Mandibular Basal Bone Research Articles

The human chin and its relationship to mandibular morphology.

This study evaluated the proportion of the external chin (protuberantia mentalia) in relation to the total symphyseal area in normal jaws and those with a diverse morphology. A sample of 60 cases was randomly selected and divided into three groups of 20 each on the basis of normal growth, horizontal growth and vertical growth with an open bite. Tracings of lateral dn frontal radiographs were used to describe general mandibular form and to determine the percentage of external/total symphyseal area. Dental casts were also examined to determine a basal arch form ratio. The results of this study indicate that the amount of bony chin present is related to certain morphologic features of the mandible. The most significant findings illustrate: 1. The chin increases in size as the mandibular type varies from a vertical type, to a normal type, to a horizontal type of growth pattern. 2. With dental "hypofunction" in combination with an exaggerated vertical development of the mandible, a smaller proportion of the protruding chin is present. 3. The chin increases in size as the mandibular basal arch form varies from a tapered shape for the vertical cases to a more square form in the horizontal cases. 4. The degree of lateral ramal flair does not appear to influence the proportion of protruding chin present. Several models have been presented which attempt to explain protuberantia mentalia variation. The evidence in this study supports the concept that mandibular morphology is the result of the action of compensative adaption in a developing structure. There appears to be an implied polygenic influence on symphyseal morphology operating from the cartilaginous cranial base and mandibular basilar bone. This may be manifested in the relative proportion of mandibular basal bone to cranial base width, and to the vector of cranial base growth. The ultimate proportion of the bony chin is viewed to be the result of mandibular adaption to a functional musculoskeletal balance in the craniofacial complex. The extreme variability of chin form in man may be considered to be the result of compensative growth developing in response to the most structurally efficient jaw form, the contiguous soft and hard tissue environment, and the intrinsic genotype of the mandible.

Blood flow measurements in selected oral tissues in dogs using radiolabelled microspheres and rubidium-86

Radiolabelled microspheres and 86Rb were used in dogs to measure oral tissue blood flow. The tissues studied were mandibular alveolar and basal bone, oral mucosa, gingiva, lip, tongue and soft tissue of hard palate. A suspension of 6 × 10 6 cerium-141 labelled microspheres, 15 ± 5 μm in diameter was injected into the left ventricle through an arterial catheter in 9 healthy adult dogs. Cardiovascular stability was assessed during the catheterization and injection of microspheres. Following the microsphere injection, 500 μCi of 86Rb was injected intravenously and the animal was killed within 60s. Blood flow measured using 86Rb was not significantly different ( p > 0.05) from radiolabelled microsphere flow in mandibular basal bone, oral mucosa and gingiva, suggesting that in these oral tissues nutritional or capillary exchange flow is similar to total blood flow. In mandibular alveolar bone, lip, tongue and soft tissue of hard palate, however, 86Rb measurements were significantly greater ( p < 0.05) than microsphere measurements. The combined use of radiolabelled microspheres and 86Rb shows promise for continued studies of blood flow in healthy and pathological oral tissues.

Changes in human mandibular structure with age

Information is presented about osteoporosis of the mandibular bone with ageing. Porosity was observed to increase with age and was assessed by two procedures: ( a) by measuring the area of space seen in histological sections, and ( b) by determining the density of small blocks of bone. Of the two procedures, pyknometry proved to be more suitable for assessing porosity of smaller samples from the alveolar crest and was used in a more detailed study. Porosity was found to vary, but was usually more pronounced in alveolar bone than in mandibular basal bone. An unexpected finding was that the distribution of porosity bore little relation to tooth loss or crest recession. This ageing process followed a pattern which appeared to be related to bone resorption during development.

The length of mandibular basal bone in normal occlusion and Class I malocclusion compared to Class II, Division 1 malocclusion

T HE general purpose of this study is to compare the length of the mandibular basal bone for individuals having normal dentofacial relationships (normals and Class I malocclusions) with that of individuals exhibiting a distal relationship of the mandibular arch to the maxilla (Class II, Division 1, Angle). Orthodontic investigators aild practitioners are fairly well agreed that the abnormality present in Class II, Division 1 malocclusion lies principally in the mandible. It has not been established to what extent (1) the ramus height or tbe basal bone length may be deficient, (2) the gonial angle may be too acute, (3) the condyle may be positioned distally to normal in the glenoid cavity, ,(4) the teeth may be positioned distally on the rnandibular basal bone, or (5) there may be a lack of vertical growth of the temporal bone in which the condylar fossa is located. This investigalion is concerned with the extent to which the observed mandibular retrusion is associated with the anteroposOerior length of the mandibular body. It is for other investigators to establish the significance of the additional factors listed. The literature on this subject reveals many references to the lack of mandibular development found in this class of malocclusion. Apparently, there has been some disagreement as to the specific center of growth which has been upset causing the retrusive position of the mandible. Angle1 evidently considered, from his clinical observations, that it was an over-all lack of growth of the bone. He stated, “The mandible is also distal (in Class II, Division 1) in its relation to’ the maxilla and usually smaller that] normal but quite normal in form.” He did recognize exceptions to this in his last etlition. This quotation is taken from the chapter, “Facial Art” :