Impact of Bone Volume Upon Condylar Activity in Patients With Unilateral Condylar Hyperplasia.

Purpose: Unilateral condylar hyperplasia or hyperactivity (UCH) is a bone overgrowth disorder affecting the mandible. The purpose of this study was to determine the relations among age, condylar bone structure, condylar bone volume, and condylar bone activity on single-photon emission computed tomographic (SPECT) scans in patients with UCH.

Materials And Methods: This study included 20 patients with a clinical presentation of progressive mandibular asymmetry and a positive bone SPECT scan.

Effects of Decreased Occlusal Loading during Growth on the Mandibular Bone Characteristics.

Background: Bone mass and mineralization are largely influenced by loading. The purpose of this study was to evaluate the reaction of the entire mandibular bone in response to decreased load during growth. It is hypothesized that decreased muscular loading will lead to bone changes as seen during disuse, i.

Implications of high-dosage bisphosphonate treatment on bone tissue in the jaw and knee joint.

Bisphosphonates are bone antiresorptive agents traditionally used on a relatively large scale for treatment of bone metabolic diseases and on a smaller scale for bone metastasis treatment. A study on the effects of bisphosphonate treatment on healthy instead of diseased animals will give more insight into the basic mechanisms of bisphosphonates and their effects on different bone sites. We aimed to assess the effect of BP on the mouse knee and jaw joint.

Higher number of pentosidine cross-links induced by ribose does not alter tissue stiffness of cancellous bone.

The role of mature collagen cross-links, pentosidine (Pen) cross-links in particular, in the micromechanical properties of cancellous bone is unknown. The aim of this study was to examine nonenzymatic glycation effects on tissue stiffness of demineralized and non-demineralized cancellous bone. A total of 60 bone samples were derived from mandibular condyles of six pigs, and assigned to either control or experimental groups.

The microstructural and biomechanical development of the condylar bone: a review.

Background: Bone constantly strives for optimal architecture. Mandibular condyle, which is subjected to various mechanical loads forcing it to be highly adaptive, has a unique structure and a relatively high remodelling rate. Despite the eminent clinical relevance of mandibular condyle, literature on its structural and biomechanical development and on the mechanical role of its mineralized and non-mineralized bone components is scarce.

Condylar process contributes to mandibular asymmetry: In vivo 3D MRI study.

The purpose of this study was to investigate the differences in mandibular morphology between the deviated and nondeviated sides in patients with noncongenital skeletal mandibular asymmetry. Divergences from control values were assessed to determine which region of the mandible contributes most to mandibular asymmetry. We measured various dimensions of the mandible in 20 young patients and 20 controls using noninvasive high-quality three-dimensional (3D) volumetric magnetic resonance imaging.

A histomorphometric and micro-computed tomography study of bone regeneration in the maxillary sinus comparing biphasic calcium phosphate and deproteinized cancellous bovine bone in a human split-mouth model.

Objective: The gain of mineralized bone was compared between deproteinized bovine bone allograft (DBA) and biphasic calcium phosphate (BCP) for dental implant placement.

Study Design: Five patients with atrophic maxillae underwent bilateral sinus elevation with DBA (Bio-Oss) and BCP (Straumann BoneCeramic). After 3 to 8 months, 32 Camlog implants were placed, and biopsies were retrieved.

Osteoclast precursors in murine bone marrow express CD27 and are impeded in osteoclast development by CD70 on activated immune cells.

Osteoclasts (OCs) are bone-resorbing cells that are formed from hematopoietic precursors. OCs ordinarily maintain bone homeostasis, but they can also cause major pathology in autoimmune and inflammatory diseases. Under homeostatic conditions, receptor activator of nuclear factor kappa-B (RANK) ligand on osteoblasts drives OC differentiation by interaction with its receptor RANK on OC precursors.

The correlation between mineralization degree and bone tissue stiffness in the porcine mandibular condyle.

The aim of this study was to correlate the local tissue mineral density (TMD) with the bone tissue stiffness. It was hypothesized that these variables are positively correlated. Cancellous and cortical bone samples were derived from ten mandibular condyles taken from 5 young and 5 adult female pigs.

Influence of botulinum toxin on rabbit jaw muscle activity and anatomy.

Introduction: Muscles can adapt their fiber properties to accommodate to new conditions. We investigated the extent to which a decrease in muscle activation can cause an adaptation of fiber properties in synergistic and antagonistic jaw muscles.

Methods: Three months after the injection of botulinum toxin type A in one masseter (anterior or posterior) muscle changes in fiber type composition and fiber cross-sectional areas in jaw muscles were studied at the microscopic level.

Dissociation of bone resorption and bone formation in adult mice with a non-functional V-ATPase in osteoclasts leads to increased bone strength.

Osteopetrosis caused by defective acid secretion by the osteoclast, is characterized by defective bone resorption, increased osteoclast numbers, while bone formation is normal or increased. In contrast the bones are of poor quality, despite this uncoupling of formation from resorption.To shed light on the effect of uncoupling in adult mice with respect to bone strength, we transplanted irradiated three-month old normal mice with hematopoietic stem cells from control or oc/oc mice, which have defective acid secretion, and followed them for 12 to 28 weeks.

The physiology and ontogeny of daily oral behaviors.

In the masticatory system, activities of muscles are the main source of force. The daily activity of the jaw muscle is a measure of the total daily loading of the tissues involved. This article gives an overview on the recent assessments of the physiology and ontogeny of the daily use of the jaw muscles.

Determination of the relationship between collagen cross-links and the bone-tissue stiffness in the porcine mandibular condyle.

Although bone-tissue stiffness is closely related to the degree to which bone has been mineralized, other determinants are yet to be identified. We, therefore, examined the extent to which the mineralization degree, collagen, and its cross-links are related to bone-tissue stiffness. A total of 50 cancellous and cortical bone samples were derived from the right mandibular condyles of five young and five adult female pigs.

The masticatory system under varying functional load. Part 1: Structural adaptation of rabbit jaw muscles to reduced masticatory load.

Skeletal muscle fibres can change their myosin heavy-chain (MyHC) isoform and cross-sectional area, which determine their contraction velocity and maximum force generation, respectively, to adapt to varying functional loads. In general, reduced muscle activity induces transition towards faster fibres and a decrease in fibre cross-sectional area. In order to investigate the effect of a reduction in masticatory load on three functionally different jaw muscles, the MyHC composition and the corresponding cross-sectional area of fibres were determined in the superficial masseter, superficial temporalis, and digastric muscles of male juvenile New Zealand White rabbits that had been raised on a soft diet (n=8) from 8 to 20 weeks of age and in those of normal diet controls (n=8).

The masticatory system under varying functional load. Part 2: Effect of reduced masticatory load on the degree and distribution of mineralization in the rabbit mandible.

A reduction in mechanical loading of the mandible brought about by mastication of soft food is assumed to decrease the remodelling rate of bone, which, in turn, might increase the degree of bone mineralization. The effect of a reduction in masticatory functional load on the degree and distribution of mineralization of mandibular bone was investigated in male juvenile New Zealand White rabbits. The experimental animals (n=8) had been raised on a diet of soft pellets from 8 to 20 weeks of age, while the controls (n=8) had been fed pellets of normal hardness.

Degree of mineralization at the attachment of lateral pterygoid.

The degree of mineralization of bone (DMB) in the human mandibular condyle is heterogeneous, and differences in DMB have been related to variations in bone turnover caused by local strains. The lateral pterygoid muscle inserts at the anterior surface of the condyle. The aim of this study is to analyze the DMB at the attachment of this muscle as compared with a control region.

Adaptation of rat jaw muscle fibers in postnatal development with a different food consistency: an immunohistochemical and electromyographic study.

The development of the craniofacial system occurs, among other reasons, as a response to functional needs. In particular, the deficiency of the proper masticatory stimulus affects the growth. The purpose of this study was to relate alterations of muscle activity during postnatal development to adaptational changes in the muscle fibers.

Nonablative neonatal bone marrow transplantation rapidly reverses severe murine osteopetrosis despite low-level engraftment and lack of selective expansion of the osteoclastic lineage.

Infantile malignant osteopetrosis (IMO) is caused by lack of functional osteoclasts leading to skeletal abnormalities, blindness owing to compression of the optic nerves, bone marrow (BM) failure, and early death. In most patients, TCIRG1, a proton pump subunit essential for bone resorption, is mutated. oc/oc mice represent a model for IMO owing to a deletion in Tcirg1 and die around 4 weeks of age.

Age-related changes in collagen properties and mineralization in cancellous and cortical bone in the porcine mandibular condyle.

Collagen is an important constituent of bone, and it has been suggested that changes in collagen and mineral properties of bone are interrelated during growth. The aim of this study was to quantify age-related changes in collagen properties and the degree of mineralization of bone (DMB). The DMB in cancellous and cortical bone samples from the mandibular condyle of 35 female pigs aged 0-100 weeks was determined using micro-computed tomography.

Functional characteristics of the rat jaw muscles: daily muscle activity and fiber type composition.

Skeletal muscles have a heterogeneous fiber type composition, which reflects their functional demand. The daily muscle use and the percentage of slow-type fibers have been shown to be positively correlated in skeletal muscles of larger animals but for smaller animals there is no information. The examination of this relationship in adult rats was the purpose of this study.

Inhibitory regulation of osteoclast bone resorption by signal regulatory protein alpha.

Osteoclasts mediate bone resorption, which is critical for bone development, maintenance, and repair. Proper control of osteoclast development and function is important and deregulation of these processes may lead to bone disease, such as osteoporosis. Previous studies have shown that the cytosolic protein tyrosine phosphatase SHP-1 acts as a suppressor of osteoclast differentiation and function, but putative inhibitory receptors that mediate recruitment and activation of SHP-1 in osteoclasts have remained unknown.

The adaptive response of jaw muscles to varying functional demands.

Jaw muscles are versatile entities that are able to adapt their anatomical characteristics, such as size, cross-sectional area, and fibre properties, to altered functional demands. The dynamic nature of muscle fibres allows them to change their phenotype to optimize the required contractile function while minimizing energy use. Changes in these anatomical parameters are associated with changes in neuromuscular activity as the pattern of muscle activation by the central nervous system plays an important role in the modulation of muscle properties.

Effects of increased occlusal vertical dimension on daily activity and myosin heavy chain composition in rat jaw muscle.

Mammalian skeletal muscles change their contractile-protein phenotype in response to mechanical loading and/or chronic electrical stimulation, implying that the phenotypic changes in masticatory muscles might result from new masticatory-loading conditions. To analyze the effects of increased occlusal vertical dimension (OVD) on daily activities and fibre-type compositions in jaw muscles, we measured the total duration of daily activity (duty time) and the myosin heavy chain (MyHC) compositions in the masseter and digastric muscles of freely moving control and bite-opened rats. In the control state, the duty time of the digastric muscle was higher than that of the masseter muscle at activity levels exceeding 5 and 20% of the day's peak activity.

From movement to models: a tribute to professor Alan G. Hannam.

This tribute article to Professor Alan G. Hannam is based on 7 presentations for him at the July 1, 2008 symposium honoring 3 "giants" in orofacial neuroscience: Professors B. J.

Jaw-muscle activity changes after the induction of osteoarthrosis in the temporomandibular joint by mechanical loading.

Aims: To examine the effect of mechanical loading on the induction of temporomandibular joint osteoarthrosis (TMJ OA).

Methods: Mechanical stress was applied to the rat TMJ by forced jaw opening of 3 hours a day for 5 days. The electromyographic (EMG) activity of the masseter and digastric muscles was continuously monitored by radio-telemetry.