John H. Hembree

Leakage of different root canal sealants

One hundred five single-rooted teeth were prepared and filled with ten commercially available root canal paste sealers. Five teeth were filled with only gutta-percha points, fifty teeth were filled with a particular cement alone, and the rest of the teeth were filled with a particular cement in conjunction with gutta-percha points. It was found that the gutta-percha point alone is not sufficient for sealing the periapical foramen; nor are N2 (Sargenti), Rieblers paste, and the iodoform paste. In general, it was found that the combination of gutta-percha and cement is more effective in sealing the periapical foramen. Polycarboxylate cement used in this investigation, although it does not meet all the requirements of a good root canal sealant, was found to yield promising results.

Microleakage of several amalgam systems: An animal study

Restorations placed without the application of cavity varnish to the cavity walls and the cavosurface angle exhibited significant marginal leakage after 24 hours and 3 months. At the end of 6 months a decrease in leakage was exhibited with all alloys. With the exception of two specimens, restorations placed after coating the cavity walls and the cavo-surface angle with cavity varnish demonstrated slight or no marginal leakage at all time intervals. The results of this study indicate that the marginal leakage of a conventional filing alloy, a conventional spherical alloy, and two high-copper alloys are approximately the same. The corrosion-resistant high-copper alloys showed the same degree of marginal leakage as the conventional alloys. The results of this study agree with those of a previously reported in vitro study on amalgam leakage.

Film thickness of cements beneath complete crowns.

The results showed that Durelon, EBAC, zinc phosphate, Epoxylite CBA, and Fynal had thinner film thicknesses than EBA and Fluro-Thin. In addition, venting of a crown resulted in lower film thicknesses with all cements except Fynal and EBAC. No significant differences occurred with these two cements whether the crown was vented or not. Obviously many other factors besides film thickness, such as toxicity, strength, and solubility, have to be considered before selecting a cement for clinical use. When only film thickness is to be considered, all of the cements in the study could be recommended for the cementation of crowns with the exception of EBA and Fluoro-Thin.

Influence of Amalgam, Alloy, and Mercury on the in Vitro Growth of Streptococcus mutans: I. Biological Test System

A procedure is presented for the in vitro growth of Streptococcus mutans in a dextrose-beef extract medium. Growth was estimated spectrophotometrically. The amount of amalgam, alloy, or mercury that was added to the sealed test tube influenced the rate and extent of growth.

Microleakage evaluation of eight composite resins

A n important advance in restorative dentistry in recent years has been the indication that microleakage can be minimized around a composite resin with the use of acid-etching and the placement of an unfilled resin on the walls of the cavity preparation.‘-’ Elimination or reduction of microleakage would result in a decrease in sensitivity, discoloration, and recurrent caries, thereby resulting in greater longevity of composite resin restorations.” Investigations have shown that microleakage is ‘significantly reduced or eliminated in restorations where the cavosurface angle and the enamel are etched and a layer of unfilled resin is placed before and after placement of the restoration.“-r These two studies tested four composite resins. The purpose of this study is to evaluate the marginal leakage of eight composite resins using an acid-etch technique and unfilled resin as indicated by the manufacturer.

In vivo evaluation of marginal leakage of four inlay cements

Marginal leakage was demonstrated in all the inlays at all time intervals with all cements by the use of the isotope Ca45. Gross marginal leakage was observed in all inlays luted with the cyanoacrylate cement at all time intervals. The setting time of this cement is very short, making it difficult to completely seat the inlay before the cement sets. The results of this study indicate that the cyanoacrylate cement is not a satisfactory luting medium for Class V inlays. Inlays cemented with EBA demonstrated leakage patterns similar to those of inlays seated with polycarboxylate and zinc phosphate cements in the specimens taken at 72 hours. In the 3 month and 6 month specimens, greater marginal leakage was seen with EBA cement than with polycarboxylate and zinc phosphate cements. Leakage patterns associated with polycarboxylate and zinc phosphate cements were very similar at all time intervals. The polycarboxylate and zinc phosphate cements showed less marginal leakage than the other two cements at 3 months and 6 months. The results of this study indicate that inlays cemented with polycarboxylate cement and zinc phosphate cement exhibit significantly less marginal leakage than the cyanoacrylate cement and EBA cement over a 6 month period of time.

The bond strengths of resin systems to etched enamel

This study was undertaken to compare the resin-enamel bond strengths of seven anterior restorative resins using the acid-etch technique. Six of the materials (Restodent, Enamelite, Smile, Nuva-System, Concise, and Adaptic) were composite resins. Only one, Sevriton, was an unfilled resin. Of the seven, only Sevriton and Smile were not designed for the acid-etch technique. Of the materials tested, Sevriton and Enamelite had the weakest bonds. There was no significant difference in the bond strength among Nuva-System, Smile, and Restodent; the bonds of all these were stronger than those of Sevriton and Enamelite. Concise showed a significantly greater bond strength than all the other materials in the study except Adaptic and the Nuva-System. The resin-enamel bond strength of Adaptic was of a greater magnitude than that of all other test materials.

Influence of Amalgam, Alloy, and Mercury on the in Vitro Growth of Streptococcus mutans: II. Comparison of Amalgams and Alloys

The influence of three alloys and their amalgams on the in vitro growth of Streptococcus mutans has been estimated. Spherical, fine cut, and dispersion alloys were studied. Dispersion alloy amalgams seem to inhibit bacterial growth more than amalgams prepared from the other alloys in a similar fashion.

Influence of Amalgam, Alloy, and Hg on the In Vitro Growth of Streptococcus mutans: III. Effect of Specimen Age and Composition

In vitro growth inhibition of Streptococcus mutans is lost with sample age at different rates for amalgams Prepared from a spherical, fine cut, and dispersion alloy. Varying the Hg composition from 48 to 52% has little effect on growth inhibition.