Computer-assisted osteotomy guides and pre-bent titanium plates improve the planning for correction of facial asymmetry

A novel guide for minimally invasive genioplasty

Mentoplasty or genioplasty is a simple procedure to enhance facial aesthetics. While usually considered simple, it might present certain difficulties during execution, especially when a minimally invasive approach is preferred. Drilling and cutting guides are a valuable tool to overcome such challenges but usually require larger incision and dissection to allow adequate positioning and bone rigid fixation. In this article, we describe a novel guide design that permits adequate bone repositioning while preserving minimally invasive protocols.

Accuracy and influencing factors of maxillary and mandibular repositioning using pre-bent locking plates: a prospective study

In-house repositioning methods based on three-dimensional (3D)-printing technology and the use of pre-bent plates has been gaining popularity in orthognathic surgery. However, there remains room for further improvement in methods and investigations on clinical factors that affect accuracy. This single-centre, prospective study included 34 patients and aimed to evaluate the accuracy and factors influencing maxillary and mandibular repositioning using pre-bent locking plates. The plates were manually pre-bent on the 3D-printed models of the planned position, and their hole positions were scanned and reproduced intraoperatively with osteotomy guides. The accuracy of repositioning and plate-hole positioning was calculated in three axes with the set landmarks. The following clinical factors that affect repositioning accuracy were also verified: deviation of the plate-hole positioning, amount of planned movement, and amount of simulated bony interference. The median deviations of the repositioning and hole positioning between the preoperative plan and postoperative results were 0.26 mm and 0.23 mm, respectively, in the maxilla, and 0.69 mm and 0.36 mm, respectively, in the mandible, suggesting that the method was highly accurate, and the repositioning concept based on the plate hole and form matching was more effective in the maxilla. Results of the correlation test suggest that large amounts of bony interference and plate-hole positioning errors in the up/down direction could reduce mandibular repositioning accuracy.

Orthognathic surgical planning using graph CNN with dual embedding module: External validations with multi-hospital datasets

BACKGROUND AND OBJECTIVE

Despite recent development of AI, prediction of the surgical movement in the maxilla and mandible by OGS might be more difficult than that of tooth movement by orthodontic treatment. To evaluate the prediction accuracy of the surgical movement using pairs of pre-(T0) and post-surgical (T1) lateral cephalograms (lat-ceph) of orthognathic surgery (OGS) patients and dual embedding module-graph convolution neural network (DEM-GCNN) model.

METHODS

599 pairs from 3 institutions were used as training, internal validation, and internal test sets and 201 pairs from other 6 institutions were used as external test set. DEM-GCNN model (IEM, learning the lat-ceph images; LTEM, learning the landmarks) was developed to predict the amount and direction of surgical movement of ANS and PNS in the maxilla and B-point and Md1crown in the mandible. The distance between T1 landmark coordinates actually moved by OGS (ground truth) and predicted by DEM-GCNN model and pre-existed CNN-based Model-C (learning the lat-ceph images) was compared.

RESULTS

In both internal and external tests, DEM-GCNN did not exhibit significant difference from ground truth in all landmarks (ANS, PNS, B-point, Md1crown, all P > 0.05). When the accumulated successful detection rate for each landmark was compared, DEM-GCNN showed higher values than Model-C in both the internal and external tests. In violin plots exhibiting the error distribution of the prediction results, both internal and external tests showed that DEM-GCNN had significant performance improvement in PNS, ANS, B-point, Md1crown than Model-C. DEM-GCNN showed significantly lower prediction error values than Model-C (one-jaw surgery, B-point, Md1crown, all P < 0.005; two-jaw surgery, PNS, ANS, all P < 0.05; B point, Md1crown, all P < 0.005).

CONCLUSION

We developed a robust OGS planning model with maximized generalizability despite diverse qualities of lat-cephs from 9 institutions.

Standard orthodontic treatment after condylectomy for patients with active unilateral condylar hyperplasia

INTRODUCTION

Unilateral condylar hyperplasia (UCH) is a progressive, nonneoplastic overgrowth of the condyle of the temporomandibular joint. For treating active UCH, a popular method combines orthognathic surgery with high condylectomy and orthodontic treatment. The goal of this study was to introduce a new method to correct asymmetry for active UCH.

METHODS

Retrospectively, 47 patients with active UCH were divided into horizontal-type, vertical-type, and combined-type. All patients were treated with condylectomy plus postsurgery standard orthodontics (CPSO) with applied miniscrews implanted in infrazygomatic crest and hard palate to intrude affected side of maxillary molars and apply intermaxillary traction for contralateral molars. Cone-beam computed tomography was taken at presurgery, postsurgery, and the end of orthodontics (T3).

RESULTS

In the vertical (n = 10) and combined (n = 28) types, deviation of the chin and the canting of the mandible and maxillary occlusal plane were significantly reduced at T3. A difference in the torque of bilateral maxillary first molar (U6) and bilateral mandibular first molar (L6) was significantly reduced at T3. The anterior, superior, and posterior joint spaces in the vertical-type and combined-type were significantly decreased at T3 compared with postsurgery. In contrast, in the horizontal-type group (n = 9), the deviation of the chin was corrected; however, the canting of the mandible and maxillary occlusal plane was significantly increased at T3 compared with presurgery.

CONCLUSIONS

CPSO restored facial and occlusal symmetry for vertical-type and combined-type active UCH and returned affected-side condyle to the glenoid fossa. However, CPSO was not suitable for treating the horizontal-type UCH.

Three-dimensional condylar displacement and remodelling following correction of asymmetric mandibular prognathism with maxillary canting

The aim of this study was to investigate the three-dimensional condylar displacement and long-term remodelling following the correction of asymmetric mandibular prognathism with maxillary canting. Thirty consecutive patients (60 condyles) with asymmetric mandibular prognathism >4 mm and occlusal canting >3 mm, treated by Le Fort I osteotomy and bilateral sagittal split ramus osteotomy, were included. Spiral computed tomography scans obtained at different periods during long-term follow-up (mean 17 ± 7.2 months) were gathered and processed using ITK-SNAP and 3D Slicer. The condyles were subjected to translational and rotational displacements immediately after the surgery (T2), which had not fully returned to the original preoperative positions at the last follow-up (T3). Condylar remodelling was observed at the last follow-up (T3), with the shorter side condyles subjected to higher surface resorption and overall condylar volume loss. The overall condylar volume on the shorter side was significantly reduced compared to the volume on the elongated side (-11.9 ± 90.6 vs -131.7 ± 138.2 mm³; P = 0.001). About 73%, 87%, 53%, and 54% of the shorter side condyles experienced resorption on the posterior, superior, medial, and lateral surfaces, respectively; in contrast, only 50% of the elongated side condyles showed resorption on the superior surface. Higher preoperative asymmetry was significantly correlated with increased postoperative condylar displacement (P < 0.05). The vertical asymmetry and the vector of condylar displacement were associated with the resultant remodelling process. It is concluded that condylar resorption of the shorter side condyle, which may affect the long-term surgical stability, has to be considered.

Effect of computer-assisted design and manufacturing cutting and drilling guides accompanied with pre-bent titanium plates on the correction of skeletal class II malocclusion: a randomized controlled trial

This study was performed to assess the effect of correcting skeletal class II malocclusion based on the application of computer-assisted design and manufacturing (CAD/CAM) cutting and drilling guides accompanied with pre-bent titanium plates. Fifty patients with skeletal class II malocclusion were recruited into this prospective randomized controlled clinical trial and assigned to two groups. Patients underwent bilateral sagittal split ramus osteotomy directed by CAD/CAM cutting and drilling guides accompanied with pre-bent titanium plates (group A) or CAD/CAM splints (group B). Postoperative assessments were performed. Differences between the virtually simulated and postoperative models were measured. Patients in both groups had a satisfactory occlusion and appearance. More accurate repositioning of the proximal segment was found in group A than in group B when comparing linear and angular differences to reference planes; however, no significant difference was revealed for the distal segment. In conclusion, CAD/CAM cutting and drilling guides with pre-bent titanium plates can provide considerable surgical accuracy for the positional control of the proximal segments in bilateral sagittal split ramus osteotomy for the correction of skeletal class II deformities.

Deformation Assessment of the Manually Pre-bent Titanium Miniplates in Orthognathic Surgery With Finite Element Analysis

This study summarized the literature regarding the application of pre-bent titanium miniplates in orthognathic surgery and evaluated the extra deformation of the manually pre-bent titanium miniplates via finite element analysis for acquiring higher surgical accuracy. The literature was reviewed with a chart. Three models of titanium miniplates with different thicknesses (1.0 mm, 0.8 mm, 0.6 mm) were created using COMSOL Multiphysics software for biomechanical behavior analysis. The 3 models were virtually bent into 5 angles (15 degree, 30 degree, 45 degree, 60 degree, 80 degree). respectively to simulate the preoperative virtual bending, then to simulate the practical manual bending via finite element analysis. The stresses and displacements of these models were recorded. The models from virtual bending simulation and manual bending simulation were registered to analyze the deviations. The results showed that the maximum stress and the displacement deviations between the virtual bending models and the manual bending models increased with the thickness and bending angle of the pre-bent miniplate models. To improve the surgical accuracy, measures should be applied to the manually pre-bent titanium miniplates to reduce the extra deformation when the plate being thicker and the bending angle being larger.

Combined orthodontic and surgical treatment supported by virtual planning in a severe mandibular asymmetry: A case report

This article describes the complex dental treatment of a 17-year-old girl with skeletal Class I, severe mandibular asymmetry, maxillary retrusion, normodivergent pattern, left canine and molar Class II, canting of the occlusal plane, lateral left cross-bite, deep bite, upper and lower incisors retrusion and an increased curve of Spee. To achieve optimal results, a multidisciplinary approach to treatment was adopted involving orthodontics and maxillofacial surgery. The surgical phase was supported by virtual surgical planning with dedicated software. Thanks to the development of the three-dimensional radiological findings, a visualization and an accurate simulation of all the surgery-steps help to determine reproducibly and with high precision the best adjustments to do. Firstly, the excessive curve of Spee, the incisors retrusion and the deep bite were corrected with orthodontic treatment. The surgical treatment plan consisted of a palatal expansion, maxillary advancement, zygomatic grafts, bilateral sagittal osteotomy for mandibular correction and genioplasty. Orthodontic treatment was continued to finish with all the objectives achieved. After two years, the patient was satisfied with her facial and dental treatment results and with her oral function as well.