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At least 109 records · Page 6Linked to original sources
PubMed2000

[Effects of bite force lost on the expression of IL-6 in the rat periodontium].

OBJECTIVE: In order to explain the molecular mechanism of periodontium remodeling the expression of IL-6 in the rat periodontal ligament fibroblasts (PDLC) and the alveolar bone osteoblasts under normal and bite force lost was studied. METHODS: To establish a rat model of different bite force for the study, left maxillary molars of rats were extracted and the left mandibular molar area was used as the bite force lost. The animals were sacrificed after 6 hours, 1, 2, 3 days and 1, 2, 3, 4 weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of IL-6 protein in PDLC and osteoblasts with HE staining and immunohistochemistry techniques. RESULTS: In the group of bite force lost, the loosely arrangement of periodontal ligaments and the resorption of alveolar bone were observed in histological study, the expression of IL-6 in PDLC and osteoblasts was enhanced apparently than that in the group of normal bite force by using immunohistochemistry techniques. In the group of lost bite force, the expression of IL-6 in PDLC enhanced with time regularly: The expression of IL-6 was strengthened after 3 days, and reached the peak after 2 weeks, then, decreased after that and restored to normality in 4 weeks. While in osteoblasts of the group of bite force lost, the expression of IL-6 was strengthened just after 2 weeks. CONCLUSION: Bite force lost induce the expression of IL-6 enhanced apparently in PDLC and osteoblasts, it suggests that IL-6 may play important roles in the effect of bite force on periodontium remodeling. It approaches initially the molecular mechanism of periodontium remodeling, demonstrates that the histologic morphology is closely related to the mechanical condition.

Alveolar Bone Loss↗
PubMed1994

Bite force on single as opposed to all maxillary front teeth.

The relation of number of teeth to maximal clenching force was tested in 10 healthy female dental students. The maximal force in the interincisal position was tested by spreading the load with individual acrylic splints over a varying number of teeth in the anterior region. In the maxilla, one splint covered teeth 13-23; another covered tooth 11. In the mandible, one splint covered teeth 33-43 in all experiments. The maximal force in the incisal position was measured 10 times, five times with each splint. The maxillary splints were changed in random order. The tactile sensibility of tooth 11 and its antagonists was tested before and immediately after interincisal force measurements. A highly significant difference between maximal forces was seen in comparing biting between a single tooth and multiple teeth. In addition, bite force also showed a significant increase in both single tooth and multiple teeth successive biting trials during the experiments. Tactile sensibility between d 11 and its antagonist was not altered by the maximal bite force trials.

Acrylic Resins↗
PubMed2005

[Effect of bite force lost on the expression of iNOS in the rat periodontium].

PURPOSE: To investigate the molecular mechanism of the effect of bite force loss on periodontium remodeling. METHODS: For establishing a rat model of different bite forces for the study, the left maxillary molars of Wistar rats were extracted and the left mandibular molar area was used as the model of the bite force lost. The animals were sacrificed after 6 hours,1,2,3 days and 1,2,3,4weeks. The prepared tissue specimens were processed for the study of the change in the histologic morphology and the expression of iNOS protein in PDLC and osteoblasts with HE staining, immunohistochemistry and RT-PCR techniques, and the results were analyzed by one-way ANOVA,Dunnet t test and paired samples test. RESULTS: In the group of lost biting force, the derangement of periodontal ligament and resorption of alveolar bone were observed in histologic study: the structure of periodontal ligament deranged ,fibers and cells arrayed abnormally, there were many holes in the alveolar bone, even osteoclasts were present; the expression of iNOS was observed dramatically changed: the expression of iNOS in periodontal ligament fibroblasts and osteoblasts was higher than normal, especially at 2 days and 3 weeks,so as the results of RT-PCR.There was a significant correlation between bite force lost and the increased expression of iNOSmRNA. CONCLUSIONS: Bite force lost significantly increased the expression of iNOSmRNA in PDLC and osteoblasts, which suggests that iNOS may play an important role in the process of periodontium remodeling.

Alveolar Bone Loss↗
PubMed1989

Proportionality of mean voltage of masseter muscle to maximum bite force applied for diagnosing temporomandibular joint disturbance syndrome.

Maximum bite force in the region of the right first maxillary molar and the corresponding mean voltage of the right masseter muscle of 29 patients suffering from temporomandibular joint dysfunction and 27 healthy controls were measured. In contrast with the controls, the maximum bite force of the patients was smaller (p less than 0.01), the mean voltage was nearly equal (p greater than 0.05), and the proportionality of the mean voltage to the maximum bite force of the patients was greater (p less than 0.01). These results tend to indicate that the masticatory muscles of patients with temporomandibular joint dysfunction are in a state of hyperactivity and tension. The proportionality method suggested in this article is more convenient and easier to apply than previously proposed methods that measure the slope of voltage/tension curves. It may, therefore, have clinical value in the diagnosis of patients with temporomandibular joint disorders.

Adolescent↗
PubMed1994

Bite forces in patients treated for mandibular angle fractures: implications for fixation recommendations.

Voluntary bite forces were recorded at varying periods in 35 males treated with rigid internal fixation for fractures of the mandibular angle. Bite forces were also obtained in 29 male controls for comparison. It was found that molar bite forces in patients were significantly less than in controls for several weeks after surgery. Further, molar bite forces on the side of the fracture were significantly less than on the nonfractured side. The results of this study indicate that recommendations for the amount of fixation required for a given fracture may be reduced.

Adolescent↗
PubMed1989

[A study on mandibular displacement due to biting force. 2. Analysis of condylar displacement].

Part of the biting force is believed to be transmitted to the temporomandibular joint and cause interarticular pressure. This pressure's degree and function, however, are not clarified. In this paper, I shall examine this pressure from condylar movement measured by the face-bow. For the measurement of condylar movement caused by biting-pressure, I used an intraoral appliance which consisted of a pair of Co-Cr clutches and a pivot. While the patient exerted both maximum and medium biting force on the pivot located at the first molar, mandibular movements were measured. Both sides of the condyle tended to move anterosuperiorly. Condylar movement averaged 0.29 mm on the working side, and 0.46 mm on the balancing side during maximum bite force. Distance and direction of the condylar movements were equal to the results of previous investigations, excepting the direction of working side condyle. The difference was considered to be primarily due to experimental variables. The condylar movement during biting was smaller than that during pushing the jaw upward with manual forces. This suggests that interarticular pressure is only slight on both sides during first molar bite action.

Bite Force↗
PubMed1990

Jaw muscle activity in relation to the direction and point of application of bite force.

This study examined the way the masseter and the anterior and posterior temporal muscles of human subjects were activated when a bite force of constant magnitude was exerted at different teeth in different defined directions. Subjects were instructed to produce a bite force of a particular magnitude (250 N) and direction (vertical, anterior, lateral, posterior, or medial) using a three-component force transducer and a feedback method. Simultaneously, the EMG activity of the muscles was registered with use of surface electrodes. Unilateral bite forces were produced at the right canine, second premolar, and second molar. In addition, a bilateral vertical premolar bite was examined for comparison of activity levels of the muscles of both sides. The results showed that, on average, the activities of the right and left side muscles did not differ in a bilateral vertical bite. Moreover, in a unilateral vertical bite, there were no significant right-left differences. For all bite force directions, more muscle activity was required for production of a constant bite force at the anterior side of the dental arch than at the posterior side. An exception to this rule was the activity of the posterior temporal muscle in a posteriorly directed bite. There was a close relationship between the direction of bite force and jaw muscle activity. Variations in activity were small for the anterior temporal muscle and large for the posterior temporal and masseter muscles. All muscles that were studied were always active, even in directions in which they could be expected to act antagonistically.

Adult↗
PubMed1986

Electromyography and bite force studies of muscular function and dysfunction in masticatory muscles.

Electromyographic (EMG) activity versus bite force was studied during a gradually increased isometric contraction up to maximal effort for patients with painful masseter muscles and referents. The masseter muscle, the anterior temporal muscle and the descending part of the trapezius muscle were chosen for the recordings. Bite force was registered with a bite force sensor placed between the first molars. The effects of double blind intramuscular injections of lidocaine and saline in the patients' masseter muscle were evaluated by EMG versus bite force and by assessment of discomfort. EMG activity during unilateral chewing was compared in terms of relative masticatory force between referents and patients by amplitude probability distribution analysis. Regression analyses showed intra-individually steeper slopes for high force levels than for low force levels for the masseter muscle. This was not observed for the anterior temporal muscle. These differences in slopes of the EMG versus force regressions for the masseter muscle and the anterior temporal muscle could be due to differences in recruitment pattern. The same intra-individual relationship between low and high force levels was found for referents and patients. An increased activity, especially among the patients, was found for the descending part of the trapezius muscle during stronger activity of the mandibular elevators. The EMG versus force relationship for low force levels of the masseter muscle was less steep after an intramuscular injection of lidocaine but not after saline. Both solutions for injection had a positive effect on the patients' assessments of discomfort one week after the injection. Three days after injection the patients who received lidocaine experienced a reduction in muscular discomfort. This reduction was not found among patients receiving saline. The amplitude probability distribution analysis revealed that the patients used greater relative masticatory forces than the referents during the chewing of an almond for all probability levels analysed below the peak load of the masseter muscles. Rough estimates of the peak masticatory forces in Newton (N) were for chewing an almond 364 N (referents); 373 N (patients) and for gum-chewing 239 N (referents); 238 N (patients) as regards the masseter muscle. The values were similar for the anterior temporal muscle.

Bite Force↗
PubMed2006

Seed husking time and maximal bite force in finches.

Many studies on the efficiency of feeding in finches concentrate on husking time in relation to average seed size and bird size. Large species are capable of eating larger seeds and are able to husk large seeds faster than smaller species. It is generally assumed that husking time is related to bite force. However, there are very few studies that investigate the relationship between husking time, seed hardness and bite force directly. In our experiments we measured the seed husking time and the maximal bite force of two taxa of seed cracking birds. Husking time is related to maximal bite force in a highly non-linear way and differs between estrildids and fringillids. Fringillids with the same bite force as estrildids take less time to crack seeds, but only when the strength of the seed coat is close to their maximal bite force. For seeds that are relatively soft the difference in husking time becomes very small. A preliminary jaw motion analysis provides evidence that this difference in husking time between estrildids and fringillids is paralleled by a difference in husking technique. This difference in technique does not affect bite force as such, but decreases the chance of failed cracking attempts. The selective advantage of a small increase in maximal bite force may be related more to the decrease in husking time for seeds with hardness below the maximal bite force, than to the increase in range of seed hardness that the bird is able to crack.

Animals↗
PubMed2005

The effect of maximum bite force on marginal bone loss in mandibular overdenture treatment: an in vivo study.

The impact of bite force on the marginal bone response around implants is a subject of debate. This study focused on the effect of maximum bite force on marginal bone levels in mandibular implant overdenture treatment. In addition, the effect of the sequence of 3 different loading conditions on marginal bone loss was evaluated in vivo. The patient population consisted of a group of 18 patients. They received 2 implants in the mandible and a new denture without attachments during the period of submerged implant healing. After second stage surgery, the denture was provided with a ball, magnet or bar-clip attachment. There was a transition of attachment type after 3 and 6 months of function. The sequence in which the attachments were used was randomised. Radiographic marginal bone loss was measured after the period of submerged implant healing and after 3, 6 and 9 months of functional implant loading. Maximum bite force measurements were obtained just prior to second stage surgery with the new denture without attachment. Bite force measurements were also obtained after 3, 6 and 9 months of loading with the implant-retained overdenture. The latter 3 values were averaged. The mean bone loss during the period of submerged healing and during functional loading was 1.7 mm (0.7 mm) and 1.3 mm (0.6 mm), respectively. A relationship between maximum bite force during the period of submerged healing or during the period of functional loading on the one hand and the amount of marginal bone loss on the other could not be demonstrated. The sequence in which the different attachment types were used did not influence the observed amount of marginal bone loss.

Adolescent↗
PubMed1982

A novel miniature bite force recorder and its clinical application.

Solid state components were used to construct a miniature bite force recorder suitable for registrations in large study groups. A semiconductor was chosen as the sensory unit. The complete recording system included a power supply, the bite force recorder, a chart recorder and a millivoltmeter. Laboratory calibration tests were performed to screen the limitations of the recorder. Series of loads were applied in the range from 10 to 1000 N. Eight females and eight males, 20 to 25 years old, were asked to produce a succession of maximum bites at three second intervals for as long as possible. The bite force recorder was positioned between the first molars on the left side. The laboratory tests showed that loads in the range from 10 to 1000 N were recorded with an error less than four percent. In the clinical tests, the mean maximal bite force was 500 N ranging from 330 to 680 N. The number of maximum bites varied from 5 to 27. No statistically significant differences were observed between the sexes as regards the maximal bite force and the number of bites.

Adult↗
PubMed2003

Correlation between maximum bite force and craniofacial morphology of young adults in Indonesia.

The present study was conducted to evaluate the relationship between maximum bite force and craniofacial morphology. Sixty-four Indonesian female dental students aged 19-27 years with normal occlusion served as the subjects. The Dental Prescale System was used to measure the maximum bite force using a pressure sensitive sheets while craniofacial morphology measurements were determined from conventional lateral radiograms. The antero-posterior and right-left position of the occlusal load centre (the OLC) were measured also. Stepwise multiple regression analysis was performed to evaluate the relationship between bite force and craniofacial morphology while correlation analysis was used to evaluate the antero-posterior position of the OLC related to craniofacial morphology. Fifty-five per cent of the bite force could be explained by variations in the posterior facial height, gonial angle, antero-posterior size of the maxilla, and posterior length of the cranial base. The result showed a larger bite force implies a greater posterior facial height, smaller gonial angle, larger maxilla and straighter posterior length of the cranial base. This study suggests that among Indonesians, maximum bite force could be explained by craniofacial morphology as found in Caucasians. In addition, we proposed a clinical standard of the OLC for the comprehensive evaluation of occlusion.

Adult↗
PubMed1995

Maximal bite force and its association with signs and symptoms of craniomandibular disorders in young Finnish non-patients.

Maximal bite force values and subjective symptoms and clinical signs of craniomandibular disorders (CMD) were recorded for a non-patient sample of 129 young adults, 56 men and 73 women. The signs and symptoms of CMD were classified on the basis of Helkimo's clinical dysfunction index. The two genders reported equally frequently subjective symptoms of CMD, but women had significantly more severe clinical signs of CMD than did men. Mean maximal bite force values for men were 909 N (SD, 177) in the molar region and 382 N (SD, 133) in the incisal region and thus significantly higher than corresponding figures for women, 777 N (SD, 168) in the molar, 325 N (SD, 116) in the incisal region, suggesting that separate evaluation of the genders would be advisable in future studies involving bite force assessments. Neither subjective symptoms nor clinical signs of CMD correlated significantly with maximal bite force values. The bite force values measured were in line with theoretical calculations.

Adult↗
PubMed1993

The effects of dental condition on hand strength and maximum bite force.

Piezoelectric force transducer and hand dynamometer were used for measuring the maximum bite force and hand grasp force on 2034 primary, middle, and high school students. Dental condition and body weight and height were also observed to relate to the force measurements. It was discovered that both forces increased relative to the increase of age, body weight, and body height. Boys had stronger bite force than girls at all age groups, while the grasp force of boys became significantly stronger only after the age of 13. Students who had dentition with decay and missing teeth tended to have weaker bite force, while hand force was not influenced. Bite force does not seem parallel to hand strength and is, instead, related to dental condition.

Adolescent↗
PubMed1988

Bite force after temporomandibular joint surgery.

Bitings were recorded bilaterally on 5 different submaximal and maximal force levels on 12 patients (7 women and 5 men) who had earlier been subjected to TMJ surgery (10 diskectomies and 2 condylectomies). The maximal bite force was relatively low for the recorded sample with mean values of 7.8 Kp and 8.3 Kp for operated and non-operated sides, respectively. The strongest forces were recorded after condylectomy. There was a wide range between the individual recordings on all levels and the differences increased with the force and were largest at maximal bite force level. No significant differences in bite force between operated and non-operated sides could be found for any of the force levels. The ability to discriminate between different force levels was better on the higher levels. The almost comparable results of the recordings of bite force on the operated and the non-operated sides may be an effect of functional interaction within the masticatory system and be an expression of the essentially improved function after the surgical treatment.

Adult↗
PubMed1989

Human bite force discrimination using specific maxillary and mandibular teeth.

The purpose of this study was to determine whether performance differences existed in subjects' self-generated bite force discrimination ability using maxillary and mandibular central incisors, canines, premolars and first molars. Two separate studies were conducted: (i) to assess whether performance differences existed in subjects' bite force discrimination ability using central incisors and premolars; (ii) to compare subjects' performance on bite force discrimination using central incisors, canines and first molars. Assessment of bite force was measured using a specially designed strain gauge scale allowing subjects to visually monitor when their biting force equalled a preset resistance. Resistance forces of 500, 1000 and 3000 g were selected as standards. Subjects were presented with a series of paired resistance settings, one at a time, the first of each pair being the standard and the second being the comparator setting of a predetermined amount. This paired-comparisons procedure was continued until the subjects' difference limen (DL) value (the threshold of discrimination between two forces) could be established. The first study revealed no significant (P greater than 0.05) overall difference in subjects' bite force discrimination ability relative to specific teeth. In contrast, in the second study a significant difference (P less than 0.05) was identified in subjects' performance relative to specific teeth; subjects' performed better using central incisors compared to first molars. In both studies, subjects' performance was significantly better (P less than 0.05) using the 500 g standard compared to the 3000 g standard in the first study, and compared to the 1000 g standard in the second study. No significant differences (P greater than 0.05) were observed between the performance of males and females in either study.

Adult↗
PubMed1991

A biomechanical analysis of craniofacial form and bite force.

In vivo measurements of bite force and bone strain obtained in growing African green monkeys were used to study skull biology and geometry. Strain values and distributional patterns seen in association with forceful jaw elevation were inconsistent with most conventional explanations that link upper facial morphology with masticatory function and use beam models of craniofacial architecture. The results mandate careful use of concepts about skeletal geometry based on static analysis that have not been experimentally verified with in vivo procedures. In particular, a reevaluation of conventional ideas about the generation and dissipation of forces during contraction of the jaw elevator muscles seems called for.

Animals↗
PubMed2004

Comparative analysis of methods for determining bite force in the spiny dogfish Squalus acanthias.

Many studies have identified relationships between the forces generated by the cranial musculature during feeding and cranial design. Particularly important to understanding the diversity of cranial form amongst vertebrates is knowledge of the generated magnitudes of bite force because of its use as a measure of ecological performance. In order to determine an accurate morphological proxy for bite force in elasmobranchs, theoretical force generation by the quadratomandibularis muscle of the spiny dogfish Squalus acanthias was modeled using a variety of morphological techniques, and lever-ratio analyses were used to determine resultant bite forces. These measures were compared to in vivo bite force measurements obtained with a pressure transducer during tetanic stimulation experiments of the quadratomandibularis. Although no differences were found between the theoretical and in vivo bite forces measured, modeling analyses indicate that the quadratomandibularis muscle should be divided into its constituent divisions and digital images of the cross-sections of these divisions should be used to estimate cross-sectional area when calculating theoretical force production. From all analyses the maximum bite force measured was 19.57 N. This relatively low magnitude of bite force is discussed with respect to the ecomorphology of the feeding mechanism of S. acanthias to demonstrate the interdependence of morphology, ecology, and behavior in organismal design.

Analysis of Variance↗