Periapical Bacterial Disinfection is Critical for Dental Pulp Regenerative Cell Therapy in Apical Periodontitis in Dogs

Abstract

Background Application of pulp regenerative cell therapy for mature teeth with periapical lesions is a critical clinical challenge. The bacterial infection in inaccessible location within the root canal system and in the periapical lesions could cause resistance and impediment, leading to limitations in successful therapy. Thus, the aim of this study was to examine the effect of residual bacteria on the outcome of pulp regeneration in mature teeth with apical periodontitis in dogs. Methods Periapical lesions were induced in 32 root canals of 4 dogs in two different models in severities, model A and model B. Model A (moderate infection): the canal exposed to the oral cavity for 2 weeks and then closed for 2 weeks. Model B (severe infection): the canal exposed to the oral cavity for 2 months and then closed for a few months. All root canals were irrigated with 6% sodium hypochlorite, and 3% EDTA and further with 0.015% levofloxacin containing nanobubbles, which was also used as an intracanal medicament. The aseptic conditions were examined by bacterial anaerobic culture and/or PCR analyses. The root canal treatment was repeated several times, and allogeneic dental pulp stem cells were transplanted into the root canals. The radiographic evaluation of periapical lesions was performed by cone-beam computed tomography before the first treatment, just after cell transplantation, and after 2 months and 6 months in both model A, model B, respectively. The animals were then sacrificed and the jaw blocks were harvested for histological and histobacteriological evaluations of pulp regeneration and periapical tissue healing. Furthermore, the DiI-labelled DPSCs were transplanted into the root canals after complete disinfection (n = 4) or without root canal treatment (n = 4) in the apical periodontitis model (model A) in one dog, and cell localization was compared 72 h after transplantation. Results In 8 out of 12 canals from model A, and 10 out of 15 canals from model B, pulp regeneration with good vascularization, innervation, and a significant reduction in the radiolucent area of the periapical lesions were observed. However, in the other 4 canals and 5 canals from model A and model B, respectively, no pulp tissue was regenerated, and inflammation in the periapical tissue, and external resorption or healed external resorption were detected. The presence of residual bacteria in the periapical tissues and severe inflammation were significantly associated with inhibition of regenerated pulp tissue in these 9 unsuccessful canals (P < 0.05, each) (OR = 0.075, each) analyzed by multiple logistic regression analysis. For cellular kinetics, transplanted cells remained in the disinfected root canals, while they were not detected in the infected root canals, suggesting their migration through the apical foramen under the influence of inflammation. Conclusions For successful pulp regeneration in apical periodontitis, it is essential to completely disinfect the periapical tissue, suppress inflammation, and allow the transplanted cells to remain in the root canal and promote regeneration in the mature teeth.

Bioactive Endodontic Hydrogels: From Parameters to Personalized Medicine

“…The added biomolecules play a major role during the release from the endodontic space to the periapical environment [ 65 , 66 , 67 ]. Parameters of the released biomolecules, such as size, shape, charge, and solubility in hydrophilic or hydrophobic media, play a critical role in their bioactivity and bioavailability, as they modify its ability to diffuse through and interact with the hydrogel and the surrounding host tissue [ 18 , 68 ].…”

“…The composition of the periapical host tissues can also influence the release of molecules from an endodontic material (hydrogel) [ 65 , 67 ]. Each molecule, according to its own physicochemical properties, will have varying affinities depending on the tissue, hydrogel, pH, etc.…”

“…Controlled delivery with a vector, such as a nanoparticle for example, adds a great number of parameters, such as size, solubility, or shape, that complexify the understanding of the release even further and, therefore, the bioactivity of the loaded bioactive molecule. Although the physicochemical characteristics of biomolecules are often well documented in the literature, they need to be taken into consideration in the specific context of encapsulation in a hydrogel, as well as for the patient-specific morphology of the endodontic space to control the in situ and released bioactivities [ 57 , 65 , 66 , 67 , 86 ]. Encapsulating an active molecule in a hydrogel makes the hydrogel a de facto vector, and the release of an active molecule with a specific release profile causes them to become not only scaffolds but also galenic objects.…”

Investigation of the early apical release from endodontic hydrogels: A 3D printed model

“…Regenerative Endodontic Procedures (REPs) aim at recreating a pulp-like tissue in the endodontic space to replace the current approach that uses gutta-percha (Ducret et al, 2017). This strategy has been studied in clinic for decades, but it was suggested in reports that numerous parameters, such as biological and clinical, could greatly vary between patients and influence its success (Iohara et al, 2023;Widbiller et al, 2022). Various studies and reviews in this field were already been published, amongst them, a long list of biomaterials, including fibrin, PEG derivatives, gelatin derivatives and others, that could be used to fulfil the endodontic space and act potentially as scaffolds for cellular components (Leveque et al, 2023;Nageh et al, 2018;Namazi et al, 2023;Widbiller et al, 2022).…”