The collagen density was determined in tissue sections stained with Mallory’s aniline blue.16 Histological sections
were analyzed under a standard microscope equipped with digital camera. The colour images generated by a camera were transferred to a microcomputer and analyzed with mathematical morphology software (WinROOF; Mitani Co., Fukui,
Japan). Measurements were performed in standard areas (0.05 mm 0.05 mm each) subjacent to the junctional epithelium.