The performance and the characteristics of various sensors are analyzed to meet the requirement of measuring the bone force-electromechanical potentials. The strain sensor that is suitable small signal and bone force-electromechanical potential measure is developed and the curved structural form of the strain sensor is chosen. The strain sensor has the advantage of small volume, large linear range, convenient installation and high sensitivity. The relationship between the strain and force-electromechanical potential of bone specimen is determined in the experiment on the bone of femur and bone of teeth using this type of sensor which provides the valuable data for clinical use.
Biomechanical Phenomena ; Biosensing Techniques ; Electrophysiology ; Equipment Design ; Femur ; physiology ; Humans ; Mandible ; physiology ; Maxilla ; physiology ; Osteogenesis ; physiology

Defects were created in the mandible of a rabbit model whereby the right side was implanted with hydroxyapatite (HA) while the left side was left empty to act as control. Both the implant and control sites were evaluated clinically and histologically at 4,12,20,22 weeks. Decalcified sections were studied under confocal laser scanning microscope. No reactive cells were evident microscopically in all sections. There was bone ingrowth as early as 4 weeks when viewed by the topographic method. Enhancement of osteoconduction was evident by the presence of abundant capillaries, perivascular tissue and osteoprogenitor cells of the host. At 22 weeks, the implanted defect showed mature bone formation filling almost the whole field. This study demonstrated that the dense HA exhibits excellent biocompatibility as noted by the complete absence of reactive cells. It also promotes osteoconduction.
*Bone Substitutes ; *Hydroxyapatites ; Mandible/pathology ; Mandible/*surgery ; *Materials Testing ; Osseointegration/physiology

OBJECTIVETo investigate the regulation of stress distribution on TMJ when the location of occlusal load on the mandibular second molar was changed by using the 3-dimensional Finite Element Method (FEM).

METHODSA 3-dimensional FEM TMJ model including left mandibular second molar and mandible was established. In finite element analysis software ANSYS the same boundary constraints were applied to the TMJ FEM model with different load cases. The occlusal loads were applied to simulate ICO load, distal load, and buccal load and the stress values of condyles of the FEM model were calculated.

RESULTSAs the occlusal load was applied to different tooth contact areas with various shapes, the stress distributions of bilateral condyles were found different and asymmetrical. The condyle stress on TMJ FEM model in three loading cases was diverse, not only in stress character but also in stress distribution style. The maximum value of Von Mises in the opposite condyle was 51.513 MPa when ICO load was applied. But when the distal load or the buccal load was applied, the maximum value of Von Mises in the opposite condyle increased to 72.145 MPa or 69.566 Mpa respectively.

CONCLUSIONSThe same level but in different direction of occlusal load that resulted from difference of loading spots by changing the occlusal contact area, would induce different stress features on bilateral condyles.

Bite Force ; Dental Stress Analysis ; Finite Element Analysis ; Humans ; Mandible ; physiology ; Molar ; physiology ; Temporomandibular Joint ; physiology

OBJECTIVETo explore the six degrees of freedom of jaw opening and closing movement with motion capture and analysis system to establish a quantitative method for studying mandibular movement and a digital basis for virtual reality study of mandibular movement.

METHODSIn a male adult with normal dentition without temporomandibular joint disorders, 3 fluorescent markers were pasted in the upper dentition and 4 in the lower dentition. Six cameras of the motion capture system were arranged in a semi-circular fashion. The subject sat in front of the camera at an 80-cm distance with the Frankfort plane kept parallel to the horizontal plane. The degree-of-freedom (3 linear displacement and 3 angular displacement) of jaw opening and closing movement was obtained by collecting the marker motion.

RESULTSSix degrees of freedom of jaw opening and closing were obtained using the motion capture system. The maximum linear displacements of X, Y and Z axes were 5.888 089 cm, 0.782 269 cm, and 0.138 931 cm, and the minimum linear displacements were -3.649 83 cm, -35.961 2 cm, -5.818 63 cm, respectively. The maximum angular displacements of X, Y and Z axes were 0.760 088°, 2.803 753°, and 0.786 493°, with the minimum angular displacements of -2.526 18°, -0.625 94°, and -25.429 8°, respectively. Variations of linear displacements during jaw opening and closing occurred mainly in the Y axis, and those of angular displacement occurred mainly in the Z axis.

CONCLUSIONThe six degree-of-freedom of mandibular movement can be accurately obtained with the motion capture system to allow quantitative examination of the mandibular movement.

Adult ; Humans ; Male ; Mandible ; physiology ; Movement ; physiology ; Range of Motion, Articular ; Temporomandibular Joint ; physiology ; Video Recording

Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.
Humans ; Mastication/physiology* ; Temporomandibular Joint/physiology* ; Temporomandibular Joint Disorders/etiology* ; Mandible/physiology*

Four types of 3D mathematical mode of the muscle groups applied to the human mandible have been developed. One is based on electromyography (EMG) and the others are based on linear programming with different objective function. Each model contains 26 muscle forces and two joint forces, allowing simulation of static bite forces and concomitant joint reaction forces for various bite point locations and mandibular positions. In this paper, the method of image processing to measure the position and direction of muscle forces according to 3D CAD model was built with CT data. Matlab optimization toolbox is applied to solve the three modes based on linear programming. Results show that the model with an objective function requiring a minimum sum of the tensions in the muscles is reasonable and agrees very well with the normal physiology activity.
Bite Force ; Computer Simulation ; Electromyography ; Humans ; Mandible ; physiology ; Programming, Linear

OBJECTIVETo investigate the activities of head, neck and upper trunk muscles with mandibular movement in normal adults.

METHODSThe integral data of surface electromyography (EMG) had been recorded to analyze the activities of anterior temporal (Ta), posterior temporal (Tp), sternocleidomastoid (SCM) and trapezius (TRAP) muscles with mandibular movement in ten normal adults.

RESULTSThe former mentioned muscles acted constantly when the mandible was in the rest position. The activities of Ta, Tp and SCM muscles increased with protrusion of mandible, mouth opening, tapping, maximum clenching, and chewing movements. The amplitudes of the increased activity of these muscles were correlated significantly with each other. When the activities of Ta and Tp muscles increased to 56 times and 25 times respectively, the activity of SCM muscle increased to 5 - 6 times. The activity of trapezius muscle increased with protrusion of mandible and opening movement, but tended to stop with the maximum clenching and chewing movement. The correlations of left and right sides of the same muscles had been found.

CONCLUSIONSThe muscles of head, neck and upper trunk can act as contributors to keep the mandibular positions and take part in the mandibular movements.

Adult ; Electromyography ; Female ; Head Movements ; physiology ; Humans ; Male ; Mandible ; physiology ; Mastication ; physiology ; Movement ; Muscle, Skeletal ; physiology ; Neck Muscles ; physiology ; Range of Motion, Articular ; Shoulder ; physiology ; Temporomandibular Joint ; physiology

OBJECTIVETo look for the way of three-dimensional simulation of the craniofacial system.

METHODSA three-dimensional laser scanner was used for gypsum models digitization and computed tomography scans was employed for skull reconstruction, then the data of teeth and temporomandibular joint were picked up and integrated. The ARCUS sigma system was used to record spatial mandibular movements. The data of both digital reconstruction and spatial movements were transferred into one coordinate system. The software for three-dimensional simulation was programmed.

RESULTSThe preliminary program could be used to analyze static and dynamic occlusion and gnathic relations, to check the contact points and to show from various visual angles and slices. The occlusal plane, curves, and helical axis were initially defined and displayed.

CONCLUSIONSUsing available instruments and methods, we developed the primary edition for three-dimensional simulation of the craniofacial system. However, it is far from a mature system and there is still plenty of work to be done.

Dental Occlusion ; Humans ; Imaging, Three-Dimensional ; Mandible ; physiology ; Models, Anatomic ; Skull ; Temporomandibular Joint ; physiology ; Tooth

gp130-mediated signaling is involved in both chondrogenesis and osteogenesis, but its direct role in the formation of embryonic Meckel's cartilage and associated mandibular development has not yet been elucidated. In this study, we examined the influence of gp130 ablation on the developing mandibular Meckel's cartilage by evaluating the morphological and histological changes as well as the gene expression patterns in developing embryonic gp130-/- mice. The ablation of the gp130 gene showed no change in region-specific collagen mRNA expression except for a slight delay in its expression but caused shortened embryonic Meckel's cartilage, delayed hypertrophic chondrocyte maturation and subsequent bony replacement with characteristic bending of the intramandibular Meckel's cartilage. The bending of Meckel's cartilage led to a narrow mandibular arch at the rostral area with poor cortical plate formation. These findings indicate that gp130-mediated signaling is important for the normal morphogenesis of Meckel's cartilage and subsequent mandibular development.
Animals ; Body Patterning ; Cartilage/embryology/metabolism/*physiology ; Collagen ; Cytokine Receptor gp130/genetics/*physiology ; Mandible/embryology/metabolism/*physiology ; Mice ; Mice, Knockout

OBJECTIVETo study the effect of nerve growth factor (NGF) and Schwann cells on axon regeneration of the inferior alveolar nerve following mandibular lengthening with distraction osteogenesis.

METHODSUnilateral mandibular osteodistraction was performed in 9 healthy adult male goats with a distraction rate of 1 mm/d. Every 3 goats were killed on days 7, 14 and 28 after mandibular lengthening, respectively. The inferior alveolar nerves in the distraction callus were harvested and processed for ultrastructural and NGF immunohistochemical study. The inferior alveolar nerves from the contralateral side were used as controls.

RESULTSOn day 7 after distraction, axon degeneration and Schwann cell proliferation were observed, and very strong staining of NGF in the distracted nerve was detected. On day 14 after distraction, axon regeneration and remyelination were easily observed, and NGF expression started to decline. On day 28 after distraction, the gray scale of NGF immunoreactivity recovered to the normal value and the Schwann cells almost recovered to their normal state.

CONCLUSIONSGradual mandibular osteodistraction can result in mild or moderate axon degeneration of the inferior alveolar nerve. Nerve trauma may stimulate the proliferation of Schwann cells and promote the synthesis and secretion of NGF in the Schwann cells. Schwann cells and NGF might play important roles in axon regeneration of the injured inferior alveolar nerve following mandibular lengthening.

Animals ; Axons ; pathology ; physiology ; Goats ; Immunohistochemistry ; Male ; Mandible ; surgery ; Mandibular Nerve ; physiology ; Nerve Growth Factor ; physiology ; Nerve Regeneration ; physiology ; Osteogenesis, Distraction ; Schwann Cells ; physiology