Calcium hydroxide-loaded nanoparticles dispersed in thermosensitive gel as a novel intracanal medicament.

Aim: Design, produce and assess the viability of a novel nanotechnological antibacterial thermo-sensible intracanal medicament This involves encapsulating calcium hydroxide (Ca(OH)) within polylactic-co-glycolic acid (PLGA) nanoparticles (NPs) and dispersing them in a thermosensitive gel (Ca(OH)-NPs-gel). In addition, perform in vitro and ex vivo assessments to evaluate tissue irritation and penetration capacity into dentinal tubules in comparison to free Ca(OH).

Methodology: Reproducibility of Ca(OH)₂-NPs was confirmed by obtaining the average size of the NPs, their polydispersity index, zeta potential and entrapment efficiency. Moreover, rheological studies of Ca(OH)-NPs-gel were carried out with a rheometer, studying the oscillatory stress sweep, the mean viscosity value, frequency and temperature sweeps. Tolerance was assessed using the membrane of an embryonated chicken egg. In vitro Ca(OH) release was studied by direct dialysis in an aqueous media monitoring the amount of Ca(OH) released. Six extracted human teeth were used to study the depth of penetration of fluorescently labelled Ca(OH)-NPs-gel into the dentinal tubules and significant differences against free Ca(OH) were calculated using one-way anova.

Results: Ca(OH)-NPs-gel demonstrated to be highly reproducible with an average size below 200 nm, a homogeneous NPs population, negative surface charge and high entrapment efficiency. The analysis of the thermosensitive gel allowed us to determine its rheological characteristics, showing that at 10°C gels owned a fluid-like behaviour meanwhile at 37°C they owned an elastic-like behaviour. Ca(OH)-NPs-gel showed a prolonged drug release and the depth of penetration inside the dentinal tubules increased in the most apical areas. In addition, it was found that this drug did not produce irritation when applied to tissues such as eggs' chorialantoidonic membrane.

Conclusion: Calcium hydroxide-loaded PLGA NPs dispersed in a thermosensitive gel may constitute a suitable alternative as an intracanal antibacterial medicament.