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A forced bite results in displacement of the mandible and malposition of the condyles. The terminal hinge position is a useful point of reference in treatment planning for the surgical correction of forced bites, since it is, among others, independent of the occlusion. Thus, it provides an ideal condyle-fossa relation.
The maximal bite force was recorded between antagonizing anterior teeth in a group (n = 10) of patients with pathologic attrition and in a control group. No statistically significant difference between the maximal bite forces was recorded. Also, the effect on the maximal bite force of the continuous wearing of a partial bite raising splint for 4 months was recorded. The great individuality in reaction patterns prohibited simple generalizations. However, in some individuals the maximal bite force was larger when biting on the splint than without, both at base line and after 4 months. Also, the maximal bite force showed a tendency to increase with time. The findings indicate that pathologic attrition is not necessarily associated with a high maximal bite force. Also, the maximal bite force recorded under various conditions is seemingly not an absolute value but rather the result of a number of factors of varying importance for different individuals.
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This study compared bite force discrimination between 14 treated periodontal patients with significant bone resorption and 14 control subjects who were free of periodontal disease. Bite force was measured using a strain gauge scale which permitted subjects to visually monitor when their bite force equaled a preset resistance. A bite force of 500 gm was selected as the standard. Subjects were presented with a series of paired resistance settings, one at a time, the first of each pair being the standard and the second being the comparator setting of some predetermined different amount. This procedure was continued until the subject's difference limen (DL) value, the threshold of discrimination between two bite forces, was established. The periodontal patients required an average of 334 additional grams of resistance over the standard before they could detect a difference, whereas the control subjects required only 201 additional grams. These group means were significantly different (P less than 0.01). The results of this study suggest that the periodontal ligament provides sensory feedback relative to bite force discrimination.
The effect of the three-dimensional orientation of occlusal force on maximal bite-force magnitude was examined in seven human subjects at three different unilateral anteroposterior bite positions (canine, second premolar and second molar). At each position, bite-force magnitude was registered in 17 precisely defined directions using a three-component force transducer and a feedback method. In addition, to assess the efficiency of transfer of muscle to bite force, for bites produced in the sagittal plane, moment-arm length was determined and the produced bite-force moment calculated. The results showed that the largest possible bite force was not always produced in a direction perpendicular to the occlusal plane. Generally, maximal bite force in medial and posterior directions was larger than that in, respectively, corresponding lateral and anterior directions. In each direction the produced force was larger at the posterior bite point than at the anterior bite point. The combined moment produced by the jaw muscles was largest for vertical bites, smallest for posteriorly directed bites and intermediate for anteriorly directed bites. In the case of vertically and anteriorly directed bites the produced moment did not vary significantly with the bite position. Hence, for these bite positions the jaw closing moment of the muscles must have kept constant. In the case of posteriorly directed bites the produced moment decreased when bite position changed from the anterior to the posterior side of the dentition. This indicated that jaw muscle activity had declined.
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The maximal bite force and the strength of the finger-thumb grip of 125 Skolt Lapps, aged 15 to 65, was measured with a specially devised apparatus. The bite force was measured with the biting fork placed between the first molars and between the incisors, respectively. The finger-thumb grip was measured by letting the subject press the prongs of the fork between the thumb and forefinger of each hand as hard as possible. The range of inter-individual variation of the maximal bite force and finger-thumb grip was great. The mean values were higher for the males than for the females. In the males the maximal bite force thus measured in the molar region was 39 kg (382 N) and 18 kg (176 N) in the incisor region. The corresponding values for the females were 22 kg (216 N) and 11 kg (108 N). The finger-thumb grip strength for males was, on the average, 10 kg (98 N); that of the females, 7 KG (69 N). The average difference in bite force between the men and the women was larger in the group with natural teeth than in the one with complete dentures. The values found for the bite force decreased with increasing age, especially for the females. Most of this reduction with increasing age was probably due to the age-dependent deterioration of the dentition. In both sexes the bite force was notably smaller among the denture wearers than among the dentate persons. The number of natural teeth varied closely with the bite force, i.e. the greater number of natural teeth the greater the bite force.
Maximum voluntary bite force has been used to evaluate functional changes following orthognathic surgery. It has been proposed by others that maximum voluntary bite force may depend, in part, on sensory input from the dentition. However, results from previous studies have shown contradictory effects of local anesthesia on bite force following anesthetization of the dentition. The purpose of this study was to investigate the effects of drug-induced local anesthesia on the generation of first molar bite force and electromyographic (EMG) activity in adults. Twenty normal adults (3 women, 17 men) were evaluated. Electromyographic activity was monitored from four muscles of mastication bilaterally, and bite force was concurrently recorded at the right and left first molars. Maximal and submaximal bite forces were then measured after sequential unilateral anesthetization of the right mandible and maxilla with 2% lidocaine containing 1:100,000 epinephrine. No statistically significant differences in bite force or integrated EMG levels were observed between the unanesthetized and anesthetized sides, nor on the anesthetized side at different levels of anesthesia.
The biting force of 855 Nigerian children and adults from the age of 3 to 60 was recorded in the Joint Dental Epidemiological Survey in Nigeria in 1981. The biting force of the Nigerian rural group (245 males and 178 females) was significantly greater than those of the Nigerian urban group (227 males and 203 females) and the Japanese males and females.
Human subjects commonly show large variations in bite force produced at the first molar teeth. To evaluate the role of muscle cross-sectional sizes and lever arms in bite-force production, we correlated these variables in 11 healthy adults. Axial and coronal images obtained by magnetic resonance were combined with conventional lateral cephalograms and dental cast data to reconstruct the craniomandibular morphology in each subject. The cross-sectional sizes of the right masseter and medial pterygoid muscles, their lever arms, and the bite-point lever arms were measured directly from these reconstructions. Physiological recordings of bite force were made in the region of the right first molar by means of a customized transducer aligned perpendicular to the functional occlusal plane. The average bite force for the sample as a whole was 189 +/- 78 N. The coefficients of variance were greater for bite forces, and for the cross-sectional sizes of the two muscles, than for their respective lever arms. Highly significant Pearson Product Moment correlation coefficients (p less than 0.005) were found between masseter and medial pterygoid cross-sectional size, and between the cross-sectional size of each muscle and bite force. No significant correlations (p greater than 0.1) were found between muscle or bite-point lever arms and bite force. Despite the fact that craniofacial spatial morphology may differ among subjects, jaw muscle size alone seems to explain most of the variation in bite force reported by ourselves and others.
A three-dimensional mathematical model of the human masticatory system, containing 16 muscle forces and two joint reaction forces, is described. The model allows simulation of static bite forces and concomitant joint reaction forces for various bite point locations and mandibular positions. The system parameters for the model were obtained from a cadaver head. Maximum possible bite forces were computed using optimization techniques; the optimization criterion we used was the minimizing of the relative activity of the most active muscle. The model predicts that at each specific bite point, bite forces can be generated in a wide range of directions, and that the magnitude of the maximum bite force depends on its direction. The relationship between bite force direction and its maximum magnitude depends on bite point location and mandibular position. In general, the direction of the largest possible bite force does not coincide with the direction perpendicular to the occlusal plane.
Maximal bite force was measured and intraoral condition was examined in 89 patients at the Institute of Dentistry, University of Turku. These patients formed three different denture groups: those with complete dentures, those with full maxillary denture and partial mandibular denture, and those with natural dentition or skeleton-supported partial maxillary denture and partial mandibular denture. There were three age groups: greater than or equal to 70, 60-69, and less than or equal to 59 years old. Maximal bite force was recorded with an appliance at seven different measuring points by placing a biting fork between the antagonistic teeth while at the same time the occlusion was stabilized contralaterally with a plastic tube. Maximal bite force had a correlation with age and sex (P less than 0.01). In partial-denture groups high bite force had a correlation with the breaking of dentures (P less than 0.001 and P less than 0.05, respectively). Satisfied patients had a higher bite force than dissatisfied ones. When there was some disturbance in occlusion, the bite force was smaller, especially in full-denture groups (P less than 0.001). Full-denture wearers also had a good bite force, but the best biting area was located more posteriorly than in patients who still had some natural teeth left in both jaws. Changes in the denture-bearing mucosa in patients with complete dentures and negative height of the mandibular alveolar process decreased the bite force slightly.
The maximum bite force and position of the hyoid bone during natural and extended head posture were studied in 15 adults. All participants had normal occlusions and full dentitions. In addition, there were no signs or symptoms of craniomandibular disorders. The bite force was measured with a bite force sensor placed between the first molars. Six registrations of gradually increasing bite force up to a maximum were made with randomized natural and extended head postures. With one exception, the mean maximum bite force value was found to be higher for every subject with extended head posture compared to natural head posture. The sample mean was 271.6 Newton in natural head posture and 321.5 Newton with 20 degrees extension. With changed head posture, the cephalometric measurements pointed towards a changed position of the hyoid bone in relation to the mandible and pharyngeal airway. The cephalometric changes in the position of the hyoid bone could be due to a changed interplay between the elevator and depressor muscle groups. This was one factor which could have influenced the registered maximum bite force.
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 of the 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 control subjects and 387 N in patients, with corresponding bilateral values of 347 N and 230 N. At predetermined levels of contraction, temporalis 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 significantly correlated to bite force. With the present method it was demonstrated that unilateral bite force is a simple clinical indicator of mandibular elevator strength as a whole, but inadequate to disclose asymmetric conditions. During isometric contraction, relative strength of electromyographic activity fairly accurately imaged the output of mechanical activity.
Maximum biting force and chewing performance were measured in adult subjects before and after four-weeks training by newly devised "Chewing Ability Enhancing Substances (CAES)". The CAES is made of glucomannan. The number of chewing strokes and chewing time until the last swallowing action are much larger when chewing CAES than those of other usual eating materials. By four weeks training using CAES, the maximum biting force and chewing performance of the subject were clearly increased. However, this increased chewing ability began to return to the control level gradually 2 weeks after the cessation of the training.
The correlation between mouth-breathing and bite force was studied in 81 children, 7 to 16 years old. Mouth-breathing was diagnosed on the basis of the subject history, the rhinomanometrically determined nasal airflow and the size of the airway measured on the profile cephalogram. The maximum bite force was measured at the first molars. In addition, the facial morphology was analysed on profile cephalograms. Both mouth-breathing and bite force were associated with the facial morphology but there was no association between mouth-breathing and bite force. It was concluded that the long-face morphology characteristic of mouth-breathing children is not due to weak masticatory muscles.
The recovery of the masticatory function in patients with dentures was assessed by several indices such as masticatory efficiency, maximal biting force and electromyographic analysis. We have attempted to develop a new method of calculating the biting force of edentulous patients by using electromyography. The method has almost been established, but, depending on the clenching speed, there is a certain difference between the estimates obtained from this method and the biting force obtained from a force transducer. The purpose of this study is to clarify the effect of the clenching speed on the method of calculating the biting force by using electromyography. In 9 healthy subjects with normal dentitions, biting force and electromyograms were recorded simultaneously under 3 different clenching speed conditions. After the recording, the relation between the biting force and integrated electromyography was compared thoroughly. The effect of the clenching speed on the method of calculating the biting force by using electromyography was also investigated. The following results and conclusions were obtained: 1. At a slow clenching speed, a linear relation between the biting force and integrated electromyography was found. 2. At a medium clenching speed, the relation showed a slightly upward curvature as the biting force was increased and a slightly downward curvature as it was decreased. 3. At a fast clenching speed, the relation between the biting force and integrated electromyography showed an upward curvature as the biting force was increased, and a downward curvature as it was decreased. 4. At the slow and medium clenching speeds the estimates obtained from this method approximated the biting forces obtained from a force transducer. 5. At the fast clenching speed, the tendency was found that the estimates obtained from this method were higher than the biting force obtained from a force transducer. 6. When realizing this tendency, the method of calculating the biting force by using electromyography can be said to be clinically effective.