Endodontic anatomy of the root canals of lower incisors.

Ninety lower incisors of known age (18 to 20 yr, 30 to 40 yr and over 50 yr) were grouped into 2 sets of 45 pieces each. Cross sections of the root at 4 levels (coronal, middle and apical thirds and 2 mm from the apex) were employed to study: 1. The shape of the canals 2. The changes in diameter induced by age 3. The correlation at the apex of the maximum diameter of the root canal with the Dzero diameter of endodontic instrument. The results showed that the canal anatomy of lower incisors is not as simple as it appears to be and that it is characterized by the predominance of flat shapes even in the vicinity of the foramen. The statistical analysis showed that the dentin deposits, typically age-associated, are influenced by the morphological changes that take place. A true compensation occurs between the different buccolingual and mesiodistal diameters, particularly in the vicinity of the apex, to guarantee irrigation in old age and avoid calcification fo the canal. The correlation between the maximum diameter of the canal at 2 mm from the apex and the Dzero diameter of the instruments evidenced the difficulties involved in adequate apical preparation of these teeth, regardless of age.