Intraoral Curved Ostectomy for Prominent Mandibular Angle by Grinding, Contiguous Drilling, and Chiseling:

Evaluating robotic assistance on the learning curve and efficiency of mandibular angle ostectomy: an animal model study

Introduction

This study evaluated the efficacy and learning curve of a maxillofacial surgical robotic system (MSRS) guided by electromagnetic navigation for mandibular angle ostectomy (MAO), compared to traditional surgical methods.

Methods

The study utilized a controlled experiment involving thirty rabbits, paired divided into experimental and control groups. The experimental group underwent MAO using the MSRS, while the control group was treated with conventional surgical techniques. The surgeons performing the procedures were inexperienced in robotic surgery and MAO to assess the learning curve and the impact of robotic assistance. Key parameters measured included the accuracy of ostectomy, setup time, and ostectomy efficiency, with data analyzed through a paired-t test to compare the performance between the two groups.

Results

The study indicated a significant reduction in ostectomy time for the experimental group, with improved accuracy and efficiency in ostectomy. The study found that robotic assistance could decrease the risk of complications and enhance surgical outcomes. It also highlighted the presence of an initial learning curve when adopting new robotic technologies, which could be mitigated through adequate training and simulation practices.

Discussion

Using MSRS for MAO could lead to faster early learning curves and increased ostectomy efficiency compared to traditional surgical methods. It demonstrated the potential benefits of integrating robotic systems into craniofacial surgery, suggesting a promising direction for future surgical practices.

Total inferior border ostectomy versus T-shape genioplasty for chin narrowing combined with mandibular contouring

The objective of this study was to compare the indications and outcomes of the total inferior border ostectomy and T-shape genioplasty. A retrospective study was conducted using the clinical notes and records of patients who underwent total inferior border ostectomy (group 1, n = 42) and T-shape genioplasty (group 2, n = 60). The outcomes were evaluated by assessment of computed tomography images combined with medical records and photographs. Lower facial height, chin width, chin symmetry, and facial proportions, as well as patient satisfaction and complications were investigated. The data were collected preoperatively and 6-24 months postoperatively. All 102 patients showed an improved lower facial contour. No severe complications were observed during the follow-up period. Although the postoperative lower to midfacial height ratios were similar in the two groups (P = 0.080), both the preoperative and postoperative chin width to lower facial height ratios were lower in group 1 (both P < 0.001). A larger amount of chin narrowing, as well as better chin symmetry were observed in group 1 (P < 0.001). In conclusion, compared to the T-shape genioplasty, the total inferior border ostectomy is well suited for a longer, wider, and more asymmetrical chin. The surgical options should be considered and chosen quantitatively to achieve aesthetically pleasing results.

The Accuracy of a Patient-Specific Three-Dimensional Digital Ostectomy Template for Mandibular Angle Ostectomy

BACKGROUND

Although three-dimensional (3D)-printed digital ostectomy templates (DOTs) can help surgeons perform mandibular angle ostectomy (MAO) more precisely and safely, the clinical application of such templates is problematic.

OBJECTIVES

The aim of this study was to evaluate the accuracy of a novel DOT and improve the precision of MAO.

METHODS

A total of 20 patients with a prominent mandibular angle (PMA) were allocated into 2 groups (10 patients per group). A conventional DOT and a novel DOT were applied to guide MAO in Groups A and B, respectively. The mean time taken for curved osteotomy and the volume of postoperative drainage on 1 side within 24 hours were recorded. The deviations between the simulated and postoperative lower border of the mandible were measured on both sides.

RESULTS

All the patients were satisfied with the cosmetic outcomes. Statistical results showed that the mean time taken for curved osteotomy was shorter in Group B than in Group A, and that the volume of postoperative drainage on 1 side within 24 hours was similar between the 2 groups. The deviations at the anterior and posterior parts of the inferior border showed that the accuracy of osteotomy was higher in Group B than in Group A, and that there was no significant difference between the 2 groups in the middle part.

CONCLUSIONS

The novel DOT is easy to locate and fix tightly, which reduced the operating time and increased the safety and precision of the procedures.

LEVEL OF EVIDENCE: 4

Reduction Mandibuloplasty Along with Partial Masseter Muscle Resection: Masseter Muscle Response and Bone Regeneration

OBJECTIVE

To compare the masseter muscle changes and bone regeneration between reduction mandibuloplasty along with partial masseter muscle resection and reduction mandibuloplasty alone.

METHODS

Forty-seven patients who complained of prominent mandibular angle and hypertrophy masseter muscles (MMH) were divided into group 1 treated with reduction mandibuloplasty along with partial masseter muscle resection, and group 2 treated with reduction mandibuloplasty alone. Pre-5 days and long-term postoperative computed tomography data were collected, and the masseter muscle volume, hemi-mandible volume, and unilateral lower face width were measured. Patient satisfaction and complication were also evaluated.

RESULTS

At long-term follow-up, group 1 showed a greater decrease in masseter volume (p < 0.001), and lower face width (p < 0.001), and less bone regeneration (p < 0.001) than group 2. Furthermore, patients in group 1 had higher satisfaction with the surgical outcome (p < 0.05).

CONCLUSION

Reduction mandibuloplasty along with partial masseter muscle resection can achieve a slender frontal appearance and significantly decrease bone generation. For patients with MMH, reduction mandibuloplasty along with partial masseter muscle resection is an effective and predictable lower face reshaping surgery.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine Ratings, please refer to Table of Contents or online Instructions to Authors www.springer.com/00266 .

A Novel Precise Optical Navigation System for Craniomaxillofacial Surgery Registered With an Occlusal Splint

BACKGROUND

An augmented reality tool allows visual tracking of real anatomical structures and superimposing virtual images, so it can be used for navigation of important structures during surgery.

OBJECTIVES

The authors have developed a new occlusal splint-based optical navigation system for craniomaxillofacial surgery. In this study, the authors aim to measure the accuracy of the system and further analyze the main factors influencing precision.

METHODS

Ten beagle dogs were selected and a three-dimensional model was established through computed tomography scanning, dental model making, and laser scanning, and then registration was performed according to the tooth marking points. The bilateral mandibular osteotomy was performed on Beagle dogs under navigation system based on the occlusal splint. The left side was taken to compare the deviation between the preoperative plan and the surgical results, and the accuracy of distance and angle and the stability of the system were analyzed.

RESULTS

The average position deviation between the preoperative design and intraoperative navigation was: 0.01 ± 0.73 mm on the lateral height of the mandibular ramus, 0.26 ± 0.57 mm on the inner height of the mandibular ramus, and 0.20 ± 0.51 mm on the osteotomy length. The average angle deviation is 0.94° ± 1.38° on the angle between the mandibular osteotomy plane and ramus plane and 0.66° ± 0.97° on the angle of the retained mandibular angle. And most of the data showed good consistency.

CONCLUSIONS

In summary, the accuracy of the system can meet clinical requirements and can be used as a useful tool to improve the accuracy of craniomaxillofacial surgery.

A digital photograph study evaluating facial taperness and square face perception of Taiwanese females

BACKGROUND

This study assessed the perception of facial taperness in Taiwanese females among people with dental knowledge and laypersons. Additionally, this study also specified the criteria by which "square face" was defined regarding Taiwanese females' facial taperness.

METHODS

A series of digitally modified photos with different levels of facial taperness (Gonion to Gonion/Zygoma point to Zygoma point-Go-Go/Zy-Zy ratio ranges from 65% to 90%) were randomly arranged and presented to the raters. Visual analog scale (VAS) lines were used for scoring the photos on a scale of 0-100. The true or false question about "defining square face" was incorporated in the same questionnaire. The reliability of the true/false square face question and the esthetic evaluation by VAS were assayed. The receiver operating characteristic curve was used to define the cutoff point on "square face." The effects on the raters' genders, orthodontic treatment experience, and their professional background on the perception of a square face were assayed.

RESULTS

The overall reliability of the raters was within the acceptable range. The VAS score evaluation revealed that the average expectation for best facial taperness was 75%, whereas the facial taperness of over 83% was considered as the square face. The facial taperness reaching to 90% was regarded as the most unattractive. Gender, therapy, and professional experience have no impact on the standard of square facial form evaluation.

CONCLUSION

A face with a taperness greater than 83% was evaluated as a square face, and a face with a taperness around 75% was considered as the most attractive.

Mandibular angle resection using cervicofacial lifting surgical approach: Technical note

Facial feminization surgery brings a set of surgical procedures that address the three thirds of the face and aims to give feminine characteristics to a masculine face. The characteristics of the lower third of a male face are a long, broad chin, a prominent mandible with sharp angles (in connection with the insertions of the masseter muscles). Mandibular angle reduction is an important procedure of the male-to-female transformation. It allows to modify the appearance of the lower third of the face, reducing the bi-mandibular distance in the coronal plane and opening the mandibular angle in profile. The classical procedure uses trans-oral surgical approach. However, patients undergoing male-to-female sexual transformation frequently present a mixed indication of cervicofacial lift and angular resection. We present an innovative surgical technique associating cervicofacial lifting and mandibular angle resection using the same cutaneous surgical approach. We describe its advantages and discuss its disadvantages.

Reducing Prominent Mandibular Angle Osteotomy Complications: 10-Year Retrospective Review

BACKGROUND

Several methods are available for mandibular reduction, and each method is characterized by unique limitations and complications. However, only a few studies have systematically analyzed these complications. This study aimed to investigate the effects of the outcome of performing curved mandibular angle ostectomy and outer cortex grinding in 1-stage operation and to examine the causes of different types and characteristics of complications.

METHODS

The subjects consisted of 528 patients who were subjected to curved mandibular angle ostectomy and outer cortex grinding in 1-stage operation through an intraoral approach. Surgical complications and related factors were recorded, and the rates of complication according to surgeons were simultaneously evaluated.

RESULTS

The esthetic appearance of all of the patients was significantly improved, and they were satisfied with the results of the operation. The complication rate was 5.87%. No serious complications, such as subcondylar fracture, massive bleeding, permanent facial nerve, or asymmetry, occurred. Some complications, including 4 cases of hematoma, 4 cases of severe swelling, 2 cases of infection, and 1 case of sagging face, were detected. The absolute complication rate among faculty members ranged from 3.5% to 11.1%.

CONCLUSIONS

Our protocol is an effective method for mandibular angle osteotomy with very few complications. The rate of complications can be effectively reduced, and some serious complications can be avoided because protective measures are improved.

Application of computer-assisted navigation in mandibular angle osteotomy

Objective

To compare the effectiveness, accuracy, and surgical safety of a navigation technique with those of a traditional technique for intraoperative mandibular angle osteotomy.

Methods

Forty-three postsurgical patients with mandibular angle hypertrophy who were admitted to our Department from June 2014 to June 2017 were retrospectively reviewed. Of these patients, 23 underwent mandibular angle osteotomy using computer-assisted navigation (navigation group), and 20 underwent osteotomy using a traditional technique (traditional group). Postoperative computed tomography images were analyzed by three-dimensional software. Each patient’s facial proportion indices were measured using Mimics 19.0 software, and statistical comparisons and analyses were performed preoperatively and postoperatively.

Results

The postoperative facial contour morphology and facial proportion were improved in both groups; the navigation group showed greater improvement. The difference between the predicted and postoperative values was smaller in the navigation group than traditional group. The postoperative shape of the mandibular angle sample was similar to the preoperative predicted shape in the navigation group. No complications occurred in the navigation group, but paresthesia occurred in 17% of patients in the traditional group.

Conclusions

Mandibular angle osteotomy aided with computer-assisted navigation is more effective, accurate, and safe than the traditional technique and represents a promising clinical approach.

Occlusion-Fit V-Line Guide and Gooseneck Saw for Safe and Accurate Mandibuloplasty in Asians

BACKGROUND

A slender or slim face with narrow facial features is considered esthetically appealing in Asian people. Plastic surgery to obtain an oval face, called a 'V-line,' is popular among young people.

MATERIALS AND METHODS

A total of 20 Korean patients were included in this study. The patients underwent mandibular anguloplasty with three-dimensional computer-aided design and manufacturing surgical guides that were accurately fitted to the upper and lower teeth, allowing for precise replication of a virtual surgery during a real surgical procedure.

RESULTS

There were no significant complications, including severe bleeding, facial nerve injury, or airway obstruction. All patients were satisfied with the esthetic and functional results, except for one who was neutral toward the result. The mean satisfaction score was 4.75, which was between 'satisfied' and 'very satisfied.'

CONCLUSION

The V-line guide and gooseneck saw allowed for safe and fast resection of bone in the mandibular angle area. This technique provides consistent results during surgery as well as minimizing surgical complications.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Cosmetic bone contouring

PURPOSE OF REVIEW

In recent years, cosmetic bone contouring surgery has become increasingly popular, especially in East Asian countries. These procedures are also being requested by patients in the United States at an increasing rate. The purpose of this study is to provide an overview of what is involved with these procedures and their potential complications.

RECENT FINDINGS

In some cultures, a wide jaw and a square face are aesthetically unpleasing, whereas an ovoid or 'melon seed face' is thought to be feminine, delicate and beautiful. Mandibular angloplasty, mandibular lateral cortex excision, reduction malarplasty, as well as genioplasty may be performed to alter the facial contour and bring about dramatic results.

SUMMARY

Whether a surgeon choses to incorporate these procedures into practice or not, the craniofacial surgeons should be familiar with the procedures as well as the potential complications.

A modified intraoral and extraoral approach osteotomy for the prominent mandibular angle

BACKGROUND

A prominent mandibular angle (PMA) is a relatively common condition in Asians, and surgeons typically use the intraoral approach to treat it. However, the approach can have many drawbacks due to the limited operative field and view. The procedures of osteotomy are not easily manipulated, and an exact resection is difficult. In addition, some major complications can easily occur. This article presents a modified osteotomy method for the PMA that avoids these disadvantages and makes the procedure easier to execute.

METHODS

Four modifications of the procedures have been made: 1. The addition of a small extraoral incision in the auriculocephalic sulcus behind the earlobe; 2. A modest reduction in both the intraoral incision length and excessive mouth traction; 3. The use of a reciprocating saw through the extraoral incision tunnel to simplify the operative procedure; and 4. Extraction of sustained-suction drains from the extraoral incision. Postoperatively, all patients were followed up and administered the validated satisfaction questionnaire and the Patient Scar Assessment Questionnaire.

RESULTS

From June 2010 to June 2015, 46 patients with a PMA underwent surgery using this method. All patients were satisfied with the esthetic results. The majority of patients could not feel an objectionable jaw line or bony step (86.9%), visible deformity (97.8%) or bony regrowth (95.6%). All patients noted a positive psychosocial influence. All patients perceived the overall appearance of their extraoral scar to be "good" or "excellent." Forty-five (97.8%) were "not at all" self-conscious of their scar. The overall complication rate was 6.5%, and no major complication was seen.

CONCLUSION

The described method for the surgical treatment of PMA is a simple and safe procedure with fewer complications. The procedure is easy to perform, consumes less time, and can help resect the PMA accurately and easily.

Quantitative Mandibular Angle Ostectomy Facilitated by Oscillating-Blade Saw With Scalable Guide

BACKGROUND

Although various techniques of mandibular angle ostectomy have been devised to correct overly prominent bony contours, none have incorporated methods to delineate the surgical line with precision. Herein, the authors describe one means of marking an ostectomy line more easily, using a specially designed oscillating-blade saw.

METHODS

Between July 2013 and June 2014, a total of 75 patients underwent quantitative mandibular angle ostectomy using a custom oscillating-blade saw equipped with a scalable guide. Corticectomy, also done routinely to improve frontal appearance, called for a reciprocating saw only. Aesthetic outcomes gauged subjectively by the questionnaire about satisfaction and symmetry after postoperative 6 months.

RESULTS

Satisfaction score was 4.9 and symmetric score was 4.7. No major complications, such as persistent nerve injury or fracture, were encountered.

CONCLUSIONS

Use of an oscillating-blade saw equipped with a scalable guide facilitated quantitative mandibular angle ostectomy, enabling precise, and reproducible surgery with satisfactory outcomes with less complications.

Simultaneous surgery for subcondylar fracture and prominent angle of the mandible

We experienced a patient of subcondylar fracture who had a squared contour of the lower face with prominent angle of the mandible and masseter hypertrophy. Our patient was increasingly seeking esthetic improvement of the lower third of the face. But she did not want multi-stage operations. Thus, we decided and performed a one-stage mandibular angle ostectomy with fracture management. We have a stable and esthetic result simultaneously despite fractures of the fixation plates during follow-up period, so report a case.

The Accuracy of Computer Image-Guided Template for Mandibular Angle Ostectomy

BACKGROUND

Mandibular angle ostectomy (MAO) is commonly used to correct prominent mandibular angles through an intraoral approach. However, limited vision in the operative site may lead to difficulties or complications during surgery. Therefore, it is necessary to develop an effective method for helping surgeons to perform MAO more precisely and safely.

METHODS

In this study, we report a novel method of a computer image-guided surgical template for navigation of MAO, and evaluate its accuracy and clinical outcomes. Nine patients with a prominent mandibular angle were enrolled in this study. A pair of stereolithographic templates was fabricated by computer-aided image design and 3D printing. In all cases, bilateral MAO was performed under the guide of these templates. Post-operative effects were evaluated by 3D curve functions and maximal shell-to-shell deviations.

RESULTS

All patients were satisfied with their cosmetic outcomes. The mean and SD of ICC between R-Sim and R-Post were 0.958 ± 0.011; between L-Sim and L-Post, 0.965 ± 0.014; and between R-Post and L-Post, 0.964 ± 0.013. The maximal shell-to-shell deviations between the simulated mandibular contour and post-operative mandibular contour on the right and left sides were 2.02 ± 0.32 and 1.97 ± 0.41 mm, respectively.

CONCLUSION

The results of this study suggest that this new technique could assist surgeons in making better pre-surgical plans and ensure more accurate and safer manipulation for completion of this procedure.

Evaluation of mandibular angle ostectomy using three-dimensional finite element analysis

PURPOSE

This study was designed to investigate the stress and the displacement distributions of the mandible after mandibular angle ostectomy (MAO) by means of three-dimensional finite element analysis.

METHODS

On the basis of a female patient with a prominent angle of the mandible, the finite element models were generated by helical computed tomography and related software and were analyzed under muscle forces and 3 kinds of biting conditions, including intercuspal position (ICP), incisal clenching (INC), and right unilateral molar clenching (RMOL). The mandibular stress and displacement distributions were analyzed by Abaqus software.

RESULTS

In the model of MAO, the increased stress and the decreased displacement was found in ICP, INC, and RMOL at the area of mandibular angle. The stress and the displacement increased in ICP and RMOL, whereas the others remained unchanged in INC at the area of mandibular condylar neck.

CONCLUSIONS

The results of this study have shown that MAO could alter biomechanical characteristics in the operated mandible, which suggested that a greater hit on face may lead to a higher incidence rate of condyle fracture and a lower incidence rate of angle fracture after MAO.

Iatrogenic mandibular fracture associated with third molar removal after mandibular angle osteotectomy

The extraction of mandibular third molars is a common dental procedure. The complications include hemorrhage, pain, dental fracture, the displacement of teeth or fragments, iatrogenic damage or luxation of the second molar, neurologic injuries, soft tissue damage, subcutaneous emphysema, trismus, swelling, infection, and iatrogenic mandibular fracture. Fracture of the angle of the mandible associated with third molar removal is a rare but severe complication. This article describes a case of mandibular angle fracture associated with third molar extraction after mandibular angle osteotectomy, including a brief review of the literature. The removal of the mandibular angle and the outer cortex of the mandible, especially the external oblique ridge, may contribute to the bone fracture. We conclude that the extraction of the lower third molar must be before the removal of the mandibular angle, and a soft diet for at least 4 weeks postoperatively is essential to prevent late mandible fracture.