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Odontogenic fibromyxomas are extremely rare, benign odontogenic tumours, found preferentially in the second and third decades of life. They have a preference for the mandible. The present case report describes a 25-year-old patient with an odontogenic fibromyxoma in the lower jaw. Differential diagnosis, histology and therapy of this neoplasm are described.
In recent years lengthening of the human mandible by distraction osteogenesis has become an accepted treatment for correction of severe mandibular disto-basal discrepancies. Using extra-oral and intra-oral distraction devices the technique of osseous anchorage is usually preferred. To avoid the disadvantages of this method it is the aim of many research groups to develop a tooth-borne distraction. In the present animal study, six minipigs were treated with a new solely dentally fixed orthodontic device for mandibular distraction osteogenesis. Following bilateral osteotomy in the dentigerous area of the mandibular body and a latent period of 2-7 days, a mandibular lengthening of 9 mm was reached within a period of 9 days. This situation was retained using the distraction device for 6 weeks. After the removal of the apparatus, there followed a period of another 6 weeks of consolidation. The callus and bone formation and potential dental, periodontal and nerval reactions were radiologically examined and histological examination was performed at the end of the experiment. At 12 weeks after the mandibular lengthening, the osteogenesis in the distraction areas was complete. No destructive processes were recognizable, either at the roots or at the periodontium of the teeth near the osteotomy gap. The mandibular nerve at the osteotomy site remained intact. The results justified transferring this procedure to humans. The clinical application of the device is presented.
In recent years, lengthening the human mandible by distraction osteogenesis has become an accepted treatment to correct severe mandibular hypoplasia. Using intraoral unidirectional and extraoral bidirectional distraction devices we report about our experiences and results in the application of the bone distraction technique in four selected cases of syndromal disease, including various forms of mandibular hypoplastic malformations. The patients involved were a boy with Pierre Robin syndrome, a girl with unilateral facial hypoplasia in Goldenhar's syndrome, a case with Nager's syndrome, and a rare case of midline deficiency caused by partial deletion of chromosome 18 (18p-syndrome). The distraction period lasted from 6 to 30 days and new bone formation, ranging from 6 to 28 mm, was achieved.
In a sample of lateral x-ray cephalograms of children with obstructing adenoids, a dorsal rotation of the mandibular ramus was found to characterize the facial skeleton. The mandibular body and the condylar process were not correspondingly rotated. The findings suggest that dorsal rotation of the mandible occurring in association with various pathologic processes could always be primarily a response to an encroachment of the pharyngeal space. A possible involvement of the clivus region, to a minor degree, was also indicated. The need for "tailormade" cephalometric methods in studies of specific problems is stressed.
Two case reports of a modified sagittal split osteotomy of the ramus of the mandible are presented which illustrate a technically simplified modality of treating various dentofacial abnormalities. A brief review of the literature is presented and observations are made on the procedures. The need for future documentation of intraoperative and postoperative results on this type of procedure is recommended.
The purpose of this study was to clarify the relative importance of the condyle in mandibular growth. Activated papain, a protease which inhibits endochondral growth, was injected for 4 weeks into the left temporomandibular joints of growing rabbits. Histologic and morphologic changes were evaluated microscopically and by measurement of dried skulls and serial cephalometric radiographs. The injected condyles showed a rapid but temporary depletion of the cartilage matrix. Repeated injections produced severe arthritic changes in some cases. The papain caused a significant decrease in vertical ramal growth. Mandibular length was unaffected. The unilateral injections also produced vertical asymmetry characterized by a canting of the mandibular plane superiorly toward the injected side. It was concluded that, in the rabbit, condylar growth is essential for normal vertical growth of the ramus but has little influence on the length of the mandible.
The lower border of the mandible in mandibulofacial dysostosis is characteristic of the syndrome. Evaluation of the cephalograms by means of the medial axis analysis and inflectional tangents captures the shape deformity. Morphometric data from lateral cephalograms on seven patients, ages 3 through 20 years, are reported: a total of 22 observations on three males and four females. These forms were compared to normal mandibular forms from the University of Michigan University School Study. The curvature of the gonial angle in the study population is not distinguishable from the normal curvature. Relative to this apparently normal region, there is a marked downward displacement of the symphysis that results in the curvature typical of the lower mandibular border in this syndrome. These findings are not consistent with earlier reports.
Simultaneous records of masseter-EMG activity and position of the mandible were made on 4 Wistar rats eating four food types: standard food pellets (large pellets), 45 mg precision food pellets (small pellets), bread and pudding. Masseter activity was recorded with chronic bipolar silver EMG electrodes placed within the muscle and led subcutaneously to a pedestal on the head. The transducer indicating jaw position consisted of two tiny inductance coils, placed on the head and under the mandibular symphysis. The lower coil acted as a receiving aerial for the carrier signal supplied via the upper coil, so that distance between the coils, and thus relative jaw position, was traced on the oscilloscope screen. A silent period was found in the masseter-EMG bursts similar to that found in man, where the silent period represents tooth contact and the occlusal phase of chewing (time during which teeth are in the intercuspal position) is defined as the interval between the silent period and the termination of the EMG activity in the muscle. Applying this to the rat data, opening represented 70-75 per cent of the total cycle while the combined closing and occlusion phases comprized 25-30 per cent when either type of pellet was eaten. With bread, closing and occlusal phases represented 56 per cent of the total cycle. For all three food types, muscular force, as indicated by the jaw-closing movement registered by the transducer, continued beyond the masseter EMG. Irregular jaw movements seen when the animals lapped pudding were not correlated directly with masseter activity.
A reconstruction method was employed to study the relative contributions of bone deposition and resorption to the overall growth of an individual bone. Total bone volume and incremental bone volume were measured for 24 mandibles spanning an age range from 22 to 211 days. No obvious relationship was demonstrated between the overall rate of bone formation and age; however, the rate of bone formation per unit volume of the jaw conformed to an exponential curve. The rate of increase in bone volume fell to nearly zero over the experimental period, whilst the rate of new bone addition levelled out at 12-13 mm3/cm3 per day. Thus there was significant bone remodelling after adult size was reached.
Mandibles were cultured in the presence of dibutyryl cyclic AMP (1 mM) and theophylline (1 mM) and in control medium. Controls differentiated normally but the timing of events differed from that in ovo and feathers did not form. With elevated intracellular cyclic-AMP levels, membrane bone did not form in the earlier stages tested and was inhibited or reduced in older ones; chondrogenesis was inhibited only in young explants (HH stage 20) and, in certain instances, it was enhanced. There was precocious and hyperplastic differentiation of mucous cells within oral epithelium but the aboral epithelium was unchanged.
Various regions of the mandibular process were tested for these potentials to determine whether regional differences exist and vary with embryonic age. Mandibular processes from HH stages 17-21.5 were cultured and grafted intact, or were subdivided into medial, mediolateral and lateral fragments and the separate regions cultured or grafted. The intact mandible from all these stages can form cartilage and membrane bone, but the 3 regions are not equally osteogenic and chondrogenic. The lateral region from all stages could form cartilage and membrane bone; the mediolateral region could form cartilage and membrane bone but, in mediolateral fragments from HH stage 17, membrane bone was formed only in scant amounts. The medial region from HH stages 17 and 18 formed cartilage in only 50 per cent of cases and never formed membrane bone. By HH stage 20, the medial region could form membrane bone, but only in scant amounts. Medial fragments from HH stage 21.5 formed extensive membrane bone and cartilage. The acquisition of these potentials, therefore, proceeds in a lateral-to-medial sequence, and the acquisition of an osteogenic potential lags slightly behind that of a chondrogenic potential. These findings do not indicate the mechanisms by which the two subpopulations of chondrogenic and osteogenic cells are distinguished from one another, but they give the temporal and spatial sequence in which this determination must occur.
Development of the mouse embryonic mandible from days 9 to 14 involves tissue interactions in the formation of bone, cartilage, salivary glands and teeth. Growth factors may play an important role in these interactions. Epidermal growth factor (EGF) mRNA expression has been characterized and its presence has been shown to be necessary for odontogenesis. In addition, retinol alters the pattern of dental lamina formation; this effect is correlated with an alteration of the expression of the mRNA for this mitogen (EGF). Transforming growth factor-alpha (TGF alpha) mRNA expression has now been characterized by polymerase chain reaction for this entire period of development (days 9-14). Although the mRNA is present at the same time as EGF (days 9 and 10 only), retinol does not alter the expression of this mitogen as it does EGF. This suggests that retinoids may act to control the proliferative pattern of the dental lamina through EGF expression and not TGF alpha expression, although mRNAs for both mitogens are present at the same time.
The neonatal rat mandible was used as a model to study bone formation, mineralization, quiescence, and resorption, using immunolocalization and a variety of tissue-processing techniques. Monospecific antibodies for osteopontin (OPN), bone sialoprotein (BSP), alkaline phosphatase (AP) and alpha 2HS-glycoprotein (alpha 2HS-GP) were used on fixed paraffin-embedded tissue, fixed frozen tissue and unfixed frozen tissue. Immunostaining was correlated with mineral content by two procedures, the von Kossa and the morin techniques. Morin fluorescence was used with secondary immunostaining to provide a way of closely correlating bone matrix proteins and matrix mineralization. Co-immunolocalization procedures were used to compare the sites of bone proteins in the matrix. AP was found earliest during osteogenic cell differentiation, appearing in the preosteoblasts, followed by OPN and BSP, which first appeared in osteoblasts. alpha 2HS-GP expression was not observed in cells. The results provide clear evidence for the presence of OPN in osteoid, while BSP and alpha 2HS-GP were confined to the mineralized matrix. Immunostaining of bone proteins is highly technique-dependent: immunolocalization investigations required several methods of approach to ensure adequate demonstration of these proteins in cells and matrix. The results support the contention that osteopontin is multifunctional in bone metabolism, and that alpha 2HS-GP, though produced in the liver, is abundant in bone matrix and may also have a function in bone metabolism.
The osteogenic potential of different surface charges was studied by implanting uncharged, negatively changed and positively charged Sephadex beads subperiosteally on the buccal aspect of the mandible. The implant sites were examined 1, 2, and 4 weeks later. New bone formation was observed around the positively charged beads at 2 weeks. An amorphous collagen-free layer seen around the beads consisted of anionic substances and contained needle-like crystals. Tartrate-resistant acid phosphatase-positive, multinucleated giant cells, which had typical fine structural characteristics of osteoclast-like ruffled borders and a clear zone, were observed on the surface of positively charged beads, with osteoblastic cells juxtaposed to them. Bone formation was still going on at 4 weeks in this group. Around the uncharged or negatively charged beads, new bone formation and osteoclast-like cells were not observed at any time. The findings suggest that the surface charge of implant materials has a definite influence on the differentiation of osteoclastic cells and subsequent occurrence of osteoblastic cells leading to formation of bone.
The first indication of cartilage formation was detected on day 14.5 of pregnancy in close connection to the ossifying mandible. A separated blastema was never observed. Thus the findings support the concept that the condylar cartilage develops from already differentiated cells, not from primary undifferentiated mesenchymal cells. Moreover, endochondral bone formation started on day 16 of pregnancy. Although the condylar cartilage basically undergoes the same processes of endochondral bone formation as the long bone, many hypertrophic chondrocytes may survive and are released into the primary spongiosa.
A study of identifying the position of the lingula of the mandible on the external surface is described. The study was undertaken in an attempt to avoid damage to the inferior dental neurovascular bundle during operative procedures on the ascending ramus.
A rational approach to the management of spontaneous fracture of the severely atrophie mandible is illustrated by means of a case report. A study of the literature reveals that some confusion exists concerning the terms "atrophy" and "osteolysis", and an attempt is made to distinguish between them.
Whilst the special anatomical features of the mandible may make radiographic comparison of jaw lesions with similar conditions in other bones more difficult, the changes that occur in respect to the mandibular canal and the teeth may in themselves aid diagnosis. Benign cysts and neoplasms generally cause a displacement of the mandibular canal, but its cortical plate remains intact, Severe infections and malignant tumours result in an irregular erosion of bone and loss of the sclerotic outlines of the canal.