Quintessence International, 04/1992

A new technique for the fabrication of composite resin direct veneers is presented. In this technique, a transparent acrylic resin matrix is fabricated before preparation of the facial surface of the tooth, to allow the adequate reproduction of contour, shape, and surface texture originally exhibited by the tooth. Advantages, as well as limitations, of the procedure are also presented.

A patient presented with severe loss of enamel on the palatal surface of the maxillary anterior teeth, resulting from attrition. After correction of the mandibular occlusal position, the palatal defects were restored with metal partial crowns cemented with an adhesive cement. One of the six restorations dislodged during 4 years of observation, but was replaced successfully.

Lichen planus is an inflammatory dermatosis affecting the skin and mucous membrane.

The use of protective mouthguards in athletes has proven to be an effective and inexpensive means of preventing traumatic injuries to the teeth and supporting structures. Of the three general types of mouthguards available currently, the custom-fabricated type is considered superior to stock and mouth-formed protectors. A new technique is introduced for the fabrication of custom-made mouthguards with light-curing urethan diacrylate material.

Results of this study showed no correlation between the thickness or amount of reparative dentin deposited and the type of dental restorative material placed at either 5 or 8 weeks in controlled Class V cavity preparations in monkey teeth. Factors such as preparation trauma from the bur, operator hand instrumentation, and microleakage of bacterial toxins played a greater role in the stimulation of reparative dentin than did material irritation or toxicity. Some differences in the thickness of the reparative dentin deposited were noted when teeth were grouped according to the amount of remaining dentin.

The marginal adaptation of fired ceramic inlays prepared by three dental technicians in two ceramic materials was evaluated in vitro. The thickness of the sealing gap varied between 46.4 and 57.6 um, and the percentage of margina l ceramic defects ranged between 8.6% and 25.0% of the total inlay circumference. The incidence of marginal defects increased in areas of complex occlusal morphology. Dif ferences observed in inlay adaptation were realted to the technician rather than to the material used. The accuracy of ceramic inlays was comparable to that of metallic and porcelain-fused-to-metal crowns with butt-joint margins and fell within the range of clinically acceptable adaptation.

The corrosion behavior of 12 high-gold, low-gold, palladium-silver, and nickel-chromium alloys was tested using electrochemical techniques. A 22-carat-gold alloy was used as a control. High-gold alloys were extremely resistant to corrosion, but the resistance of the alloys decreased with decreasing nobility (from high-gold, to palladium-silver, to low-gold, to nickel-chromium alloys). Tests were also made to determine the type of corrosive attack; nickel-chromium alloys exhibited pitting, and palladium-silver alloys demonstrated the selective dissolution of the silver-rich phases. The corrosion resistance of noble alloys was far superior to that of nickel-chromium-based alloys; therefore, the palladium-silver alloys, which have a moderate price range, may be more suitable for restorations

This investigation evaluated the operating characteristics of a recently introduced tooth dryer and its effect on the bond strength of three composite resins to etched enamel. The effect of varying air pressure, distance from the tip of the tooth dryer, and distance laterally from mid-air stream on temeprature were measured using a rapid-response thermocouple. Specimens were subjected to shear forces either immediately after bonding or after 5 days of water stor age. The air stream required from 32 to 41 seconds to reach maximal temperature; however, more than 90% of the maximal temperature was obtained in 20 seconds. There was an increase in temperature with increased air pressure and a decrease in temperature with increasing distance from the tip. The temperature dropped rapidly laterally from the center of the air stream. The shear bond strength measurements were significantly higher for the specimens prepared using the tooth dryer for one composite resin tested immediately after bonding; there was no statistically significant difference for the other resins. The effect of warm air on the shear bond strength of composite resins to etched enaeml may be dependent on bonding and testing.