MUSCULATURE
John Rowson, Adrian Slaney in Dentistry for Lawyers, 1996
There are many muscles in the head and neck; however, only a few of these have relevance to dentistry. The muscles of mastication are a group of muscles which control jaw movement. The largest in size and number are those which close the jaw giving power to the bite. These include the temporalis muscle, which is a large muscle attached to the side of the skull passing downwards to its insertion on the coronoid process of the mandible previously described. In addition, two other powerful muscles take origin from the base of the skull and the rear portion of the cheek bone, and these pass down on each side of the mandible and are attached over a large area around the angle of the mandible. These are, on the outer side, the masseter and, on the inner side, the medial pterygoid.
PROSTHETICS
John Rowson, Adrian Slaney in Dentistry for Lawyers, 1996
Prosthetics involves the replacing of missing teeth by artificial ones. These may be full dentures (false teeth) where the patient is totally edentulous, or partial dentures where only one or more teeth are missing. Replacing missing teeth with dentures restores the normal appearance and improves mastication and speech. Most dentures, whether full or partial, are constructed out of acrylic (plastic) together with acrylic teeth. Metal may be used for the framework of partial dentures and is usually an alloy of cobalt/chrome. This has replaced the use of gold for the framework on account of its lower costs.
BIOMECHANICS OF DENTAL PROSTHESES
Megh R Goyal in Biomechanics of Artificial Organs and Prostheses, 2014
One can loose a tooth due to dental diseases and conditions like: cavities and periodontal. The loss of one or more dental pieces contributes to a deficit in the mastication efficacy, with functionally and organic consequences. This is why patients prefer to replace dental pieces for dental prosthesis. Dental ontologists use a provisional prosthesis. The main purpose of using the provisional prosthesis is to restore the oral integrity of the patient until a final design of the prosthesis is elaborated. Although in some cases the maintenance of the prosthesis is secondary, this process is very important for the complete restoration of the set of teeth (Figs. 1 and 2). Hygienic precautions, correct use, maintenance and the conservation of the dental is a very important topic among patients, because cavities and other premalignant injuries can be avoided with use of established methods of maintenance. This chapter discusses biomechanics of dental prostheses and biomaterials for these prostheses.
Orthodontic intervention combined with myofunctional therapy increases electromyographic activity of masticatory muscles in patients with skeletal unilateral posterior crossbite
Published in Acta Odontologica Scandinavica, 2014
Carla Maffei, Pâmela Garcia, Noemi Grigoletto de Biase, Elisa de Souza Camargo, Michelle Santos Vianna-Lara, Ana Maria Trindade Grégio, Luciana Reis Azevedo-Alanis
Objective. The aim of this study was to evaluate the electromyographic activity of both the temporalis and masseter muscles and the mastication type of patients with skeletal unilateral posterior crossbite before and after orthodontic treatment and speech therapy. Methods. A total of 14 patients with skeletal unilateral posterior crossbite (eight females and six males), between 6–13 years of age, underwent electromyographic evaluation of their masseter and temporalis muscles in mandibular rest, habitual mastication and isometry. The subjects were assessed with regard to mastication type before and after orthodontic treatment and speech therapy. The data obtained during mandibular rest and habitual mastication were normalized in terms of the mean values of isometry. The Student's t-test was used for paired samples to compare the mean values of electromyographic activity (p < 0.05). Results. The masseters during habitual mastication presented higher electromyographic activity after both treatments (p = 0.0458). There was no significant difference between the contralateral masseters in terms of mandibular rest or habitual mastication before or after either treatment (p > 0.05). During habitual mastication, after the treatments, the temporalis muscle on the malocclusion side showed higher electromyographic activity than the contralateral side (p = 0.0263). Prior to therapy, all of the patients exhibited chronic unilateral mastication (n = 14) and 13 patients exhibited bilateral mastication after treatment. Conclusions. Orthodontic intervention combined with myofunctional therapy in patients with skeletal unilateral posterior crossbite provided an increase in the electromyographic activity of the masseter and temporalis muscles during mandibular rest and habitual mastication, with predominantly bilateral mastication.
Cortical control for mastication in cats: Changes in masticatory movements following lesions in the masticatory cortex
Published in Somatosensory & Motor Research, 2005
In a previous paper (Hiraba and Sato ) we reported that an accurate mastication might be executed by the cortical processing in bilateral masticatory area (MA)and motor cortices. The aim of this study was to determine if cats with lesion of either unilateral or bilateral MA showed changes in mastication. After exploring mechanoreceptive fields and motor effects of mastication-related neurons (MRNs) in MA using the single unit recording and intracortical microstimulation methods, we made various lesions in MAs with injections of kainic acid (0.1%, 2.0 µl). Since the MA was divided into facial (F) and intraoral (I) projection areas as reported in the previous paper, cats with the unilateral lesion in F or I, and with the bilateral lesion in F & F, I & I or F & I (F on one side and I on other side) were prepared. Cats with unilateral lesion in F or I and with bilateral lesion in F & I showed no changes in mastication except for prolongation of the food intake and masticatory periods. Cats with bilateral lesion into F & F, or I & I showed wider jaw-opening during mastication. Particularly, the latter group showed enormous jaw-opening, delay in the start of mastication and difficulty in manipulating food on the tongue. In all cats with lesions of each type, masticatory and swallowing rhythms remained normal. These findings suggest that accurate mastication is executed by the close integration between F & F and I & I of the bilateral MA.
Relationship between jaw movement and masticatory performance in adults with natural dentition
Published in Acta Odontologica Scandinavica, 2016
Elan Ignacio Flores-Orozco, Bernat Rovira-Lastra, Eva Willaert, Maria Peraire, Jordi Martinez-Gomis
Objective. This study determines the relationship between several characteristics of jaw movement and masticatory performance determined by multiple regression analysis and adjusted for occlusal contact area and bite force. Materials and methods. Forty-two young adults with natural dentition participated in this cross-sectional study. Occlusal contact area was determined at the maximum intercuspal position by scanning interocclusal records. Maximum unilateral force was measured by means of a gnathodynamometer. The height and amplitude of mastication, occlusal glide length, lateral guidance angle, anterior–posterior distance and cycle duration were recorded using the ARCUSdigma II system. Masticatory performance was determined by sieving the Optosil particles resulting from 20 chewing cycles. Results. Median particle size was negatively associated with height of mastication, maximum bite force, occlusal contact area and amplitude of mastication. Stepwise multiple linear regression analysis revealed that the height of mastication and dental guidance angle are the characteristics of jaw movement most closely related to masticatory performance. Conclusions. In adults with natural dentition, a large vertical height of mastication and a small dental guidance angle are the characteristics of jaw movement most closely associated with good masticatory performance, determined by multiple regression analysis and adjusted for occlusal contact area and bite force.
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