Maxillary Posterior Impaction Research Articles

"Gearing Effect in Clockwise Rotational Orthognathic Surgery".

The standard procedure for the management of skeletal class III malocclusion is maxillary advancement with mandibular setback. Occlusal plane altering orthognathic surgery, such as jaw rotation, is useful as well. Although clockwise jaw rotation is a common procedure, its mechanism has not been well-investigated. Therefore, in this study, we aim to introduce the gearing effect to correct class III malocclusion in Asians by maxillary posterior impaction via clockwise rotation without advancing the maxilla. Patients with class III correction with clockwise rotation of the maxillomandibular complex without maxillary advancement were included, while those with genioplasty were excluded. Various facial skeletal cephalometric landmarks were measured through artificial intelligence based cephalometric analysis software. The gearing effect was determined by dividing the lower anterior facial height (LAFH) in relatively short and long groups compared to those in the ANS‒PNS length. In a total of 29 patients, the amount of Menton setback between group 1 (n=15, short LAFH) and group 2 (n=14, long LAFH) was 1.67±0.66 and 2.74±0.99 mm per 1 mm of PNS impaction, respectively (p=0.002), and 1.58(interquartile range(IQR) 0.78) and 1.95(IQR 1.05) mm per 1° clockwise rotation of palatal angle, respectively (p=0.007). The convexity of the A point was improved without any significant change in the SNA angle before and after surgery. This article addressed the scientific evidence in impact of clockwise rotational orthognathic surgery based on the gearing effect. Considering the gearing effect, the mandibular setback turned out to be more effective in patients with a long LAFH.

A learning curve in 3D virtual surgical planned orthognathic surgery

ObjectivesTo assess the surgical accuracy of 3D virtual surgical planned orthognathic surgery and the influence of posterior impaction and magnitude of the planned movements on a possible learning curve.Materials and methodsThis prospective cohort study included subjects who underwent bimaxillary surgery between 2016 and 2020 at the Department of Oral and Maxillofacial Surgery of the Radboud University Medical Center, Nijmegen. 3D virtual surgical planning (VSP) was performed with CBCT data and digitalized dentition data. By using voxel-based matching with pre- and postoperative CBCT data the maxillary movements were quantified in six degrees of freedom. The primary outcome variable, surgical accuracy, was defined as the difference between the planned and achieved maxillary movement.ResultsBased on 124 subjects, the surgical accuracy increased annually from 2016 to 2020 in terms of vertical translations (0.82 ± 0.28 mm; p = 0.038) and yaw rotations (0.68 ± 0.22°; p = 0.028). An increase in surgical accuracy was observed when combining all six degrees of freedom (p = 0.021) and specifically between 2016 and 2020 (p = 0.004). An unfavorable learning curve was seen with posterior impaction and with a greater magnitude of movements.ConclusionThe present study demonstrated a significant increase in surgical accuracy annually and therefore supports the presence of a learning curve.Clinical relevanceCases with planned maxillary posterior impaction and/or a great magnitude of jaw movements should be transferred from the 3D VSP with extra care to obtain a satisfactory surgical accuracy.

A Simple Method to Retract the Descending Palatine Neurovascular Bundle During Osseous Removal of Posterior Interferences in Le Fort I Osteotomy.

For accurate repositioning of the maxilla in Le Fort I osteotomy, bone removal around the descending palatine neurovascular bundle and maxillary tuberosity is frequently required. Such task can be challenging due to the high vascularity of the region, which is the most common site of hemorrhage during removal of bony interferences. Although a rare occurrence, ligation of the descending palatine artery in cases of intraoperative vascular damage can be related to the development of aseptic necrosis. This article reports a simple technique for retraction and protection of the descending palatine neurovascular bundle during bony removal related to a posterior maxillary impaction, which can be easily reproduced in orthognathic selected cases.

Postoperative changes in the pharyngeal airway space through computed tomography evaluation after mandibular setback surgery in skeletal class III patients: 1-year follow-up

BackgroundThis study evaluated the pharyngeal airway space changes up to 1 year after bilateral sagittal split osteotomy mandibular setback surgery and bimaxillary surgery with maxillary posterior impaction through three-dimensional computed tomography analysis.MethodsA total of 37 patients diagnosed with skeletal class III malocclusion underwent bilateral sagittal split osteotomy setback surgery only (group 1, n = 23) or bimaxillary surgery with posterior impaction (group 2, n = 14). Cone-beam computed tomography scans were taken before surgery (T0), 2 months after surgery (T1), 6 months after surgery (T2), and 1 year after surgery (T3). The nasopharynx (Nph), oropharynx (Oph), hypopharynx (Hph) volume, and anteroposterior distance were measured through the InVivo Dental Application version 5.ResultsIn group 1, Oph AP, Oph volume, Hph volume, and whole pharynx volume were significantly decreased after the surgery (T1) and maintained. In group 2, Oph volume and whole pharynx volume were decreased (T2) and relapsed at 1 year postoperatively (T3).ConclusionIn class III malocclusion patients, mandibular setback surgery only showed a greater reduction in pharyngeal airway than bimaxillary surgery at 1 year postoperatively, and bimaxillary surgery was more stable in terms of airway. Therefore, it is important to evaluate the airway before surgery and include it in the surgical plan.

Management of skeletal class III malocclusion by surgery-first approach: A case report

The purpose of Dentofacial Deformity Treatment is to achieve the proper aesthetic and function- al occlusion results. Conventional orthognathic surgery involves a long-term orthodontic phase before surgery for about 18 months, in which patients’ facial appearance worsens and their mo- tivation decreases. In the SFA (surgery first approach) method, the surgery is performed before orthodontics and orthodontic therapy is performed to improve dental occlusion and final settle- ment. Two main advantages of this method are the reduction of the therapy period and the initial improvement in the patient’s facial appearance. The SFA has certain benefits, especially in Class 3 malocclusion. In this case report, a 19-year-old girl with a relatively severe Class 3 malocclu- sion with skeletal discrepancy due to a mandibular prognathism and maxillary retrognathism, and asymmetrical face with chin deviation to left is presented with a unilateral posterior cross bite which was effectively treated using the SFA protocol. The SFA therapy was performed by removing orthodontics before surgery, followed by maxillary advancement surgery, and posterior maxillary impaction and postoperative orthodontic sets to dental alignment and settling the occlusion. De- spite the overall reduction in the orthodontic therapy period to less than 9 months, good results and functional occlusion were obtained.

Positional changes in the mandibular proximal segment after intraoral vertical ramus osteotomy: Surgery-first approach versus conventional approach.

ObjectiveTo compare postoperative positional changes in the mandibular proximal segment between the conventional orthognathic surgery (CS) and the surgery-first approach (SF) using intraoral vertical ramus osteotomy (IVRO) in patients with Class III malocclusion.MethodsThirty-eight patients with skeletal Class III malocclusion who underwent bimaxillary surgery were divided into two groups according to the use of preoperative orthodontic treatment CS group (n = 18) and SF group (n = 20). Skeletal changes in both groups were measured using computed tomography before (T0), 2 days after (T1), and 1 year after (T2) the surgery. Three-dimensional (3D) angular changes in the mandibular proximal segment, condylar position, and maxillomandibular landmarks were assessed.ResultsThe mean amounts of mandibular setback and maxillary posterior impaction were similar in both groups. At T2, the posterior portion of the mandible moved upward in both groups. In the SF group, the anterior portion of the mandible moved upward by a mean distance of 0.9 ± 1.0 mm, which was statistically significant (p < 0.001). There were significant between-group differences in occlusal changes (p < 0.001) as well as in overjet and overbite. However, there were no significant between-group differences in proximal segment variables.ConclusionsDespite postoperative occlusal changes, positional changes in the mandibular proximal segment and the position of the condyles were similar between CS and SF, which suggested that SF using IVRO achieved satisfactory postoperative stability. If active physiotherapy is conducted, the proximal segment can be adapted in the physiological position regardless of the occlusal changes.

Influence of mandibular setback surgery on three-dimensional pharyngeal airway changes

The aim of this study was to investigate the factors influencing three-dimensional changes in pharyngeal airway space after mandibular setback surgery. Airway changes in 48 skeletal class III patients who had undergone mandibular setback surgery alone (n=25, group 1) or with maxillary surgery (n=23, group 2) were analyzed. Linear parameters, cross-sectional area, and volumes of the pharyngeal airway were evaluated before (T0), immediately after (T1), and 1year after surgery (T2) by cone beam computed tomography. Although the reduced airway volume and cross-sectional area recovered slightly in the long term after surgery, the total pharyngeal airway volume (TPV) was significantly reduced compared to baseline, by 15% in group 1 and 12% in group 2. Regression analysis showed that maxillary posterior impaction in two-jaw surgery had a protective effect on preserving TPV. A change in body mass index from T0 to T2 was an important predictor of decreased TPV in one-jaw surgery patients. Maxillary posterior impaction can be a reliable option for compensating the pharyngeal airway reduction after mandibular setback surgery. Postoperative weight gain can increase the risk of postoperative pharyngeal airway reduction. Therefore, these factors need to be considered before and after mandibular setback surgery.

Three-Dimensional Analysis of Midfacial Soft Tissue Changes After Maxillary Posterior Impaction and Intraoral Vertical Ramus Osteotomy for Mandibular Setback in Class III Patients.

This study investigated the correlation between the 3-dimensional changes in midfacial soft tissues, including the parasagittal area and maxilla-mandible complex, after Le Fort I maxillary posterior impaction and bilateral intraoral vertical ramus osteotomy (B-IVRO), using cone-beam computed tomography (CBCT). This retrospective study included 22 skeletal Class III patients (6 men and 16 women; mean age 21.6 years) who underwent orthognathic surgery. Three-dimensional CBCT images taken before and 1 year after surgery were superimposed based on the cranial base. Midfacial soft tissues, including those in the parasagittal area (paranasal area, anterior cheek area, lateral cheek area) and midsagittal areas of the face, were evaluated using reconstructed CBCT images. Correlations and the ratios between soft tissue and hard tissue movement were calculated. After surgery, both paranasal areas showed significant forward movement (about 2.0 mm) and the largest upward movement (about 0.15 mm) among the 3 areas. The paranasal areas moved forward with a ratio of 0.5, according to vertical movement of B. Orthognathic surgery using Le Fort I maxillary posterior impaction with B-IVRO mandibular setback results in forward movement of midfacial soft tissues, even though sagittal movement of the maxilla is limited because facial muscles and retaining ligaments pull the redundant soft tissues, which are caused by vertical movement of the maxilla-mandible. This midfacial soft tissue change with maxillary posterior impaction could be advantageous to patients who have paranasal depression and protrusion of the upper lip owing to proclined upper incisors, which are prevalent among Asian Class III patients.

Change of the airway space in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction.

BackgroundThe purpose of this retrospective study was to develop a two- and three-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether the airway space would be changed in mandibular prognathism after bimaxillary surgery involving maxillary posterior impaction.MethodsPatients requiring orthognathic surgery from 2012 to 2014 were recruited for this study. CBCT scans were obtained at three points: preoperatively (T0), immediate postoperatively (T1), and after 6 months postoperatively (T2). The nasopharynx, oropharynx, and hypopharynx were measured on the CBCT scan for each patient in a repeatable manner. With the midsagittal plane, linear measurements in the middle of each were obtained. For the CBCT, volumetric measurements of each and total airway were obtained.ResultsA total of 22 consecutive patients (11 men and 11 women) were included in the present study. The total volume was significantly reduced (p < .001). However, the change of the diameter and volume of the nasopharynx was not statistically significant (p = .160, p = .137, respectively). In the oropharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p < .001, p = .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p = .010, respectively). In the hypopharynx, the change of both the diameter and volume showed statistical significance between preoperatively and immediate postoperatively (p = .001, p < .001, respectively) and also preoperatively and after 6 months postoperatively (p = .001, p < .001, respectively).ConclusionsThe bimaxillary surgery involving maxillary posterior impaction can reduce the volume of airway in the patients of mandibular prognathism. Although total airway volume was reduced significantly, the changes in the volume and diameter of the nasopharynx were not statistically significant. The maxillary posterior impaction affects on the nasopharyngeal airway minimally.

Clockwise and Counterclockwise Le Fort I Movements Influence Nasolabial Morphology Differently

Le Fort I advancement impacts nasal appearance. However, no data exists assessing 3D nasal change following anterior (counterclockwise, CCW) or posterior maxillary impaction (clockwise, CW) during Le Fort I osteotomy. The purpose of this study was to analyze nasolabial changes comparing CW to CCW maxillary movements.

Contributing factors to intraoperative clockwise rotation of the proximal segment as a relapse factor after mandibular setback with sagittal split ramus osteotomy

The aims of this study were to analyze possible contributing factors to intraoperative clockwise rotation (CWR) of the proximal segment (PS), which is known to be a primary factor for relapse after mandibular setback with sagittal split ramus osteotomy (SSRO) and to evaluate the correlation between the CWR of the PS and relapse tendency. The sample was comprised of 47 patients who underwent SSRO for mandibular setback. Lateral cephalograms were analyzed. The vertical difference between the inferior borders of the PS and the distal segment at the vertical osteotomy line for SSRO after setback of the distal segment (vertical bony step, VBS) was the most predictable factor for CWR of the PS (p < 0.001), and it correlated significantly with the gonial angle, the surgical change in SNB, and the downward movement of the maxilla (p < 0.05). Patients with large CWR of the PS showed a greater tendency in horizontal relapse than patients with small CWR of the PS (p < 0.05). Such relapse patterns could be prevented with adequate surgical planning designed to reduce the VBS, such as maxillary posterior impaction or the intentional guidance of the PS to maintain the original position of the PS without CWR.

Do Patients Treated With Bimaxillary Surgery Have More Stable Condylar Positions Than Those Who Have Undergone Single-Jaw Surgery?

Because condylar positioning after sagittal split ramus osteotomy of the mandible has been known to affect postoperative skeletal stability, accurate positional assessment of the temporomandibular joint after orthognathic surgery is vital to maximize stability of the surgery. The purpose of this study was to evaluate condylar changes after single-jaw and double-jaw surgeries in mandibular prognathism patients by comparing 3-dimensional angular and positional changes of the condylar heads in groups of patients receiving combined maxillary posterior impaction and mandibular setback and those undergoing only mandibular setback surgeries. We assessed condylar changes of patients who have been diagnosed with mandibular prognathism and underwent either bimaxillary surgery or isolated mandibular surgery at Kangdong Sacred Heart Hospital and SmileFuture Orthodontic Clinic, Seoul, South Korea, from August 2008 to February 2011. Condylar angulation, intercondylar distance, and amount of condylar displacement were examined based on the 3-dimensional reconstructed images. Preoperative and postoperative changes within each group were assessed by paired t test. Differences between the groups were determined by independent t test. A total of 43 skeletal Class III patients were included in this retrospective, multicenter study. After single-jaw surgery, condylar angulations in all dimensions did not change. In contrast, those who received double-jaw surgery showed forward rotation of 1.93° (P = .027) and medial rotation of 1.48° (P = .032) in the sagittal and axial planes, respectively. The mean distances of condylar displacements were 0.28 ± 0.44 mm in the single-jaw group and 0.31 ± 0.51 mm in the double-jaw group, but there was no statistically significant difference. Condylar angulations are more stable after sagittal split ramus osteotomy of the mandible as an isolated procedure than in combination with the posterior maxillary impaction in treatment of skeletal Class III malocclusion patients. Condylar displacements in both the single-jaw and double-jaw groups are clinically insignificant.

Study about the relationship between the amount of posterior impaction and the change of occlusal plane angle and incisor inclination in Le Fort I osteotomy

Introduction: In the management of dentofacial deformities, variable movement of the maxilla can be made possible by a Le Fort I osteotomy. Posterior impaction of the maxilla necessary for rotation of the maxillomandibular complex enhances the functions and esthetic results. In cases of posterior impaction of the maxilla, an increase in the figure of the occlusal plane angle and incisor inclination can occur. Th is study reports the relationship between the amount of posterior impaction and the change in the occlusal plane angle and incisor inclination in a Le F ort I osteotomy by preoperative and postoperative lateral cephalograms. Materials and Methods: Twenty patients who had undergone orthognathic surgery in Dong-A University Medical Center participated in this study. Lateral cephalometrics, within 3 weeks prior to surgery and 3 days after surgery, were used for analysis. Pre and postoperative measurements of the occlusal plane angle and incisal inclination based on the Frankfort horizontal (FH) plane were performed. X and Y were defined as the amount of vertical change in the upper incisor tip and the amount of vertical change in the upper first molar mesial cup tip through the ope ration. The amount of final posterior maxillary impaction was determined by subtracting Y from X, which is the difference in vertical height. Accordi ng to the amount of posterior maxillary impaction, the change in the occlusal plane angle and incisal inclination was measured. Results: The average posterior maxillary impaction was 2.91 mm and the average change in the occlusal plane angle and incisal inclinatio n was 6.54�after surgery. As a result, each mm of posterior maxillary impaction changed the occlusal plane angle and incisal inclination b y 2.25� . Statistically, there was high significance. Two cases were observed: one with the same amount of posterior maxillary impaction performed on both the right and left showing 2.20� , and the other with a different amount of posterior maxillary impaction performed showing 2.35 � . In this case, there was no significance difference between the two cases. Conclusion: Each mm of posterior maxillary impaction changes the occlusal plane angle and incisal inclination by an average of 2.25 � . In posterior maxillary impaction, there was no significant difference in the amount of change in the occlusal plane angle and incisal inclin ation regardless of whether there was an equal amount of posterior maxillary impaction on both sides. This study is expected to help in the presurg ical orthodontic preparation and presurgical treatment planning.

The Relation Between Pogonion Advancement and Posterior Maxillary Impaction

Controversy exists about the relation between the amount of posterior maxillary impaction and pogonion (P) advancement. The aims of the current study were to (1) propose a formula to predict the amount of P advancement due to posterior maxillary impaction surgery, (2) predict the amount of posterior maxillary impaction by means of a formula to achieve the best facial harmony, and (3) identify the compatibility between proposed formulas and the actual resultant mandibular position after posterior maxillary impaction surgery. For obtaining the formulas, 2 cephalograms were taken from 1 patient in centric occlusion and rest position. Afterward, mandibular rotational center was obtained by superimposing the cephalograms; by the help of which the 2 formulas were obtained. To check the reliability of the formulas, 10 patients with the mean age of 21 +/- 1.5 years who had undergone posterior maxillary impaction were selected. The presurgical and postsurgical cephalograms of patients were obtained. These cephalograms were superimposed to find the center of mandibular rotation. Pearson correlation coefficient test was used to evaluate the relation between the suggested formulas and the clinical data. This test showed that there were significant correlations between maxillary impaction and P advancement in both the formulas and clinical evaluation. This correlation (r) was 0.993 (P < 0.001) based on formulas and r = 0.806 (P < 0.005) based on tracing. This study showed that the amounts of anterior facial height reduction and P advancement were almost the same, and the anterior facial height was reduced 1.5 times more than the amount of maxillary impaction.

Osteotomy Assisted Maxillary Posterior Impaction with Miniplate Anchorage

This case report presents orthodontic treatment with miniplate anchorage accelerated by osteotomy-assisted maxillary posterior impaction in a severe open bite case. A 14-year-old girl with a severe anterior open bite was treated by intrusion of the maxillary posterior teeth. A segmental osteotomy was applied, and the miniplates were fixed to the zygomatic buttress area. The intrusive force was applied with nickel-titanium closed coil springs using a force of 250 g between the miniplates and the upper first and second molar buccal tubes. The intrusion was completed 2.5 months after osteotomy. The treatment was continued with the fixed orthodontic appliances and completed after 12 months. At the end of treatment, optimal occlusion and the correction of the anterior open bite were achieved. The maxillary molars were impacted 4.0 mm, and the mandibular plane showed a counterclockwise autorotation of 3.0 degrees . The results showed that osteotomy-facilitated orthodontic treatment clearly reduced the treatment time and had no adverse effects. In conclusion, this one-stage osteotomy technique can be an effective option to help molar intrusion in severe open bite cases.

Bilateral Congenital Trigeminal Sensorimotor Neuropathy Presents as a Severe Open-Bite Malocclusion

Trigeminal neuropathy is commonly seen as a disorder of sensation in the distribution of the fifth cranial nerve. An 18-year-old girl was referred to our hospital because of a severe anterior open-bite deformity with a long face after presurgical orthodontic treatment. Surgical plan was maxillary posterior impaction with anterior advancement, mandibular setback operation, and genioplasty with vertical chin reduction in one stage. One month after surgery she had still difficulty closing her mouth. With the help of her hands, she could close her mouth fully on normocclusion. Weakness of the jaw-closing muscles was confirmed with muscle testing. She had impaired sensation to light touch and pinprick in the distribution of the maxillary and mandibular divisions of the bilateral trigeminal nerves. T1-weighed MRI of the brain showed bilaterally atrophy of the muscles innervated by the trigeminal motor nerve (i.e., the masseter, medial and lateral pterygoids, and temporalis muscles). We thoroughly evaluated our patient through history and clinical, laboratory, electrophysiological, and radiological examinations. The motor and the sensory V2 and V3 branches of the trigeminal nerve were congenitally damaged. As far as we know, this case is the first bilateral congenital trigeminal sensorimotor neuropathy presented with maxillo-mandibular and a severe open-bite deformity.

A relatively minor adult case becomes significantly complex: A lesson in humility

A 41-year-old white woman with no particular concerns about facial esthetics was first seen with bilateral Class II molar relationship, a Class I right canine, and a Class II left canine. Overjet was 3 mm and overbite was 0.5 mm, with no incisor contact. A maxillary right premolar was missing for unknown reasons and all 4 third molars had previously been extracted. The maxillary midline was 2 mm to the right of the facial midline, and the mandibular midline was 3.5 mm to the left of the maxillary midline. There was 7 mm of crowding in the maxillary arch and 6 mm of crowding in the mandibular arch, with an increased curve of Spee. The patient had a well-positioned maxilla, a retrognathic mandible with increased convexity, a Class II denture base relationship, and a vertical facial pattern. The treatment plan consisted of extracting the maxillary left first premolar and the mandibular left central incisor. After 4 months of treatment, an open bite from second premolar to second premolar was noted. After 6 months of treatment, the patient expressed concern with her chin position and mentalis hyperactivity. It was apparent that the orthodontic treatment had resulted in molar extrusion, which the musculature was not able to withstand. Treatment continued and the case was set up for posterior maxillary impaction and mandibular advancement surgical procedures.