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PubMed1992

[The temporomandibular joint].

With its discordant articular surfaces and complete division in two cavities separated by a disk, the temporomandibular joint appears as a complex anatomical and functional entity. Combined movements involving anteroposterior gliding between the disk and temporal bone in the upper cavity, anteroposterior condyle translation, hinge and rotation movements between the disk and mandibular condyle contribute to the different movements of the jaw. With dental occlusion, the masticatory apparatus therefore includes five functionally coordinated articular compartments. Various impairments of the normal static and dynamic features of the temporomandibular joint may lead to relatively frequent pathological conditions which can be easily diagnosed by modern imaging and arthroscopic methods.

Diagnostic Imaging↗

PubMedDate not supplied

Facial nerve paralysis following mandibular trauma: a case report.

A strong posteriorly directed force applied to the mandible resulting in fracture, can also displace the mandibular condyle towards the external auditory canal or superiorly against the mandibular fossa, causing its penetration into the middle cranial fossa or even the fracture of the temporal bone. We report the case of a 30-year-old male patient victim of a bicycle accident that developed facial expression muscles paralysis on the left side soon after the trauma. On physical examination he presented left side postauricular ecchymosis, diminished muscular tonus of the left mouth angle and difficulty to close the left eye, he did not present clinical signs of facial fractures. The neurological and CT scan examination revealed fracture of the left temporal bone with total facial expression muscles paralysis. The patient was referred to the neurosurgical team for evaluation and they opted for a conservative treatment. After 3 months the patient showed a marked improvement with almost normal facial expression muscle movements. The trauma dynamics and treatment details are discussed.

Adult↗

PubMed1979

Skeletal changes in the condylar cartilage of the neonate mouse mandible.

Histological and histochemical qualitative and quantitative determinations are provided concerning the skeletal changes taking place in the growth center of the mandibular condyle in the neonatal ICR mouse. This study followed the changes in both the major matrical components (collagen, acidic glycosaminoglycans and glycolipids) as well as in the various cartilage cells throughout the maturational period of the neonatal condyle. It was found that the transformation of neonatal condylar cartilage to its mature form involved a significant decrease in its acid glycosaminoglycan content concomitant with a rapid increase in its collagen content. In addition, significant quantitative changes were found within the zone of hypertrophic chondrocytes. The period of highest growth activity along the mandibular posterior vertical dimension (ramus) was between birth and weanling 3rd postnatal week). At this time interval, the adaptive abilities of the growing condyle appeared maximal. A high degree of correlation was noted between the overall reduction in the height of the condylar cartilage and that of its hypertrophic zone. Further, the increase in the ramal height was highly correlated with the structural changes characteristic of the neonatal condyle.

Age Factors↗

PubMed1982

Measurement of condylar loading forces by instrumented prosthesis in the baboon.

Mathematical models have been developed to predict hypothetical forces acting on the mandibular condyles during mastication, but no direct measurements of condylar forces in vivo have been reported. This preliminary study presents the technical development of an instrumented prosthesis which was implanted in the mandibular ramus of a baboon, and some preliminary data collected while measuring with this prosthesis the condylar forces exerted during simulated mastication under general anaesthesia. Simulated mastication was induced by stimulating the motor tracts of the trigeminal nerve bilaterally, and the forces in response to increasing amperage were recorded. The pathogenesis of TMJ degeneration may be more fully understood by directly measuring the direction and magnitude of forces acting on the condyles during function. In addition, the future development of a total TMJ replacement for traumatized, deranged, or degeneratively impaired joints, must be accomplished with reliably engineered prostheses based upon direct force measurements.

Animals↗

PubMed2002

A study of the movements of the human temporomandibular joint complex in the cadaver.

The objective of this study was to define the movements in the sagittal plane of the articular disk relative to the temporal bone and the mandibular condyle respectively, on jaw-opening in the absence of loads. Four temporomandibular joints from two human cadavers were used as materials in the study. Ten steel needles were placed in the lateral plane. Lateral photographs were taken of the articular area in different mandibular positions. OXY reference systems were adapted to the temporal and condylar points. The movements of the disk relative to the temporal bone are statistically different from those relative to the condyle. These findings are consistent with the new concept that the mandible joins the skull through two Temporomandibular Joint Complexes (TMJCs), one on each side and each one made up of a reciprocally fitting temporodiskal joint and a disko-condyle of the condylar type.

Algorithms↗

PubMed1984

Mandibular subluxation for high carotid exposure.

Twenty-four patients with internal carotid artery lesions extending above the second cervical vertebra underwent mandibular subluxation for additional exposure. The original technique of bilateral arch bar wiring requiring 90 minutes for application has evolved into a circummandibular/transnasal wiring technique requiring approximately 10 minutes. Subluxation of the mandibular condyle 10 to 15 mm anteriorly results in displacement of the mandibular ramus 20 to 30 mm anteriorly. This technique provides a marked increase in exposure of the internal carotid artery up to the base of the skull by transforming a triangular operating field into a rectangular field. The technique is quick, easy to perform, and not associated with objective or subjective temporomandibular joint dysfunction.

Adult↗

PubMed1993

Effect of maxillomandibular fixation on condylar growth in juvenile Macaca mulatta: a cephalometric and histologic study.

The effect of maxillomandibular fixation on the growth of the mandibular condyle was studied in eight control and eight experimental male juvenile monkeys. All animals had metallic implants placed throughout the craniofacial complex in order to facilitate cephalometric analysis of growth-related changes in the maxillomandibular complex during jaw immobilization. Every 3, 6, 12, and 24 wk after insertion of the appliance two experimental animals were killed for histologic analysis. Cephalometric analysis indicated no major deviation from normal maxillary or mandibular growth in the experimental animals. The condylar growth in the experimental animals was comparable with that of the controls. Histologic analysis indicated that the articular connective tissue in experimental joints remained the same thickness as in the controls. On the postero-superior aspect of the condyle, the thickness of the prechondroblastic-chondroblastic cell layer was reduced by 70-80% in the experimental animals. On the posterior aspect this cell layer was not visible after 12 wk of fixation, but was replaced by a periosteum-like, cell-rich tissue which appeared to be active in appositional formation of cancellous bone. These results indicate that long-term maxillomandibular fixation does not cause major alterations in the growth of condyle or the entire mandible despite a profound decrease of the prechondroblastic-chondroblastic cell layer in the postero-superior and posterior regions of the condyle. The growth is probably due to a compensatory appositional bone formation along the surface of the condyle. It is also concluded that jaw mobility is not a prerequisite for normal maxillary or mandibular growth.

Animals↗

PubMed1999

The theoretical optimal center of rotation for a temporomandibular joint prosthesis: a three-dimensional kinematic study.

A unilateral temporomandibular joint (TMJ) prosthesis may cause dysfunction of the contralateral, natural TMJ because of lack of translatorial movements of the prosthetic side. The natural translatorial capacity of the mandible can be restored in part by a TMJ prosthesis with a fixed center of rotation (CR), positioned inferiorly to the center of the natural mandibular condyle. The aim of this study was to determine the optimal position for the fixed CR of a unilateral TMJ prosthesis. A mathematical model was used to analyze different positions of the CR. These positions were evaluated based on the calculated rotation of the mandible in the frontal (theta f) and horizontal (theta h) plane, and the mediolateral movement (MLM) of the contralateral natural condyle. For current TMJ prostheses, with the CR positioned in the center of the natural condyle, theta h exceeded the natural limits. When the CR was shifted inferiorly, all parameters improved, particularly theta h. The addition of an anterior shift to an inferior shift slightly worsened theta f, while the addition of a posterior shift to an inferior shift slightly improved theta f and worsened MLM. We concluded that the functioning of the contralateral TMJ improves by shifting the CR inferiorly. An anterior shift may be added to remain within the contour of the mandibular ramus. The proposed position of the CR is 15 mm inferior to the center of the natural condyle, combined, if necessary, with an additional anterior shift of 5 mm.

Humans↗

PubMed1989

[Study of the structural compensation of the mandible during treatment with cervical headgear].

This study was performed on two cephalometric films of each fourteen subjects with skeletal class 1 facial structure and Angle Class II molar relation treated with cervical headgear for a period 0.777 +/- 0.06 years; and of each thirteen control subjects with skeletal class 1 facial structures and normal occlusion observed for a period of 0.807 +/- 0.03 years. The correlation coefficients for the longitudinal changes of angular and linear measurements during control and treatment periods in both groups were evaluated. The correlation coefficients belonging to each group were compared; and the compensational regions during cervical traction were investigated. It was concluded that; the structural compensations occurred in the mandible according to the inhibition of the mesial migration of lower permanent first molars because of the interdigitation with the upper ones were the increase in the ramus inclination, change in the growth pattern of the mandibular condyle, increases in the gonial angle, lower anterior facial height and the mandibular plane angle.

Cephalometry↗

PubMed1998

Condylar growth and glenoid fossa displacement during childhood and adolescence.

This study evaluated age and gender differences in the growth of the mandibular condyle and displacement of the glenoid fossa. The results pertain to longitudinal samples of untreated French Canadians, including 118 children and 155 adolescents. Childhood and adolescent growth were described for girls aged between 6 and 10 years and 9 and 13 years, respectively, and for boys aged between 8 and 12 years and 11 and 15 years, respectively. Four-year growth changes of the cephalometric landmarks condylion and articulare were evaluated. Mandibular and cranial/cranial base structural superimpositions were used to assess condylar growth and fossa displacement, respectively. The results showed that the condyle grew between 0.8 and 1.3 mm posteriorly and between 9.0 and 10.7 mm superiorly over the 4-year periods; the articulare landmark showed significantly more posterior and less superior growth than the condylion landmark. Relative to the cranial base reference structures, the fossa was displaced between 1.8 and 2.1 mm posteriorly and between 1.0 and 1.8 mm inferiorly. The articulare showed significantly more inferior movement than the condylion. Boys showed significantly greater superior condylar growth during adolescence than during childhood. The glenoid fossa demonstrated greater posterior and inferior displacement during adolescence than during childhood.

Adolescent↗

PubMed1993

Initiation of secondary cartilage in the mandible of the Syrian hamster in the absence of muscle function.

The functioning lower jaw is a prerequisite of the ongoing secondary chondrogenesis in the mammalian mandibular condyle. Does the articular function also initiate secondary chondrogenesis in the mandible? The angular process of the fetal mammalian mandible possesses a large secondary cartilage without any apparent articular function. Past studies have shown that the anlage of the lower jaw of the mouse embryo grown in organ culture produces condylar and angular cartilages as in vivo. In order to clarify further the capacity of the mandibular anlage to initiate secondary chondrogenesis in a non-functional environment, mandibular arch explants taken from the prenatal hamster before any cartilage or bone formation was apparent were grown in organ culture. Both primary and secondary cartilage could be found in them within 9-10 days. The results thus indicate that initiation of the condylar and/or angular secondary cartilaginous development in the rodent mandible occurs in the absence of jaw-opening function, although the pertinent literature indicates that function maintains cartilaginous differentiation in the condyle.

Animals↗

PubMed2002

Masticatory form and function in the African apes.

This study examines variability in masticatory morphology as a function of dietary preference among the African apes. The African apes differ in the degree to which they consume leaves and other fibrous vegetation. Gorilla gorilla beringei, the eastern mountain gorilla, consumes the most restricted diet comprised of mechanically resistant foods such as leaves, pith, bark, and bamboo. Gorilla gorilla gorilla, the western lowland gorilla subspecies, consumes leaves and other terrestrial herbaceous vegetation (THV) but also consumes a fair amount of ripe, fleshy fruit. In contrast to gorillas, chimpanzees are frugivores and rely on vegetation primarily as fallback foods. However, there has been a long-standing debate regarding whether Pan paniscus, the pygmy chimpanzee (or bonobo), consumes greater quantities of THV as compared to Pan troglodytes, the common chimpanzee. Because consumption of resistant foods involves more daily chewing cycles and may require larger average bite force, the mechanical demands placed on the masticatory system are expected to be greater in folivores as compared to primates that consume large quantities of fleshy fruit. Therefore, more folivorous taxa are predicted to exhibit features that improve load-resistance capabilities and increase force production. To test this hypothesis, jaw and skull dimensions were compared in ontogenetic series of G. g. beringei, G. g. gorilla, P. t. troglodytes, and P. paniscus. Controlling for the influence of allometry, results show that compared to both chimpanzees and bonobos, gorillas exhibit some features of the jaw complex that are suggestive of improved masticatory efficiency. For example, compared to all other taxa, G. g. beringei has a significantly wider mandibular corpus and symphysis, larger area for the masseter muscle, higher mandibular ramus, and higher mandibular condyle relative to the occlusal plane of the mandible. However, the significantly wider mandibular symphysis may be an architectural response to increasing symphyseal curvature with interspecific increase in size. Moreover, Gorilla and Pan do not vary consistently in all features, and some differences run counter to predictions based on dietary variation. Thus, the morphological responses are not entirely consonant with predictions based on hypothesized loading regimes. Finally, despite morphological differences between bonobos and chimpanzees, there is no systematic pattern of differentiation that can be clearly linked to differences in diet. Results indicate that while some features may be linked to differences in diet among the African apes, diet alone cannot account for the patterns of morphological variation demonstrated in this study. Allometric constraints and dental development also appear to play a role in morphological differentiation among the African apes.

Adaptation, Physiological↗

PubMed1998

The instantaneous center of rotation during human jaw opening and its significance in interpreting the functional meaning of condylar translation.

Mandibular condyles translate back and forth during mouth closing and opening in primates and most other mammals. To account for the functional significance of this phenomenon, several hypotheses have been proposed. The sarcomere-length hypothesis holds that condylar translation provides a mechanical advantage by minimizing sarcomere-length changes in the masseter-medial pterygoid complex throughout a wide range of jaw openings. As the hypothesis is inherently associated with the locations of the instantaneous centers of rotation (ICRs) of the mandible, a more accurate determination of this variable would help test this hypothesis. This study investigated ICRs in the sagittal plane during human symmetrical mandibular opening based on a recently developed analytical method. The results confirmed that, with inter- and intraindividual variation, the natural opening was a simultaneous rotational and translational motion. In addition, the ICR was found to lie closer to the condyle during the first 10 degrees than during the rest of the rotation. This suggests that for the condyles the rotational component is somewhat more significant at the early phase than at the late phase of the opening stroke. For the whole range of the natural opening, the grossly approximated centers of rotation (CRs) scattered below the palpable lateral condylar poles in the superior half of the ramus. This study supports neither the ICR path determined by Grant ([1973], J. Biomech. 6:109-113) nor the conclusions reached by recording manually operated jaw movements in human cadavers (Rees [1954] Br. Dent. J. 6:125-133). Moss's suggestion ([1960] Disorders of the Temporomandibular Joint (Philadelphia: W.B. Saunders), pp. 73-88) that the center of rotation lies at the lingula is also not confirmed. Although the new data cannot reject the sarcomere-length hypothesis, they do not strongly support it either. Another hypothesis is proposed in this study as plausible. With this hypothesis, translation is regarded as an adaptation to the use of the inferior head of the lateral pterygoid as a jaw depressor in noncarnivorous mammals. Potential functional advantages of this portion of the muscle are also discussed.

Biomechanical Phenomena↗

PubMed2003

Mandibular distraction osteogenesis using an intraoral device and bite plate for a case of hemifacial microsomia.

OBJECTIVE: To present orthodontic treatment combined with mandibular distraction osteogenesis using an intraoral device and a bite plate in a patient with hemifacial microsomia, severe facial asymmetry, and unilateral mandibular hypoplasia. PATIENT: An 8-year-old girl exhibited mandibular deviation resulting from hypoplasia of the mandibular condyle and ramus on the left side. The patient was treated with an intraoral device for mandibular distraction osteogenesis, bite plate, and hybrid-type functional appliance. Facial asymmetry was improved, and the mandibular ramus was elongated in an anterior and primarily posterior direction with slightly posterior and superior displacement of the proximal segment. Postdistraction treatment results have been stable for 1 year. At the 1-year follow-up, the volume of the lateral and medial pterygoid muscles on the left side had increased. The condyle and disc on the right temporomandibular joint moved well and in harmony at open mouth position, and a rotational movement of the left temporomandibular joint was observed.

Cephalometry↗

PubMed1989

The effects of mandibular immobilization on the masticatory system. A review.

It is clear from this review that mandibular immobilization is not as benign a procedure as once thought. Detrimental effects on several tissues within the masticatory apparatus have been observed following mandibular immobilization. Atrophy of the muscles of mastication, degenerative changes within the mandibular condyle, and decreases in range of passive bite opening are all consistent findings following several weeks of mandibular immobilization. The use of fixation procedures which avoid the use of mandibular immobilization (i.e., rigid internal fixation) has been shown to minimize these problems. As with any procedure, however, the risks and benefits of rigid internal fixation must be weighed against the time-honored standard (i.e., maxillomandibular fixation). It is hoped that future research and clinical experience will direct the surgeon to select whichever technique is in the best interest of the patient.

Fracture Fixation, Internal↗

PubMed1985

Morphologic and cytochemical changes in maturing and osteoarthritic articular cartilage in the temporomandibular joint of mice.

We studied the light microscopic, ultrastructural, and cytochemical characteristics of the temporomandibular joints of male ICR mice, from early neonatal life until they reached senescence, when spontaneous osteoarthritis is a common phenomenon. Aging of mandibular condylar cartilage was accompanied by decreasing total proteoglycan content and by an unmasking of collagen fibers, with no shift in collagen type. Fibronectin was also commonly present on the articular surface of specimens from old animals. Chondrocytes of aged mice contained an increased number of lysosomes, and their adjacent matrix vesicles reacted positively for acid phosphatase and arylsulfatase, but not for alkaline phosphatase. Such vesicles were also found to be devoid of calcium complexes and, thus, did not appear to be involved in the mineralization process. Similar age-related changes have been described in human mandibular condyles; hence, the male ICR mouse could serve as a useful model for studies of spontaneous osteoarthritis in the human mandibular joint.

Acid Phosphatase↗

PubMed2000

Dislocation of the mandible: a case report.

Dislocation of the mandible is a possible complication of direct tracheal laryngoscopy. The temporomandibular joint (TMJ) is unique in that any movement of the bone always causes movement in both joints simultaneously. The entire TMJ is surrounded by a ligamentous capsule and is stabilized by 3 ligaments. Four muscles of mastication move the mandible with great power. The lateral pterygoid muscle has nearly horizontal muscular fibers and is chiefly responsible for dislocating the mandibular condyle and articular disc past the articular eminence into the infratemporal fossa, causing the patient great pain and distress. If mandibular dislocation should occur, prompt recognition and treatment of the dislocation is recommended. There are steps, used by dentists, which can be employed by the nurse anesthetist to relocate the mandible. The technique for intraoral bimanual relocation of the mandible is described.

Aged↗

PubMed1989

Jaw fractures in the country of Stockholm (1978-1980). Injury dynamics--etiologic factors in relation to anatomic site of fracture.

This paper presents a retrospective review of jaw fractures sustained by 795 individuals in the county of Stockholm from 1978-80. The material comprised 904 mandibular and 249 maxillary fractures, a total of 1.153 fractures. The present part of the study concerns the relationship between etiologic factors and fracture location. Single fractures were noted in 43% of the mandibular fractures and in 4% of the maxillary fractures. The region most frequently fractured was the mandibular condyle (19% of all fractures). Violence was the etiologic in 42% of the total number of fractures and 47% of mandibular fractures. Compared to earlier reports, this seems to represent an increase over the last decades and probably reflects a general trend towards greater incidence of violence in society. Jaw fractures caused by traffic accidents accounted for 25% of all fractures and have decreased, probably as a result of the safety belt law of 1975 and better traffic security reforms. However, the severe Le Fort III fractures, combined with unconciousness and neurological injuries, are mainly the result of on traffic accidents. Falls accounted to 23% of the fractures, mostly localized to the mandible (81%).

Accidents↗