Effects of Hibiscus sabdariffa calyx extract on IL-10, TNF-α, and woven bone during orthodontic relapse

Tooth relapse occurs after orthodontic treatment. Bioactive chemicals in Hibiscus sabdariffa calyx extract (HS-CE) can protect bones and prevent inflammation. This study evaluated the effects of HS-CE on interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α) expression, and woven bone formation during orthodontic relapse.

Sixteen male Wistar rats underwent orthodontic tooth movement of the left maxillary first molar using a 10 g nickel-titanium closed-coil spring for 14 days, followed by a 7-day retention phase. Rats were divided into two groups (n = 8): phosphate-buffered saline (PBS) and HS-CE. During retention and the subsequent 7- and 14-day relapse phases, each group received daily intrasulcular applications of PBS or HS-CE (0.01 mL). Relapse distance was measured as the percentage return of tooth movement relative to initial separation. Four animals per group were euthanized at each time point, and maxillary tissues were processed for histological evaluation of woven bone and immunohistochemical staining of IL-10 and TNF-α. Data were analyzed using one-way analysis of variance and independent samples t-tests, and Tukey's post hoc test was applied for multiple comparisons (p < 0.05).

HS-CE significantly reduced relapse distance at days 7 and 14 (p < 0.05). IL-10 expression was elevated on day 7 (p < 0.05) and day 14 (p < 0.001), whereas TNF-α was suppressed on both days (p < 0.01; p < 0.001). The woven bone area was greater in the HS-CE group (p < 0.001).

HS-CE enhanced IL-10 expression, suppressed TNF-α, increased woven bone formation, and reduced the relapse distance, highlighting its potential as a natural adjuvant to improve post-treatment stability.