**1. Introduction**

50 Macro to Nano Spectroscopy

Wu, T.N., Yang, G.Y., Shen, C.Y. & Liou, S.H. (1995). Lead contamination of candy: an

Saliva is secreted into the mouth at a rate of 0.3 to 0.4 ml per minute. Retained saliva in the mouth physiologically triggers swallowing to carry the saliva out of the mouth. Dawes (1983) have reported the volume of saliva in the mouth just before swallowing, the rate of swallowing, the volume swallowed per swallow, and the volume of saliva in the mouth just after swallowing. Clearance of materials from the mouth is facilitated by alternatelyperformed saliva secretion and swallowing, and thereby the oral environment is maintained relatively constant (Fig.1). The unstimulated salivary flow rate and saliva volume in a single swallowing have the most influence on the efficiency of clearance.

Fig. 1. Saliva volume in the mouth

Saliva is a crucial factor for protection of the oral environment. The rate of oral clearance of sugar and acid is inversely related to the onset and progression of dental caries, as shown particularly in persons with severe hyposalivation.

Estimation of the Velocity of the Salivary Film at the Different Regions in the Mouth


cylindrical central depression (6 mm diameter and 1.5 mm depth).

Fig. 3. Diagram of design of the diffusion chambers

measured.

weight of agarose was more than 2 SD from the mean were excluded.

**2.1.2 Materials and methods** 

– Measurement of Potassium Chloride in the Agar Using Atomic Absorption Spectrophotometry 53

A 1-mol/L solution of potassium chloride was mixed with sufficient agarose (Electrophoresis Purity Reagent; BioRad Laboratories, Richmond, CA) to give a 1.0% solution which was heated until the agarose dissolved. The acrylic chambers(Fig. 3) to hold the gel were rectangular (16 mm in length, 8 mm wide, and 1.5 mm thick) with a

The weight of the agarose held in the center well of each chamber was measured six times using an electronic balance (FX-3200; A&D, Tokyo, Japan), and chambers in which the mean

Two chambers were initially covered with a layer of Parafilm (American Can, Greenwich, Conn., USA), were attached bilaterally by floss to the teeth, with the gel surface away from the teeth. The chambers were attached to the upper first molars for measurement of the posterior sites (UPB) and to both upper incisors for measurement of the anterior site (UAB) (Fig. 4).

After temperature and salivary flow equilibration, the Parafilm was removed at time 0. The first diffusion chamber was removed from the mouth after being exposed to saliva for a selected period of time and the gel was transferred to flasks containing 400 ml of (100 ppm) sodium chloride. Subsequently the second chamber was removed and the potassium chloride extracted by the same procedure. The fluid was agitated intermittently for 90 min, and the potassium concentration was assayed by atomic absorption spectrophotometry (Shimadzu AA-6105, Kyoto, Japan). The times were chosen so that between about 30 and 60% of the potassium chloride would have diffused from the agarose discs. The initial KCI concentration in the agarose discs, which had not been placed into the mouth, was also

Saliva secreted into the mouth flows slowly as a thin film, over the tooth surfaces and mucosa and is cleared from the mouth by swallowing (Fig. 2). However, saliva does not flow equally throughout the mouth, and there are differences in the different areas. Measurement of the volume of saliva and velocity of the salivary film at different locations in the mouth are important for understanding the site-specificity of dental caries and periodontal disease.

Using agar as an artificial-plaque, we have conducted studies on the five following items by measuring the clearance of potassium chloride from the agar using an atomic absorption spectrophotometer.

1) Salivary clearance from different regions of the mouth. 2) Salivary clearance in children with complete primary dentitions. 3) Influence of the location of the parotid duct orifice on oral clearance. 4) Effect of salivary flow rate on fluoride retention in the mouth. 5) Estimation of the velocity of the salivary film at different locations in the mouth.

Fig. 2. Salivary film and plaque
