Effect of 10% urea solution on epithelialization of thermally wounded gingiva

Introduction. Urea is the final product of protein degradation secreted in saliva. It has low molecular weight and neutral molecule that can freely diffuse through bacterial wall, mature plaque and extracellular polysaccharides exerting a buffering effect. In the presence of urease, urea is broken down into one molecule of ammonia and two molecules of weak carbonic acid, causing alkalization of the substrate and pH increase. Hydrolysis of urea begins at pH 4-6. In mature plaque with low pH, urea hydrolysis is a compensatory mechanism that opposes pH decrease trying to keep an optimal acidbase balance. This mechanism explains the role of urea in controlling plaque, caries and gingivitis. The aim of this study was to investigate the effect of urea on the quality and speed of epithelialisation of thermally wounded gingiva in rats. Material and Methods. The study included 36 Wistar albino rats, 3-4 months old, divided in three groups (12 in each group). According to the protocol thermal wounding of gingiva was performed in all animals. Wounded gingival epithelial tissue was treated with: 10% urea solution (experimental group), 3% hydrogen peroxide and saline (control groups). The extent and quality of epithelialisation was verified histologically after 3, 5, 8, 11 and 14 days. Results. There was a strong cellular infiltration and stromal edema with no significant morphological differences between groups in the samples analyzed after 3 days. The acceleration of epithelialisation in the experimental group observed in samples obtained after 5 days was evidenced by rapid mitotic division of epithelium and initial covering of defects in both directions. In samples obtained after 8 days, in the experimental group, epithelial defect was covered and in some areas cells were differentiated in vertical direction. After 11 days horizontal coverage of defects as well as accelerated cell differentiation in the vertical direction were noted. Restitutio ad integrum in the experimental group and significant delay in wound healing in the control groups was demonstrated in 14-day samples. Conclusion. Complete epithelialisation of gingiva occurred significantly faster in the group treated with 10% urea solution, than in the control groups treated with 3% hydrogen peroxide solution and saline.