Masticatory force or force of mastication is defined as a force, which is created by the dynamic action of the masticatory muscles during the physiological act of chewing.
The muscles that power the jaw movements during chewing are known as the muscles of mastication or masticatory muscles and are functionally classified as;
Jaw elevators: the masseter, temporalis, medial pterygoid, and superior belly of the lateral pterygoid;
Jaw depressors; the anterior digastrics, geniohyoid, mylohyoid and inferior belly of the lateral pterygoid.
The first device for measuring masticatory force (gnathodynamometer) was created by Dr. Bleck. Dr. Bleck found out that periodontal tissue is an important issue, which impact the amount of force in individuals. Dr. Morill found out that masticatory muscles will stop their contraction by appearance the first pain signals from the periodontal tissue differently.
Dr. Shreder used local anaesthesia to ignore the periodontal response to measure the maximum force of mastication. Dr. Shreder's research shows that a 21-year-old man without any periodontal pathology who could produce approximately 35 kilograms-force (340 N) of force, after having local anaesthesia increased the amount of that force increased to 60 kilograms-force (590 N) which roughly was doubled.
Dr. Weber work out that 1 cm2 surface of perpendicular slide of any masticatory muscle can produce approximately 10 kilograms-force (100 N) force. The following surfaces were found
temporalis – 8 cm2
masseter – 7.5 cm2
medial pterygoid – 4 cm2
Thus, the total average surface area of perpendicular masticatory muscles slide is about 19.5 square centimetres (3.02 in2).
Dr. Ali Nankali followed a number of act chewing in different individuals. The result of Dr. Nankali work shows a constant changes in the amount of masticatory force.
Thus, the masticatory force constantly changes in eating time according to mouthful characteristic and size, so it has various effects on the maxilla and mandible through teeth in different moment. Periodontal system controls automatically the measure of mastication force in mentioned process. The jaw elevator muscles develop the main forces used in mastication.
The force generated during routine mastication of food like carrots or meat is about 70 to 150 newtons (16 to 34 lbf). The maximum masticatory force in some people may reach up to 500 to 700 newtons (110 to 160 lbf).;
The study of masticatory force in different types of patients such as patients with polymyositis and dermatomyositis shows that hyposalivation and mucosal alterations can be related to the pathology of masticatory system.
National Medical University
The systematization of masticatory force distribution (Nankali's Masticatory Force Systematization) designed by Dr. Ali Nankali in the National Medical University at the Orthopedic and Implant Stomatology Department, which is important in designing a prosthetic in dentistry.
According to this systematization, the force of Masticatory is divided in two main groups, with physiological or pathological condition. The physiological Masticatory Force with is divided into three different subgroups according to their localizations, anterior, general (covering the entire arch) and posterior part of arch, which is also divided into two different groups; unilateral and bilateral.
It has to be noticed that the condition of producing a maximum masticatory force by a person is using the general subgroup of this systematization.