|Year : 2018 | Volume
| Issue : 6 | Page : 101-104
Cephalometrics for you and me – Valid in today's scenario?
Vignesh Kailasam1, Ashima Valiathan2
1 Asst. Dean (Students) and Prof. of Orthodontics, Department of Orthodontics, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu, India
2 Adjunct Prof., Department of Orthodontics, Case Western Reserve University, Cleveland, Ohio, USA
|Date of Web Publication||7-Dec-2018|
Prof. Vignesh Kailasam
Department of Orthodontics, Sri Ramachandra Institute of Higher Education and Research, Chennai, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Cephalometrics is no panacea, alone or in conjunction with other records. An appraisal of cephalometrics and its limitations is probably the need of the hour. The deficiency of cephalometrics starts at the very beginning that is in the head positioning. Landmark definition is the biggest Achilles heel of cephalometrics. With the lack of clarity in landmark definition, identification and error in location having not been fully addressed, the actual problem arises since it these same landmarks which are used to construct planes and angles. The problem compounds with the description of some of the planes used for analysis being, at best, vague. In our view, however, the biggest disadvantage of cephalometrics is the limited acceptance of the racial variation in various measurements and how this has not been duly factored into the clinical diagnosis. The less said about the myriad of cephalometric analyses available and their contradictions. This begs the questions which of these analyses are more reliable. Thus, in conclusion, inspite of these limitations listed and noted for more than 50 years, cephalometrics, particularly lateral cephalometric radiography, though strictly not an essential diagnostic aid, continues to be popular and serves the clinical orthodontist with additional and what appears to be as essential and invaluable data.
Keywords: Cephalometrics, errors, validity
|How to cite this article:|
Kailasam V, Valiathan A. Cephalometrics for you and me – Valid in today's scenario?. J Indian Orthod Soc 2018;52, Suppl S2:101-4
|How to cite this URL:|
Kailasam V, Valiathan A. Cephalometrics for you and me – Valid in today's scenario?. J Indian Orthod Soc [serial online] 2018 [cited 2019 Apr 25];52, Suppl S2:101-4. Available from: http://www.jios.in/text.asp?2018/52/6/101/247055
Cephalometrics is no panacea, alone or in conjunction with other records. There are certain aspects of cephalometric analysis in orthodontics that must be understood fully, if objectivity is the goal. Although Graber way back in 1956 warned of definite limitations of cephalometrics, many in the fraternity still swear by it and its utility in orthodontic therapy is unchallenged., So an appraisal of cephalometrics and its limitations is probably the need of the hour. The errors in cephalometric measurements have been classified by Macri and Athanasiou as projection errors, errors within the measuring system, and errors in landmark identification while the general disadvantages of lateral cephalometry have been well summarized by Naragond et al. in that it gives a two-dimensional view of a three-dimensional object, reliability is questionable, has an assumption of symmetry, fallacy of false precision, and fallacy of ignoring the patient. Superimposition and temporomandibular joint visualization are other areas of weaknesses of the conventional cephalograms.
The deficiency of cephalometrics starts at the very beginning that is in the head positioning of the patient for taking the cephalograms. Head position has not been fully resolved, and natural head position is subjective at best and any variation would alter measurements Malkoc et al has reported that linear measurements and the measurement of angles between horizontal planes are likely to be affected by head rotation in lateral cephalograms. However, the positioning of the patient is one of the many critical problems encountered.
Landmark definition is the biggest Achilles heel of cephalometrics. The very definition of the landmark has been criticized leading to location errors and reproducibility. Orbitale, for example, is defined as “the lowest point of the orbital rim.” Martin criticized this definition stating that it does not serve as a landmark, is not well defined, is unreliable since it is entirely an esthetic judgment. The literature is replete with such “inappropriateness” in landmark definition. Each landmark has its own characteristic distribution of error. The direction in which the location error happens is critical to the dimension of the error. Even when the same head film is assessed, errors in landmark identification occur and they are too great to be ignored. The reliability of measurements on cephalograms has been extensively investigated,,,,, and the result of those studies revealed different conclusions, which highlights that caution should be taken when measurements are transferred to reality. Richardson et al. have shown that the discrepancies in measuring an apparently simple entity, such as the width of a tooth, may be surprisingly large. Hence, the accuracy of measuring a parameter such as mandibular length and deducing clinical inferences such as the efficiency of functional appliances which are assessed in the range of millimeters from these measurements are fraught with danger.
With the lack of clarity in landmark definition, identification and error in location having not been fully addressed, the actual problem arises since it these same landmarks which are used to construct planes and angles. The problem compounds with the description of some of the planes used for analysis being, at best, vague. An example is the occlusal plane, which although has been recognized as an excellent reference plane, is really not a plane but a curve and has inherent disadvantages. Hence, it is but natural that the inferences derived from occlusal plane as a reference are, therefore, definitely questionable. Another example is the mandibular plane which, unfortunately, is rather variable and subjective. The alternative method of drawing the plane through the anthropometric landmarks gonion and gnathion is no better because of the variability in establishing both landmarks. Further, gnathion is a midline point while gonion is not leading to natural mathematical errors.
Analyses of angular measurements require complete objectivity since the planes used to measure them are not reliable. The inevitable conclusion is that two variables hardly permit positive deductions. A most common example would be the angle formed between the long axis of the mandibular incisor and the mandibular plane. A further complication is that the apex of the lower central incisor is perhaps the most difficult landmark to accurately locate. The upper incisor suffers a similar disadvantage with the landmark closely related to it, which is Point A, is very hard to see and locate.
Another severe criticism of cephalometrics was provided by Moyers. “Fabrication, camouflage, confusion, and subtraction” are Moyers' terms for 4 of the systematic ways in which the conventional cephalometrics would misinform. Mathematical expressions of facial and dental relations through cephalometrics have tended to oversimplify some of the problems. Graber clearly proved that magnification is 5%–8% per cent in the peripheral portions and the basic intuition driving the cephalostat is mathematically unfounded and geometrically unsound. Every orthodontic postgraduate would have read the landmark cephalometric articles by Cecil Steiner on lateral cephalometric radiography. It still remains unresolved whether to treat a patient as a Class II or Class I and thus formulate a treatment plan when the maxilla is orthognathic as depicted by SNA of 84 (upper end of normal), and mandible is also orthognathic as depicted by an SNB is 78 (lower end of normal) since the angle ANB will naturally indicate Class II. Further, literature evidence is lacking for the Steiner compromise mechanics. Even today, space analysis for incisor retraction has not been standardized. Add this to the fact that measurements of the axial inclination of incisor teeth, so useful to the clinician, are also among the least reliable.
The most surprising conclusion which questioned the very need of cephalometrics for treatment planning was provided by Devereux et al., who proved that for most treatment-planning decisions in a sample of six patients, the availability of a lateral cephalometric radiograph and its tracing did not make a significant difference to the treatment decisions.
In our view, however, the biggest disadvantage of cephalometrics is the limited acceptance of the racial variation in various measurements and how this has not been duly factored into the clinical diagnosis. To be fair, the Indian Orthodontic Society had previously published a booklet on the racial variations as seen in various cephalometric analyses. A superficial perusal of the publications of these variations suggests a huge variation among parameters. Cephalometric norms have been established, and differences with Caucasian norms have been observed in various populations from Assam to Chennai (Madras) and even NRIs. Not only geographical variation but norms have been evaluated for caste groups in a single geographical area and differences have been noted.
A particularly significant disadvantage of cephalometric radiographs is the information regarding the midline and nonmidline areas. Any nonmidline structure is superimposed on the contra lateral side. Thus, the lateral cephalogram is inherently handicapped in assessing the natural left and right variations of the human skull. A clinical example would be the gonial angle, wherein lateral head films have the inherent disadvantage in that they do not permit reliable registrations.
A limited disadvantage of cephalometrics that is their availability has been overcome at least in Indian metros and towns. Further, this technique is not useful for demonstrating bone quality, width of the cortical bone and only demonstrates a cross-sectional image of the alveolus where the central rays of the X-ray device are tangent to the alveolus.
The less said about the myriad of cephalometric analyses available and their contradictions. This begs the question as which of these analyses are more reliable. Miethke suggested that we select certain analysis because our instructors advised us to do so and this was not a scientific approach to problem-solving. His experience was that individual variation was so large that cephalometric measurements could not help with treatment planning. If a patient has a skull configuration with a low-position sella, angle SNA would be reduced even if the maxilla is correctly positioned. It would be insane to correct the sella, and no patient is worried about the sella but definitely worried about the maxillary esthetics.
When Creekmore et al. being strong proponents of customization of bracket prescription, since a single preadjusted prescription will not achieve the treatment objectives, it is but natural to apply the same logic. Treating patients according to fixed numbers as provided in cephalometric analysis may not be similarly desirable. As the teacher of Miethke states “you cannot go by numbers.”
There is no “theory of cephalometrics.” Unsurprisingly, the most cited article on cephalometrics of the last 50 years is “The inappropriateness of conventional cephalometrics” published in 1979. Thus, it is critically important that we as clinical orthodontists, remember Graber's observation that the patient is still the most important source of information. The newer investigation that is CBCTs with the 3D imaging, we are moving from lengths and angles toward volume and surface areas and thus may have the advantages of overcoming some of the limitations of cephalometrics but its role as an investigative aid has to be extensively assessed. Thus, in conclusion, inspite of these limitations, listed and noted for more than 50 years, cephalometrics, particularly lateral cephalometric radiography, though strictly not an essential diagnostic aid, continues to be popular and serves the clinical orthodontist with additional and what appears to be as essential and invaluable data.
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Conflicts of interest
There are no conflicts of interest.
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