[Experimental studies on the exerting mechanism of masticatory muscle force and the occurring mechanism of biting force].
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Dental Stress Analysis↗
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Effect of occlusal morphology on the accuracy of bite force measurements using thin film transducers.
PURPOSE: Occlusal transducer foils using piezoelectricity or pressure-dependent electric resistance are potential candidates for a measurement system for both absolute levels and changes in bite force. This preliminary in vitro study evaluated the possible usefulness of such transducer foils in the assessment of occlusal forces in centric occlusion. MATERIALS AND METHODS: Piezoelectric force transducer foils 33 microm thick were placed between pairs of teeth with the dentition in centric occlusion. Occlusal forces were recorded in five patients, who were instructed to bite as hard as possible for about 1 second. Acrylic resin casts of each pair of antagonistic teeth were aligned with the help of interocclusal records. The casts were mounted in a jig, where a defined load could be applied. The ratio of applied force and measured sensor signal permitted a set of calibration factors. RESULTS: A correction factor for each pair of teeth helped determine the ratio by which measured occlusal force exceeded actual tooth load. Differences in occlusal morphology gave rise to a wide span of correction factors (1.01 to 2.80). Steep cusp angles resulted in a wedge action that gave rise to a strong increase in occlusal forces, which were about twice as high as actual tooth load, with wide variation. CONCLUSION: This method of bite force measurement eliminated the influence of occlusal morphology by individual correction for each pair of opposing teeth. To measure the absolute load of antagonistic teeth with thin film transducer foils, one must take into account individual occlusal morphology. Forces measured with the films are a function of both actual tooth load and occlusal morphology.
Bite Force↗
Maximal bite force and its associations with spinal posture and craniofacial morphology in young adults.
Maximal bite force (MBF) and its associations with craniofacial morphology and spinal posture were studied in a group of young adults (46 M and 38 F) aged 21 to 23 years. MBF was recorded in molar and incisal regions. Sagittal spinal posture was measured by spinal pantography and trunk asymmetry at thoracic and lumbar levels by a forward-bending test. Craniofacial variables and posture of the cervical spine were examined from lateral cephalograms taken in a natural head position. No statistically significant correlations existed between MBF and spinal posture, but significant correlations did exist between MBF and craniofacial variables, especially in women.
Adult↗
Bite force and oral function in patients with osseointegrated oral implants.
The function of the masticatory system was analyzed in 19 patients (13 women and 6 men), aged 39 to 68, randomly selected from a group of 165 patients who had been treated with osseointegrated oral implants within the last 7 years (average 3.5 years). The patients were well satisfied with the functional capacity of their implant reconstructions, especially compared with the poor function before treatment. According to the clinical examination, all but one patient had no or only mild symptoms of dysfunction of the masticatory system. Three bite-force levels were recorded. The mean value for gentle biting was 15.7 N, for biting as when chewing 50.1 N, AND FOR MAXIMAL BITING 144.4 N. The patients could thus well discriminate between the different bite-force levels, and the maximal values are much higher than those in persons with removable dentures.
Adult↗
Bite forces in patients after treatment of mandibular angle fractures with miniplate osteosynthesis according to Champy.
Maximal biting forces were evaluated in 22 patients with mandibular angle fractures treated with miniplate osteosynthesis according to Champy. An electric test procedure for evaluating the load resistance between the incisors, canines and molars was carried out 1 to 6 weeks following the treatment and additionally in 15 controls, too. This revealed that after surgical fracture treatment 1 week postoperatively only 31%, of the maximal vertical loading found in controls was registered. These values increased to 58% at the 6th week postoperatively.
Adolescent↗
Task-dependence of activity/ bite-force relations and its impact on estimation of chewing force from EMG.
Estimation of chewing force from electromyograms (EMGs) calibrated in isometric biting yielded strikingly high force values. We tested the hypothesis that EMG-based force predictions are excessive because of differing activity/bite-force relations in mastication and isometric biting. In nine patients, unilateral bite forces and EMGs of 4 elevator muscles were recorded during chewing and isometric clenching on a bite-fork. We estimated chewing force by substituting chewing EMGs of each muscle into isometric activity/bite-force regressions. The estimates were compared with actual chewing forces recorded by intra-oral transducers. In all muscles except the balancing-side masseter, the activity/bite-force ratio was significantly higher in chewing than in isometric biting. The actual mean chewing force amounted to 220 N, while EMG-based estimates ranged from 273 to 475 N, depending on the muscle used for estimation. The results indicate that different activity/force characteristics in dynamic and isometric biting can cause overestimation when chewing force is predicted from masticatory EMGs.
Algorithms↗
Maximum bite force after the replacement of complete dentures.
OBJECTIVE: The aim of the present study was to investigate whether the maximum bite force (MBF) can be improved by the replacement of complete dentures for elderly people. DESIGN: Nine edentulous volunteers, mean age 74.2 (+/- 5.5) years and average denture experience 19.4 +/- 19.5 years (1 to 50 years) had replacement dentures made. After a rehearsal session, MBF was recorded with the old dentures, and with the new dentures immediately at insertion, at 3, 8 days, 2-3 weeks, 1, 2, 3 and 6-10 months post insertion (p-i.). MBF was recorded with the central bearing point method using a full-bridge strain gauge load cell. Data were analysed off-line using the mean of two peak readings per patient per session. RESULTS: The results indicate that MBF tended to be impaired when replacement dentures were first fitted (n.s.). However, this trend reversed during the first month p-i. for patients with a "moderate" lower ridge resorption of Atwood grade 3 or 4 (n = 5). Patients with more severe lower ridge resorption Atwood grade 5 or 6 (n = 4) showed a significantly lower MBF over the entire observation period (p < or = 0.05) and took longer to regain bite strength. Only patients with moderate bone resorption exceeded their pre-insertion level of MBF within the observation period of 6-10 months p-i. CONCLUSION: The present pilot study suggests that, at least for elderly patients with severe bone resorption, delayed improvement of MBF should be expected with replacement complete dentures.
Age Factors↗
Effect of sample thickness on bite force studied with a multiple-point sheet sensor.
The aim of this study was to investigate the relationship between thickness of sample food and bite force. We designed a new sensor that can detect the pressure distribution between the incisor and molar teeth on one side, and the contact area between the food samples and the teeth. The force and contact area were directly measured in real time using the multiple-point sheet sensor, which is a very thin and flexible pressure-sensing device. Silicone rubber blocks were used as a sample food and were chewed with incisors and molars by 10 healthy women. The peak force, contact area, duration and impulse were greater between the incisors for a thicker specimen. The active pressure, defined as the ratio of the force to contact area, at peak was similar for different thicknesses. In contrast, with a 2 mm thick sample, the peak force and force related parameters were greatest in molar chewing. The force, contact area and duration were greater for molar chewing cycles than incisor ones. We verified that the thickness of samples influenced the chewing force of humans and the effects differed between incisors and molars.
Adult↗
A preliminary study of maximum voluntary bite force and jaw muscle efficiency in pre-orthognathic surgery patients.
The functional state of dentofacial deformity patients before orthognathic surgery has received relatively little study. In this study, the ability to generate occlusal force was compared between 84 patients before treatment for various dentofacial deformities and 57 controls. Maximal and submaximal bite forces were measured at the incisor and right and left first molar bite positions. Electromyographic activity (EMG) was recorded bilaterally from the anterior temporalis, posterior temporalis, and masseter muscles during each bite. An efficiency ratio was calculated for the jaw muscles by dividing the level of EMG by the occlusal force. There was a reduced ability to generate occlusal forces in the patients before surgery, especially among female patients. The reductions in maximal occlusal force were correlated with reduced efficiency of the jaw muscles.
Adult↗
Changes in bite force and chewing efficiency after denture treatment in edentulous patients with denture adaptation difficulties.
Masticatory function was studied by means of a chewing efficiency test and bite forces measurements in forty-nine edentulous patients who had applied for treatment with fixed protheses on osseointegrated dental implants. Registrations were performed with the original complete dentures and after treatment aiming at optimizing the dentures. The patients were divided into two groups and the post-treatment recordings were completed after adaptation periods of 2 and 6 months, respectively. The functional tests showed mainly small and non-significant changes after the denture treatment. Improvement was greater, however, in those with the poorest pre-treatment values. Chewing efficiency deteriorated after treatment in the older patients (more than 50 years) while it did not change in the younger ones. A longer adaptation period did not lead to better functional results. The findings are discussed in relation to the fact that the patients were waiting for implant treatment, with consequent psychological implications for interpretation.
Adaptation, Physiological↗
Bite force and masseter muscle electromyographic activity during onset of an isometric clench in man.
The surface electromyogram (EMG) of the masseter muscle and interocclusal force were recorded in six human subjects during fast and slow clenches. The simple linear force/EMG relation that applies for steady bite-force levels was inadequate to explain their relationship under conditions of changing force: a second component of force, its rate of change, was necessary. EMG/force equations for fast and slow clenches were broadly similar. The rate of change factor may account for the apparent EMG/force lag observed in earlier studies.
Adult↗
The effect of an interocclusal appliance on bite force and masseter electromyography in asymptomatic subjects and patients with temporomandibular pain and dysfunction.
The aims of this study were to assess the effect of clenching with or without the presence of an interocclusal appliance (IOA) on bite force (BF) and masseter electromyography (EMG) in patients with temporomandibular pain dysfunction disorders (TMPD) and to compare these results with an asymptomatic age- and gender-matched control group. Ten patients with TMPD (mean age 26.9 years) were compared with eight healthy controls (mean age 25.3 years). Bilateral masseter EMG activity was recorded at rest, while clenching on the BF meter, while clenching on an IOA and while clenching on an IOA together with the BF meter. Significant left to right EMG activity asymmetry was found in the patient group at rest and during multiple clenching tasks in the control group. The patient group had significantly greater EMG activity at rest than controls. For all other tasks, the control group EMG activity was greater than the patient group. Use of an IOA significantly decreased EMG activity in both patient and control groups. BF was significantly greater in the control group on the right side for the different clenching tasks. Insertion of the IOA significantly increased BF in the control group. The results of this study indicate differences in EMG activity and BF during different clenching tasks and between patients with TMPD and asymptomatic subjects.
Adult↗
The effect of a new denture adhesive on bite force until denture dislodgement.
PURPOSE: Denture adhesives are used to improve the denture retention and comfort of complete denture wearers. The purpose of this investigation was to establish the effect of a new denture adhesive on maximum bite force until denture dislodgement (BFDD) after adhesive application. MATERIALS AND METHODS: Fifteen denture-wearing patients (7 female, 8 male, mean age: 64 years) were involved in the study. The BFDD measurements were performed using a disposable gnathometer with a 1 to 10 scale. During one of the treatment sessions, the maximum BFDD with the pre-existing maxillary dentures using denture adhesive were measured. The measurements were also made at the baseline without adhesive and after the 1st, 2nd, 4th, and 6th hours following the application of the denture adhesive. The same procedure was applied to the new dentures about 2 weeks after the delivery of the dentures. The data were collected and statistically analyzed using ANOVA and Student's t-test. RESULTS: Consistent improvement was observed in BFDD when adhesive was used for all time intervals from the baseline (mean: 1.54 units, 3.20 units) to 6 hours (mean: 3.99 units, 4.60 units) for both pre-existing dentures (p= 0.003) and new dentures (p= 0.05), respectively. CONCLUSIONS: The results of this in vivo study suggest that the denture adhesive tested could effectively increase BFDD for up to 6 hours after application.
Adhesives↗
Bite force and occlusal load in healthy young subjects--a methodological study.
This study compares a new technique (Dental Prescale System) using pressure-sensitive foils for recording of maximal jaw closing force with a conventional clinical measurement using a miniature force transducer in 17 students. For assessment of load distribution the "pressure" image was superimposed on digitiZed images of dental casts and compared with clinical registrations of tooth contact. The bite force recorded with foil was systematically higher than that recorded by conventional measurements. Further more teeth were assessed as being loaded than having clinical occlusal contact. The new technique seems promising, although time consuming.
Adult↗
Relationship between myoelectric activity in masticatory muscles and bite force.
Myoelectric activity in the anterior and posterior temporalis and in the masseter muscle was assessed in five subjects biting unilaterally on a bite fork at 50, 100 and 200 N for 60 s. The bite fork was placed between the right first premolars and the first molars. The ipsilateral muscle activity was recorded first, and the contralateral side was evaluated 1 wk later. The relationship between exerted force and EMG-activity was expressed as ratios between EMG-activity and related bite force. EMG-activity increased with increasing force for all muscles tested. Linearity was found for the anterior temporal muscle, but not for the other muscles. Four of the subjects participated in an endurance test, exerting maximum bite force on the right side for as long as possible. The EMG activity of the right masseter muscle was closely related to bite force, in contrast to the other tested muscles. The activity of the left muscles increased at the end of the endurance test.
Adult↗
Discomfort and bite force in painful masseter muscles after intramuscular injections of local anesthetic and saline solution.
Thirty women with a history of daily pain in the masseter muscles were injected with either lidocaine or saline. The participants were told that they were being given an anesthetic injection to reduce their muscular discomfort. The dentist performing the injections did not know which fluid was used. The discomfort in the masseter muscle was assessed by using Borg's new rating scale before and 10 minutes after injection. The evaluation was followed up on day 1, day 3, and day 7. Bite force was registered between the first molars on the injection side. When scale values were compared individually within groups before and after injection, a significant decrease in discomfort was found in both groups, with the exception of day 1 for the lidocaine group and days 1 and 3 in the saline group. The total lidocaine and saline groups assessed the discomfort similarly except on day 3 when the lidocaine group showed significantly less discomfort. The intraindividual force values increased significantly after injection in the saline group. This effect was not found in the lidocaine group. Despite the minor tendencies for lidocaine to have a better effect, the placebo effect was considered to be high and important.
Adolescent↗
Masseter and temporalis muscle EMG levels and bite force in migraineurs.
The purpose of this study was to compare absolute and proportional electromyography (EMG) levels in the masseter and temporalis muscles during performance of a variety of oral functions for migraineurs and age- and sex-matched controls. Both groups consisted of nine women and one man, with a mean age of 43 years (range, 29 to 51 years). Absolute resting EMG levels and those levels during swallowing and speech were not significantly different between the groups, but the levels of the group with migraine were significantly higher during maximum voluntary effort contractions on the anterior teeth and on the posterior teeth for both muscles. When expressed as a percentage of those levels obtained at maximal posterior contraction (ie, proportional levels), no difference in functional activity was demonstrated between groups. It was concluded that the two groups studied had similar levels of EMG activity in the masseter and temporalis muscles during the normal oral functions investigated, but that the group with migraine had higher levels of absolute EMG activity during anterior and posterior maximum voluntary contractions. Furthermore, the group with migraine demonstrated higher levels of anterior and posterior bite force, although not correlated with EMG levels.
Adult↗