Skeletal Stability and Complications of Bilateral Sagittal Split Osteotomies and Mandibular Distraction Osteogenesis: An Evidence-Based Review

Long-term follow-up of corrective jaw surgery including distraction osteogenesis in 32 patients with juvenile idiopathic arthritis

Dentofacial deformity following juvenile idiopathic arthritis (JIA) with temporomandibular joint (TMJ) involvement is associated with functional, aesthetic, and psychosocial impairment. Corrective surgical treatment includes combinations of orthognathic surgeries (OS). The aims of this study were to assess orofacial symptoms, functional and aesthetic status, and stability after OS including mandibular distraction osteogenesis (MDO). A prospective study was conducted of 32 patients with JIA of the TMJ and dentofacial deformities who underwent MDO as the only surgery or in combination with bilateral sagittal split osteotomy, Le Fort I, and/or genioplastybetween 2003 and 2018. Data from clinical examinations and cephalograms performed pre- and postoperative and at long-term (mean 4 years) were analysed. Patients experienced unchanged orofacial symptoms (all P > 0.05), short-term TMJ functional impairment (all P < 0.001), and long-term morphological improvements in SNB angle (P < 0.001), anterior facial height (P < 0.001), mandibular length (P = 0.049), overjet (P < 0.001 and P = 0.005), and posterior facial symmetry (P = 0.046). MDO as the only surgery or with secondary adjunctive OS improved dentofacial morphology in terms of mandibular advancement, anterior facial height, posterior facial symmetry, and incisal relationships without long-term deterioration in TMJ function or orofacial symptoms.

Evaluation of bone contact area and intercondylar distance changes in orthognathic surgery - a comparison between BSSO and HSSO technique depending on mandibular displacement extent

OBJECTIVES

The present study aims to assess the impact of bilateral and high oblique sagittal split osteotomy (BSSO/HSSO), as well as displacement distances and directions on the expected and achievable bone contact area (BCA) and changes in the intercondylar distance (ICD). The primary question addressed is whether mandibular splitting through BSSO results in a greater BCA and/or ICD when compared to splitting through HSSO.

MATERIALS AND METHODS

Totally 80 mandibular displacements were performed on 20 fresh cadavers, for each subject, four splints were produces to facilitate mandibular advancement as well as setbacks of 4 and 8 mm. Pre- and postoperative CBCT scans were performed to plan the surgical procedures and to analyze the expected and achieved BCA and ICD.

RESULTS

Regarding the maximum mandibular displacement, the expected BCA for HSSO/BSSO were 352.58 ± 96.55mm2 and 1164.00 ± 295.50mm2, respectively, after advancement and 349.11 ± 98.42mm2 and 1344.70 ± 287.23mm2, respectively, after setback. The achieved BCA for HSSO/BSSO were 229.37 ± 75.90mm2 and 391.38 ± 189.01mm2, respectively, after advancement and 278.03 ± 97.65mm2 and 413.52 ± 169.52 mm2, respectively after setback. The expected ICD for HSSO/BSSO were 4.51 ± 0.73 mm and 3.25 ± 1.17 mm after advancement and - 5.76 ± 1.07 mm and - 4.28 ± 1.58 mm after setback. The achieved ICD for HSSO/BSSO were 2.07 ± 2.9 mm and 1.7 ± 0.60 mm after advancement and - 2.57 ± 2.78 mm and - 1.28 ± 0.84 mm after setback. Significant differences between the BCA after HSSO and BSSO were at each displacement (p < 0.001), except for the achieved BCA after 8-mm setback and advancement (p ≥ 0.266). No significant differences were observed regarding ICD, except for the expected ICD after 8-mm setback and advancement (p ≤ 0.037).

CONCLUSIONS

Compared to the virtual planning, the predictability regarding BCA and ICD was limited. ICD showed smaller clinical changes, BCA decreased significantly in the BSSO group.

CLINICAL RELEVANCE

BCA and ICD might have been less important in choosing the suitable split technique. in orthognathic surgery.

Skeletal stability of inter-molar mandibular distraction osteogenesis in growing patients

INTRODUCTION

The aim of this retrospective study was to firstly assess the stability of surgical advancement using inter-molar mandibular distraction osteogenesis (IMDO) and secondly to assess the impact of the surgical intervention on subsequent mandibular growth in patients with residual growth.

METHODS

The sample consisted of 17 (13F and 4M) consecutively treated patients who underwent IMDO and orthodontic treatment. Cephalometric analysis was performed at three time points: T0 prior to distraction; T1 post-distraction immediately prior to surgical removal of the distractors; and T2 following completion of orthodontic treatment when the final lateral cephalogram was taken (0.86-4.37 years after T1). Statistical comparison of lower facial height, mandibular length, growth, condylar position and anterior mandibular rotation was performed.

RESULTS

No association was found between changes in any of the cephalometric measurements and the length of the follow-up interval. The anterior mandibular segment underwent clockwise rotation during distraction and recovered to near its pre-distraction angulation during remodelling. An increase in the lower facial height of 1.88 ± 2.81mm also occurred during distraction (T0-T1) and was maintained during the follow-up period (T1-T2). Post-distraction (T1-T2) growth of lower facial height (p value 0.872) and mandibular length (p value 0.251) showed no association when compared to an untreated control group and an overall reduction in growth was reported.

CONCLUSIONS

IMDO was highly stable within a follow-up period of 2.3 ± 0.9 years; however, growth appears to have been inhibited.

Application of bilateral condylectomy as an alternative surgical treatment for Class III malocclusion with posterior vertical excess, a technical note

The Posterior vertical excess (PVE) associates a symmetric ramus and condyle elongation to an Angle Class III malocclusion. This dento-skeletal discrepancy can be isolated or associated to a condyle hyperplasia or a transverse overgrowth of the mandible due to macroglossia. We present the technique and the postoperative results of bilateral condylectomy applied for the surgical correction of PVE. Bilateral condylectomy represents an alternative to the bimaxillary surgery and adds to the therapeutic arsenal for the correction of Angle Class III malocclusion.

Radiological evaluation of inferior alveolar nerve displacement after removal of impacted mandibular third molars prior to sagittal split osteotomy

INTRODUCTION

We hypothesize that the removal of mandibular third molars (M3) 6 months prior to a bilateral sagittal split osteotomy (BSSO) could allow the displacement of the inferior alveolar nerve (IAN) in a favorable lingual position. This study aimed to radiographically compare the position of IAN before and after M3 removal in patients with Class II malocclusion.

MATERIALS AND METHOD

The CBCT images of 30 randomly selected patients (mean age 15.5 years, 19 females and 11 males) were segmented regarding the mandibular bone and the IAN canal. Mandibles were then superimposed and compared using 3D slicer (www.slicer.org). An orthonormal system was constructed, and the coordinates of IAN were assessed in the x- (horizontal axis), y- (depth axis), and z- (vertical axis) directions.

RESULTS

The mean changes in x- and z-values were 0.37 %, -0.09 % for the right IAN, 0.07 %, and -0.10 % for the left IAN, respectively. Y-axis was the dimension the most impacted by the M3 removal with a mean variation of -11.96 % for the right IAN, and 0.45 % for the left nerve (p1=0.74 and p2=0.04, respectively). Three patients presented a change in the IAN position superior to 1 mm on at least one coordinate axis. We observed a more important change in x-values of the right IAN in male than in female (p = 0.04), and no significant modifications regarding the other dimensions. Finally, there was no correlation between the age of the patients and the changes in IAN position.

CONCLUSION

This study confirms the absence of influence of mandibular third molar removal on the inferior alveolar nerve route prior to BSSO.

Global network mapping research findings on orthognathic surgery and temporomandibular disorder

OBJECTIVES

The objective of this work is to assess the relationship between orthognathic surgery and temporomandibular disorders literature through a bibliometric analysis.

METHODS

A bibliographic search in line with the STROBE guidelines and the concepts of the Leiden Manifesto was performed on the Web of Science using the terms orthognathic surgery AND temporomandibular. A citation analysis and establishment of the more cited articles were performed. A graphical representation of the keywords was created with VOSviewer.

RESULTS

A total of 810 articles were analyzed in this study. The research revealed a significant increase in publications on this topic, particularly in English language articles and a high H-index. The publications represented 55 nations, with the highest number of articles coming from the USA. The discussion of highly cited articles covered various aspects such as the relationship between orthognathic surgery and TMD, including condylar resorption or displacement, predisposing factors, dentoskeletal and occlusion patterns, anatomical factors, osteotomy techniques, condylar positioning techniques, and emerging technologies for improved TMJ stability.

CONCLUSION

The analysis reveals an increasing research interest in this field, with a significant number of publications in English and a high citation rate per article, indicating the impact of the research. Various factors associated with TMD in orthognathic surgery are explored, including condylar alterations, predisposing factors, occlusion patterns, and surgical techniques. The study underscores the importance of thorough assessment, treatment, and monitoring of TMD in orthognathic surgery patients, while acknowledging the need for further research and consensus in management strategies.

Prospective Evaluation of Children with Robin Sequence following Tübingen Palatal Plate Therapy

BACKGROUND

To assess the long-term functional orthodontic outcome of the Tübingen palatal plate (TPP) in children with Robin sequence (RS) in comparison to age- and sex-matched healthy controls.

METHODS

Between 09/2019 and 10/2020, we performed orthodontic assessments in 41 children at our Department of Orthodontics. Included were patients with RS (17 non-syndromic; four syndromic) and healthy controls (n = 22, average age in both groups 9.9 y). Facial analyses of 2D images, digital study casts and cephalometric measurements were made.

RESULTS

The orthodontic examinations showed no statistically significant group differences regarding functional extraoral, intraoral and pharyngeal parameters, or in skeletal patterns. The relationship between the upper and lower incisors was significantly increased (overjet 4 (2-10) vs. 3 (0-9) mm; p = 0.01) with a significant deficit in the lower face proportions (Jaw Index 4.15 (1.9-9.6) vs. 2.98 (0-9); p = 0.02; Facial convexity angle 157 (149-173) vs. 159 (149-170); p = 0.01).

CONCLUSION

Children with RS treated with the TPP showed normal long-term functional orthodontic outcomes, thanks to the functional adaption of the stomatognathic system. However, soft tissue growth did not completely match skeletal growth, resulting in a more convex facial profile.

Evaluation of effect of single vector mandibular distraction for correction of postankylotic mandibular hypoplasia requiring multiplanar correction: A prospective case series

Introduction

Uniplanar devices have been criticized for being insufficient to correct complex mandibular deformities and associated problems of open bite and cross bite. The use of oblique vector to correct complex multiplanar deformities using uniplanar mandibular distraction devices is the uniqueness of the present case series.

Aim and Objective

The aim of the present case series is to describe the successful use of uniplanar mandibular distraction devices for the correction of complex multiplanar deformities.

Material and Method

The technique of callous molding was employed to overcome any open bite. A total of 40 mandibular distractors in 20 patients (mean age 13 ± 2.67 years) were placed on the mandible for correction of the facial deformity associated with the lower jaw(mandible) in vertical, horizontal and/or sagittal plane, secondary to temporomandibular joint ankylosis. The distraction was done before and after the gap arthroplasty in 15 and 5 patients, respectively. A latency period of 3-5 days was applied, and distraction was performed at a rate of 1 mm/day with the rhythm of 0.5 mm twice daily.

Results

The significant lengthening was observed in both mandibular height (Ar Go) (50.40 ± 1.52 mm from 38.80 ± 4.38mm, P = 0.006) as well as in mandibular corpus length (Go Pg) (79.40 ± 2.28 from 58.80 ± 4.09, P = 0.001). Statistically significant changes in mandibular dimensions, facial proportions, and soft tissue profile were seen, which was assessed with the help of COGS analysis done on lateral cephalogram taken preoperatively and postoperatively.

Conclusion

With intelligent vector planning and callus molding multiplanar complex deformities can be corrected by using semiburieduniplanar devices.

Influence of Inferior Alveolar Nerve Exposure During Sagittal Split Osteotomy on the Rate and Timing of Baseline Sensory Recovery

PURPOSE

Neurosensory disturbance is the most common consequence of sagittal split osteotomy (SSO). The purpose of this study is to quantitatively assess neurosensory deficiency and recovery to the preoperative status when the inferior alveolar nerve (IAN) was exposed versus unexposed during SSO.

METHODS

This is a single-center, prospective, cohort study of all patients undergoing bilateral SSO between August 2018 and July 2019. Patients were included in the study sample if they underwent bilateral SSO with an intact intraoperative IAN and were received follow-up assessment for at least a year. The predictor variable was the intraoperative IAN status (exposed vs unexposed). The outcomes of interest were the rate and timing of recovery to the preoperative status. The covariates were age, sex, and the magnitude and direction of surgical movements. Neurosensory function was quantitatively evaluated using the Semmes-Weinstein monofilament test at follow-up intervals of 1, 3, 6, and 12 months. Descriptive statistics, bivariate statistics, Cox proportional hazards regression, and Kaplan-Meier analyses were performed. P value <.05 was considered statistically significant.

RESULTS

Of 90 patients, 86 patients who underwent 172 SSOs were included in this study. The mean age was 22.95 ± 3.34 years (range, 17 to 30), 65 were women, and the range of surgical movements was 3 to 8.3 mm of advancement and 2 to 12 mm of setback. Eighty-five nerves (49.4%) were allocated to the unexposed group, and 87 (50.6%) to the exposed group, with statistically significant differences in the rate and timing of recovery (hazard ratio = 2.368; 95% confidence interval, 1.662 to 3.376; P < .001). Among those with recovered nerves, the median time to recovery was 90 days in the unexposed group and 364 days in the exposed group (P < .0001).

CONCLUSIONS

IAN exposure during SSO is associated with an increased risk of neurosensory deficiency and an increased time of sensory recovery to the baseline threshold in patients aged 17 to 30 years. When the IAN remained fully enclosed in the canal of the distal segment, only 11% of patients had a measurable sensory deficit 1 year after surgery. In those patients with any degree of IAN exposure, 36% had a residual sensory deficit 1 year after surgery.

Is Orthognathic Correction with TMJ Preservation A Stable Treatment Option for Patients with Juvenile Idiopathic Arthritis?

Purpose

The purpose of this study was to evaluate the long-term skeletal stability of orthognathic correction of dentofacial deformities secondary to juvenile idiopathic arthritis (JIA) in individuals without total alloplastic joint reconstruction.

Materials and Methods

The investigators designed and implemented a retrospective case series of patients diagnosed with JIA who underwent bimaxillary orthognathic surgery. To evaluate the long-term skeletal changes, the maxillary palatal plane to mandibular plane angle, anterior facial height, and posterior facial height measurements were evaluated through cephalograms.

Results

Six patients met inclusion criteria. All subjects were female (mean 16.2 years). Four patients demonstrated < 1° of change of the palatal plane to mandibular plane angle, and all patients had < 2° of change. Three patients had < 1% change in the anterior to posterior facial height ratio. Three patients demonstrated relative posterior facial shortening compared to anterior facial height (< 4%). No patients developed postoperative anterior open-bite malocclusion.

Conclusion

Orthognathic correction of the JIA DFD deformity with TMJ preservation is a viable modality to improve facial esthetics, occlusion, upper airway and speech swallowing and chewing mechanisms in select patients. The measured skeletal relapse did not affect the clinical outcome.

Paediatric mandibular distraction: optimizing outcomes

PURPOSE OF REVIEW

The purpose of this review is to summarize current evidence surrounding the use of mandibular distraction osteogenesis in children and to highlight recent advances in our knowledge of this subject.

RECENT FINDINGS

Distraction osteogenesis of the mandible has gained in popularity since its initial description about 30 years ago. Its efficacy and safety have been well described. More recently, proper patient selection, technique modifications and long-term outcomes have been the subject of much discussion around this revolutionary technique.

SUMMARY

Distraction osteogenesis of the mandible is a powerful tool for surgeons. Technological advances and high-quality research have allowed for optimization of this technique within the field of craniomaxillofacial surgery.

Pierre Robin and breathing: What to do and when?

Robin sequence is characterized by mandibular retrognathia, airway obstruction, and glossoptosis; 80%-90% also have a cleft palate. Various treatment approaches exist, and although controlled studies are rare, objective assessment of treatment outcomes that address the leading clinical issues, namely obstructive sleep apnea and failure to thrive, are essential. Sleep-disordered breathing may be detected using cardiorespiratory polygraphy or polysomnography. Pulse oximetry alone may miss infants with frequent obstructive apneas, yet no intermittent hypoxia. Among conservative treatment options, the Tubingen Palatal Plate with a velar extension shifting the tongue base forward is the only approach that corrects the underlying anatomy and that has undergone appropriate evaluation. Of the surgical treatment options, which are not necessarily the first line of therapy, mandibular distraction osteogenesis (MDO) is effective and has been most extensively adopted. Notwithstanding, it is puzzling that MDO is frequently used in some countries, yet hardly ever in others, despite similar tracheostomy rates. Thus, prospective multicenter studies with side-by-side comparisons aimed at identifying an optimal treatment paradigm for this potentially life-threatening condition are urgently needed.

Comparison of two surgical techniques (HOO vs. BSSO) for mandibular osteotomies in orthognathic surgery-a 10-year retrospective study

PURPOSE

To retrospectively compare the high-angled sagittal split osteotomy (HOO) and the bilateral sagittal split osteotomy (BSSO) for the correction of skeletal dysgnathias regarding intra- and postoperative complications.

METHODS

The electronic medical records of all patients treated with an orthognathic surgery at the Department for Oral, Maxillofacial and Facial Plastic Surgery, University Hospital Frankfurt, Germany, between the years 2009 and 2019 were retrospectively reviewed.

RESULTS

Two hundred ninety-one patients were included. The overall complication rates were 19.78% (BSSO) compared to 12.5% (HOO) (p = 0.14). Significant differences were found regarding the operation time (HOO < BSSO, p = 0.02), material failure (HOO > BSSO, p = 0.04), and early recurrence requiring revision surgery (HOO < BSSO, p = 0.002). The use of a ramus plate significantly reduced the risk of plate failure (2.8% < 13.6%, p = 0.05). More bad splits (p = 0.08) and early sensory disorders (p = 0.07) occurred in the BSSO group.

CONCLUSION

The HOO presents a possible alternative to the BSSO since newly developed osteosynthesis material significantly reduces the risk of material failure. The BSSO is accompanied by higher risks of developing complications like a bad split and sensory disorders but, however, remains the standard for large anterior-posterior transpositions of the mandible.

Physiotherapeutic Reduction of Orofacial Pain Using Extremely Low-Frequency Electromagnetic Field and Light-Emitting Diode Therapy—A Pilot Study

Introduction. Pain is a natural response of the body to injury and one of the symptoms defining an inflammatory reaction. It is almost always present after orthognathic surgeries (OGS), but its severity is subjective in each patient. Postoperative care of the patient is aimed at minimizing of postoperative pain relief orofacial region. Options of physiotherapy include extremely low-frequency electromagnetic field (ELF EMF) and high-energy light-emitting diode (LED). Aim of the Study. The aim of this study was to evaluate the effects of physiotherapy combining ELF EMF and LED to reduce pain of the orofacial region in patients after OGS. Material and Methods. The study was conducted in thirty-two patients who underwent OGS to treat morphological defects. The participants were randomly divided into two groups: Physiotherapy group (PT) and Control group (CG). In both groups, patients were prescribed Paracetamol and nonsteroidal analgesics (NSAID—ibuprofen). Patients from the PT group additionally received postoperative physiotherapy immediately after leaving the surgical clinic in the form of ELF EMF and LED therapy. Physiotherapeutic treatments were performed for 10 days, three applications a day, at no cost to the patient. Pain intensity was assessed using the visual analogue scale (VAS), which is a reliable instrument for the measurement of pain intensity self-reported by the patient. Results. Faster reduction of pain was the major observation made in patients who received physiotherapy treatments. In all subjects, after 5 days of therapy, the pain intensity was reduced by about 50% or resolved completely. Effects of therapy were measured with the relative changes in the pain intensity score, showing what fraction of the initial pain was eliminated at the first stage and throughout the whole therapy. The analysis of relative changes instead of absolute changes allowed us, among other things, to eliminate the bias of the higher initial pain intensity in the CG group compared to the PT group. Conclusions. The conducted research revealed that the combined use of ELF EMF and LED is beneficial in the reduction of pain of patients after OGS. The analgesic effects of physiotherapy in the treatment after OGS are necessary to continue research in this area and analyze the possibility of extending the indications for its use in other surgically treated maxillofacial diseases.

[Condylar displacement following orthognathic surgery]

The overview of the current literature in the research of mandibular condyle displacement after orthognathic surgeries was done. The correct postoperative mandibular condyle position is considered as one of the determinants of the stability of treatment results.

Treatment of severe mandibular deficiency following TMJ ankyloses by distraction osteogenesis and orthodontic treatment with microimplants

Severe mandibular deficiency caused by temporomandibular joint (TMJ) ankyloses produces functional and aesthetic problems that require complicated long-term treatment. In this case report, we describe the benefits of using microimplant mechanics for controlling the direction of distraction during distraction osteogenesis and for performing the movement of teeth. We also present its remarkable results and long-term stability. A 20-year-old girl presented with a convex profile due to severe mandibular retrognathia after a history of several TMJ surgeries for bilateral TMJ ankyloses. Mandibular distraction osteogenesis (MDO) was performed, and elastics were placed between the microimplants to control the direction of distraction. Subsequently, after retraction of the maxillary anterior teeth and distalisation of the whole mandibular dentition, the facial profile was markedly improved, and good interdigitation was obtained. The six-year follow-up retention and overall stability were satisfactory with good interdigitation and jaw function.

The effect of low intensity pulsed ultrasound on mandibular condylar growth in young adult rats

There is a need for more effective methods to enhance mandibular growth in young adults with mandibular deficiency. Previous studies suggest that low intensity pulsed ultrasound (LIPUS) can enhance mandibular growth in growing individuals. This study aimed to evaluate the potential growth changes of the mandible following 4-week LIPUS application in young adult rats. Nineteen ≈120-day-old female rats were allocated to experimental (n = 10) and control (n = 9) groups. The animals in the experimental group were treated with LIPUS to their temporomandibular joints (TMJs) bilaterally, 20 min each day for 28 consecutive days. Animals were then euthanized; gross morphological evaluation was performed on 2D photographs and 3D virtual models of hemi-mandibles, and microstructural assessment was done for the mandibular condyle (MC). Evaluation of mineralization and microarchitecture properties of subchondral cancellous bone was performed by micro-computed tomography (μCT) scanning. Qualitative and histomorphometric analysis was done on condylar cartilage and subchondral bone following Alcian Blue/PAS and Goldner's Trichrome staining. Vital flourochrome (calcein green) labeling was also utilized to determine the amount of endochondral bone growth. Gross morphological evaluations showed a slight statistically non-significant increase especially in the main condylar growth direction in the LIPUS group. Moreover, 3D evaluation depicted an enhanced periosteal bone apposition at the site of LIPUS application. Microstructural analysis revealed that LIPUS stimulates both chondrogenesis and osteogenesis and enhances endochondral bone formation in young adult rat MC. Furthermore, the effect of LIPUS on osteogenic cells of subchondral cancellous bone was notable. To conclude, LIPUS can enhance young adult rats' MC residual growth potential.

Orthognathic surgery for juvenile idiopathic arthritis of the temporomandibular joint: a critical reappraisal based on surgical experience

Juvenile idiopathic arthritis (JIA) involving the temporomandibular joint (TMJ) can result in significant dentofacial deformities that may require orthognathic surgical correction. The aim of this study was to assess the functional and aesthetic results relative to stability after bimaxillary surgery with counterclockwise rotation of the occlusal plane in patients with JIA. A retrospective chart review was conducted of all patients affected by JIA who underwent orthognathic surgery between January 2000 and December 2019 at the Face Surgery Centre (Parma, Italy). Patient records were evaluated for surgical indications, complications, and outcomes. The final study sample included 13 patients (12 female, one male). The mean age of the patients was 18.6 years (range 17-26 years) at the time of surgery; 12 patients had bilateral TMJ disease. At the 1-year follow-up, all patients except one had a stable occlusion with a natural, well-balanced morphology of the face and adequate dynamic excursion of the mandible. The 1-year postoperative cone beam computed tomography (CBCT) scan revealed complete ossification at all osteotomy sites. Bilateral sagittal split osteotomy with mandibular advancement is an effective procedure with a low rate of complications for patients with JIA with stable disease confirmed by preoperative CBCT or magnetic resonance imaging.

Radiographic healing patterns after tooth-borne distraction in canine model

Background

The osteogenesis distraction technique applied to the craniofacial skeleton is an alternative treatment for dentofacial deformities. Despite the advantages of tooth-borne distractors, few studies have evaluated their clinical implementation in sagittal dentoskeletal deformities. This study aimed provide a radiographic assessment of the effect of two different activations of tooth-borne distraction in the lengthening of the mandible in canines.

Material and Methods

Ten male beagle dogs, approximately one year old, were used for this experimental study. Three remained as a control group and seven underwent a mandibular tooth-borne distraction protocol with single daily activation in one hemimandible and two daily activations in the other, during ten days. The consolidation period took 12 weeks. Occlusal radiographs were performed immediately pre- and postoperatively.

Results

After the distraction period, the host bone margins presented very well-defined outlines with regular contours. Concerning the consolidation period, between the second and fourth weeks, all hemimandibles showed small rectangular radiopaque regions with parallel orientation to the distraction axis. At the twelfth week, all hemimandibles presented an entire mineralization of the distraction gap with no axial deviations of the anterior and posterior host bone, nine of which with both margins showing corticalization.

Conclusions

Radiographic analysis showed bone regeneration in order to achieve the original bone architecture, especially in the group of multiple distraction. Tooth-borne distraction allowed successful sagittal lengthening of the mandible in a canine model.

Key words:Orthodontics, osteogenesis, distraction, mandibular advancement, orthodontic appliance design.

Device Malfunction Associated With Mandibular Distraction for Infants With Robin Sequence

INTRODUCTION

Mandibular distraction osteogenesis (MDO) effectively treats upper airway obstruction (UAO) in young patients with Robin sequence (RS). The most commonly used MDO devices have internal and external components that require manual activation. Although complications associated with MDO in infants with RS have been well documented, hardware/device malfunction has not been precisely described. The present study reports the authors' recent experiences with such problems, in an effort to shed light on these complications and identify potential steps to mitigate future related issues.

DESIGN

The authors reviewed a prospectively gathered database to identify all young children under the age of 3 years who underwent MDO using buried internal devices for UAO associated with grade 3 RS from March 2007 to September 2019. We specifically focused on complications attributable to the hardware itself.

RESULTS

Nineteen patients with 40 devices met inclusion criteria. The median age at MDO was 2.3 months (interquartile range 1.4-6.3 months). Intraoperative activation of all devices under direct vision resulted in satisfactory distraction. Four devices (10.5%) developed postoperative complications directly related to the device, including break down of component parts (N = 3) and failure to maintain distraction distance (N = 1). Two patients required surgical replacement of one device each, whereas the remaining complications occurred during the consolidation phase and did not require intervention.

CONCLUSIONS

This report documents a series of device/hardware malfunction in infants and young children undergoing MDO for severe UAO associated with RS. Despite rigorous testing and development, these devices may fail, resulting in patient morbidity.

Long-term stability and condylar remodeling after mandibular advancement: A 5-year follow-up

INTRODUCTION

This study evaluated whether presurgical characteristics, the magnitude of mandibular advancement, and changes in mandibular plane angle are correlated with long-term stability and postsurgical condylar remodeling and adaptations using 3-dimensional imaging.

METHODS

Forty-two patients underwent bilateral sagittal split osteotomies for mandibular advancement using rigid fixation. Cone-beam computed tomography (CBCT) scans were acquired before surgery (T1), immediately after surgery (T2), and at long-term follow-up (T3). The average follow-up period was 5.3 ± 1.7 years after surgery. Anatomic landmark identification on the cone-beam computed tomographies and subsequent quantification of the changes from T1 to T2 and T2 to T3 were performed in ITK-SNAP (version 2.4; itksnap.org) and 3DSlicer (version 4.7; http://www.slicer.org) software. Surgical displacements, mandibular plane angle changes, and skeletal stability were measured relative to cranial base superimposition, whereas condylar remodeling was measured relative to regional condylar registration. Partial correlation coefficients were used to assess relationships between clinical and surgical variables, condylar remodeling, and long-term surgical relapse while controlling for variability in the length of follow-up.

RESULTS

B-point relapsed more than 2 mm posteriorly in 55% of the patients. The only variables strongly associated with the posterior movement of B-point long-term were mesial yaw of the condyle during surgery (P ≤0.01) and the length of follow-up from T2 to T3 (P ≤ 0.01). There was no relationship between the magnitude of advancement or presurgical mandibular plane angle and relapse or condylar resorption. Condylar resorption was strongly associated with relapse of B-point in the posterior direction (P ≤0.01) and clockwise rotation of the mandibular plane long-term (P ≤0.01). Twenty-nine percent of subjects showed resorption of more than 2 mm in the inferior direction at the lateral pole, and 17% of the subjects showed resorption of more than 2 mm in the inferior direction at condylion. Compared with male subjects, females exhibited significantly greater condylar remodeling (P ≤0.01) and slightly greater relapse at B-point (P ≤0.05).

CONCLUSIONS

Surgical relapse at B-point may occur slowly over time and is primarily due to condylar resorption in mandibular advancement patients. Mesial yaw of the condyle during surgery may lead to condylar resorption postsurgically. In addition, females are at greater risk of condylar resorption postsurgically.

Incidence of condylar resorption after bimaxillary, Lefort I, and mandibular surgery: an overview

The aim of the present overview was to evaluate the outcomes of systematic reviews to determine the incidence of condylar resorption in patients submitted to orthognathic surgery and analyze whether the risk of developing this condition is related to a specific type of surgery. Searches were conducted in the PubMed/MEDLINE, Embase, and Cochrane electronic databases for systematic reviews with quantitative data on condylar resorption due to any type of orthognathic surgery for dentoskeletal deformities published up to May 25, 2019. The AMSTAR 2 and Glenny tools were applied for the quality appraisal. Five systematic reviews were included for analysis. Only one article was considered to have high quality. Among a total of 5128 patients, 12.32% developed condylar resorption. From those patients, 70.1% had double jaw surgery, 23.4% had mandibular surgery alone, and in 6.5% a Lefort I technique was used. Based on these findings, bimaxillary surgery could be considered a risk factor for condylar resorption. However, these results should be interpreted with caution, since other factors, such as pre-operative skeletal deformities, type of movement, and type of fixation, can contribute to the development of this condition. Further studies should consider reporting main cephalometric data, temporomandibular diagnosis, hormonal levels, and tomographic measures before and after the surgery at least every 6 months during the firsts two years to identify accurately risk factors for condylar resorption.

The Effect of Orthognathic Surgery on Temporomandibular Joint Function and Symptoms: What are the Risk Factors? A Longitudinal Analysis of 375 Patients

PURPOSE

The effects of orthognathic surgery (OGS) on the temporomandibular joint (TMJ) are still controversial. Based on a high-volume uniform collective, the function and clinical symptoms of the TMJ and the dysfunction index (Di) by Helkimo were evaluated prior and up to 2 years after OGS.

METHODS

A longitudinal cohort study was performed between 2006 and 2016. A comprehensive examination focusing on TMJ function, temporomandibular disorder (TMD) symptoms, and the Di had been performed preopertaively (T0) and postoperatively at 6 weeks (T1), 6 months (T2), 1 year (T3), and 2 years (T4). The predictor variables used were sex, age, skeletal class, type of surgery, and amount of dysfunction or number of TMD complaints before treatment. The outcome of this study was TMD symptoms and the Di. Descriptive and bivariate statistics were computed, and the significance level was set at P < .05.

RESULTS

The sample consisted of 375 patients (247 women, 128 men, mean age 28.1 ± 9.4 years), 269 with skeletal Class II (71.7%) and 106 with skeletal Class III (28.3%) treated with sagittal split osteotomy bilateral sagittal split osteotomy (n = 173) or Le Fort I and bilateral sagittal split osteotomy (n = 202). Severe signs of dysfunction (Di 2/3) were seen in 5.9% of the patients before OGS and in 2.1% of the patients 2 years after OGS. The difference in Di (Di0/1 and Di2/3) between T0 and T1/T2 was statistically significant (P = .028; P = .011, respectively). TMD symptoms were significantly reduced 2 years after OGS (P = .028). Female gender (P = .013), skeletal Class II (P < .001), and counterclockwise rotation (P < .001) were the only risk factors significantly associated with the occurrence of TMD at T1.

CONCLUSIONS

The results of this study suggest that in most cases TMD symptoms can be significantly reduced and only a few can be induced with OGS. No risk factors were found for long-term effects on the TMJ.

Distraction Osteogenesis Versus Orthognathic Surgery: Demystifying Differences in Concepts, Techniques and Outcomes

Introduction

The popularity and interest evoked by orthognathic surgery and distraction osteogenesis are undisputed in the field of oral and maxillofacial surgery. However, questions regarding the individual identities of either of them with clarity in their concepts, techniques and outcomes have remained unanswered. The aim of this review is to shed light on these questions.

Methods

This review is structured as a narrative review of thirty years of literature available in the specialities of orthognathic surgery and distraction osteogenesis.

Conclusion

The authors present a review of existing literature combined with contrasting experience gained over the years in providing an overview of the merits and demerits of the two surgical techniques which will aid the clinician in justifying the use of one technique over the other.

Mandibular micrognathia and vertical maxillary excess correction with combination LeFort I and inverted L osteotomies

A 34-year-old woman with mandibular micrognathia, vertical maxillary excess, and an open bite characterized by a "bird-face" deformity was treated with orthodontics combined with LeFort I and bilateral inverted L osteotomies. The total treatment time was 16 months. Her occlusion and facial appearance were significantly improved by a surgical-orthodontic plan. This case report presents the discussion of a unique and complex orthognathic surgical case and the myriad of orthodontic and surgical considerations that it involved.

Do Patients With Different Mandibular Plane Angles Have Different Time to Relapse After Bilateral Sagittal Osteotomy With Mandibular Advancement?

PURPOSE

This study sought to answer the following question: Do patients with different mandibular plane angles (MPAs) have a different time to relapse after mandibular advancement with bilateral sagittal split osteotomy?

MATERIALS AND METHODS

We performed a retrospective cohort study of patients who underwent bilateral sagittal split osteotomy advancement at Massachusetts General Hospital between 2005 and 2017. The primary predictor variable was MPA, categorized as low (<25°), medium (between 25° and 35°), or high (>35°). The outcome variable was time to relapse (≥2-mm posterior change at the B point). Other covariates included gender, age, temporomandibular joint symptoms, bimaxillary surgery, direction of mandibular rotation, magnitude of advancement, genioplasty, and fixation method. Time to relapse was estimated using the Kaplan-Meier method. Cox and parametric regressions for interval-censored data were performed. P < .05 was considered statistically significant.

RESULTS

The sample was composed of 58 patients (40 female patients), with a mean age of 26.1 ± 4.9 years, grouped as follows: low MPA, n = 15; medium MPA, n = 26; and high MPA, n = 17. Clinically significant relapse was found in 18 patients (31%). Age, temporomandibular joint symptoms, counterclockwise rotation, and magnitude of advancement were statistically significantly different among the 3 groups. When we assessed time to relapse, the Kaplan-Meier method showed that high-MPA patients had a longer mean time at risk and higher estimated probabilities of relapse at different time points compared with low- and medium-MPA patients (P < .05). However, this association was not significant in Cox and parametric regressions.

CONCLUSIONS

Our results suggest that clinically significant relapse was found during the first postoperative year in low-MPA patients and from 2 to 5 years postoperatively in high-MPA patients. Multivariate regression analyses did not show a significant association between MPA and time to relapse, suggesting that other covariates may play a role in the observed time to relapse.

Condylar resorption in orthognathic patients after mandibular bilateral sagittal split osteotomy: a systematic review

Objective

To systematically search the literature and assess the available evidence regarding the incidence and quantification of condylar resorption following bilateral sagittal split osteotomy (BSSO) of the mandible in orthognathic patients.

Search methods

Electronic database searches of published and unpublished literature were performed. The reference lists of eligible studies were hand searched for additional studies.

Selection criteria

Randomized clinical trials (RCTs), prospective, and retrospective studies with patients of any age that underwent BSSO were included.

Data collection and analysis

Study selection, data extraction, and risk of bias assessment were performed individually and in duplicate.

Results

One RCT, 3 prospective, and 10 retrospective studies were included in this review. The lack of standardized protocols and the high amount of heterogeneity precluded a valid interpretation of the actual results through pooled estimates. There was a substantial consistency among studies, however, that young, female patients with mandibular deficiency and high mandibular plane angle, submitted to surgical counterclockwise rotation of mandibular segments, were more prone to a higher risk for condylar resorption after BSSO. The level of evidence was found to be low given the high/serious risk of bias in all included studies.

Conclusions

Condylar resorption should be taken into account as a potential postsurgical complication after BSSO. However, its incidence and quantification need precautious interpretation owing to the low level of evidence and the high heterogeneity of studies. Additional high-quality prospective research assisted by 3D imaging technology is needed to allow more definitive conclusions.

Registration

Study not registered.

Conflict of interest

None.

The Impact of the Use of Kinesio Taping Method on the Reduction of Swelling in Patients After Orthognathic Surgery: A Pilot Study

BACKGROUND Orthognathic surgery (OGS) is associated with extensive surgical intervention within the soft and hard tissues of the facial region of the skull leading to inflammatory reactions. The presence of postoperative swelling indicates the accumulation of exudate or transudate; both these fluids occur in surgery. Massive swelling is a significant problem, because the tension of tissues intensifies pain sensations. The aim of the study was to evaluate the effectiveness of the kinesio taping method (KT) in patients after orthognathic surgery in the area of the facial skull in terms of eliminating postoperative swelling. MATERIAL AND METHODS The study of the impact of kinesiology tape applied after orthognathic surgery to the craniofacial area on the elimination of swelling was performed in sixteen patients who suffered from this complication after bilateral sagittal split osteotomy. RESULTS The swelling was shown to be reduced after KT; within the same study the differences were statistically significant between the left and right sides and for the same side (p<0.05). The application of the lymphatic kinesio taping method led to the reduction of tension in the affected area and restoration of proper lymphatic circulation in the region covered by swelling. This allows for the improvement of the blood and lymph microcirculation and activation of self-healing processes. CONCLUSIONS The analysis of the impact of the practical use of the lymphatic KT on complications after orthognathic surgery revealed that it had a beneficial effect on the reduction of swelling. The use of the KT method seems promising because it is simple to carry out, not traumatic, economical and rarely causes undesirable allergies.

Micrognathia with temporomandibular joint ankylosis and obstructive sleep apnea treated with mandibular distraction osteogenesis using skeletal anchorage: a case report

Background

We describe the case of a 16-year-old female patient with micrognathia, temporomandibular joint (TMJ) ankylosis, and obstructive sleep apnea, who was treated with mandibular distraction osteogenesis (DO) combined with sliding genioplasty, using skeletal anchorage.

Case presentation

We first performed interpositional arthroplasty, in which an interposition of fascia temporalis and surrounding fat tissue was inserted into the defect after bilateral condylectomy, increasing the maximum mouth opening from 5.0 to 32.0 mm. Subsequently, orthodontic treatment and advancement of the mandible were carried out by mandibular DO, using miniscrews and miniplates. Finally, sliding genioplasty was performed to bring the tip of the mandible forward. The total amount of mandibular advancement at the menton was 16.0 mm. An improved facial appearance and good occlusion were eventually achieved, and the apnea-hypopnea index decreased from 37.1 to 8.7. There was no obvious bone resorption or pain in the temporomandibular region, limited mouth opening (maximum mouth opening: 33.0 mm), myofascial pain or headache, downward rotation of the mandible, or lateral shift of mandibular position evident at 5 years and 6 months after mandibular DO.

Conclusion

Mandibular DO using skeletal anchorage with intermaxillary elastics is useful for preventing extrusion of the upper and lower anterior teeth, thereby preventing rotation of the mandible. In addition, mandibular DO combined with sliding genioplasty is effective at improving both dentofacial deformities and impaired respiratory function.

Surgical Treatment of Dentofacial Deformities Caused by Juvenile Idiopathic Arthritis

The purpose of our retrospective study was to evaluate the results of orthognathic treatment, distraction osteogenesis, and/or prosthetic reconstruction of the temporomandibular joints in patients with juvenile idiopathic arthritis (JIA).Twelve patients with severely affected temporomandibular joints (TMJs) and reduced ramus height were treated with mandibular advancement with orthognathic surgery (11) and additional bilateral or unilateral mandibular ramus distraction (3) or additional bilateral or unilateral prosthetic reconstruction of the TMJ (3). One patient was treated surgically with bilateral TMJ prosthetic reconstruction only. The patients were followed up clinically and radiologically with emphasis on healing, TMJ function, stability of the occlusion, skeletal stability, and facial appearance for an average of 2.3 years after the final surgery. The mean mandibular advancement was 10.1 mm. The mean relapse at pogonion was 2.1 mm, which represents 20.8% of the surgical advancement. The occlusion was stable in 11/12 patients. The TMJ function was good and the facial esthetics improved in all patients. Orthognathic treatment and mandibular ramus distraction osteogenesis provide beneficial lengthening of the mandibular body in JIA patients with asymptomatic and stabile condyles. In adult patients with relapse of the disease or postoperative condylar relapse prosthetic total joint replacement is a reliable and safe alternative.

Laser Biophotomodulation in Patients with Neurosensory Disturbance of the Inferior Alveolar Nerve After Sagittal Split Ramus Osteotomy: A 2-Year Follow-Up Study

OBJECTIVE

To evaluate the effect of the application of photobiomodulation in a 2-year follow-up period in patients who have been intervened with a sagittal ramus split osteotomy and present neurosensory disturbance of the inferior alveolar nerve.

BACKGROUND

Photobiomodulation is a common clinical tool in dentistry, for its beneficial effects have been shown in surgical and periodontal wound healing, reducing of swelling and pain, neurosensory recovery, and treatment of temporomandibular joint disorders.

METHODS

This is a 2-year follow-up study with an experimental (Laser) group (n = 33) that received photobiomodulation, and a control (Sham) group (n = 9), placebo. All patients from the Laser group received laser applications (continuous wave of 0.353 W/cm², 27 J in 270 sec per session) on days 1, 2, 3, 5, 10, 14, 21, and 28 after surgery. Neurosensory disturbance was evaluated with five tests: Visual Analog Scale (VAS) for pain and sensitivity, sensitivity threshold test, two-point discrimination, and thermal discrimination. All tests were performed before (24 h before surgery) and after surgery (24 h, 28 days, 60 days, 6 months, 1 year, 2 years, more than 2 years). Participants and evaluator were blinded to intervention. Variables were described with absolute frequencies, percentages, and medians. Ordinal and dichotomous variables were compared with Mann-Whitney's and Fisher's tests, respectively.

RESULTS

Clinical improvement was observed during the follow-up period for the Laser group; general VAS for sensitivity was normal in 11 participants from the Laser group at 2 years postsurgery (40.74%), while no participants from the Sham group achieved this (p = 0.0341). Twenty-three participants recovered initial values for two-point discrimination (69.7%) after 2 years of follow-up (p = 0.0025) as well as sensitivity threshold test. General VAS for pain was normal in 31 patients from the Laser group after 2 years of follow-up (93.94%, p = 0.0254).

CONCLUSIONS

Photobiomodulation was effective for neurosensory recovery on sample studied.

Influence of Electroacupuncture and Laser-Acupuncture on Treating Paresthesia in Patients Submitted to Combined Orthognathic Surgery and Genioplasty

Objective: The goal of this research was to observe the influence of electroacupuncture (EA) and laser-acupuncture on the return of tactile/pain sensitivity in patients who underwent orthognathic surgery. Materials and Methods: Thirty volunteers subjected to orthognathic surgery were evaluated and randomly divided into 2 groups, in which 3 treatments were evaluated: control (n = 30) (G0, medication + placebo laser treatment) and 2 experimental treatments (n = 15) (G1, medication + EA) or G2 (medication + laser-acupuncture). The control group had n = 30 because for each experimental treatment conducted on a volunteer's hemi-face, there was a control treatment on the other hemi-face. In G1, medication was given with EA, with needles placed at predetermined points (ST 4 [Dicang], M-HN-18 [Jiachengjiang], CV 24 [Chengjiang], ST 5 [Daying], ST 6 [Jiache], and point A1 [YNSA]). For electrostimulation, the device used delivered transcutaneous electrical nerve stimulation of a burst type, with intensity and frequency variations of T = 220 ms and F = 4 Hz (30 minutes, 2 × /week). In G2, in addition to the medication, laser irradiation (at 780 nm) was applied on acupuncture points (at 0.04 cm², 70 mW, 6 s/point, 0.42 J/point, 10 J/cm², 2 × /week). All volunteers were evaluated before and during the 4 months following the surgery. Tactile sensitivity was assessed by mechanical brushing (brush #s 2 and 12) and by a 2-point discrimination test, using a bow compass. A pain test was performed with a pulp electrical test that stimulates intact nerves of the dentin-pulp complex. A Kaplan-Meier test was performed, and survival curves were plotted for comparison between groups. Cox regression analysis was also conducted (α = 0.05). Results: There were no statistically significant differences among the groups for the 2-point discrimination test (brushes #2 and #12) on the buccal mucosa region and for the pulp test on all evaluated regions. However, the tactile test using brush #12 revealed significant differences between G1 and the other groups when considering the lower lip (P = 0.024) and chin (P = 0.028) areas. Conclusions: Only EA was able to influence-using the brushing test (brush #12)-the return of tactile sensitivity on the chin and lower lip positively after combined orthognathic surgery and genioplasty.

Skeletal stability following mandibular advancement: is it influenced by the magnitude of advancement or changes of the mandibular plane angle?

Objectives

The aim of this study was to investigate the effects of advancement magnitude and changes in mandibular plane angle on the stability of mandibular advancement.

Materials and Methods

This retrospective cohort study evaluated the postoperative stability of mandibular advancement in class II skeletal subjects who underwent bilateral sagittal split osteotomy. Radiographs taken preoperatively, immediately postoperatively and 1 year postoperatively were traced and analyzed using linear and angular measurements. To determine horizontal and vertical relapse, an X-Y coordinate system was established in which the X-axis was constructed by rotating S-N downward by 7° (approximation of the Frankfort horizontal plane) and the Y-axis was defined as a line perpendicular to the X-axis and passing through the point Sella. For certain reference points including point A, point B, pogonion and menton, the perpendicular distance between each point and both axes was determined and cephalometric variables were recorded as X and Y coordinates.

Results

Twenty-five subjects were studied. A significant correlation between the amount of mandibular advancement and relapse in the B point (vertical and horizontal) and the pogonion point was observed (vertical and horizontal, P<0.001). Evaluation of data demonstrated a positive correlation between the mandibular plane angle (SN/ML) change and vertical relapse in the B point (P<0.05). A simple regression model demonstrated that 74% of horizontal relapse and 42.3% of vertical relapse in the B point was related to the amount of mandibular advancement. The receiver operating characteristic test showed that 8.5 mm mandibular advancement is related to a relapse rate of 1 mm or more in the pogonion, vertically or horizontally.

Conclusion

The magnitude of mandibular advancement is a stronger surgical predictor for horizontal rather than vertical relapse at the B point. Changes in mandibular plane angle (SN/ML) during surgery affect vertical, but not horizontal relapse at the B point.

Bilateral sagittal split mandibular osteotomies for enhanced exposure of the anterior cervical spine in children: technical note

The bilateral sagittal split mandibular osteotomy (BSSMO), a common maxillofacial technique for expanding the oropharynx during treatment of micrognathia, is a rarely employed but useful adjunct to improve surgical access to the ventral cervical spine in children. Specifically, it provides enhanced exposure of the craniocervical junction in the context of midface hypoplasia, and of the subaxial cervical spine in children with severe kyphosis. The authors describe their technique for BSSMO and evaluate long-term outcomes in patients. The pediatric neurosurgical database at a single center was queried to identify children who underwent BSSMO as an adjunct to cervical spine surgery over a 22-year study period (1993-2015). The authors retrospectively reviewed clinical and radiographic data in all patients. The authors identified 5 children (mean age 5.3 ± 3.1 years, range 2.1-10.0 years) who underwent BSSMO during cervical spine surgery. The mean clinical follow-up was 3.0 ± 1.9 years. In 4 children, BSSMO was used to increase the size of the oropharynx and facilitate transoral resection of the odontoid and anterior decompression of the craniocervical junction. In 1 patient with subaxial kyphosis and chin-on-chest deformity, BSSMO was used to elevate the chin, improve anterior exposure of the subaxial cervical spine, and facilitate cervical corpectomy. Careful attention to neurovascular structures, including the inferior alveolar nerve, lingual nerve, and mental branch of the inferior alveolar artery, as well as minimizing tongue manipulation and compression, are critical to complication avoidance. The BSSMO is a rarely used but extremely versatile technique that significantly enhances anterior exposure of the craniocervical junction and subaxial cervical spine in children in whom adequate visualization of critical structures is not otherwise possible.

Development of a computer-aided design software for dental splint in orthognathic surgery

In the orthognathic surgery, dental splints are important and necessary to help the surgeon reposition the maxilla or mandible. However, the traditional methods of manual design of dental splints are difficult and time-consuming. The research on computer-aided design software for dental splints is rarely reported. Our purpose is to develop a novel special software named EasySplint to design the dental splints conveniently and efficiently. The design can be divided into two steps, which are the generation of initial splint base and the Boolean operation between it and the maxilla-mandibular model. The initial splint base is formed by ruled surfaces reconstructed using the manually picked points. Then, a method to accomplish Boolean operation based on the distance filed of two meshes is proposed. The interference elimination can be conducted on the basis of marching cubes algorithm and Boolean operation. The accuracy of the dental splint can be guaranteed since the original mesh is utilized to form the result surface. Using EasySplint, the dental splints can be designed in about 10 minutes and saved as a stereo lithography (STL) file for 3D printing in clinical applications. Three phantom experiments were conducted and the efficiency of our method was demonstrated.

Nerve injury associated with orthognathic surgery. Part 2: inferior alveolar nerve

The inferior alveolar nerve (IAN) is the most commonly injured structure during mandibular osteotomies. The prevalence of temporary injury has been reported as 70/100 patients (95% CI 67 to 73/100) or 56/100 nerves (95% CI 46 to 65/100), and the prevalence of permanent alteration in sensation was 33/100 patients (95% CI 30 to 35/100) or 20/100 nerves (95% CI 18 to 21/100) when assessed subjectively. The prevalence varied significantly between different operations (p<0.0001). It was significantly higher for sagittal split osteotomy (SSO) combined with genioplasty than for SSO alone (p<0.0001) or vertical ramus osteotomy (VRO) (p<0.0001). Injury may result from traction during stripping or manipulation of the distal fragment, incorrect placement of the cuts, or misjudged placement of fixation in ramus ostotomy. During SSO, they can occur during retraction to make cuts in the medial ramus, when the bone is cut or split, and on fixation. The impact of injury is generally said to be low as it does not seem to affect patients' opinions about the operation.

Preoperative, intraoperative, and postoperative complications in orthognathic surgery: a systematic review

Objectives

The aim of this study was to determine whether orthognathic surgery is associated with any complications, and what type of complications may occur.

Materials and methods

Data were obtained using PubMed (MEDLINE), ISI Web of Knowledge, Ovid, Cochrane Library, Embase Library, and an additional manual search. The titles and abstracts of the electronic search results were screened and evaluated by two observers for eligibility according to the inclusion and exclusion criteria.

Results

A total of 1924 articles were identified, and we retained 44 articles for the final analysis. The Prisma diagram flowchart demonstrates our selection scheme. For the purpose of this study, the Cochrane data extraction form was modified. One review author extracted data from the included studies, and the second author checked all of the forms. The hierarchy of evidence classification from the UK NHS Centre for Reviews and Dissemination was used to assess the level of evidence for the retrieved studies.

Conclusions

An evaluation of the obtained studies revealed the existence of a large number of varied complications associated with orthognathic surgery procedures.

Clinical relevance

Oral and maxillofacial surgeons, orthodontists, and the surgical team need to prevent such complications during preoperative, intraoperative, and postoperative periods to increase the safety of orthognathic surgery procedures. This review was registered on http://www.crd.york.ac.uk/PROSPERO as CRD42013004711.

Electronic supplementary material

The online version of this article (doi:10.1007/s00784-015-1452-1) contains supplementary material, which is available to authorized users.