Definition of "cementum"

From a purely anatomic standpoint, root cementum is part of the tooth, but also part of the periodontium.

2005, Herbert F. Wolf, Klaus H. Rateitschak, Periodontology, page 14

Cementum is the least known calcified tissue in vertebrates (Bosshardt and Schroeder 1996) and several questions about cementogenesis have not yet been answered.

2007, Ermanno Bonucci, Biological Calcification: Normal and Pathological Processes in the Early Stages‎, page 245

Whether epithelial cells from Hertwig's sheath contribute to initial cementum formation is controversial as has already been discussed in Chap. 1.

2007, Pieter Johannes Slootweg, Dental Pathology: A Practical Introduction‎, page 8