William M. Johnston

Learn More
Judgments of appearance matching by means of the visual criteria established by the United States Public Health Service (USPHS) and by means of an extended visual rating scale were determined for composite resin veneer restorations and their comparison teeth. Using a colorimeter of 45 degrees/0 degrees geometry and the CIELAB color order system we used the(More)
The selection of an appropriate material that duplicates the appearance of natural tooth structure is very important in restorative dentistry. Photometric and colorimetric analysis techniques offer great potential as a tool for aiding in the duplication process. The degree to which these techniques will be useful depends on the accuracy and precision with(More)
Certain variables were tested for their influence on the color of ceramic metal restorations. The variables included firing temperature, condensation technique, modeling liquid, and brand of porcelain. In addition, the color of different nominal shades was compared. The color was measured with a Minolta CR-121 small-area colorimeter. The small (7 mm2)(More)
The contrast gloss and the average roughness were measured for four commercial composite filling materials. Using a factorial design, each material was subjected to four available finishing methods. A significant difference was found in the contrast gloss among finishing methods, and a significant linear regression is given which relates the inverse of the(More)
STATEMENT OF PROBLEM Limited studies have indicated that an alternative small color difference formula would be more appropriate for use in dentistry. PURPOSE The purposes of this study were to determine which color difference formula provides a superior degree of fit for judgments of perceptibility and acceptability and to determine if different groups(More)
Tooth color change was monitored after a single, in-office bleaching technique using a colorimeter. Twenty young adults participated in the double-blind study at The Ohio State University College of Dentistry. Half of the participants had their maxillary anterior teeth bleached and half were controls. By one month, the large initial color change was(More)
The objectives of this study were: (i) to determine variability among colour parameters of five different ceramic crown systems; and (ii) to measure the effect of using coloured luting agents on restoration colour. The crown systems studied were Cerestore, Dicor, Hi-Ceram, Renaissance, and Vitadur-N. Five crowns for each system were made according to(More)
PURPOSE Curvature of the posterior border of the mandibular ramus at the occlusal plane has been described as a morphological trait for males. Controversy over the accuracy of this method remains among researchers; studies employing similar methods report accuracy rates for successful gender identification ranging from 59% to 99%. This blind study assessed(More)
Sintered samples of modifying porcelains of various colors and manufacturers were analyzed using reflectance spectrophotometry. Color designations are reported according to practices of the Commission Internationale de l'Eclairage (International Commission for Illumination), and color names were assigned based on a method developed through a joint effort of(More)
Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASAÕs scientific and technical information.(More)