A periodontist repairs and maintains the natural tissues that support the teeth and mouth. They understand how to diagnose and treat gingival conditions such as gingivitis, and they can perform advanced gum surgeries such as crowns, bridges and veneers. A periodontist can also identify and treat diseases affecting the teeth, such as caries, dental plaque and cavities. They have a great understanding of the complex interactions between the oral cavity, its immune system, the gums and its supporting structures. A periodontist can work on all parts of the mouth, including the tongue, lips, cheeks, palate and hard and soft palates.