Use of a paper-strip absorption method to measure the depth and volume of saliva retained in embrasures and occlusal fussae of the human dentition.

Embrasures and occlusal fossae are regions of the human dentition that readily retain saliva, as well as dental plaque and dietary substrates. In this study, a wax filling and weighing technique was used to determine the volumes of these irregularly shaped spaces, and a paper-strip absorption method was developed for measuring the thickness and amounts of saliva therein. The volumes were measured on dental stone models prepared from alginate impressions of the maxillary arches of each of eight individuals and on an acrylic maxillary denture representative of the shape and alignment of normal-sized adult teeth. Embrasure volumes in the two cases were similar and ranged between 4.0 and 16.4 microliters for the individual participants, and between 4.8 and 14.9 microliters for the denture. Occlusal fossae volumes of posterior teeth determined on the denture ranged between 6.0 and 9.8 microliters. The paper-strip absorption method for the thickness or amount of saliva in embrasures or fossae consisted of the absorption of the saliva in these sites on to filter-paper strips and the measurement of the collected volumes electronically with a Periotron 6000 micro-moisture meter. Residual saliva for the embrasures between the two central incisors and the second premolar and first molar ranged between 0.12 and 0.56 with means of 0.28 and 0.37 microliter, respectively, for the same eight participants. Corresponding saliva Vmax volumes were 0.48 and 0.63 microliter, respectively. Further paper strip absorption measurements of saliva in embrasures and fossae showed a linear relation between Periopaper dipstick values and embrasure saliva volumes when these were less than 1 microliter. This range includes most residual saliva volumes normally found in these sites in vivo. For volumes of saliva greater than 1 microliter, small increments in dipstick values in embrasures corresponded to very large changes in total embrasure volumes, which reflects their exponential widening beyond about that point. For saliva thickness measurements, a blue food dye was used to construct a standard curve relating depth of saliva in embrasures and fossae (measured with an electronic micrometer) to Periopaper dipstick scores (measured with the Periotron). The relation was linear for both sites, with r values of 0.98 and 0.99, respectively (p < 0.001 for each), and was used to convert extensive in vivo depth measurements of embrasures and fossae determined in microlitres by the dipstick method in an earlier study to thicknesses in millimetres here. In the earlier study, residual saliva on oral mucosal and smooth dentition surfaces was quantified by the blotting method. Together with the method developed here, it should now be possible to measure the saliva, residual or otherwise, on all oral surfaces whether uniform or irregular in shape.

Measurement and comparison of the residual saliva on various oral mucosal and dentition surfaces in humans.

Using a paper-strip absorption method, the amounts of residual saliva on 20 soft-tissue sites in different regions of the mouths of 20 individuals were surveyed once in the morning after a 12-h fast and again approx. 1-2 h after lunch. After swallowing, saliva at each site was immediately collected on filter-paper strips in a dipstick fashion for 5 s and the volumes were measured electronically with a Periotron micro-moisture meter. A clear pattern of wetness was evident and was almost identical for fasting and postprandial determinations. The hard palate and labial mucosa were covered with the least residual saliva; the floor of the mouth and back of the tongue were the wettest. In the same 20 participants, the amounts of residual saliva on various dentition sites were next measured and, as expected, much higher residual amounts were found in approximal embrasures and occlusal fossae than on adjacent facial or lingual smooth areas. Molars gave higher values than premolar and incisor embrasures. To relate residual saliva dipstick volumes to saliva thickness values, filter-paper strips were applied flat against the same mucosal or dentition surfaces in 10 of the participants, and the volume of the saliva absorbed was measured electronically as before. As the areas of the strips used were known, saliva thicknesses could be calculated. These ranged from 0.01 mm on the hard palate to 0.07 mm on the posterior of the dorsum of the tongue. For the incisor teeth, the calculated residual saliva thickness determined in the same way was about 0.01-0.02 mm. Blotting values plotted against dipstick values for oral sites where blotting could be readily performed showed a linear relation, which could be used as a standard curve to enable the easily done dipstick measurements in microlitres to be converted to saliva thicknesses in millimeters. As blotting could not be done in embrasures and occlusal fossae, this paper-strip absorption method was unsuitable for similar quantification of residual saliva in these sites but was done in another way described elsewhere. Overall, the results indicated that variations in dental morphology, and in the saliva secreted and available to the different oral regions, are the basic factors responsible for the wide variations in residual amounts of saliva seen on the diverse hard- and soft-tissue surfaces of human mouths. Also, finding that the hard palate and inner lips are covered by very thin films of residual saliva suggested that only a small reduction in their quantity would be needed to trigger the dry mouth sensation in hyposalivators.