Study of mandibular premolars cross section with cone beam computed tomography

Abstract

INTRODUCTION: Mandibular premolars are known for the complex nature of their root canal
configuration. Generally, the configuration of the single canal in lower premolars with one root canal is
narrow and long. Currently we have more precise diagnostic tools such as Cone Beam Computed
Tomography to evaluate the morphology of the canals in the three planes of space, with less radiation than
a conventional tomography.
OBJECTIVE: is to study the cross section of the human mandibular premolar canals, with a single root
canal.
MATERIAL AND METHODS: 120 human lower extracted premolars were studied. The specimens were
studied by means of CBCT, with an exposure time of 15 seconds, 90KV 3.2mA, dose 1098mGy.cm² voxel
size 150x150x150μm, with a Carestream 8200 tomograph. From the total sample, only the premolars with
a single canal were selected through the CBCT. They were analyzed in perpendicular cuts to the long axis
of the tooth (axial) In each tooth the diameter in the canal were measured in the buccolingual and
mesiodistal direction (expressed in milimeters) in the three thirds: cervical, middle and apical.
Subsequently, the morphology of the canal in the axial sections was analyzed, in the three thirds mentioned
above, classifying them as: circular, oval, long oval and flat shape. The quantitative variables were
represented in tables by means of average and deviation, while the qualitative ones with frequencies and
percentages. Friedman tests and chi-square uniformity tests were performed. The soft RMedic and Infostat
were used. In all cases the level of significance was 5%.
RESULTADOS: El 1.22% of the cases presented a circular canal and 4.88% oval throughout its route.
93.9% of the sample presented different morphologies in the 3 thirds of the canal: LCC in 21.95%, followed
by ACC with 20.73% and OCC with 10.98%. Were observed a predominance of circular canals in 84% in
the apical third and 56% in the middle; oval in the middle third in 31.71% and flat in the cervical third
37.8%. The average diameter of the circular canals at 3 mm from the apex was 0.55 mm2. In cervical the
average diameter was 2.58 mm in BL and 0.83 mm in MD and in the middle third 1.29 mm in BL and 0.82
mm in MD.
CONCLUSIONS: The lower premolars with a single canal presented different morphologies in three thirds.
The predominance of anatomy was Elongated or Flattened in the Cervical third (37.80%) and predominance
of Circulars in The Middle (56.10%) and Apical (84.15%). This type of canals, which vary their
morphology longitudinally, can be a real challenge for their instrumentation, irrigation and sealing.