Zirconia crowns are resistant to stains as long as the porcelain remains intact. However, if the porcelain gets damaged, then the crown may stain. Things that can damage the porcelain include highly abrasive toothpastes and brushing technique, tar and other substances found in cigarettes, acidic foods and beverages, eating extremely hard or crunchy foods, using your teeth as an opener, and alcoholic beverages. In most cases if stains do develop, they can usually be removed with porcelain polish during your professional teeth cleaning.