Effect of maxillary impaction on mandibular surgical accuracy in virtually-planned orthognathic surgery: A retrospective study

Although surgical accuracy has been evaluated in bi-maxillary procedures, few studies have investigated the relationship between maxillary and mandibular accuracy. The present study evaluated the effect of maxillary impaction accuracy on mandibular surgical outcome.This cohort study analyzed skeletal class III patients who underwent planned maxillary impaction in bi-maxillary surgery. The primary predictor was the difference between the virtual plan and surgical outcome in the maxilla, as determined by three-dimensional (3D) and vertical differences. The secondary predictors were the planned 3D distances in the maxilla and mandible. The primary outcome was mandibular surgical accuracy, defined as the difference between the planned and actual outcomes, calculated as 3D Euclidean distance.The study included 73 patients. Increased differences between the planned and actual outcomes in the maxilla were associated with increased differences in the mandible. The post-operative position of the mandible was closer to the planned position when the position of the impacted maxilla was superior than when it was inferior to the planned position.Moving the maxilla closer to the planned position resulted in a more accurate mandibular position. These findings suggest that careful surgical procedures are needed to avoid inferior positioning of the maxilla during maxillary impaction surgery.     

Pre-operative Assessment of Anatomical Position of Inferior Alveolar Nerve and Its Significance in Bilateral Sagittal Split Osteotomy

The aim of this study is to investigate the position and course of the mandibular canal through the ramus, angle and body of mandible using computed tomographic (CT) imaging pre-operatively and to relate these predetermined values intra-operatively to perform sagittal split ramus osteotomies. Pre-operative CT scans were taken and four points were marked at mandibular foramen, mandibular angle, mandibular body and midpoint and different dimensions of IAN were measured to localize the inferior alveolar nerve. With the obtained values, precise osteotomy cuts were made intra-operatively and intra-operative measurements for position of IAN were noted. Based on the preoperative CT measurements, the chance to encounter IAN bundle, during surgery was evaluated. The present study proved that pre-operative CT imaging prior to BSSO surgical procedure is an effective way to investigate the position and course of the IAN canal through the framework of the mandible and by interpolating these dimensions intra operatively, reduces the risk of direct injury to the IAN bundle.     

下颌前突畸形的正颌外科矫治

目的 总结正颌外科矫治下颌前突畸形的临床经验。方法 对32例下颌前突畸形患者进行了正颌外科手术，其中12例行双侧SSRO，4例行双侧IORO，10例行双侧IVRO，5例行上下颌前部根尖下截骨，1例行下颌骨体部截骨，同期搭配施行水平截骨颏成形术12例，畸形涉及上颌骨行LeFortⅠ型截骨9例。结果 32例下颌前突畸形患者术后外观及功能均获得满意效果。并发症有术后下颌前突轻度复发4例，明显复发1例，下颌骨升支骨折一侧1例，下牙槽神经一侧断离1例，结论 随访结果显示应用IVRO，SSRO等术式治疗下颌前突畸形只要术式选择及操作得当，能获得较满意效果。文中就手术方法，注意事项及并发症等进行了讨论。     

Simulation-guided navigation: a new approach to improve intraoperative three-dimensional reproducibility during orthognathic surgery

Because of the recent development of three-dimensional technology, computer software is increasingly being used for diagnosis, analysis, data documentation, and surgical planning for orthognathic surgery. Currently, the typical method to reposition jaws in the correct and planned location is based on the use of surgical splints, which have a quite high level of imprecision. The most important differences between planned and achieved maxillary movements are in the vertical and rotational positioning. Several methods have been described for intraoperative maxillary control, but none of these procedures is satisfactory. We present a new method to transfer individualized three-dimensional virtual planning of the patient using a navigation system in the operating room to improve reproducibility of the simulation. We enrolled 10 patients with dentofacial deformities from November 2008 to May 2009. All patients were studied and treated according to the following steps: cone-beam computed tomography data acquisition, virtual simulation of the surgical procedure, surgery with intraoperative navigation, and validation through reproducibility evaluation. We found 86.5% mean preoperative surgical plan reproducibility with the assistance of simulation-guided navigation compared with 80% mean reproducibility obtained in our previous group, in which no intraoperative navigation was performed. According to these results, we can assume that simulation-guided navigation would be a helpful procedure during orthognathic surgery to improve reproducibility of the preoperative virtual surgical planning.     

The impact of Le Fort I advancement and bilateral sagittal split osteotomy setback on ventilation during sleep

The impact of orthognathic surgery for class III malocclusion on ventilation during sleep was examined using a comparison of pre- and post-surgical respiratory parameters. 21 patients with both maxillary hypoplasia and mandibular excess underwent Le Fort I osteotomy and advancement together with bilateral sagittal split osteotomy (BSSO) setback. Respiratory parameters, ECG and position of the body were monitored before surgery and postoperatively after the fixation removal (mean 8.5 months). Average Le Fort I advancement was 4.44 mm, BSSO setback was 4.96 mm. Generally, the orthognathic procedure worsened breathing function during sleep, as reflected in significant increase of index of flow limitations and decrease in oxygen saturation. The posterior airways space decreased to 75% of its original volume, the distance between mandibular plane and hyoid bone increased to 133%. The results indicate that bimaxillary surgery for class III malocclusion increased upper airway resistance. A young person would probably be able to balance such a decline in respiratory function using different adaptive mechanisms, but the potential impact of orthognathic surgery on the upper airways should be incorporated in a treatment plan.     

Trigeminal nerve hypesthesia after sagittal split osteotomy in setback cases: correlation of postoperative computed tomography and long-term trigeminal somatosensory evoked potentials.

PURPOSE: We sought to assess the relationship of the inferior alveolar nerve to the osteotomy site after bilateral sagittal split osteotomy (BSSO) and to correlate the nerve osteotomy relationship as the cause of long-term postoperative hypesthesia. Patients and Methods: The subjects consisted of 28 patients with mandibular prognathism who underwent BSSO setback surgery. The distance between the ostectomized surface of the mandibular ramus and mandibular canal was measured and scored on a computed tomograph (CT). The relationship between this distance and the presence and degree or absence of trigeminal nerve hypesthesia was objectively evaluated by latency delay of the trigeminal somatosensory evoked potential (TSEP) records. RESULTS: Five of the 56 sides (8.9%) showed latency delays more than 1 year after the operations. Scored CT points between the canal and the split surface strongly correlated with TSEP latency recovery (Y = 1.716X + 41.2). CONCLUSIONS: This relationship between the canal and the osteotomy site is related to long-term hypesthesia in BSSO postoperatively.     

Risk factors of nerve injury during mandibular sagittal split osteotomy

There is little objective data about whether surgical technique or mandibular anatomy are a risk for inferior alveolar nerve (IAN) injury during bilateral sagittal split osteotomy (BSSO). Orthodromic sensory nerve action potentials (SNAPs) of the IAN were continuously recorded on both sides in 20 patients with mandibular retrognathia during BSSO operation. Changes in latency, amplitude, and sensory nerve conduction velocity (SNCV) at baseline and at different stages of the operation were analyzed. The SNAP latencies prolonged, the amplitudes diminished, and the SNCVs slowed down during BSSO (P = 0.0000 for all parameters). The most obvious changes occurred during surgical procedures on the medial side of the mandibular ramus. There was a clear tendency towards more disturbed IAN conduction with longer duration of these procedures (right side R = -0.529. P = 0.02; left side R = -0.605, P = 0.006). Exposure or manipulation of the IAN usually had no effect on nerve function, but the IAN conduction tended to be more disturbed in cases with nerve laceration. Low corpus height (R = 0.802, P = 0.001) and the location of the mandibular canal near the inferior border of the mandible (R = 0.52, P = 0.02) may increase the risk of IAN injury. There was no correlation between the age of the patients and the electrophysiological grade of nerve damage.     

Factors affecting neurosensory disturbance after mandibular bilateral sagittal split osteotomy.

PURPOSE: The current study evaluated the incidence of subjective neurosensory disturbances after bilateral sagittal split osteotomy (BSSO) in relation to gender, age, indication for osteotomy, magnitude of mandibular movement, degree of manipulation of the inferior alveolar nerve at operation, side of the mandible operated, and complications during and after surgery. PATIENTS AND METHODS: Thirty patients (60 sides) who had undergone a BSSO were followed up for 1 year after operation. The patients were classified into different groups according to gender, age, indication for osteotomy, magnitude of mandibular movement, degree of manipulation of the nerve, and complications during or after surgery. A self-administered questionnaire was used at every follow-up to evaluate the sensations in the mental region. RESULTS: A statistically significant positive correlation was found between subjective neurosensory loss and the patient's age (P = .039), magnitude of mandibular movement (P = .044), and degree of manipulation of the nerve (P = .0007). However, no significant correlation was found between disturbances of sensation and gender, indication for osteotomy, side of the operated mandible, or intraoperative and postoperative complications. Even if all patients evaluated their sensation as "normal" 1 year postoperatively, 31% of them reported slightly altered sensation in the mental region. CONCLUSIONS: After BSSO, a prolonged neurosensory deficit is strongly related to age, the intraoperative magnitude of mandibular movement, and the degree of manipulation of the inferior alveolar nerve. However, a long-term sensory loss is very rare, and patients seem to adapt to a mild neurosensory deficit and report sensory function as "normal" despite slightly altered sensation.     

Inferior alveolar nerve injury caused by thermoplastic gutta-percha overextension

Injuries to the inferior alveolar nerve following trauma resulting in a mandibular fracture are well documented and are a well-known risk when surgical procedures are planned for the mandible in the region of the inferior alveolar canal. Such injuries are relatively rare following endodontic therapy. This article reports a case of combined thermal and pressure injury to the inferior alveolar nerve, reviews the pathogenesis of such an injury and makes suggestions for its management.     

下颌骨正颌术后下牙槽神经阻滞麻醉联合帕瑞昔布钠静脉镇痛的临床观察

目的比较正颌手术术后镇痛中,双侧下牙槽神经阻滞麻醉联合帕瑞昔布钠静脉镇痛与单纯静脉镇痛泵的镇痛效果及安全性。方法选择行下颌升支矢状骨劈开术+颏成型术的患者40例,使用随机数字表随机分成观察组和对照组,每组20例,观察组患者采用双侧各2mL 1%罗哌卡因术中下牙槽神经阻滞麻醉,术毕立即予以40 mg帕瑞昔布钠静脉注射,对照组术毕予以静脉自控镇痛泵镇痛。记录两组患者术后2、4、8、24、48 h疼痛强度(VAS疼痛评分)及Ramsay镇静评分,并观察患者术后不良反应的发生情况。结果两组患者术后各时间点疼痛强度、Ramsay镇静评分比较差异无统计学意义(P>0.05)。镇痛治疗期间,观察组患者恶心呕吐的发生率低于对照组(P<0.05)。结论双侧下牙槽神经阻滞联合帕瑞昔布钠静脉镇痛与单纯静脉镇痛泵用于下颌骨正颌手术术后镇痛效果相当,但前者不良反应发生率较低,更适用于下颌骨正颌手术术后镇痛。     

Effect of modified bilateral sagittal split osteotomy on inferior alveolar nerve neurosensory disturbance

The aim of this study was to assess the occurrence of neurosensory disturbance of the inferior alveolar nerve (IAN) following modified mandibular bilateral sagittal split osteotomy (BSSO) that preserves the mandibular inferior border. All patients undergoing BSSO, associated or not with a Le Fort I osteotomy (performed by the same senior operator) between January 2018 and December 2019, were eligible. The modified BSSO consists of a modification of the technique described by Epker: the bony section of the buccal cortex stops 3-4 mm above the basal mandibular edge. While respecting the basilar border, sectioning is then performed up to the gonial angle where bicortical section is finally performed. Sensibility of the labial and chin area was evaluated immediately postoperatively, and at six months and two years of follow up. A total of 140 eligible patients underwent the modified BSSO between January 2018 and December 2019, and 72 were included. Hypoaesthesia was found in 81.9% of the patients (59/72 patients) at initial evaluation. It decreased to 45.8% (33/72 patients) at the six-month examination and to 12.5% (9/72 patients) at the last examination. Four bad splits were recorded. The modified BSSO preserves the inferior border of the mandible and maintains the IAN in the lingual fragment. There is no need to release the IAN, hence its manipulation is reduced and the incidence of IAN postoperative hypoaesthesia is also reduced.     

The impact of mandibular advancement on articulation, resonance and voice characteristics in Flemish speaking adults: a pilot study

Bilateral saggital split osteotomy (BSSO) of the mandible is a frequently performed mandibular orthognathic procedure, used to resolve mandibular disharmonies. Literature review showed contradictory findings regarding the effect of the orthognathic surgery on speech characteristics. The purpose of the present study was to determine a detailed analysis of the articulation, resonance and voice characteristics after BSSO with mandibular advancement for the treatment of Class II malocclusions using objective and subjective assessment techniques (perceptual evaluations, Dysphonia Severity Index, nasalance scores) in eight subjects. The findings of the present study indicate that before and after BSSO with mandibular advancement three types of articulation disorders may predominate in the Flemish language: the incorrect production of the trill sound /r/ and the /s/ sound and devoicing of the /z/. After orthognathic surgery most patients showed an identical articulation pattern (normal or disturbed pattern) as in the presurgical condition. In this study the BSSO with mandibular advancement had no significant impact on the nasality characteristics and the nasalance values probably due to the competent velopharyngeal valving in the presurgical condition. And, as expected the vocal quality revealed no significant difference. The maxillofacial surgeon and the speech language pathologist must be aware of the persistency of these preoperative articulation errors in the postsurgical condition.     

A split ostectomy of mandibular body and angle reduction

Combined mandibular angle resection with angle-splitting ostectomy (ASO) is more effective than conventional simple or multistaged ostectomy. Removal of the outer cortex of the mandibular body by ASO lessens the protuberance of the masseter muscle. In this study, the anatomy of the mandibular canals in seven human cadavers was studied in detail, and a guideline for ASO and mandibular angle ostectomy was set up so as to avoid injury to the inferior alveolar nerve. The most vulnerable area of the inferior alveolar nerve is the line from the gonion (G) to the junction (O) of the intersecting vertical line along the anterior border of the ramus and the horizontal line on the alveolar crest because of the thin anterior distance (AD) between the buccal surface of the mandible and the outer wall of the mandibular canal. The resection line should not be above 17.5 mm at the GO line to ensure a safe inferior distance, the distance between the inferior border of the mandible and the floor of the mandibular canal (21.6 +/- 4.1 mm). The body of the mandible was less vulnerable to injury to the inferior alveolar nerve in ASO because of the relatively thicker AD at the second molar (8.3 mm) and first molar (6.8 mm). Pilot surgery was performed in five cadavers. The lateral cortex was safely split off, avoiding injury to the inferior alveolar nerve, and angle ostectomy was then done. This method was applied in two clinical cases without any complications. The "split ostectomy of mandibular body and angle reduction" is a new and safe method of avoiding the injury to the inferior alveolar nerve.     

Assessment of material- and technique-related complications following sagittal split osteotomies stabilized by biodegradable polylactide screws

OBJECTIVE: The aim of this retrospective clinical study was to determine whether there are any material-related problems and increased occurrence of postoperative mandibular nerve and temporomandibular joint dysfunctions in connection with the use of biodegradable self-reinforced poly-L-lactide (SR-PLLA) screws for bone fixation after bilateral sagittal split osteotomies (BSSO). STUDY DESIGN: Forty consecutive patients who underwent BSSO and mandibular advancement that included fragment fixation using SR-PLLA screws were monitored for an average of 2.2 years postoperatively. RESULTS: The osteotomy sites healed uneventfully with no adverse reactions. The incidence of postoperative sensory disturbances of the inferior alveolar nerve was 27%. Symptoms of temporomandibular joint disorders (TMJD) observed preoperatively in 73% of patients were reduced to 48% after surgery. CONCLUSION: The occurrence of postoperative sensory disturbances and TMJD symptoms in this study did not deviate strikingly from that of other studies using conventional osteosynthesis. No specific complications related to the screw material were observed.     

Extraoral vertical ramus osteotomy combined with internal fixation for the treatment of mandibular deformities

Extraoral vertical ramus osteotomy (EVRO) is used in orthognathic surgery for the treatment of mandibular deformities. Originally, EVRO required postoperative intermaxillary fixation (IMF). EVRO has been developed using rigid fixation, omitting postoperative IMF. We examined retrospectively the long-term stability and postoperative complications for patients with mandibular deformities who underwent EVRO with internal rigid fixation. Patients who were treated with EVRO for a mandibular deformity in the period 2008–2017 at the Clinic of Oral and Maxillofacial Surgery, Mölndal, Sweden were included (N = 26). Overjet and overbite were calculated digitally and cephalometric analyses were performed preoperatively, and at three days, six months, and 18 months postoperatively. There was a general setback of the mandible, decreased gonial angle and reduced degree of skeletal opening. Excellent dental and vertical skeletal stabilities were seen up to 18 months postoperatively, although relapse was seen sagitally up to six months postoperatively. Since the overjet did not show any significant change over time, the sagittal skeletal changes have been attributed to dental compensation. There was no permanent damage to the facial nerve and 5.8% neurosensory damage to the inferior alveolar nerve was observed.     

Distraction osteogenesis versus bilateral sagittal split osteotomy for advancement of the retrognathic mandible: a review of the literature

Bilateral sagittal split osteotomy (BSSO) and distraction osteogenesis (DO) are the most common techniques currently applied to surgically correct mandibular retrognathia. It is the responsibility of the maxillofacial surgeon to determine the optimal treatment option in each individual case. The aim of this study was to review the literature on BSSO and mandibular DO with emphasis on the influence of age and post-surgical growth, damage to the inferior alveolar nerve, and post-surgical stability and relapse. Although randomized clinical trials are lacking, some support was found in the literature for DO having advantages over BSSO in the surgical treatment of low and normal mandibular plane angle patients needing greater advancement (>7 mm). In all other mandibular retrognathia patients the treatment outcomes of DO and BSSO seemed to be comparable. DO is accompanied by greater patient discomfort than BSSO during and shortly after treatment, but it is unclear whether this has any consequences in the long term. There is a need for randomized clinical trials comparing the two techniques in all types of mandibular retrognathia, in order to provide evidence-based guidelines for selecting which retrognathia cases are preferably treated by BSSO or DO, both from the surgeon's and the patient's perspective.     

冠根分次去除法在疑或累及下牙槽神经的下颌第三阻生磨牙拔除术中的应用

目的:评价应用截冠法分次拔除紧贴下牙槽神经的下颌阻生第三磨牙的效果。方法:对10例术前全景片及CT均显示牙根紧贴或接触下牙槽神经的下颌阻生第三磨牙患者采用截冠留根法,于釉-牙骨质界去除阻力牙冠,包埋牙根于牙槽骨内;术后观察,待牙根移动远离下牙槽神经后再行拔除术。结果:10例患者术后反应轻微,均无下牙槽神经损伤,无感染情况出现;仅1例牙根未能上移至远离下牙槽神经的位置,留根于牙槽骨内,牙龈创面愈合,随访1年无不适。结论:根尖紧贴或接触下牙槽神经的下颌阻生第三磨牙,经截冠留根术后,断根有上移萌出趋势,可远离下牙槽神经管,后期拔除断根,可明显降低下牙槽神经损伤的风险。     

Changes in the temporomandibular joint position depending on the sagittal osteotomy technique and extent of mandibular movement

The bilateral sagittal split osteotomy (BSSO) and high oblique sagittal split osteotomy (HSSO) are common techniques for mandibular movement in orthognathic surgery. The aim of this study was to evaluate the influence of both techniques, as well as movement distances and directions, on the position of the temporomandibular joint (TMJ). A total of 80 mandibular movements were performed on 20 fresh human cadaver heads, four on each head. Pre- and postoperative cone beam computed tomography was used to plan the surgical procedure and analyse the TMJ. Reference measurements included the anterior, superior, and posterior joint spaces, intercondylar distances and angles in the axial and coronal planes, and the sagittal, coronal, and axial angulations of the proximal segment. Only minor differences were found between the BSSO and HSSO techniques, particularly in terms of the intercondylar angle in the axial plane (P < 0.03) and the condylar angle of the proximal segment in the sagittal plane (P < 0.011). Observed changes in the TMJ were mostly opposite when moving the mandible forwards and backwards and increased with increasing movement distance. BSSO and HSSO result in similar changes in TMJ position. The extent of the movement distance influences the position of the condyle more than the osteotomy technique.     

Original sagittal split osteotomy revisited for mandibular distraction

Introduction: A malformed mandible and an abnormally positioned mandibular foramen make it difficult to plan an ideal osteotomy line for mandibular distraction. In addition, there have been reports of such complications as nonunion, damage and stretch injury of the inferior alveolar nerve and tooth germ damage when conventional osteotomy or corticotomy are used for mandibular distraction. The authors utilized the original sagittal split ramus osteotomy for mandibular distraction. Patients and Methods: Five patients (three unilateral hemifacial microsomia, one bilateral hemifacial microsomia, and one mandibular retrusion) were included in this study of distraction osteogenesis using the sagittal split ramus osteotomy. Extraoral distraction devices were applied to the first four patients. An intraoral device with mono-cortical screw fixation was used for the fifth patient. Result: In all five cases, the results of the distraction were satisfactory. Complications (as listed) of conventional osteotomy when used for distraction were avoided. Satisfactory results were achieved and these were also well maintained postoperatively (mean follow up: 36 months). Conclusion: The authors believe that sagittal osteotomy for mandibular distraction osteogenesis makes it possible, to avoid injury to the inferior alveolar nerve during operation and stretching injury during distraction and to prevent tooth germ injury. It is also possible to diversify the osteotomy line for various force vectors to enlarge the bony contact surface area. Therefore, we suggest that sagittal split ramus osteotomy should be used as a preferred modification of osteotomy for mandibular distraction. Copyright 2001 European Association for Cranio-Maxillofacial Surgery.     

Original sagittal split osteotomy revisited for mandibular distraction.

INTRODUCTION: A malformed mandible and an abnormally positioned mandibular foramen make it difficult to plan an ideal osteotomy line for mandibular distraction. In addition, there have been reports of such complications as nonunion, damage and stretch injury of the inferior alveolar nerve and tooth germ damage when conventional osteotomy or corticotomy are used for mandibular distraction. The authors utilized the original sagittal split ramus osteotomy for mandibular distraction. PATIENTS AND METHODS: Five patients (three unilateral hemifacial microsomia, one bilateral hemifacial microsomia, and one mandibular retrusion) were included in this study of distraction osteogenesis using the sagittal split ramus osteotomy. Extraoral distraction devices were applied to the first four patients. An intraoral device with mono-cortical screw fixation was used for the fifth patient. RESULT: In all five cases, the results of the distraction were satisfactory. Complications (as listed) of conventional osteotomy when used for distraction were avoided. Satisfactory results were achieved and these were also well maintained postoperatively (mean follow up: 36 months). CONCLUSION: The authors believe that sagittal osteotomy for mandibular distraction osteogenesis makes it possible, to avoid injury to the inferior alveolar nerve during operation and stretching injury during distraction and to prevent tooth germ injury. It is also possible to diversify the osteotomy line for various force vectors to enlarge the bony contact surface area. Therefore, we suggest that sagittal split ramus osteotomy should be used as a preferred modification of osteotomy for mandibular distraction.