The most reliable criteria in Gustafson method of age estimation is -
The canals in dentin become wide and are filled with mineral so that they become translucent gradually . It is not seen until thiy years of age. It is the most reliable criteria in Gustafsons method. Ref:Dr . Narayana Reddys Synopsis of Forensic Medicine & Toxicology 27th edition pg. 37.
Attrition
Secondary dentin deposition
Transparency of root
Cementum apposition
Identification