Inhibitory effects of citrus lemon oil and limonene on Streptococcus sobrinus - Induced dental caries in rats

Objective: This study aimed to examine and compare the anti-caries effects of citrus lemon oil (CLO) and limonene in rats.

Methods: The minimal inhibitory concentrations of CLO and limonene were measured using the disk diffusion method. The rats were infected with Streptococcus sobrinus and assigned into four groups: (1) Chlorhexidine, (2) CLO, (3) limonene, and (4) distilled water (H₂O). The total cultivable microbiota and Streptococcus sobrinus in the mouth of the rats were counted, and the caries lesions were measured by Keyes' scoring and DIAGNOdent examination.

Results: The minimal inhibitory concentrations of CLO and limonene against Streptococcus sobrinus were 4.50 and 21.00 mg/mL, respectively. The chlorhexidine group had the lowest total microbiota counts (p < 0.05), while there were no significant differences among the CLO, limonene and H₂O groups (p > 0.05). The proliferation of Streptococcus sobrinus was remarkably inhibited by chlorhexidine, limonene and CLO (p < 0.05). The Keyes' scoring and DIAGNOdent results indicated that the caries lesions were reduced in the CLO and limonene groups compared to that of the vehicle control group (p < 0.05). There was no significant difference between CLO and limonene (p > 0.05).

Conclusion: Limonene and CLO have similar anti-caries abilities in a bacteriostatic manner in vivo.

Keywords: Anticaries; Citrus lemon oil; DIAGNOdent; Keyes’ scores; Limonene; Streptococcus sobrinus.