investigate the anatomic features of the pulp floor and root canal system in 3 rooted mandibular 1st molars.
•n= 122 mandibular 1st molars Inclusion criteria: native Chinese.
•n= 25 (2 rooted), 20 (3 rooted) mandibular 1st molars.
Inclusion criteria: intact roots.
•To calculate the frequency, each extracted tooth was stored in 10% formalin and its age, sex, side, and root number of the specimen were recorded.
•To study the morphology of the pulp floor. Teeth were cleaned with 5% NaOCl and ultrasonic scaler. Then scanned at fixed resolution using micro CT. Opacity, view angle and magnification were adjusted to study the root canal system.
•Interorifice distance measured between all orifices.
•Angle formed by DBO-DLO and MLO-DLO was measured (fig1).
•Vertucci classification was used.
Most highlighted Results:
•frequency of three-rooted teeth was 31.97%.
•3 rooted teeth had mostly 4 canals, 2 rooted teeth had mostly 3 canals. The third root usually curved severely in proximal view and the lingual edge of the orifice may form dentinal shelf obstructing the DL orifice.
•Grooves were often present between DBO and DLO in the three-rooted first molars. The depth varied with the division level of the third root from the DR.
•significantly longer interorifice distance in distal orifices than mesial orifices 2.93 as shown in Table.3
•(DBO:distobuccal orifice, DLO:distolingual orifice, MLO:mesiolongual orifice)
•Most highlighted Results:
•Mean angle formed by DBO-DLO and MLO-DLO was 75⁰±10 ⁰.
•In both 3 and 2 rooted 1st molars: mesial roots had type II (2-1), while distal canals had type I (1-1)
•DL root rarely has lateral canals, most of the lateral however were found in mesial root of 2 rooted mandibular molar.
•Understanding the anatomy of 3 rooted mandibular 1st molar would aid in both access and instrumentation.