Mastication

Abstract: This review describes the patterns of mandibular movements that make up the whole sequence from ingestion to swallowing food, including the basic types of cycles and their phases. The roles of epithelial, periodontal, articular, and muscular receptors in the control of the movements are discussed. This is followed by a summary of our knowledge of the brain stem neurons that generate the basic pattern of mastication. It is suggested that the production of the rhythm, and of the opener and closer motoneuron bursts, are independent processes that are carried out by different groups of cells. After commenting on the relevent properties of the trigeminal and hypoglossal motoneurons, and of internuerons on the cortico-bulbar and reflex pathways, the way in which the pattern generating neurons modify sensory feedback is discussed.

Abstract: IMPLE, reliable methods for measuring masticatory function would be useful aids in evaluating the success of dental restorative procedures. One goal of dental restoration is to improve the masticatory function of patients who have lost teeth. It is surprising how little is known by the dentist concerning his achievement of this goal. Current practices are based on the satisfaction of the patient or the fulfillment of certain theoretical and arbitrary standards that have become accepted because of the clinical experience of their proponents. Tooth structure is replaced wherever it has been destroyed; occlusal surfaces are carved to provide considerable contact with opposing teeth and to approximiate ideal tooth form. The completed restorations are never checked objectively for their masticatory function and there are not even data to prove that the ideal tooth form will provide best function under all conditions. For example, flatter cusps might be advantageous in masticating processed foods, and the ocelusal shape might be modified to compensate for missing teeth. Perhaps contact area should be diminished on teeth which cannot tolerate forces readily, and the normal occlusal pattern might be discarded entirely for denture teeth among cases where forces are severely limited. Several investigations of this topic have appeared in the foreign literature but only a few in English, and there is no agreement concerning the test to be used. The procedures are complicated and vary in the foods and technics that are recommended. Investigators have been unable to agree as to which of several criteria should be used and have been puzzled by the wide variation in performance among persons having the same numbers and types of missing teeth. Most authors agree concerning the principles to be employed in designing a function test for mastication. The test should be selected from foods that are normally consumed. These foods should offer the proper degree of difficulty, permitting a normal dentition to receive a high rating and a deficient dentition, a poor rating. Any selective action that is performed by the normal and is missing from the deficient mouth should be taken into account. A certain degree of precision should be obtained, and the method should be simple, rapid, and inexpensive. Masticatory function tests have been described by Lehman,1 Gaudenz,2 Christiansen,3 Schutz,4 Paulsen,5 Claussen,6 Balters,7 Ascher,8 Gelman,9 Juul,10 Ono,'1 Sognnaes,12 and Dahlberg.13 A variety of test foods were proposed, including Spanish hazel nuts, Brazil nuts, sweet almonds, boiled egg white, potato, apple, carrot, bread, zwiebach, turnip, coconut, meat, cracked corn, and

Abstract: Summary During chewing, food is reduced in size, while saliva moistens the food and binds the masticated food into a bolus that can be easily swallowed. Characteristics of the oral system, like number of teeth, bite force and salivary flow, will influence the masticatory process. Masticatory function of healthy persons has been studied extensively the last decades. These results were used as a comparison for outcomes of various patient groups. In this review, findings from literature on masticatory function for both healthy persons and patient groups are presented. Masticatory function of patients with compromised dentition appeared to be significantly reduced when compared with the function of healthy controls. The influence of oral rehabilitation, e.g. dental restorations, implant treatment and temporomandibular disorder treatment, on masticatory function will be discussed. For instance, implant treatment was shown to have a significant positive effect on both bite force and masticatory performance. Also, patient satisfaction with an implant-retained prosthesis was high in comparison with the situation before implant treatment. The article also reviews the neuromuscular control of chewing. The jaw muscle activity needed to break solid food is largely reflexly induced. Immediate muscle response is necessary to maintain a constant chewing rhythm under varying food resistance conditions. Finally, the influence of food characteristics on the masticatory process is discussed. Dry and hard products require more chewing cycles before swallowing than moist and soft foods. More time is needed to break the food and to add enough saliva to form a cohesive bolus suitable for swallowing.