types, substrates, metabolic pathways and hence end products are involved. Zinc clearly inhibited I/S production in salivary supernatant, possibly by interfering with the release of tryptophan from peptides/proteins.

H(2)S generation and E(h) reduction in cysteine challenge testing as a means of determining the potential of test products and treatments for inhibiting oral malodor.

Bacterial degradation of the sulfur-containing amino acid, cysteine, involves two biochemical processes that contribute significantly to oral malodor generation. The first is production of hydrogen sulfide, a major component and common indicator of oral malodor formation. The second is generation of the sulfhydryl anion, HS(-), an anion that is central to the lowering of the oxidation-reduction potential (E(h)). A reduced E(h) is fundamental to the growth and metabolism of the oral Gram negative anaerobic bacteria. These microorganisms are responsible for oral putrefaction, a process primary to both oral malodor generation and gingivitis-periodontitis development. One purpose of this paper is to report on the testing of a number of anti-malodor treatments and products for their effects on H(2)S formation and E(h) reduction, two processes that occur rapidly and do so simultaneously after the oral bacteria are challenged with cysteine. A second is to report on aspects of cysteine challenge testing in the development of an anti-malodor product composed of ZnCl(2) and sodium chlorite that simultaneously inhibits both H(2)S formation and E(h) reduction and effectively inhibits oral malodor.

A mixed-bacteria ecological approach to understanding the role of the oral bacteria in dental caries causation: an alternative to Streptococcus mutans and the specific-plaque hypothesis.

For more than 100 years, investigators have tried to identify the bacteria responsible for dental caries formation and to determine whether their role is one of specificity. Frequent association of Lactobacillus acidophilus and Streptococcus mutans with caries activity gave credence to their being specific cariogens. However, dental caries occurrence in their absence, and the presence of other bacteria able to produce substantial amounts of acid from fermentable carbohydrate, provided arguments for non-specificity. In the 1940s, Stephan found that the mixed bacteria in dental plaque produced a rapid drop in pH following a sugar rinse and a slow pH return toward baseline. This response became a cornerstone of plaque and mixed-bacterial involvement in dental caries causation when Stephan showed that the pH decrease was inversely and clearly related to caries activity. Detailed examination of the pH (acid-base) metabolisms of oral pure cultures, dental plaque, and salivary sediment identified the main bacteria and metabolic processes responsible for the pH metabolism of dental plaque. It was discovered that this metabolism in different individuals, in plaque in different dentition locations within individuals, and in individuals of different levels of caries activity could be described in terms of a relatively small number of acid-base metabolic processes. This led to an overall bacterial metabolic vector concept for dental plaque, and helped unravel the bacterial involvement in the degradation of the carbohydrate and nitrogenous substrates that produce the acids and alkali that affect the pH and favor and inhibit dental caries production, respectively. A central role of oral arginolytic and non-arginolytic acidogens in the production of the Stephan pH curve was discovered. The non-arginolytics could produce only the pH fall part of this curve, whereas the arginolytics could produce both the fall and the rise. The net result of the latter was a less acidic Stephan pH curve. Both kinds of bacteria are numerous in dental plaque. By varying their ratios, we were easily able to produce Stephan pH curves indicative of different levels of caries activity. This and substantial related metabolic and microbial data indicated that it is the proportions and numbers of acid-base-producing bacteria that are at the core of dental caries activity. The elimination of S. mutans, as with a vaccine, was considered to have little chance of success in preventing dental caries in humans, since, in most cases, this would simply make more room for one or more of the many acidogens remaining. An understanding of mixed-bacterial metabolism, knowledge of how to manipulate and work with mixed bacteria, and the use of a bacterial metabolic vector approach as described in this article have led to (1) a more ecological focus for dealing with dental caries, and (2) new means of developing and evaluating anti-caries agents directed toward microbial mixtures that counter excess acid accumulation and tooth demineralization.

Cysteine challenge testing: a powerful tool for examining oral malodour processes and treatments in vivo.

Gram-negative oral bacteria rapidly produce the odorant hydrogen sulphide from cysteine. It provides a major part of the oral malodour bouquet while causing a corresponding decrease in the oxidation-reduction potential (Eh). A low Eh favours oral putrefaction and malodour occurrence. Challenge testing with cysteine (5ml of 6mM for 30 seconds) enabled evaluation of: the contribution of tongue and teeth bacteria to overall oral malodour; the effectiveness of tongue and tooth brushing, tooth scraping, gum chewing and mouthrinsing with different agents in reducing oral malodour. Successive cysteine challenge tests for 20 minute periods at selected times in a seven hour experiment were effective for assessing the magnitude and duration of an agent's effectiveness. Brushing the teeth reduced malodour modestly. So did tongue scraping and gum chewing. In contrast, brushing the tongue dorsum, especially the posterior half was remarkably effective, which confirmed it as a major site of oral malodour contribution. Rinses containing various actives showed wide variation in effectiveness. The experiments demonstrated that cysteine challenge testing is potentially a aluable tool for assessing the ability of the oral bacteria to produce malodour and for assessing agents designed to inhibit such production.

Role of saliva in oral dryness, oral feel and oral malodour.

Patients who believe they have oral malodour often have a dry mouth condition instead. Here we have examined its relation to oral malodour, real or perceived. A direct relationship between the thickness of the film of residual saliva on mucosal surfaces throughout the mouth and perception of a dry mouth was observed. On the hard palate, the thickness of this film proved to be diagnostic for a dry mouth and corresponded to lower resting saliva flow and pH levels (P< 0.001). Intra-muscular administration of the anti-sialogogue, Robinul, accurately produced the dry mouth condition. Using a sulphide monitor, loss of volatile sulphur compounds into mouth air progressively occurred as the mouth became drier. Mouth pH and Eh on the dorsum of the tongue correspondingly fell. Mouth breathing led to tongue and palate moisture loss thus enabling escape of malodour volatiles into mouth air. Measurement of oral dryness should make it possible to differentiate genuine malodour from dry mouth related pseudo-malodour subjects, and in turn, the latter from patients that are halitophobic. This should facilitate identification of such patients and avoid error in their clinical management.

The effect of ammonium glycopyrrolate (Robinul)-induced xerostomia on oral mucosal wetness and flow of gingival crevicular fluid in humans.

The antisialogogue, ammonium glycopyrrolate (Robinul), was used to reduce the salivary flow rate in healthy individuals with normal salivary function to determine whether the dry-mouth symptoms and reduced amounts and patterns of oral mucosal wetness found previously in hyposalivators could be induced by this means. After baseline measurements, the drug was given to 10 healthy volunteers and their resting whole-saliva flow rate was measured at 0, 15, 60, 105 and 150 min thereafter. At the same times, the thickness of the layer of residual mucosal saliva (a measure of residual mucosal wetness) at each of 22 intraoral sites was also determined. The saliva flow rate fell from a mean of 0.45 +/- 0.07 ml/min to a mean of 0.05 +/- 0.02 ml/mm by 1 h and slowly thereafter to a mean of 0.02 +/- 0.01 to 0.03 +/- 0.01 ml/min for the remainder of the experiment. Onset of dryness symptoms was observed approx. 30 min after giving the drug. Simultaneously, the residual saliva at each of the 22 sites teted decreased to a thickness level previously found in patients with hyposalivation and who exhibited an intense feeling of dry mouth. Despite these decreases in thickness, the pattern of residual mucosal wetness throughout the mouth remained more or less unchanged. As in earlier studies, wetness was least on the hard palate and highest on the posterior dorsum of the tongue. An altered taste of the residual saliva in the mouth and an increased feeling of roughness as the tongue was passed over labial and buccal mucosal surfaces were noted. The amount of gingival crevicular fluid (GCF) in 12 gingival sites in each of the participants was also measured. Unlike the reduction in salivary flow, changes in GCF over the 150 min of the study were negligible. From this it was concluded that GCF could contribute much more to the oral fluids in dry-mouth than in normal individuals, especially when there is greater gingival inflammation.

Modeling of the oral malodor system and methods of analysis.

Bacterial putrefaction is the central metabolic process involved in oral malodor and can easily be modeled in the salivary sediment system developed from centrifuged whole saliva. Methods used in this system for examining malodor have included measurement of (1) head space (gaseous-phase) and liquid-phase odors, organoleptically; (2) volatile sulfur compounds, by means of an electrochemical sensory instrument; (3) pH, Po2, and oxidation-reduction potential with appropriate respective electrodes; (4) the malodorous compounds indole and skatole, colorimetrically; (5) substrate levels and their effects; and (6) bacterial numbers and types. The simplicity of the system permits other analyses to be easily added, if needed, and the influence of factors and agents that affect oral malodor to be assessed. Addition of odorigenic or non-odorigenic pure cultures to the mixed bacterial flora of the system enables modification of the microflora composition and high- and low-odor-production microflora to be simulated and compared. Modeling validity has been enhanced by the use of complementary in vivo methods, such as a method used to measure the ability or potential of an oral microbial flora to produce malodor. The method involves in vivo challenge testing with cysteine, an amino acid, and measuring the hydrogen sulfide produced. Oral malodor is a multifactorial condition and models enable its systematic study and the quantitative testing of antimalodor agents.

Oral mucosal wetness in hypo- and normosalivators.

After a person swallows, a film of residual saliva covers the oral hard- and soft-tissue surfaces. Here, the thickness of this film was measured at 11 selected mucosal surfaces on each side of the mouth (22 sites total) in two groups of dry-mouth and one group of normal individuals. Each group contained 25 individuals; one of the dry-mouth groups had resting flow rates < or = 0.1 ml/min while the other and the normal had flow rates above that. Residual saliva thickness was determined by placing frying-pan-shaped filter-paper strips (Sialopaper) against the mucosa at each site for 5 s and measuring the saliva volume collected with a modified Periotron 6000 micro-moisture meter; the thickness was then calculated by dividing the collected saliva volume by the strip area. The two groups with dry-mouth symptoms had mean resting (unstimulated) saliva flow rates of 0.04 and 0.19 ml/min and mean mucosal saliva thicknesses of 22.4 and 27.8 microns, respectively. The control group had a higher mean saliva flow rate of 0.39 ml/min and mucosal saliva thickness of 41.8 microns. As was observed in a previous study on normosalivators, the various sites had a characteristic pattern of wetness, with the hard palate and lips the least moist regions. In this study, these observations, were also true in the two dry-mouth groups. Lower resting saliva flow rates were associated with lower mucosal thickness of saliva and with dryness symptoms becoming evident when hyposalivation was below about 0.1-0.2 ml/min. The characteristic pattern of mucosal wetness was not affected by saliva flow rate. As saliva readily collects in the floor of the mouth and is then spread over other mucosal surfaces upon swallowing, it was suggested that hyposalivation could also lead to the dryness symptoms because there was not enough saliva to cover the various oral surfaces, especially the palate and the lips. In this regard, a critical level of moisture was proposed as necessary to protect vulnerable mucosal surfaces from becoming dry. Lower resting saliva flow rates and correspondingly lower mucosal wetness were also associated with a more acidic salivary pH, which was shown earlier to be associated with lower dental plaque pH.

Use of N-phenylmethazonium methosulphate oxidation of NADH in the quantification of oxygen uptake by oral bacteria under open-system conditions.

Technically, open systems are more suited than closed systems for the measurement of oxygen uptake by bacteria present at high cell densities as in dental plaque. Moreover, measurements are easier to perform and can be done faster and continuously. However, quantifications is more difficult and, except for steady-state conditions, has been semiquantitative. The stoichiometric oxidation of NADH by N-phenylmethazonium methosulphate (PMS) is a reaction used here to develop a formula that overcomes this problem and makes it possible to relate quantitatively the pO2 measured easily with an oxygen electrode to the amount of oxygen utilized by respiring bacteria provided with a given amount of substrate. The approach and formula consist of the summing of (i) the oxygen decrease observed during the period of bacterial oxygen consumption and (ii) the oxygen simultaneously entering from the atmosphere. To quantify the entry component, the rate of oxygen diffusion into the mixture needed to be determined: this was done by reducing or exhausting the oxygen content of the medium in various ways and determining the rate constant of atmospheric oxygen entry. The relation between the logarithm of the oxygen concentration (determined from pO2 values using the PMS-NADH reaction) and point of time in the oxygen resaturation process proved to be linear. This enabled calculation of a diffusion rate constant, k, for use in the oxygen utilization formula. The validity of this method for quantification of oxygen use was tested by comparing oxygen consumption determined from the pO2 tracing and the derived formula to the oxygen consumed when fixed amounts of NADH are oxidized by PMS. When oxygen uptake/substrate utilization molar ratios were calculated for each of several NADH concentrations, the resulting values were almost identical. The method proved reliable over most of the oxygen concentration range possible in this system.

Stoichiometry of oxygen consumption and sugar, organic acid and amino acid utilization in salivary sediment and pure cultures of oral bacteria.

In each of 23 numerically or metabolically significant oral micro-organisms, and in each of the salivary sediments of 10 humans, oxygen uptake was determined quantitatively with various sugar and organic and amino acid substrates. With relatively few exceptions, the salivary sediments rapidly consumed oxygen with the array of substrates (23) tested. On the other hand, the individual pure cultures oxidized fewer substrates and did so selectively from this menu. The observation that the Gram-positive bacteria readily used oxygen when sugar substrates were provided, but were unable to use oxygen with all but one of the organic and none of the amino acids was significant. The Gram-negative bacteria, in contrast, used oxygen poorly with the sugars but most readily with many of the organic and amino acids, was significant. Only two of the Gram-positive but most of the Gram-negative micro-organisms tested showed oxygen uptake with L(+)-lactate; the Gram-negative bacteria were also active with D(-)-lactate, formate and succinate. Propionate was also tested and showed oxygen uptake only with the Gram-negative micro-organism, Neisseria subflava; acetate showed none or almost none with all of the examined bacteria. Where oxygen consumption occurred with the various pure or mixed cultures and substrates tested, the quantities of oxygen consumed were less than theoretically possible. For example, they ranged on average in the sediment results from 1.78 mumol oxygen per mumol of L(+)-lactate catabolized to 5.17 mumol oxygen per mumol of lactose. This was consistent with substrate oxidation by the oral bacteria being less than complete as in aerobic glycolysis, and with compounds other than water and carbon dioxide (such as acetate) being prominent amongst the end-products produced. The pure-culture oxygen data and other reports from this laboratory have made it possible to propose a speculative scheme as to which bacterial species might be involved in the various metabolic pathways used when different substrates are catabolized and oxidized by the mixed bacteria in salivary sediment or dental plaque. Also, it made it possible to suggest which bacteria and substrates are likely to be involved in the oxygen depletion that enables plaque to achieve anaerobiosis.

Use of a paper-strip absorption method to measure the depth and volume of saliva retained in embrasures and occlusal fussae of the human dentition.

Embrasures and occlusal fossae are regions of the human dentition that readily retain saliva, as well as dental plaque and dietary substrates. In this study, a wax filling and weighing technique was used to determine the volumes of these irregularly shaped spaces, and a paper-strip absorption method was developed for measuring the thickness and amounts of saliva therein. The volumes were measured on dental stone models prepared from alginate impressions of the maxillary arches of each of eight individuals and on an acrylic maxillary denture representative of the shape and alignment of normal-sized adult teeth. Embrasure volumes in the two cases were similar and ranged between 4.0 and 16.4 microliters for the individual participants, and between 4.8 and 14.9 microliters for the denture. Occlusal fossae volumes of posterior teeth determined on the denture ranged between 6.0 and 9.8 microliters. The paper-strip absorption method for the thickness or amount of saliva in embrasures or fossae consisted of the absorption of the saliva in these sites on to filter-paper strips and the measurement of the collected volumes electronically with a Periotron 6000 micro-moisture meter. Residual saliva for the embrasures between the two central incisors and the second premolar and first molar ranged between 0.12 and 0.56 with means of 0.28 and 0.37 microliter, respectively, for the same eight participants. Corresponding saliva Vmax volumes were 0.48 and 0.63 microliter, respectively. Further paper strip absorption measurements of saliva in embrasures and fossae showed a linear relation between Periopaper dipstick values and embrasure saliva volumes when these were less than 1 microliter. This range includes most residual saliva volumes normally found in these sites in vivo. For volumes of saliva greater than 1 microliter, small increments in dipstick values in embrasures corresponded to very large changes in total embrasure volumes, which reflects their exponential widening beyond about that point. For saliva thickness measurements, a blue food dye was used to construct a standard curve relating depth of saliva in embrasures and fossae (measured with an electronic micrometer) to Periopaper dipstick scores (measured with the Periotron). The relation was linear for both sites, with r values of 0.98 and 0.99, respectively (p < 0.001 for each), and was used to convert extensive in vivo depth measurements of embrasures and fossae determined in microlitres by the dipstick method in an earlier study to thicknesses in millimetres here. In the earlier study, residual saliva on oral mucosal and smooth dentition surfaces was quantified by the blotting method. Together with the method developed here, it should now be possible to measure the saliva, residual or otherwise, on all oral surfaces whether uniform or irregular in shape.

Measurement and comparison of the residual saliva on various oral mucosal and dentition surfaces in humans.

Using a paper-strip absorption method, the amounts of residual saliva on 20 soft-tissue sites in different regions of the mouths of 20 individuals were surveyed once in the morning after a 12-h fast and again approx. 1-2 h after lunch. After swallowing, saliva at each site was immediately collected on filter-paper strips in a dipstick fashion for 5 s and the volumes were measured electronically with a Periotron micro-moisture meter. A clear pattern of wetness was evident and was almost identical for fasting and postprandial determinations. The hard palate and labial mucosa were covered with the least residual saliva; the floor of the mouth and back of the tongue were the wettest. In the same 20 participants, the amounts of residual saliva on various dentition sites were next measured and, as expected, much higher residual amounts were found in approximal embrasures and occlusal fossae than on adjacent facial or lingual smooth areas. Molars gave higher values than premolar and incisor embrasures. To relate residual saliva dipstick volumes to saliva thickness values, filter-paper strips were applied flat against the same mucosal or dentition surfaces in 10 of the participants, and the volume of the saliva absorbed was measured electronically as before. As the areas of the strips used were known, saliva thicknesses could be calculated. These ranged from 0.01 mm on the hard palate to 0.07 mm on the posterior of the dorsum of the tongue. For the incisor teeth, the calculated residual saliva thickness determined in the same way was about 0.01-0.02 mm. Blotting values plotted against dipstick values for oral sites where blotting could be readily performed showed a linear relation, which could be used as a standard curve to enable the easily done dipstick measurements in microlitres to be converted to saliva thicknesses in millimeters. As blotting could not be done in embrasures and occlusal fossae, this paper-strip absorption method was unsuitable for similar quantification of residual saliva in these sites but was done in another way described elsewhere. Overall, the results indicated that variations in dental morphology, and in the saliva secreted and available to the different oral regions, are the basic factors responsible for the wide variations in residual amounts of saliva seen on the diverse hard- and soft-tissue surfaces of human mouths. Also, finding that the hard palate and inner lips are covered by very thin films of residual saliva suggested that only a small reduction in their quantity would be needed to trigger the dry mouth sensation in hyposalivators.

A comparative study of glucose and galactose uptake in pure cultures of human oral bacteria, salivary sediment and dental plaque.

The ability to utilize glucose and the weaker sugar acidogen, galactose, was surveyed in salivary sediment, pooled dental plaque, and in pure cultures of the bacteria that numerically comprise most of the bacteria in these mixed microbial systems. Except for a veillonella isolate, which showed no uptake of either sugar, glucose was utilized more rapidly than galactose by the 27 pure cultures tested and by both sediment and plaque. This sugar difference was also seen for two other measures of glycolysis, formation of acid and previously studied ability to produce an acidic pH. Rates of uptake of the two sugars by individual pure cultures varied considerably. Generally, the Gram-positive bacteria utilized glucose and galactose at rates similar to those seen with salivary sediment and dental plaque, whereas the Gram-negative cultures tested showed much slower uptakes. Bacteria previously identified as arginolytic had lower glucose and galactose uptake rates than similar non-arginolytic micro-organisms. This, together with the ability to produce base from arginine, would explain their tendency to produce a less acidic pH. In pure culture mixtures, uptakes were generally predictable and indicated an averaging effect. When the microbial compositions of salivary sediment or dental plaque were altered by mixing with pure cultures of high glucolytic activity, such as many of the Gram-positives, glucose uptake was enhanced. The opposite was observed when the less glucolytic Gram-negative bacteria were similarly incorporated. As well as determining the glucose and galactose uptake rates of the various bacteria that collectively comprise the bulk of the salivary sediment and supragingival plaque microfloras, this study has shown how variation in microbial composition affects sugar uptake rates and has indicated how microbial composition could be manipulated to produce dental plaques with different capacities to ferment sugars and presumably different cariogenicities.

Bacteria in human mouths involved in the production and utilization of hydrogen peroxide.

Earlier studies have demonstrated that pure cultures of oral streptococci produce hydrogen peroxide but none has found any free peroxide in dental plaque or salivary sediment despite streptococci being major components of their mixed bacterial populations. The absence of peroxide in plaque and sediment could be due to the dominance of its destruction over its formation by bacterial constituents. To identify which of the oral bacteria might be involved in such a possibility, pure cultures of 27 different oral bacteria were surveyed (as well as dental plaque and sediment) for their peroxide-forming and peroxide-removing capabilities. Peroxide production was measured for each of the pure cultures by incubation with glucose at low and high substrate concentrations (2.8 and 28.0 mM) for 4 h and with the pH kept at 7.0 by a pH-stat. Removal of hydrogen peroxide was assessed in similar experiments where peroxide at 0, 29.4, 147.2 or 294.4 mM [0, 0.1, 0.5 and 1% (w/v)] replaced the glucose. Hydrogen peroxide formation was seen with only three of the bacteria tested, Streptococcus sanguis I and II (sanguis and oralis), and Strep. mitior (mitis biotype I); levels of hydrogen peroxide between 2.2 and 9.8 mM were produced when these micro-organisms were grown aerobically and 1.1 and 3.9 mM when grown anaerobically. Earlier reports indicate that such levels were usually sufficient to inhibit the growth of many plaque bacteria. The amounts formed were similar at the two glucose levels tested, suggesting that maximum peroxide production is reached at low glucose concentration. None of the three peroxide-producing organisms was able to utilize hydrogen peroxide but five of the other 24 tested, Neisseria sicca, Haemophilus segnis, H. parainfluenzae, Actinomyces viscosus and Staphylococcus epidermidis, could readily do so, as could the mixed bacteria in salivary sediment and dental plaque, both of which contain relatively high numbers of these peroxide-utilizing micro-organisms. The ability of the bacteria in plaque and sediment to degrade hydrogen peroxide was considerable and extremely rapid; peroxide removal and usually complete within the first 15 min of the incubation even when its initial level was as high as 294.4 mM. This almost overwhelming ability to remove peroxide was confirmed when peroxide-producing and -using cultures were mixed and when each of eight salivary sediments was incubated with glucose and with peroxide at concentrations up to 294.4 mM. In the glucose incubations, no hydrogen peroxide was observed, indicating dominance of microbial peroxide removers over hydrogen peroxide producers.(ABSTRACT TRUNCATED AT 400 WORDS)

Measurement of tooth hypersensitivity and oral factors involved in its development.

The various methods of measurement of dentinal hypersensitivity are based upon the types of stimuli used to elicit a pain response in teeth, which include thermal, tactile, evaporative, electrical and osmotic. Pulpal inflammation in its early stages reduce the threshold of pain response to these stimuli but electrical stimulation may make it possible to assess the possible contribution of such inflammation to sensitivity determinations. Although the magnitude of each stimulus is quantifiable, patient response is subjective, which necessarily makes measurements of dentinal sensitivity semisubjective. Various methods of testing dentinal sensitivity are discussed, along with their advantages and disadvantages. The teeth most suited for measurement in clinical studies are the canines and premolars. This is because approx. 80% of the sensitivity lesions are associated with these teeth, which have similar thicknesses of root dentine. Data from several studies involving the same subjects indicate that individual measurements readily return to baseline and that the commonly seen placebo effect is probably due to some as yet unidentified factor in desensitizing formulations. Possible roles of salivary and plaque environmental factors in the development of dentinal sensitivity are discussed, as well as methods for their measurement.

Design and statistical aspects of the management of clinical trials to assess antihypersensitivity product efficacy.

This paper discusses the design of clinical trials for testing the efficacy of therapeutic products for hypersensitive teeth with emphasis on statistical considerations. The preparation of a proper protocol is essential to the successful outcome of any clinical study. Key considerations in this regard are the criteria for patient selection, the size of the sample, the method of stratification of subjects into various test and control groups, the methods to be used for assessing sensitivity, and the statistical treatment of the data generated. The importance of other factors such as the requirement for a quiet, relaxed atmosphere and allowing adequate time for the examiner to establish a rapport with the subject, and the need to comply with institutional review board regulations, are stressed.

Bruxism: aetiology, clinical signs and symptoms.

The aetiology of bruxism and therefore its management is poorly understood by dentists and their focus on a local dental cause has lead to much unnecessary irreversible dental treatment, with little impact on the incidence of bruxism. Clinical and neurophysiological evidence suggests that there is a strong link between bruxism and tooth wear in man and its counterpart in animals. In animals, keeping teeth sharp has importance for food retrieval and defense. In man, although this is no longer necessary, remnants of this mechanism remain as an inherited predisposition.