The effect of limonene extract on the adhesion of different endodontic cements to root dentin: an in vitro experimental study.

Objectives: The study aimed to evaluate the effect of limonene extract (LE) on push-out bond strength (BS) to root dentin in endodontically treated teeth. Methods: Single-rooted teeth were selected and instrumented using the reciprocating technique, then divided into three groups based on the final irrigating solution: 2.5% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA), and 5% LE. The roots were further divided (n = 12) and obturated using the single-cone technique with epoxy resin-based (ERB) or bioceramic sealer (Bio-C). After 3 days, the roots were sectioned into 2-mm slices, obtaining two slices from each root third. Push-out BS testing was conducted at 0.5 mm/min, followed by failure pattern and adhesive interface analysis using scanning electron microscopy. Push-out BS data were analyzed by three-way analysis of variance and Tukey post-hoc test (p < 0.05). Results: ERB showed higher BS when irrigated with EDTA (5.0 ± 2.3 MPa) compared to NaOCl (1.8 ± 1.1 MPa) (p = 0.0005), particularly in the cervical third. LE yielded intermediate values without significant differences from the other irrigants (3.5 ± 1.9 MPa) (p > 0.05). For Bio-C, the highest BS was observed in the apical third, especially with LE (9.4 ± 5.0 MPa), differing from other thirds and final irrigating solutions (p < 0.05). Mixed failure patterns were most prevalent, regardless of the irrigant solutions. Conclusions: The combination of LE with Bio-C demonstrated superior BS in the apical third, suggesting its potential as a final irrigating solution in endodontic treatments.