Sustained release of calcium hydroxide from poly(dl-lactide-co-glycolide) acid microspheres for apexification

Calcium hydroxide (CH) loaded poly(dl-lactide-co-glycolide) acid (PLGA) microspheres (MS) might be used for apexification requiring a sustained release of Ca²⁺. The aim of this study was to formulate and characterize CH-PLGA-MS. The CH-loaded MS were prepared by either oil-in-water (O/W) or water-in-oil/in-water (W/O/W) emulsion solvent evaporation technique. MS produced by the O/W technique exhibited a larger diameter (18.63 ± 7.23 μm) than the MS produced by the W/O/W technique (15.25 ± 7.37 μm) (Mann–Whitney U test P < 0.001). The CH encapsulation efficiency (E _e) and Ca²⁺ release were calculated from data obtained by absorption techniques. Ca²⁺ release profile was evaluated for 30 days. To know the E _e, the CH-loaded MS were dissolved in 1 M NaOH to release all its content and a Ca²⁺ colorimetric marker was added to this solution. The reagent marked the Ca²⁺ in blue color, which was then measured by a UV–Vis system (650 nm). The percentage of E _e was calculated on the basis of the theoretical loading. The E _e of the O/W-produced MS was higher (24 %) than the corresponding percentage of the W/O/W-produced MS (11 %). O/W- and W/O/W-produced MS released slower and lower Ca²⁺ than a control CH paste with polyethylene glycol 400 (Kruskal–Wallis test). O/W-produced MS released higher Ca²⁺ than W/O/W-produced MS (statistically significant differences; P < 0.05). In conclusion, the CH-PLGA-MS were successfully formulated; the technique of formulation influenced the size, encapsulation efficiency and release profile. The MS were better sustained release system than the CH paste.