A novel method for the management of proximal segment using computer assisted simulation surgery: correct condyle head positioning and better proximal segment placement

Are Virtually Designed 3D Printed Surgical Splints Accurate Enough for Maxillary Reposition as an Intermediate Orthognathic Surgical Guide

Background and Aim

The accuracy of the virtually-designed 3D-printed surgical splints requires investigation for the practical use of surgical plan in the operating room. This study aimed to compare the validity of the 3D-printed and the conventional intermediate splints and evaluate the outcomes after the surgical application of the 3D-printed splint compared with the predicted values.

Methods

In this study, ten patients with dentofacial deformity were recruited. Participants were analyzed by the conventional surgical planning and virtual surgical planning. The intermediate surgical splints were created by the conventional and 3D-printing methods. Maxillary movements in 3 spatial directions were measured in an articulator after the application of both splints. Correlation and agreement between the two methods were tested by intraclass correlation coefficient (ICC). After the confirmation of 3D printed splint validity for each patient, the surgery was performed using 3D printed splints. It is assumed that ideally cephalometric prediction values are going to be obtained using conventional acrylic splints (gold standard). So, as a second objective, the outcome of the surgically-applied 3D-printed splint was evaluated and compared with the predicted values and finally analyzed by the paired t-test.

Results

Based on the observations, there was an excellent agreement between the virtually-designed 3D-printed and conventional intermediate surgical splints (ICC ranged between 0.83 and 0.99 for linear values). There was a good cumulative agreement of ICC greater than 0.80. Overall, the mean linear measurements were not different between conventional and 3D-printed splint on the articulator. Also, there were no significant differences between the linear and angular measurements of 2D-cephalometric prediction and postoperation values.

Conclusion

The results showed cautiously the acceptable accuracy of the 3D-printed splints for several parameters in three spatial dimensions within the laboratory and clinical settings.

Computer Guided Generated Dual-Purpose Splint for Bilateral Sagittal Split Osteotomy

Purpose

to evaluate the efficacy of dual-purpose computer-generated splint in guiding the proximal and the distal segment in bilateral sagittal split osteotomy.

Patients and Method

It was a prospective case series study directed on 8 class III patients indicating the need of maxillary advancement and mandibular set back by bilateral sagittal split osteotomy. A CAD/CAM splint is generated to guide the distal segment to the stable maxilla and at the same time a grooved extension to engage the proximal segment ensuring the condyle in its planned position during fixation. The primary outcome was measured by calculating the difference between the pre- and post-operative condylar segment position.

Results

The present study included five female patient and three male patient with mean age of 28.4 ± 5.1 years. The accuracy of the splint in positioning the mandibular proximal segment showed promising results ranging from 2.59 to 0.49.

Conclusion

The dual-purpose splint introduced in this study showed satisfied results in maintaining the pre-operative condylar position while securing the distal segment in the desired plan.

Combining a digital design-mediated surgery-first approach and clear aligners to treat a skeletal Class III defect for aesthetic purposes: a case report

This case report introduces digital surgery-first approach orthognathic surgery assisted by three-dimensional virtual planning and combined with invisible orthodontic treatment for a 21-year-old female patient with a skeletal Class III high-angle gummy smile malocclusion. We explored the clinical significance of the widespread application of digital technology for rapid development of the orthodontic/orthognathic field. The regional acceleratory phenomenon and clear aligners were used to achieve fast and aesthetic tooth movement after surgery. The treatment lasted only 8 months, and the patient was satisfied with the aesthetic results. The results remained stable after 1 year of follow-up. This case report highlights the advantages of combining a digital design and a surgery-first approach to produce accurate, rapid, safe, stable, and fulfilling cosmetic results. The combination of the surgery-first approach and clear aligners can facilitate patient-oriented surgical orthodontic treatment.

Evaluation of postoperative changes in condylar positions after orthognathic surgery using balanced orthognathic surgery system

Background

Many studies on maintaining the condyle in a normal or anatomical position during orthognathic surgery have been conducted to stabilize surgical outcomes and prevent iatrogenic temporomandibular joint complications. The aim of this study is to evaluate the changes in condylar positions after orthognathic surgery using virtual surgical planning via the balanced orthognathic surgery (BOS) system.

Methods

Postoperative changes in condylar position were retrospectively evaluated in 22 condyles of 11 patients with skeletal class III malocclusion who underwent orthognathic surgery using virtual surgical planning via the BOS system. The center point coordinates of the condylar head before and after orthognathic surgery were analyzed using voxel-based registration.

Results

Changes in the condylar position mainly occurred downward in the y-axis (−1.09 ± 0.62 mm) (P < 0.05). The change in the x-axis (0.02 ± 0.68 mm) and z-axis (0.01 ± 0.48 mm) showed no significant difference between before and after orthognathic surgery.

Conclusion

These results indicate that the changes in the condylar positions after orthognathic surgery using virtual surgical planning via the BOS system mainly occurred downward in the y-axis, with slight changes in the x- and z-axes. The change in the condylar position after orthognathic surgery using the BOS system is clinically acceptable.

Three-Dimensional Changes in the Mandibular Proximal Segment After Using a Surgery-First Approach in Patients With Class III Malocclusion and Facial Asymmetry

ABSTRACT

This study was performed to evaluate condylar position and angulation after asymmetric mandibular setback between a conventional (CA) and surgery-first approach (SFA) using three-dimensional analysis. The condylar positions of 30 patients with skeletal Class III malocclusion and facial asymmetry who underwent 1-jaw (sagittal split ramus osteotomy) or 2-jaw orthognathic surgery (Le Fort I osteotomy and sagittal split ramus osteotomy) with CA (n = 18) or SFA (n = 12) from 2 university hospitals were studied. The three-dimensional assessment of condylar changes was performed using computed tomography images at the initial time point (T0) and at least 6 months after surgery (T1). Segmentation of condyles and cranial base assessment from cone-beam computed tomography images were performed using ITK-SNAP software (version 3.4.0). Condylar position and angulation changes were calculated using 3D Slicer software (version 4.10.2), and statistical analysis was performed. No significant translational or rotational condylar changes were observed between the deviated and nondeviated sides in each group or between the CA and SFA groups except yaw (P = 0.014). Linear mixed-model analysis and multivariate analysis showed no significant difference between the CA and SFA groups. Surgery-first approach might not be associated with more harmful effects on the condylar position and angulation changes as compared with CA.

Virtually-Planned Orthognathic Surgery Achieves an Accurate Condylar Position

PURPOSE

Accuracy in orthognathic surgery with virtual planning has been reported, but detailed analysis of accuracy according to anatomic location, including the mandibular condyle, is insufficient. The purpose of this study was to compare the virtual plan and surgical outcomes and analyze the degree and distribution of errors according to each anatomic location.

PATIENTS AND METHODS

This retrospective cohort study evaluated skeletal class III patients, treated with bimaxillary surgery. The primary predictor was anatomic locations that consisted of right and left condyles, maxilla, and the distal segment of the mandible. Other variables were age and gender. The primary outcome was surgical accuracy, defined as mean 3-dimensional distance error, mean absolute error, and mean error along the horizontal, vertical, and anteroposterior axes between the virtual plan and surgical outcomes. Landmarks were compared using a computational method based on affine transformation with a 1-time landmark setting. The mean errors were visualized with multidimensional scattergrams. Bivariate and regression statistics were computed.

RESULTS

This study included 52 patients, 26 men and 26 women, with a mean age of 21 years and 3 months. The mean 3D distance errors for condylar landmarks, maxillary landmarks, and landmarks on the distal segment of the mandible were 1.03, 1.25, and 2.24 mm, respectively. Condylar landmarks, maxillary landmarks, and the landmarks on the distal segment of the mandible were positioned at 0.49 mm inferior, 0.28 mm anterior, and 1.25 mm inferior, respectively. The landmark errors for the distal segment of the mandible exhibited a wider distribution than those for condylar and maxillary landmarks.

CONCLUSIONS

Agreement between the planned and actual outcome aided by virtual surgical planning was highest for the condyles, followed by the maxilla, and the distal segment of the mandible. It is important to consider the tendency for surgical errors in each anatomic location during operations.

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.

Current status of surgery-first approach (part III): the use of 3D technology and the implication in obstructive sleep apnea

Considering psychosocial needs of patients, it is not surprising that surgery-first approach (SFA) is becoming more popular than ever. Although the concept of SFA was introduced a few decades ago, the limitation of analysis method based on two-dimensional images makes surgeons reluctant to choose SFA. Recently, the advancement of three-dimensional technology allows us to perform SFA even without minimal pre-surgical orthodontic treatment, and the prediction of surgical outcome became more accurate, especially in obstructive sleep apnea (OSA) patients to whom the advantages of SFA should be more significant. Here, we describe the current trend of SFA and its implication in OSA patients.

Relevance of 3D virtual planning in predicting bony interferences between distal and proximal fragments after sagittal split osteotomy

After sagittal split osteotomy, the mandibular distal and proximal fragments do not always align themselves passively to one another, resulting in bony interferences and subsequent anomalous settlement of the condyles. Predicting these interferences could be an important ancillary procedure for avoiding intra- and postoperative surgical complications, rendering orthognathic surgery more effective and safer. This study evaluated the relevance of virtual surgical planning in assessing the displacement of the proximal segments after virtual distal segment repositioning, for predicting bony interferences between the segments and thus avoiding related intra- and postoperative surgical complications. The presence of interferences between the distal and proximal segments was compared between virtually predicted (computer-assisted simulation surgery, Dolphin software) and real cases in 100 consecutive patients diagnosed with dentofacial deformities who underwent orthognathic surgery with mandibular repositioning (using a short lingual osteotomy (SLO)). The results indicated that clockwise rotation of the mandible was the mandibular movement most prone to segment interference. Furthermore, virtual planning was sensitive (100%) but had low specificity (51.6%) in predicting proximal and distal segment interferences. This low specificity was due to the software-based automated design of the mandibular osteotomy, where the length of the distal segment was longer than the real SLO, and the mandibular ramus sagittal split was located just behind Spix's spine. Thus, more precise simulated osteotomies are needed to further validate the accuracy of virtual planning for this purpose.

Current status of the surgery-first approach (part I): concepts and orthodontic protocols

The "surgery-first" approach, defined as a team approach between surgeons and orthodontists for orthognathic surgery without preoperative orthodontic treatment, is aimed at dental decompensation. A brief historical background and indications for the surgery-first approach are reviewed. Considering the complicated mechanism of postoperative orthodontic treatment, the proper selection of patients is a vital component of successful surgery-first approach.

Three-Dimensional Virtual Treatment Planning: Presurgical Evaluation

OBJECTIVE

This article describes a virtual protocol designed to optimize surgical orthodontic diagnosis and treatment plan.

METHODS

A total of 15 patients undergoing orthodontic-surgical treatment have been analyzed with a presurgical virtual three-dimensional (3D) treatment planning, which involves 9 steps. All the patients have been treated with the use of occlusal splint guides projected on the basis of the surgical and orthodontic visualized treatment objective .

RESULTS

In all the analyzed patients, a precise and optimal orthodontic presurgical preparation has been obtained.

CONCLUSIONS

The 3D analysis seems more precise to interpret than two-dimensional; it provides information and images of craniofacial structures free from perspective distortion and it reduces the steps of the presurgical diagnosis. The simplicity of the protocol described in this paper makes possible to apply it in everyday practice.The study described here allows high-precision planning of orthodontic-surgical therapy and optimization of each treatment phase, with consequent advantages in clinical practice: a more accurate orthognathic surgery with predictable results.

Occlusion-Fit Three-Dimensional-Printed Zygoma Repositioner

Reduction malarplasty is utilized to reshape the facial form into an oval shape. However, complications and unfavorable results in reduction malarplasty have been reported. Reoperation of a nonunion malar complex is difficult relative to the achievement of a satisfactory outcome using the intraoral approach with a narrow surgical field because the normal anatomy has been destroyed, and previous surgery may have caused asymmetry. In this situation, computer-aided simulation surgery and surgical guides can serve as effective solutions to overcome the limitations of reoperative malarplasty using the intraoral approach.In this report, the authors present a case with successful treatment outcomes for a nonunion malar complex using a three-dimensional-printed zygoma repositioner.

A Review of Objective Measurement of Flap Volume in Reconstructive Surgery

Background

The utility and efficacy of 3-dimensional representation have been proven in bony reconstruction; however, its role in soft-tissue reconstruction remains limited. There is currently no reliable gold standard to objectively measure flap volume. This systematic review aims to summarize the available techniques used to objectively measure flap volume in reconstructive surgery.

Methods

A systematic literature search was performed to identify all relevant articles describing objective techniques to quantify flap volume. The search included published articles in 3 electronic databases-Ovid MEDLINE, EMBASE, and PubMed.

Results

A total of 16 studies were included. Flap volume was calculated using the following techniques: magnetic resonance imaging, computed tomography, 3-dimensional imaging and modeling, material templates, ultrasound, and weighing scales. Techniques and results of the included studies are summarized.

Conclusions

This systematic review provides a summary of various published techniques for objective pre- or intraoperative quantification of flap volume in reconstructive surgery. The preliminary results from this review are promising, and we believe that 3-dimensional representation and objective quantification is the future of reconstructive flap surgery. More studies are needed to study the clinical relevancy and impact of the various imaging modalities reviewed and to develop automated volumetric measurement technology with improved accuracy, efficacy, and reproducibility.

Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery

PURPOSE

Maxillary downgraft (MD) and mandibular setback (MS) are problematic procedures in terms of postoperative stability. While the amount of intraoperative clockwise rotation (CWR) of the proximal segment (PS) after MS combined with MD has a positive correlation with the amount of MD, mandibular relapse after MS with MD in relation to intraoperative CWR of the PS has not been reported. Moreover, the effect of mandibular relapse on maxillary stability after MS with MD remains unclear. The purpose of this study is to evaluate mandibular and maxillary stability after MS with MD in relation to intraoperative CWR of the PS and amount of MD.

MATERIALS AND METHODS

The study included 57 patients who underwent bimaxillary orthognathic surgery. Patients were classified into two groups according to whether MD was performed or not performed: Group I had 2 mm or more MD; and Group II had less than 2 mm MD including vertical impaction or no vertical changes. The amount of surgical movement and postoperative relapse were cephalometrically evaluated and statistically analyzed.

RESULTS

There was no significant difference in MS between Groups I and II, however, the vertical movement of the maxilla was different significantly (p < 0.001). In Group I, the intraoperative CWR and postoperative CCWR of the PS was greater than that of Group II (p = 0.010; p < 0.001, respectively). Consequently, the anterior relapse of the mandible was greater in Group I than in Group II despite the same amount of MS in Groups I and II. In Group I, with direct bone contact using Le Fort I inclined osteotomy, vertical relapse at point A showed no statistical correlation with anterior relapse at point B, while the vertical and horizontal dental relapse at U1 showed significant correlations with anterior relapse at point B (r = -0.403, p = 0.030; r = 0.581, p < 0.001, respectively).

CONCLUSION

For more stable results, Le Fort I inclined osteotomy is recommended to obtain direct bone contact when moving the maxilla inferiorly. The PS must also be fixed while maintaining vertical bone step to prevent CWR.

Corrective outcome and transverse stability after orthognathic surgery using a surgery-first approach in mandibular prognathism with and without facial asymmetry

OBJECTIVES

The aim of this study was to evaluate corrective outcome and transverse stability after orthognathic surgery via a surgery-first approach (SFA) in mandibular prognathism with and without facial asymmetry using 3-dimensional analysis.

STUDY DESIGN

Twenty-nine patients who received mandibular setback surgery using SFA were divided into 2 groups according to the menton deviation (4 mm): symmetry group (n = 17) and asymmetry group (n = 12). Using computed tomography images obtained before (T0), immediately after (T1), and 6 months after (T2) surgery, time-dependent changes in variables related to facial asymmetry, including maxillary height, ramal length, frontal and lateral ramal inclination, mandibular body length, and mandibular body height, were evaluated.

RESULTS

Immediately after surgery, the asymmetry group showed significantly decreased discrepancies between the longer and non-longer sides for all variables (P < .05); there were no significant differences in discrepancies between the 2 groups. During the postoperative period, no significant changes in discrepancies were found in any variable in either group. Compared with T0, the asymmetry group showed significantly decreased discrepancies in ramal length, frontal and lateral ramal inclination, and mandibular body length at T2.

CONCLUSIONS

Variables related to facial asymmetry showed significant improvement after surgical-orthodontic treatment using SFA, and corrected outcomes showed good postoperative stability in both the symmetry and asymmetry groups.

Recent advances in the reconstruction of cranio-maxillofacial defects using computer-aided design/computer-aided manufacturing

With the development of computer-aided design/computer-aided manufacturing (CAD/CAM) technology, it has been possible to reconstruct the cranio-maxillofacial defect with more accurate preoperative planning, precise patient-specific implants (PSIs), and shorter operation times. The manufacturing processes include subtractive manufacturing and additive manufacturing and should be selected in consideration of the material type, available technology, post-processing, accuracy, lead time, properties, and surface quality. Materials such as titanium, polyethylene, polyetheretherketone (PEEK), hydroxyapatite (HA), poly-DL-lactic acid (PDLLA), polylactide-co-glycolide acid (PLGA), and calcium phosphate are used. Design methods for the reconstruction of cranio-maxillofacial defects include the use of a pre-operative model printed with pre-operative data, printing a cutting guide or template after virtual surgery, a model after virtual surgery printed with reconstructed data using a mirror image, and manufacturing PSIs by directly obtaining PSI data after reconstruction using a mirror image. By selecting the appropriate design method, manufacturing process, and implant material according to the case, it is possible to obtain a more accurate surgical procedure, reduced operation time, the prevention of various complications that can occur using the traditional method, and predictive results compared to the traditional method.

The Application of 3D Printing Technology for Simultaneous Orthognathic Surgery and Mandibular Contour Osteoplasty in the Treatment of Craniofacial Deformities

BACKGROUND

Because of the limitation of specific preoperative design and surgical templates, orthognathic surgery and mandibular contour osteoplasty are generally performed in two stages. Three-dimensional printing technology has improved the accuracy of the surgery and results in good surgical predictability easily. This study aims to confirm the effectiveness, feasibility and precision of simultaneous mandibular contour osteoplasty and orthognathic surgery with the assistance of 3D printing technology.

METHODS

Ten patients, who were diagnosed with mandibular hypertrophy and bimaxillary deformities, were included in the study. In addition to conventional orthognathic surgery, mandibular angle ostectomy, mandibular outer cortex grinding or mandibular border ostectomy was designed for mandibular hypertrophy. Optimal osteotomy lines and simulated surgeries were designed according the 3D printing model of the mandible. Then, surgical templates were made on the 3D printing model. No muscle excision was performed in any patient. Preoperative, predicted and postoperative measurements were taken, including the gonial angle (Ar-Go-Me) and the mandibular width (Go-Go).

RESULTS

All the patients had a reposeful postoperative recovery, with no indication of obvious infection, facial paralysis, osteonecrosis or bone displacement. The gonial angle was improved from 110.3° ± 11.1 to 121.3° ± 2.9, and the mandibular width was improved from 117.5 mm ± 6.8 to 111.9 mm ± 4.2. The discrepancies between simulation and postoperation of the left gonial angle, the right gonial angle and the mandibular width were 0.56° ± 0.22, 0.65° ± 0.3 and 0.49 mm ± 0.43, respectively.

CONCLUSIONS

The results of our study illustrated the predictability, feasibility and reliability of simultaneous mandibular contour osteoplasty and orthognathic surgery with the assistance of 3D printing technology. Our technique could achieve functional improvement and an aesthetic profile at the same time.

LEVEL OF EVIDENCE IV

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