W.W. Wainwright

Human saliva XIII. Rate of flow of resting saliva of healthy individuals

The necessity of determining the normal variation of salivary rate of secretion among healthy individuals, and thereby establishing a cross-section of the population, has been stressed repeatedly (6, 7, 25, 19) because of the known effects of changes of rate of flow on most salivary constituents. Few reports only are available on a sufficiently large number of observations which would permit the biometrical evaluation of these relationships. The lack of attention to the fact that human saliva is a secretory and/or excretory product is reflected in the exclusive use of mg. % values, a measure of concentration, rather than of mg./hr. values, i.e., a measure of total secretion per time unit (9). Furthermore it has been intimated that decreased salivary rate of flow may be related to the dental caries process, while increased secretion may have a beneficial effect on the teeth and oral mucosa (20, 21, 22, 23, 24, 28, 31, 34, 39). The great variations in speed of salivary secretion met by every investigator has made it very desirable to establish averages of rates of salivary flow in human beings of all age groups under standard conditions.

Human Saliva: IX. the Effect of Activation On Salivary Flow1

The great variation of results of calcium and phosphorus analyses of activated saliva have suggested that the many stimulating or activating factors render the value of A.S. rather questionable as a medium for comparative purposes. Very little information is available which gives the changes in salivary content produced by chewing a tasteless and inert activator, as for instance paraffin, and still less is known about the individual response to activation of saliva in persons with fast or slow flowing R.S. For this reason 30 individuals were requested to produce R.S. for 15 minutes and then for the production of A.S. to chew a 1 gram piece of paraffin 450 times. The experimental conditions were the same as previously reported (4, 28). The classification into Groups I and II again was made in order to study the influence of differences in rate of flow; Group I included 15 individuals with originally low rates of flow, i.e., up to 20 cc. R.S. per hour, aged 12 to 63 years; and Group II, 15 with over 20 cc./hr., aged 6 to 35 years. Table I demonstrates the changes in rate of flow from R.S. to A.S. in both groups. Even though the average rate of flow of R.S. (Table I, Columns A, bottom row) of Group I is approximately one-fourth that of Group II (9.0 and 39.7 cc./hr., respectively) the ranges for A.S. (Columns B) are-surprisingly enough-approximately the same,

Human Saliva: II. A Technical Procedure for Calcium Analysis

Recently a survey of international literature concerning salivary Ca was made by Becks and Wainwright (3). They called attention to the inadequacy of present knowledge of the subject, and to the extreme variation of results reported by former investigators. It was found that salivary-Ca values published by 26 authors varied from 1.5 to 33 mg. percent. None of these investigators showed definite correlation between salivary-Ca content and dental disorders. The 26 authors who attempted to determine salivary-Ca content were divided into three groups: (a) 8 used methods no longer acceptable because technical procedures for Ca analysis have been greatly improved; (b) 8 did not satisfactorily report the technical procedures, making it impossible to judge the reliability of the findings; (c) 10 reported in detail the methods, which showed many differences in technic. These differences suggested a possible reason for the wide range of results. Only the data of Clark and Shell (5), Becks (1, 2), Karshan, Krasnow and Krejci (9), Krasnow (11), Leonard (12), and Horton, Marrack and Price (6), are useful in establishing normal standards. From a strictly scientific aspect, only the results of the five cases of Clark and Shell are acceptable. This unexpected finding indicated definite need for further thorough studies of salivary-Ca content. Becks and Wainwright (3) showed that the very wide range of results in previous work was due partly to the methods of Ca analysis, and partly to the basis on which subjects were selected. Differences that affected results occurred in preliminary treatments of saliva

Human Saliva: XI. The Effect of Activation on Salivary Calcium and Phosphorus Content

Heidenhains law (23) stipulates that electric stimulation of salivary secretions in animals alters the composition of saliva in a definite way. In human beings, a relationship is found between the rate of flow of resting saliva and calcium and phosphorus content (11); however, it it is the reverse of Heidenhains law in that mg. per cent calcium and phosphorus values decrease rather than increase with higher speeds of secretion, and vice versa. Because of this observation, the changes in salivary composition produced by paraffin activation were studied.

Human saliva. 15. Inorganic phosphorus content of resting saliva of 650 healthy individuals.

The surmise has been frequently voiced that disturbances in phosphorus metabolism may be responsible for the incidence of dental caries. The reports by McCollum (32); Klein and McCollum (30); Agnew, Agnew and Tisdall (1); and Price (33) suggest that a lowered phosphorus intake in experimental animals and human beings is accompanied by a greater incidence of dental caries than in controls. Furthermore Eddy, Heft, Rosenstock and Ralston (27) reported a decrease of salivary phosphorus content as a result of high sugar meal. The exact mechanism, however, as to how this lowered phosphorus intake or lowered salivary phosphorus content may be related to dental decay has remained obscure. Experience with salivary analyses has revealed the surprising picture that the inorganic phosphorus content frequently exceeds by many times that of the blood serum level. While the inorganic phosphorus level of blood serum ranges between 3 and 5 mg. %, mixed human resting saliva values have been reported (7) from 2.5 to 49.2 mg. %. This wide variation may have some significance; however, before a possible correlation with oral lesions can be attempted, analyses of normal saliva must be made in a wide range of age groups. For this reason inorganic phosphorus studies were made of 650 individuals from 5 to 95 years of age for whom the rates of flow and calcium analyses and technique have been reported previously (11, 5, 36).

Human saliva. 5. A technical procedure for phosphorus analysis.

The technical procedure of phosphorus analysis has offered great difficulties because of the slow growth of knowledge of the phosphorus fractions and their organic combinations, and the great variations in concentration and amount of phosphorus in the material examined. Most salivary methods have been of the type not requiring preliminary precipitation of phosphorus. The continuous improvement which these methods have undergone has lately resulted in simple, speedy micro methods having an accuracy claimed to be within -t2 to 3 per cent over a range of phosphorus from 0.01 to 0.04 mg. It has been shown (12, 12A) that most investigators of salivary phosphorus used one of the following colorimetric methods: Bell-Doisy (13) (or modifications thereof); Kuttner and Cohen (74) (or modifications thereof); Tisdall (112); or Fiske and Subbarow (34). In spite of the fact that methods were used which are accepted as accurate for the analysis of blood, the results of salivary analysis vary so much that it is not possible to compare the work of different authors. It was therefore necessary to survey the literature from the standpoint of the phosphorus fraction examined because this important point was ignored in the interpretation and description of data by many in-

Human Saliva: VI. Methods of Biometrical Evaluation of Salivary Analyses

In view of the slow progress dentistry has made during the last few decades with regard to some of the outstanding oral problems as caries, paradentosis, root resorption, pathologic bone formation, salivary composition, etc., the need for statistical evaluation of carefully described and classified material has become of paramount importance. Only few attempts have been made in dentistry to evaluate clinical material properly by biometrical means and many authors who have spent years of valuable time in meticulously recording clinical observations did not avail themselves of scientific means for the interpretation of their findings. Many failed to demonstrate the maximum value of their results because of unfamiliarity with the most effective ways of treating accumulated data. It must be admitted that biometrical procedures require a large amount of time, sometimes even as much as that consumed in accumulating the data themselves. The fundamental work in biometry of Martin (44), Pearson (47), and Yule (61), has been greatly advanced in recent years by Davenport (9), Fisher (16), Pearl (49), and others with the development of practical methods which can be used without great difficulty in the biological fields. Biometry (statistical methods specially prepared for the evaluation of biological material) is a science in itself. It is very difficult to master in its entirety. The application of the standard biometrical

Human Saliva: III. Critical Discussion of Former Salivary Phosphorus Studies and their Value in the Establishment of Normal Standards

In a recent publication (11) an attempt was made to establish the present status of technical procedures in salivary calcium analysis. Emphasis was placed on the necessity of establishing normal ranges for salivary constituents, which, based on a large amount of material, will serve as standards by which any pathologic composition can be judged. Today in any discussion of normal and pathologic calcium metabolism, due consideration must be given to the various phosphorus fractions and their distribution because it is increasingly apparent that they are interdependent in metabolic processes. For many years it was believed that dental caries, paradentosis and pathologic bone formation were primarily calcium problems, because one is easily inclined in speaking of enamel, dentin, cementum and bone to think in terms of only their chief constituent. However, recent authors [McCollum (84); Klein and McCollum (63, 64, 65); Agnew, Agnew and Tisdall (4, 5); and Price (94, 95, 96, 97, 98, 99, 100)] have expressed the suspicion that caries might be the manifestation of a disturbed phosphorus metabolism which reveals itself in the salivary

Human Saliva XVI. Relationship of Total Calcium to Inorganic Phosphorus of Resting Saliva

Salivary calcium and inorganic phosphorus have been implicated in many ways in the normal and pathologic processes of oral physiology. Especially has it been hoped that the laws of ion concentration and the ratios of these minerals in solution would provide a key to solving the problems of maintaining oral health. The known relationships of calcium and inorganic phosphorus in other biological materials suggests the possibility of a correspondence between their levels in saliva. For this reason a study of the relationships between these minerals and their ratios and products has -been made; previously reported analytical material (2, 1, 4) was used for this purpose.

Human Saliva: XVII. Relationship of Total Calcium and Inorganic Phosphorus to Rate of Flow of Resting Saliva

A dependence of salivary composition upon rate of flow has been recognized (1, 2, 9. 10, 11, 14, 16); in many studies, however, its possible effect on the results has been ignored (12, 13, 17, 20). Salivary composition is altered markedly by paraffin activation, because of the increased rate of flow (5, 7, 8, 15, 19). Analyses of resting saliva from different individuals and from the same individual on different days show significant differences in group averages of calcium and phosphorus content in extreme rate of flow groups (4). Great variation in the relationship between rate of flow and composition seems to exist which indicates that the relationship is complex. For the study of this relationship a further evaluation of the resting saliva values of 650 individuals previously reported in this series (6, 3, 18) was made.