Setback Of Mandible Research Articles

Relapse patterns of two-jaw surgical correction in patients with skeletal Class III malocclusion and different vertical facial types

The aim of this study was to evaluate postoperative relapse after the surgical correction of skeletal Class III deformities of various facial patterns as a guide to surgical planning. A retrospective cohort study of 90 consecutive patients with skeletal Class III malocclusion who underwent bimaxillary surgery was performed. The surgical outcomes and postoperative stability were compared. The primary predictor variable was vertical facial type, which was classified into three groups according to the Frankfort mandibular plane angle (FMA). The primary outcome of angular and linear measurements was obtained using serial cone beam computed tomography scans obtained at time points of preoperative, 1 week after surgery, and orthodontic debonding. No significant difference in skeletal relapse was observed in patients with the different vertical facial types. The mandible displayed a forward and upward relapse in all three groups postoperatively. The patients with a low FMA exhibited a more consistent mandibular relapse pattern than those with a normal or high FMA. These findings suggest that bimaxillary surgery is clinically stable for mandibular prognathism regardless of the vertical facial pattern. However, 1–1.5 mm of overcorrection in the mandible setback should be considered in patients with a low FMA, because of the greater facial depth and consistent forward and upward mandibular relapse pattern.

Changes in Tongue Area, Pharyngeal Area, and Pharyngeal Airway Velocity after Correction of Mandibular Prognathism.

This study aimed to investigate the correlation between the amount of mandibular setback, and the related changes of the tongue area, pharyngeal area, and pharyngeal airflow velocity. Twenty-five patients treated for mandibular prognathism, and serial cephalograms were obtained (T1: preoperation, T2: more than one year postoperation). The postoperative area of the tongue, pharyngeal airway space, and pharyngeal airflow velocity were investigated. Statistical analysis was performed with the Student t-test and Pearson correlation. The amount of mandible setback was significant after surgery (12.8 mm; p < 0.001). The pharyngeal area was significantly reduced 115.5 mm2 (p = 0.046). There was a slight reduction of the tongue area (43.2 mm2; p = 0.305) and an increase of pharyngeal airflow velocity (0.3 m/s; p = 0.133). The Pearson correlation coefficient test showed no statistical significance among the amount of horizontal setback and vertical movement of the mandible, such as the reductions in the tongue area, the pharyngeal airway space, and the increase in pharyngeal airflow velocity. Larger amounts of mandibular setback caused a significant reduction of pharyngeal airway area, but without significant changes of the tongue area and pharyngeal airflow velocity.

Effects of different surgical techniques and displacement distances on the soft tissue profile via orthodontic-orthognathic treatment of class II and class III malocclusions

BackgroundOrthognathic surgery can be carried out using isolated mandibular or maxillary movement and bimaxillary procedures. In cases of moderate skeletal malocclusion, camouflage treatment by premolar extraction is another treatment option. All these surgical procedures can have a different impact on the soft tissue profile.MethodsThe changes in the soft tissue profile of 187 patients (Class II: 53, Class III: 134) were investigated. The treatment approaches were differentiated as follows: Class II: mandible advancement (MnA), bimaxillary surgery (MxS/MnA), upper extraction (UpEX), or Class III: maxillary advancement (MxA), mandible setback (MnS), bimaxillary surgery (MxA/MnS), and lower extraction (LowEX) as well as the extent of skeletal deviation (moderate Wits appraisal: − 7 mm to 7 mm, pronounced: Wits <− 7 mm, > 7 mm, respectively). This resulted in five groups for Class II treatment and seven groups for Class III treatment.ResultsIn the Class II patients, a statistically significant difference (p ≤ 0.05) between UpEX and moderate MnA was found for facial profile (N′-Prn-Pog’), soft tissue profile (N′-Sn-Pog’), and mentolabial angle (Pog’-B′-Li). In the Class III patients, a statistically significant differences (p ≤ 0.05) occurred between LowEX and moderate MxA for facial profile (N′-Prn-Pog’), soft tissue profile (N′-Sn-Pog’), upper and lower lip distacne to esthetic line (Ls/Li-E-line), and lower lip length (Sto-Gn’). Only isolated significant differences (p < 0.05) were recognized between the moderate surgical Class II and III treatments as well between the pronounced Class III surgeries. No statistical differences were noticed between moderate and pronounced orthognathic surgery.ConclusionsWhen surgery is required, the influence of orthognathic surgical techniques on the profile seems to be less significant. However, it must be carefully considered if orthognathic or camouflage treatment should be done in moderate malocclusions as a moderate mandibular advancement in Class II therapy will straighten the soft tissue profile much more by increasing the facial and soft tissue profile angle and reducing the mentolabial angle than camouflage treatment. In contrast, moderate maxillary advancement in Class III therapy led to a significantly more convex facial and soft tissue profile by decreasing distances of the lips to the E-Line as well as the lower lip length.

Ortho-surgical management of class iii malocclusion: A case report

Class III malocclusion is considered to be one of the most difficult and complex orthodontic problems to treat. Prevalence of class III malocclusion in Caucasians ranges from 0.8 to 4.0% and rises up to 1213% in Chinese and Japanese populations, while in North Indian population, class III malocclusion is found in up to 3.4% of the population. A 19 years old boy who reported with chief complaint of poor smile because of forwardly placed lower jaw from 2 years. Treatment plan of orthodontic treatment first and surgery later was planned. The upper and lower arches were aligned until a 0.019” x 0.025” stainless steel archwire could be placed. . Bilateral sagittal split osteotomy with short lingual split was carried out using surgical saws. 05 mm set back of mandible was performed. After 06 weeks class III elastics and settling elastics were given. Keywords: Surgical, Prediction, Class III malocclusion

Postsurgical changes of mandible based on vertical dimension increase in Skeletal Class III deformities

The aim of this study was to evaluate the postsurgical mandibular changes after surgery based on vertical dimension increase in skeletal Class III deformities.Patients who underwent mandibular setback surgery for skeletal Class III malocclusion correction with surgery-first orthognathic treatment were enrolled in the study. Lateral cephalograms were obtained at initial visit, immediately after surgery, 6 months after surgery, and at post-treatment. Postsurgical change of the mandible based on the vertical dimension increase was estimated using a diagrammatic method before surgery and this amount was compared with the actual amount of mandibular forward movement at 6 months after the surgery, using a paired t-test and Bland–Altman plot.Thirty patients (16 men and 14 women; mean age, 22.6 years) with skeletal Class III deformities had undergone mandibular setback surgery with the surgery-first orthognathic treatment. Immediately after surgery, the mandible setback was 9.4 ± 3.7 mm at pogonion. Six months after surgery, the mandible moved forward at an average of 2.3 ± 1.5 mm which corresponded to the estimated value of 2.2 ± 0.9 mm. The estimated amount of postsurgical movement did not show a statistically significant difference from the actual value on paired t-test (p = 0.349). The Bland–Altman analysis showed that the difference between the two values was within the limits of agreement.The postsurgical changes based on vertical dimension increase in surgery-first orthognathic treatment might be predicted by using a diagrammatic method.

Three-dimensional assessment of condylar position following orthognathic surgery using the centric relation bite and the ramal reference line: A retrospective clinical study.

Orthognathic surgery (OGS) is a relatively common procedure for solving functional and aesthetic problems in facial and jaw areas in patients with dentofacial deformities. The positioning of the mandibular condylar segment during OGS has an impact on the surgical outcome. This study aimed to investigate the changes in the condyle-fossa relationship three dimensionally after OGS using the centric relation (CR) bite and the ramal reference line (RRL).Thirty-two patients with skeletal malocclusion underwent OGS. Condylar repositioning was performed using the CR bite, as previously reported. A RRL was added to the existing method and used during the surgery. Cone-beam computed tomography scans were acquired at 4 time points. Sixty-four condyles were evaluated in the coronal, sagittal, and axial views. Two groups were created according to the amount of mandible setback (SB1 vs SB2), and another 2 groups were created according to the maxillary operation (1-jaw vs 2-jaw). Each was then compared at the 4 time points. Differences between the values before (T0) and a year after surgery (T3) were also investigated. The positions of the pogonion and the menton were examined at T2 and T3 for the simple evaluation of relapse.The change in the condylar position was significant over a time-course (P < .001) but not between T0 and T3 (P > .05). Neither the setback amount nor the maxillary operation affected the positional change (P > .05). There were no significant changes between T2 and T3 in the relapse evaluation.This condylar repositioning method using the CR bite and a RRL showed stable results after OGS. This method is noninvasive and cost-effective and can be easily performed even by an inexperienced surgeon because it reduces errors in repositioning the condyle during OGS.

Stability of biodegradable metal (Mg–Ca–Zn alloy) screws compared with absorbable polymer and titanium screws for sagittal split ramus osteotomy of the mandible using the finite element analysis model

Mg–Ca–Zn alloy has been suggested for the application of fixation materials during maxillofacial surgery. We investigated the stability of Mg–Ca–Zn alloy for clinical application during orthognathic surgery. The finite element model for the fixation of sagittal split ramus osteotomy was constructed. In the bicortical screw fixation of the mandible setback condition, the stress distributions of Mg–Ca–Za alloy, polylactic acid polymer, and titanium were evaluated using the virtual model with occlusal loading of 132 N. The deformations of the three different materials of fixation screw were observed according to masticatory force ranging from 132 to 1,000 N. When comparing the stress distribution placed on cortical bone between the polymer and magnesium alloy groups, the magnesium alloy screws could bear more stress, thereby decreasing the stress, which might be distributed to other biologic components, such as the condyle and cortical ramus of the mandible. Deformations of the screws according to functional load were minimal, and the deformation remained <0.21 mm at the initial functional load of the mandible after surgery, regardless of materials used. The biodegradable magnesium alloy screw can bear more stress and decrease the detrimental effect on the stability of sagittal split ramus osteotomy setback surgery.

Retrospective study of changes in pharyngeal airway space and position of hyoid bone after mandibular setback surgery by cephalometric analysis.

BackgroundThe posterior movement of mandible was known as the main cause of the changes in the pharyngeal airway space (PAS) and the postoperative obstructive sleep apnea (OSA). The purpose of this study was to know the changes of PAS and position of hyoid bone.MethodsLateral cephalographies of 13 patients who had undergone sagittal split ramus osteotomy (SSRO) setback surgery were taken preoperatively (T1), postoperatively within 2 months (T2), and follow-up after 6 months or more (T3). On the basis of F-H plane, diameters of nasopharynx, oropharynx, and hypopharynx were measured. The movements of the soft palate, tongue, and hyoid bone were also measured.ResultsThe amount of mandible setback was 7.5 ± 3.8 mm. In the measurements of PAS, there was a statistically significant decrease of 2.8 ± 2.5 mm in nasopharynx (P < 0.01), and 1.7 ± 2.4 mm in oropharynx (P < 0.01) were observed after surgery. The hypopharynx decreased 1.0 ± 2.1 mm after surgery and continuously decreased 1.0 ± 2.8 mm at follow-up. The changes in hyoid bone position showed the posterior movement only after surgery and posteroinferior movement at follow-up.ConclusionsThe PAS such as nasopharynx, oropharynx, and hypopharynx showed relatively high correlation with the amount of mandibular setback. The change of resistance in upper airway may be important for the prevention of OSA after mandibular setback surgery.

Analysis of 40 Cases of Intraoral Verticosagittal Ramus Osteotomies to Treat Dentofacial Deformities

The aim of the present study was to report the experience of 40 patients who had undergone intraoral verticosagittal ramus osteotomy (IVSRO) to treat dentofacial deformities. The charts of 40 consecutive patients who had undergone IVSRO were analyzed regarding the diagnosis, amount of mandibular movement, and complications. Eighty IVSROs were performed in 40 patients. The mean follow-up was 18 months. Mandibular protrusion in both genders was the main preoperative diagnosis (25 patients), and the treatment was 2-jaw surgery in 36 patients. The mean amount of movement was 2 mm for the mandible setback and advancement, 3 mm for mandible counterclockwise rotations, and 2 mm for mandible clockwise rotations. The mean period of maxillomandibular fixation was 15 days, followed by a period of heavy elastics. The rate of complications was 2%, including 2 bad splits, and 2 cases of intraoperative bleeding. No nerve injury was observed in the 40 patients studied. The IVSRO is efficient and versatile, with low morbidity, and is an option for the oral and maxillofacial surgeon to treat patients with mandibular dentoskeletal discrepancies.

How the Lower Face Soft Tissue Changes After Mandibular Advancement or Setback

To contribute as an auxiliary tool for orthodontic and orthognathic planning and treatment, short-term changes on the lower face soft and hard tissues were investigated. All subjects presented adequate maxillary relation with the cranial base. The treatment was done by mandibular advancement in patients with skeletal class II or setback in skeletal class III, by the same oral surgeon, using the same technique, and rigid internal fixation. Lateral cephalograms were traced at the following intervals: T0--immediately before the surgical procedure, T1--6 months after surgery, and T2--1 year after surgery. The postoperative data of the lower face revealed highly significant changes for the soft tissue pogonion and lower lip, in the mandible advancement cases, whereas the underlying bone and dental structures remained constant. For the mandible setback cases, just the hard tissue pogonion variable displayed a statistically significant change.

Sagittal split osteotomy of the mandible without postoperative intermaxillary fixation. A clinical and cephalometric study.

A modified sagittal split technique has been evaluated in 42 dentate patients, in whom no postoperative intermaxillary fixation was used. Twenty-three patients had mandible set-back performed and 19 patients mandibular advancement. The method makes possible a safe split osteotomy under controlled conditions. The design of the osteotomy and screw osteosynthesis counteracts relapse. Omitting intermaxillary fixation facilitates postoperative handling of the patient and promotes rehabilitation.