Oral mucosal lesions in older people: relation to salivary secretion, systemic diseases and medications.

OBJECTIVES: To determine the prevalence of oral mucosal lesions in a sample of older Danish people and to investigate their associations with age, gender, systemic diseases, medications, xerostomia and salivary secretion. METHODS: A total of 668 community-dwelling individuals aged 65-95 years underwent a clinical examination, measurements of unstimulated and stimulated whole and labial salivary flow rates and an interview regarding xerostomia, general health, medication, tobacco and alcohol habits. RESULTS: Seventy-five per cent of all participants and 70% of the non-medicated ones had one or more oral mucosal lesions. The most prevalent lesions were lingual varicosities (28.3%), denture stomatitis (12.7%), candidiasis (11.8%), fissured tongue (9.1%) and frictional keratosis (8.4%). Lesions were generally associated with smoking and xerostomia. Varicosities were more common in participants with systemic diseases and medication intake, particularly with cardiovascular diseases and agents. Fissured tongue and atrophic tongue were associated with female gender, xerostomia and low unstimulated whole and labial salivary secretion. Oral candidiasis was associated with older age; being male; current smoker; having >3 diseases, intake of medications and low salivary flow rates; and identified in relation to denture stomatitis, fissured tongue and atrophic tongue and median rhomboid glossitis. CONCLUSIONS: Oral mucosal lesions are prevalent in older Danish people and generally associated with changes in both local and systemic factors. Tongue lesions in particular appeared as indicators that may identify patients with specific need of oral intervention.

Different miRNA signatures of oral and pharyngeal squamous cell carcinomas: a prospective translational study.

BACKGROUND: MicroRNAs (miRNAs) are small non-coding RNAs, which regulate mRNA translation/decay, and may serve as biomarkers. We characterised the expression of miRNAs in clinically sampled oral and pharyngeal squamous cell carcinoma (OSCC and PSCC) and described the influence of human papilloma virus (HPV). METHODS: Biopsies obtained from 51 patients with OSCC/PSCC and 40 control patients were used for microarray analysis. The results were correlated to clinical data and HPV status. Supervised learning by support vector machines was employed to generate a diagnostic miRNA signature. RESULTS: One hundred and fourteen miRNAs were differentially expressed between OSCC and normal oral epithelium, with the downregulation of miR-375 and upregulation of miR-31 as the most significant aberrations. Pharyngeal squamous cell carcinoma exhibited 38 differentially expressed miRNAs compared with normal pharyngeal epithelium. Differences in the miRNA expression pattern of both normal epithelium and SCC were observed between the oral cavity compared with the pharynx. Human papilloma virus infection revealed perturbations of 21 miRNAs, most significantly in miR-127-3p and miR363. A molecular classifier including 61 miRNAs was generated for OSCC with an accuracy of 93%. CONCLUSION: MicroRNAs may serve as useful biomarkers in OSCC and PSCC. The influence of HPV on miRNA may provide a mechanism for the distinct clinical behaviour of HPV-infected tumours.

Effects of isoflurane anesthesia and pilocarpine on rat parotid saliva flow.

The purpose of this study was to investigate the effects of isoflurane on unstimulated and pilocarpine-stimulated parotid saliva secretion. Ten male Sprague-Dawley rats weighing 350-400 g were randomized into two groups, and the saliva flow rate and lag phase were measured at two doses of isoflurane in a crossover study design. Increasing the isoflurane concentration from 1% to 2% was associated with a 19% decrease in saliva secretion rate, and the lag to saliva secretion was increased by 155%. To clarify whether the effect of isoflurane (1.5%) on the parotid flow varied with stimulus intensity, we measured the parotid flow induced by seven different doses of pilocarpine on sham-irradiated rats and rats irradiated with single doses of 15 Gy. A maximal pilocarpine response was obtained with 1.5 mg/kg in both irradiated and sham-irradiated rats; however, the parotid flow of the irradiated rats was 50% slower than that of the sham-irradiated rats. In conclusion, 1.5% isoflurane was found to be a good compromise between proper anesthesia and isoflurane-induced inhibition of saliva secretion. Pilocarpine induces saliva secretion in a dose-dependent matter, with supra-maximal stimulation achieved using 1.5 mg/kg.

Associations between oral and ocular dryness, labial and whole salivary flow rates, systemic diseases and medications in a sample of older people.

OBJECTIVE: To investigate the associations between age, gender, systemic diseases, medications, labial and whole salivary flow rates and oral and ocular dryness in older people. METHODS: Symptoms of oral and ocular dryness, systemic diseases, medications (coded according to the Anatomical therapeutic chemical (ATC) classification system), tobacco and alcohol consumption were registered, and unstimulated labial (LS) and unstimulated (UWS) and chewing-stimulated (SWS) whole salivary flow rates were measured in 668 randomly selected community-dwelling elderly aged 65-95. RESULTS: Presence of oral (12%) and ocular (11%) dryness was positively correlated. Oral dryness was associated with low UWS, SWS and LS, and ocular dryness with low UWS and SWS. Oral and ocular dryness was related to female gender, but not to age. Only four persons in the healthy and nonmedicated subgroups reported oral and ocular dryness. The numbers of diseases and medications were higher in the older age groups and associated with oral and ocular dryness, low UWS, SWS and LS. On average, women were slightly older, reported more oral and ocular dryness and had lower UWS, SWS, LS and higher numbers of diseases and medications. High prevalence and odds ratios for oral dryness were associated with metabolic, respiratory and neurological diseases and intake of thyroid hormones, respiratory agents (primarily glucocorticoids), psycholeptics and/or psychoanaleptics, antineoplastics, proton pump inhibitors, antidiabetics, loop diuretics, antispasmodics, quinine and bisphosphonates. Ocular dryness was especially associated with neurological diseases and intake of psycholeptics and/or psychoanaleptics. Intake of magnesium hydroxide, antithrombotics, cardiac agents, thiazides, beta-blockers, calcium channel blockers, ACE inhibitors/angiotensin II antagonists, statins, glucosamine, paracetamol/opioids, ophthalmologicals and certain combination therapies was related to oral and ocular dryness. CONCLUSIONS: In older people, oral and ocular dryness are associated with low salivary flow rates, specific as well as high number of diseases and medications, but neither with age and gender per se nor with tobacco and alcohol consumption. New detailed information concerning associations between medications and oral and ocular dryness has been obtained using the ATC classification system.

Can the genotype or phenotype of two polymorphic drug metabolising cytochrome P450-enzymes identify oral lichenoid drug eruptions?

BACKGROUND: Lichenoid drug eruptions (LDE) in the oral cavity are adverse drug reactions (ADR) that are impossible to differentiate from oral lichen planus (OLP) as no phenotypic criteria exist. Impaired function of polymorphic cytochrome 450-enzymes (CYPs) may cause increased plasma concentration of some drugs resulting in ADR/LDE. In an earlier study we did not find more patients with OLP (OLPs) with impaired CYP-genotype. OBJECTIVES: To test if more OLPs have an impaired CYP-phenotype than to be expected from the CYP-genotype and to find clinical criteria characterising oral LDE. METHODS: One hundred and twenty OLPs were genotyped for the most common polymorphisms of CYP2D6 and CYP2C19 that result in impaired function. One hundred and ten did a phenotype test of both enzymes. The exposure to drugs and polypharmacy and the CYP metabolism of the drugs were evaluated. The OLP manifestations were registered. RESULTS: The only difference in OLP manifestations was that patients with a CYP2D6 genotype with less than two fully functional alleles presented more asymmetrical OLP distribution in particular in non-medicated patients (P < 0.05). No more OLPs than expected from the genotype had a phenotype with reduced function. However, the established phenotypic categories could not differentiate between the genotypes with two or one fully functional allele. Nevertheless, among the patients with a phenotype with normal function the patients with only one functional allele had a statistically significant higher metabolic ratio compared to patients with two fully functional alleles (P < 0.05). CONCLUSION: It was not possible to identify LDE by impaired function of polymorphic CYPs.

Polymorphic drug metabolizing CYP-enzymes--a pathogenic factor in oral lichen planus?

BACKGROUND: Oral lichen planus (OLP) is a chronic mucosal disease with a characteristic clinical phenotype. Environmental exposures, e.g. drugs have been associated with the pathogenesis. OBJECTIVES: To test the hypothesis that some OLP lesions have a pharmacological pathogenesis related to polymorphisms of the cytochrome P450 enzymes (CYPs) resulting in poor or intermediate CYP metabolism. METHODS: One hundred and twenty patients with OLP and 180 gender-matched controls without OLP were genotyped for CYP2C9, CYP2C19, and CYP2D6 alleles with absent or reduced function. RESULTS: The prevalence of poor or intermediate metabolizers was not higher among the OLPs as compared with the controls; however, there were higher numbers of variant CYP2D6 genotypes among the OLP females (P < 0.05). There were no differences between the groups with regard to intake of drugs metabolized by polymorphic CYPs or drug or herbal products inhibiting CYPs. The prevalence of CYP2D6*4 alleles among the OLPs was higher [28%; 95% confidence interval (CI) 20-36%] than previously reported among Danes (19%; 95% CI 17-22%). Fifty per cent of the OLPs had a CYP2D6*4 genotype as compared with 30% in the background population (P = 0.0001). The CYP2D6*4 protein has sequence homology with human herpes simplex virus type 1 (HSV1) and Candida albicans, which may result in molecular mimicry. CONCLUSION: It was not possible to substantiate a pharmacological pathogenesis of OLP based on poor or intermediate CYP metabolism. However, molecular mimicry between CYP2D6, in particular CYP2D6*4, and common oral pathogens may be involved in the pathogenesis of OLP.

Identifying sources and estimating glandular output of salivary TIMP-1.

OBJECTIVE: Tissue inhibitor of metalloproteinases 1 (TIMP-1) has been identified as a potential biomarker in diseases such as cancer, cardiovascular diseases and diabetes. Since TIMP-1 resides in most tissues and bodily fluids, we evaluated the potential of using saliva to obtain reproducible TIMP-1 measurements in a non-invasive manner. MATERIAL AND METHODS: Samples of unstimulated and stimulated whole saliva and saliva collected from individual glands were analysed for TIMP-1 content. A TIMP-1 ELISA was validated for use in saliva testing and the most optimal sampling and handling procedures for reproducible measurements identified. Western blotting and MALDI-TOF mass spectrometry were used for confirmatory analyses. RESULTS: The TIMP-1 ELISA was found suitable for saliva measurements. All saliva secretions contained TIMP-1, but in different concentrations ranging from 2.81 ng/mL in submandibular/sublingual saliva to 173.88 ng/mL in parotid saliva. TIMP-1 concentrations were influenced to a varying degree by fluctuations in flow. We found the lowest output in submandibular/sublingual saliva stimulated with 0.5% citric acid (3.56 ng/min) and highest output in chewing-stimulated whole saliva (267.01 ng/min). CONCLUSION: This study shows that saliva contains authentic TIMP-1, the concentration of which was found to depend on gland type and salivary flow. Stimulated whole saliva is suggested as a reliable and easily accessible source for TIMP-1 determinations in bodily fluids.

Expression of two drug-metabolizing cytochrome P450-enzymes in human salivary glands.

OBJECTIVE: The oral cavity is constantly lubricated by saliva and even small amounts of xenobiotics and / or their metabolites in the saliva may affect the oral mucosa. Our aim was therefore to clarify if xenobiotic metabolizing enzymes CYP1A2 and CYP3A4 are expressed in salivary glands. METHODS: Formalin-fixed paraffin-embedded specimens from parotid (10), submandibular (7) and labial (10) salivary glands were examined immunohistochemically and by in situ hybridization for expression of CYP1A2 and CYP3A4 protein and mRNA. RESULTS: CYP1A2 and CYP3A4 protein and mRNA were detected in ductal and seromucous / serous acinar cells in all gland types although to a varying degree and intensity. Mucous acinar cells were positive to a lesser extent. CONCLUSION: The results indicate a xenobiotic metabolizing capability of salivary glands. This may have implications for development of oral mucosal disease as a result of mucosal exposure to metabolites originating from internal sources (blood) as well as from saliva.

Effects of calcium on the erosive potential of acidic candies in saliva.

Theoretical calculations have shown that acidic candies may be potentially erosive upon consumption. However, little is known about the protective effect of adding calcium to potentially erosive candies and about the protective effects of saliva that cannot be fully accounted for by theoretical calculations. Therefore, the aims of this study were to (1) determine the erosive potential of acidic candies with and without calcium and (2) to determine differences between theoretically calculated erosive potential and actual erosive potential in saliva. Twenty healthy test persons sucked acidic candy with and without calcium while their whole saliva was collected into a closed system at different times: baseline, candy-stimulated, and post-stimulated. The erosive potential of the candy was evaluated from candy-induced changes in saliva degree of saturation with respect to hydroxyapatite (HAp) and directly by dissolution of HAp crystals in candy-stimulated saliva. The results showed that similar salivary stimulation was obtained with both candies. The modified candy released more than 13 mmol/l of calcium into saliva, resulting in a lower critical pH, and considerably lower erosive potential than the control (p < 0.001). Although a significant correlation was obtained between theoretical calculation of DS(HAp) and dissolution of HAp crystals (r(s) = 0.65; p < 0.001), many samples obtained by sucking modified candy showed no signs of HAp dissolution in spite of being undersaturated. We conclude that saturation levels and critical pH may not fully reflect when dental erosion is expected to occur in saliva and that calcium addition reduces the erosive potential of acidic candies.

Immediate erosive potential of cola drinks and orange juices.

Little is known about the erosive potential of soft drinks within the first minutes of exposure to teeth, and about the potentially protective role of salivary proteins. We hypothesized that the erosive potential is determined primarily by pH and decreases in the presence of salivary proteins. To investigate this, we first added uncoated hydroxyapatite crystals and, second, salivary-protein-coated hydroxyapatite crystals to 20 commercially available cola drinks and orange juices simultaneously, with pH recordings every 15 sec for 3 min. The amount of apatite lost per liter of soft drink per sec was calculated from titratable acidity values to each pH obtained by crystal addition. The erosive potential within the first minutes of exposure was determined solely by the pH of the drink, and the erosive potential was ten-fold higher in cola drinks compared with juices. However, salivary proteins reduced the erosive potential of cola drinks by up to 50%.

Effects of sucking acidic candies on saliva in unilaterally irradiated pharyngeal cancer patients.

Patients who have received radiation therapy on the head and neck area often use acidic candies to relieve symptoms of dry mouth. Therefore, the aim of this study was to determine the erosive potential in relation to teeth of an acidic candy in 10 such patients. The patients sucked the candy while their whole saliva was collected into a closed system at different times: baseline, candy-stimulated, and post-stimulated. The erosive potential of the candy was evaluated from candy-induced changes in saliva degree of saturation with respect to hydroxyapatite (HAp). Previously published normative values were used for comparison. The results showed that saliva became significantly more undersaturated with respect to HAp in irradiated patients, and failed to return to baseline values during the post-stimulatory period, which it normally does in healthy individuals. Thus, prevention of dental breakdown in these patients should involve counseling regarding choice of stimulant for dry mouth relief.

Effects of sucking acidic candy on whole-mouth saliva composition.

Limited information is available on the effects of sucking acidic candies on saliva composition and the protective role of saliva in this relation. Therefore the aim of this study was to determine salivary effects of sucking acidic candies in vivo in relation to individual variations in whole-saliva flow rate (WSFR) and buffer capacity (WSbeta). Ten healthy young males (24 +/- 2 years) sucked a rhubarb-flavoured acidic hard-boiled candy with tartaric acid available on the Danish market. The whole saliva was collected into a closed system, regarding CO2, at different times as follows: firstly, unstimulated saliva for 5 min (baseline), secondly stimulated saliva for 4 min upon sucking the candy, and finally post-stimulated saliva for 10 min. Saliva pH was determined on a blood gas analyser and WSbeta was estimated from the saliva bicarbonate concentration obtained by the analyser and by ionic balance calculation. The erosive potential of the candy in saliva was estimated from the saliva pH values and degree of saturation with respect to hydroxyapatite (DS(HAp)). The results showed that saliva pH dropped from 6.5 (baseline) down to 4.5 at the fourth minute of sucking the candy, and returned to pH 6.5 five minutes after stimulation (post-stimulated). DS(HAp) decreased upon sucking the candy and saliva from all subjects became undersaturated with respect to HAp. Significant positive correlations were obtained between pH and WSFR (r(s) = 0.47; p < 0.05) and between pH and WSbeta (r(s) = 0.65; p < 0.01). In relation to WSbeta we found that 70% of the buffer capacity originating from the bicarbonate buffer system upon sucking the candy was exerted as phase buffering. We conclude that sucking this type of acidic candies changes whole-mouth saliva composition so that it may have erosive potential and that high WSFR and WSbeta have protective effects against these salivary changes.

Effect of saliva composition on experimental root caries.

The aim of this study was to determine the effect of saliva composition on caries lesion development independently of the flow rate of unstimulated whole saliva (UWS) and other caries-related variables such as lesion progression time, oral hygiene level, and fluoride exposure. We hypothesized that this could be done by developing experimental root caries under carefully controlled conditions in situ in test subjects with UWS flow rates within a narrow window of normalcy. Fifteen female and 5 male subjects (66 +/- 6 years) were selected for the study according to their UWS flow rates between 0.2 and 0.4 ml/min. All subjects developed experimental root caries lesions during a 62-day period in which UWS as well as stimulated whole saliva (SWS) were repeatedly collected and analysed for flow rate, pH, buffer capacity, inorganic, and organic composition. Caries lesion development was determined by quantitative microradiography. The mean UWS flow rate was 0.30 +/- 0.05 ml/min. Significant negative correlations were obtained between UWS total phosphate concentration and mineral loss (DeltaZ; r(s) = -0.72, p < 0.001) and UWS total protein concentration and DeltaZ (r(s) = -0.70, p < 0.01). SWS and its constituents had only limited or no effect on DeltaZ. Qualitative UWS protein analysis (SDS-PAGE) revealed that subjects with low DeltaZ values had broader and more stained amylase bands than subjects with high DeltaZ values. These findings were confirmed quantitatively by HPLC. We conclude that, within a group of subjects with normal UWS flow rates, the UWS composition was more important for caries lesion development than the SWS composition. Furthermore, high UWS concentrations of phosphate, protein, and amylase were caries-protective.

Effects of furosemide and bendroflumethiazide on saliva flow rate and composition.

Aim of this study was to evaluate the effect on saliva flow rate and composition and on perceived xerostomia. The study used a Latin square design, all subjects being once daily (at 7.00 a.m.) taking the bendroflumethiazide (2.5 mg), furosemide (40 mg), or placebo, in a randomised order. Each treatment period of 7 days was separated by wash-out periods of 14 days. Unstimulated and paraffin chewing stimulated whole saliva, and 3% citric acid stimulated parotid and submandibular-sublingual secretion were collected twice daily, at 7.30 a.m., with the patients in a fasting condition (morning values), and at 10.30 a.m., about 2 h after intake of a standard breakfast (lunchtime values), on day 0 (baseline), day 1 (acute treatment), and day 7 (chronic treatment). Saliva flow rates were measured and all four secretions were analysed for the concentration of sodium, potassium, chloride, and total protein. Xerostomia was assessed by means of a Visual Analogue Scale. Statistical analysis used the Wilcoxon signed rank test. For flow rate, only that of submandibular-sublingual secretion was affected, significantly so in the morning during chronic treatment with both drugs. In resting whole saliva the output of both sodium and chloride tended to decrease especially during treatment with bendroflumethiazide, while in submandibular-sublingual secretion the output of all the electrolytes was decreased, especially for potassium and chloride and during treatment with furosemide. Further, xerostomia tended to increase during treatment with furosemide, statistically significant at lunchtime during chronic treatment. In conclusion, this study has demonstrated a modest effect on salivary flow rate and a more pronounced effect on saliva composition, especially in submandibular-sublingual secretion during treatment of healthy volunteers with therapeutic doses of two different diuretics, encouraging clinical studies in hypertensive patients and basic research as to the presence of a thiazide sensitive Na-Cl cotransporter in human salivary glands.

Oral lichen planus and intake of drugs metabolized by polymorphic cytochrome P450 enzymes.

OBJECTIVE: To study if patients with oral lichen planus (OLP) had a medication profile different from that of a control group without oral mucosal lesions. It was hypothesized that OLP lesions might result from poor drug metabolism (PM) because of genetic variation of the major cytochrome P450-enzymes (CYPs with a PM-risk). SUBJECTS AND METHODS: Dental records of 172 OLP patients were reviewed in this cross-sectional study and 152 sex- and age-matched subjects served as controls. The measures for the drug profiles were medicine type (ATC-code), mono- and polypharmacy, CYP-enzyme metabolism pattern, and medicine with a potential to induce lichenoid drug eruptions. RESULTS: Fifty per cent of the OLP patients consumed daily medications as compared with 59% of the controls. The OLP patients more frequently consumed medicines metabolized by CYPs with a PM-risk (P = 0.03). Furthermore, they consumed more medicine with an inhibitory effect on one or more CYPs than the controls (P = 0.01). CONCLUSION: Confounders like sex, age, systemic diseases, drug distribution into the therapeutic classes, and polypharmacy were similar in the two groups; but the OLP patients consumed more drugs metabolized by CYPs with a PM-risk. The results argue for further investigation of associations between OLP, medication intake and the CYP-enzyme metabolic pathways.

Saliva and gastrointestinal functions of taste, mastication, swallowing and digestion.

Saliva has multiple essential functions in relation to the digestive process taking place in the upper parts of the gastrointestinal (GI) tract. This paper reviews the role of human saliva and its compositional elements in relation to the GI functions of taste, mastication, bolus formation, enzymatic digestion, and swallowing. The indirect function of saliva in the digestive process that includes maintenance of an intact dentition and mucosa is also reviewed. Finally, pathophysiological considerations of salivary dysfunction in relation to some GI functions are considered.

Oral findings in patients with primary Sjögren's syndrome and oral lichen planus--a preliminary study on the effects of bovine colostrum-containing oral hygiene products.

Bovine colostrum is rich in antimicrobial substances and growth factors. The purpose of this open study was to examine and compare the interventory effects of daily use of bovine colostrum-containing oral hygiene products (CHP) on oral symptoms and findings in 20 patients with primary Sjogren's syndrome (pSS) and 20 age-matched patients with oral lichen planus (OLP). Objective oral measures and self-assessment of oral symptoms and general health were conducted before and after 90 days' use of CHP. The pSS patients had more systemic diseases, medication intake, oral dryness, poorer general health and lower salivary secretion than the OLP patients, who had the highest plaque index (PI) and the most mucosal soreness. Oral dryness and soreness were correlated to general health. In both patient groups. unstimulated whole saliva flow rate (UWS) had increased, PI and periodontal pocket depth (PPD) were reduced, and general health and oral dryness and soreness had improved after using CHP. A decrease in hyphae was found in candida smears from both groups and in blastospores in OLP smears. A reduction in the extension of the mucosal lesions was observed in 15 OLP patients. Results suggested beneficial effects of intervention with CHP on oral symptoms, general health, UWS, PI, PPD and candidal load in two patient groups--pSS and OLP--representing different oral symptomatology.

Primary Sjögren's syndrome: oral aspects on pathogenesis, diagnostic criteria, clinical features and approaches for therapy.

Primary Sjögren's syndrome (pSS) is a chronic inflammatory systemic autoimmune disease affecting the exocrine glands and predominantly the salivary and lacrimal glands. The impaired gland function is assumed to be a result of progressive lymphocyte-mediated destruction of the exocrine gland tissue leading to the cardinal manifestations, hyposalivation and keratoconjunctivitis sicca (KCS), as well as devastating symptoms of oral and ocular dryness. Although primarily characterised as an exocrine dysfunction, non-exocrine organs may also be affected. The onset and course of pSS is usually insidious but may develop into a disabling disease, which profoundly affects the patient's general well being and quality of life. Moreover, pSS may even evolve into a lymphoid malignancy. The aetiology of pSS remains unknown but the pathogenesis of exocrine cell damage is apparently multi-factorial, including immunological, genetic, hormonal and viral components. Recent research also includes neurogenic aspects of exocrine gland dysfunction, including the interference of immune mediators with glandular response to neurotransmitters released from nerve fibres. pSS usually affects middle-aged women and the female:male ratio is 9:1. The prevalence varies from 0.29-4.8%, depending on the population sampled and the diagnostic criteria used. At present, there are no specific diagnostic tests for pSS and no universally accepted diagnostic criteria. The current therapy is primarily symptomatic. This review focuses on the current oral clinical, diagnostic, pathogenic and therapeutic aspects of pSS.

Relationships between medication intake, complaints of dry mouth, salivary flow rate and composition, and the rate of tooth demineralization in situ.

The aim of this study was to describe the relationships between the rate of tooth demineralisation and medication intake, subjective feeling of dry mouth, saliva flow, saliva composition and the salivary level of lactobacilli. The study group consisted of 28 subjects that were divided into three groups according to their unstimulated whole saliva flow rate. Group 1 had an unstimulated saliva low rate < or =0.16 ml/min (n=10), group 2 had one from 0.17--0.30 ml/min (n=9), and group 3 had one >0.30 ml/min (n=9). The rate of tooth demineralization was determined as mineral loss assessed by quantitative microradiography of human root surfaces, exposed to the oral environment for 62 days in situ. The unstimulated and stimulated saliva flow rates, pH, bicarbonate, calcium, phosphate, and protein concentrations, as well as the degree of saturation of saliva with hydroxyapatite and the saliva buffer capacity were determined. The results showed that almost all subjects developed demineralization, albeit at highly varying rates. Eighty-five percent of the subjects in group 1, 33% of the subjects in group 2, and 0% of the subjects in group 3 developed mineral loss above the mean mineral loss for all the root surfaces in this experiment. Futhermore, group 1 differed significantly from groups 2 and 3 in having a higher medication intake, a more pronounced feeling of dry mouth, lower stimulated saliva flow rate, lower stimulated bicarbonate concentration, lower unstimulated and stimulated compositional outputs (bicarbonate, calcium, phosphate, and protein), and a higher Lactobacillus level. The best explanatory variable for high mineral loss in this study was a low unstimulated saliva flow rate. In conclusion, our results suggest that an unstimulated salivary flow rate < or =0.16 ml/min as described by Navazesh et al. (1992), is a better indicator of increased caries risk due to impaired salivation, than the currently accepted definition of hyposalivation (unstimulated saliva flow rate < or =0.10 ml/min), which relates to the function of the salivary glands (Sreebny, 1992).