Treatment outcome in orthognathic surgery—A prospective randomized blinded case-controlled comparison of planning accuracy in computer-assisted two- and three-dimensional planning techniques (part II)

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Abstract

Purpose

The aim of the present study was to compare the accuracy of two-dimensional (2D) and three-dimensional (3D) prediction methods. The hypothesis was that a 3D technique would give a more accurate outcome of the postoperative result.

Material and methods

Patients with severe class III occlusion were included and planed with both a 2D and 3D prediction technique. They were there after randomly subdivided into a control (2D) and test (3D) group and treated according to the technique randomized for. Cephalometric measurements from 2D and 3D predictions were compared with 12-month follow-up respectively. Together with an analysis of tracing error, placements of 3580 cephalometric markers, 2460 measurements, 680 intra-individual analyses and 1200 preop/postop comparisons were performed in 57 individuals.

Results

Statistically significant differences for accuracy between the two groups were seen for 11/NSL-112/NSL2 and for A-A2 (p < 0.05). Both groups showed a high level of accuracy for SNA and SNB. The test group also showed a relatively high level of accuracy for 11/NSL and for the A-point. No prediction method achieves a perfect accuracy. As expected from this, measuring accuracy within each group showed statistically significant difference for all markers and cephalometric measurements (p < 0.001). Mandibular markers showed greater differences than maxillary markers.

Conclusion

The present study indicates an equal high accuracy in predicting facial outcome for both studied techniques. However, in patients with asymmetry the three-dimensional technique has an obvious advantage.

Introduction

Treatment of dentofacial deformities and severe malocclusions with orthognathic surgery involves thorough preoperative planning. The planning is based upon clinical recordings, X-ray examinations, photographs and dental casts (Moorrees, 1995, Wahl, 2006). It is important, when performing corrections of the malocclusion, to simultaneously optimize the facial appearance in accordance with the neutral head posture (Downs, 1948, Moorrees, 1994).

Two-dimensional (2D) computer programs for cephalometric measurements and treatment prediction are widely used (Ricketts, 1969). Through the development of three-dimensional (3D) examination techniques and computerized analysis methods (Westermark et al., 2005), the opportunity to make 3D computerized predictions of orthognathic treatments has arisen (Gateno et al., 2000, Gateno et al., 2003). Preoperative planning aims for an optimal combination of masticatory function and facial appearance. It is therefore crucial that the preoperative planning is able to predict the final treatment outcome and not only high accuracy promptly after surgery. Numerous articles have been published on virtual surgical planning, but with an insufficient number of subjects to yield significant outcomes (Stokbro et al., 2014).

The accuracy of surgical treatment of severe malocclusions depend on three main sequences: preoperative planning, transfer of planning to surgery (Surgical template); and surgical precision/relapse. Previous studies on 3D planning have not focused on only one of these, but have reported accuracy as a consequence of multiple sequences (Marchetti et al., 2006, Xia et al., 2007, Mazzoni et al., 2010, Tucker et al., 2010, Zinser et al., 2012, Hsu et al., 2013). In the present study, when comparing accuracy between the two methods, the accuracy is measured as a result of one sequence only, namely, the preoperative planning. The other sequences are equally distributed in both the test and the control groups. Accordingly, we are more precise in describing the importance of preoperative planning, and the outcome of this study is therefore important.

Recently, we published a comparative study of a two-dimensional and a three-dimensional computerized planning technique (Bengtsson et al., 2017). Thirty patients, who underwent planning with both techniques, were treated according to the two-dimensional planning. Precision measurements of marker placement were also conducted. Based on that study, the present study expands the number of subjects to 60. All patients, after undergoing planning with both planning techniques, were randomly divided into a test or control group.

The main aim of this study was to compare the accuracy of two prediction methods, namely, 2D and 3D. A secondary objective was to measure the accuracy for each method in preoperative treatment planning compared with 12-month follow-up.

Section snippets

Study subjects

Patients aged between 18 and 30 years, diagnosed with Angle class III occlusion with a minimum of 5-mm negative horizontal overjet and referred to The Department of Oral and Maxillofacial Surgery, The University Hospital of Skåne, Lund, Sweden were included in the study. Patients with systemic musculoskeletal diseases, drug abuse and poor psychiatric status were excluded, as well as patients with temporomandibular joint disorders. In all, 60 patients were recruited and agreed to participate.

Subjects

After finalizing follow-ups, the trial included 57 subjects, aged between 18 and 28 years at surgery (mean 20.8 years), who were randomized into test (3D) and control (2D) groups. The test group included 13 male and 15 female patients with a mean age of 21.1 years. The control group included 17 male and 12 female patients with a mean age of 20.5 years.

Three of the 60 subjects were considered dropouts, due to noncooperation in the follow-ups. They represented both genders and both groups.

Cephalometric measurement of accuracy

A

Patient selection

Only class III malocclusions, with or without a presence of asymmetry, were included in the present study. The reasons for this were the possibility of the patient's own physical simulation in an Angle class II malocclusion and the aim to homogenise the cohort.

Several studies on accuracy of planning techniques have been conducted on selected surgical movements (Marchetti et al., 2006, Tucker et al., 2010, Hsu et al., 2013, Stokbro et al., 2016). When studying treatment planning, the inclusion

Conclusions

The present study showed a statistically significant difference between 3D and 2D prediction methods regarding the anterior maxilla, with an advantage for 3D. Additionally, both studied methods indicated a high accuracy in predicting facial outcome except for mandible markers.

Funding

This project was supported by personal grants to Martin Bengtsson from the Scandinavian Association of Oral and Maxillofacial Surgeons (25000 SEK), from the Southern Region within the Swedish Dental Association (50000 SEK) and from the Swedish Association of Oral and Maxillofacial Surgeons (25000 SEK). The sponsors had no influence upon the study design, analysis of the data or upon the writing of the manuscript.

Acknowledgements

The authors want to thank Dr Mikael Korduner, Head of the Oral and Maxillofacial Department, University Hospital of Skåne, Lund, Sweden and Statistician Helena Johansson, PhD, Institute for Health and Ageing, Melbourne, Australia for contributing to the performance of the present trial.

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