Time and position‐specific expression of glycosaminoglycans in rat molar cementum related to physiological tooth movement

The role of glycosaminoglycans (GAGs) and proteoglycans during cementogenesis is not known. In this study, we have analysed the temporal and spacial expression of GAGs in the cellular cementum of 10–30 weeks old rats, immunohistochemically using monoclonal antibodies 2B6 and 3B3, specific for chondroitin 4‐sulfate/dermatan sulfate and chondroitin 6‐sulfate, respectively. Both 2B6‐and 3B3‐epitopes were expressed at similar position and time in the rat cellular cementum. Two types of cellular cementum were identified; GAG‐positve and GAG‐negative cementum. The former corresponded to the lightly stained and the latter to the darkly stained cementum in sections stained with haematoxylin and eosin. The GAG‐positive cementum was seen at the distal side of dentine surface and appeared most thick at middle of the apical half roots, whereas the other parts of the cementum were the GAG‐negative. Distribution of GAG‐positive cementum showed changes with age of animals. In 10–15 week old rats, the GAG‐positive cementum occupied most of the cementum layer, covering a thin layer of the GAG‐negative cementum. The cellular cementum of 20–30 week old rats consisted of three layers; GAG‐negative, GAG‐positive and GAG‐negative cementum from dentine to cementum surface, reducing the GAG‐positive area. Because our previous study has demonstrated that the lightly stained cementum is uncalcified, the present result suggests a correlation between calcification and contents of GAGs in the cellular cementum. Further, time‐ and position‐specific expression of GAGs indicates their relation to the physiological tooth movement, which has been known in the rat molars.