At present, stock linear distractors are used for internal maxillary distraction osteogenesis. However, the authors’ research group has demonstrated, through an in silico analysis, that linear ...distraction leads to bone deformities and malocclusion, whereas helical distraction can yield ideal outcomes. A system for designing and manufacturing custom helical distractors has recently been developed, and the feasibility of these appliances now needs to be assessed. This study was, therefore, conducted to gain an initial insight into their feasibility. The study had two goals. First, it aimed to demonstrate, in an in vitro model, that the novel system of custom helical distraction can produce appropriate clinical outcomes. The second aim was to compare the performance of custom helical distractors with that of stock devices and hybrid devices (i.e., linear appliances that feature patient-specific footplates). Interpreting the results as trends, this study showed that the system of custom helical distraction resulted in in vitro outcomes that were superior to those obtained with stock and hybrid devices.
Orthognathic surgery primarily corrects skeletal anomalies and malocclusion to enhance facial aesthetics, aiming for an improved facial appearance. However, this traditional skeletal-driven approach ...may result in undesirable residual asymmetry. To address this issue, a soft tissue-driven planning methodology has been proposed. This technique estimates bone movements based on the envisioned optimal facial appearance, thereby enhancing surgical accuracy and effectiveness. This study investigates the initial implementation phase of the soft tissue-driven approach, simulating the patient’s ideal appearance by realigning distorted facial landmarks to an ideal state. The algorithm employs symmetrization and weighted optimization strategies, aligning projected optimal landmarks with standard cephalometric values for both facial symmetry and form, which are essential in orthognathic surgery for facial aesthetics. It also incorporates regularization to preserve the patient's facial characteristics. Validation through retrospective analysis of preoperative patients and normal subjects demonstrates this method's efficacy in achieving facial symmetry, particularly in the lower face, and promoting a natural, harmonious contour. Adhering to soft tissue-driven principles, this novel approach shows promise in surpassing traditional methods, potentially leading to enhanced facial outcomes and patient satisfaction in orthognathic surgery.
The primary objective of this cadaver study was to assess the feasibility of a novel custom helical distraction system and a patient-specific antral maxillary distractor. The study involved two fresh ...cadaver heads and followed a systematic procedure. First, virtual planning was conducted for an asymmetric maxillomandibular advancement. Custom patient-specific hardware was then fabricated to enable sequential mandibular advancement and gradual maxillary distraction. The mandibular lengthening procedures were found to be highly accurate, with only minor deviations from the planned results. In terms of maxillary distraction, the patient-specific antral distractors demonstrated favorable outcomes, with two noteworthy exceptions. Ideal forward maxillary advancement was short by a modest 2–3 mm in both cadavers. Additionally, cadaver 2 exhibited an unplanned pitch malrotation. However, an excellent occlusion was achieved in cadaver 1 and an acceptable anterior occlusion in cadaver 2, albeit with bilateral posterior open bites that could be readily corrected with interdental elastics in a clinical setting. This cadaver model study provides compelling evidence for the feasibility of patient-specific antral helical distractors, highlighting their potential to yield positive outcomes. Importantly, the study results suggest that patient-specific antral distractors may offer superior results compared to the current standard of linear distractors.
This in silico kinematic study was performed to evaluate the best attainable outcomes of maxillary distraction osteogenesis given the constraints of linear and helical motion. The study sample ...included the retrospective records of 30 patients with maxillary retrusion who had been treated with distraction or had been recommended this treatment. The primary outcomes were the errors of linear and helical distraction. The study measured two types of error: misalignment of key upper jaw landmarks and misalignment of the occlusion. Concerning the misalignment of key landmarks, the median misalignments resulting from helical distraction were minimal; the interquartile ranges were also minimal. The median misalignments and interquartile ranges that resulted from linear distraction were significantly larger. Regarding the occlusal misalignments, helical distraction produced minor occlusal misalignments, while linear distraction produced significantly larger errors. The results of this study confirmed that helical motion is the ideal motion for LeFort I distraction.
Abstract Three-dimensional (3D) cephalometry is not as simple as just adding a ‘third’ dimension to a traditional two-dimensional cephalometric analysis. There are more complex issues in 3D analysis. ...These include how reference frames are created, how size, position, orientation and shape are measured, and how symmetry is assessed. The main purpose of this article is to present the geometric principles of 3D cephalometry. In addition, the Gateno–Xia cephalometric analysis is presented; this is the first 3D cephalometric analysis to observe these principles.
Helical mandibular distraction is theoretically better than linear or circular distraction. However, it is not known whether this more complex treatment will result in unquestionably better outcomes. ...Therefore, the best attainable outcomes of mandibular distraction osteogenesis were evaluated in silico, given the constraints of linear, circular, and helical motion. This cross-sectional kinematic study included 30 patients with mandibular hypoplasia who had been treated with distraction, or to whom this treatment had been recommended. Demographic information and the computed tomography (CT) scans showing the baseline deformity were collected. The CT scans of each patient were segmented and three-dimensional models of the face created. Then, the ideal distraction outcomes were simulated. Next, the most favorable helical, circular, and linear distraction movements were calculated. Finally, errors were measured: misalignment of key mandibular landmarks, misalignment of the occlusion, and changes in intercondylar distance. Helical distraction produced trivial errors. In contrast, circular and linear distractions resulted in errors that were statistically and clinically significant. Helical distraction also preserved the planned intercondylar distance, while circular and linear distractions led to unwanted changes in the intercondylar distance. It is now evident that helical distraction offers a new strategy to improve the outcomes of mandibular distraction osteogenesis.
Abstract The success of craniomaxillofacial (CMF) surgery depends not only on the surgical techniques, but also on an accurate surgical plan. The adoption of computer-aided surgical simulation (CASS) ...has created a paradigm shift in surgical planning. However, planning an orthognathic operation using CASS differs fundamentally from planning using traditional methods. With this in mind, the Surgical Planning Laboratory of Houston Methodist Research Institute has developed a CASS protocol designed specifically for orthognathic surgery. The purpose of this article is to present an algorithm using virtual tools for planning a double-jaw orthognathic operation. This paper will serve as an operation manual for surgeons wanting to incorporate CASS into their clinical practice.
The purpose of this ambispective study was to investigate whether deep learning-based automatic segmentation and landmark detection, the SkullEngine, could be used for orthognathic surgical planning. ...Sixty-one sets of cone beam computed tomography (CBCT) images were automatically inferred for midface, mandible, upper and lower teeth, and 68 landmarks. The experimental group included automatic segmentation and landmarks, while the control group included manual ones that were previously used to plan orthognathic surgery. The qualitative analysis of segmentation showed that all of the automatic results could be used for computer-aided surgical simulation. Among these, 98.4% of midface, 70.5% of mandible, 98.4% of upper teeth, and 93.4% of lower teeth could be directly used without manual revision. The Dice similarity coefficient was 96% and the average symmetric surface distance was 0.1 mm for all four structures. With SkullEngine, it took 4 minutes to complete the automatic segmentation and an additional 10 minutes for a manual touchup. The results also showed the overall mean difference between the two groups was 2.3 mm for the midface and 2.4 mm for the mandible. In summary, the authors believe that automatic segmentation using SkullEngine is ready for daily practice. However, the accuracy of automatic landmark digitization needs to be improved.
Digital dental articulation for three-piece maxillary orthognathic surgery is challenging. The purpose of this proof-of-concept study was to evaluate the clinical feasibility of a newly developed ...mathematical algorithm to digitally establish the final occlusion for three-piece maxillary surgery. Five patients with jaw deformities who had undergone a three-piece double-jaw surgery that was planned virtually were randomly selected for this study. The final occlusion had been hand-articulated using stone casts, scanned into the computer and used in the surgery. These hand-articulated occlusions served as the control group. To form the experimental group, the three-piece maxillary dental arch was articulated again automatically from the patient’s original occlusion using the mathematical algorithm. The hand- and algorithm-articulated occlusions were then evaluated qualitatively by two experienced orthodontists. A quantitative evaluation was also performed. The results of the qualitative evaluation showed that all of the three-piece occlusions, hand- and algorithm-articulated, were clinically acceptable based on the American Board of Orthodontics grading system. When compared, two of the algorithm-articulated occlusions were clearly better (40%), one was the same (20%), and two were slightly worse (40%) than the hand-articulated occlusions. All of the quantitative measurements were comparable between the two articulation methods. In conclusion, the results of this study demonstrate that it is clinically feasible to digitally articulate the three-piece maxillary arch to the intact mandibular dental arch.
Abstract To assess facial form, one has to determine the size, position, orientation, shape, and symmetry of the different facial units. Many of these assessments require a frame of reference. The ...customary coordinate system used for these assessments is the ‘standard anatomical frame of reference’, a three-dimensional Cartesian system made by three planes: the sagittal, the axial, and the coronal. Constructing the sagittal plane seems simple, but because of universal facial asymmetry, it is complicated. Depending on the method one selects, one can build hundreds of different planes, never knowing which one is correct. This conundrum can be solved by estimating the sagittal plane a patient would have had if his or her face had developed symmetrically. We call this the ‘primal sagittal plane’. To estimate this plane we have developed a mathematical algorithm called LAGER (Landmark Geometric Routine). In this paper, we explain the concept of the primal sagittal plane and present the structure of the LAGER algorithm.
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