To evaluate the efficacy of a prototype root canal dressing containing surface pre-reacted glass-ionomer (S-PRG) fillers on repairing induced periapical lesions in a rat model. Calcium hydroxide [Ca(OH) ] was applied as a comparison in the healing process.
The pulp chambers of the maxillary first molars in 64 male Wistar rats aged 16 weeks were opened to induce periapical lesions. After 28 days, the mesial canal of each tooth was prepared, irrigated with 2.5% sodium hypochlorite (NaOCl) only (control group: irrigation) or followed by the respective dressing [Ca(OH) group, irrigation + Ca(OH) ; S-PRG group, irrigation + S-PRG], and restored with composite resin for 3 or 7 days (10/group). Four rats with healthy molars were used as blank controls. Descriptive analysis of the periapical radiographs, haematoxylin and eosin staining, and immunohistochemical observation were performed 3 and 7 days after treatment. The periapical gray value, CD68 macrophages, and osteoclasts (cathepsin-K) were quantified and statistically analyzed with Tukey’s honest significant difference test. A significant difference was achieved when p values were < 0.05.
S-PRG and Ca(OH) dressing were associated with increased periapical gray value and inhibited osteoclast activity at 3 and 7 days; a significant difference in radiographic results and the number of osteoclasts was obtained at 3 and 7 days compared with the control group (p < 0.05). Reparative tissue was observed histologically in the space of the periapical resorbed necrotic area after S-PRG and Ca(OH) treatment for 3 and 7 days. The number of macrophages was significantly decreased at 3 and 7 days in the S-PRG and Ca(OH) specimens when compared with the controls (p < 0.05).
In a rat experimental model, the S-PRG root canal dressing was comparable to Ca(OH) in promoting experimentally induced periapical lesion healing. S-PRG paste has the potential to be used as an alternative intracanal dressing in teeth with apical periodontitis.

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