Quintessence International, 01/1995

There are many ways to approach the removal of a cast restoration. In deciding on the most appropriate method, the clinician's primary concern should be to prevent damage to the supporting tissues and to minimize trauma to the patient. The difficulties encountered in meeting this responsibility relate to the practicalities of applying potentially injurious forces in a controlled and predictable manner. Although there is an inherent risk factor associated with all crown removal methods, this paper describes the safest methods of preserving crowns during removal. In addition practical hints are introduced with the emphasis on patient safety and reducing the risk factor to the supporting tissues.

A carefully controlled, 2-year study was undertaken to evaluate the clinical performance of castable glass-ceramic crowns used to restore teeth in the posterior segments. After 2 years of clinical performance, three of the original 101 restorations had failed. Of the remaining 98 crowns, 93 were available for recall; All were rated as excellent for color match, marginal adaptation, and cavosurface marginal discoloration. Postoperative sensitivity occurred in only two of the restored teeth and was noted only at the 6-month recall evaluation. Gingival tissue response was also excellent. The results of this study indicate that this material can be used for the esthetic treatment of posterior teeth that are in need of complete-coverage restoration.

The purpose of this in vitro study was to determine the effects of two 10% carbamide peroxide bleaching solutions on the hardness of enamel from the surface to the dentinoenamel junction. Fifteen anterior teeth wre sectioned faciolingually, and their roots were removed. Hlf of each crown was bleached and half served as its own control. Specimens were bleached with two commercially available 10% carbamide peroxide solutions (Proxigel and gly-Oxide) for 24 1-hour periods. A visible color change occurred. Teeth were embedded in acrylic resin rings, sanded with progressively finer silicon carbide papers, and polished. The polishing process removed approximately 800 jm of the cut tooth surfact. Specimens were tested with ah microhardness tester and a Knoop diamond under a 35-g load; measurements were taken along the cut surface from the outer enamel surface to the dentinoenamel junction. Matching depths from control and test specimens were compared. For teeth treated with Gly-Oxide, no statistically significant changes in enamel hardness were evident at 50 um or deeper. A statistically significant decrease in hardness was noted in the outer 25 um or deeper. A statistically significant decrease in hardness was noted in the outer 25 um of the enamel surface. It is unknown whether this decrease would have an effect clinically because the remineralizing effects of saliva should resolve any surface change.

Gloves are not a panacea. They can be punctured, torn, or damaged in a number of ways. In the dynamic environment in which they are used, gloves function as a bidirectional barrier only when they remain intact. Researchers have shown that latex gloves serve as an effective barrier to most pathogens. More recently, intact gloves have been shown to be a good barrier against viral pathogens. However, neither latex gloves nor cut-resistant gloves will prevent needlestick injuries. When the risk of puncture or tearing is too high, practitioners should conisder donning stronger gloves or double-gloving to reuce personal exposure. Glvoes should not be considered a substitute for good handwashing practices or skin care. The best barrier is intact skin. Gloves are and will remain an integral component of health care workers' personal protective armamentarium. By identifyng the most important features, benefits, and attributes of a glove, the health professional can select the safest product for both patient and worker.

The amount of bacteria in the water supply delivered by dental units was quantitated by direct-count and plate-count methods. Water samples collected from dental units following various intervals during which the units were not used were serially diluted 10 times. Various dilutions were plated onto trypticase soy agar. Samples were prepared for quantitation by the total direct-count and the total viable-count methods. The number of bacteria recovered from the dental unit water samples as quantitated by the total direct-count and total viable-count methods was 0.5 to 1.0 log greater than that revealed by the plate-count method. Direct-count methods are more rapid and more accurate than the plate count. Direct-count methods offer potential as a routine, accurate, and rapid method of standardizing the enumeration of bacteria in the water supply of dental units. The plate count remains a valuable method for characterizing bacterial isolates.

A glass-ionomer-silver cermet cement was comparatively evaluated with a conventional fissure sealant for such mechanical properties as compressive strength, tensile bond strength, and wear resistance. The mean compressive and tensile bond strength values of the Ketac-Silver group were found to be significantly lower than those of Delton sealant group. However, the wear percentage in the Delton group was higher than that in the other group. Nevertheless, the results indicated that Ketac-Silver cannot be used as an alternative to bis-GMA resin fissure sealant.

In the clinical part of a two-part study on the use of glass-ionomer-silver-cermet cement as a pit and siffure sealant, 100 children between the ages of 6 and 15 years who had noncarious permanent first molar teeth bilaterally received sealants. One of the teeth was sealed with Ketac-Silver and the other received a conventional fissure sealant (Delton). At the 6-month evaluation, 94 children were examind. The number of the children examined decreased to 86 at the end of 12 months. During both evaluation periods, the percentage of teeth that had completely lost the Ketac-Silver sealant was significantly higher than the same parameter in the Delton-sealed teeth. However, there were no statistically significant differences in the caries incidences between the two groups. Nevertheless, Ketac-Silver cannot be considered an alternative to bis-GMA resin fissure sealant.

Two cases of talon cusp, one in a primary anterior tooth and the other in a permanent anterior tooth, are reported. Because both the patients were asymptomatic, they required no treatment. However, it is necessary to follow up the talon cusp occurring in a permanent tooth because it has been reported to cause a variety of clinical problems needing treatment at a later date.

Maintenance of optimal density of radiographic films is a daily problem in dental practice. Developing solutions for film processing deteriorate over time. Storage conditions are known to influence the durability of developing solutions. Results of the present study indicated that the durability of these solutions may be extended by use of plastic storage bottles with tightly fitting lids that have locking rims.

The purpose of this study was to observe microabraded enamel surfaces after various applications of Prema to evaluate the mineralized, dense outer-enamel layer. The loss of enamel during the manual method was also compared to that resulting from the mechanical method. Twenty-four intact, freshly extracted maxillary incisors were randomly divided into four groups: five applications, 10 applications, 15 applications, and 20 applications. Each group was further subdivided into manual or mechanical application. Round cavity preparations (about 3 mm) were made in the mesial or distal half of the facial surface and obturated to serve as a reference point. The compound was applied for 5 seconds, rinsed with tap water for 10 seconds, and air-dried, and applications were repeated. Manual applications were performed with a Prema Hand Applicator. After the prescribed applications, the teeth were sectioned mesiodistally. Enamel losses were measured by computer image analysis. No statistically significant difference was observed between the manual and mechanical techniques. The sections were further polished down to approximately 100 um thick and examined with polarized and transmitted light microscopy and microradiography. None of the sections showed the highly mineralized region that has been reported in previous studies. The dark superficial region reported elsewhere probably is an artifact caused by the Edge effect of thicker enamel sections.

The present study involved the use of light microscopy to investigate the resin-dentin interface, supplemented with examination by scanning electron microscopy. In vivo specimens were processed for (1) scanning electron microscopic examination of acid-rinsed, highly polished, undemineralized surfaces; (2) light microscopic examination of demineralized paraffin serial sections stained with hematoxylin and eosin and according to the Brown and Brenn technique; and (3) scanning electron microscopic examination of dewaxed paraffin sections. The hybrid layer, which was clearly defined with Brown and Brenn stain and confirmed with the acid-rinsed undemineralized specimens, measured up to a depth of 8 jm from the pulp. The resin strings had a rough outer surface and exhibited the appearance of a solid core as they traversed the hybrid layer, becoming gradually hollow within the tubules. This study confirmed the presence of a dentinal hybrid layer within 0.5 mm of the pulp in vivo. The morphology, length, and adaptation of the resin strings were indicative of the degree of wetting with the use of hydrophilic primers.