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PubMed2000

Morphologic and biomechanical correlates with maximum bite forces in orthognathic surgery patients.

PURPOSE: The purpose of this study was to determine which factors of craniofacial morphology best predict maximum bite forces and jaw muscle strength (based on [electromyogram] EMG/force slopes) in patients selected for various orthognathic surgical procedures. These factors were then compared for their ability to separate orthognathic surgery patients by their clinical diagnosis. PATIENTS AND METHODS: Standard lateral cephalograms were taken of 121 orthognathic surgery patients (before treatment) and 80 control subjects to establish multivariate sagittal and biomechanical factors of craniofacial form. Maximum and submaximal bite forces were recorded at 8 tooth positions for each subject. EMG activity was recorded for 3 pairs of muscles (anterior temporalis, posterior temporalis, and superficial masseter) during the isometric bites. The EMG and bite force measurements were used to calculate EMG/force slopes as a measure of jaw muscle strength. The study looked for significant correlations between the morphologic factors and maximum bite force or jaw muscle strength. RESULTS: Factor analysis determined 12 sagittal and 6 biomechanical factors. However, only 3 of the sagittal and 4 of the biomechanical factors were significantly correlated with maximum bite force or jaw muscle strength. Factors reflecting jaw size were correlated with maximum bite forces and jaw muscle strength but generally did not separate patient groups. The factor most strongly correlated with maximum bite forces separated patients by their relative difference between anterior and posterior facial height. The factor for anteroposterior maxillomandibular discrepancies was not correlated with maximum bite force or jaw muscle strength. CONCLUSIONS: Many cephalometric measurements used to diagnose craniofacial deformities and to assign patients to particular orthognathic surgical procedures are not correlated with maximum bite forces or jaw muscle strength. Only measurements reflecting relative differences between anterior and posterior facial height are both strongly correlated with maximum bite force and reflect assignment of surgical procedures.

Adult↗
PubMed2005

Bite force measurement in awake rats: a behavioral model for persistent orofacial muscle pain and hyperalgesia.

AIMS: To test the hypotheses that masseteric inflammation produces a reduction of mean bite force and success rates and that classical anti-inflammatory agents prevent inflammation-induced changes in bite force. METHODS: Rats were initially trained to produce a bite force greater than 400 g. Once the rats attained above 70% of successful responses in a 10-minute test period, the bite force required for reinforcement was increased gradually to the target force of 1.3 kg. Seven trained rats received bilateral masseteric injections of complete Freund's adjuvant (CFA; 50 microL in isotonic saline). The mean number of attempted bites, the percentage of correct responses, and the bite force measured before and 1, 2, 3, 7, 10, and 14 days following the CFA injection were compared. Five additional trained rats were injected with the same volume of vehicle control. Other rats (n = 10) were treated with anti-inflammatory agents before and after the CFA injection. RESULTS: Intramuscular CFA, but not the vehicle, produced a significant reduction of mean bite force and success rate at days 1, 2, and 3. Bite force and success rate gradually increased; they returned to baseline by 14 days. The CFA-mediated reduction of bite force and success rate was prevented in rats treated with anti-inflammatory agents administered intraperitoneally (dexamethasone, n = 5, or indomethacin, n = 5, 4 mg/kg). CONCLUSION: These results provide further evidence that bite force measurements in awake rats can be a useful method for the study of inflammatory muscle hyperalgesia.

Animals↗
PubMed1995

A study of bite force, part 2: Relationship to various cephalometric measurements.

Maximum bilateral bite force, determined in 129 dental students, was evaluated with regard to six skeletal and eight dental measurements acquired from conventional lateral cephalometric radiographs. Statistically significant correlations for three of the skeletal measurements were found. Maximum bite force increased with regard to decreasing mandibular plane/palatal plane angle and to decreasing mandibular plane angles. Maximum bite force increased with an increasing ratio of posterior facial height to anterior facial height. Significant statistical correlation for only one of the eight dental measurements was found: maximum bite force related directly with increasing maxillary and/or mandibular dentoalveolar heights, and unexpected finding.

Alveolar Process↗
PubMed2002

[Maximal isometric bite force and sports. Preliminary study].

INTRODUCTION: The evaluation of the bite forces coupled with EMG activity of masseter muscles allows to point out temporo-mandibular joint disorders. The intense practice of sports induces stress which may affect the mandibular statics, due to an hyperfunction of the elevator masticatory muscles, especially the masseter muscles. This concept has led us to compare the maximum isometric bite forces of sedentary and physically trained subjects. MATERIAL AND METHODS: The aim of this experimentation is to study the maximum isometric bite forces of the premolars, with a force transducer, for two groups of physically trained and sedentary volunteers (25 subjects), with distinction between male and female subjects. Subjects with normal denture and no temporo-mandibular joint disorder were retained. EMG and force recording were synchronized and recorded during 10 seconds of maximal contraction. RESULTS: The male subjects developed a maximal bite-force significantly higher (p < 0.05) compared to the female subjects. There is no significant difference between subjects practising a sport (at least 6 hours a week) and sedentary ones. The evolution of force during the contraction is different between sexes. EMG activity allowed to control that subjects developed a maximal force and an increase in muscular fatigability of physically active females compared to sedentary ones was noticed. DISCUSSION: The difference of maximal force between men and women is similar to the one found for the locomotor muscles. The analysis of the evolution of the force according to the contraction duration, might be linked to a different distribution of muscular fibers according to the sex. The practice of a sport might increase the fatigability of the masseter muscles and might be a factor inducing a muscular imbalance of the mandibular posture. But the relatively low number of subjects and the absence of well defined distinctions between different kinds of sport limit our conclusions.

Adult↗
PubMed2006

Functional properties and regional differences of human masseter motor units related to three-dimensional bite force.

The aim of this study was to estimate numerically the properties of masseter motor units (MUs) in relation to bite force magnitude and direction three-dimensionally and to confirm the hypothesis that the properties differ between different parts of the muscle by means of simultaneous recording of MU activity along with the MU location and three-dimensional (3D) bite force. The MU activity of the right masseter of four healthy men was recorded using a monopolar needle electrode in combination with a surface reference electrode. The location of the needle electrode was estimated stereotactically with the aid of magnetic resonance images and a reference plate. The magnitude and direction of the bite force was recorded with a custom-made 3D bite force transducer. The recorded bite force was displayed on a signal processor, which enabled the participant to adjust the direction and magnitude of the force. The activities of 65 masseter MUs were recorded. Each MU had specific ranges of bite force magnitude and direction (firing range: FR) and an optimum direction for recruitment (minimum firing threshold: MFT). There was a significant negative correlation between MFT and FR width. There were functional differences in MU properties between the superficial and deep masseter and between the superficial layer and deep layer in the superficial masseter. These results indicate that the contribution of human masseter motor units to bite force production is heterogeneous within the muscle.

Action Potentials↗
PubMed2006

Evaluation of maximal bite force in temporomandibular disorders patients.

The aim of this study was to evaluate the maximum bite force in temporomandibular disorders (TMD) patients. Two hundred women were equally divided into four groups: myogenic TMD, articular TMD, mixed TMD and control. The maximum bite force was measured in the first molar area, on both sides, in two sessions, using an IDDK (Kratos) Model digital dynamometer, adapted to oral conditions. Three-way anova, Tukey and Pearson correlation tests were used for the statistical analysis. The level of statistical significance was given when P < or = 0.05. The maximal bite force values were significantly higher in the control group than in the experimental ones (P = 0.00), with no significant differences between sides. Higher values were obtained in the second session (P = 0.001). Indeed, moderate negative correlation was found between age and bite force, when articular, mixed groups and all groups together were evaluated. A moderate negative correlation was also detected between TMD severity and the maximal bite force values for myogenic, mixed and all groups together. Authors concluded that the presence of masticatory muscle pain and/or TMJ inflammation can play a role in maximum bite force. The mechanisms involved in this process, however, are not well understood and deserve further investigation.

Adult↗
PubMed2001

[Effect of increased and decreased bite force on morphology of periodontal tissues].

OBJECTIVE: The aim of this study was to observe the effect of bite force on morphology of periodontal tissues. METHODS: Animal models were induced by extracting the left maxillary molars; the left mandibular molars served as decreased bite force models; the right mandibular molars served as increased bite force models. The dynamic changes of widths of periodontal ligament and cementum were measured. RESULTS: In decreased bite force group, there were significant morphologic changes of periodontal tissues after 1 week. In increased bite force group, there was no significant change. Ligament widths were significantly different after 2, 3 weeks respectively in those two groups, compared with that in control group (P < 0.05). There were significant differences between proximal alveolar wall and distal alveolar wall in width (P < 0.05). CONCLUSION: The histological morphology is closely related to the mechanical condition. Physiological bite force is necessary for periodontal ligament to maintain its physiological structure.

Animals↗
PubMed1989

The effect of experimental anesthetization of the temporomandibular joint superior cavity on bite force discrimination.

The purpose of this study was to determine whether bilateral experimental sensory impairment of the temporomandibular joints (TMJs), as induced by injecting 1.5 ml of two percent mepivacaine into the superior cavity of the TMJs would alter the subject's ability to discriminate among differences in their bite force. Assessment of bite force was measured isometrically, using the strain gauge scale, and isotonically, using the mechanical swing beam scale. Resistance forces of 500 and 1000 gms were selected as standards. For each task, subjects were given a series of paired resistance settings, one at a time, the first of each pair being the standard resistance and the second being a comparator resistance of some greater amount. Subjects reported whether biting against the comparator resistance was equal to, greater than, or less than the standard resistance. This procedure of paired comparisons was continued until the subject's threshold of discrimination (difference limen value) between two biting forces was established. The results revealed that the subject's ability to discriminate differences in their bite force, either isometrically or isotonically, was not significantly (p greater than 0.05) affected following anesthetization of the superior cavity of the TMJs. These findings suggest that the sensory receptors within the TMJ capsules are not significantly involved in the detection of forces that play a role in monitoring biting force.

Adult↗
PubMed1994

Direction of a bite force determines the pattern of activity in jaw-closing muscles.

Human individuals were hypothesized to use the same pattern of jaw muscle activity to produce the same bite force. To test this hypothesis, we used a 2-mm-thick force transducer to monitor the magnitude and direction of a bite force between a single pair of occluding first molars. Five subjects performed standardized bite force tasks. Six different magnitudes were tested, each in five directions. The surface electromyographic (EMG) activity in the left and right masseter and temporalis muscles was recorded, integrated, and normalized. Ratios of the EMG activity of paired muscles (e.g., the ratio of working temporalis and working masseter) were calculated for each bite force task. Each ratio was roughly constant for each direction of bite force, regardless of its magnitude. In contrast, when the magnitude of bite force was the same but the directions were different, the ratio was not constant. We conclude that the direction of a bite force, not its magnitude, determines the pattern of activity of jaw-closing muscles. The shared patterns of muscle activation may be the result of a subconscious optimization of jaw muscle forces to improve efficiency.

Adult↗
PubMed1997

Impact velocities of the teeth after a sudden unloading at various initial bite forces, degrees of mouth opening, and distances of travel.

A potentially dangerous situation arises when an individual bites on hard and brittle food which suddenly breaks, since the impact velocity of the lower teeth onto the upper teeth after the food is broken can be high and may cause dental damage. The present experiments were designed to study the magnitude of the impact velocity after a sudden unloading at various initial bite forces, degrees of mouth opening, and distances of travel. Subjects were asked to perform a static biting task during which the resistance to the bite was suddenly removed. The upward mandible movement was arrested after a certain distance. The velocity of the lower teeth at impact was calculated just before the mandible came to a standstill in combinations of 4 different bite forces (100, 80, 60, and 40 N), 4 different initial degrees of mouth opening (33.5, 30.5, 27.5, and 24.5 mm), and 3 different distances of travel of the mandible (4.5, 3.0, and 1.5 mm). We found that the bite force rapidly declined after the unloading, resulting in a small impact velocity of the lower front teeth. This impact velocity largely depended on the magnitude of the initial bite force and the distance traveled; it was barely sensitive to variations in degree of initial mouth opening. The maximal velocity of the lower teeth was 0.43 m/s (at an initial bite force of 100 N). This maximum was reached after a distance of travel of about 4 mm in 12 ms. The data suggest that the rapid decline in bite force coupled with a limitation of impact velocity is due to the force-velocity properties of the active jaw muscles and is not caused by neural control.

Biomechanical Phenomena↗
PubMed1998

The variability of bite force measurement between sessions, in different positions within the dental arch.

The effect of measuring bite force with different patterns of transducer on different occasions was studied. Maximum voluntary bite force was measured in eight volunteers. Three transducer positions, each with a different pattern of transducer, were used; between the anterior teeth, between the second premolar and the first molar on one side and between the second premolars and first molars on both sides. Visual feedback of force was provided. Two sets of five maximum clenches were recorded with a rest period in between. This sequence was repeated for each transducer and the experiment was repeated on three different days. The highest forces were measured with the bilateral posterior transducer (mean 580 N, s.d. 235) and the lowest on the anterior transducer (mean 286 N, s.d. 164). The standard deviations of the bite force mean values were used as an indication of the variability and were subjected to a non-parametric anova (Kruskal-Wallis). The forces recorded with each transducer position were significantly different between the transducers (P < 0.01) and the maximum bite force showed least variability when measured between the posterior teeth on one side only. There was little difference in bite force between the three different sessions (P > or = 0.05) when measured in the same position within the dental arch, whichever of the three positions that may be.

Adult↗
PubMed2001

Comparison of maximum bite force and dentate status between healthy and frail elderly persons.

The purpose of the present study was to (1) determine the standard value of maximum bite force and to (2) compare the maximum bite force of the elderly between healthy and frail subjects. Subjects included 349 healthy elderly individuals (149 males, 200 females) and 24 frail elderly individuals (seven males, 17 females) ranging from 65 to 74 years of age. Maximum bite force was evaluated using a Dental Prescale system. The maximum bite force of the healthy subjects was significantly higher than that of the frail subjects in both males (P=0.020) and females (P=0.015). However, no significant difference was observed in the number of present teeth between the healthy and frail subjects. Median of maximum bite force in healthy males was 408.0 N, and that of the healthy females was 243.5 N. These results suggest that the frail elderly have latent bite force problems.

Aged↗
PubMed2006

Bite force and occlusal contact area changes following mandibular widening using distraction osteogenesis.

OBJECTIVE: To examine changes in bite force and occlusal contact area after mandibular widening by distraction osteogenesis using pressure-sensitive sheet (Dental-Prescale; Fuji Photo Film, Tokyo, Japan). STUDY DESIGN: Fifteen patients with transverse mandibular deficiency (6 to 9 mm, mean distraction interval: 8 mm) were examined. They were measured just before the operation and at 1 week, 1 month, 3 months, 6 months, and 1 year after the operation. Ten control subjects with normal occlusion were also measured. RESULTS: Both bite force and occlusal contact area were lowest at 1 month postoperatively. The values of bite force and occlusal contact area steadily increased thereafter. The bite force and occlusal contact area reached to the preoperative levels at 6 months after operation and slightly above the preoperative level at 12 months after operation. There were no statistically significant differences between 12 months and the control values for bite force measurements (P > .05). CONCLUSION: Although statistically not significant, this study suggests that mandibular symphyseal distraction osteogenesis increases the bite force and occlusal contact area in patients with transverse mandibular deficiency.

Adolescent↗
PubMed2005

Molar bite force in relation to occlusion, craniofacial dimensions, and head posture in pre-orthodontic children.

The present study examined bite force in relation to occlusion, craniofacial dimensions, and head posture. The sample comprised 88 children (48 girls, 40 boys) aged 7-13 years, sequentially admitted for orthodontic treatment of malocclusions entiling health risks. Bite force was measured in the molar region by means of a pressure transducer. Angle classification, number of teeth and contact in the intercuspal position (ICP) were recorded and dental arch widths were measured on plaster casts. Craniofacial dimensions and head posture were recorded from lateral cephalometric radiographs taken with the subject standing with their head in a standardized posture (mirror position). Associations were assessed by Spearman correlations and multiple stepwise regression analyses.The maximum bite force increased significantly with age in girls, with teeth in occlusal contact in boys, and with increasing number of erupted teeth in both genders. Bite force did not vary significantly between the Angle malocclusion types. Only in boys was there a clear correlation between bite force and craniofacial morphology: cranial base length (n-ba, n-ar), posterior face height (s-tgo, ar-tgo), vertical jaw relationship (NL-ML), mandibular inclination (NSL-ML), form (ML-RL) and length (pg-tgo), and inclination of the lower incisors (Ili-ML). Multiple regression analysis showed that the vertical jaw relationship (P < 0.001) and the number of teeth present (P < 0.01) were the most important factors for the magnitude of bite force in boys. In girls, the most important factor was the number of teeth present (P < 0.001). No correlations between bite force and head posture were found.

Adolescent↗
PubMed1986

In-vivo bone strain as an indicator of masticatory bite force in Macaca fascicularis.

The hypothesis that mandibular bone-strain patterns are a good indicator of molar bite-force patterns in M. fascicularis during mastication was tested by determining the relationship between mandibular bone-strain patterns and bite-force patterns during isometric biting. Bone-strain patterns were determined using rosette strain gauges bonded to mandibular cortical bone below the roots of the M2 during isometric binding on a transducer along the M1-M2 region. The effects of rosette position on bone-strain patterns during mastication was determined by comparing bone-strain patterns recorded from two different rosettes; one bonded below the roots of the M2 and the other below the roots of the M3. The data from the two experimental sets support the hypothesis that bone-strain patterns along the working side of the mandible are a good indicator of bite-force patterns during the power stroke. The relationship between bone-strain patterns and bite-force patterns was not perfect and the two principal strains were not of equal value. In general, principal compression was a better indicator of bite force than principal tension.

Animals↗
PubMed1996

Mandibular excursions and maximum bite forces in patients with temporomandibular joint disorders.

PURPOSE: This study evaluated mandibular motion and bite force in patients with temporomandibular joint disorders after joint surgery. PATIENTS AND METHODS: Maximum voluntary mandibular motion, maximum excursion during mastication, and maximum bite force were examined in 25 female patients before temporomandibular joint surgery. Their pretreatment performance was compared with that at 6 weeks, 6 months, and 1 year after surgery, and with performance of 26 normal female volunteers. RESULTS: Before surgery, all of the patients' movements and bite forces were smaller than those of controls. One year after surgery, maximum interincisal opening increased significantly, but lateral excursion and protrusion remained unchanged. Maximum bite forces increased significantly and nearly reached control levels. CONCLUSIONS: Patients with severe restriction in temporomandibular joint function exhibit general improvements in some mandibular movements and in maximum bite force after surgical treatment.

Adolescent↗
PubMed2002

Bite force determination in children with primary dentition.

The aim of this study was to determine the bite force with primary dentition in 30 children with normal occlusion (group I), cross bite (group II) and open bite (group III). The magnitude of the bite force was determined through a pressurized transmitter tube (pressure sensor MPX 5700 Motorola), which was connected to a converse analog/digital electronic circuit. The children bit the tube with maximum force three times successively for 5 s, with a 10 s interval among each bite, and the sign was sent directly to the computer. The highest value of the three, for each patient, was considered. Analysis of variance evaluated difference among the three groups. The means of maximum bite force were 213 17, 249 63 and 241 19 N for the groups, respectively, and there were no significant statistical differences among them (P > 0.05). The analysis of correlation showed that the weight, height and bite force presented weak positive correlation (r=0.24 and 0.23). It was concluded that in the studied groups the type of occlusion did not affect the maximum values of the bite force and body variables had a small influence in this magnitude.

Analysis of Variance↗
PubMed1995

[Relationships between biting force and the morphology of the maxilloface].

The maximum biting force of 40 male students aged 26.1 +/- 3.9 years was assessed to evaluate the relationships between biting force and the morphology of the maxilloface. The evaluations were made using roentgenographic cephalogram measurements and oral model measurements. The results obtained were as follows. 1. The subjects who had strong maximum biting force (MBF) were those with high posterior facial height, high posterior inferior facial height, long length from the Ar-Me line to the gonion, and long length between the adhesion of the masseteric muscles. 2. The subjects who had strong MBF had a small gonial angle, and their occlusal plane and mandibular plane approached the anterior cranial base and eye-ear-plane, that is, the subjects with strong MBF were considered to be persons with a deep overbite. 3. There was a significant positive correlation between MBF and discrepancy values using oral model measurements (p < 0.01). No significant correlations were noted between MBF and the sum of teeth size. 4. There was a significant positive correlation between MBF and maximum grip strength (p < 0.01), back strength (p < 0.01) and the long jump (p < 0.05), and there was a significant negative correlation between MBF and 50m running (p < 0.01), but no significant correlations were noted between MBF and 1500m running.

Adult↗