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PubMed1990

Unilateral, isometric bite force in 8-68-year-old women and men related to occlusal factors.

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 or signs 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 (P less than 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, P less than 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.

Adolescent↗
PubMed1983

A method of bite force measurement in primates.

A bite force transducer consisting of two differential strain beams with four strain gages in a full bridge configuration was modified for measuring occlusal forces in rhesus monkeys. A procedure of muscle stimulation (20-50 V, 60 Hz, and 0.8 ms duration) produced maximal unilateral masticatory muscle contraction when stimulating electrodes were placed in the masseter muscle. Tests of this procedure revealed reproducible results and a potential for use in studies of the force of isometric contraction of the masticatory muscles in normal and experimentally altered macaques and other primates.

Animals↗
PubMed1996

Coupling electrical and mechanical outputs of human jaw muscles undertaking multidirectional bite-force tasks.

Previous studies have identified both linear and curvilinear relations between increasing bite-force magnitude and the integrated electromyogram (EMG) of jaw-closing muscles. In an attempt to explain the discrepancy, bite forces of incrementally increasing magnitude were produced on the right-hand side in five specified directions by eight humans. Linear regression lines were fitted to normalized EMG activities of the left and right masseter and temporalis muscles against increasing bite-force magnitude in each direction. The grand mean of linear correlation coefficients was 0.79 (+/- 0.11 SD), suggesting an overall linear relation. Each set of individual data was fitted with polynomial lines up to the third order. The best fit was selected by statistical significance of coefficients and the least-square analysis of the sum of residues for each fitted line; 62% of individual data-sets were best fitted with linear regression lines, 31% with quadratic lines and the remaining 7% with cubic lines. Repeated analysis of residue variance of the pooled data showed that either a linear or quadratic line fitted every data set except one, for which a cubic line had the best fit. Working-side muscles had significantly larger linear correlation coefficients than corresponding balancing-side muscles for most bite-force directions. Analysis of variance of linear correlation coefficients revealed that the degree of linearity often depended upon the roles played by a muscle in producing forces in different directions. It appears that linearity or non-linearity of the EMG force relation is a determinant, among other variables, of the direction of the resultant force.

Adult↗
PubMed2004

Association of bite force with ageing and occlusal support in older adults.

OBJECTIVES: The purpose of this study was to investigate the effect of ageing, occlusal support and TMJ condition and general health status on bite force in older adults. METHODS: The study sample consisted of 850 independently-living people over the age of 60 years. Bilateral maximal bite force in the intercuspal position was measured with pressure sensitive sheets. TMJ noise by palpation and limitation of mouth opening (less than 40 mm) were assessed. Subjects were grouped into three categories by occlusal support according to the Eichner Index. RESULTS: A multiple logistic regression analysis showed that whether participants had low bite force or not was significantly associated with gender, age, self-rated general health and occlusal support, but not TMJ noise or mouth opening limitation. Overall bite force showed a statistically significant but weak negative Spearman's correlation with age (r=-0.24, p<0.001). However, there was no significant correlation between age and bite force in the Eichner C group for males or in any of the Eichner classification for females. CONCLUSIONS: Decline of occlusal support and general health might translate into reduction of bite force with ageing in older adults. Since tooth loss is not physiological ageing but pathological ageing, it cannot be shown that reduction of bite force is a natural effect of ageing.

Age Factors↗
PubMed1998

Changes in bite force and occlusal contacts in patients treated for mandibular prognathism by orthognathic surgery.

PURPOSE: The purpose of this study was to evaluate changes in bite force and occlusal contacts before and after orthognathic surgery in patients with mandibular prognathism and to compare the findings with those in controls with normal occlusion. PATIENTS AND METHODS: Bite force and occlusal contacts were analyzed in 23 (7 male and 16 female) patients with mandibular prognathism before and after sagittal split ramus osteotomy, and in 20 (10 male and 10 female) controls with normal occlusion. The bite force and occlusal contacts were simultaneously measured by a computerized occlusal analysis system, the T-Scan system, immediately before surgery, and at 6 weeks, 3 months, 6 months, and 1 year postoperatively. RESULTS: Both the bite force and occlusal contacts in the patients were significantly less than those in the controls before surgery. Although both the bite force and occlusal contacts in the patients were improved by the orthognathic surgery, neither approached the level in the controls within 1 year. Bite force was correlated with the number of occlusal contacts in both patient and control groups. CONCLUSION: The postoperative masticatory function does not reach control levels even 1 year after the orthognathic surgery for mandibular prognathism. Therefore, further adjustment of the occlusion should be considered before the end of treatment.

Adult↗
PubMed2001

The relationship between surgical changes in dentofacial morphology and changes in maximum bite force.

PURPOSE: This study determined whether patients with greater surgical changes, and presumably greater normalization of their skeletal morphology, showed greater increases in their maximum voluntary bite forces after orthognathic surgery. PATIENTS AND METHODS: A total of 104 adult patients (32 males and 72 females) treated with 1 of 8 different orthognathic surgical procedures were examined. Patients' presurgical and postsurgical morphologic and biomechanical measurements were taken from lateral cephalograms. Measurements known to be related to maximum bite force were used in the analysis. Patients' presurgical and postsurgical maximum bite forces were measured at 8 tooth positions (ie, right and left incisors, canines, premolars and molars). RESULTS: Presurgical and postsurgical morphology and biomechanics variables were strongly correlated with each other, suggesting that orthognathic surgery produced relatively little change in patients' overall craniofacial form. Maximum voluntary bite forces were primarily correlated with variables relating to jaw size-both before and after surgery. No correlations were noted between the increases in maximum voluntary bite forces and surgically produced changes in skeletal morphology and the biomechanics variables. CONCLUSIONS: Factors other than surgically produced changes in skeletal morphology are responsible for increases in maximum voluntary bite force after orthognathic surgery.

Adult↗
PubMed1996

Alteration in the bite force and EMG activity with changes in the vertical dimension of edentulous subjects.

The bite force and EMG activity of jaw closing muscles were studied at seven different vertical jaw positions around the occlusal vertical dimension (OVD) in 10 edentulous subjects. When the masseteric EMG activity was maintained at constant values (40% and 20% of the maximum activity at the OVD), the bite force increased in proportion to increase of the vertical dimension. On the other hand, when the bite force was maintained at constant values (4 kg and 8 kg), the EMG activities of the jaw closing muscles decreased, with an increase of the vertical dimension. These results indicate that the OVD is not the position at which the most efficient exertion of the bite force is obtained.

Adaptation, Physiological↗
PubMed2002

[Expression of IL-6 and it's mRNA transcription in the process of rat periodontium remodeling influenced by various bite forces].

OBJECTIVE: To study the expression of IL-6 in periodontal ligament fibroblasts (PLF) and osteoblasts in order to explain the molecular mechanism of the bite forte on periodontium remodeling. METHODS: A rat model of different bite forces was established to study the expression of IL-6 and IL-6 mRNA in the PLF and osteoblasts with immunohistochemical (IHC) and in situ hybridization (ISH) techniques. RESULTS: In the group of disuse bite force, the expression of IL-6 and IL-6 mRNA in the PLF and osteoblasts enhanced apparently compared with that in the group of normal bite force. The gray level values enhanced respectively from 6.5886 +/- 1.6 to 38.8381 +/- 9.5 and from 11.8337 +/- 2.8 to 57.2623 +/- 13.6. The loosely arrangement of periodontal fibers and the resorption of alveolar bone were observed in histological study. In the group of compensation bite force, the same result was observed with IHC and ISH, the gray level values enhanced respectively from 6.3119 +/- 1.5 to 45.5456 +/- 11.1 and from 11.7714 +/- 2.8 to 81.9391 +/- 19.5, but the increase of periodontal fibers, the resorption and formation of alveolar bone were observed simultaneity in histological study. CONCLUSIONS: With the change of bite force, the expression of IL-6 and IL-6 mRNA in PLF and osteoblasts presents a certain regulation. IL-6 may play important roles in the effect of bite force on periodontium remodeling.

Animals↗
PubMed1979

EMG, bite force, and elongation of the masseter muscle under isometric voluntary contractions and variations of vertical dimension.

The relation EMG activity, bite force, and muscular elongation was studied in eight subjects with complete natural dentition during isometric contractions of the masseter muscle, measured from 7 mm to almost maximum jaw opening. EMG was registered with superficial electrodes and bite force with a gnathodynamometer. In series 1, recordings of EMG activity maintaining bite force constant (10 and 20 kg) show that EMG is high when the bite opening is 7 mm, decreases from 15 to 20 mm, and then increases again as jaw opening approaches maximum opening. In series 2, recordings of bite force maintaining EMG constant show that bite force increases up to a certain range of jaw opening (around 15 to 20 mm) and then decreases as we approach maximum jaw opening. Results show that there is for each experimental subject a physiologically optimum muscular elongation of major efficiency where the masseter develops highest muscular force with least EMG activity.

Adult↗
PubMed1988

A comparison of stimulated bite force after mandibular advancement using rigid and nonrigid fixation.

This study evaluated maximum stimulated molar bite force following advancement of the mandible in 17 adult Macaca mulatta using rigid and nonrigid fixation techniques. Cephalometric analysis was also performed to determine the amount of proximal segment rotation. Analysis of the bite force showed the animals whose mandibles were advanced using rigid fixation to have significantly greater bite force at six weeks postsurgery when compared to those animals who underwent mandibular advancement and six weeks of maxillomandibular fixation. By the ninth postoperative week, there was no longer any significant difference between the two groups, indicating a rapid recovery of muscle function in the animals whose mandibles were immobilized following advancement. Both groups, however, had significant decreases in bite force at 12 weeks postsurgery when compared to preoperative values. Neither group had a significant amount of proximal segment rotation from the surgery.

Animals↗
PubMed1982

Effect of bite force on the masseteric electromyographic silent period in man.

The duration of the masseteric EMG silent period as induced by tapping on the chin was measured at different levels of sustained bite force. Under both open bite and normal occlusion, the duration of the silent period was inversely related to the magnitude of the bite force. For bite force of the same magnitude, the value of the silent period remained relatively constant for the same subject in different trials (SEM congruent to 1 per cent), whereas the absolute values of the silent periods ranged far and wide for different individuals even under similar experimental conditions.

Adolescent↗
PubMed1998

[Reproducibility of maximal bite force distribution over dentition].

We have reported that the analysis of the maximal bite force distribution over dentition was available for objective evaluation of prosthodontic treatment. The purpose of this study was to investigate the reproducibility of occlusal force distribution in maximal voluntary clenching. The maximal bite forces of 10 normal subjects with complete dentition were measured at close to intercuspation using Dental Prescale System. The measurements were performed two times with an interval of 3 years. The differences of the distributed occlusal force and the location of occlusal load center, i.e., the center of balance of distributed occlusal force, between 1st and 2nd measurement were evaluated by Mann-Whitney signed rank test (p < 0.01). The coefficient of variance was calculated from the results of two measurements in order to assess the measurement error. The statistical significant differences were not found in all measurement protocol and the coefficient of variance of the location of occlusal load center showed a remarkably small value (4.0%). The mean of absolute differences in the location of occlusal load center between two measurements were almost 4.0 mm anteroposteriorly and right-left. These results suggested that the maximal bite force measurement and the analysis of occlusal force distribution using Dental Prescale System were useful for the longitudinal evaluation of masticatory function and prosthodontic treatment. The analysis of occlusal load center was shown to be the most reliable method for evaluation. The reliable range for the reproducibility of occlusal load center was also shown.

Adult↗
PubMed1996

Bite forces before and after surgical correction of mandibular prognathism.

PURPOSE: The purpose of this investigation was 1) to compare morphologic parameters and voluntary bite forces between controls and a sample of patients with mandibular prognathism before surgical correction, and 2) to examine how these patients' bite forces adapt after treatment. PATIENTS AND METHODS: Twenty-four prognathic patients were compared with 24 controls before and up to 3 years after mandibular setback surgery. Measures of skeletal morphology and maximum isometric bite force were made on all subjects over time. Statistical analysis compared the controls, the patients before surgery, and the patients after surgery. RESULTS: Surgical shortening of the mandible averaged 4.1 mm, bringing most skeletal measures into the normal range. Before surgery, the jaw muscle mechanical advantages for patients were significantly smaller than for controls; surgery did not significantly change this relationship. Before surgery the patients had maximum isometric bite forces that were significantly less than those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 to 3 years. CONCLUSIONS: The results of this study suggest that correction of mandibular prognathism by mandibular setback surgery produces some significant functional benefits.

Adolescent↗
PubMed2004

Maximum bite force and related dental status in children with deciduous dentition.

Six hundred seventy-six Taiwanese children with deciduous dentition were sampled for maximum bite force and related dental status. Sixty-seven percent of children had at least one decayed tooth. The mean number of decayed teeth of all children was 2.97+/-3.58, and the mean plaque index of the right maxillary central incisor was 2.00+/-0.75. Twenty-seven percent of children had occlusal anomalies. Boys had a statistically significantly larger maximum bite force than did girls. Children with normal occlusion had statistically significantly larger maximum bite forces than did children with malocclusion. A statistically positive correlation was found between the number of decayed teeth and the plaque index. However, a statistically negative correlation was found between the number of decayed teeth and the maximum bite force and between the plaque index and the maximum bite force.

Bite Force↗
PubMed1987

The control of bite-force in relation to jaw position and load in man.

Whether bite-force is controlled independently of mouth opening, and jaw position is controlled independently of the imposed load of the mandible, was examined. Subjects were asked to match, at 15 and 30 mm inter-incisor distance, reference forces of 2, 10 and 50 N exerted at 15 and 30 mm mouth opening. They were able to grade bite-force, as matches made of the different forces hardly overlapped. However, at a 5 per cent level of significance in 90 per cent of the cases, the matches were dependent on jaw position. The imprecision of the 2 N matches was about 40 per cent of the reference force; those of the 10 and 50 N matches were about 25 per cent. Thus a mechanism controlling bite-force with any degree of precision is absent in the jaw system.

Bite Force↗
PubMed1995

Craniofacial morphology, occlusal traits, and bite force in persons with advanced occlusal tooth wear.

The aim of this study was to investigate the dentofacial structure, the occlusal traits, and the bite force in subjects with advanced occlusal wear. The material comprised 54 adults, 30 men (mean = 40 years, range 16 to 61) and 24 women (mean = 28 years, range 18 to 47), most of whom had a full or near-full complement of natural teeth, and the presence of occlusal wear. Craniofacial structure was studied on lateral cephalograms. Occlusal traits were examined on study casts, these serving also for an evaluation of occlusal wear to be carried out by using an ordinal scale. Bite forces were recorded at differing force levels (maximum biting, "biting as when chewing" and "light biting") and occlusal positions. Although maximum bite force and endurance time did not differ significantly between men and women, the level of bite force was high compared with other samples. The craniofacial structure of the sample was characterized by a deviation in the vertical direction, a small angle between the mandibular-palatal planes and a small gonial angle, as compared with Swedish adult norms. No significant differences were found in anteroposterior relationships between persons with advanced wear and normal standards. The results support the hypothesis that functional hyperactivity of the masticatory system imposed increased stress on the bony structures of the craniofacial complex with possible influences on its structure.

Adolescent↗
PubMed2001

The association between research diagnostic criteria for temporomandibular disorder findings and biting force and endurance in patients with temporomandibular disorders.

OBJECTIVE: This study was designed to evaluate the association between examination findings based on Research Diagnostic Criteria for Temporomandibular Disorders and performances on bite force and endurance tasks. METHODS: Subjects were 126 patients with temporomandibular disorder and 34 pain-free controls. A subset of patients with temporomandibular disorder (n = 56) also were evaluated following a brief conservative 4-week treatment intervention. RESULTS: A multivariate analysis of variance indicated that female patients (P <.001) but not males (P =.17) had lower bite forces than age- and gender-matched controls. Dental examination findings were significantly but modestly predictive of bite task performance (R2 = 0.175), with higher joint pain and smaller maximum unassisted jaw opening associated with lower bite force. The brief treatment interventions resulted in both self-reported and clinically determined improvements. Clinical and self-reported improvement significantly predicted pre-post treatment changes in biting force among female subjects (R2 = 0.237). Specifically, reduction in joint palpation pain and self-reported pain (McGill Pain Questionnaire short form) were the primary predictors of increases in bite force. The improvement in biting force was modest (mean = 7 lb), and the force levels of female patients remained lower than those of control subjects. Treatment did not significantly increase endurance time. DISCUSSION: The brief conservative treatments used resulted in improvements in pain and jaw opening, and 81.8% of patients reported moderate to major improvement. The modest association of the bite task with Research Diagnostic Criteria for Temporomandibular Disorders examination findings and treatment improvement in this heterogeneous sample suggests that the bite and endurance tasks have limited diagnostic utility and sensitivity to treatment effects.

Journal Article↗
PubMed1979

Bite force and oral function in complete denture wearers.

Oral function was evaluated in complete denture wearers by using a questionnaire, clinical examination and bite force measurements. Ten patients with satisifactory and ten with unsatisfactory dentures were studied and six of the latter patients were reexamined 1 year after the insertion of new dentures. The bite force values were compared with those obtained in ten dentate controls. No significant differences in bite force were found between the satisfactory and unsatisfactory denture groups. Individual values varied much in both groups. The six patients re-examined were satisfied with their new dentures and thought they had improved chewing but no significant increase of bite force was found. The maximal bite force was 5-6 times greater in the dentate subjects than in the denture wearers. Edentulous persons are very handicapped in masticatory function and even clinically satisfactory complete dentures are poor substitutes for natural teeth.

Adult↗