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At least 1,405 records · Page 78Linked to original sources
PubMed1994

Mandible preservation in cancer of the floor of the mouth. Anatomical and oncological considerations.

An extended marginal mandibulectomy can be performed in most T2-T3 carcinomas of the floor of the mouth that abut the anterior mandible if there is no radiologic evidence of bony invasion or clinical evidence of fixation. We propose a modification of the marginal mandibulectomy that maintains viability to the anterior mandibular remnant and thus decreases the morbidity associated with a loss of blood supply. This modification permits preservation of a viable mandibular remnant with significantly less loss of function than with the traditional segmental mandibular resection, while remaining oncologically sound.

Adult↗
PubMed1996

Cross-sectional geometric properties of the Otavipithecus mandible.

Cross-sectional geometric properties of the postcanine mandibular corpus are determined for the only known specimen of Otavipithecus namibiensis, a middle Miocene hominoid from southern Africa. It is shown that Otavipithecus is unique in that several important mechanical properties of its mandible, including maximum and minimum moments of inertia and distribution of cortical bone, differ from patterns seen in both extant hominoids and the early hominids Australopithecus africanus and Australopithecus (Paranthropus) robustus. This is particularly apparent in the mechanical design of the posterior portion of the mandibular corpus for resisting increased torsional and transverse bending moments. Cortical index values at the level of M2 also reveal that both Otavipithecus and A. africanus are similarly designed to resist increased masticatory loads with relatively less cortical bone area, a highly efficient mechanical design.

Africa, Southern↗
PubMed1998

Bone response to unloaded and loaded titanium implants with a sandblasted and acid-etched surface: a histometric study in the canine mandible.

Many dental clinical implant studies have focused on the success of endosseous implants with a variety of surface characteristics. Most of the surface alterations have been aimed at achieving greater bone-to-implant contact as determined histometrically at the light microscopic level. A previous investigation in non-oral bone under short-term healing periods (3 and 6 weeks) indicated that a sandblasted and acid-etched titanium (SLA) implant had a greater bone-to-implant contact than did a comparably-shaped implant with a titanium plasma-sprayed (TPS) surface. In this canine mandible study, nonsubmerged implants with a SLA surface were compared to TPS-coated implants under loaded and nonloaded conditions for up to 15 months. Six foxhound dogs had 69 implants placed in an alternating pattern with six implants placed bilaterally in each dog. Gold crowns that mimicked the natural occlusion were fabricated for four dogs. Histometric analysis of bone contact with the implants was made for two dogs after 3 months of healing (unloaded group), 6 months of healing (3 months loaded), and after 15 months of healing (12 months loaded). The SLA implants had a significantly higher (p < 0.001) percentage of bone-to-implant contact than did the TPS implants after 3 months of healing (72.33 +/- 7.16 versus 52.15 +/- 9.19; mean +/- SD). After 3 months of loading (6 months of healing) no significant difference was found between the SLA and TPS surfaced implants (68.21 +/- 10.44 and 78.18 +/- 6.81, respectively). After 12 months of loading (15 months of healing) the SLA implants had a significantly greater percentage (p < 0.001) of bone-to-implant contact than did the TPS implants (71.68 +/- 6.64 and 58.88 +/- 4.62, respectively). No qualitative differences in bone tissue were observed between the two groups of implants nor was there any difference between the implants at the clinical level. These results are consistent with earlier studies on SLA implants and suggest that this surface promotes greater osseous contact at earlier time points compared to TPS-coated implants.

Acid Etching, Dental↗
PubMed1992

Short stature, Robin sequence, cleft mandible, pre/postaxial hand anomalies, and clubfoot: a new autosomal recessive syndrome.

We report on 5 unrelated Brazilian children with short stature, Robin sequence, cleft mandible, pre/postaxial hand anomalies, and clubfoot. Genetic aspects and phenotypic manifestations are compared with those of previous reports of acrofacial dysostoses and with other Robin sequence syndromes. We suspect that these patients present a previously undescribed autosomal recessive syndrome.

Abnormalities, Multiple↗
PubMed2002

A blind test of mandibular morphology for sexing mandibles in the first few years of life.

Loth and Henneberg ([2001] Am. J. Phys. Anthropol. 115:179-186) proposed that consistent shape differences exist between male and female juvenile mandibles which can be used to predict sex with an accuracy of 81%. A sample of known sex and age from the Spitalfields Collection was examined blind twice and resulted in an overall accuracy of only 64%. The tests also showed that: 1) the method sexed males more reliably than females; and 2) consistency was low.

Female↗
PubMed2003

Functional significance of cortical bone distribution in anthropoid mandibles: an in vitro assessment of bone strain under combined loads.

Local variation in cortical bone thickness in the postcanine mandibular corpus appears to be stereotypical among anthropoids. Specifically, at sections under the molars, lingually situated cortical bone is typically thinner than that along the lateral aspect. This pattern applies despite phylogenetic, dietary, and allometric differences among the anthropoids sampled to date. Demes et al. (Food Acquisition and Processing in Primates [1984] New York: Plenum Press, p. 369-390) employed a theoretical analysis of mastication in Gorilla and Homo to argue that this pattern could be explained with reference to biomechanical stresses. Specifically, they proposed that the combined effects of torsion and direct shear on the working-side corpus create a condition in which net stresses and strains are reduced along the lingual cortical plate. Demonstration of this effect would suggest a functional linkage between localized differences in bone mass and strain gradients in the facial skeleton. We conducted an empirical evaluation of the effects of the combined loads of torsion and direct shear in vitro on a sample of formalin-fixed human mandibles. Rosette strain gages were affixed to the lateral and medial aspects of the corpus in each specimen, and surface strains were recorded separately under controlled torsional and occlusal loads, and under simultaneous application of these loads. The hypothesis that lingual strains are reduced under combined twisting and occlusal loads was generally supported; however, we observed reduction in surface strains at some sites along the lateral aspect of the corpus under these combined loads as well. These unexpected findings are attributable to unanticipated loading conditions imposed by occlusal forces, which result from sources of stress in addition to direct shear. These experiments provide provisional support for the hypothesis that superposed sources of bone strain produce large strain gradients between buccal and lingual aspects of the mandibular corpus, and that local variation in bone mass may be associated with these gradients.

Animals↗
PubMed1977

Split-line patterns of the mandible following masseterectomy in adult and growing monkeys.

Architectural changes of the mandibular ramus following masseterectomy were analyzed by means of the split-line technique in both adult and growing monkeys. The right masseter muscle was resected in ten tufted capuchin monkeys (Cebus apella) and they were sacrificed following a 12-month period. Along with modifications in the shape of the mandible, the masseterectomy induced structural changes as revealed by alterations in the split-line patterns. These changes were much more evident in the adult animals. In growing monkeys, intrinsic forces determine an architecture of mandibular growth, represented by the direction of the splits. This is not influenced by the lack of mechanical factors like muscle action. Conversely, the final fibrous architecture of the bone in the adult monkey may be modified by extrinsic mechanical factors.

Age Factors↗
PubMed1983

Alveolar dehiscences and fenestrae in dried South African Negro mandibles.

The buccal and lingual roots of 1077 teeth from 100 mandibles of South African Negroes were examined for the presence of dehiscences and fenestrae. All specimens were obtained from cadavers of known sex, tribe, and stated age; 10.5% of teeth were affected. Canines and first premolars were the most common teeth associated with dehiscences and fenestrae. Dehiscences occurred more commonly than fenestrae (1:0.49). The defects were found exclusively in the buccal plate of the alveolar process.

Adult↗
PubMed1986

Nonlever action of the mandible.

This study considers the current concept of the mandible as a lever of the third order. The concept requires a fulcrum, and this function has been ascribed to the condyle region, but it tends to be overlooked that the fulcrum of a third-order lever in this case would sometimes have to bear a considerable stress. Certain changes, attributed to stress, have been observed in anatomical components of the articulation, but they cannot be explained in terms of the lever concept. They are accounted for by the changing anatomical relations in the working and contralateral sides during mandibular function. They arise from minor stress, especially when dental conditions indicate a period of abnormal function.

Biomechanical Phenomena↗
PubMed1987

Retromolar foramen of the human mandible.

Analysis of retromolar foramen (RMF) in a large series of mandibles (N 2500) was undertaken to provide descriptive statistics for this variant. RMF of diameter 0.5 mm or greater were scored. Consistent with other data on accessory canals in the facial skeleton, RMF was found to occur more commonly in native populations of North America than in other populations (Africa, Europe, India, northeast Asia). The ratio of bilateral to unilateral occurrences was shown to increase with population incidence, a pattern consistent with the theoretical model of an epigenetic (threshold "quasicontinuous") variant. Male-female differences were not found. Age profiles were characterized by a marked peak in the adolescent cohort. In some populations RMF showed a positive intertrait correlation with accessory mandibular foramen and with accessory mental foramen, but correlations with presence/absence of third molar and three-rooted first molar were not found. With refinements in scoring criteria and, ideally, better evidence of its heritability, RMF should be useful along with other minor cranial variants for ethnohistorical studies.

Adolescent↗
PubMed1993

Mandible of Ouranopithecus macedoniensis (Hominidae, Primates) from a new late miocene locality of Macedonia (Greece).

In 1990, a new late Miocene locality named "Nikiti 1" or NKT, was discovered near the village of Nikiti (Chalkidiki, Macedonia, Greece) about 100 km east of Thessaloniki City. The locality is situated in the Nikiti Formation, which consists of yellowish sands, gravels and pebbles and has been dated to late Vallesian-early Turolian. Among the initially collected fossils there is a mandible of a hominoid primate, which is described, compared, and attributed to Ouranopithecus macedoniensis. A short review of the species in Macedonia and its phylogenetic relationships are also given.

Animals↗
PubMed1985

Ultrasonic microdissection of the mouse mandible: exposure of the vasculature of alveolar bone and myelinated axons of the pulp.

The present scanning electron microscopic study describes a new method for the exposure of blood vessels of mouse alveolar bone and myelinated nerves of the dental pulp. This technique differs from others because it does not remove the periodontal ligament, allowing study of the vascular continuity between alveolar bone and periodontal ligament. Fixed and demineralized mandibles are digested with bacterial collagenase (1 mg/ml) at 37 degrees C for 12 hours, exposed to buffered osmium tetroxide for 24 hours, and ultrasonicated at 80 kHz for 5 minutes. The technique demonstrates that the vascular distribution of the interdental and interradicular septa is different. Vessels pass horizontally through the interdental septum and are continuous with vessels of the adjacent periodontal ligament. Vessels of the interradicular septum branch from a central vessel, pass toward the adjacent periodontal ligament, and become continuous with its vessels. Thus, the pattern of vessel distribution of the interdental septum of the mouse has little similarity to that of man or of research animals. The present study provides an improved method for demonstration of bone vasculature and pulpal axons while retaining valuable anatomical landmarks.

Alveolar Process↗
PubMedDate not supplied

DentaScan imaging of the mandible and maxilla.

DentaScan is a unique new computer software program which provides computed tomographic (CT) imaging of the mandible and maxilla in three planes of reference: axial, panoramic, and oblique sagittal (or cross-sectional). The clarity and identical scale between the various views permits uniformity of measurements and cross-referencing of anatomic structures through all three planes. Unlike previous imaging techniques, the oblique sagittal view permits the evaluation of distinct buccal and lingual cortical bone margins, as well as clear visualization of internal structures, such as the incisive and inferior alveolar canals. Several case reports are presented to demonstrate the clinical usefulness of DentaScan.

Adult↗
PubMedDate not supplied

Trapezius osteomyocutaneous island flap for reconstruction of the anterior floor of the mouth and the mandible.

The anterior mandible defect following cancer excision presents a formidable reconstructive challenge. A trapezius osteomyocutaneous island flap based on the transverse cervical vessels is described which allows immediate reconstruction of the entire defect. The various classes of bone flaps retaining an intact vascular pedicle are discussed. The osseous extension of the trapezius island flap appears to be adequate perfused. The anatomy involved and the orthopedic sequelae of using flap are discussed.

Arteries↗
PubMedDate not supplied

Spread of squamous cell carcinoma to the nonirradiated edentulous mandible--a preliminary report.

The changes in the mandible and in its relationship to surrounding soft tissue structures after loss of the teeth are described; the regular presence of deficiencies in the cortical bone along the line of the occlusal ridge is emphasized. Resection specimens of squamous carcinoma of the oral cavity not treated by radiotherapy were examined where there was mandibular involvement by tumor, and showed that the main route of tumor entry into the bone was through the occlusal ridge. Subsequent perineural spread along the inferior alveolar nerve has been found to be a regular occurrence.

Alveolar Process↗
PubMed2003

Biological performance of biomimetic calcium phosphate coating of titanium implants in the dog mandible.

The aim of the present study was to analyze the in vivo effect of biomimetic calcium phosphate coating of titanium implants on periimplant bone formation and bone-/implant contact. Five types of implants were used: 1) Ti6Al4V implants with a polished surface; 2) Ti6Al4V implants with collagen coating; 3) Ti6Al4V implants with a mineralized collagen layer; 4) Ti6Al4V implants with sequential coating of hydroxyapatite (HA) and collagen; and 5) Ti6Al4V implants with HA coating only. All implants had square cross sections with an oblique diameter of 4.6 mm and were inserted press fit into trephine burr holes of 4.6 mm in the mandibles of ten beagle dogs. The implants of five animals each were evaluated after a healing period of 1 month and 3 months, respectively, during which time sequential fluorochrome labeling of bone formation had been performed. Bone formation was evaluated by morphometric measurement of the newly formed bone around the implants and the percentage of implant bone contact. After 1 month, there was a significantly higher percentage of mean bone/implant contact in the HA-coated implants compared to those with polished surface and those with the collagen-coated surface. After 3 months, these differences were not present anymore. Bone apposition was significantly higher next to implants with sequential HA/collagen coating compared to polished surfaces and mineralized collagen layer. It is concluded that biomimetic coating of titanium implants with HA has shown the clearest trend to increase bone-implant contact in the early ingrowth period. The addition of collagen to an HA coating layer may hold some promise when used as sequential HA/collagen coating with mineralized collagen as the surface layer.

Alloys↗
PubMed2006

Healing pattern of bone defects covered by different membrane types--a histologic study in the porcine mandible.

Few investigations on guided bone regeneration (GBR) focus on the behaviour of tissues adjacent to barrier membranes. This study was conducted to (1) evaluate the barrier function potential of different resorbable and nonresorbable membranes for GBR, (2) investigate their structural changes after different intervals, and (3) characterize tissue composition and reaction adjacent to the barrier by qualitative histologic evaluation. Seven barriers for GBR were used per animal (made of dense or expanded polytetrafluoroethylene (d/ePTFE), titanium, polyetherurethane, collagen and two polylactide-polyglycolide-/-trimethylenecarbonate-co-polymers (PLPG, LPGTC) in standardized defects not exceeding the critical size) without using bone substitution material or autogenous bone at the right inferior margin of the mandibles of six domestic pigs. Samples of the defect areas with membranes were harvested after 2 days (one animal), 4 and 8 (two animals, each) and 12 weeks (one animal), respectively. The healing of bone defects was completed in all animals after 12 weeks. Nonresorbable barriers prevented the soft tissue in-growth into standardized defects. Thinner layers of fibrous tissue were seen underneath the dense and rigid barriers (dPTFE, titanium) when compared with collagen and PLPG/LPGTC, in which soft-tissue plugs occupied the crestal defect portion. PLPG-/LPGTC-barriers underwent structural changes after 4 weeks and revealed blistered central layers, whereas structural changes were not evident in nonresorbable barriers. The degradation of PLPG-/LPGTC-membranes was present with in-growth of fibres, vessels, and cells. Using collagen or synthetic polymer barriers for GBR, the application of bone or bone substitutes to prevent membrane prolapse into the defect is suggested.

Animals↗