Predictability of maxillary positioning: a 3D comparison of virtual and conventional orthognathic surgery planning

A facebow-free technique for mechanical articulator remounting using computed tomography

This technical note introduces a technique for remounting dental casts to a mechanical articulator using computed tomography (CT) without a facebow. We have developed a jig method that ensures precise remounting by aligning the virtual dental casts to the upper and lower jaw models reconstructed from the CT and transferring them to a virtual articulator based on anatomical landmarks. A custom-designed positioning jig and splint further enhance the accuracy of the process, preserving the spatial relationship between the midface and mandible. The proposed mounting jig technique can help transfer the patient's maxillomandibular relationship quickly, repeatedly, and accurately to an articulator after the patient leaves.

Management of facial asymmetry assisted with digitally designed surgical guide for 3-dimensional maxillary repositioning: A case report

Orthodontists play a pivotal role in diagnosing, planning, and preparing patients for orthognathic surgeries. Digital technologies like cephalometry, intraoral scans, CBCT scans, CAD-CAM-assisted 3-D planning, and printed surgical splints, have largely replaced conventional techniques. The automated software produces surgical splints with a design similar to conventional which may not address complex scenarios, involving symmetric and asymmetric maxillary impaction. To address this, a surgical splint designed using 3D dolphin software was modified with 3-matic software for precise guidance. This article gives insight into the digitally designed surgical splint for the correction of facial asymmetry on skeletal Class III bases and occlusal canting in an 18-year-old woman. The precise relocation of the maxilla was achieved as planned pre-surgically leading to significant improvement in the facial aesthetics. In conclusion, modified splint design fabrication offers more predictable outcomes, reduces laborious laboratory procedures, and acts as a reliable guide for precise surgical results.

Virtual surgical plan with custom surgical guide for orthognathic surgery: systematic review and meta-analysis

BACKGROUND

The shift from traditional two-dimensional (2D) planning to three-dimensional (3D) virtual surgical planning (VSP) has revolutionized orthognathic surgery, offering new levels of precision and control. VSP, combined with computer-aided design/computer-aided manufacturing (CAD/CAM) technology, enables the creation of patient-specific surgical guides and implants that translate preoperative plans into more precise surgical outcomes. This review examines the comparative accuracy and operative efficiency of VSP, especially when used with custom surgical guides, against conventional 2D planning in orthognathic surgery.

MAIN TEXT

The study systematically reviewed and analyzed published literature comparing the accuracy and operative time between VSP and conventional planning methods. The meta-analysis included clinical trials, controlled trials, and observational studies on patients undergoing orthognathic surgery, focusing on the degree of alignment between planned and postoperative bone positions and total surgery time. Results indicate that VSP consistently reduces discrepancies between planned and actual surgical outcomes, particularly when integrated with custom surgical guides. Additionally, while VSP demonstrated potential time-saving advantages over conventional planning, these differences were not statistically significant across studies, likely due to high variability among study protocols and designs.

CONCLUSIONS

VSP with custom surgical guides enhances surgical accuracy in orthognathic procedures, marking a significant advancement over traditional methods. However, the reduction in operative time was not conclusively significant, underscoring the need for further studies to evaluate time efficiency. These findings emphasize VSP's role in improving surgical precision, which holds substantial implications for future orthognathic surgical practices.

An automatic tracking method to measure the mandibula movement during real time MRI

Mandibular movement is complex and individual due to variations in the temporomandibular joint (TMJ). Consequently, patient-centered dentistry should incorporate patients' specific anatomy and condylar function in treatment planning. Real-time magnetic resonance imaging (rt-MRI) visualizes relevant structures and tracks mandibular movement. However, current assessments rely on qualitative observations or time-consuming manual tracking, lacking reliability. This study developed an automatic tracking algorithm for mandibular movement in rt-MRI using least mean square registration (LMS) and compared it to manual tracking (MT) during mouth opening. Ten participants with skeletal class I underwent rt-MRI (10 frames/s). The same operator tracked the condylar pathway for the two methods, setting 2000 landmarks (2 landmarks x100 frames x10 participants) for MT and 210 landmarks (3 landmarks x7 frames x10 participants) for LMS. Time required, superimposition error, and the distance between tracked condylar pathways were compared between methods. LMS tracking was 76% faster and showed significantly better superimposition (0.0289 ± 0.0058) than MT (0.059 ± 0.0145) (p = 0.002). During one-third of the movement, the pathways tracked by both methods were more than 1 mm and 1° apart. These findings highlight the benefits of automatic condylar movement tracking in rt-MRI, laying the groundwork for more objective and quantitative observation of TMJ function.

Accuracy of maxillary repositioning surgery in teaching hospitals using conventional model surgery

PURPOSE

The aim of this study was to assess the accuracy of maxillary repositioning surgery in teaching hospitals using conventional model surgery.

MATERIALS AND METHODS

A total of 73 patients undergoing single-piece LeFort I osteotomies in the maxilla and bilateral sagittal split osteotomies in the mandible were included in the study. Preoperative and immediate postoperative cone-beam CT were compared in computer software (Dolphin3D©). Maxillary landmarks relative to the vertical and horizontal reference lines were evaluated. The difference between the planned and achieved maxillary positions was measured. Distance error in millimeters and achievement ratio (achieved displacement/planned displacement*100) were calculated for different maxillary movements.

RESULTS

Midline correction and advancement were the most accurate movements with an overall mean distance error of 0.53 mm and 0.63 mm respectively while posterior impaction and setback were the least accurate movements with 1.38 mm and 1.76 mm mean discrepancies, respectively. A significant difference was observed only in setback movement regarding the discrepancy value (P < .05). Although setback and down-graft movements tended to under-correction, all other movements were overcorrected. As the magnitude of maxillary movements increases, the accuracy decreases. In severe displacements (≥ 8 mm), the accuracy declines significantly (P < .05).

CONCLUSION

Classic cast surgery and manually fabricated intermediate splints in teaching hospitals yield accurate and acceptable results in the majority of cases (84.6%). The accuracy of maxillary repositioning decreases as the magnitude of displacement increases.

OrthoCalc: The six degrees of freedom measurement workflow of rotational and displacement changes for maxilla positioning evaluation

BACKGROUND

This study is undertaken to establish the accuracy and reliability of OrthoCalc, a 3D application designed for the evaluation of maxillary positioning.

METHODS

We registered target virtual planned models, maxillary models from pre-operative and post-operative CT scans, and post-operative intra-oral scans to a common reference system, allowing for digital evaluation. To assess rotational changes, we introduced a novel measurement method based on virtual cuboid models. Displacement errors were calculated based on proposed registration matrices. We also compared OrthoCalc to established commercial medical software as a benchmark.

RESULTS

Statistical significance calculated showed no significant differences between OrthoCalc and commercial software. the biggest error of 0.04 degree in rotation change was found in the yaw. A maximum displacement change of 0.75 mm was found in the X direction.

CONCLUSIONS

Our study validates OrthoCalc as a precise and reliable tool for assessing maxillary position changes with six degrees of freedom in orthognathic surgery, endorsing its clinical utility.

[Comparison of the virtual surgical planning position of maxilla and condyle with the postoperative real position in patients with mandibular protrusion]

OBJECTIVE

To compare the difference between virtual surgical planning (VSP) position and postoperative real position of maxilla and condyle, and to explore the degree of intraoperative realization of VSP after orthognathic surgery.

METHODS

In this study, 36 patients with mandibular protrusion deformity from January 2022 to December 2022 were included. All the patients had been done bilateral sagittal split ramus osteotomy (SSRO) combined with Le Fort Ⅰ osteotomy under guidance of VSP. The VSP data (T0) and 1-week postoperative CT (T1) were collected, the 3D model of postoperative CT was established and segmented into upper and lower jaws in CCMF Plan software. At the same time, accor-ding to the morphology of palatal folds, the virtual design was registered with the postoperative model, and the unclear maxillary dentition in the postoperative model was replaced. Then the postoperative model was matched with VSP model by registration of upper skull anatomy that was not affected by the operation. The three-dimensional reference plane and coordinate system were established. Selecting anatomical landmarks and their connections of condyle and maxilla for the measurement, we compared the coordinate changes of marker points in three directions, and the angle changes between the line connecting the marker points and the reference plane to analyze the positional deviation and the angle deviation of the postoperative condyle and maxilla compared to VSP.

RESULTS

The postoperative real position of the maxilla deviates from the VSP by nearly 1 mm in the horizontal and vertical directions, and the anteroposterior deviation was about 1.5 mm. In addition, most patients had a certain degree of counterclockwise rotation of the maxilla after surgery. Most of the bilateral condyle moved forward, outward and downward (the average distance deviation was 0.15 mm, 1.54 mm, 2.19 mm, respectively), and rotated forward, outward and upward (the average degree deviation was 4.32°, 1.02°, 0.86°, respectively) compared with the VSP.

CONCLUSION

VSP can be mostly achieved by assistance of 3D printed occlusal plates, but there are certain deviations in the postoperative real position of maxilla and condyle compared with VSP, which may be related to the rotation axis of the mandible in the VSP. It is necessary to use patient personalized condylar rotation axis for VSP, and apply condylar positioning device to further improve surgical accuracy.

The impact of orthodontic-surgical treatment on facial expressions-a four-dimensional clinical trial

OBJECTIVE

The objective of this clinical trial was to compare facial expressions (magnitude, shape change, time, and symmetry) before (T0) and after (T1) orthognathic surgery by implementing a novel method of four-dimensional (4D) motion capture analysis, known as videostereophotogrammetry, in orthodontics.

METHODS

This prospective, single-centre, single-arm trial included a total of 26 adult patients (mean age 28.4 years; skeletal class II: n = 13, skeletal class III: n = 13) with indication for orthodontic-surgical treatment. Two reproducible facial expressions (maximum smile, lip purse) were captured at T0 and T1 by videostereophotogrammetry as 4D face scan. The magnitude, shape change, symmetry, and time of the facial movements were analysed. The motion changes were analysed in dependence of skeletal class and surgical movements.

RESULTS

4D motion capture analysis was feasible in all cases. The magnitude of the expression maximum smile increased from 15.24 to 17.27 mm (p = 0.002), while that of the expression lip purse decreased from 9.34 to 8.31 mm (p = 0.01). Shape change, symmetry, and time of the facial movements did not differ significantly pre- and postsurgical. The changes in facial movements following orthodontic-surgical treatment were observed independently of skeletal class and surgical movements.

CONCLUSIONS

Orthodontic-surgical treatment not only affects static soft tissue but also soft tissue dynamics while smiling or lip pursing.

CLINICAL RELEVANCE

To achieve comprehensive orthodontic treatment plans, the integration of facial dynamics via videostereophotogrammetry provides a promising approach in diagnostics.

TRIAL REGISTRATION NUMBER

DRKS00017206.

Managing Predicted Post-Orthognathic Surgical Defects Using Combined Digital Software: A Case Report

For facial abnormalities, recent developments in virtual surgical planning (VSP) and the virtual design of surgical splints are accessible. Software companies have worked closely with surgical teams for accurate outcomes, but they are only as reliable as the data provided to them. The current case's aim was to show a fully digitized workflow using a combination of three digital software to correct predicted post-upward sliding genioplasty defects. To reach our goal, we presented a 28-year-old man with long-face syndrome for orthodontic treatment. Before orthognathic surgery, a clinical and paraclinical examination was performed. For a virtual surgical plan, we used the dedicated surgical planning software NemoFab (Nemotec, Madrid, Spain) and Autodesk MeshMixer (Autodesk Inc., San Rafael, CA, USA). To create the design of the digital guides, DentalCAD 3.0 Galway (exocad GmbH, Darmstadt, Germany) and Autodesk MeshMixer (Autodesk Inc., San Rafael, CA, USA) were used. The patient had undergone bilateral sagittal split osteotomy in addition to Le Fort 1 osteotomy and genioplasty, followed by mandible base recontouring ostectomy. Stable fixation was used for each osteotomy. Based on our case, the current orthognathic surgery planning software was not able to perform all the necessary operations autonomously; therefore, future updates are eagerly awaited.