The buffer capacity and buffer systems of human whole saliva measured without loss of CO2

Hydroxyapatite formation on a novel dental cement in human saliva

Dental materials have to meet high standards regarding mechanical strength and handling properties. There is however only a limited amount of research that has been devoted to natural formation of hydroxyapatite (HA) in contact with the materials. The objective of the current investigation was to study the surface reactions occurring in human salvia on a novel dental cement. Ceramir Crown & Bridge, a bioceramic luting agent intended for permanent cementation of conventional oral prosthetics, was evaluated by immersing discs made from the cement in human saliva and phosphate buffered saline (PBS) for seven days, after which they were dried and analyzed. The analytical methods used in order to verify HA formation on the surface were grazing incidence X-ray diffraction (GI-XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). All results showed that HA was formed on the surfaces of samples stored in saliva as well as on samples stored in PBS. The possibility of a dental luting cement to promote natural formation of HA at the tooth interface increases the stability and durability of the system and could help prevent secondary caries.

Effect of salivary factors on the susceptibility of hydroxyapatite to early erosion

OBJECTIVE

Salivary pellicle is known to reduce the erosion of enamel and differences in the level of protection exist between individual saliva sources, but which parameters or components are important is not known. The focus of this study was to investigate the relationship between saliva parameters and early erosion of hydroxyapatite (HAp) with an in situ grown saliva film.

METHODS

Twenty-eight volunteers carried two HAp and one porcelain discs in their buccal sulcus for 1.5 h. Next, the discs covered with pellicle and the attached saliva film were exposed extraorally to 50 mM (pH = 3) citric acid for 2 min and unstimulated and stimulated saliva was collected. Calcium loss from HAp after erosive challenge was measured, corrected for calcium loss from pellicle on porcelain discs and averaged. Several salivary parameters were analysed. Pearson's linear correlation and multiple regression analysis were used to study the relation between saliva parameters and HAp erosion.

RESULTS

Significant correlations were found between HAp erosion and the concentration of phosphorus in unstimulated saliva (r = 0.40, p = 0.03) and between HAp erosion and the concentration of sodium (r = -0.40, p = 0.03), chloride (r = -0.47, p = 0.01), phosphorus (r = 0.45, p = 0.01) and flow (r = -0.39, p = 0.04) of stimulated saliva. Multivariate analysis revealed a significant role in the HAp erosion for sodium, urea, total protein, albumin, pH and flow of unstimulated saliva and for sodium, potassium, urea, and phosphorus of stimulated saliva.

CONCLUSIONS

Several salivary parameters are associated with the susceptibility of HAp to erosion.

Parotid gland-recovery after radiotherapy in the head and neck region--36 months follow-up of a prospective clinical study

Background

The aim of the present study was to evaluate the recovery potential of the parotid glands after using either 3D-conformal-radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) by sparing one single parotid gland.

Methods

Between 06/2002 and 10/2008, 117 patients with head and neck cancer were included in this prospective, non-randomised clinical study. All patients were treated with curative intent. Salivary gland function was assessed by measuring stimulated salivary flow at the beginning, during and at the end of radiotherapy as well as 1, 6, 12, 24, and 36 months after treatment. Measurements were converted to flow rates and normalized relative to rates before treatment. Mean doses (D_mean) were calculated from dose-volume histograms based on computed tomographies of the parotid glands.

Results

Patients were grouped according to the D_mean of the spared parotid gland having the lowest radiation exposure: Group I - D_mean < 26 Gy (n = 36), group II - D_mean 26-40 Gy (n = 45), and group III - D_mean > 40 Gy (n = 36). 15/117 (13%) patients received IMRT. By using IMRT as compared to 3D-CRT the D_mean of the spared parotid gland could be significantly reduced (D_mean IMRT vs. 3D-CRT: 21.7 vs. 34.4 Gy, p < 0.001). The relative salivary flow rates (RFSR) as a function of the mean parotid dose after 24 and 36 months was in group I 66% and 74%, in group II 56% and 49%, and in group III 31% and 24%, respectively. Multiple linear regression analyses revealed that the parotid gland dose and the tumor site were the independent determinants 12 and 36 months after the end of RT. Patients of group I and II parotid gland function did recover at 12, 24, and 36 months after the end of RT.

Conclusions

If a D_mean < 26 Gy for at least one parotid gland can be achieved then this is sufficient to reach complete recovery of pre-RT salivary flow rates. The radiation volume which depends on tumor site did significantly impact on the D_mean of the parotids, and thus on the saliva flow and recovery of parotid gland.

Salivary microbial and nonmicrobial parameters in children with fixed orthodontic appliances

OBJECTIVE

To determine the physiologic changes of salivary flow rate, pH, and buffer capacity and the levels of Streptococcus mutans and Lactobacillus spp in patients undergoing fixed orthodontic treatment.

MATERIALS AND METHODS

The study included 23 patients scheduled for fixed orthodontic therapy. All subjects received equal braces, bands, and brackets, bonded with the same material. Stimulated saliva samples were taken before placement of the appliance, and at weeks 6, 12, and 18 during the therapy. Salivary flow rate and salivary pH were measured, and the salivary buffer capacity was determined. Saliva samples were cultivated on selective microbial agar for microorganism detection.

RESULTS

A significant (P < .05) increase in stimulated salivary flow rate and salivary pH was found. The salivary levels of S mutans and Lactobacillus spp also inscreased significantly (P < .05), and the major peak was at week 12 of fixed orthodontic therapy.

CONCLUSION

The 6th to 12th week of orthodontic therapy is the period of the most intensive intraoral growth of S mutans and Lactobacillus spp and a time of very intensive salivary functions and physiologic response.

Effect of surfactants and pH on naltrexone (NTX) permeation across buccal mucosa

The objective of this pre-formulation study was to systematically investigate the effects of two surfactants (Brij 58(®) and Tween 80(®)) and change in solution pH on in vitro permeation of naltrexone HCl (NTX-HCl) across tissue engineered human buccal mucosa. For the study, 10mg/ml solutions of Tween 80(®) (0.1 and 1%, w/v) and Brij 58(®) (1%, w/v) were prepared in standard artificial saliva buffer solution (pH 6.8). For studying pH effects, solution pH was adjusted to either 7.5 or 8.2. As controls, three concentrations of NTX-HCl (2.5, 10 and 25mg/ml) were prepared. Using NTX standard solution (10mg/ml; pH 6.8), the permeation was observed between in vitro human and ex vivo porcine mucosa. It was observed that Brij 58(®) increased the permeation rates of NTX significantly. The flux of 10mg/ml solution (pH 6.8) increased from 1.9 ± 0.6 (× 10(2)) to 13.9 ± 2.2 (× 10(2))μg/(cm(2)h) (approximately 6-fold) in presence of 1% Brij 58(®). Increasing pH of NTX-HCl solution was found to increase the drug flux from 1.9 ± 0.6 (× 10(2)) (pH 6.8) to 3.0 ± 0.6 (× 10(2)) (pH 7.4) and 8.0 ± 3.5 (× 10(2)) (pH 8.2)μg/(cm(2)h), respectively. Histological analyses exhibited no tissue damage due to exposure of buccal tissue to Brij 58(®). The mean permeability coefficients (K(p)) for 2.5, 10 and 25mg/ml solutions of NTX-HCl (pH 6.8) were 5.0 (× 10(-2)), 1.8 (× 10(-2)) and 3.2 (× 10(-2))cm/h, respectively, consistent with data from published literature sources. Increase of NTX flux observed with 1% Brij 58(®) solution may be due to the effects of ATP. Increase in flux and the shortening of lag time observed by increasing in solution pH confirmed earlier finding that distribution coefficient (logD) of NTX is significantly affected by small increments in pH value and therefore plays an important role in NTX permeation by allowing faster diffusion across tissue engineered human buccal tissue.

Does laryngopharyngeal reflux cause intraoral burning sensations? A preliminary study

Intraoral burning sensations are a common problem in the otolaryngological practice. The aim of this study was to evaluate if laryngopharyngeal reflux can cause intraoral burning sensations by measuring oropharyngeal acid reflux. Patients with recurring intraoral burning sensations underwent oropharyngeal pH monitoring in our outpatient clinic. The pH catheter was placed at the level of the uvula. The catheter contained an externally worn transmitter, which wirelessly sent the data to a monitor. In addition, patients were instructed to indicate meals or the occurrence of burning sensations by pressing provided buttons on the monitor. Corresponding events of burning sensations and a significant decrease in oropharyngeal pH values should be visualized. Twenty two patients suffering from recurring intraoral burning sensations underwent oropharyngeal pH measurement for 21-25 h. We could find oropharyngeal reflux episodes in 11 patients. However, we could not detect any episodes of burning sensations in the mouth corresponding with a decrease in oropharyngeal pH values. Our results suggest that there is no causal connection between LPR episodes and the occurrence of intraoral burning sensations in the examined patients. Although further studies with more patients are necessary in the future, we conclude from our findings that recurring intraoral burning sensations are not an indication for proton pump inhibitor therapy.

A nocturnal decline of salivary pH associated with airway hyperresponsiveness in asthma

Salivary pH is associated with esophageal acid reflux and neutralization of esophageal acid. In this study, we assessed the association between nocturnal decline of salivary pH and airway hyperresponsiveness. Salivary pH was serially assessed in 9 patients with mild asthma (7 men and 2 women; mean age 33.3 years; mean %predicted FEV(1.0) 89.4%) and 10 healthy volunteers (6 men and 4 women; mean age 31.2 years) using a pH indicator tape. The buffering capacity of saliva was defined as the median effective dose (ED(50)) for acidification of saliva with 0.01 N HCl, and airway responsiveness was defined as the dose of methacholine producing a 35% fall in Grs (PD(35)-Grs). There was a significant correlation between the values obtained from the pH indicator tape and those obtained from the electrometric pH meter. Using the indicator tape for sequential monitoring, we observed a nocturnal fall (ΔpH) in salivary pH in all subjects. A significant correlation was found between airway hyperresponsiveness (PD(35)-Grs) and either ΔpH or ED(50) in mildly asthmatic patients. Vagal reflux dysfunction might contribute to nocturnal salivary pH as well as to airway hyperresponsiveness in mild asthmatics.

Erosive potential of saliva stimulating tablets with and without fluoride in irradiated head and neck cancer patients

BACKGROUND

Patients irradiated in the head and neck region often suffer from severe dry mouth and use acidic saliva stimulating products, which may cause erosion of teeth.

PURPOSE

To determine saliva stimulating effects and erosive potential (EP) of acidic saliva stimulating tablets (Xerodent) with and without fluoride in irradiated head and neck cancer patients.

MATERIALS AND METHOD

Nineteen irradiated patients (median age 57 years) sucked Xerodent tablets with and without fluoride. Saliva collections were divided into three 10-min sessions in the sequence: unstimulated whole saliva, Xerodent stimulated saliva without fluoride, and with fluoride. Saliva pH was determined without loss of CO(2) and in combination with inorganic measures used to calculate the degree of saturation of hydroxyapatite (HAp) and fluorapatite (FAp). EP was determined directly in all saliva samples by monitored dissolution of HAp crystals.

RESULTS

Saliva flow rates increased significantly (15-fold) when sucking both tablets (p<0.001). Major changes in saliva composition caused undersaturation of HAp in some samples. However, no dissolution of HAp occurred in the saliva obtained with any of the two tablets. This was most likely due to the limited drop in pH resulting in saliva that was still supersaturated with respect to FAp.

CONCLUSION

Both Xerodent with and without fluoride were evaluated as non-erosive, however, for additional caries protection the fluoride variant is preferable.

Effect of Cisplatin on parotid gland function in concomitant radiochemotherapy

PURPOSE

To determine the influence of concomitant radiochemotherapy with cisplatin on parotid gland tissue complication probability.

METHODS AND MATERIALS

Patients treated with either radiotherapy (n = 61) or concomitant radiochemotherapy with cisplatin (n = 36) for head-and-neck cancer were prospectively evaluated. The dose and volume distributions of the parotid glands were noted in dose-volume histograms. Stimulated salivary flow rates were measured before, during the 2(nd) and 6(th) weeks and at 4 weeks and 6 months after the treatment. The data were fit using the normal tissue complication probability model of Lyman. Complication was defined as a reduction of the salivary flow rate to less than 25% of the pretreatment flow rate.

RESULTS

The normal tissue complication probability model parameter TD(50) (the dose leading to a complication probability of 50%) was found to be 32.2 Gy at 4 weeks and 32.1 Gy at 6 months for concomitant radiochemotherapy and 41.1 Gy at 4 weeks and 39.6 Gy at 6 months for radiotherapy. The tolerated dose for concomitant radiochemotherapy was at least 7 to 8 Gy lower than for radiotherapy alone at TD(50).

CONCLUSIONS

In this study, the concomitant radiochemotherapy tended to cause a higher probability of parotid gland tissue damage. Advanced radiotherapy planning approaches such as intensity-modulated radiotherapy may be particularly important for parotid sparing in radiochemotherapy because of cisplatin-related increased radiosensitivity of glands.

[Caries risk estimation in children regarding values of saliva buffer system components and carboanhydrase activity]

BACKGROUND/AIM

One of the preconditions for efficacious systematic reduction of caries prevalence and prophylaxis is the determination of risks of this disease appearance. The aim of this study was to prove the significance of salivary carboanhydrase activity determination in estimation of caries risk in children.

METHODS

The study included 123 children of average age of 13.4+/-0.3 years and permanent dentition. The children were divided into two groups according to caries risk (low and high caries risk groups). Two samples of saliva--unstimulated and stimulated one were taken from each child. Salivary carboanhydrase activity, as well as pH value, bicarbonate and phosphate buffer levels were estimated in both group of saliva samples.

RESULTS

The investigation showed significantly higher carboanhydrase activity (p < 0.001) in both saliva samples in low caries risk group compared to high caries risk one. In children with low caries risk, both unstimulated and stimulated saliva show significantly higher bicarbonate and phosphate buffer concentrations (p < 0.001), as well as pH values.

CONCLUSION

The lower caries incidence could be expected in children with high carboanhydrase activity and higher salivary buffer system parameters levels. The presented results suggest that salivary carboanhydrase activity represents the important marker of individual susceptibility for caries appearance in children.

Saliva as research material: Biochemical, physicochemical and practical aspects

Whole saliva is a complex mixture of proteins and other molecules which originate from several sources. The biochemical and physicochemical properties of saliva contribute to the numerous functions of saliva in, e.g., speech, maintaining oral and general health, and food processing. Interest in saliva has increased in the last few years for its potential to diagnose viral, bacterial and systemic diseases. The use of saliva as research material may pose particular problems due to its inherent variability and instability. This review describes practical aspects of salivary as research material with emphasis on protein biochemistry and physical chemistry.

Buffering effect of a prophylactic gel on dental plaque in institutionalised elderly

OBJECTIVES

The effect of multiple daily applications of a prophylactic gel, with buffering substances, on plaque acidogenicity in elderly institutionalised individuals was evaluated.

BACKGROUND

Many elderly suffer from reduced salivary flow, poor oral hygiene and increased levels of cariogenic bacteria and are considered to be at an increased risk for coronal and root caries. Reinforcing the buffering capacity of dental plaque by the addition of substances such as bicarbonate and phosphates may decrease their caries activity.

MATERIALS AND METHODS

Fourteen elderly, with subjective dry mouth, were treated for 16-day-periods at random with: (i) Profylin fluoride gel with buffering components; (ii) Profylin fluoride gel without buffering components and (iii) rinsing with water. Applications were made four times a day and each period was followed by a 2-week wash-out period. The plaque pH was registered after a carbohydrate challenge and the following were recorded before and after each test period: stimulated salivary secretion rate, buffer capacity, number Colony Farming Units (CFU) mutans streptococci, lactobacilli and a sample of Candida albicans on oral mucosa.

RESULTS

Eleven participants (mean age 76.6 years) fulfilled the study. Changes in plaque pH measurements, when calculated as area under the curve (AUC(6.2) and AUC(5.7)) values (pH x min), before and after each of the three treatments, showed no significant differences. A tendency to a higher plaque acidogenicity and amount of cariogenic microorganisms was found after the gel treatments. C. albicans was found in low levels.

CONCLUSION

Frequent applications of the gel did not result in an improved neutralising effect in the elderly. This may be caused by a combination of several factors, such as the level of oral dryness of the individuals and low solubility, release and retention of the gel substances in plaque. Instead, an increased plaque acidogenicity was noted.

Whole saliva in X-linked hypohidrotic ectodermal dysplasia

BACKGROUND

X-linked hypohidrotic ectodermal dysplasia (HED) is the most common type of ectodermal dysplasia. Identification of female carriers of X-linked HED can be difficult because of varying degrees of clinical symptoms due to the X-chromosome inactivation. This is the first study about whole saliva flow and composition in males affected by HED and female carriers all confirmed by molecular genetic analysis. HYPOTHESIS AND AIM: As salivary glands derive from ectoderm, we hypothesized that whole saliva flow and composition are altered in males affected by HED and female carriers.

DESIGN

Saliva flow and composition were examined in a group of affected males and in a group of female carriers, all confirmed by molecular genetic analysis, and compared with healthy male and female controls.

RESULTS

Affected males and female carriers had reduced whole saliva flow and saliva with high concentrations of most inorganic salivary constituents as well as total protein. However, affected males and female carriers seemed to have reduced amylase activity and concentration relative to their total protein concentration.

CONCLUSION

Saliva flow and composition may be used as part of a comprehensive clinical examination to identify potential female carriers of HED.

Protein buffering in model systems and in whole human saliva

The aim of this study was to quantify the buffer attributes (value, power, range and optimum) of two model systems for whole human resting saliva, the purified proteins from whole human resting saliva and single proteins. Two model systems, the first containing amyloglucosidase and lysozyme, and the second containing amyloglucosidase and α-amylase, were shown to provide, in combination with hydrogencarbonate and di-hydrogenphosphate, almost identical buffer attributes as whole human resting saliva. It was further demonstrated that changes in the protein concentration as small as 0.1% may change the buffer value of a buffer solution up to 15 times. Additionally, it was shown that there was a protein concentration change in the same range (0.16%) between saliva samples collected at the time periods of 13:00 and others collected at 9:00 am and 17:00. The mode of the protein expression changed between these samples corresponded to the change in basic buffer power and the change of the buffer value at pH 6.7. Finally, SDS Page and Ruthenium II tris (bathophenantroline disulfonate) staining unveiled a constant protein expression in all samples except for one 50 kDa protein band. As the change in the expression pattern of that 50 kDa protein band corresponded to the change in basic buffer power and the buffer value at pH 6.7, it was reasonable to conclude that this 50 kDa protein band may contain the protein(s) belonging to the protein buffer system of human saliva.

Characterization of fasted-state human intestinal fluids collected from duodenum and jejunum

The solubility of drugs in the gastrointestinal tract is very challenging to simulate with artificial media due to the high complexity of human intestinal fluid (HIF). In particular, bile salt composition, pH and buffer capacity are very important characteristics of HIF, since they determine the solubility of drugs in-vivo. In this study, we have measured the concentrations of individual bile salts in human intestinal fluids (n=6) collected from two different locations (duodenum and jejunum) in the fasted state. Total bile salt concentrations ranged from 570 to 5,137 microM in the duodenum and from 829 to 5,470 microM in the jejunum. The following rank order of relative bile salt concentration in duodenum was observed: taurocholic acid > glycocholate >or= glycochenodeoxycholate > glycodeoxycholate > taurochenodeoxycholate > taurodeoxycholate. Cholic acid, tauroursodeoxycholate, chenodeoxycholic acid, and deoxycholic acid represented less than 1% of bile salts present in the samples. Ursodeoxycholate could not be detected in HIF. No statistically significant difference between bile salt composition of duodenal and jejunal aspirates was observed. The buffer capacity of HIF was compared with other media commonly used for solubility/dissolution determinations, indicating a relatively low buffer capacity of HIF (4-13 mmol L(-1)/pH). This low buffer capacity was reflected in the change in pH (between 4 and 9.5) that occurred in HIF after addition of model compounds covering a broad pK(a) range. Interindividual variability in pH, buffer capacity and bile salt contents of HIF will contribute to differences in the rate and extent of absorption of compounds for which dissolution/solubility is the rate limiting step. The variability observed warrants further research to explore the impact of intraluminal conditions on drug solubility.

A study of the influence of mouth-breathing in some parameters of unstimulated and stimulated whole saliva of adolescents

OBJECTIVE

The aim of this study was to analyze some standard parameters of the unstimulated and stimulated whole saliva of mouth-breathers and a control group to determine if these variables present any difference in mouth-breathers compared to control group, since these parameters of saliva can influence the oral health.

METHODS

Saliva samples were collected from 61 adolescents aged 10-19 years; 30 were mouth-breathers and 31 were nose-breathers. The unstimulated salivary specimen was collected, followed by collection of the stimulated saliva. Soon after collecting the salivary sample, the flow rate and buffering capacity were determined. The samples were then stored at -80 degrees C until analysis was performed. The analysis consisted of the determination of protein content and total, free and bound sialic acid levels.

RESULTS

No statistically significant difference was observed in the flow rate, buffering capacity, protein content, total and bound sialic acid levels of unstimulated and stimulated saliva, nor in the free sialic acid of stimulated saliva. However, the levels of free sialic acid of the unstimulated saliva were significantly higher in the mouth-breather compared to the control group.

CONCLUSIONS

Since a higher level of free sialic acid is indicative of an increase in the number of bacteria in saliva, our findings suggest that mouth-breathers retain more bacteria in oral tissues.

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.

Water uptake of bonding systems applied on root dentin surfaces: a SEM and confocal microscopic study

OBJECTIVES

Dentin adhesives have been proposed as desensitizing agents to seal exposed root dentin surfaces. Simplified 'one-step' dentin adhesives are highly permeable to water. The authors hypothesized that a lactic acid challenge may increase permeability of simplified adhesives and may induce fast degradation of bonding. This phenomenon adversely affects their durability as long term desensitizing agents. The aim of this in vitro study was to evaluate the ability of four dentin adhesives to seal root dentin surfaces that were exposed to water and lactic acid challenges.

METHODS

Four commercially-available dentin adhesives were applied with a small sponge to the root dentin of extracted human molars as de-sensitizing agents. Impression replicas of the adhesive-covered root dentin were fabricated after water immersion, as a control, and after lactic acid challenge. The replicas were examined with SEM for quantitative comparison of fluid droplet formation on the surfaces. The bonded specimens were also examined using reflected light confocal microscopy.

RESULTS

Replicas of water droplets were observed on the adhesive surfaces, by SEM which corresponded with direct confocal observation of blisters and voids from the surface of the bonded specimens. There were significantly more water droplets from samples that were subjected to lactic acid challenge than water only immersion.

SIGNIFICANCE

Although the dentin adhesives examined were able to cover exposed root dentin, they all exhibited fluid transudation through the polymerized adhesives. Dentin adhesives were also susceptible to surface degradation after lactic acid challenge. As simplified self-etch adhesives were highly water permeable and exhibited the most extensive surface damage, they may not be the best adhesives to be used for long-term dentin desensitization. These preliminary in vitro findings warrant validation in vivo.

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.

A role of salivary carbonic anhydrase VI in dental plaque

OBJECTIVE

Carbonic anhydrase (CA) VI is a unique secreted isozyme of CA, which catalyzes the reversible reaction CO2 +H2O<-->H+ +HCO3-. CA VI has been thought to provide a greater buffering capacity to fluids into which it is secreted. This study was performed to confirm this in saliva.

DESIGN

Nine healthy subjects participated in the study. The pH of the dental plaque from each subject was monitored after a mouth rinse with 10% sucrose with or without 10(-5)M acetazolamide, a specific inhibitor of CA. Also CA was examined in plaque by enzyme histochemistry, immunohistochemistry and Western blot analysis.

RESULTS

Though sucrose and sucrose plus inhibitor yielded Stephan curves with a similar temporal pattern, the pH values of the latter were significantly lower than those of the former. Plaque exhibited CA activity by enzyme histochemistry. Immunohistochemistry and Western analysis demonstrated that the activity was due to CA VI but not to CA I or CA II.

CONCLUSIONS

The results indicate that CA VI in saliva penetrates plaque and facilitates acid neutralization by salivary bicarbonate. Therefore, CA VI may be considered an anti-caries protein in saliva.

Salivary changes and dental caries as potential oral markers of autoimmune salivary gland dysfunction in primary Sjogren's syndrome

BACKGROUND: the classification criteria for primary Sjogren's syndrome (pSS) include a number of oral components. In this study we evaluated if salivary flow and composition as well as dental caries are oral markers of disease severity in pSS. METHODS: in 20 patients fulfilling the American-European Consensus criteria for pSS and 20 age-matched healthy controls whole and parotid saliva flow rates and composition, measures of oral dryness, scores of decayed, missing and filled tooth surfaces (DMFS), periodontal indices, oral hygiene, and dietary habits were examined. RESULTS: in pSS, salivary flow rates, pH, and buffer capacities were lower, and DMFS, salivary sodium and chloride concentrations higher than in the healthy controls. DMFS also correlated inversely to salivary flow rates and positively to oral dryness. Apart from slightly increased gingival index, and more frequent dental visits in pSS, the periodontal condition, oral hygiene or sugar intake did not differ between these two groups. In pSS, findings were correlated to labial salivary gland focus score (FS) and presence of serum-autoantibodies to SSA/SSB (AB). The patients having both presence of AB and the highest FS (>2) also had the highest salivary sodium and chloride concentrations, the lowest salivary phosphate concentrations, lowest salivary flow rates, and highest DMFS compared to those with normal salivary concentrations of sodium and chloride at a given flow rate. CONCLUSION: the salivary changes observed in some pSS patients reflect impaired ductal salt reabsorption, but unaffected acinar transport mechanisms, despite low salivary secretion. Our results suggest that changes in salivary flow and composition as well as dental caries may serve as potential markers of the extent of autoimmune-mediated salivary gland dysfunction in pSS. The study also indicates that the ductal epithelium is functionally affected in some pSS patients, which calls for future pathophysiological studies on the mechanisms underlying this impaired salt reabsorption.

Properties and modification of soft drinks in relation to their erosive potential in vitro

OBJECTIVES

The objective was three-fold; (1) to test the erosive potential (EP) of various soft drinks, (2) to determine properties related to the soft drinks that were important for EP, and (3) to test possibilities of reducing the EP of soft drinks by modification.

METHODS

Sixteen soft drinks from the Icelandic market including three modified soft drinks were used. The pH, calcium, phosphorus, and titratable acid (TA) to pH 5.5, 7.0, and 10.0 were determined in each drink. From these results the buffer capacity (beta) at pH 4.5, 6.3, and 8.5, degree of saturation with respect to hydroxyapatite (DS(HAP)), and critical pH (DS(HAP)=1) were calculated. One orange juice was modified by addition of various concentrations of calcium and phosphate. EP was determined as weight loss from tooth pieces after immersion into the soft drinks for 24 and 72 h as well as calcium increase in the soft drink upon immersion.

RESULTS

EP of the drinks varied from 0-10% weight loss and 0-31 mmol calcium increase. The pH in carbonated and sport drinks was lower than in fruit juices, whereas TA and beta was considerably higher in fruit juices. Significant correlations were obtained between EP and TA, beta, pH, and DS(HAP) (r(s)=0.69-0.90). Addition of calcium and phosphate to the experimental drinks considerably decreased their EP.

CONCLUSION

We conclude that several properties related to soft drinks have an impact on their EP upon long exposure time to teeth and that moderate modification could be a helpful measure to reduce the EP of soft drinks.

Randomized controlled trial of pilocarpine hydrochloride for the moderation of oral mucositis during autologous blood stem cell transplantation

Pilocarpine hydrochloride has been reported to increase salivation and decrease oral mucositis in patients receiving head and neck radiotherapy, but there is only one report of its use in a cancer chemotherapy patient population. This prospective, double-blinded, randomized, placebo-controlled trial was undertaken to determine the efficacy of pilocarpine for the moderation of oral mucositis during autologous blood stem cell transplantation. Subjects were randomized to receive a 5 mg tablet of pilocarpine, or a placebo, during and following chemotherapy. Subjects were seen every other day and evaluated for gingival, oral, and oropharyngeal mucositis; nutrition; oral hygiene; eating; speaking; sleeping; pain at rest and/or with swallowing; and mouth dryness. We recorded the mean and highest scores and duration of problems, along with white blood cell counts and differentials, and the use of systemic narcotics for oral mucosal pain. We enrolled and randomized 36 subjects, and there were no statistically or clinically significant differences for the primary outcome of severity of mucositis and no clinically significant differences in any of the other outcome measures. Pilocarpine has no benefit for the moderation of the incidence, severity, or duration of mucositis in patients receiving autologous blood stem cell transplantation.

Levels of mutans streptococci and lactobacilli in plaque on aged restorations of an ion-releasing and a universal hybrid composite resin

The purpose of this in vivo study was to evaluate the cariogenic microflora of plaque on aged restorations of a hydroxyl, fluoride, and calcium ion-releasing composite resin (IRCR) (Ariston pHc), and to compare it intra-individually with a universal hybrid composite resin and enamel. Each of 19 subjects received one proximal restoration of the IRCR, one proximal universal hybrid composite resin restoration (CR) and each subject had one non-filled proximal enamel control surface to make intra-individual comparisons possible. To avoid peak ion releases from the materials, aged restorations were studied. Plaque was collected from 57 surfaces using sterile applicator tips. Samples were cultured to determine the numbers of mutans streptococci, lactobacilli, and total microorganisms. The relative numbers for mutans streptococci (% of total bacteria) were: IRCR 0.59%, CR 0.40%, enamel 0.22%. Two outliers were found in the IRCR group. Excluding these outliers resulted in a relative number of 0.33%. Lactobacilli were detected in the plaque from only 9 surfaces and at very low relative proportions for all three surfaces: 0.01%. The enamel surfaces showed the lowest relative numbers of mutans streptococci and lactobacilli, but the differences were not significant. It can be concluded that the ion release of the IRCR did not influence the growth of cariogenic microorganisms in dental plaque.

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.

Use of a physiologic bicarbonate buffer system for dissolution characterization of ionizable drugs

PURPOSE

The aim of this study was to examine if sparging with CO2(g) could be used to establish stable biorelevant bicarbonate buffers, in aqueous medium, for use in dissolution characterization of low-solubility ionizable drugs.

METHODS

Preparation of the bicarbonate-containing dissolution medium was monitored by use of a commercially available fiberoptic probe to measure the concentration of dissolved CO2(aq). Intrinsic dissolution measurements at 100 rpm, 37 degrees C for indomethacin and dipyridamole were performed using a rotating disk and UV detection at pH 6.8 and 5.0 in a USP dissolution vessel apparatus.

RESULTS

Indomethacin dissolution at pH 6.8 was significantly impacted by the concentration of CO2(g) in the sparging gas. Dipyridamole flux at pH 6.8 was independent of buffer species or buffer concentrations studied. However, dipyridamole dissolution at pH 5 was also a strong function of the concentration of CO2(g) in the sparging gas.

CONCLUSIONS

Stable bicarbonate biorelevant buffers could be established to perform intrinsic dissolution rate determinations for indomethacin and dipyridamole as long a continuous gas sparging of CO2(g) was used. Depending of the pH of the dissolution medium, the intrinsic dissolution rates of both indomethacin and dipyridamole were affected by the bicarbonate concentration. Sparging with CO2(g) to create physiologic buffers has a unique advantage over conventional buffers in that gas sparging serves as a continuous source of bicarbonate buffer species. This advantage was demonstrated by performing dissolution experiments at pH values typically associated with the fed state (pH 5) and applying relatively low CO2(g) pressures, resulting in bicarbonate concentrations less than 0.5 mM. It was demonstrated that CO2(g) sparging at a pH consistent with the fed state created an in-situ bicarbonate buffer at low concentrations, which had a significant impact on the dissolution of a basic drug such as dipyridamole.

Salivary carbonic anhydrase VI and its relation to salivary flow rate and buffer capacity in pregnant and non-pregnant women

OBJECTIVE

Previous studies have shown that pregnancy may have unfavourable effects on oral health. The pH and buffer capacity (BC) of paraffin-stimulated saliva, for example, have been found to decrease towards late pregnancy. Salivary carbonic anhydrase VI (CA VI) probably protects the teeth by accelerating the neutralization of hydrogen ions in the enamel pellicle on dental surfaces. Since estrogens and androgens are known to regulate CA expression in some tissues, we studied here whether salivary CA VI concentration shows pregnancy-related changes.

DESIGN

Paraffin-stimulated salivary samples were collected from nine pregnant women 1 month before delivery and about 2 months afterwards and assayed for salivary CA VI concentration, BC and flow rate. The enzyme concentration was determined using a specific time-resolved immunofluorometric assay. The control group consisted of 17 healthy non-pregnant women.

RESULTS

The results indicated that salivary CA VI levels varied markedly among individuals, but no significant differences in mean concentrations were seen between the samples collected during late pregnancy and postpartum. BC values were lower during pregnancy, however.

CONCLUSIONS

Our findings suggest that CA VI secretion is not significantly affected by the hormonal alterations associated with pregnancy, and confirm the earlier reports that CA VI is not involved in the regulation of actual salivary BC.

Electrolytes in stimulated whole saliva in individuals with hyposalivation of different origins

There are reasons to believe that changes in the secretion rate of saliva as well as changes in its protein and electrolyte composition promote the growth of micro-organisms associated with oral disorders. Knowledge of the electrolytes in the saliva of those with hyposalivation might therefore be of value in designing oral health-promoting measures. In this study, electrolytes in stimulated whole saliva were analysed in individuals with hyposalivation due to radiation therapy in the head and neck region (RT group), primary Sjögren's syndrome (pSS group), neuroleptic treatment (Neuro group), and to medication or of unknown origin (Unknown group). The bicarbonate concentration was significantly lower in all four hyposalivation groups compared with controls. The bicarbonate concentration, which in normal conditions is positively correlated with the salivary secretion rate, was lower in the Neuro group than in the RT and Sjögren's groups despite a stimulated secretion rate about twice as high. Furthermore, the Neuro group had the highest phosphate concentration. The RT and Sjögren's groups tended to have increased sodium concentrations. For potassium and calcium, the RT group had significantly higher concentrations than the other hyposalivation groups and the controls. The substantial increase in calcium and decrease in bicarbonate suggest that the function of the parotid glands is more affected than that of the other salivary glands. The results also indicate a contribution of plasma to the electrolyte concentrations determined in whole saliva in the RT and Sjögren's groups. In conclusion, in individuals with hyposalivation the concentrations of electrolytes in stimulated whole saliva seem to be more related to the reason for the hyposalivation than to the salivary secretion rate.

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.

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).

Saliva and dental caries

Caries is a unique multifactorial infectious disease. Our understanding of etiological factors, the progress of the disease, and the effectiveness of prophylactic procedures have led us to believe that we understand the disease. However, we still have too few answers to many questions: "Why can we not predict who will get the disease?" "Why do we not become immunized?" "How much saliva is enough?" or "Which salivary components are protective?" and "Which salivary components predispose for caries?" It is generally accepted, however, that saliva secretion and salivary components secreted in saliva are important for dental health. The final result, "caries to be or not to be", is a complex phenomenon involving internal defense factors, such as saliva, tooth surface morphology, general health, and nutritional and hormonal status, and a number of external factors-for example, diet, the microbial flora colonizing the teeth, oral hygiene, and fluoride availability. In this article, our aim is to focus on the effects of saliva and salivary constituents on cariogenic bacteria and the subsequent development of dental caries.