Modulation of force during mammalian mastication provides insight into force modulation in rhythmic, cyclic behaviors. This study uses in vivo bone strain data from the mandibular corpus to test two hypotheses regarding bite force... more
Modulation of force during mammalian mastication provides insight into force modulation in rhythmic, cyclic behaviors. This study uses in vivo bone strain data from the mandibular corpus to test two hypotheses regarding bite force modulation during rhythmic mastication in mammals: (1) that bite force is modulated by varying the duration of force production, or (2) that bite force is modulated by varying the rate at which force is produced. The data sample consists of rosette strain data from 40 experiments on 11 species of mammals, including six primate genera and four nonprimate species: goats, pigs, horses and alpacas. Bivariate correlation and multiple regression methods are used to assess relationships between maximum (epsilon(1)) and minimum (epsilon(2)) principal strain magnitudes and the following variables: loading time and mean loading rate from 5% of peak to peak strain, unloading time and mean unloading rate from peak to 5% of peak strain, chew cycle duration, and chew du...
Research Interests: Mathematics, Agriculture, Medicine, Masticatory Biomechanics, Mammals, and 15 moreBiological Sciences, Bite force, Animals, Regression Analysis, Mandible, Chewing, Multiple Regression, Cycle Time, Bone Strain, Rhythmicity, Mastication, Food Consistency, Experimental Biology, Biomechanical Phenomena, and Medical and Health Sciences
Research Interests:
Synthesis of Physiologic Data from the Mammalian Feeding Apparatus Using FEED, the Feeding Experiments End-User Database Organized by Susan H. Williams, Christine E. Wall, Rebecca Z. German and Christopher J. Vinyard ... 215 Overview of... more
Synthesis of Physiologic Data from the Mammalian Feeding Apparatus Using FEED, the Feeding Experiments End-User Database Organized by Susan H. Williams, Christine E. Wall, Rebecca Z. German and Christopher J. Vinyard ... 215 Overview of FEED, the Feeding Experiments End-user Database Christine E.Wall, Christopher J.Vinyard, Susan H.Williams,Vladimir Gapeyev, Xianhua Liu, Hilmar Lapp and Rebecca Z. German 224 Mammalian Masticatory Muscles: Homology, Nomenclature, and Diversification Robert E. Druzinsky, Alison H. ...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Current craniofacial growth modification devices use static forces, but cyclic forces are believed by some to be more effective. The latter have not been evaluated in large animal models, and it is not known how such forces are... more
Current craniofacial growth modification devices use static forces, but cyclic forces are believed by some to be more effective. The latter have not been evaluated in large animal models, and it is not known how such forces are transmitted to distant parts of the skull. In this study, we aimed to (1) develop a portable loading system capable of delivering reliable cyclic loads to the porcine nasofrontal suture (NFS), (2) explore strain transmission to distant sutures, and (3) characterize the sutural growth effects in a small pilot study. After we validated the device, cyclic (2.5 Hz) tensile loads were applied unilaterally to the NFS of 6 abattoir pig heads, with strain gauges on multiple sutures. Similar loading was applied to 3-month-old live pigs (Sus scrofa, n = 4 and 1 sham) 30 minutes per day for 5 days. These animals received fluorescent markers of mineralization on loading days 1 and 3. Suture strains were recorded on day 5. Histomorphometric analysis quantified suture widt...
Research Interests:
In addition to conveying the forces of attaching muscles and ligaments to the zygomatic and temporal bones, the arch periosteum is responsible for lateral apposition and medial resorption during the growth period. In this contribution, we... more
In addition to conveying the forces of attaching muscles and ligaments to the zygomatic and temporal bones, the arch periosteum is responsible for lateral apposition and medial resorption during the growth period. In this contribution, we describe the vasculature of the zygomatic arch in young pigs (Sus scrofa dom.) in order to understand the relationship of osseous and periosteal vessels to each other, to surrounding tissues, and to patterns of modeling. Subjects 2-6 weeks of age were perfused with vascular fill; some also received the vital bone label calcein. Whole mounts were prepared of the decalcified bony arch and of its lateral periosteum. Undecalcified arches were plastic-embedded and thick-sectioned. Additional observations on cell replication were made using material from a previous study. The osseous and periosteal vascular supplies were largely independent, joined only by a fine network at the tissue interface. Osseous vessels entered the medial side of the arch through clusters of nutrient foramina. The intraosseous branching pattern resembled the direction of appositional growth, which in turn describes the disposition of bony trabeculae in older pigs. In contrast, vessels arrived at the periosteum via muscles and ligaments and thus its perfusion may partially depend on functional activity. The open weave of periosteal vessels bore little similarity to bone architecture, especially for the temporal bone, but the appositional lateral periosteum showed indications of angiogenesis, whereas the thinner, resorptive periosteum on the medial side featured composite, possibly fusing vessels at the bone surface. Anat Rec, 299:1661-1670, 2016. © 2016 Wiley Periodicals, Inc.
Research Interests:
Research Interests:
Page 1. Vol. 108, No. 962 The American Naturalist July-August 1974 THE SUPERFICIAL MASSETER AND GAPE IN M MLS SUSAN W. HERRING AND STEPHEN E. HERRING Department of Oral Anatomy, University of Illinois at the Medical Center, Chicago,... more
Page 1. Vol. 108, No. 962 The American Naturalist July-August 1974 THE SUPERFICIAL MASSETER AND GAPE IN M MLS SUSAN W. HERRING AND STEPHEN E. HERRING Department of Oral Anatomy, University of Illinois at the Medical Center, Chicago, Illinois 60612 ...
Research Interests:
... condyle reflects the decreased vertical load and perhaps also generally lower muscle activity during grinding. ... Presumably, warthogs and giant forest hogs use the same contraction pattern as Sus for producing ...... more
... condyle reflects the decreased vertical load and perhaps also generally lower muscle activity during grinding. ... Presumably, warthogs and giant forest hogs use the same contraction pattern as Sus for producing ... HERRING-MASTICATORY PATTERNS IN PECCARIES AND PIGS ...
Research Interests:
The periosteum is anatomically and functionally divided into two layers. The inner osteoblastic layer contributes to local appositional bone growth. The outer fibroblastic layer receives the attachments of muscles and responds to bone... more
The periosteum is anatomically and functionally divided into two layers. The inner osteoblastic layer contributes to local appositional bone growth. The outer fibroblastic layer receives the attachments of muscles and responds to bone growth by a more global enlargement. Coordinated growth of the layers could theoretically be produced by parallel replication rates in the layers followed by migration of fibroblastic layer cells. Alternatively, replication rates in the layers could differ, those in the osteoblastic layer reflecting local apposition and those in the fibroblastic layer responding to total bone growth. To test these alternatives, we compared two regions of the pig mandible, one appositional and one resorptive, equidistant from the major growth sites of the bone. Four 2-week-old pigs were injected i.p. with 5-bromo-2'-deoxyuridine (BrdU) to label replicating cells. Three hours subsequent to BrdU injection, animals were sacrificed. The mandibles were sectioned and processed immunocytochemically for BrdU. Periosteal cell mitotic activity was analyzed selectively at the level of the mandibular foramen on the medial and lateral ramal surfaces. The proportion of labeled cells was determined by grid-point analysis. Individual differences were minor but regional differences were striking. As expected, the osteoblastic layer of the lateral surface exhibited a greater proportion of mitotic cells than did the medial surface (p = 0.037). However, no such difference was seen in the fibroblastic layer, where medial and lateral sides exhibited identical replication activity. These results strongly support the second alternative, that cell division is differentially controlled in the two periosteal layers.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
An animal study of functional biomechanics was undertaken to understand normal loading of the temporomandibular joint (TMJ) and to provide insight into the pathogenesis of TMJ disorders. Bone strain and ligamentous deformation were... more
An animal study of functional biomechanics was undertaken to understand normal loading of the temporomandibular joint (TMJ) and to provide insight into the pathogenesis of TMJ disorders. Bone strain and ligamentous deformation were measured during mastication in 26 10-month-old minipigs. Half the subjects had undergone a surgical disruption of the left lateral capsular and disc attachments to the condyle 5 to 6 weeks previously. Rosette strain gauges were bonded to the left lateral surfaces of the squamosal bone near the TMJ, the condylar neck, and the mandibular corpus below the molar region. Differential variable reluctance transducers (DVRTs) were placed bilaterally in the lateral capsular tissue of the joints. Bone strains, ligamentous deformations, and the electromyographic activities of the masseters and lateral pterygoids were recorded during natural mastication. In all animals on both working and balancing sides, mastication caused bone strains that were dominated by tension in the squamosal bone site and by compression in the other sites. Measurements from the DVRT revealed elongation of the lateral capsular tissue in the last phase of the power stroke and shortening in the initial phase of opening, which was almost simultaneous with the development of bone strain. Strain in the capsule ranged from 3 to 25%, with the strain of the balancing side exceeding that of the working side. The surgical disruption did not alter chewing side preference or bone strain, but a tendency toward more extensive ligamentous deformation on the intact side was observed. Furthermore, the ratio of masseter to lateral pterygoid activity was smaller on the disrupted side and larger on the intact side, in comparison to control pigs. Both osseous and ligamentous components of the TMJ are strained during mastication, and the latter are more deformed on the balancing side. Disruption of the lateral attachment had little effect on strain in the osseous components but appeared to increase strain in the capsule and to modify the balance of masticatory muscle activity.
Research Interests:
Research Interests:
Objectives: Paralysis of the masseters using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters, muscle spasm, bruxism, and pain. In a previous study, rabbit masseters injected with BTX functionally... more
Objectives: Paralysis of the masseters using botulinum toxin (BTX) is a common treatment for cosmetic reduction of the masseters, muscle spasm, bruxism, and pain. In a previous study, rabbit masseters injected with BTX functionally recovered, but remained significantly lighter than uninjected muscles 12 weeks after injection. The goal of this study was to understand the effects of BTX on muscle fiber size and tissue composition. Methods: Rabbit masseters were injected unilaterally with BTX and harvested at 4 weeks (n=7) or 12 weeks (n=8) post-injection. Saline controls (n=4) were harvested at 12 weeks. The observer was blinded to treatment. Masseters were paraffin-embedded, cross-sectioned, and stained with trichrome. The least diameters of 120 muscle fibers were averaged per cross-section. Percent tissue composition was determined by superimposing a grid over the entire cross-section and identifying the tissue type at each intersection. Cross-sections were qualitatively observed an...
The skull does not bear body weight, causing speculation that craniofacial bones are not dependent on loading for their maintenance, unlike limb bones. The relative ease of changing alveolar bone using orthodontic forces seems to belie... more
The skull does not bear body weight, causing speculation that craniofacial bones are not dependent on loading for their maintenance, unlike limb bones. The relative ease of changing alveolar bone using orthodontic forces seems to belie this notion, as do experiments modifying sutural and condylar growth using applied loads. Nevertheless, these may be special cases involving periosteum/periodontium surfaces and may not apply to bone density. During normal function, loading of craniofacial bones can only come from contraction of jaw muscles. The force of contraction can be manipulated by changing the consistency of the diet or by selectively paralyzing muscles. These indicate a substantial effect. For example, 1 month after a single dose of botulinum toxin to one masseter of adult rabbits, trabecular bone in the ipsilateral condylar head was reduced by 40%. Craniofacial bones are just as sensitive to loading as are limb bones.
Introduction: Loading history affects periodontal ligament (PDL) and alveolar bone morphology. Previous literature shows that force can increase the complexity of the tooth-bone interface whereas soft diets lead to thinning of the PDL... more
Introduction: Loading history affects periodontal ligament (PDL) and alveolar bone morphology. Previous literature shows that force can increase the complexity of the tooth-bone interface whereas soft diets lead to thinning of the PDL space and disorganization of PDL fibers. Weakening of jaw muscles is a treatment for severe bruxism, and reduction of masticatory muscle mass is an increasingly popular cosmetic treatment; both are achieved with Botox injections to the masseter. Objective: This project investigated where Botox treatment of the masseter affects the PDL. Methods: Rabbits were subjected to four weeks of reduced occlusal loading via a single Botox injection to one masseter. Treated rabbits (n=6) were expected to exhibit decreased collagen amount and decreased PDL-bone interface complexity when compared to saline-injected rabbits with normal bite force (n=5). A reduction in PDL organization marked by fewer distinct bundles and more variation in fiber attachment angle, and t...
Objectives: To study the effects of location, orientation and loading speed on the compressive mechanical properties of porcine nasal septal cartilage. Methods: Porcine nasal septa were extracted from freshly slaughtered specimens (N=23)... more
Objectives: To study the effects of location, orientation and loading speed on the compressive mechanical properties of porcine nasal septal cartilage. Methods: Porcine nasal septa were extracted from freshly slaughtered specimens (N=23) and frozen in phosphate-buffered saline. Specimens were thawed and six samples were cut from each specimen, two vertical (anterior/posterior) and four horizontal (superior/inferior) to the palate at 8mm x 12mm x natural thickness. Samples were mounted between compression platens of an MTS testing machine. Samples were preloaded to 2.5N, and then loaded at a speed of 1 or 0.1%length/second. Each sample was loaded to 5 different strain points (2, 4, 6, 8, and 10% of height) in randomized order. Stress was calculated as load divided by cross-sectional area and stress-strain curves were plotted. Elastic modulus (stiffness) was calculated as the slope of the linear part of the stress-strain curves. Results: Larger strains were consistently associated wit...
Introduction:The nasal septal cartilage (NSC) is thought to be a driving force of midfacial growth. However, it is not clear whether the NSC expands uniformly. Previous reports suggest that interstitial growth and cellular proliferation... more
Introduction:The nasal septal cartilage (NSC) is thought to be a driving force of midfacial growth. However, it is not clear whether the NSC expands uniformly. Previous reports suggest that interstitial growth and cellular proliferation in the NSC varies by region, but results are not consistent. Objectives: To measure the interstitial growth and the cellular proliferation of the NSC in a minipig model to determine: (1) whether the NSC expands uniformly and (2) whether cellular proliferation varies regionally. Methods: Real-time growth of the NSC was measured in vivo for an average of 81±64 hours using pairs of differential variable linear displacement transducers implanted anteriorly and posteriorly in the dorsal part of the NSC (n=9, 4.2±0.4 months). Animals of similar age (n=6, 4.4±1.0 month) were injected with 5’-bromo-2’-deoxyuridine (BrdU) and sacrificed 24 hours later. Proliferation rate (BrdU positive cells/total cells) and cellular density (cells/mm2) in the NSC and attache...
Objective: To evaluate functional loading and bone quality of the mandible following injection of botulinum neurotoxin type A (BoNT/A) in the masseter. Methods: Forty adult female New Zealand white rabbits received injection of either... more
Objective: To evaluate functional loading and bone quality of the mandible following injection of botulinum neurotoxin type A (BoNT/A) in the masseter. Methods: Forty adult female New Zealand white rabbits received injection of either BoNT/A or saline into one masseter muscle. Animals were terminated at 4 and 12 weeks. In a terminal procedure, gages were applied to the condylar necks and the alveolar processes, and strain was recorded during awake feeding. After termination, the muscles of mastication were weighed and bone specimens were scanned with microCT. Results: Saline controls showed no side differences. At 4 weeks the BoNT/A-injected masseter was 18% and the medial pterygoid 10% smaller than the contralateral side (p≤0.001). At 12 weeks, the injected side masseter and medial pterygoid were 7% and 4% smaller, indicating partial recovery. Compressive strain at the condylar neck was re-oriented (p=0.005) and tended to be low on the injected side at 4 weeks but not at 12 weeks. ...
Objective: The 7 serotypes of botulinum toxin vary in effectiveness. This project investigated how botulinum toxin Type-A (BTX/A) and Type-B (BTX/B) differentially affect the physiology and anatomy of the pig masseter muscle(MA). Method:... more
Objective: The 7 serotypes of botulinum toxin vary in effectiveness. This project investigated how botulinum toxin Type-A (BTX/A) and Type-B (BTX/B) differentially affect the physiology and anatomy of the pig masseter muscle(MA). Method: BTX/A (100 units, n=3; 200 units, n=1), BTX/B (5,000 units, n=3), or an equivalent volume of 0.9% saline (n=2) were injected into one randomized MA of minipigs. Surface electromyography (sEMG) of bilateral MAs was recorded during natural mastication before injection (baseline), 48 hours after, then weekly for 4 weeks. Molar bite force (BF) produced by electrical stimulation to injected and non-injected MAs was also tracked. At the end of week 4, strain gages were bonded bilaterally to the condylar neck and alveolar bone, and bone strain was recorded during mastication and masseter stimulation. Upon euthanasia, the muscles were dissected and weighed. Non-parametric and descriptive statistics were used to test the difference between the sides and acro...
Objective: To evaluate masticatory muscle function after paralysis of one masseter using botulinum neurotoxin type A (BoNT/A) and during the course of recovery. Methods: Forty adult female New Zealand rabbits were injected either with... more
Objective: To evaluate masticatory muscle function after paralysis of one masseter using botulinum neurotoxin type A (BoNT/A) and during the course of recovery. Methods: Forty adult female New Zealand rabbits were injected either with BoNT/A (n=20) or saline (n=20) in one masseter. Electromyographic activity (EMG) was recorded during mastication before injection (T1) and 1-2 (T2, n=20), 5-6 (T3, n=20), and 9-11 (T4, n=20) weeks later. Wire electrodes were placed in the anterior, middle, posterior, and deep regions of each masseter, and in the medial pterygoid muscles, and synchronized video images served to identify the chewing side. At each time point, masticatory rhythm and side preference were evaluated, and 30-50 consecutive chewing cycles were analyzed for signal amplitude and onset/offset time for each muscle part. Results: There were no significant differences between BoNT/A and saline animals at any time point in body weight, chewing side preference, or chewing rate. Compare...
Objective: To investigate short- and long-term effects of botulinum toxin Type A (BTX/A) on the neuromuscular responses of the masseter muscle (MA). Method: Of 15 rabbits, 5 were untreated (control), and 10 received 10 units of BTX/A... more
Objective: To investigate short- and long-term effects of botulinum toxin Type A (BTX/A) on the neuromuscular responses of the masseter muscle (MA). Method: Of 15 rabbits, 5 were untreated (control), and 10 received 10 units of BTX/A injected into one MA. The treated rabbits were examined 4 weeks (short-term) or 12 weeks (long-term) after the injection (n=5 each). In random order of uninjected and injected sides, MA nerve trunks were exposed in anesthetized animals and stimulated at threshold intensity (5-6V) at 2Hz. Evoked action potentials (eEMG) were recorded from 11 sites in each injected and non-injected MA via fine-wire electrodes. Ten consecutive eEMG action potentials from each recording were analyzed to calculate integrated amplitude and duration for each site. Differences among control, 4- and 12-week groups and between injected and non-injected MAs were tested non-parametrically. Result: 1) All sites of the BTX-injected MAs had significantly lower eEMG amplitudes than the...
Research Interests:
Like humans, domestic pigs are omnivorous and thus are a common model for human masticatory function. Prior attempts to characterize food–tooth interactions and jaw movements associated with mastication have been limited to aspects of the... more
Like humans, domestic pigs are omnivorous and thus are a common model for human masticatory function. Prior attempts to characterize food–tooth interactions and jaw movements associated with mastication have been limited to aspects of the oral apparatus that are visible externally (with videography) and/or to 2D movements of oral structures (with monoplanar videofluoroscopy). We used XROMM, a 3D technique that combines CT-based morphology with biplanar videofluoroscopy, to quantify mandibular kinematics, tooth occlusion and mandibular condylar displacements within the temporomandibular joint (TMJ) during feeding. We observed that the pig TMJ moved detectably in only three of six possible degrees of freedom during mastication: two rotations, pitch and yaw; and one translation, protraction–retraction. Asymmetrical yaw around a dorsoventral axis produced the observed alternating left–right chewing cycles responsible for food reduction. Furthermore, the relative motions of the upper and...
Research Interests:
Intraoral splints are a commonly used dental treatment for a variety of conditions. Because such splints alter the condyle-disc-fossa relationship, they probably change the loading status of the temporomandibular joint (TMJ), including... more
Intraoral splints are a commonly used dental treatment for a variety of conditions. Because such splints alter the condyle-disc-fossa relationship, they probably change the loading status of the temporomandibular joint (TMJ), including the TMJ disc. Collagen, a major constituent of the disc, acts to resist tensile loading, and it is presumed that the fiber orientations of the individual disc bands reflect their functional loading. Therefore, the purpose of this study was to examine effects of intraoral splint wear on TMJ morphology in general, and collagen orientation of the intra-articular disc in particular. Young adult, female miniature pigs were divided into three groups: open-bite splint, protrusive-bite splint, and unsplinted control. Splints were worn for 2 months, after which the TMJ discs were harvested for histological examination and stereological analysis, and the skulls were cleaned. Although the splints had no effect on skull dimensions, changes were seen in the TMJs. ...
Research Interests:
The mechanical environment is a regulator of growth and adaptation of the musculoskeletal system, including joints. Although pigs (Sus scrofa) are used frequently as models for temporomandibular joint (TMJ) dysfunction, no systematic... more
The mechanical environment is a regulator of growth and adaptation of the musculoskeletal system, including joints. Although pigs (Sus scrofa) are used frequently as models for temporomandibular joint (TMJ) dysfunction, no systematic description of microanatomy exists for this species. We injected the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) into 10- to 11-month-old miniature pigs that were undergoing measurements of TMJ bone strain. Ten hr later, the animals were sacrificed and their heads were perfused. Histological sections were used to map the distribution of replicating cells. Additional observations were made on gross dissections of jaw joints obtained from an abattoir. The pig TMJ is better supported than that of humans laterally and medially, but more vulnerable posteriorly. The posterior attachment area of the intra-articular disc is fibro-fatty rather than vascular, as in humans. Cartilage lines the articular eminence as well as the condylar surface. At the post...
Research Interests:
Many mammalian muscles have a complex internal architecture. This type of structure could allow a single muscle to produce a variety of force vectors through selective regional contractions. This hypothesis was tested... more
Many mammalian muscles have a complex internal architecture. This type of structure could allow a single muscle to produce a variety of force vectors through selective regional contractions. This hypothesis was tested electromyographically in the multipinnate pig masseter by recording simultaneously from several intramuscular sites. It was found that the activity in different portions of the masseter varied systematically during the various phases of mastication. anatomical correlates of the differential activity included fasciculus orientation and length, sarcomere length in specific jaw positions, and histochemical fiber type. The usual assumptions made about muscles for biomechanical analysis, such as uniform contraction and constant line of action, are inappropriate for complex muscles such as the pig masseter.
Research Interests:
The purpose of this study was to investigate the effects of reduced masticatory function on midline suture growth and morphology in growing pigs. The sample was 20 pigs separated into two dietary groups and raised at the Department of... more
The purpose of this study was to investigate the effects of reduced masticatory function on midline suture growth and morphology in growing pigs. The sample was 20 pigs separated into two dietary groups and raised at the Department of Anthropology, Harvard University. Midline suture specimens were analyzed at the Department of Orthodontics, University of Washington. Ten farm pigs and 10 minipigs, all male, were randomly assigned to hard (n = 9) and soft-diet (n = 11) groups. Fluorochromic mineral labels were administered to document bone apposition, and the animals were killed after 12 weeks. Undecalcified sections of the interfrontal, interparietal, internasal, and intermaxillary sutures were evaluated for bone quantity and sutural thickness, interdigitation ratio and growth rate. Soft-diet pigs were characterized by a slower rate of weight gain and less bone than their hard-diet counterparts. Even after correction for weight gain, soft-diet pigs had reduced suture growth rate and ...
Research Interests:
In addition to their role in skull growth, sutures are sites of flexibility between the more rigid bones. Depending on the suture, predominant loading during life may be either tensile or compressive. Loads are transmitted across sutures... more
In addition to their role in skull growth, sutures are sites of flexibility between the more rigid bones. Depending on the suture, predominant loading during life may be either tensile or compressive. Loads are transmitted across sutures via collagenous fibers and a fluid-rich extracellular matrix and can be quasi-static (growth of neighboring tissues) or intermittent (mastication). The mechanical properties of sutures, while always viscoelastic, are therefore quite different for tensile versus compressive loading. The morphology of individual sutures reflects the nature of local loading, evidently by a process of developmental adaptation. In vivo or ex vivo, sutural cells respond to tensile or cyclic loading by expressing markers of proliferation and differentiation, whereas compressive loading appears to favor osteogenesis. Braincase and facial sutures exhibit similar mechanical behavior and reactions despite their different natural environments.
Research Interests:
Cranial bones and sutures are mechanically loaded during mastication. Their response to masticatory strain, however, is largely unknown, especially in the context of age change. Using strain gages, this study investigated masticatory... more
Cranial bones and sutures are mechanically loaded during mastication. Their response to masticatory strain, however, is largely unknown, especially in the context of age change. Using strain gages, this study investigated masticatory strain in the posterior interfrontal and the anterior interparietal sutures and their adjacent bones in 3- and 7-month-old miniature swine (Sus scrofa). Double-fluorochrome labeling of these animals and an additional 5-month group was used to reveal suture and bone growth as well as features of suture morphology and fusion. With increasing age, the posterior interfrontal suture strain decreased in magnitude and changed in pattern from pure compression to both compression and tension, whereas the interparietal suture remained in tension and the magnitude increased unless the suture was fused. Morphologically, the posterior interfrontal suture was highly interdigitated at 3 months and then lost interdigitation ectocranially in older pigs, whereas the ante...
Research Interests:
Despite a number of previous biomechanical studies on the zygomatic arch, unanswered questions remain about its three-dimensional loading and growth. Using young miniature swine, we have for the first time recorded strains from both the... more
Despite a number of previous biomechanical studies on the zygomatic arch, unanswered questions remain about its three-dimensional loading and growth. Using young miniature swine, we have for the first time recorded strains from both the medial and lateral aspects of the squamosal bone during mastication and masseter muscle stimulation. Strains from the zygomatic bone flange and zygomatic arch growth data were also obtained from the same animals. A second study on a younger group of animals examined the growth of the zygomatic flange following partial removal of the masseter. Strain data indicated that the squamosal bone is bent out-of-plane and that this pattern of loading is quite different from that of the adjacent zygomatic bone, which experiences much lower strains with little evidence of out-of-plane bending. Surprisingly, strains were higher in the zygomatic flange during contralateral chews and contralateral masseter stimulations than during ipsilateral chews/stimulations. Th...
Research Interests:
The growth of the nasal septal cartilage is believed to be a driving force of midfacial growth. Cellular proliferation is an important contributor to growth of the cartilage, but this factor has been rarely investigated. The current study... more
The growth of the nasal septal cartilage is believed to be a driving force of midfacial growth. Cellular proliferation is an important contributor to growth of the cartilage, but this factor has been rarely investigated. The current study was undertaken to assess the proliferation and cellular density in the septal cartilage of fast-growing juvenile minipigs. Six minipigs averaging 4.4 ± 1 months old were injected with 5'-bromo-2'-deoxyuridine (BrdU), a thymidine analog, 24 h before death. The septal cartilage was sectioned in the coronal plane and reacted for BrdU. The proliferative index (number of BrdU-positive chondrocytes/total number of chondrocytes) and cellular density (number of cells mm(-2) ) of various locations of the septum were measured and compared in order to determine overall proliferation rate and whether regional variations in proliferative activity and cellular density are present. To provide a time perspective to the problem of midfacial growth, the lengths of the nasal bone and the palate were measured in a collection of 61 dry skulls of minipigs aged 1-8 months. Results showed that the septal chondrocytes were proliferating at a surprisingly high rate (~21%). The proliferative index was higher in the ventral and middle compared with the dorsal locations, and in the central cartilage compared with the perichondrium. No difference in proliferative index was found between the anterior and posterior parts of the septum. Cellular density was higher in the perichondrium than in the central cartilage. Within the central cartilage there was a trend for higher cellular density anteriorly. In conclusion, the rapidly growing midface of juvenile minipigs is associated with a high rate of septal proliferation, especially in the ventral half of the cartilage.
Research Interests:
Our knowledge of total body bone resorption during growth is limited. The primary purpose of this study was to determine if a commercially available bone resorption assay, developed for measuring human bone resorption, could be used to... more
Our knowledge of total body bone resorption during growth is limited. The primary purpose of this study was to determine if a commercially available bone resorption assay, developed for measuring human bone resorption, could be used to measure whole body bone resorption in young, growing pigs. A secondary purpose was to evaluate if this method could detect changes in bone resorption in response to certain dental appliances which have been shown to change mandibular and maxillary growth. Five growing 4-month-old male Hanford minipigs (Sus scrofa) were housed in metabolic cages for 24 h, every other day, over a period of 1 month. Three of the animals were fitted with a mandibular protrusive orthodontic appliance. Total 24 h urines were collected in which the concentration of creatinine and collagen type I N-telopeptide crosslinks (NTx, a marker of bone resorption) were measured. The NTx immunoassay was originally developed for the analysis of human urine. Pig bone was powdered, defatt...
Research Interests:
A comparative study of chewing in miniature pigs at three stages of dental development was carried out using electromyography and movement analysis. The mastication of the youngest pigs was characterized by longer burst durations of jaw... more
A comparative study of chewing in miniature pigs at three stages of dental development was carried out using electromyography and movement analysis. The mastication of the youngest pigs was characterized by longer burst durations of jaw muscles, particularly closing muscles, and greater relative jaw opening. Chewing side alternated irregularly and burst durations were variable. Between the intermediate and oldest ages, the parameters remained almost unchanged. Because the amount of dental development that occurred between the second two stages was just as extensive as that between the first two, progressive eruption cannot account for the age changes observed in mastication.
Research Interests: Age, Female, Animals, Male, Electromyography, and 7 moreChewing, Muscle development, Mastication, Swine, Tooth Eruption, Age Factors, and Tooth
During mastication the adult pig masseter contracts with a complex pattern involving a wave of electromyographic (EMG) activity moving from the ventro-rostral corner to the dorso-caudal corner. The present study was undertaken to... more
During mastication the adult pig masseter contracts with a complex pattern involving a wave of electromyographic (EMG) activity moving from the ventro-rostral corner to the dorso-caudal corner. The present study was undertaken to ascertain the ontogeny of that contraction pattern. Anatomical measurements were made on masseters from fetal, infant, and juvenile pigs. EMG activity from different parts of the masseter was recorded along with oral movements in infant and juvenile pigs as they suckled, drank, and chewed on food and non-food objects. The basic arrangement of muscle fibers and tendinous aponeuroses was found to be the same in all ages. The longest and most vertical fibers were found rostrally and ventrally, whereas the shortest and most horizontal fibers were found caudally and dorsally. The length of fasciculi decreased with age, relative to muscle weight. Variance in length among different parts of the muscle increased with age. Fetal masseters were oriented generally mor...
Research Interests:
At incremental whole muscle lengths, active isometric and passive elastic forces were recorded from the masseter and digastric muscles of anaesthetized miniature pigs (Hanford) weighing 2.0-20.0 kg. Wet muscle mass and maximum tetanic... more
At incremental whole muscle lengths, active isometric and passive elastic forces were recorded from the masseter and digastric muscles of anaesthetized miniature pigs (Hanford) weighing 2.0-20.0 kg. Wet muscle mass and maximum tetanic tension values for masseter exceed those for digastric and increase more rapidly with body mass (age). At any body mass, masseter exceeds digastric in the ratio of optimum length (that length at which maximum tetanic tension is produced) to in situ muscle length (that length which corresponds to the jaw in a closed position) and the proportion of passive tension comprising total (passive plus active) tension. Passive elastic tension begins to rise in masseter at lengths as short as 87% of optimum (in younger pigs). In digastric, passive tension is absent until the muscle is stretched to a length slightly longer than optimum in younger pigs but occurs at shorter lengths in older pigs. Contractile properties explain functional differences between massete...
Research Interests:
... Susan W. Herring, Katherine L. Rafferty, Zi Jun Liu, and Zongyang Sun ... side contraction in which the ZM is strongly active when the superficial masseter and medial pterygoid activ-ity are diminished (Scapino, 1981; Ravosa and... more
... Susan W. Herring, Katherine L. Rafferty, Zi Jun Liu, and Zongyang Sun ... side contraction in which the ZM is strongly active when the superficial masseter and medial pterygoid activ-ity are diminished (Scapino, 1981; Ravosa and Hylander, 1994; Lieberman and Crompton, 2000 ...
Research Interests:
Page 1. Vol. 108, No. 962 The American Naturalist July-August 1974 THE SUPERFICIAL MASSETER AND GAPE IN M MLS SUSAN W. HERRING AND STEPHEN E. HERRING Department of Oral Anatomy, University of Illinois at the Medical Center, Chicago,... more
Page 1. Vol. 108, No. 962 The American Naturalist July-August 1974 THE SUPERFICIAL MASSETER AND GAPE IN M MLS SUSAN W. HERRING AND STEPHEN E. HERRING Department of Oral Anatomy, University of Illinois at the Medical Center, Chicago, Illinois 60612 ...