H.A. Zander

Preliminary Reports on the Effect on Dental Caries of the Use of Sodium Fluoride in a Prophylactic Cleaning Mixture and in a Mouthwash

Previous reports (1, 2) have shown that the activity of dental caries can be reduced by bringing aqueous solutions of sodium fluoride into contact with the freshly cleaned tooth surfaces of children. Unfortunately, the methods so far employed for this purpose are somewhat time-consuming and require the employment of techniques not usually used by dentists or dental hygienists. Therefore it seemed desirable to determine whether alternative and simpler methods of topical treatments with fluoride solutions might not bring about comparable reductions in caries activity. For this reason it was decided to study the effects of: 1. Incorporating sodium fluoride in a cleaning mixture which could be used in a routine way by dental hygienists giving oral prophylaxes, and 2. The use of a mouthwash containing sodium fluoride. Because it had been shown (3) that fluoride solutions buffered to an acidity of pH 4 reduce the solubility of enamel and dentin much more than do ordinary aqueous fluoride solutions, it seemed advantageous to use such acidulated preparations in these studies.

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.

Penicillin and Caries Activity

To test for interference with carbohydrate fermentation, the following procedure was used: 4 cc. of pooled stimulated saliva added to 1 cc. of a 20% glucose solution were incubated at 370 C. for 4 hours. At the end of this period, the pH of the saliva-glucose mixtures was determined electrometrically. As a control, 4 cc. of the saliva were incubated with 1 cc. of distilled water. The test agents were added in various concentrations to the saliva-glucose mixtures before incubation. Results typical of 20 tests are shown in Table I. Pooled saliva and glucose alone produces a pH of 4.0 after 4 hours incubation. However, when 10 units of penicillin are present, no acid is formed.

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.