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PubMed2006

Bite force, occlusal contact area and masticatory efficiency before and after orthognathic surgical correction of mandibular prognathism.

The purpose of this study was to evaluate bite force, occlusal contact area and masticatory efficiency before and after sagittal split ramus osteotomy in 27 patients with mandibular prognathism, in comparison with 27 control subjects with normal occlusion. Bite force and occlusal contact area were simultaneously measured with a computerized occlusal analysis system, the Dental Prescale system. Masticatory efficiency was estimated by a low-adhesive colour-developing chewing-gum system. The data were collected at initial medical consultation, immediately before surgery, and at 6 weeks, 3 months, 6 months, 1 year and more than 2 years after surgery. Both bite force and occlusal contact area of the patients before surgery were significantly less than those of the controls. Although all three parameters had improved after orthognathic surgery, the bite force and occlusal contact area did not reach the values of the controls within 2 years postoperatively; masticatory efficiency at 2 years after surgery drew near to control levels. Bite force correlated with occlusal contact area in the patients postoperatively, whereas masticatory efficiency did not correlate with either of the other two parameters. These results suggest that further adjustment of occlusion and mechanical advantage should be considered before the end of treatment.

Adolescent↗
PubMed2001

Migraine and masticatory muscle volume, bite force, and craniofacial morphology.

The purpose of this investigation was to compare the masticatory muscle volume, bite force, and craniofacial morphology of migrainous subjects with age- and sex-matched controls. Ten adult dentate migraineurs were matched with 10 dentate age- and sex-matched controls. The groups consisted of nine women and one man (mean age, 43 years; range, 29 to 51 years). Volumetric analysis of the masseter and medial pterygoid muscles was performed using magnetic resonance imaging. Craniofacial morphology was analyzed from standard cephalometric radiographs using 30 angular and linear variables. Recordings of bite force were made using a strain gauge transducer. There was a significant difference in the volume of both masseter and medial pterygoid muscles between the two subject groups (P<.0001), with the muscles of the migraineurs nearly 70% larger. The migraineurs recorded significantly higher maximal bite forces (P<.0001) than did the controls. No significant differences for any craniofacial morphological measurement were demonstrated between the two groups. It was concluded that the migraineurs had larger masseter and medial pterygoid muscle volumes, and greater bite forces than the controls, which could not be explained by any change in craniofacial morphology.

Adult↗
PubMed1995

Measurement of bite force in dogs: a pilot study.

A force transducer was developed to measure bite force in dogs. A total of 101 readings was obtained from 22 pet dogs ranging in size from 7 to 55 kg. Bite forces ranged from 13 to 1394 Newtons with a mean for all dogs of 256 Newtons and a median of 163 Newtons. Most measurements fell within the low end of the range, with 55% of the biting episodes less than 200 Newtons and 77% less than 400 Newtons.

Animals↗
PubMed1979

Functional state, bite force and postural muscle activity in patients with osseointegrated oral implant bridges.

The function of the masticatory system of 13 women, aged 42-59 years, with osseointegrated oral implant bridges (OIB) made within the last seven years was compared with that of 10 matched dentate controls by means of a questionnaire, clinical examination, bite force measurements and electromyographic recordings of biting and of postural muscle activity. Both groups were satisfied with their masticatory capacity according to the questionnaire. The clinically determined state of the masticatory system, as judged from the clinical dysfunction index, was normal in both groups. Three levels of bite force 1) gentle biting, 2) biting as when chewing and 3) maximal biting, were recorded with a bite force apparatus and electromyographically. There was no statistically significant difference between the groups at any level of bite force for any of the methods of registration. Nor was there any difference of the two groups in the activity of the masticatory muscles with the mandible in the postural position. It is concluded that patients with osseointegrated oral implant bridges have a masticatory muscle function equal to or approaching that of patients with natural teeth, or with tooth-supported bridges, with the same number of chewing units as the OIB-patients.

Adult↗
PubMed2000

EMG activities of two heads of the human lateral pterygoid muscle in relation to mandibular condyle movement and biting force.

Electromyographic (EMG) activities of the superior (SUP) and inferior heads (INF) of the lateral pterygoid muscle (LPT) were recorded in humans during voluntary stepwise changes in biting force and jaw position that were adopted to exclude the effects of acceleration and velocity of jaw movements on the muscle activity. The SUP behaved like a jaw-closing muscle and showed characteristic activity in relation to the biting force. It showed a considerable amount of background activity (5-32% of the maximum) even in the intercuspal position without teeth clenching and reached a nearly maximum activity at relatively lower biting-force levels than the jaw-closing muscles during increment of the biting force. Stretch reflexes were found in the SUP, the function of which could be to stabilize the condyle against the biting force that pulls the condyle posteriorly. This notion was verified by examining the biomechanics on the temporomandibular joint. The complex movements of the mandibular condyle in a sagittal plane were decomposed into displacement in the anteroposterior direction (Ac) and angle of rotation (RAc) around a kinesiological specific point on the condyle. In relation to Ac, each head of the LPT showed quite a similar behavior to each other in all types of jaw movements across all subjects. Working ranges of the muscle activities were almost constant (Ac <3 mm for the SUP and Ac >3 mm for the INF). The amount of EMG activity of the SUP changed in inverse proportion to Ac showing a hyperbola-like relation, whereas that of the INF changed rather linearly. The EMG amplitude of the SUP showed a quasilinear inverse relation with RAc in the hinge movement during which the condyle rotated with no movement in the anteroposterior direction. This finding suggests that the SUP controls the angular relationship between the articular disk and the condyle. On the other hand, the position of the disk in relation to the maxilla, not to the condyle, is controlled indirectly by the INF because the disk is attached to the condyle by tendinous ligaments.

Adult↗
PubMed2003

Changes in bite force and dentoskeletal morphology in prognathic patients after orthognathic surgery.

OBJECTIVE: We sought to evaluate the changes in bite force and dentoskeletal morphology in prognathic patients after orthognathic surgery. STUDY DESIGN: Twenty-four patients underwent orthognathic surgery to correct Class III skeletal and dental malocclusions. Ten patients who underwent Le Fort I and bilateral sagittal split ramus osteotomy of the mandible (ie, surgical correction of 2 jaws) and 14 patients who underwent only bilateral sagittal split ramus osteotomy (ie, surgical correction of 1 jaw) were compared. Bite force was measured preoperatively and at 3, 6, and 12 months postoperatively. The dentoskeletal morphology was assessed through lateral cephalograms obtained preoperatively and 12 months postoperatively. RESULTS: Twelve months postoperatively, the bite force was significantly greater in the patients who underwent surgery on 1 jaw than in the patients who underwent surgery on 2 jaws. Significant decreases in the gonial angle, occlusal plane angle, and anterior facial height were observed postoperatively in the patients with 1 surgically corrected jaw, but not in the patients with 2 surgically corrected jaws. Patients with 2 surgically corrected jaws experienced a greater increase in the Frankfort mandibular plane angle and a greater decrease in the posterior facial height than did those with 1 surgically corrected jaw. CONCLUSION: The difference in the preoperative-to-postoperative change in dentoskeletal morphology between the 2 groups is one of the factors responsible for the significant difference in postoperative bite force between the 2 groups.

Adolescent↗
PubMed2001

Temporomandibular disorders in relation to craniofacial dimensions, head posture and bite force in children selected for orthodontic treatment.

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.

Adolescent↗
PubMed2000

Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: a preliminary report.

PURPOSE: This study examined bite force and occlusal contact area in prognathic patients before and after bilateral sagittal split ramus osteotomy of the mandible using a newly developed pressure-sensitive sheet (Dental-Prescale, Fuji Photo Film Co, Tokyo, Japan). PATIENTS AND METHODS: Twenty-five prognathic patients were examined. Bite force and occlusal contact area were measured preoperatively, at 2, 4, and 8 weeks, and at 3 and 6 months after surgery. The bite force and occlusal contact area of 20 healthy subjects were also measured. RESULTS: Both bite force and occlusal contact area of the patients were the lowest 2 weeks after surgery and recovered to the preoperative level between 8 weeks and 3 months. Subsequently, they increased slowly and exceeded the preoperative level at 6 months after surgery. However, even at 6 months, both the bite force and the occlusal contact area of the patients were still only about half or less than that of healthy subjects. CONCLUSION: This pressure-sensitive device can be used as a simple indicator of postoperative recovery and occlusal improvement in patients following orthognathic surgery.

Adolescent↗
PubMed1998

Self-assessed masticatory ability in relation to maximal bite force and dental state in 80-year-old subjects.

By means of a questionnaire, clinical examination and force recordings, the relationships between self-assessed masticatory ability, dental state and bite force were studied in 160 80-year-old persons, 74 men and 86 women. The subjects were in general satisfied with their masticatory ability and 70% had no problems, while 6% reported three or more problems with mastication. Half of the subjects were dentate without removable prostheses and almost one-third had 20 or more natural teeth. The edentulous persons (about one-fifth of all) reported more problems related to mastication than the other dentition groups. The maximal bite force varied much and exhibited a significant correlation to the number of remaining teeth and dental state. The self-assessed masticatory ability was only weakly correlated with dental state and bite force. It was concluded that many subjects with few or no remaining teeth and/or removable dentures had only few complaints of impaired masticatory function and showed a good adaptation to an impaired dental status and small maximal bite force.

Adaptation, Physiological↗
PubMed2005

Periapical biomechanics and the role of cyclic biting force in apical retrograde fluid movement.

AIM: To investigate the stress distribution pattern in the periapical region caused by biting forces and to study the role of cyclic biting loads on periapical fluid movement. METHODOLOGY: In the first part, a digital photoelastic experiment was conducted to study stress distribution in the periapical region. In the second, 20 maxillary central incisors were selected and divided into three main groups: normal intact teeth (group 1), tooth specimens in which the root canal was enlarged and maintained wet (group 2), and tooth specimens in which the root canal was enlarged and maintained dry (group 3). The tooth specimens were placed in a polycarbonate support with a cavity filled with a sponge soaked in methylene blue solution to simulate a periapical defect with exudate. During testing, the specimens were placed in a water bath at 37 degrees C, and were loaded cyclically with a load of 20 N, at a rate of 72 cycles min(-1), to a maximum of 20,000 cycles. The specimens were then sectioned and evaluated for retrograde fluid movement using light microscopy. The data were analysed using one-way anova (post hoc tests). RESULTS: Digital photoelastic experiments showed that the compression of teeth produced bending stresses in the periapical region. Testing with cyclic loads demonstrated retrograde fluid movement into the apical portion of the root canal and extraradicular region in all groups. There was a significant difference amongst the apical retrograde fluid movement displayed by different groups (<0.01). Group 2, in which the root canal was enlarged and maintained wet showed maximum retrograde fluid movement, whilst group 3, in which the root canal was enlarged and maintained dry showed the least retrograde fluid movement. CONCLUSIONS: Biting forces would cause bending of the periapical bone and cyclic biting forces would contribute to retrograde fluid movement into the root canal space and extraradicular region.

Alveolar Process↗
PubMed1999

Bite force, endurance and masseter muscle fatigue in healthy edentulous subjects and those with TMD.

It is well known that bite force and EMG activity are considerably reduced in edentulous patients, but the susceptibility of their jaw-closing muscles to localized fatigue is less certain. This information is even less clear for edentulous subjects who have TMD. Eleven healthy edentulous subjects and 10 edentulous subjects with TMD participated in this study. Maximum bite force was measured first, with the transducer placed on the canine-first premolar region bilaterally, and then two rapid relaxations were made from a brief voluntary clench to 50% of maximum. A sustained voluntary clench of 50% of maximum was then maintained and endurance time was noted. EMG was recorded from both masseter muscles and the median frequency of the power spectrum of the EMG from 2 s at the beginning of the sustained clench and 2 s at the end was subsequently calculated. Two more rapid relaxations from brief clenches were performed immediately after the sustained clench. The mean maximum bite force in the healthy group was 115 N (SD +/-41) and in the TMD group was 75 N (SD +/-22), this difference being significant (P = 0.0013). The mean endurance time in the healthy group was 86 s (SD +/-51) and in the TMD group was 63 s (SD +/-20). The percentage change in the median frequency in the healthy group as a result of the sustained contraction was 6% (left) and 8.6% (right) and in the TMD group was 13.9% (left) and 12.8% (right). The percentage change in the mean relaxation half time for the healthy group was 28.5% and for the TMD group was 72%, a significant difference (P = 0.0046). It was apparent that the maximum bite force was low in edentulous subjects and was further reduced in edentulous TMD subjects; endurance time was reduced in TMD subjects; fatigue resistance of the masseter muscles was reduced in TMD subjects.

Aged↗
PubMed1998

Evaluation of trismus, bite force, and pressure algometry after third molar surgery: a placebo-controlled study of ibuprofen.

PURPOSE: This study evaluated trismus, bite force, and pressure algometry as measures of analgesic efficacy after third molar removal. PATIENTS AND METHODS: Fifty-seven patients (36 females and 21 males) developed at least moderate pain after surgical removal of a mandibular third molar and were given either ibuprofen, 400 mg (n = 26), or placebo (n = 31) in a double-blind study. Pain intensity and pain relief were rated on a five-point verbal rating scale during the 4-hour study period. Recordings of trismus, bilateral pressure pain detection and tolerance thresholds, and bite force were performed before surgery, at medication, and hourly for 4 hours. Changes in the functional variables were calculated as percent change from baseline (before surgery). RESULTS: The pain intensity and pain relief ratings showed significant differences between the ibuprofen- and placebo-treated patients in the 4-hour study period. The changes in trismus, bite force, and pressure pain thresholds were in accordance with these pain ratings. Pressure pain detection threshold on the operated side was significantly lower in the placebo-treated patients compared with the ibuprofen-treated patients 2 and 3 hours after medication, whereas pressure tolerance threshold showed a significant difference after 2 hours. Bite force on the operated side was significantly less reduced 3 hours after treatment with ibuprofen when compared with placebo. CONCLUSIONS: The functional measures used support the results obtained by rating of pain intensity and pain relief, and could be of value as measures of the efficacy of an analgesic to reduce functional impairment caused by postoperative pain.

Adolescent↗
PubMed1985

Regression analysis of electromyographic activity of masticatory muscles versus bite force.

Electromyographic (EMG) activity of the superficial masseter and the anterior temporal muscles versus the bite force was studied in 10 young women. They were fully dentate and had no dysfunction of the stomatognathic system. The descending part of the trapezius muscle was also chosen for EMG registration. The average bite force between the first molars was 396 N (Newton). Steeper slopes for the EMG versus force regression curve at high contraction levels than at low contraction levels for the superficial masseter muscle may indicate that this muscle has a recruitment pattern that differs from that of the anterior temporal muscle. In the case of the anterior temporal muscle there was no difference between the slopes for the EMG-force regression at low and high contraction levels. There was significantly increased activity in the descending part of the trapezius muscle mainly during high bite force levels in half the subjects.

Adult↗
PubMed2001

The effects of isometric exercise on maximum voluntary bite forces and jaw muscle strength and endurance.

The effects of training and exercise on the strength and endurance of limb muscles has been investigated extensively, but the response of the jaw muscles to exercise remains poorly known. The purpose of this study was to determine whether short-term isometric training increases strength and endurance of the superficial masseter and anterior temporalis muscles. Maximum and submaximum voluntary bite forces and corresponding electromyographic (EMG) activity were measured in 28 young adults, randomly divided into exercise and non-exercise (control) groups. Subjects in the exercise group performed isometric clenches against a soft maxillary splint for five 1-min sessions per day over a 6-week period. After exercise, subjects increased their maximum bite forces by 37%, but control subjects' bite forces also increased by 25%. After exercise, EMG levels per unit of bite force generally decreased, but similar decreases were also seen in the non-exercised controls. Masseter muscle activity levels during standardized 10-kg bites decreased after 6 weeks of exercise. Fatigue resistance increased significantly with exercise but did not differ significantly from control values after 6 weeks of exercise. The results of this study indicate that increases in maximum bite force can be easily produced with training, but that actual strengthening of the jaw muscles is more difficult to achieve.

Adult↗
PubMed1992

Level of accuracy and degree of precision in attempting to maintain steady levels of biting force.

The primary purpose of this study was to assess the level of accuracy (bias) and degree of precision for a group of 24 normal subjects attempting to maintain a constant biting force at levels of 100 gm, 500 gm, 1000 gm and 2000 gm for a period of 10 s each. Accuracy is defined as the difference between subjects' actual level of biting force and the target value they were trying to achieve. Precision is the level or range of variability demonstrated by the subjects while attempting to bite with a constant level of force. Subjects' performance relative to accuracy and precision was also compared when using the central incisors vs. the first permanent molars. Assessment of bite force was measured using a specially designed strain gauge scale which permitted subjects to visually monitor when their biting force equalled a preset resistance. Each subject was instructed to bite on the end of a plastic sheathed steel beam with enough force to activate the indicator needle on the voltage meter to its central position and to try to maintain a constant level of biting force (by attempting to keep the indicator needle steady in its central position). No significant (P > 0.05) differences were found in mean accuracy in bite force for gender or specific teeth used in the biting task. However, a significant difference (P < 0.0001) in mean accuracy in bite force was found to exist between the target levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2001

Changes in bite force and occlusal contact area after orthognathic surgery for correction of mandibular prognathism.

OBJECTIVE: This study examined the long-term changes of bite force and occlusal contact area in patients with prognathous after orthognathic surgery with a newly developed pressure-sensitive sheet (Dental-Prescale; Fuji Photo Film Co). STUDY DESIGN: Fifty-seven patients with prognathous were examined. Bite force and occlusal contact area were measured just before operation and at 2 weeks, 1 month, 3 months, 6 months, 1 year, 2 years, and 3 years after operation. Forty control subjects with normal occlusion were also measured. RESULTS: The bite force and occlusal contact area of the patients were significantly greater than the preoperative level at 1 year, 2 years, and 3 years after operation. However, they were still significantly lower than the control subject level even at 3 years after operation. CONCLUSIONS: This study suggests that orthognathic surgery improves the bite force and occlusal contact area of patients with prognathous. However, at 3 years from the time of operation, patients had not reached control subject levels.

Adolescent↗
PubMed1994

Bite force and dentofacial morphology in men with severe dental attrition.

Patients with severely worn dentition were interviewed and clinically examined, and only those were included who had no or minimal subjective symptoms or clinical signs of craniomandibular disorder. During a 14-month screening period, only 7 patients fulfilled the inclusion criteria; all were men. Maximal bite force was measured in the molar regions and in the incisal region. Facial morphology was evaluated from lateral cephalometric radiographs, and the form of dental arches from dental casts. Average maximal bite force in the molar region was 911 N and in the incisal region 569 N. The most characteristic findings concerning bite force were the high force levels in the incisal region and an incisal/molar bite-force ratio of 63%. The facial morphology of the patients was rectangular, with an anteriorly rotated mandible, small anterior face height, and great interincisal angle. Moreover, the form of the maxillary dental arch was more rectangular than normal. The high bite forces of these patients, especially in the incisal area, can probably be explained by strong masticatory muscles and mechanically favorable skull morphology, which in its turn has been influenced by the surrounding muscles.

Adult↗
PubMed2005

Evolution of bite force in Darwin's finches: a key role for head width.

Studies of Darwin's finches of the Galapagos Islands have provided pivotal insights into the interplay of ecological variation, natural selection, and morphological evolution. Here we document, across nine Darwin's finch species, correlations between morphological variation and bite force capacity. We find that bite force correlates strongly with beak depth and width but only weakly or not at all with beak length, a result that is consistent with prior demonstrations of natural selection on finch beak morphology. We also find that bite force is predicted even more strongly by head width, which exceeds all beak dimensions in predictive strength. To explain this result we suggest that head width determines the maximum size, and thus maximum force generation capacity of finch jaw adductor muscles. We suggest that head width is functionally relevant and may be a previously unrecognized locus of natural selection in these birds, because of its close relationship to bite force capacity.

Animals↗