Quintessence International, 01/1991

The interest of patients in vital tooth bleaching has created a demand for treatment. However, few objective data are available to help determine the number of bleaching appointments necessary and the lightening that can be expected. The purpose of this study was to measure color changes in bleached extracted teeth and compare these to control groups. Group A was etched and bleached with 35% stabilized hydrogen peroxide. Group B was treated the same as group A, but the bleaching solution was replaced with distilled water. Group C was not treated, but was stored in water. Mean color difference after one treatment was 3.33 for group A, 1.67 for group B, and 0.48 fo r group C. After six treatments, the overall color difference was 3.82, 2.41, and 1.38 for groups A, B, and C, respectively (P .01). Color changes beyond those found after the first treatment were small, suggesting that there was little benefit in repeated bleachings under the conditions of this study.

In Class I malocclusions, when the only complaint is the localized crossbite of a premolar, resulting from a mild shortage of space, correction can be simply undertaken. Adams clasps and an expansion screw are incorporated ionto a simple removable appliance designed to provide space to align the malpositioned tooth, which is then guided into the line of the arch by a pience of elastomeric thread stretched between the Adams clasps.

Two cases in which tooth splinting was required after traumatic dental injuries are documented. In each patient, an acid-etch-retained composite resin/ligature wire splint was used to stabilize displaced teeth after they were replaced into their proper positions. The step-by-step splinting technique is described, and the rationale for the method is reviewed.

Tissueward movement of the free-end saddle of a removable partial denture during function takes place around the most distal fulcrum created by the most mesial rests. Displacement because of sticky foods takes place around the fulcrum created by the most distal rests. These and other factors affecting displacement of the free-end saddle removable partial dentures are discussed, and designs intended to increase retention are presented. The forces applied to the most anterior and posterior axes of rotation can be calculated mathematically to reveal the hazards of a too-short lever arm in combination with a strong retentive clasp system.

A technique employed in China to simplify the fabrication of complete dentures is described. Prefabricated dentitions (an alignment of teeth en bloc with little denture base) are used instead of arranging individual teeth into an arch. This procedure can be performed intraorally without articulator mounting. It is economical and saves time. The results of clinical application of this technique are presented.

Eighty-eight handmade microscope slides prepared by G V Black are discussed. Black sectioned tissues using a homemade microtone and razor blades. Different sections of the same material were stained with various stains or double stained. Because of the importance of Black's writings, it was interesting to find slides that he prepared, to try to compare them to his publications, to study the way in which he obtained information, and to find the conclusions he drew from his experiments.

The object of this investigation was to assess the degree of marginal leakage around V-shaped cervical glass-ionomer cement restorations and compare it to that around composite resin restorations. Three different glass-ionomer cements and one composite resin control were assessed by means of dye penetration. Severe microleakage at the occlusal margins was found in 70% of the glass-ionomer cement restorations, but in only 10% of the composite resin restorations. A considerable amount of dye penetration was observed at the cervical margins of all restorations, including the controls. None of the glass-ionomer cements tested showed superiority in preventing marginal leakage occlusally or gingivally.

It has been advocated recently that etching times of enamel be reduced from 60 seconds to as low as 15 seconds. However, the minimal etching time needed to achieve adequate retention of composite resin to enamel has not been identified. In this study, an attempt was made to find the minimal enamel-etching time that still allowed adequate bond strength of composite resin to enamel surfaces. Adequate bond strength was defined as equivalent to the bond strength established for the conventional 60-second etch. Results seemed to indicate that a 5-second etch was sufficient to allow adequate bond strength; however, further study is required to determine the effects of short etching times on microleakage.

Four polyvinyl siloxane impression materials and 14 modified Type IV dental stones were evaluated for their abilities to reproduce surface detail. Each combination of impression material and dental stone was used to duplicate a 20-um-wide line. Surface detail reproduction was observed by two paired-rater groups. The line was reproduced in all impression material specimens, but in only 32% of the stone cast specimens. Some combinations of impression material/dental stone reproduced the line all or most of the time, but 12 combinations did not reproduce the line at all.

Panavia is a modified phosphate ester of dimethacrylate that purportedly forms a strong bond to tooth structure and to metals. The ability of this adhesive to bond orthodontic brackets to enamel was compared to the bond strengths of a no-mix bracket adhesive and a paste/paste autopolymerizing composite resin. Panavia did not form a bond as strong as that achieved by the bracket adhesive but was stronger than the composite resin.

Aggressive or improper toothbrushing techniques may have a detrimental implact on the gingiva. The purpose of this study was to examine the relationship between chewing sticks (Miswak) and gingival recession. Gingival recession was measured on the mid facial surfaces of the incisors, canines, and premolars in 238 patients presenting for routine dental appointments. All patients had been interviewed previously regarding their oral hygiene habits and use of Miswak. Patients were divided into three groups: Miswak group, toothbursh group, and Miswak/toothbrush group. The Miswak users had significantly more (P - .05) sites with gingival recession than did the toothbrush users. Furthermore, the severity of the recession was significantly more (P - .05) pronounced in the Miswak users than it was in the toothbrush users.