Gland size estimation and body mass index improve salivary flow rate assessment.
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Adult↗
Biomedical subjects
C Dawes
Publications and source records attributed to C Dawes.
Absorption of urea through the oral mucosa and estimation of the percentage of secreted whole saliva inadvertently swallowed during saliva collection.
OBJECTIVE: To determine whether some of the urea added to certain chewing gums may be absorbed through the oral mucosa and whether some saliva is inadvertently swallowed during the collection of saliva elicited by the chewing of gum. DESIGN: On two occasions, 10 experienced saliva collectors made a 5 min collection of unstimulated whole saliva and then chewed gum for 10 min and during this time collected their saliva. On one occasion, they chewed one tablet of gum containing 0.5 mg of Phenol Red, a non-absorbable substance, and one tablet of a gum containing 27.3 mg of urea. On another occasion, they chewed two tablets of the Phenol Red gum. Their saliva and the chewed gum were assayed for their Phenol Red and urea contents and the totals calculated. Since saliva normally contains urea, the recovery of urea was calculated as the difference between the amounts recovered in the two collection sessions. RESULTS: The mean recovery of Phenol Red was 96.7%, but in three participants the amount recovered was less than the 95% confidence limits for assay error. The mean recovery of urea was 85.7% and in nine of the 10 participants, the amount recovered was less than the confidence limits for assay error. In all participants, the percentage urea recovery was less than that of Phenol Red. CONCLUSION: The results showed: (1) that Phenol Red appears to be a useful, non-absorbed marker for studies of drug absorption through the oral mucosa, (2) that when the salivary urea concentration is higher than that in plasma, urea may be absorbed through the oral mucosa, (3) that even experienced saliva collectors may inadvertently swallow some of the saliva they produce. This latter finding has implications for all clinical studies of saliva.
Absorption↗
A circannual rhythm in unstimulated salivary flow rate when the ambient temperature varies by only about 2 degrees C.
OBJECTIVE: To determine whether a circannual rhythm in the flow rate of unstimulated whole saliva could be detected in persons living in a region of Sri Lanka where the average monthly temperature is virtually constant throughout the year. DESIGN: Forty-six medical students, 26 male and 20 female, in Peradeniya collected saliva on 12 occasions about once per month from September 19, 2003 to September 28, 2004. A least-squares sine wave of the form: F(t)=M+A x(2 pi t/tau+phi), in which F is the flow rate at time t (in days), M the mesor or rhythm-adjusted mean value, A the amplitude, tau the period (365 days) and phi the phase shift in radians, was fitted to the data. RESULTS: A statistically significant (p<0.05) circannual rhythm in salivary flow rate was detected with the following mean values and 95% confidence intervals: M=0.528 mL/min (0.514-0.543), A=0.0472 mL/min (0.0269--0.0674), phi=1.141 radians (0.704--1.578). The acrophase (peak value of the rhythm) was on October 14 (September 19--November 8). During the study, the average monthly temperature varied between 24.0 and 26.3 degrees C, with the peak temperature in April and minimum in December. CONCLUSION: Even though the monthly ambient temperature variation in Peradeniya was very small, the peak temperatures occurred at the times of the lowest salivary flow rates, suggesting that a small change in ambient temperature (about 2 degrees C) in a warm climate may be sufficient to influence the unstimulated salivary flow rate. In conclusion, for saliva studies, which extend over a prolonged period, it may be important to take into account the circannual rhythm in salivary flow rate.
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The unstimulated salivary flow rate after prolonged gum chewing.
OBJECTIVE: To determine whether, after a prolonged period of gum chewing, the unstimulated salivary flow rate falls below the unstimulated flow rate before gum chewing. DESIGN: Six males and six females each collected whole saliva at intervals for up to 105 min on two separate days. On one control day they collected unstimulated saliva over the -10 to 0 and 90 to 105 min periods. On the other day, they made the same collections of unstimulated saliva but, in addition, chewed two tablets of Wrigley's peppermint-flavoured gum over the 0-90 min period. The data on flow rates were subjected to repeated-measures ANOVA and Duncan tests. RESULTS: The unstimulated flow rates in the -10 to 0 and 90 to 105 min periods were not significantly different on the same day or between days and the values were all significantly less (P<0.05) than the stimulated flow rates, while gum was being chewed. CONCLUSION: This study provided no evidence that the unstimulated salivary flow rate is reduced after prolonged gum chewing. Patients who complain of mouth dryness after prolonged gum chewing may have become accustomed to the larger volume of saliva present in the mouth during the gum chewing.
Adult↗
The effects of prolonged gum chewing on salivary flow rate and composition.
OBJECTIVE: To determine the effect of gum chewing for 2 h on salivary flow rate and composition. DESIGN: Five male and five females each collected whole saliva at intervals over a 2 h period on three separate days, prior to which they collected unstimulated saliva for 5 min. For one 2 h session they continued to collect only unstimulated saliva while for the others one tablet of Wrigley's Extra peppermint- or fruit-flavoured (peach) gum was chewed continuously. Flow rates were calculated and the saliva was assayed for pH and for Na, K, Ca, Cl, inorganic P and protein concentrations. The data were subjected to repeated-measures ANOVA and Duncan tests. RESULTS: When only unstimulated saliva was collected, there was no significant change in salivary flow rate over the 2 h. With the chewing gums the flow rate increased initially and then, after 35-40 min, fell to similar plateau values which remained significantly higher than the initial unstimulated flow rate and significantly higher than the flow rate at the corresponding time intervals when only unstimulated saliva was collected. With both gums the salivary pH from 2 min to 2 h was significantly higher than that of unstimulated saliva. The changes in the salivary electrolyte and protein concentrations due to the flow rate increase elicited by the chewing gum were largely as expected from previous studies on parotid and submandibular saliva. CONCLUSION: During prolonged chewing gum use, both salivary flow rates and pH remained significantly above the values for unstimulated saliva.
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Estimates, from salivary analyses, of the turnover time of the oral mucosal epithelium in humans and the number of bacteria in an edentulous mouth.
The objectives were to obtain rough estimates of the number of bacteria in an edentulous mouth and the mean turnover time of the oral mucosa and the conditions under which the salivary phase in the mouth might act as a bacterial continuous culture system. The premise was that at steady state in vivo, the rates of loss of bacteria and epithelial cells in saliva must be equal to their rates of proliferation. Drooled saliva was collected from 17 subjects and the number of epithelial cells per millilitre was determined in a Coulter Counter. The numbers of adherent bacteria per epithelial cell were counted on cells stained with Toluidine Blue. For 10 subjects, salivary bacterial counts were obtained after saliva had been diluted in Reduced Transport Fluid and grown anaerobically on Blood Agar for 5 days. From the known surface areas of the oral mucosa and individual epithelial cells and the rate of loss of epithelial cells into saliva, the surface layer of epithelial cells was calculated to be replaced every 2.7h. From the calculated number of epithelial cells lining the oral mucosa, the number of bacteria per epithelial cell, and the rate of swallowing of the bacteria in saliva, the number of bacteria in an edentulous mouth was calculated to be about 1.58 x 10(9) and the mean time between bacterial cell divisions to be 1.38h. Given a residual volume of 0.8ml and a maximal bacterial division rate of 3h(-1), the salivary phase in the mouth could act as a continuous culture system for certain fast-growing bacteria only if the maximum flow rate were <0.04ml/min.
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The effects of gum chewing, four oral hygiene procedures, and two saliva collection techniques, on the output of bacteria into human whole saliva.
Six healthy dentate individuals collected a 5-min sample of unstimulated whole saliva (UWS) and dilutions were plated out on blood agar and grown anaerobically for 48 h. The output of bacteria into saliva (counts/min) was calculated as the product of counts/ml and ml/min. The individuals repeated the collections at intervals of up to 7 h after (1) rinsing with water, (2) eating a meal plus tooth brushing, (3) a thorough dental prophylaxis, or (4) tongue brushing and scraping. They also collected saliva at intervals while chewing gum for 20 min, as did 10 individuals who chewed gum for 2 h. The original six individuals also collected UWS under "drooling" (no oral movements) and "spitting" conditions. Six edentulous individuals not wearing their dentures collected UWS before and after a water rinse. With the four oral hygiene procedures, bacterial outputs fell initially and then rose again, but a repeated-measures ANOVA revealed no significant differences in the effects of the four procedures. Gum chewing caused initial marked increases in the outputs of bacterial and epithelial cells, but these fell with time and reached a plateau after about 10 min at outputs above those in UWS. Samples collected by spitting contained up to 14 times more bacteria than those collected by drooling. Bacterial output by edentulous individuals did not differ from that in those with teeth. It is concluded that bacteria from the teeth and gingival crevices normally make only a small contribution to those in saliva, that various oral hygiene procedures have similar effects on bacterial output into saliva, and that saliva collection conditions should be standardized and specified.
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Circadian and infradian rhythms in mood.
The aim of this study was to assess any variation in positive, negative and total affect recorded longitudinally; to compare the results with those from prior transverse or hybrid population studies, based on the same or a different method of mood rating; and to test for any association of mood with cardiovascular, hormonal and geophysical variables monitored concomitantly. The study approach was as follows. A clinically healthy 34-year-old man filled out the positive and negative affective scale (PANAS) questionnaire five times a day for 86 days. Systolic (S) and diastolic (D) blood pressure (BP) and heart rate (HR) were also measured automatically at 30-minute intervals with an ambulatory monitor from May 19 to June 29, 2000, while different endpoints of heart rate variability (HRV) were also determined at 5-minute intervals from beat-to-beat electrocardiogram (ECG) monitoring for 42 days between May 3 and June 14, 2000, with only short interruptions while the subject took a shower and changed ECG tapes. Saliva samples were collected at the times of mood ratings for one month for later determination of melatonin and cortisol concentrations. Intervals of 24 hours of the record of each variable displaced in increments of 24 hours were analyzed by chronobiologic serial section at a trial period of 24 hours to assess the circadian characteristics as they changed from one day to another. Estimates of the midline-estimating statistic of rhythm (MESOR) and circadian amplitude and acrophase obtained on consecutive days were correlated among variables to assess any associations. The findings were as follows. Overall, a circadian rhythm was demonstrated for all variables. A positive association was noteworthy between the circadian amplitude of negative affect and the MESOR of both SBP (r= 0.363; P= 0.029) and DBP (r= 0.389; P= 0.019), suggesting that BP is raised in the presence of large swings in negative affect. Needing further validation was a weak association between the MESOR of negative affect and the circadian amplitude of SBP (r= - 0.272; P = 0.108), suggesting a lowering of the circadian SBP amplitude in the presence of a strong negative affect. Of further interest was the lack of a statistically significant relation between positive and negative affect, not only in terms of the MESOR but also in terms of the circadian amplitude.
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Fluoride release from new light-cured orthodontic bonding agents.
The purpose of this study was to compare the rates of fluoride release with time from 1 nonfluoridated and 3 fluoride-containing orthodontic bonding materials in distilled water and artificial saliva. Materials tested were Assure (Reliance Orthodontic Products, Itasca, Ill), Fuji Ortho LC (GC, Tokyo, Japan), Python (TP Orthodontics, LaPorte, Ind), and Transbond XT (3M Dental Products, Monrovia, Calif). Ten specimens of each material type were stored in distilled water, and 10 of each type were stored in artificial saliva at 37 degrees C. Fluoride release was measured with an ion-specific electrode. Readings were taken periodically for a total time period of 6 months. At day 1, Assure released the most fluoride into distilled water (66.2 microg/cm(2)) and into artificial saliva (65.8 microg/cm(2)), followed by Fuji Ortho LC (25.9 microg/cm(2); 18.8 microg/cm(2)), Python (6.3 microg/cm(2); 4.2 microg/cm(2)), and Transbond (0.1 microg/cm(2); 0.1 microg/cm(2)). The fluoride release rates were highest during the first days of testing, declining to lower but more stable levels. At the end of 6 months, Fuji Ortho LC released the most fluoride (3.8 microg/cm(2); 3.5 microg/cm(2)) followed by Assure (3.1 microg/cm(2); 2.8 microg/cm(2)), Python (2.6 microg/cm(2); 1.7 microg/cm(2)), and Transbond (0.1 microg/cm(2); 0.1 microg/cm(2)). The type of storage medium did not dramatically affect fluoride release. The second part of the study, undertaken after a year of sample storage, tested the 20 samples of Assure for a further 2-week period, after exposure to running and still distilled water. Although fluoride release rates declined with time, they were still higher than the 1.5 microg/cm(2) level that is referenced as inhibiting decalcification of enamel in a clinical environment. Release rates were similar in running and still water at all time points. Throughout the 6-month period, all 3 fluoride-containing materials had rates of fluoride release that could theoretically inhibit decalcification of enamel.
Acrylic Resins↗
The effect on human salivary flow rate of the temperature of a gustatory stimulus.
In the first study, whole saliva was collected from ten adults during stimulation with sour, carbonated, sweet and water stimuli in the form of 5-ml of ice at about -10 degrees C or of liquids at 0, 8, 20 or 37 degrees C. Parotid saliva was also collected in response to ice or infusion into the mouth of the liquids at different temperatures. Another group of ten adults also collected whole saliva in response to water at 20 degrees C, with or without the presence in the mouth of an acrylic cube of dimensions similar to those of the ice. In a second study, 20 adults collected whole saliva in response to stimulation with 5 ml of water and of an astringent stimulus at 0, 8, 37 and 70 degrees C. In the first study, flow rates fell in the order sour, carbonated, sweet and water and flow rates in response to stimuli in the form of ice were very significantly higher than in response to the corresponding liquids at the four different temperatures. With the sour stimulus, liquids at 0 and 8 degrees C elicited higher flow rates than liquids at 20 or 37 degrees C. Although the presence in the mouth of the acrylic block increased the flow rate of whole saliva, the increase was only about 30% of that achieved with ice. In the second study, the astringent stimulus was a more effective salivary stimulus than water; flow rates were significantly higher in response to liquids at 0 and 8 degrees C than at the higher temperatures and flow rates in response to liquids at 37 degrees C were significantly lower than with the other temperatures. In summary, stimuli in the form of ice were the most effective and liquids at 37 degrees C were least effective in stimulating salivary flow.
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A mathematical model of the influence of salivary urea on the pH of fasted dental plaque and on the changes occurring during a cariogenic challenge.
Urea diffusing from saliva into dental plaque is converted to ammonia and carbon dioxide by bacterial ureases. The influence of normal salivary urea levels on the pH of fasted plaque and on the depth and duration of a Stephan curve is uncertain. A numerical model which simulates a cariogenic challenge (a 10% sucrose rinse alone or one followed by use of chewing-gum with or without sugar) was modified to include salivary urea levels from 0 to 30 mmol/l. It incorporated: site-dependent exchange between bulk saliva and plaque surfaces via a salivary film; sugar and urea diffusion into plaque; pH-dependent rates of acid formation and urea breakdown; diffusion and dissociation of end-products and other buffers (acetate, lactate, phosphate, ammonia and carbonate); diffusion of protons and other ions; equilibration with fixed and mobile buffers; and charge-coupling between ionic flows. The Km (2.12 mmol/l) and Vmax (0.11 micromol urea/min/mg dry weight) values for urease activity and the pH dependence of Vmax were taken from the literature. From the results, it is predicted that urea concentrations normally present in saliva (3-5 mmol/l) will increase the pH at the base of a 0.5-mm-thick fasted plaque by up to 1 pH unit, and raise the pH minimum after a sucrose rinse or sugar-containing chewing-gum by at least half a pH unit. The results suggest that plaque cariogenicity may be inversely related to salivary urea concentrations, not only when the latter are elevated because of disease, but even when they are in the normal range.
Acetates↗
A comparison of the site-specificity of supragingival and subgingival calculus deposition.
The aims of the present study on 40 patients were to quantitate by the Volpe-Manhold method, the amount of supragingival (SPR) calculus, to determine qualitatively the amount of subgingival calculus (SBG), and to determine the association between supragingival and subgingival calculus on vestibular and lingual surfaces of all the teeth except third molars. Kappa values for intraexaminer reproducibility varied between 0.863 and 0.738. There was marked site-specificity of SPR calculus scores, with the highest values by far on the lingual aspects of the lower anterior teeth: central incisor, lateral incisor, and canine, respectively. Although the grades for SBG calculus were higher on the lingual surfaces than on the vestibular surfaces of 25 of the 28 teeth, there was much less site-specificity than for SPR calculus. For the teeth as a whole, there were significant associations (P < 0.001), as tested by chi-square or Fisher's exact test, between SPR and SBG grades on both vestibular and lingual surfaces, between SPR grades on vestibular and lingual surfaces, and between SBG grades on vestibular and lingual surfaces. However, for individual teeth, or groups of similar teeth, only a few of the above associations were statistically significant.
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Recent research on calculus.
This paper discusses the different types of calcium phosphate in calculus and the role of plaque pH in controlling calcium phosphate precipitation (calculus) or dissolution (caries). There is great site-specificity of deposition of supragingival but not subgingival calculus, with highest amounts of the former being present on the lingual aspects of the mandibular anterior teeth. This may be because the plaque there is most alkaline as that region has the highest salivary film velocity and the lowest salivary sugar concentration during consumption of sugar-containing food and drinks. The importance of calculus removal for good gingival health is emphasised.
Alkalies↗
The intra-oral distribution of unstimulated and chewing-gum-stimulated parotid saliva.
The objective was to determine the percentage contribution of parotid saliva to whole saliva and to the saliva at 11 sites in the mouth, when flow rate was unstimulated or stimulated with chewing-gum. The marker substance used was alpha-amylase, as this is in much higher concentration in parotid saliva than in secretions from other salivary glands. Formulae were derived for calculation of the minimum, maximum, and mean percentage contributions of parotid saliva to saliva in different areas of the mouth. The results, from 10 individuals, showed that the contributions of parotid to unstimulated and stimulated whole saliva averaged 30.1% and 35.6%, respectively, whereas the corresponding values for samples from the region vestibular to the upper molars were 56.1% and 61.4%, but only 2.8% and 6.8% for samples from an area vestibular to the upper incisors. Thus parotid saliva was not evenly distributed throughout the mouth. Stimulated samples mostly contained significantly higher proportions of parotid saliva, but the distribution of the parotid saliva was still extremely variable. Because the different regions of the mouth are not exposed to the same fluid environment, this may influence the site-specificity of supragingival calculus deposition and of various diseases such as dental caries.
Adult↗
Effect of a bicarbonate-containing dentifrice on pH changes in a gel-stabilized plaque after exposure to sucrose.
Because many factors influence the acid-forming ability of dental plaque in the mouth, a model system was used in which reproducible Stephan curves could be generated after exposure of a gel-stabilized plaque to sucrose. Simulation of the use of a high-bicarbonate dentifrice at a time when plaque pH had fallen to about 4.5 caused a rapid return of the pH toward neutrality, whereas simulation of the use of a low-bicarbonate dentifrice had much less effect.
Analysis of Variance↗
Thiocyanate levels in human saliva: quantitation by Fourier transform infrared spectroscopy.
A new quantitative method, based on Fourier transform infrared spectroscopy, was developed to evaluate the thiocyanate concentration in human saliva. Saliva samples were collected following a typical protocol and infrared spectra obtained from very small volumes (5 microl) deposited on a barium fluoride substrate. Exogenous potassium thiocyanate was used for calibration of the endogenous thiocyanate. This methodology does not require separation or extraction procedures. Human saliva spectra contain a characteristic marker band, due to thiocyanate, at 2058 cm-1. The integrated area of this band can be used for linear regression analysis and provides a good correlation between band area and thiocyanate concentration. Recovery of thiocyanate added to saliva was 100%. Centrifugation and dialysis experiments demonstrated that thiocyanate in saliva exists as a free or loosely bound ion. Saliva collected in the afternoon from 25 different subjects had a thiocyanate concentration of 0.83 +/- 0.42 (mean +/- SD) mmol/liter. In 4 subjects whose circadian pattern was investigated there was evidence of a higher thiocyanate concentration in saliva samples collected in the morning hours.
Cyanates↗
Effect of a bicarbonate-containing dentifrice on pH changes in a gel-stabilized plaque after exposure to sucrose.
Because many factors influence the acid-forming ability of dental plaque in the mouth, a model system was used in which reproducible Stephan curves could be generated after exposure of a gel-stabilized plaque to sucrose. Simulation of the use of a high-bicarbonate dentifrice at a time when plaque pH had fallen to about 4.5 caused a rapid return of the pH toward neutrality, whereas simulation of the use of a low-bicarbonate dentifrice had much less effect.
Acids↗
The effects of chewing frequency and duration of gum chewing on salivary flow rate and sucrose concentration.
On ten separate occasions, unstimulated saliva was collected from 12 adults and then eight samples of saliva over a 20-min period while chewing, in random order, 3 g of either Wrigley's Spearmint chewing-gum or gum-base at frequencies of 35, 50, 70, 90, or 130 chews/min. With both stimuli, flow rates peaked in the first minute of stimulation and then fell with time. A repeated-measures analysis of variance showed that for both the gum and the gum-base, flow rates were independent of chewing frequency, except during the first minute with the chewing-gum. The gum elicited a significantly higher flow rate over the first 4 min of chewing, while the base elicited a significantly higher flow rate over the 8-20-min period of chewing. The sucrose concentration in saliva was also independent of chewing frequency. The salivary sucrose concentration peaked during the second minute of chewing (mean +/- SE = 424.7 +/- 20.0 mM) and the concentration then fell progressively with time. However, sucrose was still being released into saliva during the 15-20 min period of chewing (12.6 +/- 0.8 mM). Gum-base which had been chewed without access to saliva was softer than unchewed base but showed no change in filler content or a reduction in the average molecular weight. The decrease in hardness of the chewed gum-base may have resulted from improved mixing of heterogeneous phases and increased dispersion of plasticizing agents.
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