A Thermosensitive Gel Containing Biodegradable Nanoparticles Carrying Calcium Hydroxide as Antibacterial Intracanal Therapy

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Abstract
Aim: To characterise and evaluate mucoadhesive strength and antibacterial properties of a nanotechnological formulation for endodontic disinfection based on biodegradable nanoparticles dispersed in a thermosensitive gel containing calcium hydroxide (Ca(OH) 2 ‐NPs‐gel). Methodology: Morphology of Ca(OH) 2 ‐NPs‐gel was studied using transmission electron microscopy. Moreover, Ca(OH) 2 ‐NPs‐gel was sterilised using gamma irradiation (25 kGy), and the stability after the sterilisation process was studied by measuring Ca(OH) 2 ‐NPs‐gel average size, polydispersity index, zeta potential and encapsulation efficiency. To assess the ex vivo mucoadhesive strength, extracted single‐rooted human teeth were used to measure the force necessary to separate the formulation from the teeth. In addition, the short‐time stability of Ca(OH) 2 ‐NPs‐gel was evaluated monthly, analysing entrapment efficacy, backscattering and transmittance of Ca(OH) 2 ‐NPs‐gel stored at different temperatures (4°C, 25°C and 37°C). Furthermore, the antibacterial analysis of Ca(OH) 2 ‐NPs‐gel was performed against Enterococcus faecalis inoculated in extracted human single‐root teeth and evaluated by confocal and scanning electron microscopy. Finally, the metabolic activity of bacteria was studied through a resazurin assay to evaluate bacterial survival after treatment. Results: Ca(OH) 2 ‐NPs‐gel owned a round shape and a smooth surface without particle aggregation. Sterilisation did not induce an alteration in Ca(OH) 2 ‐NPs‐gel physicochemical properties and Ca(OH) 2 ‐NPs‐gel presented a high adhesion strength. In addition, 4°C was the best temperature to store Ca(OH) 2 ‐NPs‐gel. Regarding the antibacterial therapeutic efficacy, Ca(OH) 2 ‐NPs‐gel possesses suitable antibacterial properties, indicating that it efficiently reduces bacterial biofilms. Conclusion: Calcium hydroxide‐loaded PLGA nanoparticles dispersed in a thermosensitive gel have been developed, optimised and characterised, obtaining excellent antibacterial properties and achieving bacterial disinfection levels similar to those of commercial formulations.
Funding Information
  • European Regional Development Fund (PROD00141)
  • Generalitat de Catalunya (2022 FISDU 00360)
  • Fundació Bosch i Gimpera (FBG 600324)

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