Measurement of resting whole saliva

Comparison of a New Test for the Measurement of Resting Whole Saliva with the Draining and the Swab Techniques

Pia López-Jornet 1 Ambrosio Bermejo-Fenoll 1 J. Vicente Bagan-Sebastian 2 Eliseo Pascual-Gomez 3 1Department of Oral Medicine, University of Murcia, Murcia, Spain 2Department of Oral Medicine, University of Valencia, Valencia, Spain 3Department of Rheumatology, University of Alicante, Alicante, Spain

Braz Dent J (1996) 7(2): 81-86 ISSN 0103-6440

A quantification method for measuring whole saliva is described. This whole saliva test (WST) consists of a Whatman paper strip, is easily carried out, innocuous, low-cost and single use. Due to its characteristics, it could be considered as the oral equivalent of Schirmer’s tear test. A sample of 159 healthy subjects (81 males and 78 females; mean age 31.62 years) participated in this comparative study of this new procedure and two other tests, the draining and the swab test. Correlation was statistically positive among the three types of tests.

Key Words: resting whole saliva, salivary flow rate, draining method.

Introduction

The pathological reduction of the salivary flow may cause several problems, among them an increase of the susceptibility to caries, oral infections or alterations in mastication, taste, swallowing and diction (Dawes, 1987; Fox et al., 1987; Mandel, 1989). The sensation of dry mouth, a subjective symptom, is known as xerostomia (Manthorpe and Axell, 1990). The value of this symptom, that very frequently does not correlate with the actual levels of saliva production, is frequently relegated to the subjectivity of the doctor or the patient. Hence, the importance of the quantification of saliva production using an objective method. There are several methods for the measurement of the quantity of saliva that a human being produces per unit of time, both at resting conditions or stimulating the secretion, such as for parotid saliva, intra-oral cannulation in the duct, Lashley cups (and their modifications), and Schneyer’s device. Techniques for the measurement of whole saliva are usually based on draining to a recipient, in the re-collection by aspiration or in the increase in weight of an absorbent material that is chewed or placed somewhere in the mouth (White and Bunting, 1936; Brown, 1970; Stephen and Speirs, 1976; Saunte, 1983; Guter et al., 1987). However, although used in research, these methods are not normally used by doctors or dentists in their daily practice. In 1903, Schirmer described some methods for the functional examination of the lacrimal gland, based in the wetting of filter paper strips. Schirmer’s Method I measures the lacrimal secretion at conditions of minimal stimulation. Filter paper strips are used (0.5 x 3.5 cm) with rounded corners in one end which is folded and introduced into the conjunctival sac in the intersection of the medium third and external third of the eye-lid. Five minutes later, the strips are removed and the length of the moist portion is measured. Schirmer’s test was conceived to objectively detect the degree of lacrimal secretion (Prause et al., 1982; Ueda et al., 1983; Yagi, 1986), to evaluate xerophtalmia, the current diagnostic criteria of Sjögren syndrome (Manthorpe et al., 1986). The goal of this study is to present an objective and quantifiable whole saliva measurement test (WST), similar to Schirmer’s test, based on the wetting of a material, innocuous, easy to reproduce and carry out, inexpensive and practical.

Material and Methods

The sample was formed by 159 healthy subjects (81 males and 78 females; mean age 31.62 years). The inclusion criteria to participate in the study were: (a) not having any systemic or nervous illness or any important physical defect; (b) not taking any medications or drugs or being under any type of treatment; (c) not having any symptoms of dry eyes or dry mouth; (d) not having suffered in the past any type of illness or treatment that could have an effect on the normal functioning of the salivary gland; (e) pregnant or nursing women were excluded. Collection was carried out in an air-conditioned laboratory (mean temperature 20ºC). Tests were carried out between 10:00 and 12:00 a.m. Each subject was instructed to adopt the position known as “coachman position”: the sitting subject lowers his trunk vertically, the back is curved and the head hangs forwards slightly. Before starting the test, the subject swallows the saliva he/she has in the mouth. During the five minutes of the test, the subject remains relaxed and with eyes closed. For each subject, three tests were held in the same session, separated by a resting period of 10 minutes. First, the whole saliva test (WST) which measures flow rate (cm/min) was carried out. Whatman paper 41 was used uniformly cut in 1 x 17 cm strips. Then, a millimetred rule was printed, the first centimeter being left with no print. The strip was introduced in a polyethylene bag of low density and was sterilized with ethylene oxide. The non-millimetred centimeter of the strip was extracted from one end of the bag. Then, this centimeter was folded in a 90º angle and inserted in the buccal cavity under the tongue, the non-millimetred portion being in contact with the mouth mucosa. When lips were closed, they lightly contacted the bag protecting the millimetred portion of the strip from moisture. The saliva produced accumulated in the lingual vallecula and slowly soaked the strip. After five minutes, the subject opened his/her mouth, the strip was extracted and the wet centimeters read (López-Jornet, 1992) (Figure 1). If during the test, a strip was humified before the five minutes, the exact time was registered and the rate for five minutes calculated. We then carried out the draining technique (ml/min) (Navazesh and Christensen, 1982) and finally the swab weighing test (g/min)(Peck, 1959). We applied Student’s t mean comparison test (P<0.05). We carried out a simple linear regression analysis and obtained Pearson’s correlation coefficient; the values were considered statistically significant at P<0.05.

Results

Of the 159 subjects studied, the youngest participant was 5 years old, the oldest 77, and the mean age was 31.62, with a typical deviation of 13.92. There were 81 males (50.9%) and 78 females (49.2%) in the sample. With the whole resting saliva test (WST) procedure, the mean value of wetting of the strip in 5 minutes was 4.328 ± 2.15 cm.The test-retest reliability (r) was 0.666. The mean values obtained for males was 4.68 cm and for females 3.985 cm. Applying Student’s t mean comparison test of non-paired data to the results for males and females, we obtained a value of t = 2.02 and P = 0.0451. With the draining technique, measured in ml, the mean value for a 5-min period was 1.136 ± 1.153 ml, the lowest value obtained was 0 and the highest 4.5 ml. With the swab technique, the mean value was 1.156 ± 0.993 g, the lowest value was 0.074 g and the highest 4.989 g (Table 1). A correlation study was carried out by simple regression of the WST at resting conditions, the draining test and the swab test, and Pearson’s correlation coefficient was calculated, as well as the P value. The correlation between the draining and the swab tests was r = 0.286 and P = 0.0006, The correlation between WST and the draining test was r = 0.295 and P = 0.0002. The correlation between WST and the swab test was r = 0.24, P = 0.0031 (Figure 2 A,B,C)

Discussion

As pointed out in the introduction, in spite of the numerous methods for the collection of saliva, they are rarely used in daily practice. Neither the general practitioner, nor the specialist, has incorporated into their usual practice any of the methods used in research for the quantification of saliva produced per unit of time. Studies that compare methods for quantification of the salivary flow are scarce. However, our results seem to indicate that at least the most widely accepted methods are realiable and there are no important differences among them. The draining test and the swab test were carried out following the norms given by the classic authors (Peck 1959; Heintze et al., 1983). Our results with the draining test were similar to those found by Heintze et al. (1983) but slightly lower than Navazesh and Christensen (1982). With the swab test, the mean value was 156 g. These values are below those obtained by Peck (1959). Perhaps these differences could be due to the fact that, in our experiment, subjects remained very relaxed in the coachman position and with eyes closed, and therefore, were not submitted to visual stimuli, while the cited authors allowed subjects to open their eyes. The coachman position was taken from Schultz’s book “Concentrative self-relaxation” (1969), and we considered it a good procedure for the normalization of salivary quantification tests. By simple linear regression, a significant correlation was found between the draining test and the swab test. This means that when the values of the draining test increase, the values for the swab test do the same; in this sense, our results agree with those from other authors (Navazesh and Christensen, 1982; Heintze, 1983). Similarly, applying a simple regression analysis, significant relations were obtained between the WST and the draining test and the WST and the swab test. Thus, when the values of the draining or the swab test increase or decrease, the values for the WST do the same (P = 0.0002 for the former and P = 0.0031 for the latter). The WST, as Schirmer’s test, has proven to be a whole saliva measurement procedure of easy operation and reproduction, requiring no special equipment. The strips are inexpensive and do not require much space for storage, as would be the case for sialometers. The parallelism between Schirmer’s test and the WST is evident: the same material (Whatman paper 41); the same principle (the paper strip is soaked by the fluid by absorption); the same time (5 min) and the same measurement carried out in millimetres. These similarities favor the future use of the WST. Our test also has some small advantages compared to Schirmer’s test. First, the resting test causes less stimulation, since the oral mucosa is used to contact with solid elements but the conjunctive mucosa is not. The stimulus produced when the oral mucosa contacts the strip and the bag is minimal, since these materials are soft and flavorless. Other tests have been designed to measure whole saliva flow rate, e.g., Saxon test (Kholer and Winter, 1985) which consists in chewing a sterile sponge, or partial parotid saliva flow such as the test of Davis and Marks (1986) measuring parotid saliva using a strip of Schirmer’s test The WST, a new whole saliva quantification test, can be considered as the true oral equivalent to Schirmer’s test. We could say that WST is to saliva what Schirmer’s test is to tear. The WST can be used, according to the correlations obtained, instead of the draining test or the swab test, that require special equipment and are uncomfortable in their operation, and therefore are not appropriate for common use in the day-to-day medical practice.

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Correspondence: P. Lopez-Jornet, Hospital Universitario Morales Meseguer, Clinica Odontologica Universitaria, 2 planta, Cátedra de Medicina Bucal, C/Marques de los Velez s/n, 30008 Murcia, Spain.

Accepted October 22, 1996
Electronic publication: February, 1997

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