Computer-Aided Design and Manufacturing Cutting and Drilling Guides with Prebent Titanium Plates Improve Surgical Accuracy of Skeletal Class III Malocclusion

Automated Preoperative Planning Algorithm for Mandibular Angle Osteotomy Based on Anatomical Landmarks Detection: A Retrospective Study

OBJECTIVE

The aim of the study was to develop and evaluate an automated preoperative planning algorithm based on anatomical landmark point recognition for enhancing the efficiency and intelligence of preoperative planning for mandibular angle osteotomy.

METHODS

A retrospective cohort of 34 patients underwent preoperative planning with this algorithm. The present algorithm was developed using a method based on anatomical marker point recognition. The efficiency, symmetry, and safety of the automated preoperative planning and esthetics were statistically analyzed by paired t test and χ2 test.

RESULTS

The results showed that the automated planning algorithm was able to achieve a great improvement in preoperative planning efficiency as well as safety and symmetry. A prospective case report of 2 patients is then reported, illustrating the safety and esthetics of the algorithm with 1-year postoperative follow-up and postoperative esthetic scores.

CONCLUSION

This algorithm can help to improve the efficiency of preoperative planning for surgeons while ensuring safety and esthetics and can be further applied to other craniomaxillofacial personalized design surgeries in the preoperative design in the future.

Comparison of Patient-Specific Condylar Positioning Devices and Manual Methods in Orthognathic Surgery: A Prospective Randomized Trial

BACKGROUND

This study investigated whether patient-specific condylar positioning devices (CPDs) are beneficial compared to the conventional manual positioning of the condyles.

METHODS

In this prospective, randomized trial, patients undergoing orthognathic surgery with a bilateral sagittal split osteotomy of the mandible were included. The ascending ramus was positioned with computer-aided designed and computer-aided manufactured (CAD/CAM) patient-specific devices in the CPD group and manually in the control group. Postoperatively, cone-beam computed tomography (CBCT) was performed to align the virtually planned position with the postoperative result.

RESULTS

Thirty patients were enrolled in the study, with 14 randomized to the CPD group and 16 to the control group. In the CPD group, the ascending ramus differed in the postoperative CBCT scan from the virtually planned position by 0.8 mm in the left/right, 0.8 mm in the front/back, and 1.3 mm in the cranial/caudal direction. The corresponding control-group values were 1.1 mm, 1.3 mm, and 1.6 mm. CPD and controls differed significantly for the left/right movement of the rami (p = 0.04) but not for the other directions or rotations (p > 0.05).

CONCLUSIONS

The results demonstrate that both methods are accurate, and postoperative results matched the virtually planned position precisely. It can be assumed that the described CPDs are beneficial when a condylar position different from the preoperative is desired.

Comparison of Effects between Total Maxillary Setback Osteotomy and Anterior Maxillary Segmental Osteotomy on Nasolabial Morphology

BACKGROUND

The authors aimed to compare the effects of total maxillary setback osteotomy (TMSO) and anterior maxillary segmental osteotomy (AMSO) on nasolabial morphology.

METHODS

This retrospective clinical trial enrolled 130 patients undergoing maxillary surgery using TMSO or AMSO. Ten nasolabial-related parameters and nasal airway volume were measured preoperatively and postoperatively. The soft-tissue digital model was reconstructed using Geomagic Studio and Dolphin image 11.0. Statistical analysis was performed using IBM SPSS Version 27.0.

RESULTS

A total of 75 patients underwent TMSO, and 55 underwent AMSO. Both techniques achieved optimal repositioning of the maxilla. Except for the dorsal nasal length, the dorsal nasal height, the length of the nasal columella, and the upper lip thickness, the remaining parameters were significantly different in the TMSO group. In the AMSO group, only the nasolabial angle, the alar base width, and the greatest alar width showed significant differences. There was a significant difference in the nasal airway volume for the TMSO group. The results of matching maps are consistent with the statistical results.

CONCLUSIONS

TMSO has a more significant impact on both nose and upper lip soft tissues, whereas AMSO has a more significant impact on the upper lip and less on the nasal soft tissue. There is a significant decrease in nasal airway volume after TMSO, whereas AMSO showed less decrease. This retrospective study is helpful for clinicians and patients to understand the different changes in nasolabial morphology caused by the two interventions, which is essential for effective intervention and physician-patient communication.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

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.

A Novel Orthognathic Surgery With a Half-Millimeter Accuracy for the Maxillary Positioning Using Prebent Plates and Computer-Aided Design and Manufacturing Osteotomy Guide

This retrospective study aimed to assess the accuracy of prebent plates and computer-aided design and manufacturing osteotomy guide for orthognathic surgery. The prebent plates correspondent to the planning model were scanned with a 3-dimensional printed model for guide design and used for fixation. Forty-two patients who underwent bimaxillary orthognathic surgery using computer-aided design and manufacturing intermediate splint with the guide (guided group: 20 patients) or with conventional fixation under straight locking miniplates (SLMs) technique (SLM group: 20 patients) were analyzed. A deviation of the maxilla between the planned and postoperative positions was evaluated using computed tomography, which was taken 2 weeks before and 4 days after the surgery. The surgery time and the infraorbital nerve paranesthesia were also evaluated. The mean deviations in the mediolateral ( x ), anteroposterior ( y ), and vertical directions ( z ) were 0.25, 0.50, and 0.37 mm, respectively, in the guided group, while that in the SLM group were 0.57, 0.52, and 0.82 mm, respectively. There were significant differences in x and z coordinates ( P <0.001). No significant difference in the surgery duration and paranesthesia was seen, suggesting the present method offers a half-millimeter accuracy for the maxillary repositioning without increasing the risk of extending surgery duration and nerve complication.

Intraoperative condylar positioning techniques on mandible in orthognathic surgery

PURPOSE

The surgical condylar displacement often resulted in relapse and serious symptoms of temporomandibular joint disorders (TMD) after orthognathic surgery. To minimize the displacement, numerous techniques have been proposed. To verify their accuracy in positioning and effectiveness in preventing postoperative TMD and relapse, we reviewed the literature related to intraoperative condylar positioning techniques on the mandible in this study.

METHODS

The literature on condylar positioning techniques was reviewed with 2 charts, including the non-computer-assisted and the computer-assisted positioning methods. The pre- and postoperative alterations of condyles, the postoperative temporomandibular joint (TMJ) function, and surgical relapse were analyzed regarding the techniques. The clinical usage and characteristics were reviewed as well.

RESULTS

A total of 22 articles, including 907 patients, have been reported since 2001. Nearly all methods reach a considerable positioning accuracy within the range of 1-2 mm and 1-2° from the preoperative position. We ranked the accuracy of the methods from high to low: CAD/CAM CPDs>CAD/CAM titanium plate positioning>manual positioning>computer-assisted navigation systems>imaging positioning systems. Most skeletal class II and class III patients achieved great occlusion and had no TMJ dysfunction or relapse after condylar positioning.

CONCLUSION

Both the non-computer-assisted and computer-assisted condylar positioning techniques reach considerable accuracy in locating the preoperative condyle position and preventing TMJ dysfunction and surgical relapse. Different levels of surgeons and cases can benefit from multiple suggested positioning methods. Further research with large samples and long-term follow-up is worth looking forward to upgrading the current methods, improving the clinical utility, and developing new positioning techniques.

Use of modified 3D digital surgical guides in the treatment of complex mandibular fractures

The objective of this study was to evaluate the use of 3D modified digital surgical guide plates combined with preformed titanium plates in the treatment of complex mandibular fractures. Patients with complex mandibular fractures were randomized into three groups. Group A was treated with a combination of 3D modified digital surgical guide plates and preformed titanium plates, Group B was treated with preformed titanium plates only, and Group C was treated conventionally. The key design point of the guide plates is the "slot" structure, which is crucial for accurately locating the preformed titanium plate. Clinical outcomes, including facial symmetry, surgical accuracy, and maximum deviation were quantitatively assessed postoperatively. Twenty-two patients were recruited for this study, eight for Group A, six for Group B, and eight for Group C. Group A exhibited better postoperative clinical outcomes. Among three groups, significant improvements were found in Group A for facial symmetry (S1 [0.74 ± 0.17 mm, P < 0.001], S2 [0.86 ± 0.21 mm, P = 0.004], S3 [0.92 ± 0.26 mm, P < 0.001], S4 [0.32 ± 0.09 mm, P < 0.001], S5 [0.47 ± 0.16 mm, P = 0.042], S6 [0.35 ± 0.04 mm, P = 0.001], S10 [0.50 ± 0.31 mm, P = 0.048], S11 [0.97 ± 0.29 mm, P = 0.018]) and surgical accuracy (T1 [R, 0.56 ± 0.18 mm, P = 0.021], T1 [L, 0.60 ± 0.30 mm, P = 0.022], T2 [L, 0.76 ± 0.21 mm, P = 0.006], T4 [R, 0.37 ± 0.15 mm, P < 0.001], T4 [L, 0.40 ± 0.15 mm, P = 0.001], T8 [R, 0.40 ± 0.15 mm, P = 0.007], T8 [L, 0.31 ± 0.29 mm, P = 0.001], T9 [L, 0.51 ± 0.33 mm, P = 0.042], T10 [R, 0.58 ± 0.28 mm, P = 0.049], T10 [L, 0.53 ± 0.34 mm, P = 0.046], T11 [R, 0.54 ± 0.13 mm, P = 0.021], T12 [0.45 ± 0.16 mm, P = 0.003]). The ideal postoperative effect was found in Group A with maximum deviation analysis. 3D printed modified digital surgical guide plates can effectively improve treatment outcomes in complex mandibular fractures.

Three-dimensional facial esthetics-driven computer-assisted osteotomy and implant placement for immediate restoration of a failing dentition with a protruded maxilla

The rehabilitation of facial esthetics when transitioning from a failing dentition in a patient with maxillary protrusion is challenging. This clinical report described such a patient treated with an immediate cross-arch implant-supported fixed prosthesis. The ideal virtual upper lip position was used to predict the sagittal and vertical position of the restoration. A stackable device was fabricated to guide the osteotomy and implant placement.

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.