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Biomedical subjects

M L Moss

Publications and source records attributed to M L Moss.

At least 55 records · Page 3Linked to original sources
PubMed1985

Finite element method modeling of craniofacial growth.

The application of the concepts of continuum mechanics and of the numerical techniques of the finite element method permits the development of a new and potentially clinically useful method of describing craniofacial skeletal growth. This new method differs from those associated with customary roentgenographic cephalometry in that its descriptions and analyses are invariant; that is, they are independent of any method of registration and superimposition. Such invariance avoids the principal geometric constraint explicit in all analytical methods associated with conventional roentgenographic cephalometry. The conceptual and mathematical bases of the finite element method (FEM) are presented and illustrated by the numerical and graphic descriptions of the two-dimensional growth of the rat skull, for which two sets of longitudinal growth data are used. In practice, the FEM permits analysis of the skull at a scale significantly finer than previously possible, by considering cranial structure as consisting of a relatively large number of contiguous finite elements. For each such element, independently, it is then possible to describe and depict both the magnitude and the direction of temporal size and shape changes occurring in that element relative to itself at some initial time. It is emphasized that such descriptions are completely independent of any local reference frame.

Aging↗
PubMed1985

The application of the finite element method to the analysis of craniofacial growth and form.

It has been shown previously that all customary methods of analysis of craniofacial skeletal growth, closely based on the techniques of roentgenographic cephalometry, share common geometric and conceptual constraints that make all such descriptions reference frame dependent; i.e., these descriptions vary with each method of registrations and superimposition (stacking) of growth cross-sections (x-rays). The use of the concepts of continuum mechanics, and of the numerical techniques of the finite element method, permit a reference frame invariant tensor description of growth. An example of this method is provided by the analysis of the growth of the rat neurocranium and maxillary complex in the period 13-49 days of age. The finite element method should find wide application in the description of cephalic growth, in normal and pathological conditions.

Animals↗
PubMed1985

Studies on orthocephalization. 8. Behaviour of the visceral part of the rat head in the period between 7 and 60 days after gestation.

The present paper considers the significance of interosseous flexions of the palatal complex in the process of orthocephalization of the rat skull between 7 and 60 d after birth. The study is based on a sample of 25 female rats who have been X-rayed at 7, 14, 30, and 60 d with subsequent analysis of the photographs obtained. During this period the constituents of the bony palate, i.e. the palatine bone, the palatal process of maxilla and the palatal part of premaxilla grow steadily but with decreasing rate of increase with age. The premaxilla grows the most, while the palatal bone grows the least. The angle between the cranial base and the palatal plane decreases, i.e. the rat skull becomes more orthocranial with age. At the same time, the palate becomes more orthopalatal, primarily by an increase in the angle between the palatine bone and maxilla. As the angle between the cranial base and the palatine bone after 14 d increases, i.e. rotates in the opposite direction of the palatal plane, it may be concluded that the process of orthocephalization in this period is caused by the deflexion of the angle between the palatine bone and maxilla, while it before 14 d is caused by a combination of an interosseous deflexion in the palate and an upwards rotation of the palatine bone relative to the cranial base.

Aging↗
PubMed1984

An allometric network model of craniofacial growth.

This study of cranial skeletal growth kinematics details the conceptual principles underlying the development of an allometric network model of such growth. This model is tested by the analysis of longitudinal rat and cross-sectional human growth data and by comparison of this model with a previously described allometric centered model. It is shown that the network model is superior to the centered model in three ways: (1) The allometric network model permits growth prediction when allometric constants are known; (2) the network model has significantly smaller errors than the centered model; and (3) the network model is capable of displaying growth kinematics of both the neural and facial skulls while in time there are marked transformations, such as relative rotations of two sets of cranial anatomic points.

Adolescent↗
PubMed1984

Hyperfunctioning cystic parathyroid glands: CT and sonographic findings.

Four functioning cystic parathyroid glands were evaluated with computed tomography (CT) and sonography in four patients, only one of whom had prior surgery. Sonography demonstrated solid lesions of decreased echogenicity with fluid-filled cavities near the lower thyroid poles or in the posterosuperior mediastinum. On CT the cystic parts of the lesions were of low attenuation (1-44 H), often with a well defined wall that was better demonstrated after intravenous contrast administration. Fine-needle aspiration biopsy of two of the cystic parathyroids revealed elevated parathyroid hormone levels. These lesions probably represent degenerating adenomas rather than true parathyroid cysts. While the CT and sonographic findings are nonspecific, the diagnosis of a cystic parathyroid should be entertained when a fluid-filled lesion is encountered in the neck of a patient with or without hypercalcemia. The diagnosis may be confirmed by assay of parathyroid hormone from the fluid aspirate.

Adenoma↗
PubMed1983

Statistical testing of an allometric centered model of craniofacial growth.

An allometric centered model of craniofacial growth was tested by several computer-assisted statistical methods on the pure longitudinal growth data of twenty-four close-bred female rats and on cross-sectional human cranial growth data. The study demonstrated that such a model was heuristic and, being incapable of exact definition, was deemed inappropriate for further use in modeling of craniofacial skeletal growth. The necessity for vigorous testing of any hypothesis concerning the modeling of craniofacial growth is stressed.

Adolescent↗
PubMed1983

The functional matrix concept and its relationship to temporomandibular joint dysfunction and treatment.

It is inappropriate for the nonclinician to qualitatively assess the several currently available therapies for treating TMJ dysfunction. However, it is pertinent to note that the matters reviewed in this article may assist the clinician by providing some deeper insights into the biomechanical bases of any successful therapy. TMJ dysfunction is a summary term for a broad spectrum of joint malfunctions, variously termed. These may be related to congenital, traumatic, pathologic, occupational, or psychologic factors. Similarly diverse are the symptoms of dysfunction at this joint, ranging from pain to structural disorder. The emphasis in this article on the role of mandibularly related muscles in the regulation of joint morphology and function may, with assurance, be extended to considerations of joint dysfunction. To the extent that TMJ dysfunction, in a specific patient, reflects dysfunction of the related functional matrix, then it would be correct to give consideration to directing therapeutic attention to these same muscles. Just as a skeletal unit can, and does, adapt both its structure and function to normal changes of its functional matrix, so a dysfunctional skeletal unit may confidently be adaptively return to normality following appropriate therapeutic alteration of the same matrix.

Biomechanical Phenomena↗
PubMed1982

Neuro-skeletal topology of the primate basicranium: its implications for the "fetalization hypothesis".

The data above, and the literature reviewed, demonstrate that in 4 significant morphological characteristics the neuro-skeletal topology of the human basicranial regions is unique, and does not resemble that of any extant non-human primate at any fetal or postnatal age. These characteristics are: 1. the shape of the cranial base; 2. the composition of the anterior and posterior portions of that base; 3. the extent, or degree, of basicranial flexion; and 4. the extent, or degree, of brain flexion. On these bases, the craniological implications of Bolk's fetalization hypothesis cannot be supported.

Animals↗
PubMed1981

Space-time presentations of the shell of the bivalved mollusk Cardium edule.

In a recent article the concept of studying craniofacial growth in space-time was introduced. The possibilities of carrying out such studies were demonstrated with the aid of some generalized shell of a bivalved mollusk. In this study presentations of space-time models of a real biologic model, the shell of the bivalved mollusk Cardium edule, have been constructed. Quantitative expressions of paths in space-time of anatomic and material points have been elaborated. A further analysis has shown that a number of the space-time presentations may represent biologic reality. They may be used for comparisons with presentations of skull models and may represent a tool for the better understanding of results from other studies.

Animals↗
PubMed1981

Studies on orthocephalization. VII. Behavior of the rat cranial frame in the period between 1 day before birth to 14 days after birth.

The positional stability of the zygomatic arch of the rat skull in relation to the parietal bone, the basisphenoid bone and the length axis of the skull, as previously demonstrated in rats older than 14 days, does not exist to the same degree in younger rats. These conclusions have been drawn from a study of a sample of rats, aged 0, 4, 7 and 14 days. These 4 groups of rats have been x-rayed after sacrifice, and from the x-ray photographs, quantitative expressions of angular values between the mentioned structures have been obtained. The most important result is, however, considered to be, that a full description of the behavior of the external cranial frame of the rat skull is now available for further studies on the process of orthocephalization.

Aging↗
PubMed1981

Studies on orthocephalization. 6. Flexions of the rat head in the period between 1 day before gestation and 14 days after gestation.

The present paper considers the significance of a variety of cranial flexions in the process of orthocephalization of the rat skull between 1 day before birth to 14 days after birth. The study is based on a sample of 95 albino rats divided into 5 age groups (1 day before birth - 0 days - 4 days - 7 days - 14 days after birth), who have been sacrificed and x-rayed with subsequent analysis of the photos obtained. Before x-raying, the rat heads have been treated with AgNO3 to improve the contrast of the bone images on the x-ray photos. In the period studied, the angle between the cranial base and the facial part of the skull becomes considerably more obtuse, i.e. the skull becomes considerably more orthocranial. As compared to the changes that have been shown in 14...60 days old rats, the changes in the early period are much more marked. The cranial vault in the young rats studied, also becomes flatter and more square, due to changes between the individual bones of the vault. This flattening is a significant part of the straightening of the rat skull as a whole, i.e. of the process of orthocephalization. In 14...60 days old rats the simultaneous size increase which primarily takes place in the bones of the facial skull reinforces an impression of marked orthocephalization. In the young rats of the present study, the size increase takes place both in the facial and in the cerebral part of the skull. The result of this leaves an impression of only moderate angular changes, although the changes are much more pronounced than in the older rats.

Age Factors↗