No abstract

Bakke M, Ho]m B, Jensen BL, Michlcr L, Moller E: Unilateral, isometric bite force in 8-68-year-old women and men related to occtusal factors. Scand J Dent Res 1990; 98: 149-58.Abstract -Unilateral bite force was studied in 63 women and 59 men, 8-68 yr of age. The subjects had a minimum of 24 teeth and no symptoms orsigns of disorders of the craniomandibular system. Bite force was stronger in men (522 N) than in women (441 N). It increased with age until 25 yr (/•< 0.0001). The level decreased significantly after this age in women, whereas it only tended to decrease in men and not until after 45 yr of age. Body height was positively associated with force. However, the strongest correlation (r: 0.43-0.49,/"< 0.01) with adult bite force was occlusal contact. The normal bite-force values with important determining factors provide reference data for screening of elevator muscle strength in routine examination of craniomandibular function.

The thickness of the human masseter muscle, corresponding approximately to a cross‐section at the most bulky part of the superficial portion, was measured by ultrasound scanning at three sites 1 cm apart. The study included 13 women, 21–28 yr of age, with a minimum of 24 teeth and without craniomandibular disorders. Ultrasonography produced a well‐defined depiction of the muscle with distinct tendinous structures. The average thickness at the measuring sites varied from 8.83 to 11.08 mm with the muscle relaxed, and increased significantly during contraction to average values between 9.84 and 12.57 mm. The study showed a connection between measures of masseter thickness and function of the muscle, as well as parameters generally associated with masseter muscle function. Muscle thickness at the voluminous anterior part of the superficial portion was systematically and significantly correlated to bite force, occlusal tooth contact and cephalometric data (anterior face height, vertical jaw relation and mandibular inclination). In conclusion, ultrasound scanning gave an uncomplicated and a reproducible access to parameters of jaw muscle function and its interaction with the craniomandibular system.

No abstract

No comprehensive study has previously been published on orofacial function in patients with well-defined Parkinson's disease (PD). Therefore, the aim of this study was to perform an overall assessment of orofacial function and oral health in patients, and to compare the findings with matched control subjects. Fifteen outpatients (nine women and six men, 61-82 yr of age; Hoehn & Yahr Stages 2-4; and with motor impairment ranging from 17 to 61 according to the Unified Parkinson's Disease Rating Scale, Objective Motor Part III) were examined in their 'on' state together with 15 age- and gender-matched controls. Orofacial function and oral health were assessed using the Nordic Orofacial Test, masticatory ability, performance and efficiency, oral stereognosis, jaw opening, jaw muscle tenderness, the Oral Health Impact Profile-49, number of natural teeth, and oral hygiene. Orofacial dysfunction was more prevalent, mastication and jaw opening poorer, and impact of oral health on daily life more negative, in patients with PD than in controls. The results indicate that mastication and orofacial function are impaired in moderate to advanced PD, and with progression of the disease both orofacial and dental problems become more marked. It is suggested that greater awareness of the special needs in PD patients and frequent dental visits are desirable to prevent dental diseases and decay and to support masticatory function.

Bakke M, Michler L, Han K, Moller E: GlinicaS significance of isometric bite force versus electrical activity in temporal and masseter muscles. ScandJ Dent Res 1989; 97: 539-51.Abstract -Bite force and activity in temporal and masseter muscles, during biting and chewing were recorded in 19 control subjects and 23 subjects with symptoms and signs of functional disorders ofthe craniomandibular system. The entire group comprised 13 men and 29 women, 14^63 yr of age. Maximal unilateral bite force was 480 Newton (N) in controi subjects and 387 N in patients, with corresponding bilateral values of 347 N and 230 N. At predetermined levels of contraction, temporaiis and masseter activity were linearly related. Correlations of bite force and activity in short static contractions were significant with respect to unilateral, but not to bilateral force measurements. Only in the masseter muscle was strength of dynamic contractions during chewing signiiicantly correlated to bite force. With the present method il was demonstrated that unilateral bite force is a simple clinical indicator of mandibular elevator strength as a wbole, but inadequate to disclose asymmetric conditions. During isometric contraction, relative strength of electromyograpbic activity fairly accurately imaged the output of mechanical activity.Araujo PA de, Asmussen E: Aluminum oxalate/glycine solutions as pretreatment in the Gluma bonding system. Scand J Dent Res 1989; 97: 552-8.Abstract -DentiB and enamel surfaces were treated with solutions of aluminum oxalate (AO), the pH of which was adjusted by glydne. Gluma as well as an enamel bonding agent were applied to the surfaces before the placement of a composite resiti. On .shear bond testing, there was obtained a strong adhesion that was influenced by the pH of the AO solutions. Dentin and enamel specimens for examination by scanning electron microscopy (SEM) were also prepared and treated as above. Enamd specimens showed a very definite etching pattern, and on the dentin surfaces a precipitate was observed. The amount of this product seemed to decrease as the pH increased.

The present study examined the associations between craniofacial dimensions, head posture, bite force, and symptoms and signs of temporomandibular disorders (TMD). The sample comprised 96 children (51F, 45M) aged 7-13 years, sequentially admitted for orthodontic treatment of malocclusions entailing health risks. Symptoms and signs of TMD were assessed by 37 variables describing the occurrence of headache and facial pain, clicking, jaw mobility, tenderness of muscles and joints, and the Helkimo Anamnestic and Dysfunction indices. Craniofacial dimensions (33 variables), and head and cervical posture (nine variables) were recorded from lateral cephalometric radiographs taken with the subject standing with the head in a standardized posture (mirror position). Dental arch widths were measured on plaster casts and bite force was measured at the first molars on each side by means of a pressure transducer. Associations were assessed by Spearman correlations and multiple stepwise logistic regression analyses. The magnitudes of the significant associations were generally low to moderate. On average, temporomandibular joint (TMJ) dysfunction was seen in connection with a marked forward inclination of the upper cervical spine and an increased craniocervical angulation, but no firm conclusion could be made regarding any particular craniofacial morphology in children with symptoms and signs of TMJ dysfunction. Muscle tenderness was associated with a 'long face' type of craniofacial morphology and a lower bite force. Headache was associated with a larger maxillary length and increased maxillary prognathism. A high score on Helkimo's Clinical Dysfunction Index was associated with smaller values of a number of vertical, horizontal, and transversal linear craniofacial dimensions and a lower bite force.

In spite of differences in embryologic origin, central nervous organization, and muscle fiber distribution, the physiology and action of mandibular elevator muscles are comparable to those of skeletal muscles of the limbs, back, and shoulder. They also share the same age‐, sex‐, and activity‐related variations of muscular strength. With respect to pathogenesis, the type of muscular performance associated with the development of fatigue, discomfort, and pain in mandibular elevators seems to be influenced by the dental occlusion. Clinical research comparing the extent of occlusal contact in patients and controls as well as epidemiologic studies have shown reduced occlusal support to be a risk factor in the development of craniomandibular disorders. In healthy subjects with full natural dentition, occlusal support in the intercuspal position generally amounts to 12–14 pairs of contacting teeth, with predominance of contact on first and second molars. The extent of occlusal contact clearly affects electric muscle activity, bite force, jaw movements, and masticatory efficiency. Neurophysiologic evidence of receptor activity and reflex interaction with the basic motor programs of craniomandibular muscles tends to indicate that the peripheral occlusal control of the elevator muscles is provided by feedback from periodontal pressoreceptors. With stable intercuspal support, especially from posterior teeth, elevator muscles are activated strongly during biting and chewing with a high degree of force and masticatory efficiency, and with relatively short contractions, allowing for pauses. These variables of muscle contraction seem, in general, to strengthen the muscles and prevent discomfort. Therefore, occlusal stability keeps the muscles fit, and enables the masticatory system to meet its functional demands.