Mandibular shape and skeletal divergency.
(17/1956)
Pre-treatment lateral cephalograms of 41 skeletal Class I girls aged 11 to 15 were divided according to MP-SN angle: lower than 28 degrees (hypodivergent, 10 girls), between 31 and 34 degrees (normodivergent, 18 girls), or larger than 37 degrees (hyperdivergent, 13 girls). The mandibular outlines were traced and digitized, and differences in shape were quantified using the elliptic Fourier series. Size differences were measured from the areas enclosed by the mandibular outlines. Shape differences were assessed by calculating a morphological distance (MD) between the size-independent mean mathematical reconstructions of the mandibular outlines of the three divergency classes. Mandibular shape was different in the three classes: large variations were found in hyperdivergent girls versus normodivergent girls (MD = 4.61), while smaller differences were observed in hypodivergent girls (MD versus normodivergent 2.91). Mean size-independent mandibular shapes were superimposed on an axis passing through the centres of gravity of the condyle and of the chin. Normodivergent and hyperdivergent mandibles differed mostly at gonion, the coronoid process, sigmoid notch, alveolar process, posterior border of the ramus, and along the mandibular plane. A significant size effect was also found, with smaller mandibles in the hyperdivergent girls. (+info)
The functional shift of the mandible in unilateral posterior crossbite and the adaptation of the temporomandibular joints: a pilot study.
(18/1956)
Changes in the functional shift of the mandibular midline and the condyles were studied during treatment of unilateral posterior crossbite in six children, aged 7-11 years. An expansion plate with covered occlusal surfaces was used as a reflex-releasing stabilizing splint during an initial diagnostic phase (I) in order to determine the structural (i.e. non-guided) position of the mandible. The same plate was used for expansion and retention (phase II), followed by a post-retention phase (III) without the appliance. Before and after each phase, the functional shift was determined kinesiographically and on transcranial radiographs by concurrent recordings with and without the splint. Transverse mandibular position was also recorded on cephalometric radiographs. Prior to phase I, the mandibular midline deviated more than 2 mm and, in occlusion (ICP), the condyles showed normally centred positions in the sagittal plane. With the splint, the condyle on the crossbite side was displaced 2.4 mm (P < 0.05) forwards compared with the ICP, while the position of the condyle on the non-crossbite side was unaltered. After phase III, the deviation of the midline had been eliminated. Sagittal condylar positions in the ICP still did not deviate from the normal, and the splint position was now obtained by symmetrical forward movement of both condyles (1.3 and 1.4 mm). These findings suggest that the TMJs adapted to displacements of the mandible by condylar growth or surface modelling of the fossa. The rest position remained directly caudal to the ICP during treatment. Thus, the splint position, rather than the rest position should be used to determine the therapeutic position of the mandible. (+info)
A comparison of sagittal and vertical effects between bonded rapid and slow maxillary expansion procedures.
(19/1956)
The purpose of this study was to determine the vertical and sagittal effects of bonded rapid maxillary expansion (RME), and bonded slow maxillary expansion (SME) procedures, and to compare these effects between the groups. Subjects with maxillary bilateral crossbites were selected and two treatment groups with 12 patients in each were constructed. The Hyrax screw in the RME treatment group and the spring of the Minne-Expander in the SME treatment group were embedded in the posterior bite planes, which had a thickness of 1 mm. At the end of active treatment these appliances were worn for retention for an additional 3 months. Lateral cephalometric radiographs were taken at the beginning and end of treatment, and at the end of the retention period. The maxilla showed anterior displacement in both groups. The mandible significantly rotated downward and backward only in the RME group. The inter-incisal angle and overjet increased in both groups. No significant differences were observed for the net changes between the two groups. (+info)
Histochemical and immunohistochemical analysis of the mechanism of calcification of Meckel's cartilage during mandible development in rodents.
(20/1956)
It is widely accepted that Meckel's cartilage in mammals is uncalcified hyaline cartilage that is resorbed and is not involved in bone formation of the mandible. We examined the spatial and temporal characteristics of matrix calcification in Meckel's cartilage, using histochemical and immunocytochemical methods, electron microscopy and an electron probe microanalyser. The intramandibular portion of Meckel's cartilage could be divided schematically into anterior and posterior portions with respect to the site of initiation of ossification beneath the mental foramen. Calcification of the matrix occurred in areas in which alkaline phosphatase activity could be detected by light and electron microscopy and by immunohistochemical staining. The expression of type X collagen was restricted to the hypertrophic cells of intramandibular Meckel's cartilage, and staining with alizarin red and von Kossa stain revealed that calcification progressed in both posterior and anterior directions from the primary centre of ossification. After the active cellular resorption of calcified cartilage matrix, new osseous islands were formed by trabecular bone that intruded from the perichondrial bone collar. Evidence of such formation of bone was supported by results of double immunofluorescence staining specific for type I and type II collagens, in addition to results of immunostaining for osteopontin. Calcification of the posterior portion resembled that in the anterior portion of intramandibular Meckel's cartilage, and our findings indicate that the posterior portion also contributes to the bone formation of the mandible by an endochondral-type mechanism of calcification. (+info)
Intraoperative spasm of coronary and peripheral artery--a case occurring after tourniquet deflation during sevoflurane anesthesia.
(21/1956)
A 68-yr-old man with a 9-yr history of hypertension presented for hemiglossectomy, segmental resection of the mandible, and the radial forearm free flap grafting. Intraoperatively, facial artery spasm was observed during microvascular suturing of the radial artery to the facial artery. Simultaneously, systolic blood pressure decreased from 100 to 80 torr and the ST segment elevated to 15 mm from the base line. The possible mechanisms responsible for vasospasm in coronary as well as in peripheral arteries under sevoflurane anesthesia are discussed. (+info)
Developmental morphology of the head mesoderm and reevaluation of segmental theories of the vertebrate head: evidence from embryos of an agnathan vertebrate, Lampetra japonica.
(22/1956)
Due to the peculiar morphology of its preotic head, lampreys have long been treated as an intermediate animal which links amphioxus and gnathostomes. To reevaluate the segmental theory of classical comparative embryology, mesodermal development was observed in embryos of a lamprey, Lampetra japonica, by scanning electron microscopy and immunohistochemistry. Signs of segmentation are visible in future postotic somites at an early neurula stage, whereas the rostral mesoderm is unsegmented and rostromedially confluent with the prechordal plate. The premandibular and mandibular mesoderm develop from the prechordal plate in a caudal to rostral direction and can be called the preaxial mesoderm as opposed to the caudally developing gastral mesoderm. With the exception of the premandibular mesoderm, the head mesodermal sheet is secondarily regionalized by the otocyst and pharyngeal pouches into the mandibular mesoderm, hyoid mesoderm, and somite 0. The head mesodermal components never develop into cephalic myotomes, but the latter develop only from postotic somites. These results show that the lamprey embryo shows a typical vertebrate phylotype and that the basic mesodermal configuration of vertebrates already existed prior to the split of agnatha-gnathostomata; lamprey does not represent an intermediate state between amphioxus and gnathostomes. Unlike interpretations of theories of head segmentation that the mesodermal segments are primarily equivalent along the axis, there is no evidence in vertebrate embryos for the presence of preotic myotomes. We conclude that mesomere-based theories of head metamerism are inappropriate and that the formulated vertebrate head should possess the distinction between primarily unsegmented head mesoderm which includes preaxial components at least in part and somites in the trunk which are shared in all the known vertebrate embryos as the vertebrate phylotype. (+info)
The gene for cherubism maps to chromosome 4p16.
(23/1956)
Cherubism is an autosomal dominant disorder that may be related to tooth development and eruption. It is a disorder of age-related bone remodeling, mostly limited to the maxilla and the mandible, with loss of bone in the jaws and its replacement with large amounts of fibrous tissue. We have used a genomewide search with a three-generation family and have established linkage to chromosome 4p16. Three other families affected with cherubism were also genotyped and were mapped to the same locus. The combined LOD score is 4.21 at a recombination fraction of 0, and the locus spans an interval of approximately 22 cM. (+info)
A large maxillofacial prosthesis for total mandibular defect: a case report.
(24/1956)
We successfully fabricated a large maxillofacial prosthesis for replacement of a total mandibular defect resulting from surgical failure to reconstruct the mandible. Although a number of reports have described procedures for fabricating midfacial prostheses, there is little information on prostheses to compensate for total loss of the mandible. A 54-year-old woman was referred to the Dentistry and Oral Surgery Division of the National Cancer Center Hospital with total loss of the mandible and the surrounding facial soft tissue. The facial prosthesis we used to treat this patient is unique in that it is adequately retained without the use of extraoral implants and conventional adhesives. This prosthesis is retained by the bilateral auricles and the remaining upper front teeth. We present details of the design of this large silicone maxillofacial prosthesis, with which we successfully rehabilitated the patient. (+info)