Stabilisation of sagittal split advancement osteotomies with miniplates: a prospective, multicentre study with two-year follow-up. Part II. Radiographic parameters

The Stability of Anterior Open Bite Closure After Bimaxillary Osteotomy

Introduction

The aim of this study was to evaluate the long-term success rate of combined surgical-orthodontic therapy of skeletal anterior open bite.

Materials and Methods

A total of 11 patients with an anterior open bite treated with a combined surgical-orthodontic therapy were retrospectively analysed via lateral cephalometric radiographs and models before treatment, 7-10 days after surgery (T1), one year post-operatively (T2) and two years post-operatively (T3).

Results

Ten patients continued to experience a positive overbite at T2. This decreased to 8 at T3. Three patients experienced relapse and had a negative overbite at T3. The average pre-treatment overbite was greater in the positive overbite group compared to the relapse group. Spearman's correlation analysis revealed a correlation between preoperative maxilla-mandibular plane angle (MMPA) with the overall change in overbite. Friedman's test followed by Bonferroni post-hoc analysis was carried out to identify any statistical significance.

Conclusion

In conclusion, combined surgical-orthodontic treatment achieves good results for anterior open bite. Patients with a high pre-operative MMPA have a higher risk of relapse. Lower anterior facial height ratio to total anterior facial height (LAFH/TAFH) and the amount of impaction do not significantly contribute to the risk of relapse. Long-term stability of overbite for anterior open bite patients should be around 75%.

Long-Term Follow-Up of Orthognathic Surgery in 19 Patients with Juvenile Idiopathic Arthritis

Objectives

Dentofacial deformity following juvenile idiopathic arthritis with temporomandibular joint involvement is associated with functional, aesthetic, and psychosocial impairment. Surgical treatment may involve combinations of orthognathic surgery. The aims of this retrospective study were to assess orofacial symptoms, functional and aesthetic status, and stability after orthognathic surgery.

Material and Methods

Nineteen patients with juvenile idiopathic arthritis of the temporomandibular joint (TMJ) and dentofacial deformities were included. All patients were treated with combinations of bilateral sagittal split osteotomy, Le Fort I and/or genioplasty, between September 10, 2007 and October 17, 2017. Analysis of patient symptoms and clinical registrations, and frontal/lateral cephalograms was performed pre- and postoperative and long-term (mean: 3.8 and 2.6 years, respectively).

Results

Patients experienced no changes in orofacial symptoms or TMJ function, and stable normalisation of horizontal and vertical incisal relations at long-term (horizontal overbite; vertical overbite: P < 0.05). Mandibular lengthening was achieved postoperatively (from mean 79.7 to 87.2 mm; P = 0.004) and was stable. Sella-nasion to A point (SNA) and sella-nasion to B point (SNB) angles increased postoperatively (SNA, mean 79.9° to 82.8°; P = 0.022 and SNB, mean 73.9° to 77.8°; P = 0.003), however, largely reverted to preoperative status at long-term.

Conclusions

Orthognathic surgery normalized incisal relations while providing stable mandibular lengthening without long-term deterioration of temporomandibular joint function or orofacial symptoms. No long-term effect on jaw advancements was observed.

Treatment Effects and Lip Profile Changes Following Surgical Mandibular Advancement Versus Premolar Extractions in Class II Div 1 Malocclusion: A Randomized Controlled Trial

ABSTRACT

No randomized controlled trial has compared the treatment outcome between surgical mandibular advancement and premolar extractions in class II malocclusion. This 2-arm parallel randomized controlled trial evaluated the treatment effects and lip profile changes in skeletal class II adult patients subjected to bilateral sagittal split ramus osteotomy for mandibular advancement and those treated with premolar extractions. Seventy skeletal class II patients were accessed and forty-six subjects who fulfilled inclusion criteria were distributed randomly into Group CG (patients: 23, mean age: 21.28 ± 2.69 years) and Group SG (patients: 23, mean age: 21.15 ± 2.64 years). Group CG was subjected to extraction of maxillary first premolars and mandibular second premolars followed by implant supported space closure and Group SG was managed by surgical mandibular advancement. Skeletal, dental, and soft-tissue changes were analyzed. The study was single-blinded (statistical analyzer). Groups were closely matched for baseline parameters. In the present trial there was no loss to follow-up. Though overjet and overbite were optimized in both the groups but significant improvement was seen in surgical cases. Group CG demonstrated statistically significant point "A" remodeling, dentoalveolar changes, and increase in nasolabial angle. Group SG exhibited significant sagittal and vertical skeletal improvement and lip position change. Surgical mandibular advancement was found to be a better treatment modality compared to premolars extraction for managing skeletal class II div 1 malocclusion as it permits greater improvement of the profile and skeletal relationship.

Functional Outcomes Following Temporomandibular Joint Dissection Performed During Surgery for Skull Base Tumors

BACKGROUND

During skull base tumor surgery, temporomandibular joint (TMJ) dissection is commonly performed. The impact of this procedure on patients' postoperative diet and TMJ function is a matter of concern to surgeons.

METHODS

We reviewed the Craniomandibular Index (CMI) for 32 patients (15 men and 17 women) who underwent TMJ dissection during surgery for skull base tumors between August 2015 and May 2018.

RESULTS

Fifteen patients underwent removal of the mandibular condyle, and 17 had the condyle preserved. Twenty-one patients mainly underwent infratemporal fossa approach, and 11 underwent extended temporal bone resection. No significant difference between pre- and postoperative diet was observed in any group. Significant differences in CMI index were seen in all groups. The highest score was 0.115 of Dysfunction Index, observed postoperatively in the group that underwent condyle removal.

CONCLUSIONS

For skull base tumor surgery, TMJ dissection has no significant impact on postoperative diet. Patients who underwent removal of the mandibular condyle have significantly worse postoperative TMJ function.

Patient satisfaction after orthognathic surgery: a 3 year follow-up of 60 high-angle Class II individuals

BACKGROUND AND OBJECTIVES

High-angle Class II malocclusion is considered challenging to treat to a stable result and, although studies report treatment outcome in terms of morphology, patient satisfaction has not been addressed. The objectives of the present study were to examine patients' motives for treatment and satisfaction with the results.

MATERIAL AND METHODS

A structured questionnaire was distributed 3 years post-operatively to 93 consecutively treated patients with an initial diagnosis of mandibular-plane angle (ML/NSL) ≥34.0 degrees and ANB angle ≥4.0 degrees. Three surgical subsamples were defined: one-piece Le Fort I, bilateral sagittal split osteotomy, or a combination of the two (Bimax). Lateral cephalometric radiographs were used to assess morphological characteristics and post-treatment changes.

RESULTS

Questionnaire participation was 69.8 per cent. The most frequently reported motives for seeking treatment were to improve oral function (85.0 per cent) and dental appearance (71.7 per cent). Thirty per cent were very satisfied, 53.3 per cent were satisfied, and 16.7 per cent were dissatisfied with the overall treatment result. Dissatisfaction was associated with a persisting post-treatment anterior open bite (AOB), horizontal relapse at B point, and with sensory impairment.

CONCLUSIONS AND IMPLICATIONS

A higher rate of dissatisfaction was found than what has usually been reported for othognathic surgical patients, and this was associated with a persisting AOB. In addition, mandibular relapse and impaired sensory function were related to dissatisfaction and are associated with mandibular surgery. Prospective high-angle Class II patients should be comprehensively informed about the unpredictability of treatment outcomes in terms of occlusion and facial appearance.

Analysis of Sagittal Position Changes of the Condyle After Mandibular Setback Surgery Across the Four Different Types of Plating Systems

The authors analyzed the three-dimensional postoperative condylar position change across the plating systems. This retrospective study was conducted with the patients who underwent bilateral sagittal split ramus osteotomy with setback surgery. The condylar change was analyzed from preoperative cone-beam computed tomography to postoperative 1 month (T1) and postoperative 6 months (T2) using superimposition software, automatically merging based on the anterior cranial base. The condylar changes during T1 and T2 were analyzed across the four types of plates (4-hole sliding, heart-shaped, 3-hole sliding, and 4-hole conventional) Mean intraclass correlation coefficient values were consistently high for each measurement (>0.850). During T1, the conventional plate had a decreased condylar anterior distance when compared with the 3-hole sliding plate (P = 0.032). During T2, the conventional plate had an increased condylar posterior distance when compared with the 3-hole sliding plate (P = 0.031). Superimposition software based on the anterior cranial base could be available for measurement of condylar position with highly reproducible results. After bilateral sagittal split ramus osteotomy, the 3-hole sliding plate could effectively compensate for the anterior displacement of the condyle compared to other plates.

One-year stability of the mandibular advancement and counterclockwise rotation for correction of the skeletal class II malocclusion and high mandibular plane angle: Dental and skeletal aspect

Background

The purpose of this study was to evaluate the stability on dental and skeletal aspect after surgical advancement and counterclockwise rotation for the correction of the mandibular deficiency in patients with high mandibular plane angle (MPA).

Methods

We analyzed the records of patients who had undergone surgical treatment for dentofacial deformities with mandibular deficiency and high MPA. Clinical and radiological data were taken 1 month before surgery (T0), 6 weeks after surgery (T1) and 1 year after surgery (T2). Cephalometric values of the MPA were recorded and compared. The cephalometric changes in the different time periods were defined as follows: A: postsurgical changes (T0–T1), B: one-year changes (T1–T2), and C: short term changes (T0–T2).

Results

Twenty-seven patients had prominent mandibular deficiency with an MPA of over 35° (high angle). The mean age of patients at surgery was 29.7 years. Seven patients had a single jaw procedure, 20 patients had bilateral sagittal split osteotomy (BSSO) combined with a Le Fort I osteotomy, and 14 patients had additional genioplasty. MPA values differed significantly between the time periods (p < 0.05) with an observed relapse of the angle. However, satisfactory clinical improvement was achieved in the dental and skeletal presentation. The overjet improvement was evident from 8.815 ± 2.085 mm (T0) to 3.426 ± 1.253 mm (T2).

Conclusion

Counterclockwise surgical advancement of the mandible to correct mandibular deficiency in patients with a high mandibular plane angle showed an overall acceptable stability during one-year follow-up.

Body postural realignment in the first 2 months after orthognathic surgery

INTRODUCTION

This study aimed to assess the static posture in patients with Angle Class II and III malocclusions in the first 2 months after orthognathic surgery.

METHODS

This was a longitudinal observational study. Eligible participants were adult patients who had an indication of orthognathic surgery (bilateral sagittal split osteotomy of the maxilla and/or mandible, can be associated or not with genioplasty). Thirty-five patients were evaluated from the orthognathic surgery group (OSG) and control group (CG). Measurements in OSG were performed at 3 time points: preoperative orthognathic surgery (P0), first postoperative month (P1), and second postoperative month (P2). Static posture was evaluated using the PostureScreen Mobile (PostureCo Inc, Trinity, Fla) application in 4 views.

RESULTS

Patients with Angle Class II malocclusion in the OSG evidenced a tendency to a left hip translation at P1 with a significant difference at P2 in the anterior view (P = 0.052). In the right lateral view, patients with Angle Class II malocclusion in the OSG at P1 presented an accentuated anterior shoulder translation when compared with CG (P <0.001). At P1, patients with Angle Class II malocclusion in the OSG showed a significant anterior knee translation compared with the CG and OSG at P0 and P2 (P <0.001 for all). Patients in the OSG with Angle Class III malocclusion presented an average posterior head translation in the right lateral view at P1 when compared with those in the CG and OSG at P0, who presented an anterior translation (P = 0.0008).

CONCLUSIONS

These findings suggest a realignment of static posture in the first 2 months after orthognathic surgery.

Upper airway changes following high oblique sagittal split osteotomy (HSSO)

The aim of this study was to evaluate volumetric changes of the posterior airway space (PAS) following bimaxillary surgery using a high oblique sagittal split osteotomy (HSSO) of the mandibular ramus. The cone beam CTs of Class II and Class III patients taken before (T0) and 6-12 months after surgery (T1) were analyzed using 3D software (Mimics® Innovation Suite 18.0). The PAS was divided into three segments (superior, middle, inferior) by three planes parallel to the Frankfurt horizontal plane intersecting at the posterior nasal spine, the velum palatinum and the epiglottis. Total (TPAS) and partial volumes (SPAS = superior, MPAS = middle, IPAS = inferior) were calculated. For the 25 Class II patients, a highly significant increase (p<0.001) of the total, middle and inferior airway space (TPAS: +33.6%, MPAS: +43.1%, IPAS: +55.9%) was found, while the increase of the upper airway space was statistically not significant (+5.4%, p = 0.074). For the 28 Class III patients, the total, middle and inferior airway space increased statistically insignificantly (TPAS: +4.6%, p = 0.265, MPAS: +2.7%, p = 0.387, IPAS: +2.8%, p = 0.495), while the increase of the upper airway space was statistically significant (+9.7%, p = 0.010). Bimaxillary orthognathic surgery using the HSSO technique led to a significant increase of PAS for Class II patients and could conserve the PAS for Class III patients.

Bimaxillary surgery to correct high-angle class II malocclusion: does a simultaneous genioplasty affect long-term stability?

BACKGROUND AND OBJECTIVES

High-angle skeletal Class II malocclusion is one of the most challenging dentofacial deviations to treat and, in adults, a combination of orthodontic treatment and bimaxillary orthognathic surgery is often indicated. This study examines the rate of clinically significant relapse and whether a genioplasty affects the treatment outcome of high-angle Class II malocclusions.

MATERIAL AND METHODS

Cephalometric tracings of 36 consecutively treated high-angle Class II patients were evaluated from pre-surgery to 3 years post-surgery. All patients had undergone bimaxillary surgery (Le Fort I and BSSO), 13 of them had in addition a genioplasty.

RESULTS

The maxilla remained stable, whereas relapse (greater than or equal to 2 mm) of the mandibular advancement was seen in 40 per cent of the patients. Advancement greater than 10 mm increased the risk for horizontal relapse. The overjet was normalized and remained stable despite mandibular relapse. Half of the patients had an anterior open bite 3 years post-surgery. A supplemental genioplasty did not affect the relapse rate.

CONCLUSIONS AND IMPLICATIONS

Overjet was normalized and remained stable long term; there was an open bite in half of the patients. Combined orthodontic and bimaxillary surgical treatment of high-angle Class II patients showed skeletal relapse (greater than or equal to 2 mm) of the mandible in 40 per cent of patients. Mandibular advancement greater than 10 mm increased the risk for relapse. There was no increased risk for dental or skeletal instability associated with a genioplasty in combination with maxillary and mandibular surgery in the treatment of high-angle skeletal Class II malocclusion.

Biomechanical effect of asymmetric mandibular prognathism treated with BSSRO and USSRO on temporomandibular joints: a three-dimensional finite element analysis

Asymmetric mandibular prognathism is a clinically common skeletal dentomaxillofacial deformity. Unilateral sagittal split ramus osteotomy (USSRO) is an effective alternative procedure to bilateral sagittal split ramus osteotomy (BSSRO) for some patients. However, the biomechanical effect of temporomandibular joint (TMJ) of USSRO has not been fully studied. This study aims to evaluate the stress distribution changes in the TMJ of asymmetric mandibular prognathism treated with BSSRO/USSRO, to validate the clinical feasibility of USSRO. Nineteen patients with mandibular prognathism patients who were treated with BSSRO (n=12) and USSRO (n=7) had preoperative and postoperative computed tomographic scanning. Preoperative and postoperative 3-dimensional finite element analysis (FEA) of functional TMJ movements were made on one BSSRO patient and one USSRO patient. In all patients, the ANB angle and mandibular deviation were significantly improved postoperatively. There was no significant difference in the postoperative ANB angle and mandibular deviation between the BSSRO group and the USSRO group. In two preoperative FEA models, the maximum stresses of non-deviation side TMJ structures were greater than the deviation side during functional movements. The unbalanced stress distribution was corrected postoperatively in both BSSRO/USSRO FE models. Both BSSRO/USSRO can improve the ANB angle and mandibular deviation. The bilateral TMJ structure in patients with asymmetric mandibular prognathism had unbalanced stress, which could be significantly improved with the USSRO as effectively as BSSRO.

Study of the mechanical reliability of an S-shaped adjustable osteosynthesis plate for bilateral sagittal split osteotomies. Study on 15 consecutive cases

INTRODUCTION

The main challenge during the osteosynthesis of a bilateral sagittal split osteotomy (BSSO) is to take into account the correct position of the condyle. Adjustable plates can be used to fine-tune the final occlusion without changing the osteosynthesis. A new type of adjustable plate is presented in this article. The aim is to assess the mechanical reliability of this system during the surgery and during the healing period, thanks to a preliminary prospective on 15 consecutive cases.

MATERIAL AND METHODS

The bridge of the plate studied here has an "S"-shape and can be bent in two different planes. Fifteen patients presenting a maxilla-mandibular disharmony have been operated on with this device. Clinical results were evaluated three months postoperatively and the mechanical reliability of the device was studied prospectively from teleradiographies of 15 patients operated on in our department.

RESULTS

This study shows good results, with respect to the mechanical reliability of this S-shaped adjustable plate, three months postoperatively corresponding to the bone-healing period. Radiographic observations did not show any significant displacement at the osteosynthesis site.

DISCUSSION

This preliminary study shows the mechanical reliability of this new S-shaped adjustable plate. Its semi-rigid character may allow for certain condyle position adaptability. No plate fracture was reported for this 15 patient series. These encouraging results have to be confirmed on a larger series.

The effect of bone mass and architecture on mandibular condyle after mandibular distraction

OBJECTIVE

Mandibular distraction surgery is a critical treatment for jaw deformity. However, abnormal mandibular condylar bone resorption is often seen as complication after surgery. Our previous study using a rat mandibular distraction model suggested that overloading leads to mandibular condylar resorption. Host factors are also believed to influence the resorption. To understand the relationship between host factors and resorption, we investigated the effect of changing bone mass and architecture on the mandibular condyle using FK506.

STUDY DESIGN

FK506, an immunosuppressant, was used to compromise bone mass and architecture in this study. Animals were divided into 4 groups: distraction surgery (Dist), FK506 administration (FK), distraction surgery with FK506 administration (FK + Dist), and no surgery or FK506 administration (Cont).

RESULTS

The FK group showed reduced bone mass and impaired bone architecture. The Dist group exhibited abnormal bone resorption on the surface of the condyles, which was slightly exacerbated in the FK + Dist group. Bone defect length decreased over time as a result of bone apposition in the Dist group. However, in the FK + Dist group, the bone defect length remained the same.

CONCLUSIONS

These results suggest that bone mass and architecture strongly affect the tolerance to the overloading and adaptation with bone apposition in condylar resorption site.

The effect of orthognathic surgery on the temporomandibular joint and oral function: a systematic review

The objective of this systematic review was to examine the effect of orthognathic surgery (OS) on the temporomandibular joint and oral function. Electronic databases were systematically searched for studies published until October 2015. Articles were assessed against predefined inclusion criteria. The included papers were divided into four groups based on the type of OS performed. The following items were recorded: quality of evidence using the Oxford Centre for Evidence-Based medicine (CEBM) criteria, number of patients, presence/absence of controls, mean age at treatment, follow-up time, clinical examination findings, bite force, use of the Helkimo Index and Research Diagnostic Criteria for Temporomandibular Disorders, imaging findings, and patient questionnaire results. A total of 4669 articles were identified; 76 relevant articles were included in the review. These studies assessed a total 3399 patients and 380 controls, with a mean age of 25.4 years. The great variety of OS techniques, examination techniques, diagnostic criteria, and imaging techniques used in the articles studied, as well as the quality of the study designs, made it difficult to compare studies and to draw conclusions. However, looking at the different aspects studied in general, it can be stated that OS seems to have little or no harmful effect on the TMJ and oral function (level of evidence: levels II, III, and IV).

Transoral Fixation of Bicortical Screws Is Safe and Feasible for Lower Jaw Osteotomies

PURPOSE

Transoral placement of bicortical screws is a rigid fixation method in orthognathic surgery that is used less often than transbuccal placement. The aim of this study was to examine the postoperative outcome of transoral bicortical screw insertion during orthognathic surgery and to compare it with the more common transbuccal fixation technique.

MATERIALS AND METHODS

A retrospective cohort study was conducted. Clinical files of orthognathic surgery patients operated on from January 2010 through December 2012 were reviewed. Screw insertion approach (transoral vs transbuccal) was examined as a predictive variable for postoperative complications (hardware removal and infection). Type of surgery, fibrin sealant, preoperative third molar removal, and patient age and gender were analyzed as potential risk factors. Descriptive and bivariate statistics and regression analyses were performed.

RESULTS

Of the 606 patients whose cases were reviewed, 509 patients (185 men; mean age, 26.3 ± 11.1 yr) met the inclusion criteria. Most presented with a Class II malocclusion (84.5%). A transbuccal approach was used in 27.5% of cases, leading to a screw-related infection of 6.3%. Patients treated with a transoral technique (72.5%) had fewer infections (3.5%), but this was not statistically relevant. Screw removal was indicated in 3.3% of patients. Screw placement using the transoral and transbuccal approaches was performed in 3.0 and 4.2% of patients, respectively. Infection and screw removal rates did not differ significantly between fixation techniques (P = .16 and P = .49, respectively).

CONCLUSION

The present findings showed an overall low rate of screw removal and infection secondary to bicortical screw insertion during orthognathic surgery. The postoperative outcome was similar for the transoral and transbuccal approaches.

Mechanical evaluation of six techniques for stable fixation of the sagittal split osteotomy after counterclockwise mandibular advancement

We have evaluated the resistance to displacement of six stable methods of fixation of a sagittal split ramus osteotomy (SSRO) in the mandibular advancement with counterclockwise rotation. We tested 60 synthetic hemimandibles in six groups of 10 each: Group I - fixation with a straight four-hole 2.0mm miniplate; Group II - a straight six-hole 2.0mm miniplate; Group III - two straight 2.0mm four-hole miniplates; Group IV - an eight-hole 2.0mm (grid plate); Group V - a 2.0mm four-hole straight miniplate and 2.0×12mm bicortical screw; and Group VI - a straight four-hole 2.0mm locking miniplate. We applied a linear force in the region between the canine and the first premolar using a universal testing machine (EMIC- DL2000) with a loading cell of 10 KN. The loads at 1, 3, and 5mm displacement were recorded (N) and the data transmitted from the load cell to a computer. Results were analysed using analysis of variance (ANOVA) (p<0.001) and the Tukey post-test for comparison of the significance of the differences between the groups. For the three degrees of displacement, fixation with two straight 2.0mm plates and with the grid plate gave higher load values.

Evaluation of the rigidity of sagittal split ramus osteotomy fixation using four designs of biodegradable and titanium plates--a numerical study

PURPOSE

This study was conducted to determine the best design of biodegradable plates for providing rigidity when used for fixation of sagittal split ramus osteotomy.

METHODS

A computerized tomography image of a patient was used to generate a 3D model of a hemi-mandible. Four plate designs were merged with the hemi-mandible. They were (1) straight plate, (2) double straight plate, (3) T-shaped plate, and (4) double Y-shaped plate. Four finite element models were analyzed using the properties of biodegradable materials for the plates, and four additional models were analyzed using titanium alloy properties.

RESULTS

The models predicted that rigidity of fixation would be noticeably less among biodegradable plates than titanium plates. They also predicted that the most rigid design among the titanium plates would be the straight plate, but among the biodegradable plates, it would be the double Y-shaped plate.

CONCLUSION

The double Y-shaped design is recommended when using biodegradable plates in fixation of sagittal split ramus osteotomy.

Assessment of sagittal split ramus osteotomy rigid internal fixation techniques using a finite element method

In this study, finite element analysis (FEA) was used to evaluate nine rigid internal fixation techniques for sagittal split ramus osteotomy. To achieve this, a computed tomography (CT) scan of a healthy patient was obtained and used to generate the geometry of a half-mandible. The geometries of bicortical screws, miniplates, and monocortical screws were designed and combined with the mandible in nine models simulating various techniques. Four models used bicortical screws in various arrangements and four used miniplates of various designs. One model represented a hybrid technique. A load of 500 N was applied to the posterior teeth and FEA was applied. The most stable techniques were the hybrid technique and a single straight miniplate, presenting the least displacement among all models. Bicortical screws, while presenting reasonable stability, showed high strain areas near the anterior ramus ridge, superoposterior to the screws, implying a risk of bone fracture in this area. On the other hand, the T-shaped and double Y-shaped miniplates were associated with high von Mises stresses that would impair their rigidity, especially where angles appeared in their designs. We recommend the use of a single straight miniplate because it provides sufficient stable fixation with minimal risks or disadvantages.

Skeletal stability after bilateral sagittal split osteotomy or distraction osteogenesis of the mandible: a randomized clinical trial

A randomized clinical trial was carried out to evaluate postoperative stability after mandibular advancements in non-syndromal class II patients with a bilateral sagittal split osteotomy (BSSO) or distraction osteogenesis (DO). In total 32 patients could be included in the BSSO group and 34 patients in the DO group. The BSSO was converted to a unilateral procedure for one patient, and two patients in the BSSO group were lost during follow-up. A total 63 patients could be evaluated, 29 in the BSSO group and 34 in the DO group. Advancement was comparable in the two groups (mean 7.2mm). The mean follow-up period was 23.8 months (range 11-50 months). Lateral cephalograms were hand-traced. Horizontal relapse was measured in Y-B (mm) and SNB (°). For DO this was -0.324 mm and -0.250°, and for BSSO this was -0.448 mm and -0.259°, respectively (both not significant; NS). Vertical relapse measured in X-B was -0.074 mm for DO and -0.034 mm for BSSO (NS). The magnitude of advancement, a high mandibular plane angle, age and gender were not identified as independent risk factors for relapse. In conclusion, a BSSO and DO gave both similar stable results in advancements of the mandible up to 10mm.

TMJ response to mandibular advancement surgery: an overview of risk factors

Objective

In order to understand the conflicting information on temporomandibular joint (TMJ) pathophysiologic responses after mandibular advancement surgery, an overview of the literature was proposed with a focus on certain risk factors.

Methods

A literature search was carried out in the Cochrane, PubMed, Scopus and Web of Science databases in the period from January 1980 through March 2013. Various combinations of keywords related to TMJ changes [disc displacement, arthralgia, condylar resorption (CR)] and aspects of surgical intervention (fixation technique, amount of advancement) were used. A hand search of these papers was also carried out to identify additional articles.

Results

A total of 148 articles were considered for this overview and, although methodological troubles were common, this review identified relevant findings which the practitioner can take into consideration during treatment planning: 1- Surgery was unable to influence TMJ with preexisting displaced disc and crepitus; 2- Clicking and arthralgia were not predictable after surgery, although there was greater likelihood of improvement rather than deterioration; 3- The amount of mandibular advancement and counterclockwise rotation, and the rigidity of the fixation technique seemed to influence TMJ position and health; 4- The risk of CR increased, especially in identified high-risk cases.

Conclusions

Young adult females with mandibular retrognathism and increased mandibular plane angle are susceptible to painful TMJ, and are subject to less improvement after surgery and prone to CR. Furthermore, thorough evidenced-based studies are required to understand the response of the TMJ after mandibular advancement surgery.

Skeletal stability after bilateral sagittal split advancement and setback osteotomy of the mandible with miniplate fixation

The purpose of this study was to evaluate intraorally placed mini plates and monocortical screws in terms of postoperative skeletal stability after bilateral sagittal split advancement and setback osteotomy of the mandible. Ten patients were included in this study with five requiring advancement (group I) and five requiring setback of the mandible (group II). Bell and Epker modified surgical technique was followed for all the patients. All the patients underwent pre- and postsurgical orthodontics. Cephalometric radiographs were taken preoperatively, immediate, 3, 6, and 12 months postoperatively. Cephalometric tracings were performed by one individual examiner using a modified burstone analysis. Statistical analysis was performed using the student paired t-test. In advancement patients, SNB (sella, Nasion, B point) angle showed relapse at 12th month postoperative period which was statistically significant (2.4 degrees). No changes were observed in anterior facial height, posterior facial height, Frankfort-mandibular incisor angle (FmiA), and overjet during the follow-up period. In setback patients, posterior facial height (p < 0.05), angles between the lower incisors and mandibular plane and pogonion had a statistically significant change position of 1.4 mm (paired t-test, p = 0.03). The SNB angle, anterior facial height, interincisal angle, and FmiA remained constant (0.8-1.2 degrees) during the follow-up period. In advancement cases, the relapse was seen from the third month postoperative period but in setback cases, the relapse was noted from the sixth month onward and the skeletal relapse in these cases were noticed cephalometrically.

Magnetic resonance imaging-verified temporomandibular joint disk displacement in relation to sagittal and vertical jaw deformities

This retrospective study was designed to analyze the relationships between temporomandibular joint (TMJ) disk displacement and skeletal deformities in orthodontic patients. Subjects consisted of 460 adult patients. Before treatment, lateral cephalograms and TMJ magnetic resonance imaging (MRI) were recorded. Subjects were divided into six groups based on TMJ MRI according to increasing severity of TMJ disk displacement, in the following order: bilateral normal TMJs, unilateral disk displacement with reduction (DDR) and contralateral normal, bilateral DDR, unilateral disk displacement without reduction (DDNR) and contralateral normal, unilateral DDR and contralateral DDNR, and bilateral DDNR. Subjects were subdivided sagittally into skeletal Class I, II, and III deformities based on the ANB (point A, nasion, point B) angle and subdivided vertically into hypodivergent, normodivergent, and hyperdivergent deformities based on the facial height ratio. Linear trends between severity of TMJ disk displacement and sagittal or vertical deformities were analyzed by Cochran-Mantel-Haenszel test. The severity of TMJ disk displacement increased as the sagittal skeletal classification changed from skeletal Class III to skeletal Class II and the vertical skeletal classification changed from hypodivergent to hyperdivergent. There were no significant differences in the linear trend of TMJ disk displacement severity between the sexes according to the skeletal deformities. This study suggests that subjects with skeletal Class II and/or hyperdivergent deformities have a high possibility of severe TMJ disk displacement, regardless of sex.

Closure of anterior open bites with mandibular surgery: advantages and disadvantages of this approach

INTRODUCTION

While closure of an anterior open bite with a mandibular procedure may predispose a surgical case to instability, there are instances where this type of treatment planning is indicated.

METHODS AND MATERIALS

In this paper, the authors review the advantages and disadvantages of this approach and present three cases with varying degrees of success. Additionally, treatment strategies are presented for managing large advancements of the maxilla and mandible.

RESULTS AND SUMMARY

Counterclockwise rotation of the mandible is a valuable tool that can be used in the treatment of patients with dentofacial deformities.

Hybrid fixation in the bilateral sagittal split osteotomy for lower jaw advancement

Miniplate and screw fixation has been widely used in bilateral sagittal split osteotomy, but some issues remain unclear concerning its lack of rigidity when compared to Spiessl's bicortical technique. This paper demonstrates the hybrid fixation technique in a case report. A 34-year-old female patient underwent a double jaw surgery with counter-clockwise rotation of the mandible fixed using the hybrid fixation technique. The patient evolved well in the postoperative period and is still under follow up after 14 months, reporting satisfaction with the results and no significant deviation from the treatment plan up to now. No damage to tooth roots was done, maxillomandibular range of motion was within normality and regression of the inferior alveolar nerve paresthesia was observed bilaterally. The hybrid mandibular fixation is clearly visible in the panoramic and cephalometric control radiographs. It seems that the hybrid fixation can sum the advantages of both monocortical and bicortical techniques in lower jaw advancement, increasing fixation stability without significant damage to the mandibular articulation and the inferior alveolar nerve. A statistical investigation seems necessary to prove its efficacy.

Biomechanical evaluation of a T-shaped miniplate fixation of a modified sagittal split ramus osteotomy with buccal step, a new technique for mandibular orthognathic surgery

OBJECTIVE

The purpose of this study was to biomechanically evaluate the stability of a T-shaped miniplate fixation of a modified sagittal split ramus osteotomy (MSSRO) with buccal step and to compare it with single or double-parallel straight miniplates fixing a standard sagittal split ramus osteotomy (SSRO).

STUDY DESIGN

Eighteen Synbone mandibular replicas were used in the study and divided into 3 groups. Standard SSRO was applied in the first and second groups, and the third group was cut for MSSRO with buccal step. After 7 mm of advancement, fixation modalities for the 3 groups included a single straight miniplate, double-parallel straight miniplates, and a T-shape miniplate, respectively. Each model was secured in a jig and subjected to vertical load on the anterior teeth.

RESULTS

The T miniplate group showed a significantly higher value for stability than the group with a single straight miniplate. There was no significant difference in stability between the T miniplate and the double-parallel straight miniplate groups.

CONCLUSION

For mandibular advancement surgery of 7 mm in a laboratory environment, a T-shaped miniplate used with MSSRO and buccal step as a combination significantly optimize the resistance and stability of the fixation compared with a standard SSRO fixed with a single straight miniplate.

Alteration of the mandibular plane during sagittal split advancement: Short- and long-term stability

OBJECTIVES

We investigated predictors of long- and short-term stability of surgical mandibular advancements with bilateral sagittal split osteotomy (BSSO).

STUDY DESIGN

Class II patients (n = 127) received mandibular advancement through BSSO with either rigid internal fixation or wire osteosynthesis. We used multiple linear regression analysis to assess the association of predictor variables with post-treatment horizontal and vertical B-point movement through 2 years.

RESULTS

Counterclockwise rotation of the mandibular plane angulation (MPA) was associated with greater horizontal and vertical relapse at all time periods except 8 weeks. Wire osteosynthesis, larger advancements, younger age, and genioplasty were significantly associated with relapse.

CONCLUSIONS

Surgically closing the MPA is associated with late horizontal and vertical relapse, whereas fixation type is related to early B-point movement. Large advancements with forward and upward repositioning of the mandible, genioplasty, and young age also play a role in relapse after BSSO.

The effects of guided tissue regeneration (GTR) on modified Le Fort I osteotomy healing in rabbits

Osteogenesis following surgery depends on the osteoblasts at the wound site. Fibrous nonunions may be the result of differential and rapid migration of fibroblasts compared to osteoblasts into the wound. The present study was designed to test this hypothesis through the use of guided tissue regeneration (GTR) in a rabbit model. Bilateral, Le Fort I osteotomies (n=20) were produced in the maxillae of 10 New Zealand White rabbits. The segments were advanced 6mm and rigidly fixed using microplates and screws. One side was covered with a resorbable collagen membrane or left uncovered. Rabbits were followed for four weeks with radiographs and the maxillae were harvested for histology. Cephalometry revealed that membrane-covered defects had significantly (P<0.01) reduced defect area (by approximately 70%) compared to uncovered defects. Histologically, membrane-covered defects showed more organized osteogenesis and less fibrous tissue than uncovered defects. Histomorphometry revealed that membrane covered defects had significantly (P<0.05) reduced defect areas (by approximately 20%) compared to uncovered defects. While findings suggest that GTR can facilitate osseous wound healing in Le Fort I osteotomies, results also caution against relying exclusively on two-dimensional radiography to assess bony wound healing in lieu of three-dimensional imaging and evaluations.

Stabilisation of sagittal split set-back osteotomies with miniplates: a prospective, multicentre study with 2-year follow-up

The aim of this study was to assess post-operative stability of bilateral sagittal split set-back osteotomies using two miniplates and clinical parameters including nerve function, TMJ function, occlusal relapse and patient satisfaction. The stability was measured on cephalometric radiographs and possible condylar alterations on orthopantomograms. This prospective study implied a 2-year follow-up on a group of 24 patients. The same protocol was used at six participating institutions at which the patients were treated. A stable occlusion without appreciable relapse was seen in 91% after 2-year follow-up. Only two patients in this study had mild occlusal relapse. The mean skeletal horizontal relapse at pogonion of the whole group, after 2 years was 1.1mm and appeared to be directed backwards. At occlusal level, however, the mean relapse was 1.2mm forwards. The function of the inferior alveolar nerve 2 years post-operatively was reported to be normal in approximately 70% of the patients, yet 80% had no complaints about nerve dysaesthesia. In approximately 21% of the patients, signs and symptoms of TMJ dysfunction had disappeared. Another group (10%), however, without pre-operative signs and symptoms of TMJ dysfunction developed these signs or symptoms post-operatively. No condylar remodelling or resorption was seen in this group of patients. The sagittal split set-back osteotomy fixed with miniplates appeared to be a relatively save and reliable procedure giving rise to adequate results and a high degree of patients satisfaction.