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In 51 human fetuses from the first half of the prenatal period, developmental stages in the symphysis menti and the mandibular condyle were assessed by histochemical reactions. The study showed the association between the timing of the developmental stages in the two mandibular growth zones.
The high condylar shave has the disadvantage of removing the articular soft tissue cover together with the underlying condylar bone. In an attempt to overcome this disadvantage, we elevated the articular soft tissue cover, shaved the condylar head, and replaced the articular soft tissue cover in its original position in nine adult rabbit temporomandibular joints. On the contralateral joints, the same amount of bone was shaved together with the articular soft tissue cover. The rabbits were killed after 3 months, and the condyles were macroscopically and histologically evaluated. All condyles were covered with an articular soft tissue layer in the area operated on. This surface was smoother when the articular soft tissue cover was preserved. Histologically, the subarticular layer of cartilage cells was continuous in the joints with preservation of the articular soft tissue cover but was frequently interrupted in the joints where this cover was removed. The incision made in the posterior part of the articular surface for elevating the articular soft tissue cover frequently caused a deformity of the condyle and an interruption of the subarticular layer of cartilage. The results suggest that preservation of the articular soft tissue cover on the mandibular condyle might be one way to improve the postoperative morphology after high condylar shave. The technique in its present state has obvious drawbacks and should be further refined before it is considered for clinical application.
Indian hedgehog (Ihh) is a critical mediator transducing mechanical signals to stimulate chondrocyte proliferation. To clarify the cellular signal transduction pathway that senses and converts mechanical signals into tissue growth in mandibular condyle, we evaluated Ihh expression and its relation to the kinetics of replicating mesenchymal cells in condylar cartilage during natural growth and mandibular advancement. Thirty-five-day-old Sprague-Dawley rats were fitted with functional appliances. Experimental animals with matched controls were doubly labeled with iododeoxyuridine and bromodeoxyuridine so that we could evaluate the cycles of the proliferative mesenchymal cells. Mandibular advancement triggered Ihh expression in condylar cartilage. A higher level of Ihh expression coincided with the increase of the replicating mesenchymal cells' population and the shortening of the turnover time. These findings suggested that Ihh acts as a mediator of mechanotransduction that converts mechanical signals resulting from anterior mandibular displacement to stimulate cellular proliferation in condylar cartilage.
We have studied and treated 12 selected cases of condylar hyperplasia. All of our cases showed no clinical or instrumental sign of still active hyperplastic growth of the mandibular condyle. The cephalometric studies demonstrated in all cases a pathologic vertical growth of the maxilla interesting the posterior segments on the same side of the hyperplastic condyle. We decided not to perform a condylectomy because we did not expect the condyle to grow any further. The treatment consisted of Le Fort I osteotomies and sagittal split osteotomies sometimes in combination with genioplasty and mandibular remodeling. The mandibular physiologic movements were preserved in all cases.
INTRODUCTION: The purpose of this study was to investigate the relationship between muscle conduction velocity (MCV) of the masseter muscle and the direction of mandibular growth. METHODS: Longitudinal cephalometric X-rays taken at the prepubertal and postpubertal periods of 16 Japanese girls were analyzed. MCV was calculated from the delay in myoelectric signals obtained by using multiple surface electrode arrays placed along the fibers of the left masseter muscle in the postpubertal period. The direction of mandibular growth was evaluated by superimposition of the lateral cephalometric X-rays at the prepubertal and postpubertal periods. The relationship between MCV and the direction of mandibular growth was analyzed statistically. RESULTS: MCV was significantly correlated with the vertical facial height at the postpubertal period and the direction of mandibular condyle growth. CONCLUSIONS: If the relationship between prepubertal and postpubertal of MCV is clarified, it might be possible to predict the direction of mandibular growth and the vertical facial proportions at the postpubertal period from MCV of the masseter muscle at the prepubertal period.
The vertebrate articular tissue consists of collagen fibers embedded in a ground substance. Collagen resists tensile forces, while proteoglycans in the ground substance provide resilience and resistance to compression. It was hypothesized that unilateral bite raise would induce increasing expression of proteoglycans in TMJ articular tissues. As a test of this hypothesis, six- and nine-week-old Sprague-Dawley rats received unilateral bite-raising appliances bonded to their right upper molars for 4 wks. A group of nine-week-old rats was housed for an additional 4 wks after removal of the appliances they had worn for 4 wks. Proteoglycans that carry abundant chondroitin sulfate and keratan sulfate side-chains, most likely aggrecans, were detected by safranin O in the fibrocartilaginous zone of the condyle in parasagittal sections. A monoclonal antibody against a large chondroitin sulfate proteoglycan related to versican reacted strongly in the surface fibrous layer of the mandibular condyle and moderately in the discs of the treated specimens. Computer quantification for safranin O and anti-versican antibody staining revealed that the average intensities of the treated specimens were significantly higher than those of their corresponding sham-operated controls, and the average intensities of the treatment-reversal specimens had no significant differences from their corresponding sham-operated controls. Thus, unilateral bite raise appeared to have induced an increase in the expression of aggrecan in the condylar cartilage and a proteoglycan related to versican in the TMJ disc and the articular surface of the condyle. The elevated proteoglycan expression is interpreted to suggest that unilateral bite raise leads to an increase in the magnitude of compressive forces in the rat temporomandibular joint.
The purposes of the present investigation were to: 1)locate the instantaneous rotation center of mandible autorotation during maxillary surgical impaction; 2) identify the discrepancies between the resultant mandibular position following by maxillary surgical impaction and presurgical predictions, which use the radiographic condylar center as the rotation center for mandibular autorotation; and 3)find the interrelation between the magnitude of maxillary surgical impaction and the sagittal change of mandible. Ten patients underwent maxillary LeFort I impaction without concomitant major mandibular ramus split osteotomies were included. The preoperative (T0) and postoperative (T1) lateral cephalograms were used to evaluate the surgical changes and locate the center of rotation of mandibular autorotation with Reuleaux method. Prediction errors were measured by comparing the predicted (Tp) and postoperative (T1) cephalometric tracings. The magnitude of the maxillary surgical impaction was compared to the positional changes of mandible after mandibular autorotation with correlation and regression analysis. The results demonstrated that the centers of mandibular autorotation located 2.5 mm behind and 19.6 mm below the radiographic condylar center of the mandible in average with large individual variations. By using the radiographic condylar center of the mandible to predict the mandibular autorotation would overestimate the horizontal position of chin by 2 mm and underestimate the vertical position of chin by 1.3 mm following an average of 5 mm surgical maxillary impaction. The magnitude of maxillary impaction was highly and positively correlated to the horizontal displacement of chin position. The rotation centers of mandibular autorotation following by maxillary LeFort I impaction osteotomies might not usually locate at the radiographic condylar center of the mandible also with large individual variations in their positions. Surgeons and orthodontists should be aware of the horizontal and vertical discrepancies of chin positions while planning a two-jaw surgery by using the radiographic center of mandibular condyle as the rotation center in mandibular autorotation.
Attempts to increase mandibular growth by the stimulation of condylar proliferative activity, either experimentally or with functional appliances in humans, have led to controversial results. The aim of this study was to measure changes in proliferative activity in the mandibular condyle after steady experimental posterior relocation of the glenoid fossa in the rabbit without actively interfering with normal masticatory action. The method differed from most previous experimental procedures, which force the mandible anteriorly to stimulate functional appliance therapy. Twelve 5-day-old rabbits underwent gluing of the interparietal, temporoparietal, and lambdoidal sutures. Three experimental and three control rabbits were injected with tritiated thymidine at 10, 15, 20, and 30 days and were killed after 2 h for histological and autoradiographic examination. The total number of labeled cells in the prechondroblastic layer was higher in the experimental group, the difference being greatest in the 20-day-old rabbits. The highest proliferative activity in the experimental group was found in the area immediately posterior to the articular contact surface. There was a tendency for the cartilage layers to be thicker in the experimental group, especially in the extreme anterior segments of the condyle.
Long follow-up in TMJ patients shows often a lack of success with a recurrence of pain. To lower the rate of failures or at least partial failures, the relative positions between mandibular condyle and glenoïd fossa were studied, in case of recurrence after TMJ occlusal and surgical treatment: asymmetry was found between both sides. Sometimes the mandibular head is in a low and anterior position (in absence of major occlusal disorder): we call this "stretching syndrome" (for posterior apparatus). Patients complain of jaw instability. Sometimes the mandibular head is in a very high and posterior situation: we call this "compressive syndrome". In this case, patients complain of a recurrence of pain (generally the clicking disappeared after the first TMJ surgery). We propose in "stretching syndrome" to treat the instability by a cartilaginous graft, and in "compressive syndrome" to decompress the bone by drill tunnel with external effect (secondary bone settles down) and internal effect (venous drainage and oedema decrease). First results are good with a high healing rate, but the follow-up is not long enough to a complete assessment of this technic.
Controversy exists over the value of the TMJ condylar position in the fossa. Many clinicians associate the concentric position to the normal individuals and the retruded position to the dysfunctional condition. It is also recommended that therapeutically, the condyle should be placed on the posterior slope of the articulating eminence. Different groups of investigators claim that the condylar position, centric, retruded or protruded has little or no value and is not correlated with dysfunctional situations. This controversy is attributed to the inconsistency of research methodology. Using a large number of subjects, defining age and sex, careful selection of subject, using tomographic analysis with similar section locations and excluding individuals with disturbed occlusal condition are recommended for a research of this type. The conclusion is that the condylar position is an end product of many dynamic changes such as growth and remodeling, functional matrix activities, occlusal alteration, functional adaptation and individual variation. It is suggested that diagnosis and treatment of TMJ disorders should not be based solely on the radiographic position of the condyle. Consideration of general body conditions is an essential part of total patient management. TM joint condylar position has been explained as the position of the mandibular condyles in the glenoid fossa when teeth are in maximum intercuspation. Clinicians have based their diagnosis and treatment of temporomandibular joint disorder on this position. The optimal condylar position has been a controversial matter in dentistry for many years. The purpose of this paper is to review the literature pertaining to condylar position and to discuss its significance in clinical practice.
Disc-repositioning splints are routinely used in the treatment of anteriorly displaced discs. The rationale of these appliances is to direct the mandibular condyle anteriorly in the glenoid fossa and to recapture the disc onto the condyle. The stability of disc recapture depends on reestablishment of the occlusion and the adaptive capabilities of the temporomandibular joint. It could therefore be suggested that treatment success is potentially higher in the active growth period. In this case report, partial disc recapture was observed on magnetic resonance images after application of a maxillary disc-repositioning appliance. Orthodontic treatment was applied for the retention of disc recapture.
Four cases of bilateral mandibular condylysis are presented. The condition does not appear to be included in current teaching or existing nomenclature and consists of an acquired absence of the mandibular condyles, unassociated with temporomandibular ankylosis or aural/facial anomalies. In the literature of condylar maldevelopment four published cases appear to justify reclassification as bilateral mandibular condylysis, bringing the recorded total to eight. Whereas previous writers have regarded the condition as a prenatal condylar aplasia or hypoplasia, morphanalysis studies of the four current cases have shown that the probable aetiology is postnatal local disturbance in the condylar region. The term condylysis has been chosen to emphasise the locally destructive (or lytic) mechanism which appears to be involved. Mandibular condylysis is distinguished from condylar aplasia by its non-association with aural/facial anomalies and because normal development appears to proceed until the lytic event occurs. It is further distinguished from primary and secondary condylar hypoplasia because the condyle is absent rather than small, because normal development appears to proceed until the lytic event occurs and because of its non-association with aural/facial anomalies or temporomandibular ankylosis.
Elastic fibers are important components of the connective tissue that attaches the articular disk of the craniomandibular joint (CMJ) to the skull and mandible. Biopsies of the articular disk proper and bilaminar zone (BZ) tissues from patients with anterior disk displacement (ADD) have shown previously that there is a marked loss of elastic fibers. In the present study, the effects of inducing ADD on the elastic fibers in the rabbit CMJ disk proper, BZ and condylar cartilage were investigated. The right CMJ was exposed surgically and the discal attachments were severed except for the BZ attachments. Then, the disk was displaced anteriorly and sutured to the zygomatic arch. The CMJs were removed after 1, 2 or 6 weeks and processed for histochemical demonstration of elastic fibers. The results showed osteoarthritic changes following ADD, and a significant decrease in the number of the elastic fibers in the disk proper and BZ. The remaining elastic fibers were abnormal in their appearance and orientation. In addition, ADD led to the appearance of fine elastic fibers among the chondrocytes in the hyaline cartilage of the condyle that were not present in the cartilage of the control condyle. We conclude that induced ADD can lead to a significant loss of elastic fibers in the articular disk, and result in the appearance of elastic fibers within the cartilage of the mandibular condyle.
Electromyographical (EMG) activity was recorded bilaterally from the masseter and temporalis muscles of alert ferrets (Mustela putorius furo) during mastication and crushing. Electromyographic activity was also recorded during biting while a bite-force transducer placed between the carnassial teeth registered forces ranging from 1.5 to 48.8 N. Linear regression analysis demonstrates that temporalis and masseter EMG activity are linearly related to bite force. Electromyographic activity from the balancing-side muscles is nearly equal to EMG activity of the working-side muscles during bone crushing with the carnassial teeth. It is hypothesized that a high percentage of balancing-side muscle activity in ferrets can be recruited during carnassial biting because the postglenoid process prevents ventral displacement of the working-side mandibular condyle.
Apoptosis has been shown to be involved in remodeling of organs during development, and derangement of the apoptotic process may result in temporomandibular joint (TMJ) dysfunction or congenital malformation. To investigate the relationship between the development of the TMJ and apoptosis, rat fetuses at 17.5-20.5 days of gestation (E17.5-20.5, vaginal plug=E0) and rats at postnatal days 1, 2, 3, 5, and 10 (P1, 2, 3, 5, and 10) were examined by light (LM) and transmission electron microscopy (TEM) and electrophoretic analysis of DNA fragmentation. At E17.5 and 18.5, a few layers of slender mesenchymal cells which eventually develop into the TMJ disk were observed, although TEM or electrophoresis did not reveal apoptotic cells at these stages. At E19.5 and 20.5, all structures of the TMJ except the lower joint cavity could be distinguished, but at these stages apoptotic cells were not observed. In P1 condyles, apoptotic cells were observed by TEM both at the subsurface of the condyle and in the region at which the lateral pterygoid muscle attaches to the condyle. These apoptotic cells showed irregular chromatin condensation, convolution of the cell membrane, and fragmentation and disintegration of the cytoplasm. Electrophoretic analysis of the P1 condyle further confirmed DNA fragmentation. Apoptosis was not observed in all specimens at the P1 stage. It was confirmed in 8 out of 20 animals (10 out of 27 joints) by TEM and/or electrophoretic analysis. The shape of the upper portion of the condyle flattened progressively from E20.5 to P2. At this stage, the lower joint cavity was developing, as observed by LM. These findings suggest that the morphological changes of the mandibular condyle effected by apoptosis, together with development of the lower joint cavity, play important roles in the postnatal functional adaptation to external stimuli such as mechanical strain.
A 28-year-old woman involved in a motor vehicle accident sustained bilateral mandibular condyle dislocation into the infratemporal fossae. Conventional manipulations were unsuccessful in relocating the condyles. By simulating the dislocations on a dried skull, it was evident that the coronoid processes were trapped anteriorly and superiorly to zygomatic arches. An open surgical approach was required to relocate the condyles.
QUESTIONS UNDER STUDY: In this study, experimentally induced surgical defects of the mandibular condyle were evaluated histologically 3, 6 and 9 months postoperatively to investigate the capacity for remodelling which is one of the most important features of the temporomandibular joint. METHODS: In three healthy sheep standardised surgical defects were produced on each right condylar head. The left temporomandibular joints served as controls. No treatment was performed on the surgical defects and function was not restricted postoperatively. At the end of the experimental period the sheep were sacrificed and a histological evaluation was carried out. RESULTS: Histologically, no disturbance was observed during the healing process in bone and cartilage. Although function was not limited throughout the study, it was observed that the experimental surgical defects had healed completely. CONCLUSIONS: This result points to the condyle's high capacity for repair and remodelling.
OBJECTIVE: To establish an effective way in cryopreserving mandibular condylar cartilage cells. METHODS: Human mandibular condylar cartilage (MCC) cells were harvested and amplified by microcarrier culture technique. MCC cells were preserve in liquid nitrogen. The biological properties of cryopreserved MCC cells were investigated. RESULTS: Cells from liquid nitrogen preservation kept their phenotypic, proliferative an metabolic characteristics of MCC cells in vivo. CONCLUSIONS: Cryopreservation of MCC cells can supply adequate qualified cells for repairing the defects of mandibular condyle cartilage and temporomandibular joint disk.