Characterization of dental pulp defect and repair in a canine model

To explore a relationship between the size of pulp chamber perforation and reparative dentin formation in a canine model.

Pulp defects were created in the pulp chambers of maxillary and mandibular premolars (N = 64) in 17 healthy mongrel dogs in three different sizes (diameter/depth: 1/1, 2/1, and 2/2 mm3) with sterile round burs under general anesthesia. The perforations were immediately capped with hard-setting calcium hydroxide (CH) in the control group or sealed with Teflon membrane (TM) in the experimental group, followed by restoration with reinforced zinc oxide eugenol cement in vivo. Seven and 30 days after pulp chamber perforation and restoration all treated and control premolars were extracted and prepared for histomorphometric and statistical analyses.

Reparative dentin formation was more pronounced for defect sizes up to 2/1 mm3 when treated with CH, and completely bridged the surgically created dentin defects only after 30 days. However, reparative dentin upon CH treatment failed to completely bridge pulp chamber exposure for 2/2 defects. By contrast, TM treatment only yielded mild reparative dentin bridging for defects up to 1/1, but not for either 2/1 or 2/2 defects at 30 days. Inflammatory responses of the exposed dental pulp tissue were more robust with the TM group than with the CH group. Thus, dental pulp tissue possesses a capacity for spontaneous repair by the formation of reparative dentin in this preclinical model, but only up to a defect size of -2 mm in diameter and 1 mm in depth. All observations are based on 30 days post-treatment in the canine model. These findings may serve as baseline for regenerative endodontic studies.