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PubMed2004

Denture wearing and strong bite force reduce pressure pain threshold of edentulous oral mucosa.

Pain in denture supporting tissue is one of the most common and critical problems affecting function and treatment outcomes in complete denture prosthetics. The objective of this study was to investigate the effects of denture wearing and bite force on the pressure pain threshold (PPT) of edentulous oral mucosa. PPT was measured in denture and non-denture-wearing patients by using an electronic-controlled pressure algometer. Bite force was measured in denture-wearing patients by using a pressure-detecting sheet. The mid palate showed 200-300% higher PPT than the buccal alveolar mucosa (two-way anova, P < 0.0001). Denture-wearing patients exhibited 40% lower palatal PPT than non-denture-wearing patients. In denture-wearing patients, PPT in the selected areas of the oral mucosa was negatively correlated with bite force. Denture wearing may reduce PPT in selected areas of the edentulous oral mucosa, and the PPT reduction may be associated with mechanical stress on the mucosa generated by bite force.

Adult↗
PubMed1979

Relation between integrated electromyographic activity and biting force during voluntary isometric contraction in human masticatory muscles.

The relation between integrated electromyographic activity and computed biting force during voluntary isometric contraction was evaluated in the masticatory muscles of healthy subjects. The slopes of the curves relating integrated electromyographic activity to computed biting force in masseter muscles were steeper on the non-preferred chewing side than on the preferred chewing side, and they progressively became steeper during the course of continuous isometric contraction of a given biting force.

Action Potentials↗
PubMed1996

Features of human jaw design which maximize the bite force.

A linear programming model, operating in a three-dimensional coordinate system, was written to study the effect on unilateral maximum bite forces (MBFs) of small changes in the design of human jaws. Under some conditions the MBF was larger on a more anterior tooth than a more posterior tooth for a given bite direction. The MBF was increased (i) as the bite force was tilted forward, (ii) as the jaw was opened if its direction was kept perpendicular to the occlusal plane of the lower jaw, (iii) by placing teeth nearer the midline, (iv) by raising the height of the teeth for forward bite forces, and (v) by tilting forward the articular surface of the condyle (equivalent to creating an articular eminence). Increasing the distance between the condyles spread the load more evenly between the two joints. The articular eminence was the only design feature which seemed to be clearly related to increasing the MBF.

Bite Force↗
PubMed1997

Contribution of the digastric muscles to the control of bite force in man.

The contribution of the (co-contracting) digastric muscles to the rapid decline in bite-force magnitude after unloading of a static bite was investigated by asking participants to perform two different biting tasks with sudden unloading, and correlating the degree of co-contraction of the digastrics (as derived from their electromyograms) with the impact force, the impact velocity (as measured after a travel distance of 5 mm), and the residual force when the jaw system was in static conditions again after the impact. Co-contraction of the digastrics was varied by asking participants to perform the biting task while controlling bite force (force-controlled experiments) or jaw position (position-controlled experiments). In half of the experiments, participants co-contracted their digastrics more strongly in the position-controlled than the force-controlled experiments. However, there was no clear relation between the level of co-contraction and the magnitude of the impact force, the impact velocity and the residual force. The results imply that co-contraction of the digastric muscles is not sufficient to explain the reduction in bite force and the low impact velocity after an unexpected jaw-closing movement. Two other possible mechanisms that reduce forces in an unloaded jaw system are: (1) force velocity properties of the activated jaw muscles in conjunction with creep of the aponeurotic sheets of the jaw muscles, resulting in a slow partial recovery of the biting force after impact: (2) force length properties of jaw-opening muscles, an activity not recorded here.

Bite Force↗
PubMed1988

Endurance tests of the masticatory system on different bite force levels.

Endurance tests of the masticatory system were performed in three different groups of healthy volunteers in order to investigate the relation between bite force and endurance time on different force levels. The subjects clenched a bite fork until exhaustion. Some tests were performed with and others without visual feedback of the exerted force. It was found that the subjects could sustain the maximal bite force practically at the same level during the recording time with visual feedback. The exerted force varied during the non-feedback recordings and generally decreased on the forceful levels. The average endurance time increased at lower bite force levels and the relation between force and endurance time is described. The average integrated time-force areas did not differ between the test levels. It is concluded that endurance tests in the clinic may be performed on submaximal bite force levels.

Adult↗
PubMed1995

Bite force and temporomandibular disorder in juvenile chronic arthritis.

The aim of this study was to investigate the functional condition of the stomatognathic system in children suffering from juvenile chronic arthritis, with respect to bite force and temporomandibular disorder in relation to radiographic abnormalities of the mandibular condyle, occlusal factors and systemic disease parameters. Thirty-five children with juvenile chronic arthritis were compared to 89 healthy children with an Angle Class I occlusion and 62 children with an Angle Class II malocclusion. Subjective symptoms and clinical signs of temporomandibular disorder and radiographic mandibular condylar changes were more common in children with juvenile chronic arthritis than in the two comparison groups. Maximal molar and incisal bite forces and maximal molar bite force endurance times were also significantly reduced in children with juvenile chronic arthritis. It is concluded that the differences between the groups are caused mainly by the systemic inflammatory disease itself, but a functional influence of weakened masticatory muscles cannot be excluded.

Adolescent↗
PubMed2007

Bite force and maxillofacial morphology in patients with Duchenne-type muscular dystrophy.

PURPOSE: The purpose of this study is to evaluate maxillofacial morphology and bite force in patients with severe Duchenne-type myodystrophy. PATIENTS AND METHODS: The subjects included 24 men (average age, 21.5 years; range, 17 to 30 years) with Duchenne-type muscular dystrophy receiving treatment in National Ioh Hospital. Lateral and axial cephalograms were used to assess the morphology in this study. The maximum bite force on the first molar and the maximum mouth opening distance were measured. RESULTS: The anterior open bite was visualized in most patients on the lateral cephalogram. The upper and lower arch lengths in the patients were significantly smaller than those in the controls (P < .05). In contrast, the upper and lower arch widths in the patients were significantly larger than those in the controls (P < .05). The maximum bite force and maximum mouth opening distance in the patients were significantly lower than those in the controls (P < .05). CONCLUSION: These results appear to be very useful for improving the care and treatment of patients with Duchenne-type muscular dystrophy.

Adolescent↗
PubMed2006

A novel approach to bite force measurements in a porcine model in vivo.

A novel device for a bite force measurement system in a porcine model is described. A single polyethylene layer was vacuum-formed into a splint, and a force sensor was fitted on to the splint occlusal surface and seated with a silicone layer. This design enabled the measurement of bite forces on selected teeth in a large animal model with either natural dentition or single implant crowns and could be used in assessing information on biomechanical adaptation of the bone-implant interface to masticatory loads. Preliminary recordings of force values obtained during mastication in the premolar region (200-560 N) and various limiting factors of the technical design are discussed.

Animals↗
PubMed1990

Coactivation of jaw muscles: recruitment order and level as a function of bite force direction and magnitude.

The aim of this study was to obtain insight into the coactivation behaviour of the jaw muscles under various a priori defined static loading conditions of the mandible. As the masticatory system is mechanically redundant, an infinite number of recruitment patterns is theoretically possible to produce a certain bite force. Using a three-component force transducer and a feedback method, subjects could be instructed to produce a bite force of specific direction and magnitude under simultaneous registration of the EMG activity of anterior and posterior temporal, masseter and digastric muscles on each side. Forces were measured at the second premolars. Vertical, anterior, posterior, lateral and medial force directions were examined; in each direction force levels between 50 N and maximal voluntary force were produced. The results show that for all muscles the bite force-EMG relationship obeys a straight-line fit for forces exceeding 50 N. The relationship varies with bite force direction, except in the case of the digastric muscles. Variation is small for the anterior temporal and large for the posterior temporal and masseter muscles. The relative activation of muscles for a particular force in a particular direction in unique, despite the redundancy.

Adult↗
PubMed2002

A new approach to evaluating occlusal support by analyzing the center of the bite force.

The aim of this study was to create a standard for occlusal support in the diagnosis and evaluation of prosthetic treatment. In experimental occlusion, the maximal bite force of eight normal dentates was measured by pressure-sensitive film over the whole dentition using splints divided into nine pieces. The occlusal contact was altered by exchanging splint pieces according to the shortened dental arch concept. The occlusal load center (OLC) was located on a graph set up with reference to the size of the individual dental arch. The occlusal supporting index (SI) and the rehabilitation index (RI) were calculated from the locations of the OLC corresponding to each occlusal contact. Differences in numbers and distribution of occlusal stops could clearly be distinguished by the location of the OLC. Though the SI showed a strong positive correlation with maximal bite force, it is proposed that the number of occlusal stops, or occlusal units, provides the most effective index for quantitative parameters of occlusal support in clinical use. From the standpoint of bite force, analysis of the RI is suggested as a useful method of objectively evaluating the recovery of occlusal support with prosthetic treatment.

Adult↗
PubMed1995

The effects of orthodontic treatment on isometric bite forces and mandibular motion in patients before orthognathic surgery.

PURPOSE: Little is known about the effects of orthodontic treatment on oral motor function. The objective of this report is to evaluate changes in mandibular motion and maximum bite force that occur between the initiation of presurgical orthodontics and its completion before surgery. PATIENTS AND METHODS: Fifteen patients (9 women, 6 men) with a variety of dentofacial deformities were examined before and after presurgical orthodontics. Mechanical advantage of the muscles and bite points, mandibular range of motion, maximum isometric bite force, and levels of electromyographic (EMG) activity in the anterior and posterior temporalis and masseter muscles during isometric bites were recorded on all subjects over time. Data obtained before and after completion of presurgical orthodontics were statistically compared. RESULTS: Presurgical orthodontics reduced mandibular mobility somewhat, but the amount was not significant. Statistically significant reductions in bite force were noted after orthodontics for incisor, canine, premolar, and molar bite positions. No significant difference in the EMG/bite force slopes was obtained, nor was there any difference in the moment arms of the bite points or the muscles of mastication from orthodontics. CONCLUSIONS: This study showed significant changes in measures of oral motor function resulting from orthodontic treatment. A larger study is needed to confirm that these results will be similar in all orthodontic patients. There is no indication that these changes are the result of physiologic alterations of the muscles of mastication. The best current explanation is that these changes result from the pain and discomfort of the orthodontic appliances and the induced malocclusion.

Adolescent↗
PubMed1984

Human discrimination of different bite forces.

Twenty young adult subjects were selected to determine normal baseline data of dynamic interdental bite force discrimination by use of a specially designed strain gauge instrument. The data may aid in defining the role of the periodontal ligament, temporomandibular joint and muscles of mastication in the regulation of interincisor bite force.

Adult↗
PubMed1990

A preliminary electromyographic study of bite force and jaw-closing muscle fatigue in human subjects with advanced tooth wear.

The maximum bite force was recorded in five experimental volunteers with advanced tooth wear and five control volunteers who showed no abnormal wear. All subjects were then asked to maintain a force of 50% of the maximum for as long as possible while surface electromyograms from the masseter and temporalis muscles were recorded. The bite force and endurance time were found to be slightly increased in the experimental group, but no conclusions could be drawn regarding the state of fatigue. Two significant problems with regard to fatigue studies of the jaw-closing muscles emerged from the study, namely the use of the canine position for recording of the force, and the thickness of the force meter.

Adult↗
PubMed1975

Activity of temporal and masseter muscles in children with a lateral forced bite.

The activity of the temporal and masseter muscles with the mandible in postural position and during chewing, maximal bite in the intercuspal position, and swallowing were recorded electromyographically in nineteen children with laterally forced bite. Of the children, aged 8-12 years, sixteen had unilateral crossbite. In all of the individuals there was lateral deviation between the retruded contact position and the intercuspal position. The magnitude of the lateral deviation was measured with a modified gnathothesiometer. The muscle activity was recorded bilaterally from the temporal muscle and from the masseter muscle. In the postural position asymmetric activity was found in the temporal muscle suggesting that the mandible in postural position was still displaced to the side of forced bite. During chewing the activity was asymmetric both in the anterior and the posterior temporal portions. This asymmetric muscle activity was interpreted as an adaptation to avoid cuspal interferences. Also in maximal bite the muscle activity was asymmetric, while the activity during swallowing was affected less than in the other functions. The swallowing activity was, however, less in children with a forced bite than in children with normal occlusion.

Child↗
PubMed2001

[Expression of type I collagen mRNA in rat molar periodontal ligament under normal bite force].

OBJECTIVE: The main component of the periodontal ligament(PDL) is collagen fiber, especially type I collagen, and collagen plays an important role in PDL. The aim of this study is to observe the expression of rat PDL mRNA under normal bite force and to investigate the molecular mechanisms of these changes in type I collagen mRNA. METHODS: 40 male Wistar rats were used, and animals were intra-cardiac perfused with a solution of 4% polyformaldehyde under anesthesia. Dissected mandibles were immersed in the same fixation for 6 hours and subsequently decalcified in EDTA. The demineralized specimens were embedded in paraffin and cut into slices with thickness 5 microns. The probe was synthesized and labeled with digoxigenin. Expression of type I collagen mRNA was measured by using in situ hybridization(ISH). RESULTS: Under the normal bite force, the mRNA expression of type I collagen was very strong on the whole, including the alveolar bone side, the root side and the area between them. Positive signals were located mainly in the cytoplasm and some in the nuclei. But the mRNA expression of type I collagen still had spatial characteristics. The signals in some fibroblasts were apparently stronger than those in other fibroblasts in the apical 1/3 fragment of the roots. The signal of type I collagen mRNA was strong near the root sides. The expression signal on the proximal alveolar walls was strong, however, on the distal alveolar wall, there was no expression. CONCLUSION: The expression of type I collagen mRNA is closely related with bite force.

Animals↗
PubMed2000

[Effect of lost bite force on the expression of bFGF in rat molar periodontal ligament].

OBJECTIVE: To observe the dynamic change of the expression of basic fibroblast growth factor (bFGF) in rat molar periodontal ligament(PDL), combined with other experiments to probe into the relation of the expression between bFGF and type I collagen mRNA. METHODS: Animal model was established by extracting the left maxillary molars. Immunohistochemistry was applied. RESULTS: The expression of bFGF obviously increased from the first day to the second week (P < 0.05), Came back to that of normal bite force group at the third week. There were strong negative relative relationship between the expression of bFGF and that of type I collagen mRNA. CONCLUSION: The expression of bFGF increased under lost bite force in rat molar PDL. The effect of bite force on the expression of PDL type I collagen mRNA is closely related to the expression of bFGF.

Animals↗
PubMedDate not supplied

Bruxism and voluntary maximal bite force in young dentate adults.

PURPOSE: Bruxism may increase the activity and volume of the masticatory muscles, yet its resulting effect on bite force is controversial. This study evaluated the relationship between voluntary maximal bite force (MBF) and presence of bruxism in 80 dentate young adults (40 men, 40 women, 20 to 38 years old), controlling for sex, body mass index (BMI), and presence of orofacial muscular pain during the MBF measurement. MATERIALS AND METHODS: MBF was measured with a compressive load transducer at the first molar region. Information about the presence of bruxism was collected by means of self-report of centric or eccentric bruxism during the day or night and/or presence of tooth wear. Data on MBF were analyzed by analysis of covariance, with bruxism and sex as fixed factors, and BMI and orofacial muscular pain as covariates (.05 level of significance). RESULTS: The mean +/- standard deviation values of MBF were 859 +/- 304 N for nonbruxers (n = 49) and 806 +/- 282 N for bruxers (n = 31), with no significant difference between groups (P = .842). BMI was not a significant covariate for MBF (P = .237), and neither was the presence of orofacial muscular pain (P = .560). Sex was statistically significant for MBF (P < .001), and men (1,009 +/- 290 N) had higher MBF than women (668 +/- 179), but there was no interaction between sex and bruxism in relation to the MBF (P = .861). CONCLUSION: These results suggest that bruxers and nonbruxers did not have different voluntary MBF in this sample of young dentate adults.

Adult↗