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Biomedical subjects

R E Moyers

Publications and source records attributed to R E Moyers.

At least 19 recordsLinked to original sources

An inventory of United States and Canadian growth record sets: preliminary report.

A listing and description of longitudinal craniofacial growth record sets currently extant on the North American continent is provided. An argument is made for the preservation of these resources and for the generation of a pooled or shared image base of duplicate craniofacial physical records. This is a preliminary report and is assumed to be incomplete. In an effort to improve our accuracy and completeness, we invite corrections and additions.

Adolescent

Frontal cephalometric evaluation of transverse dentofacial morphology and growth of children with isolated cleft palate.

The transverse dentofacial morphology and growth of 64 children operated on for clefting of the hard and soft palate was studied by means of a frontal proportional cephalometric analysis and was compared to a normal sample at the ages 3-4, 8-9 and 12 years. The cross-sectional comparison of the cleft palate and normal samples at the three periods indicated: (a) The presence in the cleft group of significantly increased ratios of the inner orbital width to the interorbital width and of the width of the nasal cavity to the interorbital width; (b) the absence of any significant differences in the ratio of the maxillary intermolar width to the interorbital width; and (c) the presence of almost identical ratios of the intergonial width of the mandible to the interorbital width and of the width of the maxilla to the intergonial width of the mandible. Evaluation of the changes of all cephalometric variables during the period 8-12 years showed the absence of any significant difference between the cleft palate and normal groups.

Age Factors

Imprecision and bias in orthodontic treatment results.

Imprecision in treatment response has been defined as inconsistent unpredictable results from the same treatment. Bias has been defined as systematic failure to achieve defined treatment goals. Concepts of imprecision and bias are applied to the results of a study of soft-tissue response to Class II treatment with edgewise and Herbst appliances.

Clinical Protocols

Do horizontal growers grow horizontally?

It is common to analyse the growth direction of the facial skeleton by registering serial lateral cephalograms on Sella and orienting along Sella-Nasion. The present paper reports an exercise in cephalometric growth analysis by an alternate method the study of mean growth tensors. The authors conclude that conventional cephalometric techniques are inadequate for precise analysis and practical prediction of craniofacial change and that cephalometrics should proceed independently of any orientation or registration at all, with analyses following from the phenomenon, not preceding it.

Adolescent

Differential diagnosis of class II malocclusions. Part 1. Facial types associated with class II malocclusions.

By means of computer-based statistical methods, several types of Class II malocclusion have been discovered with defining horizontal and vertical characteristics. Of the six horizontal types, four are severe syndromes, one is a loose, ill-defined grouping of cases with mild skeletal features, and one has only the dental features of Class II. Five vertical types associates with Class II were also revealed, although each vertical is not associated with all horizontal types. A simplified simulation of the computerized procedures has been developed for routine use in clinical practice.

Child

The inappropriateness of conventional cephalometrics.

1. Cephalometric conventions today may have little basis in either biology or biometrics. 2. There is no theory of cephalometrics, only conventions which involve landmarks and straight lines only. These fail to capture the curving of form and its changes, exclude proper measures of size for bent structures, and misrepresent growth, portraying it as vector displacement rather than a generalized distortion. 3. Conventional cephalometric procedures misinform by fabrication of misleading geometric quantities, by camouflage, particularly of remodeling, by confusion about what is happening (analysis of rotations, treating shape separately from size, and registering angles on landmarks as vertices), and by subtraction as a representation of growth. 4. We suggest that the present systems offer little real hope of improvement sufficient to meet our needs in craniofacial growth research. We call attention to three possible techniques to be included in future cephalometric conventions: (1) tangents and curvatures, (2) Blum's medial axis ("skeleton"), and (3) biorthogonal grids.

Biometry

The concept of pattern in craniofacial growth.

1. There are semantic and associated problems with the word pattern in biology, particularly in orthodontics and facial growth. 2. Pattern, as we use the term, is invariance of relationships--"a set of constraints operating to preserve the integration of parts under varying conditions and through time." 3. Craniofacial pattern can be described and quantified by the identification of craniofacial constants, measures that are relatively invariant. 4. Growth is change and is best identified by studying those measures of size and shape that vary most sensitively through time over development stages. 5. The many traditional cephalometric measures that represent well neither pattern nor growth (mixed) are of less clinical utility than either pure pattern indices or growth indices. 6. The analytical and conceptual separation of pattern and growth seems useful in analysis of morphology, analysis of growth, prediction of growth, and clinical treatment planning.

Adolescent