John C. Mitchem

Clinical evaluation of cement solubility

This study evaluated a method of comparing the in vivo solubility of permanent luting cements. The cements were carried in crypts placed in complete dentures. A vented cover allowed for free access of fluids. Nine cements were evaluated, and cement loss was measured at 6 months. The glass ionomer (at two powder-liquid ratios) and silicophosphate cements demonstrated an approximately equal amount of solubility, which was less than for the other cements tested. The results of this study are in fairly close agreement with two previously published studies on the clinical solubility of cements.

Predictability of retentive values of dental cements

Abstract Four types of permanent cements were used to determine whether the laboratory tests of compressive and tensile strength were predictive of their retentive abilities when retaining cast gold crowns to natural teeth. The standard laboratory test for film thickness also was compared to the degree of nonseating of these cast restorations. The laboratory tests of compressive and tensile strength are not predictive of retentive ability when considering cements which have differing potentials for reacting with or on the tooth surface. The calculated film thicknesses on the axial walls of the cemented restorations in this study were of the same order of magnitude as those values in the laboratory tests. However, the degree and variance of nonseating of the clinical crowns were considerably greater.

Continued evaluation of the clinical solubility of luting cements

0 ver 35 years ago, Henschel’ reported that zinc phosphate cement mixed on a cold slab provided increased working time. He determined that the laboratory solubility of cements mixed on cold slabs was reduced, provided that the incorporation of moisture, which may precipitate on the slab, is prevented. Recently, a number of studies have reported on the mixing of zinc phosphate cement on glass slabs cooled to below the dew point.“-” In these studies, the precipitated moisture was incorporated into the mix; the solubility evaluations, which were made according to American Dental Association, (ADA) Specification No. 8 using distilled water, showed results within the limits of that specification. The influence of this water contamination on in vivo solubility and disintegration remains unanswered. The recent marketing of the glass ionomer cements has prompted a need to evaluate their clinical solubility. In so doing, the inclusion of cements that have been in use for some time provided a means for comparison. Laboratory studies of solubility have been questioned as to their ability to predict clinical behavior of luting cements. This is especially true when cements of different chemical nature are compared. A recent report described a method for measuring solubility of cement in vivo.’ This article reports on the continuation of this work.

Correlation of laboratory testing to three-year clinical behavior of silicate cements

Abstract A study was carried out to evaluate the correlation between the results of laboratory tests and clinical behavior of silicate cement restorations. Three techniques for placing silicate cement restorations were used. These techniques brought different results when tested for strength and solubility. Changes in surface and marginal integrity of restorations were observed at evaluations made after one and three years of service. At both time intervals, clinically observed changes could not be related to the differences demonstrated by laboratory tests. When considering the specific silicate cement and the specific techniques used in this study, it can be concluded that the differences demonstrated in the laboratory tests of transverse strength and solubility did not predict clinical performance.

Validity of laboratory tests in predicting clinical behavior of silicate cement

T he silicate cements are desirable restorative materials for anterior interproximal and gingival cavities because of the ease of cavity preparation, the ease of insertion and finishing, their anticariogenic nature, and their excellent esthetic properties. However, this material fails clinically, presumably because of its inherent low edge strength and relatively high solubility and disintegrati0n.l A number of authors’-” have stated that the average life of a silicate restoration lies somewhere between 3 and 5 years. All of our current knowledge on the effects of manipulative variables on the physical properties of silicate cements has been derived from the use of laboratory tests with no real understanding of the possible correlations to the clinical behavior of the material. It was, therefore, the purpose of this investigation to determine if the presently used laboratory tests can validly predict the clinical behavior of silicate cements.

The potential of amalgam condensation causing intrusion of capping materials into the pulp

Abstract Three base materials, Dycal, Hydrex, and Cavitec, were tested for resistance to intrusion into the pulp under simulated clinical conditions, including 37 °C. and 100 per cent relative humidity. These base materials resisted pulpal intrusion at their Gilmore initial set time when placed 1 mm. thick over an exposure of 2 mm. and subjected to 583 p.s.i. condensation pressure (3 pounds of force on a 2 mm. condenser). The initial set time for Hydrex is sensitive to variations in humidity. This material required more than twice as long (4½to5½ minutes) to set in the oral environment, when a rubber dam was used. Dycal and Cavitec were not as sensitive to variations in humidity.