C. Dawes
University of Manitoba
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Journal of Dental Research | 1987
C. Dawes
This paper discusses methods for collection of both whole saliva and individual gland secretions, the normal ranges of salivary flow rate, the effects of physiological variables which influence flow rate, and the role of saliva in oral sugar clearance. The physiological basis for the sensation of dry mouth is discussed, and a new concept is advanced which states that the sensation of dry mouth will occur when the salivary flow rate is less than the sum of the rates of water absorption and evaporation from the mouth. In a study of the effects of anticholinergic agents on salivary flow, the subjects experienced the sensation of dry mouth when the normal flow rate of unstimulated saliva was reduced by from 40 to 50%.
Journal of Dental Research | 1987
L.M.C. Collins; C. Dawes
The surface area of the mouth was measured to calculate the average thickness of the salivary film which separates the opposing layers of the oral mucosa and which also overlies the dental plaque. The subjects were 10 adults of each sex, all of whom had essentially a full complement of teeth. Impressions were taken of the upper and lower jaws, the buccal and labial vestibular mucosa, and the ventral surface of the tongue, and stone models were cast. The dorsum of the tongue was assumed to have the same area as the palate plus that of the palatal surfaces of the upper teeth. The six separate areas considered were the teeth, the palate, the buccal and lingual gingival and alveolar mucosa, the buccal and labial vestibular mucosa, the ventral surface of the tongue, including the floor of the mouth, and the dorsum of the tongue. Aluminum foil, of known weight per unit area, was adapted to the models of the different regions of the mouth, and the surface areas were calculated from the weights of the foil. The mean total surface area of the mouth was 214.7 ± 12.9 cm 2, and there was no significant difference due to gender. The teeth, keratinized epithelium, and non-keratinized epithelium occupied about 20%, 50%, and 30% of the total surface area, respectively. Given that the average volumes of saliva present in the mouth before and after swallowing have been estimated to be 0.77 and 1.07 mL, respectively, it can be calculated that the average thickness of the salivary film in the mouth varies between 0.07 and 0.10 mm. Since we have previously assumed that dental plaque is washed by a relatively thick layer of saliva, the results have important implications with regard to diffusion of substances in and out of dental plaque and with regard to the sensation of oral dryness caused by fluid absorption through the oral mucosa or by salivary evaporation.
Archives of Oral Biology | 1974
C. Dawes
Abstract At about 8 a.m. on three separate mornings, eight young adults collected two 5-min samples of unstimulated submandibular saliva and then maintained a constant flow rate of 1.0, 2.0 or 3.0 ml/min for 13 min with sour lemon drops as the gustatory stimulus. With stimulation, the pH, ionic strength and the concentrations of protein, sodium, calcium, chloride and bicarbonate increased in proportion to flow rate, the potassium concentration remained almost constant whilst the magnesium and phosphate concentrations decreased, the former being independent of stimulated flow rate but the latter being inversely related to flow rate. Duration of stimulation had slight effects on the protein and potassium concentrations but affected markedly the chloride and bicarbonate concentrations, the former of which rose rapidly at the beginning of stimulation and then fell in a reciprocal manner to the progressive rise in bicarbonate concentration.
Journal of Dental Research | 1984
F. Lagerlöf; C. Dawes
In 20 male and 20 female adult subjects, the volume of saliva in the mouth before (VMAX) and after (RESID) swallowing was determined. RESID could be computed by measuring the potassium and chloride concentrations in unstimulated saliva and in the expectorate after a five-second rinse with 5 ml of water immediately following a swallow. The mean value of RESID after a normal swallow was significantly higher in males (0.87 ml) than in females (0.66 ml). After a forced swallow, RESID was only slightly but significantly reduced, being 0.82 ml and 0.60 ml in males and females, respectively. The volume of saliva normally swallowed was calculated from the unstimulated salivary flow rate and the normal swallowing frequency. The mean value of VMAX (RESID plus volume normally swallowed) in males was 1.19 ml, which was slightly but not significantly higher than that in females (0.96 ml). When water was infused into the mouth at increasing flow rates, there was an increase in VMAX and in both the volume of fluid swallowed and the swallowing frequency.
Archives of Oral Biology | 1973
C. Dawes; C.M. Wood
Abstract To determine the contribution of minor mucous gland secretions to total saliva by a direct method, flow rates of both unstimulated and sour lemon drop (SLD)-stimulated saliva were initially determined in 15 subjects. The right and left lingual nerves were then anaesthetized to halt submandibular and sublingual secretion, and both parotid ducts were cannulated. The only remaining saliva in the mouth was that secreted by minor salivary glands. Unstimulated and SLD-stimulated minor mucous gland secretions were then collected and the median percentage contributions to whole saliva were calculated to be 8 and 7 per cent, respectively. Comparable results were obtained on 3 subjects using an indirect method similar to that of Schneyer (1956). With the left parotid duct cannulated, subjects maintained a constant, SLD-stimulated, left parotid flow rate of 1 ml/min and the remaining mixed saliva was collected to determine its flow rate. The right parotid and the submandibular and sublingual glands were then also cannulated and the flow rate from these glands determined whilst that from the left parotid was maintained at 1 ml/min. The contribution from minor mucous glands was the difference between the flow rate of mixed saliva and the combined flow rate from the right parotid, submandibular and sublingual glands.
Caries Research | 2004
C. Dawes
Xerostomia, the subjective sensation of dry mouth, occurs when the salivary flow rate is less than the rate of fluid loss from the mouth by evaporation and by absorption of water through the oral mucosa. Evaporation can only occur during mouth-breathing but could reach a maximum rate of about 0.21 ml/min at rest, although normally it would be much less. Water absorption through the mucosa can occur because saliva has one sixth the osmotic pressure of extracellular fluid, thus creating a water gradient across the mucosa. The maximum absorption rate is calculated to be about 0.19 ml/min, declining to zero as the saliva reaches isotonicity. A recent study found the residual saliva volume, the volume of saliva left in the mouth after swallowing, to be 71% of normal in patients with severe hyposalivation and whose mouths felt very dry. Saliva in the residual volume is present as a thin film which varies in thickness with site. The hard palate has the thinnest film and when this is <10 µm thick, evaporation during mouth-breathing and/or fluid absorption may rapidly decrease it to zero, resulting in xerostomia. This is also generally associated with reduced secretion from the soft palate minor glands, which may contribute to the film on the hard palate. Thus, xerostomia appears to be due, not to a complete absence of oral fluid, but to localized areas of mucosal dryness, notably in the palate. Unstimulated salivary flow rates >0.1–0.3 ml/min may be necessary for this condition to be avoided.
Journal of Dental Research | 1989
C. Dawes; S. Watanabe; P. Biglow-Lecomte; G.H. Dibdin
Previously, we studied the clearance rates of KCI from agarose gels positioned at different locations in the mouth, and showed that the rates were much slower than when clearance was into a well-stirred solution. We designed the present in vitro study to test the effect on KCI clearance of the velocity of a 0.1-mm-thick film of water flowing over an agarose gel of the same diameter and composition as those used in vivo. The thickness of the salivary film overlying dental plaque has been estimated to be about 0.1 mm, and we assumed that when clearance rates in vitro matched those found in vivo, velocities of the fluid film (in vitro) and the salivary film (in vivo) must be equal. On this basis, it was calculated in the present experiments that when salivary flow was unstimulated, the velocity of the salivary film at the level of the teeth varied between about 0.8 mm/min (upper-anterior buccal region) and 8.0 mm/min (lower-anterior lingual region). When salivary flow was stimulated, this was estimated to increase the velocity of the salivary film from 2 to 40 times, depending on the location in the mouth. It is postulated that the slow movement of the salivary film when flow is unstimulated allows for accumulation of diffusants from dental plaque, which reduces the concentration gradient for diffusion from plaque and prolongs the clearance time of such metabolic products as acid.
Archives of Oral Biology | 1988
S. Watanabe; C. Dawes
The effects of seven different foods and three concentrations of citric acid in 16 adult subjects of each sex were evaluated. The foods were steamed rice, french fries, cheeseburger, cookie, milk chocolate, apple, and rhubarb pie. The volume of saliva was determined by subtracting the initial weight of food from that of the food bolus after subjects had chewed it normally and then spat it into a weighed container, without swallowing. The flow rates were compared with those produced in response to infusion into the mouth of 52, 156 and 260 mmol/l citric acid through a plastic tube at a constant rate of 5.0 ml/min, controlled by a peristaltic pump. Mean salivary flow rates were highest with rhubarb pie and lowest with rice; these were 70.5 +/- 11.3 and 43.2 +/- 14.4 per cent, respectively, of the maximum flow rate (7.07 +/- 2.16 ml/min) elicited by 260 mmol/l (5 per cent) citric acid. The chewing times per 10 g of food were inversely related to the water content (r = -0.82). The water content of the food bolus varied over a wide range (28-87 per cent). Thus normal foods elicit a salivary flow rate which is a high fraction of the maximum secretory rate achieved in response to acid.
Archives of Oral Biology | 1978
K. Abe; C. Dawes
Abstract In an attempt to determine whether the types of proteins in rat parotid and submandibular saliva could be influenced by the nature of the stimulus, ductal secretions were collected from anaesthetized, adult male Sprague-Dawley rats in response to a variety of stimuli. The different types of proteins were quantified after separation by anionic and cationic disc gel electrophoresis on acrylamide gels. The relative proportions of the different proteins in either secretion were not influenced by the age of the rats above 2 months. For parotid saliva, no differences in the types or proportions of the different proteins were detected in saliva elicited by electrical stimulation of the parasympathetic nerve to the glands, by cholinergic or by α- or β-adrenergic agonists, despite large differences in salivary flow rates and protein concentrations in response to those different stimuli. The relative proportions of proteins were the same in the secretions collected at both 7:00 and 18:00h, the times of expected minima and maxima, respectively, in the secretory protein content of the glands. For submandibular saliva an α-adrenergic agonist, methoxamine, and electrical stimulation of the chordalingual nerve elicited the secretion of additional types of proteins to those released in response to methacholine, pilocarpine or isoprenaline. Secretion of these additional proteins was abolished by the α-adrenergic blocker, phentolamine, but not the β-adrenergic blocker, propranolol. It is postulated that in rat submandibular glands the acinar cells secrete protein in response to cholinergic, α- and β-adrenergic stimulation, with β-adrenergic stimuli being most effective, whereas the granular tubules secrete proteins different from those secreted by acinar cells and only in response to α-adrenergic stimulation.
Archives of Oral Biology | 2015
C. Dawes; Anne Marie Lynge Pedersen; Alessandro Villa; Jörgen Ekström; Gordon Proctor; Arjan Vissink; Dj Aframian; Richard McGowan; Ardita Aliko; Nagamani Narayana; Ying Wai Sia; Revan Kumar Joshi; Siri Beier Jensen; Alexander Ross Kerr; Andy Wolff
This narrative review of the functions of saliva was conducted in the PubMed, Embase and Web of Science databases. Additional references relevant to the topic were used, as our key words did not generate references which covered all known functions of saliva. These functions include maintaining a moist oral mucosa which is less susceptible to abrasion, and removal of micro-organisms, desquamated epithelial cells, leucocytes and food debris by swallowing. The mucins form a slimy coating on all surfaces in the mouth and act as a lubricant during such processes as mastication, formation of a food bolus, swallowing and speaking. Saliva provides the fluid in which solid tastants may dissolve and distributes tastants around the mouth to the locations of the taste buds. The hypotonic unstimulated saliva facilitates taste recognition. Salivary amylase is involved in digestion of starches. Saliva acts as a buffer to protect oral, pharyngeal and oesophageal mucosae from orally ingested acid or acid regurgitated from the stomach. Saliva protects the teeth against acid by contributing to the acquired enamel pellicle, which forms a renewable lubricant between opposing tooth surfaces, by being supersaturated with respect to tooth mineral, by containing bicarbonate as a buffer and urea and by facilitating clearance of acidic materials from the mouth. Saliva contains many antibacterial, antiviral and antifungal agents which modulate the oral microbial flora in different ways. Saliva also facilitates the healing of oral wounds. Clearly, saliva has many functions which are needed for proper protection and functioning of the human body.