Adding Two Antimicrobial Glasses to an Endodontic Sealer to Prevent Bacterial Root Canal Reinfection: An In Vivo Pilot Study in Dogs

Abstract

Current endodontic procedures continue to be unsuccessful for completely removing pathogens present inside the root canal system, which can lead to recurrent infections. In this study, we aimed to assess the antimicrobial capacity and tissue response of two inorganic bactericidal additives incorporated into a paste root canal sealer on contaminated root dentin in vivo. An experimental study was performed in 30 teeth of five Beagle dogs. After inducing microbiological contamination, root canal systems were treated by randomly incorporating one of two antimicrobial additives into a commercial epoxy-amine resin sealer (AH Plus), i.e., G3T glass-ceramic (n = 10) and ZnO-enriched glass (n = 10); 10 samples were randomized as a control group. After having sacrificed the animals, microbiological, radiological, and histological analyses were performed, which were complemented with an in vitro bactericidal test and characterization by field emission scanning electron microscopy. The tested groups demonstrated a non-significant microbiological reduction in the postmortem periapical index values between the control group and the bactericidal glass-ceramic group (p = 0.885), and between the control group and the ZnO-enriched glass group (p = 0.169). The histological results showed low values of inflammatory infiltrate, and a healing pattern characterized by fibrosis in 44.4% of the G3T glass-ceramic and 60.0% of ZnO-enriched glass. Bactericidal glassy additives incorporated in this root canal sealer are safe and effective in bacterial reduction.

Keywords: Enterococcus faecalis; apical periodontitis; bactericidal; bactericidal effect; bioactive glass; endodontics; root canal sealer.

Figure 1

Antibacterial activity of glass-filled AH Plus: (a) Samples were used within 20 min after mixing; (b) samples were allowed to set for 48 h in a humid atmosphere at 37 °C; (c) samples were allowed to set for 48 h in a humid atmosphere at 37 °C, and then aged for 5 days in phosphate buffered saline (PBS) at 37 °C. All the assays were conducted in triplicate, each point on the curve is the average of three measures.

Figure 2

Representative picture of hematoxylin and eosin staining of (a) Granulation-like inflammation (×400); (b) mature fibrosis (×400); and (c) inflammatory abscess (×200), developed in the periapical region of samples sealed with ZnO-enriched glass, G3T glass-ceramic, and the control group, respectively.

Figure 3

Representative images (×400) of blood vessel neoformation: (a) Associated with the G3T glass-ceramic study group (lower density); (b) associated with the ZnO-enriched glass study group (higher density).

Figure 4

Microbiological values (log CFU) of the two-week contamination period (“baseline sample”) sample and the study groups. Bars represent standard error.

Figure 5

Relation between additive agents and postmortem PAI values. Plots represent mean values with 95% confidence intervals. Bars represent standard error.

Figure 6

(A,B) Backscattered FE-SEM micrographs; (1,2,3) EDS microanalysis, of the selected spots (red cross with the corresponding numbers) of the dental sealer containing the bactericidal materials, (A) G3T glass-ceramic and (B) ZnO-enriched glass, both located at the delta apical of the canal.

Figure 7

Measurements of the apical lesion of one of the teeth on the axial, sagittal, and transverse planes: (a) The pre-mortem computerized axial tomography (CAT) and (b) the postmortem cone beam computed tomography (CBCT), through the 3D implant planning software.

Figure 8

(a) Image and schematic view of the sagittal plane of one of the teeth after being polished: (1) composite restoration used to fill the access cavity, (2) gutta-percha, (3) Guttacore, and (4) AH Plus dental sealer containing the bactericidal G3T glass-ceramic located at the apical position. (b,c) field emission scanning electron micrographs at different magnifications of the apical section.