Laboratory study of tissue repair of resin-based endodontic sealers in critical surgical defects

Abstract

Objective: Filling materials should be restricted to the root canal space. However, sometimes it is impossible to control the apical extrusion, in this case, the fate of the filling material and the result of the treatment will depend on its physicochemical properties and biocompatibility. To evaluate the tissue response and bone repair capacity of endodontic sealers that were implanted in the calvaria of Wistar rats, forming the groups (n=16): AH Plus and Sealer Plus, compared to the clot group.

Methodology: On days 30 and 60, the animals were euthanized, the calvaria was removed and processed for hematoxylin-eosin, immunohistochemistry for collagen type I, Picrosirus red and microtomographic analysis. Data were subjected to ANOVA and Tuckey tests (p<0.05).

Results: At 30 days, all groups showed an intense inflammatory reaction (p>0.05). At 60 days, the AH Plus and Sealer Plus maintained an intense inflammatory infiltrate compared to the clot group (p<0.05). We observed immunopositive areas for type I collagen in all groups at 30 days and 60 days (p>0.05). We observed more red collagen fibers for the Sealer Plus compared to the clot group at 30 days (p<0.05). Considering the total fibers, the clot group at 30 days compared to 60 days after surgery showed an increase in the amount of matrix (p<0.05). There were no statistical differences between groups for green and yellow fibers (p>0.05). Regarding morphometric parameters, at 30 days, the newly formed bone volume and number of bone trabeculae were higher in the groups with sealers compared to the clot group (p<0.05). At 60 days, AH Plus and Sealer Plus showed greater bone neoformation compared to the clot group (p<0.05).

Conclusions: Despite AH Plus and Sealer Plus induced an intense inflammatory reaction, they can be considered biocompatible materials, since they allowed bone repair.

Figure 1. Flowchart showing the experimental stages and their order fulfillment

Figure 3. Quantification of collagen fiber bundles by the Picrosirius-polarization method after 30 and 60 days formed in the area next to the defects. Means and standard deviation of birefringence intensity (pixels) measured from the total area of collagen fibers (represented in the gray bars) and yellow, green and red collagen fibers (represented in the bars with the respective colors). Symbols (asterisk or hashtag) indicate a statistically significant difference (p<0.05)

Figure 4. Histomorphometric analysis of the newly formed bone volume (BV/TV%), and the number (Tb.N), separation (Tb.Sp) and thickness of bone trabeculae (Tb.Th) in both experimental periods (30 and 60 days)

Figure 2. Three-dimensional microtomographic images (µCT; 350×) and photomicrographs of sections (HE, Picrosirius red and Immunohistochemical; 695×) of the portions adjacent to the bone defects (D) performed after 30 days and 60 days. Microtomographic images show all area of bone defect created in the rat calvaria (D). The delineated area (white line) shows the region of the HE, Picrosirius red and Immunohistochemical sections in higher magnification. HE photomicrographs sections showed bone neoformation next to the defects of control group and sealers (asterisks); besides a fibrous capsule was juxtaposed to this bone (arrows); many fibroblasts and few inflammatory cells, especially plasmocytes and lymphocytes, were present in this tissue. Picrosirius red section shows a bundle of collagen fibers (red, orange, green) formed in the adjacent bone. Areas immunomarked (immunohistochemical sections) in brown showed the detection nex to the newly formed bone type I collagen that can be seen in the tissue in contact with the newly formed bone (asterisks)