The effect of derum (bark of

Background and objectives: Derum, the bark of walnut tree ( Materials and Methods: Following ethical approval, derum extract was applied to the buccal vestibule of New Zealand white rabbits over three different periods (60 days, 120 days, 180 days) and two different protocols were used (daily application and once every 3 days). Accordingly, the animals were divided into four groups (A - daily derum application/B - derum applied once in 3 days/C - Positive control and acetone applied every alternate day/D - negative control), and three batches (I - 60 days/II - 120 days/III - 180 days). The animals were sacrificed, and oral biopsies prepared and examined under light microscope. The magnitude of epithelial changes was evaluated using epithelial atypia index (EAI) based on Smith and Pindborg histological grading system (1969) for epithelial dysplasia. Results: Mild dysplastic changes were detected in animals treated with derum extract regardless of the period of application. Similar results were noted among positive control group, and highest score was recorded in group A followed by group B with high tendency towards long-term derum application. Moderate changes were encountered only in group A that received derum for 180 days. Statistically, long-term derum application (180 days / Batch III in groups A and B), irrespective of the frequency of application, resulted in significantly higher mean EAI scores than all other groups or batches. Conclusion: Based on this study, prolonged and frequent use of derum can induce dysplastic changes in rabbit oral mucosa, ranging from mild to moderate dysplasia. Further studies with extended times of exposure of derum to oral mucosa are recommended to document these adverse effects as an evidence base.