A micro-CT study of the pulp cavity morphology of maxillary fourth premolar teeth in dogs

Abstract

Introduction: The objectives of the present study were (1) to describe the anatomy of the endodontic system of the dog's maxillary fourth premolar tooth (MxPM4) in relation to the morphology of the crown, (2) to determine if variations of the endodontic system exist, and (3) to look at the implications for endodontic treatment.

Methods: Ten MxPM4 were harvested en bloc and scanned using micro-computed tomography (micro-CT).

Results: The morphology of the pulp chamber mostly corresponded with the shape of the crown. Three pulp horns were clearly visible and related to the paracone, the metacone, and the metastyle. Nevertheless, the pulp horns of the metacone and metastyle could be fused, partially fused or distinct. Other pulp projections were also present, but rarely, in the parastyle, the protocone, and the plesioconule. All teeth showed a noticeable angulation of an average of 150 degrees at the coronal third of the mesiopalatal canal.

Discussion: Thus, the most common transcoronal approach for root canal treatment does not allow a straight access to the apex. There were also minor variations in the locations of the canal orifices. This first micro-CT study of the MxPM4 in dogs showed anatomical features and variations of the pulp cavity that have not been described before.

Keywords: dog; endodontic; maxillary fourth premolar teeth; micro-CT; pulp cavity; root canal treatment (RCT).

Figure 1

Landmarks on the crown of the maxillary fourth premolar in dogs according to the Osborn's terminology. Specimen 5–208 is shown. Note that a developmental groove is a term used in dentistry in general. The roots were segmented here to aid illustration of the whole tooth morphology.

Figure 2

Screenshot showing the multiplanar reconstruction in coronal (red window), sagittal (green window), and axial or transverse (yellow window) view in 3D slicer. The blue window shows the 3D reconstruction with the segmentations of the crown and pulp cavity. The coronal and axial slides are shown on the 3D model. We see in the coronal view that the radicular groove did not affect the shape of the D canal. We could appreciate the fusiform shape of the D canal in the sagittal section and the arched floor and roof of the pulp chamber in the axial view.

Figure 3

Example of marks used on specimen 2–108 for measurements of angles and length.

Figure 4

Buccal, mesial and occlusal view, respectively, of each sample's 3D reconstruction with segmentation of the crown and pulp cavity. Note that the images are at the same scale between specimens. The point of view may be slightly different. White arrows indicate accessory pulp horns related to the parastyle, the plesioconule or the protocone.

Figure 5

Coronal point of view of one tooth from all dogs to illustrate difference in orifice locations. BO, Buccal canal orifice; PO, Palatal canal orifice; DO, Distal canal orifice.

Figure 6

Intra-oral radiographs before (A) and after (B) sample collection for tooth 8–208. A sagittal slice (C) of the micro-CT shows replacement tooth resorption (white arrow) and pulp mineralizations or pulp stones (asterisk). The paracone showed abrasion that seemed to be reflected on the pulp horn shape (tertiary dentin).