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Tissue-separating capacity of growth cartilages.

The tissue-separating capacity of chondral structures has been debated for more than 30 years, and one aspect that has particularly been questioned is whether the secondary cartilage of the mandibular condyle is comparable to primary growth cartilage, e.g. the epiphyseal growth plate. The present report summarizes information gained by using a specific interosseal transplantation method. These findings lead to the conclusion that all the structures examined, i.e. the proximal epiphyseal cartilage of the tibia, the cartilage of the costochondral junction of the ribs, the basicranial synchondroses, the medial cartilage of the clavicle and the mandibular condyle, have the capacity to separate adjoining skeletal structures. The changes induced by the transplanted structures in the recipient area vary, however, suggesting a hierarchial arrangement of cartilages with regard to their tissue-separating capacity. It is suggested that the tissue-separating capacity is a basic phenomenon in the function of growth, not only of primary growth cartilages, but of secondary cartilages as well.

Animals↗

Gadolinium-enhanced MR imaging of temporomandibular disorders: improved lesion detection of the posterior disk attachment on T1-weighted images obtained with fat suppression.

OBJECTIVE: The purpose of this study was to assess the potential for improved lesion detection in the posterior disk attachment and its surrounding tissue in temporomandibular disorders when gadolinium-enhanced MR imaging performed with fat suppression is used. MATERIALS AND METHODS: Forty-five patients underwent MR imaging with conventional T1- and T2-weighted, gadolinium-enhanced T1-weighted, and gadolinium-enhanced fat-suppressed spin-echo imaging sequences. Qualitative and quantitative assessments of the contrast enhancement of each type of imaging were also performed. RESULTS: The contrast-enhanced fat-suppressed T1-weighted imaging sequence had several advantages over the other imaging techniques in detecting abnormalities of the posterior disk attachment and in detecting bone marrow lesions in the mandibular condyle. The most significant advantage was better enhancement of lesion conspicuity. The diagnostic accuracy of contrast-enhanced fat-suppressed imaging was 77% versus 70% for conventional contrast-enhanced imaging. The kappa value for interobserver agreement was .95 for contrast-enhanced fat-suppressed imaging and .72 for conventional contrast-enhanced imaging. CONCLUSION: Contrast-enhanced fat-suppressed T1-weighted spin-echo MR imaging is a valuable technique for visualizing the extent and degree of lesions in the posterior disk attachment and bone marrow lesions in the mandibular condyle.

Adolescent↗

Mandibular forces during simulated tooth clenching.

Differential, functional loading of the mandibular condyles has been suggested by several human morphologic studies and by animal strain experiments. To describe articular loading and the simultaneous forces on the dental arch, static bites on a three-dimensional finite element model of the human mandible were simulated. Five clenching tasks were modeled: in the intercuspal position; during left lateral group effort; during left lateral group effort with balancing contact; during incisal clenching; and during right molar clenching. The model's predictions confirmed that the human mandibular condyles are load-bearing, with greater force magnitudes being transmitted bilaterally during intercuspal and incisal clenching, as well as through the balancing-side articulation during unilateral biting. Differential condylar loading depended on the clenching task. Whereas higher forces were found on the lateral and lateroposterior regions of the condyles during intercuspal clenching, the model predicted higher loads on the medial condylar regions during incisal clenching. The inclusion of a balancing-side occlusal contact seemed to decrease the forces on the balancing-side condyle. Whereas the predicted occlusal reaction forces confirmed the lever action of the mandible, the simulated force gradients along the tooth row suggest a complex bending behavior of the jaw.

Bite Force↗

[Tensile mechanics of mandibular condylar cartilage].

OBJECTIVE: To study the biomechanical properties of the mandibular condyle cartilage and determine its functional importance. METHODS: Eight condyle specimens of the four pig temporomandibular joints were obtained by autopsy and stored in sealed plastic bags at -20 degrees C. These pigs were healthy, aged 1 year +/- 2 months. In the coronal direction, 300 microns wide, rectangular cartilage-bone specimens were prepared on the right condyles using specified knife. In the sagittal direction, rectangular cartilage-bone specimens with the same width were obtained on the left condyles. Standard rectangular testing specimens were prepared from cartilage-bone specimens in a microtome kept at -20 degrees C (300 microns wide and 250 microns thick). The specimens were inserted in a soft-tissue uniaxial tensile test machine and immersed in a bath of Ringer's solution at room temperature. Preconditioning of the specimens was carried out prior to the uniaxial tensile experiment and the specimens were elongated to failure with the constant strain rate (0.05 mm/s). The resulting mean values were curved fitted with Fung's two-parameter (A, B) exponential stress strain equation using a nonlinear regression program. RESULTS: The data obtained showed that a typical nonlinear biomechanical behavior of the condyle cartilage. Toe-region and quasi-linear zone were obvious on the experimental stress strain relation curve. Theoretically fitted parameter A and B were 0.47 and 4.13 (coronally) and 0.60 and 4.70 (sagittally). The sagittal specimens showed greater tensile stress (2.92 MPa), tensile stiffness (9.04 MPa), energy absorption (6.02 N.mm) but less tensile strain (37.34%) than that of the coronal specimens (2.15 MPa, 6.55 MPa, 4.91 N.mm, and 41.12%). The differences were statistically significant (P < 0.05). CONCLUSION: The mandibular condyle cartilage is a kind of biophasic material which shows nonlinear viscoelastic behavior, anistrophic characteristics in biomechanical function and high ability to resist tensile stress in the longitudinal direction.

Animals↗

Functional subdivision of the human masseter and temporalis muscles as shown by the condylar movement response to electrical muscle stimulation.

In previous studies from our laboratory, a functional subdivision of the human temporalis and masseter muscles was demonstrated by means of opto-electronic recordings of the lower incisal point movement responses to electrical muscle stimulation. In the present study, it was examined whether this subdivision was also reflected in different movement responses of the mandibular condyle. To that end, the condylar movement responses to unilateral stimulation of four masseter muscle parts and three temporalis muscle parts were studied in four different jaw positions. The kinematic centre was used for condylar reference point. For both the amplitude and the direction of the movement responses, the effects of stimulation location and jaw position were studied using multivariate ANOVA and contrast analyses. It was found that for both outcome variables, the functional subdivision of the masseter and temporalis muscles was also reflected in some, but not all, of the movement responses of the mandibular condyles. The deep masseter muscle part and the (anterior) temporalis muscle part responded similarly to electrical stimulation.

Adult↗

[Image analysis of condylar cartilaginous adaptation to mandibular protrusion in rats].

OBJECTIVE: To quantify chondrogenesis in condylar cartilage in response to active forward positioning of mandible. METHODS: Identical bite-jumping appliances were fixed to upper incisors of animals in experimental groups, causing a continuous mandibular forward positioning. Histological sections were performed through mandibular condyle and were stained with HE under the same condition. Chondrogenesis was quantified by measuring the area of cells in resting, proliferative, hypertrophic and erosive zones in the superioposterior region, through computer-assisted image analyzing system (Q550IW, Leica) with the advanced software (Leica Qwin Pro, V2.2). Statistical analysis was performed with GraphPad 3.0. RESULTS: 1. comparison among experimental groups revealed a fluctuation in proliferative zone, with 21-day group being the greatest (0.058 +/- 0.004 mm2) and 14-day the least (0.012 +/- 0.001 mm2). A change in erosive zone was also depicted by a peak of 0.112 +/- 0.001 mm2 in 7-day group and a bottom of 0.018 +/- 0.002 mm2 in 14-day group (P < 0.001). 2. comparison among the control groups manifested stable zonation, except for a slump of proliferative zone descending from 0.069 +/- 0.005 mm2 in 3-day group to 0.009 +/- 0.001 mm2 in 21-day group (P < 0.001). 3. comparison between experimental and control groups demonstrated significant discrepancy in proliferative zone, hypertrophic zone and erosive zone (P < 0.001). CONCLUSION: Mandibular forward positioning stimulates and accelerates cartilaginous remodeling in mandibular condyle.

Animals↗

Mandibular growth and histologic changes in condylar cartilage of rats intoxicated with vitamin D3 or 1,25(OH)2D3 and pair-fed (undernourished) rats.

The mandibular condyles of 1,25(OH)2D3 or Vitamin D3 intoxicated rats were studied and compared with those of normal as well as pair-fed controls. Experimental animals were injected with either Vitamin D3 (2 mg/kg/day) or 1,25(OH)2D3 (400 ng/kg/day) for 19 days. Controls were given the solvent only, while pair-fed animals were restricted in their food intake for the same period of time, so that they exhibited a weight-curve similar to that of the experimental rats. The length of the mandibular ramus was measured in lateral radiographs of all mandibles. Demineralized coronal sections were obtained from all mandibular condyles and were stained with Mallory's connective tissue stain. The width of each zone within the condylar cartilage was measured. Experimental animals showed significant reduction in width of all layers within the condylar cartilage, with total lack of distinction between the maturation and hypertrophic zones. They also exhibited a significant retardation in growth of the mandible. Pair-fed animals had a normal width of the chondroprogenitor layer but significantly smaller maturation + hypertrophic zones (vs. controls). They also exhibited a significant retardation in mandibular growth but not to the same degree as did the intoxicated animals. Reduction in growth attributed to 1,25(OH)2D3 or Vitamin D3 intoxication is partly caused by undernutrition, which is a by-product of this condition. A further kinetic study is indicated to elucidate the mechanism of growth retardation and the differential effect on the various cartilage layers.

Animals↗

Articular chondrocytes lose their proliferative activity with aging yet can be restimulated by PTH-(1-84), PGE1, and dexamethasone.

Mouse mandibular condyles develop spontaneous degenerative changes by 6 months of age, hence providing a good in vivo model for studies related to processes associated with the onset and progression of age-related osteoarthritis. Further, this joint provides an appropriate system to investigate the potential of articular cartilage to respond to hormones and local growth factors in old age. The present study examined (1) the age-related changes in [3H]thymidine incorporation by articular chondrocytes in the mouse mandibular condyle, and (2) the effect of systemic and local factors upon the tissue's ability to resume DNA synthesis. Condyles of female CW-1 mice ranging from 3 to 18 months of age were cultured in the presence of PTH-(1-84) (2 micrograms/ml), PGE1 (20 micrograms/ml), dexamethasone (10(-7) M), and MSA (5 micrograms/ml) and were concomitantly labeled with [3H]thymidine. Autoradiographs were analyzed quantitatively and revealed (1) a significant (p less than 0.01) age-related decrease (-80%) in the labeling index of the articular cartilage, and (2) the ability of old tissues to resume DNA synthesis following in vitro treatment with PTH-(1-84), PGE1, and dexamethasone. Concomitant quantitative incorporation studies further substantiated the autoradiographic findings. Hence, these factors possess a direct stimulatory effect upon senescent chondrocytes involved in an advanced stage of spontaneous osteoarthritis.

Aging↗

Condylar adaptation after alteration of vertical dimension in adult rhesus monkeys, Macaca mulatta.

Remodeling in the cartilage of the mandibular condyle was investigated in young adult monkeys after an increase in vertical dimension of the midface through the use of a tooth-borne intraoral appliance. Six young adult male rhesus monkeys had bite-splints of 5 mm, 10 mm or 15 mm cemented to their maxillary dentition for 48 weeks. Five age- and sex-matched monkeys were used as controls. The thickness of the articular tissue and of the prechondroblastic and chondroblastic layers of the condylar cartilage in the superior, posterosuperior and posterior regions was measured from parasagittal sections of the temporomandibular joint (TMJ). It was found that articular tissue thickness was reduced in the superior region; the prechondroblastic layer, absent in control animals, was very distinctive (30-75 microns) in experimental animals; and there was a 62% increase in the thickness of the chondroblastic layer in the experimental animals. These findings indicate that chronic alteration of mandibular posture via increase in vertical dimension stimulates progressive remodeling of the mandibular condyle in young adult monkeys.

Adaptation, Physiological↗

The effects of positioning variations in transcranial radiographs of the temporomandibular joint: a laboratory study.

The relationship of the mandibular condyle to the articular fossa and eminence as seen on transcranial oblique lateral (TOL) radiographs of the temporomandibular joint is used by some clinicians as an important diagnostic sign and indicator of treatment. The literature is divided on the validity of this. The aim of this study was to consider the effects of variations in both the position of the joint and the X-ray beam orientation on the image seen on TOL radiographs. TOL radiography of a mounted block specimen of a human temporomandibular joint and associated tissues was carried out using a range of specimen rotations (+20 degrees to -20 degrees with respect to the sagittal plane) and X-ray beam angulations (20 degrees, 25 degrees, 30 degrees). Analysis of tracings of the joint images showed that most of the parameters measured varied by statistically significant amounts with changes in either specimen rotation or beam angulation. It is concluded that any convention which purports to evaluate the position of the mandibular condyle in relation to the articular fossa from TOL radiographs is invalid when the orientation of the condyle to coronal and horizontal planes is unknown.

Adult↗

The insulin-sensitive glucose transporter (GLUT4) is involved in early bone growth in control and diabetic mice, but is regulated through the insulin-like growth factor I receptor.

Children with uncontrolled type I (insulin-dependent) diabetes mellitus are characterized by a slow growth rate, which improves upon adequate therapy. While skeletal growth is an energy-consuming process involving high glucose utilization, the role of glucose transporters (GLUT) and their regulation in the bone formation process are not yet fully understood. Thus, we studied both in vivo and in vitro early endochondral bone formation in control and streptozotocin-induced young diabetic mice. Using in situ hybridization and immunohistochemistry techniques, we demonstrated the novel existence of the insulin-sensitive glucose transporter (GLUT4), as well as GLUT1, in juvenile-derived murine mandibular condyles and in the humeral growth plate-two models for endochondral bone formation. Insulin-like growth factor (IGF) I receptors (IGF-I-R), but not insulin receptors (IR), were shown to have cellular distribution similar to GLUT4, being more abundant in mature chondrocytes. Further, in the skeletal growth centers of streptozotocin-induced diabetic mice, GLUT4, IGF-I, and IGF-I and insulin receptor levels, but not GLUT1 were markedly reduced. The decrease in GLUT4 and in IGF-I and insulin receptors was associated with severe histological changes in the mandibular condyles and humeral growth plate. Insulin therapy restored IR levels to normalcy, whereas IGF-I-R and GLUT4 levels were only partially recovered. Thus, GLUT4 and IGF-I-R have a potential role in early bone growth in mice. Further, during early bone growth GLUT4 may be regulated through the IGF-I receptor rather than via the insulin receptor. We propose that skeletal growth retardation in type I diabetes may be associated with reduced expression of the GLUT4 and IGF-I receptor in the bone growth center.

Animals↗

Control of the condylar-proximal mandibular segments after sagittal split osteotomies to advance the mandible.

Maintenance of the normal or presurgical anatomic position of the mandibular condyles and contiguous proximal mandibular ramus segments after sagittal split ramus osteotomies is important, not only to enhance the stability of results but also to avoid iatrogenic temporomandibular joint complications. Accordingly, during the past few years, we have attempted to improve the surgical control of condyle and proximal segment position while using the sagittal split ramus osteotomy to advance the mandible. After several modifications, the device reported herein was used and the results evaluated in ten consecutive patients who underwent bilateral sagittal split ramus osteotomies with symmetric advancement of the mandible. This device enables the surgeon to obtain very precise reproduction of the "normal" proximal segment and condyle position at the time of surgery. The use of the device and documentation of its efficiency are presented.

Equipment Design↗

The expression of types X and VI collagen and fibrillin in rat mandibular condylar cartilage. Response to mastication forces.

Types X and VI collagen and fibrillin were localized by in situ hybridization and immunohistochemical methods in the mandibular condyles of rats, and the response of these molecules to post-weaning diets of soft food, ordinary pellets, or hardened pellets was studied. Type X collagen was synthesized, particularly in conditions of soft food consistency, by cells in the perichondrium-periosteum and in the bone and by cells at the erosion front between cartilage and bone. Type X collagen synthesis diminished under higher compression forces due to mastication and with increasing age. Type VI collagen and fibrillin were synthesized by cells in the perichondrium-periosteum and by chondrocytes and by stromal osteoblasts and were not modified by higher mechanical forces. In contrast to previous findings in the growth plate of long bones, type X collagen in the mandibular condyle was not synthesized by hypertrophic chondrocytes but was associated with cells of the osteoblastic rather than the chondroblastic phenotype.

Animals↗

Cbfa1 couples chondrocytes maturation and endochondral ossification in rat mandibular condylar cartilage.

Core binding factor a1 (Cbfa1) is a crucial transcription factor for osteoblasts differentiation and chondrocytes maturation in embryonic skeletal genesis, but little is known about its function in mandibular condylar growth. The aim of this study was to determine the temporal and spatial pattern of Cbfa1 expression in condylar cartilage during natural growth. Mandibular condyles were harvested from 50 female Sprague-Dawley rats at age of 38, 42, 49, 56 and 65 days. Alcian blue and PAS staining was used for histological analysis. Type A antibody raised against Cbfa1 isoform II was observed in the pre-hypertrophic and hypertrophic chondrocytes in condylar cartilage, and in the mature osteocytes in trabecular bone. Type B antibody raised against 17 aa sequence present after the Runt domain was detected in tartrate resistant acid phosphatase (TRAP) positive osteoclasts in the erosive front of cartilage, and also in the osteoblasts on the sub-chondral bone surface. In situ hybridisation was carried out with a probe containing a fragment in exon 8 of the cDNA. Cbfa1 transcripts were localised in the osteoblasts and chondrocytes, but not in osteoclasts. Quantitative analysis demonstrated that both types of Cbfa1 proteins reached their maximum level on day 56, which coincided with the terminal maturation of hypertrophic chondrocytes and the aggregation of mineralisation deposits in extracellular matrix. These results suggest that Cbfa1 is a master gene controlling the functions of all the skeletal cell lineages by synthesising different functional isoforms. Furthermore, Cbfa1 couples the process of chondrocytes maturation, extracellular matrix mineralisation and degradation, as well as osteoblasts invasion during endochondral bone formation. Beyond its function on embryonic development, Cbfa1 regulates the postnatal growth of mandibular condyle.

Animals↗

Enhancement of toluidine blue staining by transforming growth factor-beta, insulin-like growth factor and growth hormone in the temporomandibular joint of aged mice.

Osteoarthritic lesions appear in the articular cartilage of the temporomandibular joint of mice aged 7 months and older. Reduced rate of proteoglycan (PG) synthesis leading to destruction of the articular cartilage was observed in this joint. The purpose of the present study was to test the ability of transforming growth factor-beta1 (TGF-beta1), insulin-like growth factor-1 (IGF-1) and growth hormone (GH) to induce PG synthesis in joint cartilage of aged animals and to compare it with the effect of interleukin-1alpha (IL-1alpha). Mandibular condyle explants from 18-month-old mice were cultured up to 72 h in serum-free medium, supplemented with IL-1alpha (TGF-beta1 (0.1-5.0 ng/ml), TGF-beta1 (1.0 ng/ml) + IGF-1 (2 ng/ml) or GH (10 ng/ml). The incorporation of (35)S-SO(4) into sulfated PG was tested. Cartilage samples were processed for histomorphometry using sections stained with 0.1% toluidine blue (TB), pH 1.8. Results indicated that in cultures supplemented (48 h) with either TGF-beta, TGF-beta + IGF-1 or with GH, an increased height and area of TB-positive staining as well as increased incorporation of (35)S-SO(4) into sulfated PG were observed. In contrast, the cytokine IL-1alpha exerted an inhibitory effect on TB staining and on (35)S-SO(4) incorporation. The present study demonstrated that in vitro supplementation of IL-1alpha to mandibular condyle cartilage reduced the height and area of TB staining and incorporation of (35)S-SO(4), whereas TGF-beta1, TGF-beta1 + IGF-1 or GH increased the height and area of TB staining and increased incorporation of (35)S-SO(4). The two parameters used to identify increased PG synthesis were shown to reveal similar results and were useful for studying the dynamic events taking place in cartilage destruction and repair in osteoarthritis.

Age Factors↗

Internal structure of the temporomandibular joint and the circumferential bone: comparison between dentulous and edentulous specimens.

To clarify changes in the trabecular structure due to loss of the teeth, the author compared soft X-ray images and morphological measurement values of the mandibular condyle and articular eminence between dentulous and edentulous specimens. The center of the skull base containing the temporomandibular joint was removed along the Frankfort horizontal and median sagittal planes. A block in the center of the cranial base was rejected using the Frankfort horizontal plane and median sagittal plane as references. The specimens were embedded in polyester resin by the routine method. The hardened specimens were horizontally cut into 500 microns sections and photographed using soft X-ray films. Soft X-ray of each section was taken for observation by naked eye and morphometry by computer. Observation of the compact bone in the articular eminence showed thinner compact bone on the posterior slope of the articular eminence, which is a functional plane, than on the anterior slope of the articular eminence. There was a trabecular bone group on the lateral area running from the compact bone on the posterior surface of the articular eminence into the zygomatic arch and a thick trabecular bone group in a network pattern on the medial area. In the central area of the mandibular condyle, spongy bone was surrounded by oval compact bone, and the internal trabecular bone ran anteromedially in nearly the same pattern as the arrangement of the lateral pterygoid muscle. At all sites, the density, width, extent, and index indicating the complexity of the trabecular bone had higher values in dentulous specimens than in edentulous specimens.

Aged↗

[A primary study on the relationship between condyle position and anterior distraction for cross bite caused by cleft lip and palate].

OBJECTIVE: To evaluate the changes of the position of the mandibular condyle in cleft lip and palate patients with secondary bony cross-bite deformity after early orthodontic treatment with extraoral bow and facial mask. METHODS: The TMJ topograph 6 months before and after treatment was investigated in 8 patients. The width of the anterior,superior and posterior space of the TMJ was compared prior to and post treatment. RESULTS: The results showed that there was no significant difference in the width of the three spaces of the TMJ before and after treatment. CONCLUSION: The position of the mandibular condyle had no significant change after maxillary anterior distraction with extraoral bow and facial mask.

English Abstract↗

Advances in histological methods open up new perspectives for craniofacial growth research.

Changes in the tissue architecture and composition which accompany growth and development have traditionally been mapped using histological methods. The modern technology now offers new possibilities which can be used in connection with light microscopy and electron microscopy. These techniques, particularly immunohistochemistry and in situ hybridization allow studies on spatial and temporal changes in molecular patterns of substances during tissue organization and cell differentiation. In this paper, we describe the principles of immunohistology, autoradiography, and in situ hybridization, and review our recent studies in which we have applied such methods to assess craniofacial development. We have used autoradiography to localize cell proliferation and epidermal growth factor (EGF) receptors in the developing mandibular condyle. We have also used immunohistochemistry to localize the extracellular matrix component, tenascin, in differentiating chondrocytes of the mandibular condyle, employing specific antibodies. In studies on the odontogenic potential of dental papilla mesenchyme, we have used hybridoma technology, and produced monoclonal antibodies against dental papilla mesenchyme. Most recently, we have used in situ hybridization, which allows detection of gene expression in tissue sections to localize transcripts of a fibroblast-growth-factor related gene (Int-2 proto-oncogene) in developing teeth. In future, successful combination of such new histological methods and traditional experimental procedures can be expected to produce new answers to the questions about the regulation of craniofacial growth.

Facial Bones↗