The fibrillar structure of cement lines on resorbed root surfaces of humanteeth

The cement lines between reparative cementum and resorbed dentin or cementu m in human teeth were observed by light microscopy and scanning electron mi croscopy combined with NaOH maceration. The NaOH maceration was used to rem ove interfibrillar substances and to observe the fibrillar architecture of the cement lines directly. Light microscopy showed that the cement lines we re rich in proteoglycans with mucopolysaccharides, but deficient in collage n fibrils. The cement lines were artificially broken after treatment with h yaluronidase, which digests some of the mucopolysaccharides, but digests no collagen fibrils. Scanning electron microscopy showed that fibril intermin gling occurred only in some places between reparative cementum and resorbed tissue. These findings suggested that the proteoglycans in cement Lines me diate the attachment between new and old mineralized tissue.