Objectives: To investigate the effects of denture relining materials on oral mucosa in vivo in a rat model. Methods: Denture-like appliances covering the palate in Wistar rats were relined with a resilient soft lining material and a hard ‘chairside’ relining material. The effects on the palatal epithelium were studied by quantitative analysis using computerized planimetry. Results: The relining materials caused an increase in the thickness of the keratinized layer, while not increasing the total epithelial thickness. Conclusions: Relining materials are not totally without effect on oral mucosa. Further in vivo research is indicated.