Three-dimensional soft tissue effects of mandibular midline distraction and surgically assisted rapid maxillary expansion: an automatic stereophotogrammetry landmarking analysis.

Studies on mandibular midline distraction (MMD) are mostly performed using conventional research methods. Concerning surgically assisted rapid maxillary expansion (SARME), more research is conducted using three-dimensional (3D) techniques. Research on bimaxillary expansion, the combination of MMD and SARME, is reported sparsely. The main objective of this study was to provide a 3D evaluation of soft tissue effects following SARME and/or MMD. Patients who underwent SARME and/or MMD between 2008 and 2013 were included. Stereophotogrammetry was undertaken at the following time points: preoperative (T1), immediately post-distraction (T2), 1year postoperative (T3). An automatic 3D facial landmarking algorithm using two-dimensional Gabor wavelets was applied for the analysis. Twenty patients who had undergone SARME were included, 12 of whom had undergone bimaxillary expansion. Age at the time of surgery ranged from 16 to 47 years. There was a significant downward displacement of soft tissue pogonion. Furthermore, there was a significant mean increase of 2.20mm in inter-alar width and a non-significant mean increase of 1.77mm in inter-alar curvature point width. In conclusion, automatic stereophotogrammetry landmarking analysis of soft tissue effects showed downward displacement of soft tissue pogonion following bimaxillary expansion and transverse widening of the inter-alar width and a tendency towards an increase in inter-alar curvature point width after SARME.

Follow up of surgically-assisted rapid maxillary expansion after 6.5 years: skeletal and dental effects.

Surgically-assisted rapid maxillary expansion (SARME) is a technique used to widen the maxilla, and we present the results of our long-term follow up (6.5 years). Seventeen patients who had been treated with SARME and prospectively followed were invited for long-term follow up using dental casts and posteroanterior cephalograms. The following measurements were made on the dental casts: transverse distances at canine, premolar, and molar level, length of the arch, and width and depth of the palate at premolar and molar level. The distance between the left and right nasal bases and the widening of the inferior maxilla were measured on the posteroanterior cephalograms. Boneborne and toothborne distractors were used in 8 and 9 patients, respectively. In the study of dental casts, there was a significant increase in transverse width in the canine (P<0.001), premolar (P<0.001) and molar (P=0,001) and these remained stable in the long term. The arch length did not increase significantly, but the palatal width increased significantly in the premolar (P<0.001) and molar (P=0.001) regions. No effect was seen in palatal depth. On the posteroanterior cephalograms the width of the inferior part of the maxilla was increased, but not significantly so. There were no significant changes at the nasal base. We conclude that SARME is a predictable technique to widen the maxilla in the long term.

Long-term (6.5 years) follow-up of mandibular midline distraction.

To assess the long-term stability and biomechanical effects of mandibular midline distraction (MMD), a prospective observational study was conducted with a retrospective cohort. Included were 17 MMD patients, of whom 9 completed the long-term follow-up with a mean of 6.5 years. In all patients, a bone-borne distractor was used. Dental casts and postero-anterior (PA) cephalograms were taken at fixed time points: pre-operative (T1), directly post-distraction (T2), 1-year post-operative (T3) and long-term follow-up (T4). Inter canine (ICD), inter first premolar (IPMD), inter first molar (IMD) distances and arch length (AL) were measured on dental casts. From the PA cephalograms intercondyle distance (ID) and the ramal angle (RA) were obtained. A significant and sustained widening was observed in most measurements. The greatest overall transverse expansion (T1-T4) occurred in the IPMD (4.1 ± 0.76 mm, P < 0.05), the ICD, IMD and AL increased, respectively: 2.0 ± 0.72 mm, 3.8 ± 0.82 mm and 3.5 ± 0.82 mm. The ID did not change significant (P > 0.05) during all phases of the study. An increase of RA was observed initially; however, no difference was noted in the long-term. This study showed that MMD is a stable method to expand the mandible, with no skeletal effect on the temporomandibular joint.

Introduction of the "Rotterdam mandibular distractor" and a biomechanical skull analysis of mandibular midline distraction.

The Rotterdam mandibular distractor (RMD) is a slim, rigid, boneborne distractor for use in midline distraction of the mandible. We did a biomechanical study to compare the RMD with the Trans Mandibular Distractor-flex (TMD-flex). This included an anatomical biomechanical study that was conducted on 9 dentate human cadaveric heads using both the RMD and the TMD-flex. In the vertical plane less tipping was measured in the RMD group than in the TMD-flex group. Significantly less skeletal tipping was found in the horizontal plane in the RMD group (P=0.021). There was minimal difference in the intercondylar distance between the groups. As the amount of lateral displacement of the condyle was similar in both groups and there was less rotational movement in the RMD group, the TMD-flex would be expected to increase stress on the temporomandibular joint. As a result of the increased parallel widening in the vertical plane, more basal bone is being created and less relapse is expected using the RMD. The study design involves an in vitro anatomical model and conclusions must be drawn with care. At present clinical studies are under way and results will follow.

Mandibular midline distraction: a systematic review.

INTRODUCTION: A systematic review of mandibular midline distraction (MMD) was carried out to assess effectiveness, treatment related difficulties, complications and biomechanical effects of this treatment modality objectively. MATERIAL & METHODS: Randomized controlled trials (RCT), controlled clinical trials (CCT) and case series concerning MMD with a sample size of >5 were searched electronically in Pubmed/Medline, Embase, Cochrane and CENTRAL up to September 6th 2010. RESULTS: 85 unique articles were found of which 22 met our inclusion criteria. The study designs of the articles found were prospective (9), retrospective (9) or uncertain (2). One clinical trial and no randomized clinical trials were found. The methodological quality was considered low in most articles. CONCLUSION: Generally MMD is a safe and effective treatment modality to treat transverse mandibular discrepancies, however controversies still exist: choice of distractor, surgical setting, distraction rate, start of orthodontic treatment and relapse. In addition, little is known about patient experience and quality of life after treatment. Further prospective trials are necessary to address these controversies and questions.