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At least 1,423 records · Page 79Linked to original sources
PubMed2003

Chemical sympathectomy-induced changes in TH-, VIP-, and CGRP-immunoreactive fibers in the rat mandible periosteum: influence on bone resorption.

The expression of neurotransmitter receptors by bone cells supports the concept that the nervous system is a regulator of bone metabolism. The discrimination of the respective roles of the sensory and sympathetic nervous systems requires evidence of topographic relationships between the corresponding fibers and the cells involved in bone turnover, in vivo. In this study, the influence of the sympathetic system on bone resorption was assessed by using a synchronized model of cortical resorption along the mandible. The sympathetic system was destroyed by daily injections of guanethidine (40 mg/kg) for 25 days; a resorption wave was induced on day 21. The distribution of periosteal tyrosine-hydroxylase (TH)-, vasoactive intestinal polypeptide (VIP)-, and calcitonin gene-related peptide (CGRP)-immunoreactive (IR) fibers was studied by compartmentalizing the periosteum. Most fibers were located in the distal, non-osteogenic compartment. TH-IR fibers were located perivascularly, VIP-IR fibers were gathered at the boundary with the osteogenic compartment, and CGRP-IR fibers were scattered. Sympathectomy decreased the number of TH- and VIP-IR fibers and increased the number of CGRP-IR fibers, without changing their topography. After the injection of Fast blue, a retrograde fluorescent marker, over the periosteum, fluorescent neuronal cell bodies were found in the superior cervical ganglion (SCG). Many neurons were TH-IR and very few were VIP-IR. Sympathectomy decreased the numbers of fluorescent and TH-IR cell bodies. It also decreased the number of preosteoclasts and osteoclasts, which had a drastic effect on the cortical bone surface, as assessed by scanning electron microscopy. These data indicate that VIP-IR fibers have a strategic position close to the most peripheral and less differentiated, osteogenic cells, pointing to a functional relationship. As poorly differentiated osteogenic cells support preosteoclast differentiation, VIP-IR fibers may be involved in this process, as suggested by the smaller number of preosteoclasts in sympathectomized rats. Although VIP is predominantly a parasympathetic mediator, it seemed to be conveyed by sympathetic fibers, as shown by the marked effect of guanethidine treatment. Nevertheless, these fibers did not originate from the SCG, contrary to TH-IR fibers.

Adrenergic Fibers↗
PubMed2003

Osteoclastic bone resorption around intraosseous screws in rat and pig mandibles.

This report describes osteoclastic bone resorption around intraosseous fixation screws in rat and pig mandibles. These screws supported distraction devices and provided for neutral fixation following the distraction period. Progressive clinical instability of bicortical screws and radiographic and histologic evidence of osseous resorption were frequent findings. In rats, clinical evaluation revealed screw loss and/or loosening in 50% of the rats between 11 and 30 days of neutral fixation. Radiographic signs of resorption were apparent around 60% of the screws that were in place at the end of the observation period. The total rate of resorption or loss was 64 of 80 screws (80%). Histologic examination showed partial or extensive osteolysis around the screw holes in 87% of screws that were clinically fixed in the bone at sacrifice. In histologic sections of porcine specimens, osseous resorption around identifiable screw holes was present in 75% of the cases, and showed progressive increase in resorption with time. Osteoclastic resorption was common around bicortical screws that were evaluated after they had served for osseous stability.

Animals↗
PubMed1984

Movements of the mandibles and tongue during mastication and swallowing in Pteropus giganteus (megachiroptera): a cineradiographical study.

Quantitative lateral and dorsoventral cineradiography shows that the masticatory movements of the mandible, condyles, tongue, and hyoid of Pteropus giganteus (Chiroptera) move along highly regular paths that are characteristic for each of the three food types tested. Mandibular movements are predominantly orthal, although a small forward translation occurs early in opening and small lateral deflections occur in both opening and closing phases. These deflections are related to the existence of active (bolus bearing) and balancing sides of the jaws, chewing being not truly bilateral. The deflections are associated with a shift of both condyles toward one side. In consequence the active condyle is located in a lateral part of the associated fossa, the inactive condyle in a medial part. Food transfer from side to side involves a reversal of the chewing direction during opening. Such reversals are especially frequent near the end of a chewing sequence. The fore, middle, and hind parts of the tongue differ in their movement patterns. Movements of the fore part, and to a lesser extent of the middle part, follow the open-close movements of the lower jaw. The hind part of the tongue moves predominantly dorsally during slow closing and ventrally during fast opening and fast closing. All three parts move forward during slow closing and slow opening, and backward during fast opening and fast closing. Movements of the hyoid are closely synchronized with those of the hind part of the tongue. Furthermore, tongue and hyoid movements are synchronized with jaw movements. All cycles of Pteropus giganteus are transport cycles, and the synchrony appears to reflect the consistency of the food (soft pulp, juices). Food consistency also accounts for the high swallowing rate and the absence of any significant difference between nonswallowing and swallowing cycles.

Adaptation, Physiological↗
PubMed2005

Use of vascularized iliac crest with internal oblique muscle flap for mandible reconstruction.

In the last decade, immediate reconstruction of maxillary bones following extensive trauma, large oncological defects, or late effects of radiation therapy has proved to be a reliable morpho-functional reconstruction technique. Use of the vascularized iliac crest with an internal oblique flap has become our flap of choice for mandible reconstruction when there is no need for overlying facial skin or oral sphincter reconstruction, and for bone segments within 6-15 cm of length. The advantages of this composite bone flap are the large and resizable bone stock available, the quality of bone transferred with an optimal height, depth, and contour of bone to maintain a good facial profile, and the possibility to reconstruct properly the oral lining, with a portion of the internal oblique muscle flap raised with the same pedicle that epithelializes during the healing stages. We present the experience of the Department of Maxillofacial Surgery of "S. Maria della Misericordia" Regional Hospital in Udine, Italy.

Adult↗
PubMed2006

The fetal mandible: an in utero sonographic evaluation between 11 and 31 weeks' gestation.

OBJECTIVE: To construct a growth chart of the mandible throughout gestation. METHODS: A prospective cross-sectional study of normal singleton pregnancies was conducted. Measurements of the fetal mandibular transverse and antero-posterior diameters were performed with high-resolution transvaginal and transabdominal ultrasonography in 490 pregnant women with singleton low-risk pregnancies between 11 and 31 weeks' gestation. RESULTS: The mandibular transverse and antero-posterior diameters were recorded by week of gestation and the ratio was calculated: mandibular ratio (MR) = 1.7759 - 0.01047 x gestational week. There was a negative linear correlation (-1.047%) for each incoming week of gestation. Normal values (+/-1SD and 2SD) were established. CONCLUSION: The present data provides a normal range of fetal mandibular diameters during normal pregnancies and introduces a new parameter, the mandibular ratio, for the intrauterine assessment of the fetal mandibular development.

Cross-Sectional Studies↗
PubMed1998

Discrete trait and dental morphometric affinities of the Tabun 2 mandible.

Evolutionary scenarios of Near Eastern Middle Paleolithic hominids depend to an extent upon whether the terminal Middle Pleistocene Tabun 2 mandible has its primary affinities with the late archaic (Neandertal sensu lato) or early modern (Qafzeh-Skhul) human lineage in the region. Since the specimen has been assigned to each group or seen as bridging them, we have re-examined its morphological affinities relative to these two samples, as well as to European samples of later Pleistocene hominids. This has been done with respect to posterior corporeal and ramal discrete traits, symphyseal morphology, and proportional morphometric patterns along the dental arcade. Taking within and between sample ranges of variation into account, the lateral corporeal and ramal discrete characters are either ambiguous or suggest Neandertal affinities. Anterior symphyseal morphology is largely unknown, but a mentum osseum is indicated by a moderate incisura mandibulare anterior, and the tuber symphyseos did not extend superiorly toward the alveoli, a non-modern arrangement. The lingual symphysis presents the largest planum alveolare known for a Near Eastern Middle Paleolithic hominid. Morphometric analysis of proportions along the dental arcade separate Tabun 2 from Near Eastern and European early modern humans and place it among the late archaic humans. It is dentally closest to the Near Eastern late archaic human lineage and the Krapina sample. These analyses therefore indicate that it is best seen as part of the Near Eastern late archaic human lineage with only the mentum osseum and incisure shape indicating any approach to the Qafzeh-Skhul humans within the Near Eastern Middle Paleolithic.

Animals↗
PubMed2000

Elliptical fourier analysis of symphyseal shape in great ape mandibles.

The midsagittal profile of the mandibular symphysis has served as both a taxonomic marker and a phylogenetically salient character in debates over hominoid evolution. Nevertheless, the utility of symphyseal shape as an informative attribute for paleobiological reconstructions is suspect. Quantification of shape variation has proven to be particularly problematic; it has long been recognized that conventional linear measurements (and the indices derived from them), while replicable, summarize aspects of shape very poorly because of the vast amount of contour information that is lost in the process. In this study, a type of Fourier analysis is applied to cross-sectional contours of ape mandibles in order to provide a mathematical accounting of shape variation in a "global" sense; that is, by applying the "totality" of contour information in a comparative analysis. Shape variation in the mandibular symphysis is explored through the decomposition of coordinate data into elliptical Fourier coefficients. These coefficients are used to compute average taxonomic distances (ATD) among individuals of chimpanzees, gorillas, and orang-utans. The resulting shape-based distances are summarized via clustering (UPGMA) and ordination (principal coordinates analysis-PCO). Principal coordinate scores are subjected to analysis of variance in univariate and multivariate designs; these data are also applied to discriminant function analyses. Species and sex effects on morphology are statistically significant; however, no significant interaction of these factors is indicated. This would seem to imply that patterns of sexual dimorphism are not distinct among great apes; to the contrary, within-species sex comparisons reveal that significant size and shape dimorphism is present only in Gorilla. Despite significant size dimorphism in Pan and Pongo, significant shape differences between males and females are not apparent in these taxa. These results suggest that it is theoretically possible to sort taxa by a symphyseal shape criterion, but the discriminant function results suggest that there still exists a large potential for error in assigning particular shapes to a given species or sex. Thus, despite real shape differences among these species, the use of symphyseal shape as a character in species identification or in systematic arguments remains limited and problematic.

Analysis of Variance↗
PubMed1991

Characterization of endosteal osteoblasts isolated from human maxilla and mandible: an experimental system for biocompatibility tests.

Fragments of cancellous and cortical bone from human maxilla and mandible were cultured by the explant technique. Cells isolated by trypsinization of primary cultures were characterized as osteoblasts on the basis of intracellular alkaline phosphatase activity, the constituents of the extracellular matrix, and response to human parathormone (PTH). In culture, the osteoblasts often gave rise to superposed clumps of large cells whose cytoplasm contained endoplasmic reticulum, numerous mitochondria, vacuoles, and a dense network of intermediate filaments, often at the level of the plasma membrane. In the presence of vitamin C and 1,25-dihydroxyvitamin D3, the osteoblasts produced an extracellular matrix composed of collagen type I and various non-collagenous proteins, including osteocalcin. Biochemical test results were comparable to those reported for osteoblasts of other origins (rat calvaria, human iliac crest), and namely elevated intracellular alkaline phosphatase activity and cAMP accumulation in response to stimulation by human PTH (1-34). Osteoblasts isolated in this manner were cultured in the presence of pure titanium disks to determine the effects of exposure to this metal. Electron microscopy revealed few significant differences in cell growth and specific enzyme activity compared to control osteoblasts grown on plastic dishes, reflecting the excellent biologic and biochemical relationship between the osteoblasts and pure titanium. This experimental system thus appears suitable for biocompatibility studies, and in particular, evaluation of dental implants.

Alkaline Phosphatase↗
PubMed1996

Primary lymphoma of the mandible with diffuse widening of the mandibular canal: report of a case.

A case of primary non-Hodgkin's lymphoma (NHL) of the mandible with unusual radiographic presentation is reported. The panoramic radiography revealed diffuse widening of the right mandibular canal with ill-defined margins and absence of edge sclerosis. Computed tomography showed infiltration of the superior portion of the canal with involvement of the vestibular cortex of the bone and of the alveolar ridge.

Adult↗
PubMed1985

[Discriminant analysis of the mandible for sex determination].

Seventeen measuring parameters were used to characterize 197 mandibles (109 males, 88 females) taken from the corpses of people 20-80 years of age from the Rhine-Main-Neckar area. The representative measuring parameters and discriminating functions of intact lower jaws and lower jaw fragments of most frequent fracture types were determined in this practice group by means of discriminating analysis. In the present research material it was possible to determine sex accurately from an intact lower jaw bone in 82.6% (m) and 79.5% (f) of the cases. Furthermore, our results show clearly that sex may even be determined from lower jaw fragments. The classification was correct, depending on the type of fragment, in 72.5%-81.7% (m) and 71.6%-79.5% (f) of the cases.

Adult↗
PubMed1994

Gap junction proteins exhibit early and specific expression during intramembranous bone formation in the developing chick mandible.

The spatial and temporal expression of three closely related members of the connexin family of gap junction proteins (connexin42, Cx42; connexin43, Cx43; and connexin45, Cx45) was evaluated during bone formation in the mandibular process of the chick embryo. Mandibles of chick embryos from Hamburger and Hamilton stage 25 (approximately 5 days) through 19 days of development were dissected, serially sectioned and processed for immunocytochemical localization, employing site-specific anti-connexin antibodies. Our data revealed that (1) Cx43 was present throughout mandibular bone formation; (2) although it appeared to be associated with all bone cell types, Cx43 was concentrated in mesenchymal cells during the earliest stages in the osteogenic lineage; (3) most importantly, the localization of Cx43 at sites of bone formation appeared to precede the overt expression of the osteogenic phenotype; (4) by contrast, Cx45 was more restricted, spatially and temporally, in its distribution; (5) Cx42 expression was not detected in osteogenic tissue during mandibular bone formation. From all of the data obtained, Cx45 appeared to be associated with stages of bone formation characterized by the elaboration of matrix and the progressive expression of the differentiated osteogenic phenotype. Cx43 appeared to be associated with condensation of mesenchyme and the earliest stages of osteogenesis. Because of these associations, we propose that connexin expression may be necessary for the initiation of bone formation and the full expression of the osteogenic phenotype.

Amino Acid Sequence↗
PubMed1980

Early morphological changes in rabbit mandible after cryogenic application.

In nine rabbits cryosurgery was performed on the left lateral side of the jaw bone, using liquid nitrogen as cold medium. Simultaneous temperature recordings were made of the cryosurgically treated area by the insertion of a thermocouple into the mandibular canal. The right side of the mandible was exposed but not frozen. The animals were killed by infusion of india ink into the abdominal aorta either within 1 h or after 48 h following the cryogenic application. Specimens were analysed by microangiography according to the Spalteholz technique and by light microscopy. The microcirculation within cortical bone and marrow cavity of the frozen area was completely arrested while the alveolar artery remained patent. The circulation of the soft tissue overlying the area treated was disturbed showing signs of thrombosis and extravasation of blood corpuscles.

Animals↗
PubMed1992

Glucocorticoid-induced osteoporosis in the lumbar spine, forearm, and mandible of nephrotic patients: a double-blind study on the high-dose, long-term effects of prednisone versus deflazacort.

The long-term effects of high dose steroid treatment with either prednisone (PDN) or deflazacort (DFZ) were examined on various parts of the skeleton in 29 patients with nephrotic syndrome. All had normal skeleton at the start of the steroid treatment. At the beginning, PDN was given as 80 mg/day and tapered down to 20 mg/day for 1 year and DFZ was given in an equipotent dosage. Twenty-three patients completed 6 months of treatment, and 18 patients completed 12 months of treatment. Beside laboratory parameters to ensure the effect of treatment on the nephrotic syndrome, all had measurements of the bone mineral content (BMC) at 0, 6, and 12 months of treatment. BMC was measured by single photon absorptiometry of both forearms and by dual photon absorptiometry of the mandible, forearms, and lumbar spine. The effect of DFZ was compared to that of PDN due to a potential "calcium sparing" effect of DFZ. The therapeutical effects on the nephrotic syndrome were not different between the two drugs. Urinary 24-hour protein decreased from 9.9 to 1.1 g in the DFZ-treated patients and from 8.0 to 1.4 g in the PDN-treated patients. Plasma albumin concentration normalized in both groups. Both groups of steroid-treated patients had a significant reduction of the BMC levels in all parts of the skeleton. However, the bone decay rates per month were significantly different between different bone regions and between different drug regimes. In the forearm, the bone decay rate was 5.3%/year in the PDN group and 2.0%/year in the DFZ group (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed1984

Central intravascular papillary endothelial hyperplasia of the mandible.

Light and electron microscopic findings in papillary endothelial hyperplasia of the mandible in a 49-year-old female are reported. The endothelial cell-lined papillary projection into a cystic lumen was examined by light microscopy and characteristic features of the endothelial cells were found by electron microscopy. Factor VIII-related antigen was demonstrated in the endothelial cells by the immunoperoxidase technique.

Antigens↗
PubMed1998

Morphological changes of the mandible and temporomandibular joints in a patient with cleidocranial dysostosis.

The morphology of the dentition and facial parts of the skull in a 17-year-old girl with cleidocranial dysostosis are described. The opening movement of the mandible was limited to 18 mm. Radiological examination demonstrated that this limitation was due to deformities of the temporomandibular joints. To our knowledge, such deformities have not been described in the literature.

Adolescent↗
PubMed1993

The relationship between Meckel's cartilage and the development of the human fetal mandible.

This work studied the development of the ventral part of Meckel's cartilage and its relationship to the morphogenesis of the mandible in a series of human fetuses. The development of the cartilage was followed up to the end of the embryonic period (stage 23, 8th week) when the primary ossification centre, which was formed from a condensation of embryonic mesenchyme, had become two bony plates forming a trough in which lay the neurovascular bundle. From this trough invagination of the bony plate formed the dental crypt. The primary ossification centre disappeared around the sixth month of fetal life.

Cartilage↗
PubMed1993

Relations between Meckel's cartilage and the morphogenesis of the mandible in the human embryo.

Based on a series of human embryos classified in stages, the authors studied the evolution of Meckel's cartilage in its ventral portion and its relations to the morphogenesis of the mandible. Three stages appeared particularly important: stage 16, appearance of Meckel's cartilage; stage 20, beginning of membranous ossification; and stage 23, end of the embryonic period (8th week). The primitive bony nodule which develops from the embryonic mesenchyme appears as a double bony layer forming a groove containing the neurovascular bundle, into which the dental lamina is also invaginated.

Cartilage↗
PubMed1990

[A new procedure for profile prognosis in the surgical displacement of the maxilla and the mandible].

One of the most important goals of combined orthodontic-surgical treatment is the harmonization of the soft tissue profile. For a reliable prognosis of the soft tissue profile after surgical intervention, the soft tissue response to hard tissue displacements should be analysed in regard to horizontal and vertical effects. The material consists of the pre- and postsurgical cephalograms of 40 patients who underwent a Le Fort I osteotomy, 54 patients with displacement of the mandible by means of a sagittal split (Obwegeser/DalPont), and 42 patients with combined upper and lower repositioning. In contrast with recent investigations, the analysis of the soft tissue response was not based on the conventional landmarks. Instead of this, changes of the entire soft tissue profile were analysed in relation with the underlying outline of the hard tissue. The processed material resulted in numerical data which permit the elaboration of a profile prognosis with distinction of horizontal and vertical effects also taking the error assessment into account.

Cephalometry↗