Vincent F. Lisanti

Thermal Conductivity of Dentin

1 NOWLEDGE of the thermal conductivity of dentin is valuable because there are several instances in which heat flows through dental tissues. During cavity preparation, frictional heat is created by the bur in contact with tooth structure. The number of calories produced is dependent upon such factors as the nature of the cutting instruments, the speed and pressure which is used, the surface area involved, and the time of contact with the surface. The presence or absence of moisture, the temperature of the surrounding air, and the distance of the pulp tissue from the cutting instrument influence the quantity of heat. Many materials now used in restorative dentistry create heat. These include oxyphosphate cements, zinc silicates, silicate cements, and especially the new resinous filling materials. The metals used for restoring teeth conduct heat to or from the oral cavity. Whether or not heat on the external surface of dentin will affect the pulp depends on several factors, including the thermal conductivity of the intervening dentin tissue. The object of this investigation was to determine the thermal conductivity of dentin. The thermal conductivity would affect conclusions concerning the permissible amount of heat that can safely be applied to dentin. It is also important for developing or modifying methods for cavity preparation, for giving specifications for heat conductivity of filling materials, and for amounts of heat permissible during their manipulation. A review of literature reveals no reference to thermal conductivity of dentin. This is not surprising since the standard methods used for determining heat conductivity use samples of test material larger than could be obtained from a human tooth. The largest sample of dentin obtainable with consistency was a piece 6.35 mm. in diameter and 1 to 2 mm. in thickness. Such pieces could be obtained from first and second molars.

Hyaluronidase-producing microorganisms from human saliva

Abstract 1. 1. A method has been described to test hyaluronidase activity of saliva. 2. 2. Hyaluronidase-producing microorganisms have been isolated from 60 saliva samples. The predominant enzyme producer, an alpha hemolytic streptococcus, occuring in 55 per cent of the cases, was identified as Strepto-coccus mitis. Micrococcus pyogenes var. aureus was isolated from 18 per cent of the samples. Alpha and beta hemolytic streptococci of Lancefield groups A and K occurred in 11 per cent of the cases. 3. 3. Upper respiratory and dental diseases caused a marked increase in salivary hyaluronidase titer.

Human parotid gland secretion: flow rate and interrelationships of pH and inorganic components.

Summary Stimulated parotid saliva was collected from 50 individuals using flavored chicle as the stimulatory agent. Analysis of the flow rate and composition indicated a significant positive correlation between the flow rate and the pH, sodium, calcium, and bicarbonate contents. Intercorrelations between the various salivary constituents were also noted. No differences were found in the composition of saliva samples collected in the fasting and postprandial state. The composition of the parotid secretion was found to vary not only from person to person but between the two glands in the same person.

Hydrolytic enzymes in periodontal tissues.

The purpose of this investigation was to explore and describe some of the hydrolytic enzyme activities present in human “normal and abnormal’’ periodontal tissues. The philosophy underlying and motivating this approach developed over a period of years and was informally projected in 1953 with my colleague Bertram Eichel who, a t that time, was a member of the School of Aviation Medicine, Randolph Air Force Base, Texas. Simply stated, it was and still is strongly felt that really fundamental understanding of the problems of the oral cavity could be elucidated best by investigating a broad spectrum of enzyme activities as they reflect the metabolic state of both normal and abnormal tissues. Previous studies with whole human saliva had furnished leads indicating that certain hydrolytic enzyme relationships or patterns existed that could be used statistically as potential diagnostic criteria. Lisanti’ suggested that hyaluronidase activity in whole human saliva could be correlated with the presence of periodontal disease and caries. Later, Lisanti and NIahler2,3 reported that patients involved with periodontal and upper-respiratory diseases exhibited a marked increase in the salivary hyaluronidase titer. Subsequently, Lisanti and Chauncey4 confirmed and extended these findings to include a spectrum of hydrolytic enzymes. Of 10 enzymes studied, 3 showed a correlation pattern with the occurrence of periodontal disease and 3 with the presence of dental caries. Aspects of the latter findings will be examined here as Phase 1 of this report.

The Validity of Hamster Studies in Caries Control

ALTHOUGH the Syrian hamster is widely used in caries research, there is 1A no comparative study between hamster and human caries. This information seems essential to justify the use of the hamster in research directed toward human caries control. A comparison between experimental and human caries control is now possible in the light of investigations carried out with a dentifrice containing an antibiotic.

The production of beta-glucuronidase and hyaluronidase by streptococcus mitis☆

Abstract 1. 1. Microorganisms, isolated from human saliva, carious dentine, and periodontal pockets, which produced both beta-glucuronidase and hyaluronidase were alpha hemolytic streptococci, Streptococcus mitis . 2. 2. The finding of three different strains of Streptococcus mitis is reported. 3. 3. Beta-glucuronidase and hyaluronidase titers from Streptococcus mitis were found to parallel one another. 4. 4. Beta-glucuronidase produced by Streptococcus mitis was found to be predominantly extracellular. 5. 5. Optimum conditions for the assay of beta-glucuronidase activity by Streptococcus mitis are described. 6. 6. The effect of sucrose in acid production on hyaluronidase and beta-glucuronidase activity by Streptococcus mitis was measured.

L(+)‐LACTATE DEHYDROGENASE IN THE HUMAN ORAL CAVITY

Since the introduction of the chemico-parasitic hypothesis of cariogenesis through the brilliant work of Magitot (1878) and by Miller (1890), there has been general acceptance of the idea that acids, produced a5 a result of salivary bacterial fermentation of foodstuffs (carbohydrates), solubilize the inorganic matrix of tooth enamel and dentin and are a prime cause of the caries process. Throughout the intervening years, many investigators have considered the caries problem centering their attention upon p H changes associated with the utilization of sugar (usually sucrose or glucose) by human saliva and plaque in the presence and/or absence of teeth, in vivo or in vitro. [See Office of Naval Research, “Bibliography on Saliva” (1960), Afonsky (1961), and Brislin and Cox (1964).] In recent years a few investigators have approached this problem by determining the amount of lactate production from substrates; for example: Neuwirth and Summerson (195 1) employing human saliva analyzed lactate formation from glucose by direct chemical analysis; and Eggers Lura (1958a, b ) employing human saliva and dental plaque analyzed lactate formation from sucrose and soluble starch by indirect enzyme analysis. Conventional Warburg respirometry has been a far more dependable method for the quantitation of total acid production during the course of carbohydrate metabolism. Hartles and McDonald (1950), Neuwirth and Summerson (1951), Eggers Lura (1954), Hartles and Wasdell (1955a, b ) , Bramstedt, Kronke and Naujoks (1957), Eichel(1961), and Eichel and Lisanti (1964) have determined total acid production by human saliva from glucose under aerobic and/or anaerobic conditions at relatively constant, near physiological pH (7.0-7.4 with C0,-bicarbonate buffered media), permitting the conclusion that metabolism of glucose with the formation of acid (in terms of evolved CO, equivalents) occurs in human whole saliva via the mediation of the Embden-Meyerhof pathway of glycolysis. In general, despite these and other avenues of approach aimed at the resolution of the etiology, progression and ultimate therapy of dental caries, much disagreement exists between investigators dwelling upon this problem. In this regard Hartles (1954) stated, “One of the reasons for so many conflicting reports concerning salivary metabolism is that we lack fundamental data concerning the mode of carbohydrate breakdown in the mouth. Until we have some information concerning the enzymic composition of the whole saliva little interpretation of results will be possible.” In the interim except for sporadic reports: e.g., of salivary aldolase by Hoerman and Robinson (1956) and of salivary and plaque lactate dehydrogenase by Eggers Lura (1958b), little attention has been devoted to the salivary enzymes directly responsible for the metabolism of glycogen, glucose and fructose within the oral cavity. In view of this we instituted a systematic investigation of several salivary dehy-

THE EFFECTS OF DENTIFRICES ON HUMAN SALIVA METABOLISM

Most investigators, concerned with the external environment of the teeth and how this environment may contribute to the development and progress of the caries lesion, have dealt with various metabolic parameters involving saliva and plaque. The biological material of choice most frequently employed in such studies has been paraffin stimulated human whole saliva or sediment preparations made therefrom, the latter sometimes being identified with plaque, debris (including food), and most often bacteria. Beginning with the pioneering work of Magitot (1878) in this field, and regardless of the method of analysis employed, virtually all investigators have attributed detectable metabolic activities found in human whole saliva, saliva sediment, and plaque to oral micro-organisms. Recently we, Eichel (1961), Eichel and Lisanti (1964), seriously challenged this contention and found that paraffin stimulated human whole salivas essentially exhibited the unregulated metabolism of protoplasmic fragments derived from leucocytes within the oral cavity, while the oral bacteria contribution to the salivas total metabolic pool was of a low order of magnitude. Because of the large number of epithelial cells present in such saliva collections, we investigated and demonstrated in related studies (unpublished experiments) that preparations of sloughable epithelial cells from the oral mucosa also yielded low metabolic activity. In view of these findings, we regard stimulated human whole salivas as biological preparations analagous to leucocyte homogenates. With this perspective in mind; and, since almost all dentifrices contain substances, such as: “magic ingredients,” detergents, salts, flavoring agents, etc., which could influence the metabolic balance within the human oral environment, the effect of suitable extracts of several of the more readily available tooth pastes upon the oxygen consumption and total anaerobic acid production of paraffin-stimulated human whole saliva preparations was determined.