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At least 109 records · Page 6Linked to original sources
PubMed1984

The nasion-sella reference line in cephalometry: a methodologic study.

This investigation was undertaken to examine the effects of the registration error of the nasion-sella reference line (NSL) upon the values of angular and linear head film measurements. A comparison was made between two methods of constructing the NSL: (1) using the anatomically defined landmarks nasion and sella (L method) and (2) using the stable skull structures in the anterior cranial base (S method). Double registrations of sixteen pairs of lateral head films, from before and after 3 years of activator treatment, were performed by two observers. The results of the investigation revealed the following: (1) The registration error of the NSL affected angular and linear head film measures to a considerable degree. (2) The registration error was larger for the S method than for the L method. (3) The two observers differed in locating the NSL. The interobserver difference was especially apparent for the S method. The clinician should be aware of the NSL-registration error in the analysis of both single and serial radiographs. A misjudgment of the position of the reference line may result in diagnostic misinterpretations, thus affecting treatment planning or leading to false conclusions when the outcome of a particular treatment procedure is evaluated. In longitudinal studies covering a short period of growth, the L method would be the method of choice.

Adolescent↗
PubMed2000

An inference modeling of human visual judgment of sagittal jaw-base relationships based on cephalometry: part I.

When there appears to be a contradiction between a cephalometric tracing and what is seen, the clinician tends to place more reliance on the appearance of the face in profile than on a formal cephalometric evaluation of the sagittal jaw relationship. With this in mind, we derived a multiple regression model with cephalometric variables to explain the visual influences that affect the subjective classification of sagittal jaw relationships made by experienced orthodontists. The regression model that showed the highest coefficient of determination, 0.90, was constructed from a linear combination of the angle ANB, the anteroposterior position of gnathion, the SN length, and the mandibular body length. The performance reliability of the inference system has been tested for 175 female adult cases and will be reported in Part II of this article.

Adolescent↗
PubMed2000

An inference modeling of human visual judgment of sagittal jaw-base relationships based on cephalometry: part II.

In a clinical situation, visual judgment of sagittal jaw-base relationships is described and handled as fuzzy terms, such as "slight" skeletal 3 tendency or "relatively severe" skeletal 2. The purpose of this study was to develop an inference system in order to be able to describe the degree of certainty for sagittal skeletal discrepancy automatically and in a mathematical way. Orthodontic records of 137 adult female patients were judged by 3 orthodontists. Based on these data and the multiple regression model described in Part I of this study, we developed an inference system that consisted of 2 membership functions and 6 incorporating rules. The performance reliability of the system was tested for 175 female adult cases by 7 orthodontic experts. In 97% (170 of 175) of the cases, the orthodontic experts agreed with advice proposed by the inference system. We conclude that the current model is an effective means of deriving the opinion of an experienced clinician from a cephalometric tracing and provides an interesting insight into how orthodontists are influenced by the face when attempting to judge the sagittal relationship clinically. In addition, the current system would be an initial stage in the development of the decision-making system for the orthodontic diagnosis and treatment planning.

Adult↗
PubMed1990

Use of cephalometry in diagnosing resonance disorders.

A comparative cephalometric study of the oronasopharyngeal dimensions was carried out on 20 patients with normal speech, 20 patients with nasality and 22 patients with cleft palate speech, with the help of cephalometric landmarks given by Proffit and McGlove, Proffit et al., and Ricketts. The data obtained were subjected to statistical analysis, to determine whether there were any significant changes in oronasopharyngeal dimension between the various groups. It was concluded from the obtained data that there was an increase in the width and depth of the nasopharynx, with a consequential increase in the pharyngeal cavity volume in patients with cleft palate speech when compared with patients who had normal speech and those who had nasality.

Adolescent↗
PubMed1997

A method of magnification correction for posteroanterior radiographic cephalometry.

A simple method for magnification correction of width measurements from posteroanterior (PA) cephalograms is presented. Small lead markers were placed on selected landmarks of dry skulls. Lateral and PA cephalograms were obtained for each skull. Seven cephalometric width measurements were selected. Actual widths were deduced from the geometric principle of similar triangles. The magnification factor is the distance between the anode and the transporionic axis, plus or minus the corrected distance of the landmark to the transporionic axis measured from the lateral cephalogram, divided by the distances between the anode and the film. Differences between measurements made directly on the skull and corrected width measurements from the PA films were observed to be very small (< 0.50 mm) and statistically insignificant (P > 0.05). Paired measurements were of high correlation (r = +0.99). The present method of magnification correction means cephalometric width measurements can be made that are comparable in accuracy with measurements made directly on the skulls.

Adult↗
PubMed1997

Cephalometry needs innovation, not renovation.

Units of length, degree, and area are used when measuring cephalograms. In particular, the measurement of angles is a conventional method of quantifying shape. Because angles do not provide information about direction, there is no way to tell how and where one part of the facial structure has moved with respect to the rest. A new landmark data system using x- and y-coordinates is proposed, and some of its advantages over conventional methods are explained.

Cephalometry↗