Roald J. Shern

Influence of age on the secretory rates of the human minor salivary glands and whole saliva

This investigation comprised two studies of healthy, unmedicated individuals. The first measured the effect of collection time on the volume of secretions of the minor salivary glands at four specified areas of the lower lip of 13 individuals before and after a mild gustatory stimulus. The second (n = 51) monitored the influence of age and gender on the secretory rates of unstimulated labial, buccal and palatal salivary glands. Also, unstimulated and stimulated flow rates of whole saliva were monitored to provide a point of reference. Volumes of minor gland secretions were measured with a Periotron unit. Results of the first study indicated a linear increase in volumes with collection time (15, 30, 45 and 60 s). Flow rates were similar among the four labial sites, approx. 1 microliter/cm2/min, and were not influenced by mild citric acid stimulation. Results of the second study indicated that flow rates differed significantly (p = 0.0001) among the anatomical sites, with similar rates on the right- and left-hand sides. Gender exerted no influence on flow from the minor salivary glands. Similarly, age exerted no influence on flow from the buccal or labial glands. However, the secretory rate for the palatal glands decreased significantly with age (r = -0.44; p < 0.005). As for unstimulated whole saliva, secretory rates were not influenced by age nor gender; rates for stimulated whole saliva increased with age (r = 0.31; p < 0.05). No association was detected between the flow rates of the whole saliva and that of the minor salivary glands.

A Method for Measuring the Flow of Saliva from the Minor Salivary Glands

This investigation evaluated a procedure to measure the quantity of secretion by the minor salivary glands from various locations in the mouth before and after citric acid stimulation. Fourteen healthy non-medicated adults were assessed on each of two morning visits at the same specific areas of the mucosa (labial, buccal, and palatal). During each assessment, an absorbent paper strip was placed on each designated location for 30 s, removed, and its moisture content determined with a calibrated Periotron™. Calibration procedures indicated that readings were linearly associated with known saliva volumes and were negligibly influenced by differences in salt concentration and viscosity. At each visit, the buccal flow was significantly greater than those from the lip and palate. The flow from glands in each area was unaffected by a single application of the gustatory stimulant. The mean flow rates at each specified site were similar during the two visits.

Effects on Whole Saliva of Chewing Gums Containing Calcium Phosphates

To evaluate chewing gums as a vehicle to increase salivary mineral saturation levels and enhance salivation, monocalcium phosphate monohydrate (MCPM) and an equimolar mixture of tetracalcium phosphate (TTCP) with dicalcium phosphate anhydrous (DCPA) were chosen as experimental chewing gum additives. Each of eight subjects chewed a commercial sugarless bubble gum (control) for 16 min or the same gum to which 5 wt% of MCPM or the TTCP-DCPA mixture had been added. The saliva samples collected every 2 min were analyzed for weight, pH, and total calcium (Ca) and phosphate (P) concentrations. Both experimental gums were found to increase significantly the Ca and P concentrations of saliva during the 16-minute period even more than with a previously evaluated gum that contained dicalcium phosphate dihydrate. The degree of saturation of tooth mineral was significantly increased by both experimental gums, with the greater increase being produced by the TTCP-DCPA gum. The MCPM gum produced a significantly greater saliva flow and a lower salivary pH than did the control and TTCP-DCPA gums. The results suggest that the experimental gums may be useful for promoting remineralization in general and for inducing salivation in xerostomic patients.

Development and in vitro Evaluation of an Intra-oral Controlled-release Delivery System for Chlorhexidine

Copolymers of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) were prepared and used to fabricate a membrane-controlled reservoir-type controlled-release delivery system for chlorhexidine that should be suitable for intra-oral use. The reservoir of the system was prepared bys softening an 80:20 mixture of chlorhexidine diacetate and 50:50 HEMA:MMA copolymer with methyl ethyl ketone (MEK), and pressing standard amounts of the resulting dough-like mixture into silicone rubber molds. A membrane was applied to the reservoirs by rotating them through a solution of 30:70 HEMA:MMA copolymer in MEK. The finished oval-shaped controlled-release pellets were approximately 4. 7 mm wide, 3.3 mm high, and 7.4 mm long, and contained 45.0 ± 3.7 mg of chlorhexidine diacetate. The mean in vitro release rate of chlorhexidine diacetate from the pellets into 37°C water was 608 ± 55 μg/24 h for days 2 through 11, and 389 ± 50 μg/24 h for days 15 to 30 of the test period. The chlorhexidine released on day 30 was biologically active, as determined by a serial dilution assay against Streptococcus mutans. The extended release of biologically active chlorhexidine at a controlled rate from this system suggests that it is worthy of further evaluation for the intra-oral therapy of chlorhexidine-treatable oral infections in non-compliant and physically or mentally compromised individuals.

Effects of Rinses with an Acidic Calcium Phosphate Solution on Fluoride Uptake, Caries, and in situ Plaque pH in Rats:

The effects of oral rinses on enamel fluoride uptake, caries, and plaque pH in rats were investigated by use of (1) an acidic calcium phosphate solution (CPS) saturated with dicalcium phosphate dihydrate (DCPD) and (2) a 1% fluoride solution. Osborne-Mendel rats, 19 days of age, were randomly assigned to one of four mouth-rinse treatment groups, with the two consecutively administered rinses being: H2O-H 2O; H2O-F; CPS-H20; and CPS-F. The treatments were administered on days 1 through 4, and the animals were provided with a cariogenic challenge throughout the study. The groups treated with F exhibited significantly higher mean levels of enamel-bound F than did the non-F groups. Furthermore, CPS significantly increased uptake of F by enamel when used as an adjunct to the F treatment. The caries scores of the CPS-F and H2O-F groups were not statistically different; however, a strong negative correlation was observed between enamel F content and caries scores, indicating that as more F was incorporated into the teeth, less caries formation occurred. Despite the significant differences in enamel F and caries scores among some of the treatment groups, post mortem in situ plaque pH drop in response to a sucrose rinse showed no differences among these groups.

A method for measuring secretions from the palatal minor salivary glands.

This study investigated the secretory pattern of unstimulated minor salivary glands in 10 contiguous specified areas of the hard palate in 12 healthy unmedicated adult men and women. Each participant was assessed twice at each of two visits in the same specific palatal areas from the distal portion of the second molar to 30 mm anterior. The 10 areas were isolated, dried, and sampled with a paper strip for 60 seconds. The strips were read with a Periotron device. The rates of flow were significantly influenced by position; higher values were noted posteriorly and medially during testing and retesting at both visits. The rates of flow from the palatal glands were greatest in the area between the maxillary second molars. This method proved to be simple, accurate, and reliable for measuring the secretions of the palatal glands. This method may prove useful for investigating how the relationship between the pattern and the secretory rate of minor salivary glands influences retention of the complete maxillary denture.

Effects of Sequential Calcium Phosphate-Fluoride Rinses on Dental Plaque, Staining, Fluoride Uptake, and Caries in Rats:

Oral rinses which included (1) an acidic calcium phosphate solution containing 0.7 M Ca, 1.9 M PO4, and saturated with respect to CaHPO4 · 2H 2O, and with a pH of 2.0, followed by (2) a 0.52 M fluoride solution, from NaF or SnF2, were provided to rats once daily for seven days. The investigation consisted of two studies: In the first study, the amounts of dental plaque on the tooth surfaces and fluoride concentrations in the outer enamel were assessed seven days after the last treatment; in the second study, the extent of dental caries was evaluated seven weeks after the last treatment. All rinse sequences containing fluoride provided significant caries protection. The acidic calcium phosphate treatment markedly enhanced the ability of the enamel to acquire fluoride without change of surface morphology. Only the rinse sequences that included stannous fluoride showed significant plaque suppression.

Effects of Sequential Calcium Phosphate- Fluoride Rinses on Fluoride Uptake in Rats

This study measured the effects of a calcium phosphate rinse followed by various fluoride rinses on fluoride uptake by enamel in rats. Calcium phosphate rinses promoted fluoride uptake by the enamel.

Effects of Stannous Fluoride and Tiodonium Chloride on Dental Plaque in Rats

Rats with six-day-old plaque were treated twice daily with mouthrinses containing either tiodonium chloride, stannous fluoride or a placebo. Although the results for tiodonium chloride were unremarkable, stannous fluoride mouthrinses proved to be significantly effective in removing dental plaque and in restricting the ability of plaque to lower the pH of sugar solutions.

Effects of an Acidic Calcium Phosphate Solution and the Intraoral Fluoride-Releasing Device on Dental Caries and Fluoride Uptake in Rats

This investigation comprised two studies evaluating the effects of an acidic calcium phosphate solution (CPS) on fluoride uptake in the enamel, glycolysis of dental plaque, the incidence of dental caries and urinary fluoride concentrations of rats wearing an intraoral fluoride-releasing device (IFRD). In the first study, CPS-fluoride treatment preceded the cariogenic challenge. In the second study, the cariogenic challenge preceded the treatments. In the first study, CPS treatments increased the ability of enamel to bind fluoride. However, the enamel-bound fluoride exerted a negligible effect on plaque glycolysis as measured by the pH decrease after sucrose challenge. In the second study CPS augmented the caries inhibition for both the sulcal-morsal and buccal-lingual surfaces. In both studies the IFRD significantly restricted the development of carious enamel on the sulcal-morsal surfaces and caused elevated concentrations of fluoride in the urine independent of CPS treatments.