Role of Saliva and Salivary Diagnostics in the Advancement of Oral Health.

The objective of this article was to provide an account of some of the developments related to saliva over the first 100 years of the Journal of Dental Research and to outline some of the many biomarkers identified in saliva in the last few years. The first section covers findings in salivary physiology, biochemistry, calcium phosphate chemistry related to saliva, microbiology, and the role of saliva in maintaining oral health. The second section highlights salivary diagnostics, salivaomics, and saliva exosomics in the context of the emerging theme of personalized and precision medicine.

[Medicaments and oral healthcare. Systematic review of the -literature assessing the effect of drugs on the salivary glands]. / Serie: Medicamenten en mondzorg.Systematisch literatuuronderzoek naar effect van medicatie op de speekselklieren.

Evidence-based reviews of drugs causing medication-induced salivary gland dysfunction, such as xerostomia (sensation of oral dryness) and subjective sialorrhea are lacking. To compile a list of medicaments that influence salivary gland function, electronic databases were searched for relevant articles published up to June 2013. A total of 269 papers out of 3,867 records located satisfied the inclusion criteria (relevance, quality of methodology, strength of evidence). A total of 56 active substances with a higher level of evidence and 50 active substances with a moderate level of evidence of causing salivary gland dysfunction are described in this article. While xerostomia was a commonly reported outcome, the objective effect on salivary secretion was rarely measured. Xerostomia was, moreover, mostly reported as a negative side effect instead of the intended effect of that drug. A comprehensive list of medications having documented effects on salivary gland function or symptoms was compiled, which may assist practitioners in assessing patients who complain of dry mouth while taking medications.

The complexity of oral physiology and its impact on salivary diagnostics.

OBJECTIVES: Saliva contains biomarkers for systemic as well as oral diseases. This study was undertaken to assess the variability in the sources of such biomarkers (plasma, cells) and attempted to identify saliva deterioration markers in order to improve saliva diagnostic outcomes. MATERIALS AND METHODS: Inter- and intrasubject variations in salivary gingival crevicular fluid levels were determined by measuring salivary albumin and transferrin levels. The purity of collected glandular secretions was determined by bacterial culture, and the variability in epithelial cell numbers by cell counting and optical density measurement. Saliva sample deterioration markers were identified by RP-HPLC and LC-ESI-MS/MS. RESULTS: Tenfold variations were observed in plasma-derived albumin and transferrin levels, emphasizing the need for biomarker normalization with respect to plasma contributions to saliva. Epithelial cell levels varied 50-fold in samples collected before and after a meal. Salivary fungal levels varied within subjects and among subjects from 0 to >1,000 colony-forming units per milliliter. In saliva samples incubated for various time intervals at 37°C, five peptides were identified that steadily increased in intensity over time and which could be explored as "deterioration markers." CONCLUSION: Taking saliva characteristics appropriately into account will help realize the promise that this body fluid is suitable to be exploited for reliable healthcare monitoring and surveillance.

World Workshop on Oral Medicine VI: a systematic review of medication-induced salivary gland dysfunction.

The aim of this paper was to perform a systematic review of the pathogenesis of medication-induced salivary gland dysfunction (MISGD). Review of the identified papers was based on the standards regarding the methodology for systematic reviews set forth by the World Workshop on Oral Medicine IV and the PRISMA statement. Eligible papers were assessed for both the degree and strength of relevance to the pathogenesis of MISGD as well as on the appropriateness of the study design and sample size. A total of 99 papers were retained for the final analysis. MISGD in human studies was generally reported as xerostomia (the sensation of oral dryness) without measurements of salivary secretion rate. Medications may act on the central nervous system (CNS) and/or at the neuroglandular junction on muscarinic, α-and ß-adrenergic receptors and certain peptidergic receptors. The types of medications that were most commonly implicated for inducing salivary gland dysfunction were those acting on the nervous, cardiovascular, genitourinary, musculoskeletal, respiratory, and alimentary systems. Although many medications may affect the salivary flow rate and composition, most of the studies considered only xerostomia. Thus, further human studies are necessary to improve our understanding of the association between MISGD and the underlying pathophysiology.

The functions of human saliva: A review sponsored by the World Workshop on Oral Medicine VI.

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.

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.

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.

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.

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.

How much saliva is enough for avoidance of xerostomia?

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 microm 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.

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.

Salivary concentrations of urea released from a chewing gum containing urea and how these affect the urea content of gel-stabilized plaques and their pH after exposure to sucrose.

The objectives were to: (1) determine the salivary concentrations of urea during 20 min chewing of a sugar-free gum containing 30 mg of urea; (2) measure the degree to which this urea would diffuse into a gel-stabilized plaque; (3) study the effect of the urea on the fall and subsequent rise in pH (Stephan curve) on exposure to 10% sucrose for 1 min; (4) model the measurements 2 and 3 mathematically. In point 1, the salivary urea concentration of the 12 subjects peaked at 47 mmol/l in the first 2 min of gum chewing, falling within 15 min to the unstimulated salivary concentration of 3.4 mmol/l. Recovery of urea from the saliva averaged 81.5%. 'Plaques' of 1% agarose or 67% dead bacteria in agarose accumulated urea from the saliva roughly as expected, whereas those plaques containing 8% live and 59% dead Streptococcus vestibularis showed negligible accumulation. Computer modelling showed this difference to be due to urease of live bacteria breaking down the urea as rapidly as it entered the plaque. Simulation of the effect of gum chewing subsequent to initiation of a Stephan curve in the latter type of plaque showed a rapid rise in pH but then a fall again on return to unstimulated conditions. This fall had not been seen in previous studies, with Streptococcus oralis, nor was it predicted by the computer modelling. Neither experimental simulation nor computer modelling suggested that chewing urea-containing gum before exposure to sucrose would have any effect on a subsequent Stephan curve. Thus chewing gum is only likely to inhibit caries when it is chewed after consumption of fermentable carbohydrate, rather than before.

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.

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.