Biomedical subjects

H U Luder

Publications and source records attributed to H U Luder.

At least 19 recordsLinked to original sources

PubMed2006

Tubular sclerosis rather than the smear layer impedes dye penetration into the dentine of endodontically instrumented root canals.

AIM: To evaluate the effect of different root canal irrigating regimes on dentine penetration of Patent Blue dye. METHODOLOGY: Eighty extracted single-rooted human mandibular premolar teeth with narrow root canals were prepared using ProFile instruments. After each instrument, canals were irrigated with 1% sodium hypochlorite. Subsequently, teeth were randomly assigned to receive a 10 mL rinse of aqueous 17% (w/v) ethylenediaminetetraacetic acid or tap water for 2 or 10 min, followed by a final rinse with a 2% Patent Blue dye solution for 2 or 10 min (eight groups, n = 10 teeth per group). Teeth were then horizontally sectioned 3, 6 and 9 mm from the apex. Sections were digitally photographed and dye penetration was calculated as percentage of total dentine area using NIH Image J. Values were compared using one-way anova and Bonferroni correction with the alpha-type error set at <0.05. Representative tooth sections from all groups were further analysed using scanning electron microscopy. RESULTS: No significant impact of irrigating protocols on dye penetration was found. Dye penetration was significantly (P < 0.001) greater in the coronal than middle, and in middle than in apical root thirds. When observed microscopically, irrigant penetration was independent of the presence of a smear layer, but was rather a function of tubular sclerosis. CONCLUSIONS: Tubular sclerosis, a physiological phenomenon that starts in the third decade of life in the apical root region and advances coronally with age, was the main factor influencing penetrability of root dentine.

Analysis of Variance↗

PubMed2006

A comparative study on the disinfection potentials of bioactive glass S53P4 and calcium hydroxide in contra-lateral human premolars ex vivo.

AIM: To evaluate the effects of bioactive glass S53P4 versus calcium hydroxide when used as dressings in contra-lateral human premolars infected with Enterococcus faecalis ATCC 29212. METHODOLOGY: Pairs of contra-lateral premolar teeth plus single control premolars were obtained from 23 individuals aged 10-26 years undergoing orthodontic treatment. Root canals of teeth with fully formed apices (nine contra-lateral pairs, seven controls) were instrumented using a size 60 FlexoFiles 2 mm short of canal length. Canals with open apices (six contra-lateral pairs, four controls) were circumferentially instrumented using a FlexoFile. Root canals were rinsed with 1% sodium hypochlorite and 10% citric acid. Teeth were then suspended in tryptic soy broth (TSB) and autoclaved. Positive controls and study teeth were infected with E. faecalis ATCC 29212 for 2 weeks in TSB, while negative controls were kept in sterile TSB. Subsequently, contra-lateral premolars were dressed with bioactive glass S53P4 (BAG) or calcium hydroxide suspensions for 10 days. Dentine samples were obtained from teeth with fully formed apices using ISO-size 70, 80 and 90 FlexoFiles to working length and cultured. Teeth with open apices were fixed, fractured and examined using scanning electron microscopy (SEM). RESULTS: Calcium hydroxide had a strong antibacterial effect and was significantly more effective than BAG in preventing residual bacterial growth (P < 0.01). SEM analysis revealed apparent substance-specific modes of action. CONCLUSIONS: Calcium hydroxide was an effective disinfectant in human teeth.

Adolescent↗

PubMed2005

Observations on pulpal response to carbon dioxide laser drilling of dentine in healthy human third molars.

Preservation of pulpal health is the primary prerequisite for successful application of laser systems in the hard tissue management of vital teeth. The purpose of this study was to investigate the short and long-term pulpal effects to cavity preparations in healthy human teeth using carbon dioxide (CO2) laser. A total of seven, healthy, third molars that were scheduled to be removed due to space problems were used. After the laser drilling, the occlusal cavities were closed temporarily, and the teeth were extracted 7 days (n=5) and 3 months (n=2) after the operation. The specimens were fixed, decalcified, subdivided and processed for light and transmission electron microscopy. Seven days postoperatively all the five teeth that had been irradiated with the CO2 laser did not reveal any pathological changes in the pulpo-dentine complex. Three months postoperatively the two teeth that were prepared with the laser showed subtle but distinct apposition of tertiary dentine that was lined with intact odontoblasts. One of the specimens at 3 months revealed the presence of a mild, but very circumscribed, pulpal infiltration of chronic inflammatory cells subjacent to the cavity preparation. The latter is unlikely to be due to a direct effect of the laser irradiation but a possible consequence of microleakage of oral antigens and/or other tissue-irritating molecules through the temporary restoration and the remaining dentine thickness (RDT). Although these preliminary histological results suggest that the CO2 laser under investigation induced only minimal response of the dentine-pulp complex when used as a hard-tissue drilling tool, with specific energy settings, pulse duration within thermal relaxation time and emitting radiations at 9.6 microm of wavelength, larger clinical trials involving various types of teeth are necessary to reach definite conclusions for large-scale clinical application of the laser device.

Carbon Dioxide↗

PubMed2005

Quantitative histological features and ultrastructure of opercula of human teeth showing normal and delayed eruption.

BACKGROUND: Failure of eruption of human permanent molars has been attributed to opercular lesions, although comparisons with specimens from normally erupting teeth are scarce. The aim of this study was to quantitatively analyse opercula associated with normal and delayed tooth eruption. METHOD: Twenty opercula covering permanent molars delayed in eruption were obtained from 13 patients aged 7.3-18.1 years. Six opercula from normally erupting molars of five 7.3-17.5-year-old subjects served as controls. Specimens were analysed light and electron microscopically and morphometrically. RESULTS: In addition to features recognized previously, prominent numbers of nerves, high endothelial-like venules and mast cells were observed. Ultrastructurally, large multinucleated cells did not reveal cell boundaries running between the nuclei, and mast cells seemed belonging to the MC(TC)-type. None of the features differed significantly between opercula from cases of delayed and normal tooth eruption. CONCLUSIONS: Disturbances of tooth eruption that are attributed to opercular lesions may represent retentions resulting from the failure of the eruption mechanism, rather than impactions because of a physical barrier.

Adolescent↗

PubMed1998

Age changes in the articular tissue of human mandibular condyles from adolescence to old age: a semiquantitative light microscopic study.

In a previous study (Luder, Anat. Rec., 1997;248:18-28), the articular tissue of the adult mandibular condyle was characterized semiquantitatively. However, questions about age changes of mature tissue were not answered, and the time course of tissue maturation from the end of condylar growth to the attainment of the adult appearance remained unknown. These issues are addressed in the present investigation. By using a light microscope, features of the superficial, intermediate, and deep articular tissue zones as well as of the subchondral bone were assessed at nine predetermined condylar sites. The frequencies of these features were recorded as scores from 0 (absent) to 10 (continuous) and were plotted against age. Analysis of covariance served for testing the significance of age and sex effects as well as intracondylar variability. Whereas almost all age-related changes in frequencies of tissue features were similar along the whole lateromedial dimension, changes at the putatively nonload-bearing, posterior slope differed significantly from those at the putatively load-bearing, anterior slope and zenith of the condyle. Two patterns of changes were noted. Frequencies of a first group of tissue features altered mainly during the age period from 15 years to 30 years and remained more or less stable thereafter. This course was characteristic for 1) a progressive cartilaginification of the superficial zone as well as 2) the disappearance of hypertrophic growth cartilage and 3) the appearance of grid-fibrous fibrocartilage in the deep zone, which were accompanied by 4) a decline in endochondral ossification and 5) the formation of a compact, subchondral bone plate. Frequencies of a second group of tissue features disclosed changes that continued up to middle and old age. This pattern was evident regarding 1) a decrease in the prominence associated with 2) a drop in cellularity and 3) progressive fibrosis or even cartilaginification of the intermediate zone. Among the age changes of condylar articular tissue, those affecting the superficial and deep zones as well as the subchondral bone are largely complete by about 30 years of age and seem to be related primarily to a gradual transition from growth to adulthood. In contrast, a second group of alterations, which progress to old age and involve mainly the intermediate zone, appears to be associated with continued maintenance and adaptive articular remodeling as well as possibly senescence. Both maturational and later age changes seem to depend markedly on articular load bearing.

Adolescent↗

PubMed1998

Nature and attachment of cementum formed under guided conditions in human teeth. An electron microscopic study.

In an attempt at characterizing the nature and attachment of cementum formed under conditions of guided tissue regeneration (GTR) in humans, front teeth from 4 patients aged 42 to 72 years were examined at the electron microscopic level. All teeth were affected by complex periodontitis associated with advanced loss of periodontal support. Roots were surgically planed and notched, but not chemically conditioned. Either the mesial or distal surface of each tooth represented the experimental site and was covered with a biodegradable polyglactin 910 barrier, while the opposite approximal surface served as control. Following 3 months of healing, teeth were removed together with surrounding periodontal tissues including some alveolar bone. These blocks were fixed histologically, decalcified, embedded in epoxy, and sectioned for examination in the scanning (backscatter mode) and transmission electron microscope. Both experimental and control sites disclosed 2 types of regenerative cementum that seemed to be formed by cells resembling cementoblasts. The first type was characterized by a thin fringe of collagen fibrils which were arranged perpendicular to the root surface and appeared mineralized in a zone extending about 1 to 3 microm from the dentin. The second type occurred as thick patches which revealed scattered cementocytes and sheets of collagen fibrils oriented mainly parallel to the root surface, running both circularly and axially. In both situations, a continuous, thin, electrondense layer was interposed between newly formed cementum and preexisting radicular hard tissues. Interdigitation of collagen fibrils from cementum and dentin, such as observed along the natural cemento-dentinal junction, did not occur. Thus, regenerative cementum laid down in humans under guided conditions on previously diseased and planed, but not otherwise treated root surfaces shares some morphologic features with cementum formed during spontaneous repair of root resorptions. However, unlike in the course of such repair, a fibrous attachment of new cementum resembling the natural cemento-dentinal junction does not seem to be regenerated under guided conditions.

Absorbable Implants↗

PubMed1997

Frequency and distribution of articular tissue features in adult human mandibular condyles: a semiquantitative light microscopic study.

BACKGROUND: The adult mandibular condyle is reported to be covered by fibrocartilage that develops from growth cartilage present earlier in life. Available data on the organization of condylar fibrocartilage are entirely descriptive or have been derived from young adult individuals. In order to examine the variability in normal appearance, condyles from a representative sample of adult humans were analyzed semiquantitatively. METHODS: With a light microscope, features of the superficial, intermediate, and deep tissue zones subjacent to small contiguous sectors of the articular surface were recorded. The distribution of each feature relative to the total surface was then calculated and respective data obtained from nine predetermined condylar regions and from males and females were compared using analysis of variance. RESULTS: The organization of the articular tissue varied significantly in the anteroposterior direction only. Unlike during growth, the superficial and deep zones in anterior and superior regions mostly contained fibrocartilage, although of markedly different appearance. Furthermore, the intermediate zone along about half of its anteroposterior extension lacked a distinctly visible layer, because the cell density was low and there was dense fibrous tissue or fibrocartilage similar to that of the superficial or deep zone, respectively. In these situations, zonation of the articular tissue was revealed only by the arrangement of collagen fibers. CONCLUSIONS: The appearance of adult condylar articular tissue, in addition to varying considerably within and between putative load-bearing and nonload-bearing regions, bears only a vague resemblance to the layered organization of the growing condyle. Current terminology that refers to that organization, therefore, is inappropriate. It is proposed to designate impartially the three articular tissue zones of the adult condyle as "superficial," "intermediate," and "deep."

Adult↗

PubMed1994

Perichondrial and endochondral components of mandibular condylar growth: morphometric and autoradiographic quantitation in rats.

In an attempt to determine the contribution of the perichondrial and endochondral components to rapid and slow overall condylar growth, mandibular condyles from rats aged 21 and 45 d as well as 3 and 6 months were examined by light microscopy. A morphometric analysis served to estimate the size of cells and the amount of extracellular matrix per cell in the various tissue layers beneath the articular surface. Quantitative evaluation of autoradiographic labelling due to the presence of [3H]-thymidine, [3H]-proline, and [35S]-sulphate 1.5 or 2 h and 5 d after injection of the tracer was used to determine the velocity of overall condylar growth. A combination of the two types of results allowed the calculation of daily rates in (1) the generation of new chondrocytes, constituting the perichondrial growth component, and the endochondral components comprising (2) net accumulation of extracellular matrix in the cartilage and (3) enlargement of the chondrocytes. It was observed that the 3 factors contributed, respectively, by about 10-25, 30 and 45-60% to rapid growth and by about 75, 15 and 10% to slow growth. Thus when growth slowed, the contribution of chondrocyte enlargement declined markedly and that of matrix accumulation slightly, while the contribution of new cell generation increased correspondingly. Declines in chondrocyte enlargement and in accumulation of cartilage matrix that was related mainly to decreasing proteoglycan formation were in good agreement with age-associated variation in weight gain, while peak rates in generation of new chondrocytes appeared to be delayed against peak somatic growth. It is concluded that (1) endochondral components contribute most to particularly rapid condylar growth, exceeding the perichondrial component, and (2) endochondral components of condylar growth are regulated by systemic factors that also control somatic growth.

Animals↗

PubMed1993

Onset of human aging estimated from hazard functions associated with various causes of death.

In an attempt to estimate the onset of aging-associated mortality in humans, Swiss national survival and mortality data from 1978 to 1983 were analyzed. The nonparametric kernel method served to estimate gender-specific survival and hazard functions related to five major as well as all causes of death. On the basis of graphical models, it was hypothesized that the onset of aging conceivably was associated with prominent acceleration in mortality rates. The earliest maximal accelerations in hazard functions for most causes of death occurred during the second and again during the fourth age decade. Overall mortality rates of males and females exhibited prominent humps between the two periods of acceleration. These humps were accounted for largely by a high incidence of deaths from violence (accidents, suicide, and crime), which have to be attributed to environmental factors rather than to senescence. On the other hand, no plausible argument could be found against the assumption that maximal acceleration in death rates from ischemic heart and other circulatory diseases around 20 years of age was related to aging. Therefore, these data were interpreted to indicate that in the population examined, senescent mortality sets in around 20 years of age, about 5 years earlier in males than in females. However, when considering overall hazard rates, aging is hidden from view by mortality associated with environmental factors, which predominates up to ages of 30-35 years in both genders.

Adult↗

PubMed1993

Articular degeneration and remodeling in human temporomandibular joints with normal and abnormal disc position.

Temporomandibular joints with normal and abnormal disc positions, obtained from 15 females and 38 males (most between 15 and 50 years of age), were examined under a light microscope. Histologic changes attributed to degeneration and remodeling of the articular tissues were graded according to their prominence and extension along the articular surfaces. These changes seemed little affected by internal derangement in the condyle and the temporal component. In contrast, degeneration and regressive remodeling of the disc and, although to a much lesser degree, its attachments were more severe and increased more steeply with age in internally deranged as compared to normal joints. The present findings suggest that the disc indeed suffers from an abnormal position. However, this conclusion seems tenable only for adults, as rather prominent progressive remodeling changes have been observed in joints from adolescents, but no significant degenerative variations were noted.

Adolescent↗

PubMed1993

Histometric study of synovial cavity dimensions of human temporomandibular joints with normal and anterior disc position.

To evaluate effects of internal derangement, the sagittal lengths of the condylar, temporal, and disc articular surfaces, as well as those of the disc attachments, were measured in histologic sections of human temporomandibular joints obtained at autopsy, mainly from adolescent, young adult, and middle-aged subjects. While the upper joint compartment appeared little affected, anterior disc position was significantly associated with comparatively long inferior disc attachments and a short condylar articular surface, indicative of possibly aberrant insertions of the attachments. Such discrepancies in size or alignment between condyle and disc complex could primarily reflect a constitutional deviation or result secondarily from remodeling.

Adolescent↗

PubMed1992

Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar calcified cartilage.

In an attempt to show maturational alterations in the calcified cartilage, mandibular condyles of four growing and four adult male monkeys (Macaca fascicularis) were studied using light microscopy as well as transmission and scanning electron microscopy. All specimens were initially fixed by perfusion in the presence of ruthenium red. For examination of the hard tissue surfaces in the scanning electron microscope, uncalcified tissues were removed with sodium hypochlorite. In growing animals, almost the entire hard tissue surface in the joint region of the condyle was formed by calcified cartilage, while in adult animals, calcified cartilage was confined to load-bearing regions. In growing animals, the appearance of the calcified cartilage surface suggested a continuously advancing mineralizing front similar to that seen in the epiphyseal plate. Chondrocytes mostly exhibited a terminal stage of hypertrophy, and seemed to die and get lost through vascular invasion and subsequent endochondral ossification. In adult animals, most of the calcified cartilage surface appeared comparatively stable, and resembled the tidemark of articular cartilage. Chondrocytes were usually small and appeared viable. However, on the adult condyles, there were always circumscribed islands where chondrocytes and the pattern of mineralization resembled those seen in growing animals. In these regions, prominent chondroclastic activity indicated extensive articular remodelling. These observations suggest that at the end of somatic growth, condylar calcified cartilage undergoes considerable maturation from a type reminiscent of hyaline growth cartilage to a type resembling articular cartilage. Concomitantly, chondrocytes appear to change their developmental program, in that they stop enlarging and lose their commitment to death. However, they may be able to retain, or switch back to, a more immature stage, in case there is need for extensive articular remodelling.

Animals↗

PubMed1992

Number and size-spectra of myelinated nerve fibers of human premolars.

The primary objective of this study was to determine the number and size of myelinated nerve fibers at the subcervical, midroot and juxta-apical levels of human premolars. Sixty-seven healthy premolars extracted from adolescents were utilized. Root-discs were prepared from the three sites and processed for light and electron microscopy. The myelinated nerve fibers were counted from semithin sections using a sampling microscope. The measurements were taken from composite electron micrographs using an electronic image processing unit. A total of 1883 myelinated axons from seven mandibular second premolars was gauged. The 67 teeth had an average of 312 +/- 149 myelinated nerve fibers at the juxta-apical level (range 18 to 728). The contra- and ipsilateral differences in means among the four groups of premolars were not significant (P > 0.05). The number of nerves increased significantly (P < 0.05) toward midroot and subcervical (P < 0.001) levels in all groups. The average neural diameter was 3.5 + 1.0 microns at the juxta-apical level, and the between-teeth difference in mean was found to be significant (P < 0.01). There was no decline (P > 0.05) in the diameter of myelinated nerve fibers toward midroot and subcervical levels.

Adolescent↗

PubMed1992

Morphological and labeling evidence supporting and extending a modern theory of tooth eruption.

As the interest in biological mechanisms of tooth eruption has recently been revived by a new eruption theory, the present study was an attempt to contribute new data to this problem. Four male Macaca fascicularis monkeys, two infant (about 13 months old) and two juvenile (about 44 months old), were labeled either by sequential fluorochrome or by single 3H-proline injections and then served for studying the bone apposition patterns around erupting premolars and molars. About 100 microns thick ground sections cut either in the mesiodistal or bucco-oral direction and the corresponding micrographs, microradiographs and autoradiographs, as well as fluorescence micrographs were used. In the multirooted teeth studied, bone apposition was most prominent and fast in the inter-radicular region, while at the fundus of the alveoli, bone apposition was slight or negligible. Around maxillary premolars and molars, bone apposition pointed in the mesial as well as in the axial direction. This was true for the intraosseous and the supraosseous phase of tooth eruption. Using these observations in addition to preliminary data calculated for the rates of bone apposition in the inter-radicular, apical and crestal regions, and for the rate of root elongation, the new eruption hypothesis could be extended. It is suggested that eruption of multirooted teeth, in the presence of corresponding coronal resorption, is entirely explained by forces generated through inter-radicular bone apposition and that their dental follicle is in a stimulating mode inter-radicularly but neutral apically at the bottom of the alveolar fundus.

Animals↗

PubMed1991

Changes in cells's secretory organelles and extracellular matrix during endochondral ossification in the mandibular condyle of the growing rat.

The mandibular condyle from 20-day-old rats was examined in the electron microscope with particular attention to intracellular secretory granules and extracellular matrix. Moreover, type II collagen was localized by an immunoperoxidase method. The condyle has been divided into five layers: (1) the most superficial, articular layer, (2) polymorphic cell layer, (3) flattened cell layer, (4) upper hypertrophic, and (5) lower hypertrophic cell layers. In the articular layer, the cells seldom divide, but in the polymorphic layer and upper part of the flattened cell layer, mitosis gives rise to new cells. In these layers, cells produce two types of secretory granules, usually in distinct stacks of the Golgi apparatus; type a, cylindrical granules, in which 300-nm-long threads are packed in bundles which appear "lucent" after formaldehyde fixation; and type b, spherical granules loaded with short, dotted filaments. The matrix is composed of thick banded "lucent" fibrils in a loose feltwork of short, dotted filaments. The cells arising from mitosis undergo endochondral differentiation, which begins in the lower part of the flattened cell layer and is completed in the upper hypertrophic cell layer; it is followed by gradual cell degeneration in the lower hypertrophic cell layer. The cells produce two main types of secretory granules: type b as above; and type c, ovoid granules containing 300-nm-long threads associated with short, dotted filaments. A possibly different secretory granule, type d, dense and cigar-shaped, is also produced. The matrix is composed of thin banded fibrils in a dense feltwork. In the matrix of the superficial layers, the "lucency" of the fibrils indicated that they were composed of collagen I, whereas the "lucency" of the cylindrical secretory granules suggested that they transported collagen I precursors to the matrix. Moreover, the use of ruthenium red indicated that the feltwork was composed of proteoglycan; the dotted filaments packed in spherical granules were similar to, and presumably the source of, the matrix feltwork. The superficial layers did not contain collagen II and were collectively referred to as perichondrium. In the deep layers, the ovoid secretory granules displayed collagen II antigenicity and were likely to transport precursors of this collagen to the matrix, where it appeared in the thin banded fibrils. That these granules also carried proteoglycan to the matrix was suggested by their content of short dotted filaments. Thus the deep layers contained collagen II and proteoglycan as in cartilage; they were collectively referred to as the hyaline cartilage region.

Actin Cytoskeleton↗

PubMed1991

Cartilage matrix production and chondrocyte enlargement as contributors to mandibular condylar growth in monkeys (Macaca fascicularis).

In an attempt to determine the contributions to condylar growth of cartilaginous matrix production and chondrocyte enlargement, four prepubertal male monkeys (Macaca fascicularis) were used. Each animal received 1 mCi 3H-proline per kilogram of body weight 24 hours before death. From the left condyles, the anterior and central segments of the growth cartilage in the lateral and medial joint region were examined with the light microscope. Volumes of cells and extracellular matrix, as well as the intensity of radioautographic labeling, were estimated stereologically in four layers from the articular surface to the zone of endochondral ossification. On the assumption of a steady-state system, these data led to the conclusion that an average chondrocyte in the anterior segment of the growth cartilage contributed to condylar growth by about 3000 microns 3 of newly formed matrix and about 1000 microns 3 of increased cell size. The respective estimates in the central segment were about 3700 microns 3 and 2000 microns 3. Thus, unlike findings in the condylar cartilage of 20-day-old rats, matrix production in the simian condyle exceeded chondrocyte enlargement, although in varying ratios of about 3:1 anteriorly and 1.85:1 centrally. On the other hand, chondrocyte enlargement from the anterior segment to the central segment increased by about 100%, while the increase of about 25% in matrix production was outweighed by variation between individual animals. These findings suggest that the relative contribution of the two growth components varies considerably, on the one hand, with the species or possibly with the stage of condylar development examined and, on the other hand, between various anteroposterior locations within the condylar cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Wall architecture and disc attachment of the human temporomandibular joint.

In an attempt to evaluate the potential behaviour of the temporomandibular joint wall during mandibular movements, joint specimens of 18 individuals, ranging in age from 15-45 years, were examined macroscopically and in the light microscope. The inner part of the joint wall was consistently formed by the superior and inferior lamina of the disc attachment. A distinct fibrous capsule existed in the posterior and lateral joint region, while anteriorly and medially, it could hardly be identified. The posterior attachment to the temporal bone of both the disc and capsule was clearly anterior to the squamotympanic and petrosquamosal fissure. A collagenous sheet inserting in and around these fissure was considered the deep lamina of the parotid-masseteric fascia. With reference to collagen arrangement, content in elastic fibres, and type of synovial lining, the postero-superior disc attachment appeared to be highly extensible, although not elastic enough to effectively pull the disc back upon posterior movements of the condyle. On the other hand, the latero-inferior disc attachment gave the impression of a rigid band well suited to drag the disc along with the condyle and still allowing condylar rotation. In addition, however, the postero-inferior disc attachment in combination with condylar rotation might also contribute effectively to the control of disc position on the moving condyle.

Adolescent↗

PubMed1990

Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar articular layer.

In an attempt to establish maturational alterations in the morphology of the articular tissue layer, mandibular condyles of four immature and four mature male monkeys (Macaca fascicularis) were studied using light microscopy as well as scanning and transmission electron microscopy. Specimens were fixed in situ by perfusion in the presence of ruthenium red to stabilize proteoglycans. Preparations intended for observation in the scanning electron microscope were first dehydrated and sputtered for the examination of articular surfaces, and afterwards treated with trypsin to expose the spatial arrangement of collagen fibrils. Gross anatomical relations between joint components indicated that the anterior and central, but not the posterior region of the condylar articular surface can be subject to compressional load. Load-bearing and non-load-bearing regions differed with respect to the morphology of the articular layer. Load-bearing surfaces were covered by a prominent articular surface lamina similar to that observed on articular cartilage. This lamina seemed to constitute an integral part of the articular layer, distinct from the lining of synovial fluid, and to be composed largely of proteoglycans. It was unaffected by maturation. The subjacent, load-bearing articular layer differed markedly in structure, both from articular cartilage, and between immature and mature animals. Articular cells of immature animals were classified as fibroblastlike, but unlike typical fibroblasts, were surrounded by a thin, often incomplete halo of fibril-free pericellular matrix, presumably consisting of proteoglycans. In mature animals, articular cells closely resembled chondrocytes, but exhibited prominent nuclear fibrous laminae, which usually are found only in fibroblasts. Thus, the load-bearing part of the articular layer seems to undergo a maturation-dependent metaplastic conversion, from a dense connective tissue with some features of fibrocartilage, to a fibrocartilage-like tissue containing chondrocyte-like cells with some features of fibroblasts. This conversion might reflect an adaptation to a maturation-associated increase in articular stress.

Animals↗