It has been evident from the literature that the reports of response of the lower lip and soft tissue chin to the surgical advancement of the deficient lower jaw are strongly discrepant. Therefore, the objective of this study was to improve the understanding of the soft tissue response, with particular reference to the role of the preoperative soft tissue thickness. It has become evident from a review of current studies that tissue thickness may not play as significant a role as was previously thought, thus indicating the role of other factors in the prediction of the lower lip and chin response for the individual. This study assessed the soft tissue changes of the lower lip within a homogenous sample group of 39 patients who had undergone a surgical advancement of the lower jaw. Lateral cephalometric radiographic records at time periods before and after the surgical procedure were used. The radiographs were hand traced and specific landmarks were computer digitized with the Analysis System (Olympus Pty, Ltd) relative to a constructed X-Y axis. The change in the position of these landmarks at the various time periods was calculated according to the mean value of each reading for each landmark. Multiple regression analyses of the data resulted in poor correlations of the lower lip position with the extent of mandibular advancement surgery when the variables of horizontal overjet and the vertical overbite of the incisors, the lower lip thickness (lower incisor tip to labrale inferius as well as lower lip protrusion ahead of the upper incisor teeth) and the pre-operative soft tissue thickness were included (0.27 in the horizontal dimension; 0.51 in the vertical dimension). The addition of the variables tissue thickness and lower lip thickness within the multiple regression equation did not result in a notable improvement in coefficients of correlation either (0.77 to 0.78). Within the stepwise regression equations specific variables have been identified as having an influence on the prediction of the response of the lower lip and chin consequent to the mandibular advancement surgery (R2=0.93-0.97(horizontal); R2=0.89-0.96(vertical)). These points include stomion, upper incisor tip, hard and soft tissue pogonion, lower incisor tip, gnathion and menton. The prediction equations were independently cross-validated against each individual within the sample group, achieving high cross-correlation values (0.85-vertical to 0.90- horizontal) between the prediction equation and the observed values. The findings of this study have identified factors that play a role in the soft tissue response of the lower lip and chin consequent to mandibular advancement surgery, enabling a more accurate prediction for the individual.

Department of Maxillofacial and Oral Surgery, 2013 / One of the goals during surgical repositioning of the mandible is to ensure a correct condyle-fossa relationship and to maintain the position of the proximal segment at the time of placement of rigid fixation. During setback procedures, accurate control of the proximal segment is influenced by the medial pterygoid muscle and stylomandibular ligament. These structures are therefore stripped from the medial surface of the mandibular angle during surgery. The aim of this study was to investigate the influence of the muscle attachment on proximal segment control in mandibular advancement surgery. Clockwise or counterclockwise rotations of the proximal segment during surgery of two groups of patients were compared. In one group, the medial pterygoid muscle was stripped during surgery while in the other group the medial pterygoid muscle was left attached. The second group formed part of the historical development phase of the surgical technique for mandibular advancement procedures.

Submitted in partial fulfillment of the requirements for the degree of Master in the Science of Dentistry, in the department of Oral and Maxillofacial Surgery, at the University of the Witwatersrand, Johannesburg. / The correction of most skeletal class II mandibular deficient cases require the surgical advancement of the mandible for the treatment of the malocclusion. Often genioplasty is included to the procedure to improve the soft tissue profile.2,30 Long term skeletal stability is an important goal for the surgeon and orthodontist following Bilateral Sagittal Split Osteotomy (BSSO) and is influenced by the muscles attached to the mandible. Following the surgical advancement of the mandible the suprahyoid muscle complex is certainly stretched and even more so when the procedure is combined with surgical advancement of the chin.10,11 This retrospective comparative study determined the long term skeletal stability of 29 patients, whom had undergone surgical advancement of the mandible by means of BSSO with advancement genioplasty, compared to 29 patients whom had undergone mandibular advancement surgery (BSSO) without advancement genioplasty. All the subjects were evaluated using pre-operative (T1), 1 week post-operative (T2) and at least 6 months (T3) follow-up cephalometric radiographs. This research report concluded that the post-operative hard tissue relapse following BSSO advancement, with or without genioplasty, was clinically insignificant.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Objectives: This retrospective study aims to compare the effect of different mandibular setback amount by vertical subsigmoid osteotomy (VSSO) on the pattern of condylar remodelling in both metric and morphologic analysis at 1 year post surgery. Materials and Methods: 200 patients diagnosed of mandibular prognathism and had undergone VSSO with various setback amounts from 2007 until 2012 at the Prince Philip Dental Hospital were included in this study. Presurgical and 1 year post surgical Postero-Anterior Cephalogram, Lateral Cephalograms and Cone Beam Computed Tomography (CBCT) Scans were retrieved. Tracings of plain cephalometric radiographs were performed. CBCT data sets were used to create 3D condyles to measure the linear and condylar axis angle value in multiplanar view. Finally the pre and postsurgical 3D condyle-ramus units were superimposed using stable registration point in the condylar neck and ramal area above the lingual to assess the condylar bone remodelling by topographic and multiplanar slide views. Result: From the plain radiographic tracings, there were no significant differences in the changes of ramus inclination angle, intergonial width and total ramus angle between postoperative (T2) and preoperative (T1) values across the setback groups. A gradual increase in the postoperative sagittal condylar axis angle is detected with greater setback in the CBCT multiplanar analysis while other linear and angular condylar changes were not significantly different. 3D Topography (T2 -T1) superimposition analysis of the condylar surface showed no significant relation between the remodelling changes and the setback magnitude except at the superior posterior zone. Multiplanar view (T2-T1) superimposition analysis in the coronal and sagittal planes showed no significant relationship between the remodelling changes and the setback magnitude. However there was higher proportion of positive remodelling following higher setback amount at the midanterior and posteromedial zone in the axial plane. Conclusion: Condyle remodelling is noted to be positive and not detrimental following VSSO. The positive remodelling effect remains stable regardless of the amount of VSSO setback. / published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

published_or_final_version / Dentistry / Master / Master of Dental Surgery

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

Background Distraction osteogenesis (DO) was first applied on the human craniofacial skeleton in 1992 by McCarthy et al.1 who performed lengthening of the mandible in patients with hemifacial microsomia and Nager’s syndrome. Further advances in this field have since then led to the widespread use of this modality for the treatment of numerous congenital and acquired craniofacial skeletal anomalies. In 2001, a review by Swennen et al2 concluded that up to year 1999, this form of treatment was gaining intense popularity but that the main drawbacks included insufficient data on long term results and relapse. A systematic review of the last decade on functional outcomes and long term complications following distraction osteogenesis of the facial skeleton is presented. Methods A structured systematic literature search, with predefined inclusion and exclusion criteria from relevant computer databases and journals were performed. The journals were evaluated and critically appraised by 2 reviewers separately in 3 rounds. Papers were categorized according to the level of evidence, the quality of methodology and the specific field of functional outcomes and long term complications. Results were then categorized according to the type of distraction movements, ie maxillary advancement and mandibular lengthening. Results A total of 42 papers comprising of 16 studies for maxillary advancement and 26 studies for mandibular lengthening were included in this review. Maxillary advancement was found to be beneficial in patients with cleft maxillary hypoplasia in terms of achieving aesthetic outcome but the risk for velopharyngeal insufficiency remains uncertain. The achieved maxillary advancement was stable if performed on adult patients while a recurrence of midface retrusion was noted if DO was performed on growing patients. Overcorrection was recommended in these cases to an estimated value of 20-50%. Mandibular lengthening was 99% successful in relieving respiratory obstruction in patients with isolated Pierre Robin Sequence (PRS) or syndromic micrognathic infants preventing the need for tracheostomy in the long term, and in 89% successfully decannulating infants with pre-existing tracheostomy. However, feeding and growth outcomes after airway obstruction was relieved remain unknown due to lack of sufficient evidence. Unilateral mandibular DO was successful in achieving aesthetic symmetrical facial balance in patients with hemifacial microsomia however a total loss of corrected distraction length was noted by the end of growth period if DO was performed during growth. Conclusions DO achieved stable results in terms of lengthening the maxilla and mandible but was also noted to cause restricted growth potential of the distracted bone. Hence, the benefits of performing DO during active growth should be weighed against the likely need for a second surgery due to a growth deficit of distracted bone and future surrounding bone growth. However DO in adults remains an alternative to conventional orthognathic surgery and choice of treatment should be patient centred. / published_or_final_version / Dental Surgery / Master / Master of Dental Surgery

published_or_final_version / Dental Surgery / Master / Master of Dental Surgery