- Masticatory ability and performance are commonly used summary measures of masticatory function. Numerous studies have shown that masticatory ability and performance are diminished in subjects with mutilated dentitions, as well as in subjects wearing complete or removable partial dentures. Although not as potent a factor as the mutilated dentition, malocclusions also produce functional impairment. Class III malocclusions create the greatest functional impairment, followed by Class II and Class I malocclusions, respectively. Open-bite and cross-bite malocclusions also cause functional limitations. For individuals with complete dentitions, masticatory performance is directly related to areas of interocclusal contact and near contacts; this relation best explains why individuals with malocclusions have greater functional deficits. The ability to efficiently and effectively break down foods is important because the size of food particles swallowed has been related to digestion and evacuation times. In older individuals with missing teeth and dentures, impaired masticatory performance has been linked to gastrointestinal disturbances and malnutrition. 2006 Elsevier Inc. All rights reserved.