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Background: Fluorescence is the absorption of light by a substance and the spontaneous emission of light in a longer wavelength within 10-8 seconds of activation. Purpose: The purpose of this study was to determine the differences in fluorescence among layered resin composites with a color-measuring spectrophotometer. Materials and Methods: Spectral reflectance and color of five brands of resin composites were measured over a white standard tile according to the Commission Internationale de l'Eclairage (CIE) CIELAB color scale relative to the standard illuminant D65. Human dentin was used as a control; five specimens were made for each group and each specimen was measured three times. An ultraviolet (UV) filter was inserted or removed to exclude or include the UV component of illumination. From the spectral reflectance values, subtraction spectrum by the inclusion and exclusion of the UV component was calculated. Results: Dentin showed a fluorescence peak around 440 to 450 nm. Three of the five resin composites showed fluorescence peaks, and the peak wavelength was 440 to 450 nm. Peak height and peak area varied by the composite. Changes in color (ΔE*ab) caused by the UV component were 1.58 to 2.35, and Δb* values were from -2.20 to -1,49 In composites that showed fluorescence peaks. [ABSTRACT FROM AUTHOR]

A letter to the editor and author's reply to it are presented in response to the article "Quantitative Analysis of Tooth Surface Loss Associated With Gastroesophageal Reflux Disease: A Longitudinal Clinical Study," by Dr. Daranee Tantbirojn and colleagues in the March, 2012 issue.

A preliminary study was conducted on the development of an intelligent dental handpiece with functionality to detect subtle changes in mechanical properties of tooth tissue during milling. Such equipment would be able to adopt changes in cutting parameters and make real-time measurements to avoid tooth tissue damage caused by overexertion and overextension of the cutting tool. A modified dental handpiece, instrumented with strain gauges, microphone, displacement sensor, and air pressure sensor, was mounted to a linear movement table and used to mill three to four cavities in >50 bovine teeth. Extracted sound frequency and density were analyzed along with force, air pressure, and displacement for correlations and trends. Experimental results showed a high correlation (coefficient close to 0.7) between the feed force, the rotational frequency, and the averaged gray scale. These results could form the basis of a feedback control system to improve the safety of dental cutting procedures. This article is written in memory of Dr Hongyan Sun, who passed away in 2011 at a young age of 37.