Post-academic dental specialties 15. Prevention of coronal leakage after placement of lining cement One of the main origins of unsuccesful endodontic treatment is coronal leakage. In the prevention of coronal leakage a good sealing restoration seems mandatory. The effect of 2 types lining cement used as coronal barrier on filled root canals was studied over time. Fifty extracted human canines were prepared and filled by gutta-percha with a quantifiable initial coronal leakage. After placement of the lining cements in 2 groups of 20 canines, leakage was assessed at 96 hours and at 26 weeks and compared with the leakage in a control group of 10 canines. Placement of a coronal barrier of lining cement on the orifice of the root canal after endodontic treatment revealed a significant reduction of coronal leakage. In this study leakage decreased over time.