The validity of computerized orthognathic predictions

Abstract

Objective: utilizing OPAL™ cephalometric prediction software.

Design: A retrospective investigation involving the random selection of Class II orthognathic patients from surgical records.

Subjects: These 25 cases had undergone treatment aimed at producing Class I incisors. This involved fixed orthodontic appliances and a mandibular advancement osteotomy with rigid internal fixation.

Methods: Lateral cephalographs from three key stages were digitized and processed using the OPAL software. Pre-treatment predictions were generated and compared with the actual clinical changes.

Results: Prediction of some of the principal OPAL variables (SNA, ANB, LAFH%, OJ, OB) was reasonably accurate in terms of mean values. However, there were large individual variations for most measurements, and prediction of Wits, MxP/MnP, LAFH, and LPFH was prone to systematic error. In particular, there was a tendency towards over-prediction of the surgically-induced backward mandibular rotation.

Conclusion: In lieu of further validation caution should be exercised with the interpretation of individual OPAL predictions, especially vertical skeletal changes, and an explanation given to patients that orthognathic predictions are based on generalizations.

Keywords:

• Class II
• computerized prediction
• OPAL
• orthognathic surgery

Acknowledgments

The authors wish to thank their surgical and orthodontic colleagues who were involved in the care of these patients: Miss Pat Jenkins, and Messrs Peter Cove, Julian Crabb and David Roberts. We are also grateful to Jane Baxter, from the York Clinical Effectiveness Unit, for her help with the data processing.