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Biomedical subjects

C L Lavelle

Publications and source records attributed to C L Lavelle.

At least 19 recordsLinked to original sources
PubMed1992

Diagnosis of skeletal form on the lateral cephalogram with a finite element-based expert system.

Orthodontic diagnosis depends largely on the current methods of cephalometric analysis and categorization. It is therefore unfortunate that such analyses tend to use inappropriate metrical systems that lack a rigorous scientific basis. As a consequence, the resultant data have questionable validity, as well as being subject to observer bias. In this study, an alternative, more rigorous, approach is described. A random sample of 126 pretreatment lateral cephalograms were analyzed with the finite element method. These data were then classified to form a training set or reference data base for the subsequent objective diagnosis of new, previously unclassified cases. This new case-classification system was based on matching the new cases to similar cases within the existing training set. The degree of concordance between such computer-matched cases was then evaluated by their subsequent conventional cephalometric analyses.

Adolescent↗
PubMed1992

A preliminary study of craniofacial classification.

Cephalographic evaluations often hinge on univariate statistical analyses of their component dimensions. These analyses generally depict a progressive increase in cephalometric form with age. Such analyses are, however, complicated by the varied inter-dimensional correlations. But when the cephalometric dimensions were combined together in cluster analysis, complex associations between various age groups were noted in the 1-18 year range. Such multivariate analyses revealed far more complex craniofacial age changes than traditionally envisaged. These data therefore indicated the need for further investigation of such "normocephalic gold standards" before their value in craniofacial evaluation can be established.

Age Factors↗
PubMed1990

Potential of finite element analysis for cephalometric investigation.

In view of concerns relating to the validity of traditional cephalometric appraisals, we undertook this study to use a potentially powerful method, finite element analysis, to compare cephalometric changes between two samples (subjects with and without orthodontic treatment). The derived data show varying sample contrasts depending on the particular finite element array included in the analysis. Thus, although finite element analysis facilitates rigorous morphometric analysis, further investigation is required before it can be applied universally in cephalometric studies.

Adolescent↗
PubMed1989

An evaluation of the changes in soft-tissue profile form induced by orthodontic therapy.

In view of the growing concensus that traditional cephalometric appraisals yield data of dubious scientific value, the changes in soft-tissue profile forms were evaluated by an alternative technique. This involved dividing the soft-tissue profile form into a series of triangular finite elements spanning homologous datum points. With the use of techniques derived from continuum mechanics, the changes in soft-tissue profile form were evaluated by computing the degree of distortion in each triangle after treatment (target element) compared with the triangle before treatment (reference element) in terms of specific size and shape parameters. In a comparison of samples of patients with Class I and II malocclusion, varying patterns of facial profile change were noted, depending on the parameters analyzed. The results, therefore, showed that although such techniques offer rigorous cephalometric potential, further investigation is required to identify more appropriate datum points.

Cephalometry↗
PubMed1989

The role of cluster analysis on traditional cephalometric dimensions.

In order to categorize (classify) craniofacial forms, varying linear dimensional arrays from a series of pretreatment cephalographs ('A' records) were subjected to cluster analysis. The derived subgroups (clusters) not only showed inconsistencies in their component patients, but also their 'nearest neighbors', i.e. cases identified as being most similar to one another. This study, therefore, emphasized the need to devise more appropriate cephalometric appraisal techniques for patient categorization (diagnosis).

Adolescent↗
PubMed1989

An evaluation of conventional cephalometric appraisals.

Although lateral cephalographic diagnosis is central to craniofacial skeletal assessment, their classification (categorization) remains largely empiric. In this study, pre- and post-treatment lateral cephalographic dimensional arrays were subjected to the classic numerical taxonomic technique of cluster analysis. The resultant patient groupings (clusters) were not only inconsistent with respect to their Angle malocclusion categories, but also the composition of each cluster group varies depending upon the dimensional arrays analyzed. These findings demonstrate that lateral cephalometric categorization remains largely subjective.

Adolescent↗
PubMed1989

Statistical methodology applied to facial studies.

The majority of cephalometric studies of anomalous craniofacial taxonomy and evaluation is based upon either isolated cases or methods that cannot withstand rigorous scientific scrutiny. A number of techniques have been devised to resolve such deficiencies, although the image quality of lateral cephalographs limits the precision of their measurement. Thus, further advances in the statistical evaluation of anomalous craniofacial forms hinge upon the acquisition of more precise images.

Cephalometry↗
PubMed1988

Detection of three-walled infrabony defects by subtraction radiography.

An in vitro investigation was undertaken to establish the sensitivity of subtraction radiography for three-walled infrabony defect detection. After the creation of defects of controlled sizes in the interproximal regions of a dried mandible, subsequent radiographs were taken with the help of an occlusal stent. The radiographs were then digitized, and the images were enhanced by frame summation and averaging to reduce electronic noise. Further standardization was facilitated by the use of a step wedge on each radiograph and a computer program to correct variations in processing and exposure. The results show that defect resolution depended not only on the diameter of the defect but also on the mass of the adjacent bone. The smallest detectable lesion was 0.5 mm in diameter in the interproximal region of the premolars. In addition, a change in depth of 1 mm could be detected at the base of three-walled infrabony defects.

Alveolar Process↗
PubMed1988

An analysis of craniofacial form in cleft palate patients.

Lateral cephalometric form was compared between age-sex matched cleft palate and normocephalic (control) samples aged 6-12 years. Analogous arrays of 3 cephalometric datum points were subjected to finite element analysis, a rigorous geometric technique. The results showed that normocephalic craniofacial size changes were greater than those of the cleft palate sample, although the degree of contrast varied depending upon the particular finite element included in the analysis. More complex lateral cephalometric shape changes were denoted by this technique, however, again depending upon the specific finite element included in the analysis. These data therefore suggested that the differences in craniofacial size and shape changes between normocephalic and cleft palate patients were far more complex than traditionally envisaged.

Cephalometry↗
PubMed1988

An analysis of orthodontically induced changes in craniofacial form.

Traditional cephalometric analyses facilitate only cursory craniofacial evaluation. When a more rigorous geometric technique, in the form of finite element analysis, was applied to a retrospective series of lateral cephalographs taken before and after the completion of the orthodontic therapy, however, complex craniofacial size and shape changes were apparent. Such complexities could not have been detected from conventional cephalographic appraisal.

Adolescent↗
PubMed1988

A statistical approach to the discrimination of the cranial form.

In a study of lateral cephalographic dimensions, their multivariate statistical analysis was shown to discriminate between patients with gross cranial anomalies and controls exhibiting no abnormal morphology. Although the degree of discrimination depended upon the group of dimensions included in the analysis, discrimination was more consistent than when compared using univariate statistical techniques. As cephalographic dimensions combine both size and shape parameters together, however, the interpretation of such contrasts must await more specific analytic techniques development.

Cephalometry↗
PubMed1986

A preliminary craniofacial profile evaluation of normo-, micro- and macro-cephalics.

In order to investigate the metrical definitions of the craniofacial skeleton, lateral cephalographs were defined by 120, 351 or 14,535 linear dimensions. When these dimensions were combined together by multivariate statistical techniques, the degree of discrimination between normo-, micro- and macro-cephalics was found to vary, depending upon the actual metric craniofacial definition included in the analyses. This study therefore indicated the need for further research before definitive comparisons of lateral cephalographs can be formalized.

Adolescent↗
PubMed1979

A study of craniofacial form.

There are differences in the craniofacial skeleton, dental arch, and tooth dimensions between brachycephalics and dolichocephalics. Furthermore, the craniofacial complex appears to be more intergrated biologically in dolichocephalics than brachycephalics.

Adolescent↗