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Journal ArticleDOI

Pushing the limit: masticatory stress and adaptive plasticity in mammalian craniomandibular joints

TL;DR: It is argued that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures.
Abstract: Excessive, repetitive and altered loading have been implicated in the initiation of a series of soft- and hard-tissue responses or ;functional adaptations' of masticatory and locomotor elements. Such adaptive plasticity in tissue types appears designed to maintain a sufficient safety factor, and thus the integrity of given element or system, for a predominant loading environment(s). Employing a mammalian species for which considerable in vivo data on masticatory behaviors are available, genetically similar domestic white rabbits were raised on diets of different mechanical properties so as to develop an experimental model of joint function in a normal range of physiological loads. These integrative experiments are used to unravel the dynamic inter-relationships among mechanical loading, tissue adaptive plasticity, norms of reaction and performance in two cranial joint systems: the mandibular symphysis and temporomandibular joint (TMJ). Here, we argue that a critical component of current and future research on adaptive plasticity in the skull, and especially cranial joints, should employ a multifaceted characterization of a functional system, one that incorporates data on myriad tissues so as to evaluate the role of altered load versus differential tissue response on the anatomical, cellular and molecular processes that contribute to the strength of such composite structures. Our study also suggests that the short-term duration of earlier analyses of cranial joint tissues may offer a limited notion of the complex process of developmental plasticity, especially as it relates to the effects of long-term variation in mechanical loads, when a joint is increasingly characterized by adaptive and degradative changes in tissue structure and composition. Indeed, it is likely that a component of the adaptive increases in rabbit TMJ and symphyseal proportions and biomineralization represent a compensatory mechanism to cartilage degradation that serves to maintain the overall functional integrity of each joint system. Therefore, while variation in cranial joint anatomy and performance among sister taxa is, in part, an epiphenomenon of interspecific differences in diet-induced masticatory stresses characterizing the individual ontogenies of the members of a species, this behavioral signal may be increasingly mitigated in over-loaded and perhaps older organisms by the interplay between adaptive and degradative tissue responses.

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TL;DR: In this article, the authors highlight recent advances in X-ray microcomputed tomography (microCT) as applied to materials, specifically advances made since the first materials microCT review appeared in Internati...
Abstract: This review highlights recent advances in X-ray microcomputed tomography (microCT) as applied to materials, specifically advances made since the first materials microCT review appeared in Internati...

470 citations

Journal ArticleDOI
TL;DR: Novel findings in biomedicine and developments in imaging and computer technologies are beginning to provide a vision of future innovations in the diagnostics and therapeutics of TMJ disorders, and the identification and use of local or systemic biomarkers to diagnose disease or monitor improvements in therapy.
Abstract: Because their etiologies and pathogenesis are poorly understood, temporomandibular joint (TMJ) diseases are difficult to diagnose and manage. All current approaches to treatments of TMJ diseases are largely palliative. Definitive and rational diagnoses or treatments can only be achieved through a comprehensive understanding of the etiologies, predisposing factors, and pathogenesis of TMJ diseases. While much work remains to be done in this field, novel findings in biomedicine and developments in imaging and computer technologies are beginning to provide us with a vision of future innovations in the diagnostics and therapeutics of TMJ disorders. These advances include the identification and use of local or systemic biomarkers to diagnose disease or monitor improvements in therapy; the use of imaging technologies for earlier and more sensitive diagnostics; and the use of biomedicine, biomimetics, and imaging to design and manufacture bioengineered joints. Such advances are likely to help to customize and enhance the quality of care we provide to patients with TMJ disorders.

218 citations

Journal Article
TL;DR: The data suggest that myostatin has direct effects on the proliferation and differentiation of osteoprogenitor cells, and that hisostatin antagonists and inhibitors are likely to enhance both muscle mass and bone strength.
Abstract: Myostatin (GDF-8) is a member of the transforming growth factor-beta (TGF-β) superfamily that is highly expressed in skeletal muscle, and myostatin loss-of-function leads to doubling of skeletal muscle mass. Myostatin-deficient mice have been used as a model for studying muscle-bone interactions, and here we review the skeletal phenotype associated with altered myostatin signaling. It is now known that myostatin is a key regulator of mesenchymal stem cell proliferation and differentiation, and mice lacking the myostatin gene show decreased body fat and a generalized increase in bone density and strength. The increase in bone density is observed in most anatomical regions, including the limbs, spine, and jaw, and myostatin inhibitors have been observed to significantly increase bone formation. Myostatin is also expressed in the early phases of fracture healing, and myostatin deficiency leads to increased fracture callus size and strength. Together, these data suggest that myostatin has direct effects on the proliferation and differentiation of osteoprogenitor cells, and that myostatin antagonists and inhibitors are likely to enhance both muscle mass and bone strength.

195 citations

Journal ArticleDOI
TL;DR: The osteological correlates and inferred soft tissue anatomy of the jaw muscles and relevant neurovasculature in the temporal region of the dinosaur head are presented to provide the anatomical foundation necessary for future analyses of skull function and evolution in an important vertebrate clade.
Abstract: Jaw muscles are key components of the head and critical to testing hypotheses of soft-tissue homology, skull function, and evolution. Dinosaurs evolved an extraordinary diversity of cranial forms adapted to a variety of feeding behaviors. However, disparate evolutionary transformations in head shape and function among dinosaurs and their living relatives, birds and crocodylians, impair straightforward reconstructions of muscles, and other important cephalic soft tissues. This study presents the osteological correlates and inferred soft tissue anatomy of the jaw muscles and relevant neurovasculature in the temporal region of the dinosaur head. Hypotheses of jaw muscle homology were tested across a broad range archosaur and sauropsid taxa to more accurately infer muscle attachments in the adductor chambers of non-avian dinosaurs. Many dinosaurs likely possessed m. levator pterygoideus, a trait shared with lepidosaurs but not extant archosaurs. Several major clades of dinosaurs (e.g., Ornithopoda, Ceratopsidae, Sauropoda) eliminated the epipterygoid, thus impacting interpretations of m. pseudotemporalis profundus. M. pseudotemporalis superficialis most likely attached to the caudoventral surface of the laterosphenoid, a trait shared with extant archosaurs. Although mm. adductor mandibulae externus profundus and medialis likely attached to the caudal half of the dorsotemporal fossa and coronoid process, clear osteological correlates separating the individual bellies are rare. Most dinosaur clades possess osteological correlates indicative of a pterygoideus ventralis muscle that attaches to the lateral surface of the mandible, although the muscle may have extended as far as the jugal in some taxa (e.g., hadrosaurs, tyrannosaurs). The cranial and mandibular attachments of mm adductor mandibulae externus superficialis and adductor mandibulae posterior were consistent across all taxa studied. These new data greatly increase the interpretive resolution of head anatomy in dinosaurs and provide the anatomical foundation necessary for future analyses of skull function and evolution in an important vertebrate clade.

148 citations


Cites background from "Pushing the limit: masticatory stre..."

  • ...Finally, feeding behavior and connective tissue adaptive plasticity are major factors involved in the structure and function of jaw muscles and the skull (Ravosa et al., 2007)....

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References
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Journal ArticleDOI
TL;DR: 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, interpreted to suggest that unilateral bite raise leads to the magnitude of compressive forces in the rat temporomandibular joint.
Abstract: 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.

103 citations


"Pushing the limit: masticatory stre..." refers background in this paper

  • ...In addition, altering TMJ force application by varying masticatory loading regime, tooth extraction, unilateral bite raise or corticotomy has been shown to result in gene expression changes and elevated glycosaminoglycan (GAG) content in condylar cartilage (Copray et al., 1985; Carvalho et al., 1995; Holmvall et al., 1995; Pirttiniemi et al., 1996; Mao et al., 1998; Agarwal et al., 2001; Huang et al., 2002; Huang et al., 2003)....

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  • ...…has been shown to result in gene expression changes and elevated glycosaminoglycan (GAG) content in condylar cartilage (Copray et al., 1985; Carvalho et al., 1995; Holmvall et al., 1995; Pirttiniemi et al., 1996; Mao et al., 1998; Agarwal et al., 2001; Huang et al., 2002; Huang et al., 2003)....

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Journal ArticleDOI
TL;DR: By the age of 3 years, young mountain gorillas have developed the basic dietary patterns of adults, in terms of the number of foods eaten, the proportions in which specific foods are consumed, and diet diversity and equitability.
Abstract: This report describes observations on the ontogeny of food choice in mountain gorillas (Gorilla gorilla beringei), made during a 17-month field study of mountain gorilla feeding ecology in the Parc National des Volcans, Rwanda. Data are presented on the feeding behavior of two infants observed from birth to the age of 8 months and on older infants and juveniles. This information is compared with data on the composition and diversity of the diets of young adults and adults in the same social group. Initial feeding by infants is usually synchronized with the mother's behavior: infants ingest the same food, or a different part of the same plant species, currently being eaten by the mother or just eaten by her. This suggests that observational learning is largely responsible for the transmission of food preferences. Most feeding by young infants, whether or not synchronized with the mother's, is on those foods eaten most frequently by adults. Infants also independently sample potential foods, some of which are apparently not consumed by adults. The frequency of sampling declines with age, although even adults occasionally ingest foods not observed to be eaten by other adults. By the age of 3 years, young mountain gorillas have developed the basic dietary patterns of adults, in terms of the number of foods eaten, the proportions in which specific foods are consumed, and diet diversity and equitability. There is a strong possibility that chemical cues influence food choice, but their role remains unclear.

103 citations


"Pushing the limit: masticatory stre..." refers background in this paper

  • ...Once weaned, mammals ingest ‘adult’ food items (e.g. Watts, 1985; Tarnaud, 2004) and develop ‘adult’ jaw-adductor activity patterns (Herring and Wineski, 1986; Weijs et al., 1987; Herring et al., 1991; Iinuma et al., 1991; Langenbach et al., 1991; Langenbach et al., 1992; Langenbach et al., 2001;…...

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Journal ArticleDOI
TL;DR: The collagen-binding integrins alpha 1 beta 1 and alpha 2 beta 1 isolated from bovine chondrocytes or human chondrosarcoma cells bound collagen type II as judged from affinity chromatography, and the effect of mechanical stress on expression of matrix molecules and integrin subunits was investigated.

102 citations


"Pushing the limit: masticatory stre..." refers background in this paper

  • ...In addition, altering TMJ force application by varying masticatory loading regime, tooth extraction, unilateral bite raise or corticotomy has been shown to result in gene expression changes and elevated glycosaminoglycan (GAG) content in condylar cartilage (Copray et al., 1985; Carvalho et al., 1995; Holmvall et al., 1995; Pirttiniemi et al., 1996; Mao et al., 1998; Agarwal et al., 2001; Huang et al., 2002; Huang et al., 2003)....

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  • ...…has been shown to result in gene expression changes and elevated glycosaminoglycan (GAG) content in condylar cartilage (Copray et al., 1985; Carvalho et al., 1995; Holmvall et al., 1995; Pirttiniemi et al., 1996; Mao et al., 1998; Agarwal et al., 2001; Huang et al., 2002; Huang et al., 2003)....

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Journal ArticleDOI
TL;DR: Observed phenomena suggest that during development the possibilities for generation of large bite forces are increased at the cost of a restriction of the range of jaw excursion.
Abstract: Between weaning and adulthood, the length and height of the facial skull of the New Zealand rabbit (Oryctolagus cuniculus) double, whereas much less growth occurs in the width of the face and in the neurocranium. There is a five-fold increase in mass of the masticatory muscles, caused mainly by growth in cross-sectional area. The share of the superficial masseter in the total mass increases at the cost of the jaw openers. There are changes in the direction of the working lines of a few muscles. A 3-dimensional mechanical model was used to predict bite forces at different mandibular positions. It shows that young rabbits are able to generate large bite forces at a wider range of mandibular positions than adults and that the forces are directed more vertically. In young and adult animals, the masticatory muscles differ from each other with respect to the degree of gape at which optimum sarcomere length is reached. Consequently, bite force can be maintained over a range of gapes, larger than predicted on basis of individual length-tension curves. Despite the considerable changes in skull shape and concurrent changes in the jaw muscles, the direction of the resultant force of the closing muscles and its mechanical advantage remain stable during growth. Observed phenomena suggest that during development the possibilities for generation of large bite forces are increased at the cost of a restriction of the range of jaw excursion.

99 citations


"Pushing the limit: masticatory stre..." refers background in this paper

  • ...…and reaction forces are elevated during the processing of relatively tough and/or resistant foods (Herring and Scapino, 1973; Thexton et al., 1980; Weijs et al., 1987; Weijs et al., 1989; Gans et al., 1990; Dessem and Druzinsky, 1992; Hylander et al., 1992; Hylander et al., 1998; Hylander et al.,…...

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  • ...…mammals ingest ‘adult’ food items (e.g. Watts, 1985; Tarnaud, 2004) and develop ‘adult’ jaw-adductor activity patterns (Herring and Wineski, 1986; Weijs et al., 1987; Herring et al., 1991; Iinuma et al., 1991; Langenbach et al., 1991; Langenbach et al., 1992; Langenbach et al., 2001;…...

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  • ...…muscle activity, jaw-kinematic and jaw-loading patterns, masticatory function during ontogeny, and the link between masticatory behaviors and diet (Weijs et al., 1987; Weijs et al., 1989; Langenbach et al., 1991; Langenbach et al., 1992; Langenbach et al., 2001; Langenbach and van Eijden, 2001)....

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Journal ArticleDOI
TL;DR: Immunohistochemical staining of sagittal sections of the disc showed chondroitin sulphate to be distributed throughout, whereas dermatan sulphate (as proteodermatan sulphates) appeared to be concentrated in the periphery.

99 citations


"Pushing the limit: masticatory stre..." refers background in this paper

  • ..., 1988; Goldring, 2004a; Goldring, 2004b), with expression of cartilage ECM elements likely reflecting regional variation due to differential loading patterns in distinct joint regions (Bayliss et al., 1983; Nakano and Scott, 1989; Mow et al., 1990; Hamrick, 1999; Tanaka et al., 2000)....

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  • ...…et al., 1988; Goldring, 2004a; Goldring, 2004b), with expression of cartilage ECM elements likely reflecting regional variation due to differential loading patterns in distinct joint regions (Bayliss et al., 1983; Nakano and Scott, 1989; Mow et al., 1990; Hamrick, 1999; Tanaka et al., 2000)....

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