An evaluation of the Pi analysis in the assessment of anteroposterior jaw relationship

New Sagittal and Vertical Cephalometric Analysis Methods: A Systematic Review

Cephalometric analysis is an essential tool used in orthodontic diagnosis and treatment planning. The main objectives of correct cephalometric analysis include resolving anteroposterior and vertical maxillary and mandibular base discrepancies. For a diagnostic tool to be of value, it should be precise, reliable and reproducible. Unfortunately, according to some studies, the accuracy of input and, therefore, the diagnostic reliability of some of the points and measurements may not be satisfactory. To this end, new cephalometric measurements are being developed with increased precision. In order to properly and definitively determine the usefulness of a given measurement in cephalometric diagnosis, it is necessary to carry out a critical evaluation of available studies. The aim of this systematic review was to evaluate the available scientific literature describing new landmarks and reference linear and angular measurements of 2D cephalometric analyses assessing the sagittal and vertical discrepancy in the position of jaw bases since the last systematic review in 2013. The secondary aim was to assess the accuracy and reliability of new anthropometric landmarks and reference planes in relation to those used previously, and their instability in relation to growth and orthodontic tooth movements. To carry out the intended plan, electronic databases such as PubMed, Scholar Google, Web of Science and Pro Quest were searched using specific keywords. Initially, a total of 1451 articles were retrieved. Then, duplicate articles in all databases were excluded from the resulting publications. The results showed that despite such a high number of articles published in peer-reviewed scientific journals, only 12 studies on new cephalometric analyses in the sagittal plane and 4 studies on new cephalometric analyses in the horizontal plane met the criteria and, as a result, were included in the review.

A heuristic model for cephalometric diagnosis of sagittal dysplasia

OBJECTIVE

To identify the best-suited cephalometric parameter for assessing the sagittal skeletal discrepancy in the Indian population.

DESIGN

An in vitro, observational, single-blinded, retrospective study.

SETTING

Department of Orthodontics and Dentofacial Orthopaedics.

METHODS

A total of 94 lateral cephalograms were used in this study. The study involved one key person and two examiners. The key person collected the radiographs, coded, analysed and classified them into three groups (skeletal classes I, II and III). Subsequently, the coded radiographs were independently analysed by the two examiners. They classified the cases by matching a minimum of 6 out of 11 parameters. On completion of diagnosis by the examiners, the samples were decoded and matched with the original diagnosis given by the key person. The samples in which identification of a particular cephalometric parameter matched the original evaluation as given by the key person was regarded as correctly diagnosed. The number of correctly assessed cases was used to judge the diagnostic performance of all the parameters in all the cases. Cross-validation of the method was performed, and a diagnostic algorithm was developed for diagnosis.

RESULTS

β angle and Pi angle showed a positive predictive value of 1 in both skeletal class I and II cases. ANB angle, W angle and HBN angle showed a positive predictive value of 1 in skeletal class III cases.

CONCLUSION

No single cephalometric parameter can independently be used to diagnose sagittal skeletal discrepancy in all cases. However, a conclusive diagnosis on the type of sagittal skeletal malocclusion can be made by using a simple and easy to use diagnostic algorithmic process having a combination of cephalometric parameters.

Cephalometric Floating Norms for the β Angle and MMBP-Wits

The importance of an accurate measurement of sagittal jaw relationship, that is, skeletal class, is critical to orthodontic treatment planning. The ANB angle, β angle, and MMBP-Wits are among indices of sagittal jaw relationship. All of these indices are subjected to geometrical distortion, especially from facial divergence, making the use of floating (individualized) norms necessary. This study thus provides floating norms for the ANB angle and for the first time for the β angle and MMBP-Wits. Lateral head films were obtained from 119 subjects (74 females and 45 males; mean age, 11.2 ± 1.5 years; range, 8.2–14.0 years) with well-balanced and pleasant profile and a near-ideal occlusion. Multiple regression models were employed to quantify the association of the ANB angle, β angle, and MMBP-Wits each with other four angular cephalometric parameters including SNA, SN/PP, SN/MP, and NSBa angles. The β angle and MMBP-Wits were associated with the SNA and SN/MP angles; the ANB angle was associated with all the four other cephalometric variables. Floating norms for the β angle and MMBP-Wits (but not ANB angle) have been cross-tabulated according to the SNA angle (from 74° to 90°) and SN/MP angle (from 24° to 44°). While the ANB angle is subjected to significantly more geometrical distortion as compared to the β angle and MMBP-Wits, floating norms may be used to individualize the reference values for both the β angle and MMBP-Wits.

A “new vista” in the assessment of antero-posterior jaw relationship

Aim

The purpose of this investigation was to (1) compare the credibility of four recently introduced cephalometric measurements in assessing the antero-posterior jaw relationship; (2) To assess the correlation between various measurements used for assessment of antero-posterior discrepancy, including Yen linear, Yen angle, W angle and Pi angle.

Materials and Methods

The sample size for the study consisted of 45 subjects with age group of 15-19 years (mean age 17 ± 2.1) and was subdivided into Skeletal Class I, II and III groups of 15 each based upon the ANB angle derived from the pre treatment lateral cephalogram. Landmarks were located and Yen angle, Yen linear, W angle and Pi angle were assessed for each group. All the lateral cephalograms were traced by a single examiner. Intra examiner reliability was assessed by Intraclass co-efficient correlation (ICC) test. Correlation coefficients were obtained for each of parameters to compare their relationship with other parameters in Class I group. Receiver operating characteristics (ROC) curves were run to examine sensitivity and specificity of all the angles.

Results

The results showed that ICC for all the groups were ≥0.90 showing good repeatability of the measurements. There was statistically significant correlation between Yen angle and ANB angle, Yen linear and Yen angle for Class I group, between W angle and Yen angle for Class II group, between Yen angle, Yen linear and ANB for Class III group. ROC curves showed that Pi angle had 100% sensitivity and specificity to discriminate a Class II and a Class III group from a Class I and a Class III group from a Class II. Yen linear and W angle showed very low specificity to differentiate a Class II from a Class I group.

Interpretation and Conclusion

The new parameters considered in the study were found to be equally reliable and are not affected much by local remodeling due to tooth movements or by occlusal or Frankfurt horizontal plane. These parameters measure the antero-posterior discrepancy more consistently and accurately, with Pi angle being the most accurate.

A reflection on radiographic cephalometry: the evaluation of sagittal discrepancy

A critical review is presented of the basic properties and applications of cephalometry as a clinical tool with a focus on the evaluation of sagittal discrepancy. Diagnostic cephalometric assessments are subjective and not based on evidence. To assess individual skeletal and/or facial soft tissue form subjectively, selected norms are used. Norms have been developed for various ethnical groups to improve clinical applicability, but subjectivity remains. That subjectivity precludes application of a modern review system, making the present review a personal account. The cephalometric evaluation of sagittal discrepancy finds its historic origin in the Angle classification. Recent publications try to improve accuracy in classifying sagittal discrepancy. It remains unclear in what sense such efforts influence treatment decisions and/or treatment effect. Almost all selected landmarks are located on or dependent upon periosteal/endosteal bone image contours. Their homology is based on circumstantial reasoning and stability over time, which is implicitly assumed. However, implant growth studies and histological investigations show most landmarks to be unstable, as they are involved in displacement and bone remodelling. These landmarks are therefore heterologous when used for individual evaluation of change over time. Notwithstanding the above-indicated limitations, diagnostic cephalometric assessments are clinically useful and help to develop perceptions of balance and harmony and communication between colleagues and patients. There is no evidence-based method to prefer one particular diagnostic method. Landmark location accuracy and geometric issues do not play a decisive role. The subjective characteristic of diagnostic evaluations limits their power to size/shape comparisons. Structural superimposition is the valid biologically evidence-based method to provide advanced insight in individual growth and/or treatment changes and their variations.

[New developments in cephalometrics]

Recently l recalled the error in the principle which makes cephalometric analysis unsuitable for orthodontic diagnosis. Now, three methods of analysis have been published precisely conceived in order to avoid this error. Will cephalometric analysis succeed in its search for the truth?