**2.3.3 Result**

Along the X axis, the location of the left and right parotid duct orifices varied within a range of -7.5 to +6.1 mm (Mean ± S.D.) from the reference point. Mean location (-0.36 ± 3.76) was just mesial to the reference point. Along the Y axis, the orifice was always located on the positive side of the reference point, ranging from +3.8 to +10.4 mm (mean value: 7.21 ± 2.15) (Fig. 10). This suggests that the parotid duct orifice is located above the reference plane near the contact surface between the maxillary first and second molars. Also, ranges of 13 mm in the mesiodistal direction and 6 mm in the perpendicular direction were noted, showing that

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

flow was either unstimulated or stimulated by the use of chewing gum.

**2.4 Effect of salivary flow rate on fluoride retention in the mouth** 

**2.3.4 Discussion** 

opposite the duct opening.

buccal surfaces of the upper molars.

reports the clearance of the fluoride in the sleep.

**2.4.2 Materials and methods** 

the subjects were awake and when they had been sleeping.

**2.4.1 Aim** 

(Fig.12).

– Measurement of Potassium Chloride in the Agar Using Atomic Absorption Spectrophotometry 63

The main finding from the second study was that clearance from a site directly opposite the opening of the parotid duct was significantly faster than from sites only one cm either mesially or distally. When salivary flow was unstimulated or stimulated, the clearance halftimes mesial or distal to the duct opening were two or more times longer than those

The present results are in conformity with those of Weatherell et al. (1986) who found that when a fluoride tablet was placed in the buccal vestibule, the fluoride concentration peaked in the fluid adjacent to the tablet but was much lower both mesially and distally. The previous reports and our results suggest that when parotid saliva exits the parotid duct, it primarily flows downwards and then, from the results of Weatherell et al. (1986), probably lingually over the occlusal surface of the teeth, rather than flowing mesially or distally in the buccal sulcus. If it flowed primarily in either of these two directions, one would have expected very little difference between the clearance rates from the mesial or distal agar cylinder and that from the cylinder positioned over the parotid duct opening. Sass and Dawes (1977) also reported that very little parotid saliva appeared to flow mesially when

In conclusion, the degree of individual variation in the location of the parotid duct orifice is great and its exact location will markedly affect oral clearance at different positions on the

Salivary clearance rates in different parts of the mouth are known to vary. The clearance half-times on the buccal surfaces of the upper anterior teeth were the longest of any site in the mouth. These show that the saliva secreted into the oral cavity is not perfectly mixed. Weatherell et al (1986) reports the difference by the fluoride distribution in the mouth after fluoride rinsing. Duckworth and Morgan (1991) and Heath et al. (2001) have also reported oral fluoride retention after use of fluoride rinse. These researches demonstrate the mechanism of the salivary clearance reported by Dawes (1983). According to Lear et al (1965), the salivary flow rate in the sleep is almost similar to the zero, but there are few

The purpose of this research was to measure the site-specificity of fluoride clearance when

40 mg of NaF and 5 ml distilled water were mixed with 0.15 g agarose which was heated until the agarose dissolved. Aliquots were pipetted into holders (diameter 4 mm, depth 1 mm) and these were bonded onto mouthguards produced from plaster casts of each subject

The bonding sites were on the labial of maxillary incisors (UAB), the buccal of left maxillary molars (UPB) and the lingual of lower incisors (LAL). When the subjects were awake, the

there was a high degree of inter-individual variation. No significant left-right differences were identified. The intra-individual right-left differences were significantly less (P< 0.001) than the overall variability among subjects.

The unstimulated parotid saliva flow rates for left and right sides were 0.02 ± 0.02 and 0.02 ± 0.02 ml/min, respectively and no significant difference was found between results for the two sides. No significant differences in half-time could be detected between comparable left and right regions. Fig.11 shows the half-times for the right and left sides without stimulant. The half-time of the central cylinder was the shortest, followed by the mesial and then the distal cylinders, in that order, for both left and right sides. The half-time values among the 3 cylinders were all significantly different.

Fig. 10. The location of the parotid duct orifice. The symbols indicate the individual results for the 35 subjects. The x indicates the mean position of the duct orifice.

Fig. 11. Half-times when saliva flow was unstimulated
