PSI-Guided Mandible-First Orthognathic Surgery: Maxillo-Mandibular Position Accuracy and Vertical Dimension Adjustability.

Giovanni Badiali,Mirko Bevini,Federico Bolognesi,Liliana Feraboli,Elisa Lovero,Federica Ruggiero,Claudio Marchetti,Alberto Bianchi,Ottavia Lunari

doi:10.3390/jpm11111237

Abstract

In orthognathic surgery, patient-specific osteosynthesis implants (PSIs) represent a novel approach for the reproduction of the virtual surgical planning on the patient. The aim of this study is to analyse the quality of maxillo-mandibular positioning using a hybrid mandible-first mandibular-PSI-guided procedure on twenty-two patients while the upper maxilla was fixed using manually bent stock titanium miniplates. The virtual surgical plan was used to design PSIs and positioning guides, which were then 3D printed using biocompatible materials. A Cone Beam Computed Tomography (CBCT) scan was performed one month after surgery and postoperative facial skeletal models were segmented for comparison against the surgical plan. A three-dimensional cephalometric analysis was carried out on both planned and obtained anatomies. A Spearman correlation matrix was computed on the calculated discrepancies in order to achieve a more comprehensive description of maxillo-mandibular displacement. Intraoperatively, all PSIs were successfully applied. The procedure was found to be accurate in planned maxillo-mandibular positioning reproduction, while maintaining a degree of flexibility to allow for aesthetics-based verticality correction in a pitch range between −5.31 and +1.79 mm. Such a correction did not significantly affect the achievement of planned frontal symmetry.

Highlights

The mandible-first approach for orthognathic surgery is an alternative procedure to the more widespread maxilla-first approach, which carries an array of theoretical advantages, such as reducing the mandibular condylar sag and reducing the strain on the upper maxillary miniplates while carrying out the mandibular Bilateral Sagittal Split Osteotomy (BSSO), subsequently improving the quality of planning reproduction [1]
While part of the theoretical advantages has not been demonstrated yet, the increased intraoperative flexibility offered by this approach in terms of vertical correction is counterbalanced by its reliance on the exactness of the post-osteosynthesis spatial relationship between proximal and distal mandibular segments
The debate between maxilla-first and mandible-first approach has been ongoing for decades and, the maxilla-first approach is more widely used, the mandiblefirst approach is preferable in a range of cases, for the fact that it provides a more stable frame of reference by using the upper maxilla as a guide

Summary

Introduction

The mandible-first approach for orthognathic surgery is an alternative procedure to the more widespread maxilla-first approach, which carries an array of theoretical advantages, such as reducing the mandibular condylar sag and reducing the strain on the upper maxillary miniplates while carrying out the mandibular Bilateral Sagittal Split Osteotomy (BSSO), subsequently improving the quality of planning reproduction [1].While part of the theoretical advantages has not been demonstrated yet, the increased intraoperative flexibility offered by this approach in terms of vertical correction is counterbalanced by its reliance on the exactness of the post-osteosynthesis spatial relationship between proximal and distal mandibular segments.In the pursuit of a technique which could reliably reproduce the digitally planned spatial relationship between the mandibular condyle-bearing segments and teeth-bearing segment, we combined the mandible-first approach with a PSI-guided mandibular procedure 4.0/).and demonstrated that it leads to a satisfactory reproduction of the planned mandibular anatomy [2].As current literature on mandibular and bimaxillary PSI-guided orthognathic surgery is still scarce, the potential failure of the procedure due to dental interferences caused by combined maxillary and mandibular inaccuracies—beyond the surgeon’s level of control—has been reported but has not been extensively investigated [3,4]. The mandible-first approach for orthognathic surgery is an alternative procedure to the more widespread maxilla-first approach, which carries an array of theoretical advantages, such as reducing the mandibular condylar sag and reducing the strain on the upper maxillary miniplates while carrying out the mandibular Bilateral Sagittal Split Osteotomy (BSSO), subsequently improving the quality of planning reproduction [1]. In the pursuit of a technique which could reliably reproduce the digitally planned spatial relationship between the mandibular condyle-bearing segments and teeth-bearing segment, we combined the mandible-first approach with a PSI-guided mandibular procedure 4.0/). As current literature on mandibular and bimaxillary PSI-guided orthognathic surgery is still scarce, the potential failure of the procedure due to dental interferences caused by combined maxillary and mandibular inaccuracies—beyond the surgeon’s level of control—. The approach we propose should theoretically limit such combined inaccuracies, transferring them from the occlusal surface, where they are most impactful, to the maxillary osteosynthesis surface, which can accept and dampen such minimal inaccuracies, rendering them mostly negligible.

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