An assessment of posture in bipedal rats.

Alteration in posture was examined following foreleg amputation in rats. After the surgical induction of bipedal stance, a detailed, quantified, and longitudinal assessment of rat posture and the amount of time spent in the upright stance was undertaken. An experimental group of rats had both forelimbs amputated. A group of unaltered quadrupedal rats served as controls. A standardized series of photographs of altered and control rats was taken. Postural differences between the two groups of rats were analyzed through photographic analysis of their profiles in upright and in crouched positions. Analysis of the photographs showed that the percentage of rats assuming upright posture did not differ between the experimental and control groups. Foreleg amputation forced the rats to adopt an altered posture, but did not result in habitual assumption of upright stance to a greater degree than that of controls. Adaptation to bipedalism was marked by a tucking of the hindlimbs under the body, and a flexure of the vertebral column and the head.

Diagnosis and treatment of class II division 2 malocclusion.

Class II, Division 2 malocclusions often have skeletal patterns more nearly approaching Class I than Class II, Division I. Incisor relationships are unique. Treatment problems related to this malocclusion require that the clinician pay particular attention to the vertical dimension. Also, the prevalence of mandibular movement pattern irregularities, coupled with the "droopy incisor" phenomenon so characteristic of this malocclusion, requires careful individual case analysis. The use of simplified initial appliance mechanics to rectify some of these problems is discussed.

Dimensional changes in the dental arches of orthodontically treated cases.

Integrated data from lateral cephalometric radiographs and study models of fifty-three patients were studied to assess the interactions between dimensional changes occurring during orthodontic treatment and the postretention stability of these changes. A new technique was developed to study distal movement of canines. Distal movement of canines did not ensure a stable increase in intercanine width. There was no significant relationship between mesiodistal position of the first molars and changes in intermolar width. Eruption of the first molar in the postretention period was associated with greater stability in overbite. There was no great degree of correlation between depth of the curve of Spee and inclination of the occlusal plane or between changes in arch length and changes in inclinations of the incisors.

A computer program for the analysis of dental models.

This paper presents the details and logic of a Fortran computer program which carries out routine clinical analysis of dental models resulting from impressions of the teeth and related structures, which are subsequently cast in plaster of Paris. The program is primarily intended for use by the orthodontist who is engaged in research or clinical practice, and is useful in studies related to changes in the dentition as a result of orthodontic treatment.

Craniofacial morphology: a principal component analysis.

A series of 56 measurements was derived from lateral cephalometric radiographs of a large sample of subjects. These measurements were subjected to a principal-component analysis which resulted in a series of six components (factors). These factors, represented in general terms and in rank order of their percentage sample variability were as follows: Factor 1. Vertical facial characteristics Factor 2. Anteroposterior aspects of facial morphology Factor 3. Midfacial and dental protrusion Factor 4. Relationship of the mandible and dentition to the profile Factor 5. Horizontal base-line relationships (internal or deep) Factor 6. Maxillary incisor relationships These principal components and the variables contained within them were shown to have sex and age interactions. A longitudinal study of the principal component changes with age was then undertaken. Demonstrable age changes were verified for Factors 1, 2, and 3, and Factors 1 and 3 were observed to show patterns of change which were statistically different from each other and the remaining principal components. An orthodontically treated sample of patients was also assessed for factor changes. Factors 1 and 2 were found to show statistically reliable changes resulting from treatment and/or growth. The remaining four factors showed no statistically supportable alteration. The data-reduction method involving a principal-component analysis would seem to have potential research and clinical applications.