A major issue with a complete denture opposing natural teeth is abrasion of the artificial teeth. Natural teeth are composed of enamel, which is significantly harder than the acrylic or resin materials used in denture teeth. This hardness difference leads to accelerated wear and surface loss of the denture teeth when in occlusion with natural dentition. This wear compromises the occlusal vertical dimension, aesthetics, and function of the denture, necessitating frequent adjustments or replacements. Therefore, selecting wear-resistant materials or protecting the denture teeth is critical in such cases.

Reference: Textbook of Prosthodontics, Dr. A. R. Pradeep, 2nd Edition.