Mandibular Symphyseal Distraction Research Articles

Impact of Mandibular Symphyseal Distraction Osteogenesis (MSDO) on the Sagittal Dimension and Long-Term Skeletal stability.

To evaluate the long-term effects of mandibular symphyseal distraction osteogenesis (MSDO) on the correction of class II malocclusion correction and dental crowding. Twenty-two patients received MSDO and presented class II malocclusion with transverse mandibular discrepancy. The authors collected data on 2 different cephalometric analyses. On Tweed analysis, The authors recorded ANB, SNA, SNB, and FMA angles. On Delaire analysis, we recorded the distance from Pti (pterygoid inferior) to ENAt (anterior nasal spine) and the distance from Cos (superior condyle) to Pog (pogonion). Superimpositions studies were performed at pre-treatment phase (T1) and post-treatment phase (T2) to evaluate the new position and changes in the dimensions of the mandible and maxilla. On superimposition of Tweed analysis of T1 and T2, reduction of ANB was seen in 18 patients, no change in ANB in 2 patients, and increase in ANB (by 1 deg) in 2 patients. Superimposition of Delaire analysis showed a mean difference of 0.3mm (SD, 3.6mm) between T1 and T2 for the maxilla and a mean difference of 6.0mm (SD, 7.3mm) for the mandible. Mandibular symphyseal distraction osteogenesis performed after the pubertal growth peak can effectively correct class II malocclusion and dental crowding with a single light surgical procedure.

Should Mandibular Symphyseal Distraction Osteogenesis be considered in OSA Surgery?

Surgical maxillary expansion for the treatment of obstructive sleep apnea (OSA) has become common place. To maximize airway improvement, over-expansion of the maxilla can occur, resulting in an excessively widened maxilla that creates a mismatch to the mandible. Therefore, mandibular symphyseal distraction osteogenesis (MSDO) to widen the mandible along with maxillary expansion is being increasingly advocated in OSA surgery. The authors discuss their 20-year experience with MSDO and surgical maxillary expansion. They also analyze the airway impact between Distraction Osteogenesis Maxillary Expansion (DOME) and Endoscopically-Assisted Surgical Expansion (EASE) based on currently available computational fluid dynamic (CFD) data, which has implications in whether MSDO needs to be considered. The goal of surgical maxillary expansion is to enlarge the nasal cavity and reduce the airway resistance. CFD data demonstrates that EASE results in a much greater reduction in airway resistance as compared to DOME. EASE achieved a 12-fold reduction in nasal airway resistance compared to 3-fold reduction by DOME; a 12-fold reduction of retropalatal airway resistance as compared to 3-fold reduction by DOME; a 10-fold reduction of oropharyngeal airway resistance as compared to a 3-fold reduction by DOME, and an 8-fold reduction of hypopharygeal airway resistance as compared to a 3-fold reduction by DOME. Because there is no physiologic basis or data that demonstrates mandibular widening improves OSA, an airway centric surgical expansion technique such as EASE can achieve a much greater airway impact without needing excessive maxillary widening, thus eliminating the necessity MSDO.

Hybrid mandibular Bologna midline distractor in combination with surgically assisted rapid maxillary expansion for transverse facial expansion: clinical and cephalometric results

Transverse maxillomandibular hypoplasia can be treated with surgically assisted rapid maxillary expansion (SARME) in association with mandibular symphyseal distraction (MSD). This paper introduces a hybrid mandibular Bologna midline distractor (BMD); the effectiveness of the distractor in combination with SARME for the treatment of transverse skeletal deficiency was evaluated. This two-centre study included 10 patients with a transverse arch width deficit>7 mm and dental crowding, in both the maxilla and mandible, treated with SARME and MSD. The study design was partly retrospective (seven patients) and partly prospective (three patients). Frontal and lateral cephalometric analyses, as well as measurements on dental models, were performed at three different times: before treatment, after the distraction, and 6 months after postoperative orthodontic treatment. The cephalometric analyses and measurements on dental impressions confirmed a balanced and stable skeletal and dental mandibular expansion. An average symphyseal expansion of 7.8 mm was obtained, resolving dental crowding without dental extractions. In conclusion, mandibular expansion performed with the BMD in combination with SARME appears to be a viable surgical approach to transverse maxillomandibular hypoplasia. This technique allows the surgeon to obtain a balanced skeletal and dental expansion, with a low level of relapse.

Mandibular Symphyseal Distraction Osteogenesis―A Review

Mandibular symphyseal distraction osteogenesis (MSDO) is nothing but regular distraction osteogenesis (DO)performed at the symphysis wherein, the new bone formation occurs between bone segments that are gradually separated by incremental traction”.Treatment planning decisions in the transverse dimension are based on the mandibular arch width and form. Mandibular symphyseal distraction osteogenesis supplements orthodontic treatment to resolve mandibular anterior width deficiencies or dental crowding.This article focuses on indications, orthodontic preparation, surgical procedures, complications, long term effects and stability of mandibular symphyseal distraction osteogenesis.

Pharyngeal airway changes following symohyseal distraction osteogenesis

Introduction: The aim of this study was to analyze the effects of mandibular symphyseal distraction osteogenesis (MSDO) on the pharyngeal airway dimensions in a group of adult patients.Subjects and Methods: The sample consisted of digital lateral cephalograms of 10 patients (7 females and 3 males)with a mean age of 21.0 ± 2.5 years. Radiographs were taken before start of distraction (T1) and following distraction(T2) (12.5 days ± 2.3 days after surgery). Symphyseal distraction was done using a bone-borne distractor. The mean value of mandibular symphyseal distraction was 8.4 ± 1.7 mm. Digital lateral cephalometric tracing was done to evaluate airway changes following symphyseal distraction.Results: Digital lateral cephalometric analysis revealed no statistically significant changes in nasopharyngeal airway(0.3 ± 0.1 mm) (P > 0.05). There were statistically significant changes in oropharyngeal and hypopharyngeal airway widths (1.2 ± 0.3 mm) and (0.7 ± 0.4 mm) respectively (P 0.05) while statistically significant decrease were evident for the vertical measurement H-C3RGN (- 1.2 ± 0.2 mm) (P < 0.01).Conclusion: The results propose that MSDO significantly affects the lower pharyngeal airway dimensions but has no effect on the upper pharyngeal airway measurements. No significant effects on hyoid bone position were observed except mild decrease of its vertical measurement to reference planes. The normal reflex mechanisms that conserve the patency of the airway may have negated any potential changes in the hyoid bone position.

Mandibular symphyseal distraction osteogenesis: 20 years of experience treating transverse deficiencies with an internal hybrid device

IntroductionTransverse mandibular deficiency has been traditionally managed by orthodontic compensation. However, without resolving the underlying skeletal hypoplasia it leads to high relapse rates. Few studies have reviewed the long-term experience and potential complications of mandibular symphyseal distraction osteogenesis (MSDO) as an alternative treatment method. Materials and methodA retrospective review of 20 patients (range: 4–19 years; mean: 11.9 years) treated with a hybrid MSDO device over the period of 1996–2017 was conducted. Epidemiological data, medical and dental history as well as photographic and cephalometric analyses were carried out. Furthermore, pre-operative and long-term post-operative status including dental occlusion and tooth-jaw discrepancies were recorded. ResultsThe distraction amount ranged from 3 mm to 15 mm (mean: 10 mm) with an average distraction period of 30.9 days. In long-term follow-up (mean: 7.3 years), 14 patients presented a class I and 6 patients presented a class II relationship. Correction of overjet, tooth jaw discrepancy and arch length discrepancy were obtained in 18, 20 and 17 cases respectively. A device malfunction was experienced in 6 patients. ConclusionMandibular widening using a hybrid MSDO device can be efficiently and safely performed in a paediatric population. Further studies confirming our results and analysing facial aesthetic outcomes are warranted.

Symphyseal bone distraction (part 1): benefit / risk ratio. A systematic literature review

The purpose of this systematic literature review is to evaluate the benefit / risk ratio of mandibular symphyseal distraction osteogenesis. Searches were made on Pubmed/Medline and Cochrane for randomized clinical trials and case series involving mandibular symphyseal distraction over the past 20 years with a patient sample greater than or equal to 10. Of the 92 articles, 25 met the inclusion criteria. A controlled trial was selected, but no randomized trial. The other studies were all case series, 16 retrospective and 8 prospective. Distractors with bone or hybrid anchorage appear to lead to more periodontal and infectious complications due to the buccal position of the jack. Most complications are benign. However, the most difficult event to deal with is distraction device fracture. Symphyseal midline distraction increases the transverse dimension efficiently, reliably and sustainably, and appears to have no demonstrated deleterious effects on the ATMs for the three types of distractors. Tooth-borne devices are recommended in most cases given their benefit / risk ratio. Furthermore, they do not require a second surgical procedure to remove them. Mandibular symphyseal distraction osteogenesis is a reliable therapy whose exact limits and reproducibility remain to be defined by future prospective studies.

Symphyseal bone distraction (part 2): which protocol in 2018? A systematic literature review

The aim of this systematic literature review is to propose a clinical protocol in 2018 by comparing therapeutic efficacy and undesirable effects of the technique. Searches were made on Pubmed/Medline and Cochrane for randomized clinical trials and case series involving mandibular symphyseal distraction over the past 20 years with a patient sample greater than or equal to 10. Of the 92 articles, 25 met the inclusion criteria. A controlled trial was selected, but no randomized trial. The other studies were all case series, 16 retrospective and 8 prospective. Dental crowding over 7 mm, with or without compensation, is an indication for mid-symphyseal distraction. Pre-surgical orthodontic treatment ensures root divergence between the mandibular incisors. Tooth-borne devices are recommended in first intention. Surgical intervention (ambulatory) under local anesthesia and intravenous sedation is considered. The latency period before activation of the jack is 6 days. Activations are performed by the orthodontist and subsequently by the patient at a rate of 1 mm per day, with four activations daily. Orthodontic movements are resumed two weeks after activations are discontinued. The distractor is removed within two to three months after installation. Although the main features of the mid-symphyseal distraction protocol were drawn up essentially in the light of expert opinion, they still need to be refined by controlled trials.

Comparison of two preoperative protocols for mandibular symphyseal distraction osteogenesis to reduce the risk of tooth damage

Two techniques to separate the lower incisors prior to mandibular symphyseal distraction osteogenesis (MSDO) were evaluated with respect to avoiding tooth damage. MethodsFifty patients (20.2 ± 7.0 years) requiring MSDO were treated with a tooth-borne appliance by utilizing two preoperative protocols to separate the central incisors: i) brackets and a V-bent wire with an open coil spring (two-step; TS; n = 24) and ii) a wire attached from the appliance to the central incisors with subsequent dento-alveolar expansion prior to surgery (one-step; OS; n = 26). The distance between the lower incisors was measured preoperatively on radiographs and measurements at the cast models were performed. Complications and radiographs were analyzed. ResultsThe mean distance (±SD) between the lower central incisors for OS and TS prior to surgery was 3.44 ± 1.05 and 3.18 ± 1.13 mm, respectively. The mean expansion for OS and TS was 4.3 ± 2.9 and 4.3 ± 2.7 mm at the dental level and 3.8 ± 3.2 and 4.0 ± 2.1 mm at the bone level, respectively. Four patients undergoing the TS and one patient undergoing the OS showed transient dental complications. ConclusionPre-surgical dento-alveolar expansion by utilizing a one-step technique to separate the lower central incisors reduces the risk of permanent tooth damage and weakens the mandibular bone in the midline.

New Technique for Mandibular Symphyseal Distraction by a Double-Level Anchorage and Fixation System: Advantages and Results.

A surgical technique to widen the mandible is the mandibular midline distraction: the most common indications for mandibular midline distraction are severe mandibular anterior crowding, severe mandibular transverse deficiency, uni- or bilateral crossbite, impacted anterior teeth with inadequate space, and tipped teeth. Commonly used distraction devices can be divided into 2 systems: bone-borne distraction system appliance, dental-borne distraction systems. Each system has peculiar advantages, disadvantages, and different indications. To combine advantages of both systems we developed a new technique adopting an immediate basal bone widening with fixation after osteotomy and a dental borne rigid lingual system for distraction. The aim of this work is to show a new technique for symphysis mandibular distraction based on a double-level anchorage and fixation system on clinical patients showing final results and advantages. Two patients affected by dento-alveolar and basal bone maxillary and mandibular transversal collapse even in association with other skeletal malocclusion were selected. Patients were clinically and radiographically studied and analyzed at different times before and after surgery. Dental and basal bone measurements were performed clinically and radiographically. The results were optimal with perfect dental arches alignment followed by closing of the open bites with multiple-segmented surgery in a second surgical time. No misalignment of the 2 mandibular halves was noticed during the distraction procedure. Dental-bone discrepancies correction is mandatory before orthodontic treatment alignment. Transversal jaw expansion can be achieved safely and stably by distraction of both maxillae for the combination of osteogenesis and histogenesis with augmentation of both bone and soft tissue. Bone-borne distraction will result in more stable results; dental-borne devices will result in more simple and aesthetically rewarding procedures. Hybrid techniques usually show mixed results depending on the characteristics of the device. For this reason we developed a combination of both the aforementioned systems which is not a hybrid system but the combination of an immediate expansion of the symphysis and fixation by 1 miniplate with only 2 screws acting like hinges during distraction, combined with a lingual distraction system at the alveolar bone level. Bone-borne distraction systems result in more efficient basal bone mandibular widening with increased stability for dental results. For dental-borne appliance the advantages consist in no second surgery need for their removal, no transmucosal hardware emergence and better aesthetic, especially when lingual devices were used. Our technique combines advantages of both procedures.

Biomechanical Effects of Novel Osteotomy Approaches on Mandibular Expansion: A Three-Dimensional Finite Element Analysis

Surgically assisted mandibular arch expansion has proved to be an effective treatment modality in alleviating constriction and crowding issues. However, only mandibular symphyseal distraction osteogenesis has been in favor for the purpose of mandibular arch expansion. In addition, no relevant study has compared the biomechanical response of different osteotomy designs on mandibular expansion. The present study evaluated the effect of different osteotomy approaches and modes of loading on the expansion of the adult mandible using biomechanics. To address the research purpose, 9 finite element (FE) models, including 2 novel osteotomy designs, were simulated. Stress, strain, and displacement of crown, root, and bone were calculated and compared under different osteotomy approaches and loading conditions. The biomechanical response envisaged by the FE models in terms of displacement on the X axis was consistent from the anterior to posterior teeth with parasymphyseal step osteotomy and a hybrid mode of force application. In addition, the amount of displacement predicted by parasymphyseal step osteotomy with the hybrid mode was greater compared with that of the other models. The results of our study suggest parasymphyseal step osteotomy with the hybrid mode is a viable treatment option for true bony expansion in the adult mandible.

Contribution of mandibular symphyseal distraction osteogenesis to our therapeutic strategies

Distraction osteogenesis helps create new bone by using the natural bone repair process. This technique, applied to the symphysis, affords a new perspective: increasing the mandibular transverse dimension in a stable way due to a simultaneous expansion of the skeletal structure. In this respect, it represents a potential alternative to therapy conventionally implemented to remedy dental crowding and mandibular transverse deficiency. All the same, the technique remains marginal as it is considered to be too invasive and risky. With the exception of the patient’s cooperation, the success of mandibular symphyseal distraction osteogenesis (MSDO) relies on three main points: good knowledge of indications, strict compliance with the protocol, and lastly the prevention and management of possible complications. After reviewing these three sections, we will cover a few clinical applications.

Stability and Effects of Mandibular Symphyseal Distraction Osteogenesis: A Systematic Review

Stability and Effects of Mandibular Symphyseal Distraction Osteogenesis: A Systematic Review

Skeletal and dental effects of tooth-borne versus hybrid devices for mandibular symphyseal distraction osteogenesis

To evaluate and compare, retrospectively, the skeletal and dental effects of mandibular symphyseal distraction osteogenesis (MSDO) achieved through the use of tooth-borne versus hybrid distractors. Pretreatment (T1), predistraction (T2), postdistraction (T3), and posttreatment (T4) orthodontic records were collected and analyzed for 47 patients (20 tooth-borne, 27 hybrid). At each time point, records included intraoral photographs, study models, postero-anterior cephalometric radiographs, and lateral cephalometric radiographs. Submental vertex radiographs were taken at T2, T3, and T4. Changes in a total of 18 measurements were analyzed to compare patients undergoing tooth-borne versus hybrid distraction. The cumulative effects of orthodontics and MSDO produced similar gains in measured arch widths, with a decreased irregularity index in both groups (P > .05). However, there were differences in the timing during which the expansion was achieved. The hybrid distractor group gained space during the distraction phase of treatment. The tooth-borne group showed greater gains during pre- and postdistraction orthodontics. Comparisons of intercanine and interbone marker widths demonstrated a more parallel separation of bone during distraction with the hybrid distractor (P < .001). Distraction with the tooth-borne distractor was disproportionate, with greater separation of the canines in alveolar bone than of the bone markers in basal bone. During postdistraction orthodontics, the tooth-borne distractor group showed statistically greater increases in measurements. Both skeletal and dental expansion was achieved with both appliances. Greater skeletal expansion was achieved with a hybrid distractor. Greater dental expansion was achieved with a tooth-borne distractor.

Semirapid Maxillary Expansion and Mandibular Symphyseal Distraction Osteogenesis in Adults: A Five-Year Follow-up Study

The aim of this study was to evaluate the long-term effects of semirapid maxillary expansion (SRME) and mandibular symphyseal distraction osteogenesis (MSDO) on dentofacial structures in adult patients. The sample comprised posteroanterior cephalograms of 14 patients, with an age range between 15.8 and 25.01 years (mean, 20.09 ± 2.36 years) at the start of treatment. Records were obtained before treatment (T1, day 0), at the end of SRME and MSDO retention (T2, 4.57 ± 0.65 months), at the end of orthodontic treatment (T3, 22.14 ± 4.69 months between the end of SMRE/MSDO retention of SRME/MSDO and end of orthodontic treatment), and after a 5-year follow-up period (T4, 4.99 ± 1.00 years, between the end of orthodontic treatment and follow-up). Data were analyzed statistically by using the repeated measure analysis of variance and paired t test. Statistically significant changes were observed in the lower nasal, bimaxillary, upper molar, upper incisors, lower molar, and lower incisors at the end of the retention period ( P

Long-term skeletal and dental stability of mandibular symphyseal distraction osteogenesis with a hybrid distractor

The purpose of this study was to examine the long-term skeletal and dental stability of mandibular symphyseal distraction osteogenesis (MSDO) with a tooth-borne and bone-borne hybrid distractor. To differentiate the effects of MSDO from the orthodontic movement and relapse, each phase of treatment was analyzed. Twenty-five patients were included in the study, ranging in age from 12.0 to 30.9 years at the initiation of treatment (mean, 15.8 ± 4.8 years). Of this group, 16 patients were recalled at a mean of 7.5 ± 0.9 years (range, 6.3-9.6 years) after distraction for long-term analysis of skeletal and dental changes. Orthodontic records were taken at 5 times: T1, pretreatment; T2, predistraction; T3, postdistraction; T4, posttreatment, and T5, postretention. The data were statistically analyzed by using repeated-measures analysis of variance (ANOVA). There were significant increases in all interdental transverse measurements except the mandibular intersecond molar distance from T1 to T4. The largest overall expansion was achieved between the mandibular second premolars (4.32 ± 0.60 mm), followed by the interfirst premolar (3.44 ± 0.44 mm), the interfirst molar (2.60 ± 0.65 mm), and the intercanine (1.87 ± 0.44 mm) widths. The overall amount of transverse dental expansion was substantially less when analyzed from the time of the mandibular symphyseal osteotomy to posttreatment (T2-T4). From T3 to T4, there were significant decreases between the mandibular intersecond premolars (-3.10 ± 0.52 mm), interfirst premolars (-3.90 ± 0.35 m), intercanines (-4.47 ± 0.38 mm), and intercentral incisors (-5.60 ± 0.32 mm). There were no significant changes in bicondylar, bigonial, and biantigonial widths. At the long-term follow-up, there were no significant changes in the interdental or skeletal measurements between T4 and T5, except for interincisor apices. The irregularity index significantly decreased during the orthodontic treatment but significantly increased in the long-term follow-up period (T4-T5). After the MSDO, T3 to T5, the results indicated symphyseal basal bone skeletal stability. The results indicate that the expansion of the mandibular arch with MSDO and conventional orthodontic mechanics produces no statistically significant transverse changes from posttreatment to long-term follow-up. The risks of using a surgical procedure and MSDO to achieve additional expansion should be evaluated by the clinician and compared with more traditional orthodontic methods.

Treatment of unilateral buccal crossbite with mandibular symphyseal distraction osteogenesis

The aim of this report is to present the treatment of a 14-year-old boy with scissors-bite. Mandibular symphyseal distraction osteogenesis (MSDO) with tooth-supported distractor was performed to expand the mandible, and intermaxillary cross elastics were used. The mandible was expanded approximately 9 mm. Asymmetric widening was done by using cross elastics and MSDO simultaneously. The buccal crossbite was corrected successfully. After a 2-year observation period, widening of the mandible using this procedure was judged to be stable. (Korean J Orthod 2011;41(1):59-69)

Changes in the mandibular and dento-alveolar structures by the use of tooth borne mandibular symphyseal distraction devices

Purpose Different devices to perform a mandibular symphyseal distraction osteogenesis (MSDO) are available. This study evaluates how tooth borne distraction devices change to the teeth, the mandible and the condyles. Materials and methods 19 patients (mean age 27.1) with anterior width deficiencies of the mandible were examined with routine pre- and postoperative CT-scans 1 month before and 4 months after a mean distraction width of 5.68 mm (SD 0.88). The anchorage teeth of the tooth borne device were examined concerning displacement of their axes as well as the movement of the condyles and the mandibular symphysis. The data were evaluated using Wilcoxon signed rank test and Spearman rho correlation. Results Significant tilting of the anchorage teeth was observed ( p < 0.01). The axes changed by 3.32° (SD 1.57) in the first premolar and by 2.63° (SD 1.75) in the first molar. A total of 2.67 mm (SD 1.17) of bone was formed on the symphysis. A significant correlation was found between distraction width and intercoronal distance changes of the anchorage teeth ( p < 0.01). No significant change of the intercondylar distance was found pre- and postoperatively in the Wilcoxon test. Conclusion MSDO with tooth borne devices has strong effects on the anchorage teeth. No severe effects on the condyles were observed. The postoperative width gain is a result of newly generated bone in the symphysis and tooth tilting. Nevertheless stable postoperative bite corrections are achievable.

Analysis of the performance of different orthodontic devices for mandibular symphyseal distraction osteogenesis

The aim of this study was to investigate the performance of different orthodontic devices for mandibular symphyseal distraction osteogenesis (MSDO). Two performance parameters were analysed, the first of which concerned the stability guaranteed by a distractor in the fracture gap under mastication loads and the second the level of reliability with which a distractor transfers a given expansion to the mandibular bone, inasmuch as the more reliable the device the smaller the difference between the degree of expansion provided to the device and the displacement achieved on the mandibular arch. Hence, a non-linear finite element (FE) model of a human mandible with different devices (tooth-borne, bone-borne, and hybrid) was constructed and then utilized to assess the structural behaviour of the mandibular bone under distraction and mastication loads. An ad hoc algorithm was developed to simulate progressive expansion of the devices; a distraction protocol comprising a 10 day latency period and a 6 day distraction period was hypothesized. The first hypothetical expansion given to the device was 2 mm, and the five subsequent expansions were 1 mm. The results showed that the hybrid device was the most stable appliance under mastication loads, followed by the tooth- and bone-borne devices. However, parasitic rotations of the mandibular arms caused by mastication might counteract the benefits of distraction. The tooth-borne device was found to have the highest reliability in transferring expansion to the mandibular bone. For this device, mandibular expansion was less than the nominal aperture of the distractor by no more than 15 per cent. Lower values of reliability were achieved with the bone-borne device. As the values of the aperture of the appliances increased, the stability guaranteed in the fracture gap increased while the reliability in transferring expansion to the mandibular arch decreased.

Six year follow-up of a patient treated with mandibular symphyseal distraction osteogenesis

In this report, treatment and long term effects of mandibular symphyseal distraction osteogenesis (MSDO) on dentofacial structures are presented. The distraction device used in the present case was a custom made tooth- and bone-borne distractor. Post-treatment records revealed elimination of mandibular anterior crowding, no temporomandibular joint (TMJ) disorder, no periodontal pathology and no root resorption. Follow-up records taken 6 years after the completion of the treatment indicated no mandibular anterior crowding or TMJ disorder. Treatment and long term results of this case suggest that mandibular widening with distraction osteogenesis is an efficient, safe and stable treatment modality for patients presenting transverse mandibular deficiency and/or mandibular anterior dental crowding. However, large sample studies are required to draw substantial conclusions about the long term effects of the MSDO on dentofacial structures.