Hasegawa T, Takenaka S, Wakamatsu R, et al. - Using confocal laser scanning microscopy, researchers developed a technique to build sequential slices, allowing the fluorescent visualization of bacterial viability in all parts of infected dentin. By comparison with a dye bleaching test, the reliability of this technique was verified. Without decalcification, horizontal sequential sections that preserve the 3-dimensional bacterial distribution and their viability could be made. The time of treatment contributed to the penetration of sodium hypochlorite into dentinal tubules, whereas temperature did not affect the penetration significantly. The judgement was compatible with that of a dye bleaching test by confocal laser scanning microscopic analysis. Findings suggested that the horizontal sectioning method has the advantage of sequential sections being created, allowing information to be imaged at each portion.