Stability of the mandible after advancement and use of dental plus skeletal maxillomandibular fixation: an experimental investigation in Macaca mulatta

This study examined short-term stability of the mandible following advancement surgery and the use of skeletal suspension wires plus dental maxillomandibular fixation. Twenty-four adult female Macaca mulatta underwent bilateral sagittal ramus osteotomy and advancement of approximately 6 mm. All animals had dental maxillomandibular fixation secured by bonding the upper and lower teeth together with an orthodontic composite resin. In half of the animals, the use of circummandibular wires connected to pyriform aperture wires were additionally applied. Tantalum bone markers were placed and cephalograms analyzed during the first six postoperative weeks to evaluate skeletal stability. A statistically significant mean horizontal relapse at the mandibular symphysis occurred in the group without the skeletal wires, whereas no relapse occurred in the group with the skeletal wires. A significant difference in the vertical displacement of the anterior mandible occurred, with an inferior movement of the symphysis in the group without skeletal wires, and a superior movement of the symphysis in the group with skeletal wires. The results of this study indicate that the use of skeletal suspension wires is advantageous in the prevention of horizontal and vertical skeletal relapse.     

Stability of the mandible following advancement: a comparison of three postsurgical fixation techniques

This study examines short-term stability of the mandible following mandibular advancement surgery by means of three standard techniques of postsurgical fixation. Twenty-two adult female rhesus monkeys (Macaca mulatta) underwent sagittal ramus advancement osteotomy of approximately 4 to 6 mm. Six animals had dental maxillomandibular fixation alone. Six animals had dental plus skeletal maxillomandibular fixation with circummandibular wires connected to pyriform aperture wires. Ten animals had rigid internal fixation with bicortical bone screws between the proximal and distal segments without maxillomandibular fixation. Radiographic cephalograms with the aid of tantalum bone markers and dental amalgams were analyzed during the first 6 postoperative weeks to evaluate skeletal and dental stability. Rigid internal fixation and the use of dental plus skeletal maxillomandibular fixation were both equally effective in the prevention of postsurgical relapse. However, in the animals in which only dental maxillomandibular fixation was used, statistically significant changes (relapse) occurred when compared with either of the other groups.     

Stability of extraoral vertical ramus osteotomy: plate fixation versus maxillomandibular/skeletal suspension wire fixation

The objective of this cephalometric study was to evaluate skeletal stability and time course of postoperative changes in 2 groups of mandibular prognathism patients following extraoral oblique vertical ramus osteotomy (VRO). One group (n = 22) received maxillomandibular fixation and skeletal suspension wires (MMF group) for a period of 8 weeks. In the other group (n = 22), the segments were rigidly fixed with plates and the patients were allowed to function immediately after surgery. Lateral cephalograms were taken on 5 occasions: immediately presurgical, immediately postsurgical, 8 weeks postsurgical, 6 months postsurgical, and 1 year postsurgical. During the first 8 weeks after surgery, the MMF group demonstrated posterior movement of the mandible, with an increase in mandibular plane angle, shortening of the rami, and dental compensations. Upon release of MMF and skeletal suspension wiring, a small anterior relapse tendency was observed, but the net setback 1 year after surgery was still greater than the actual surgical setback. In the plate fixation group, postoperative changes were mainly in the form of a small anterior relapse tendency in the range of 10% of the surgical setback. The results indicate that the use of plate fixation with VRO, while eliminating the inconvenience for the patient of several weeks of MMF and preventing the early side effects observed in the MMF group, also resulted in a more predictable surgical procedure, with excellent stability 1 year after surgery.     

Effects of wire and miniplate fixation on mandibular stability and TMJ symptoms following orthognathic surgery

The effects of wire and miniplate fixations on mandibular stability and temporomandibular joint (TMJ) symptoms were analyzed in 145 patients in whom mandibular prognathism had been corrected by the bilateral sagittal split osteotomy (BSSO). The subjects were divided into two groups based on the method of fixation. Group I consisted of 105 patients treated with intraosseous wiring and group II consisted of 40 patients treated with titanium miniplates. The mean maxillomandibular fixation periods for groups I and II were 48 days and 23 days, respectively. Lateral cephalograms were taken immediately before surgery, within a week after surgery, and at least a year after surgery. Changes in the positions of the incisal edge of the lower central incisors, point B, pogonion, and menton were examined. TMJs were examined clinically for pain, sounds, movements, and limitations before treatment and at least a year after surgery. In both groups, the mean of the horizontal relapses was correlated to the magnitude of their surgical movements. In group II, the mean horizontal relapse was smaller, but not significantly more than that of group I. There was no statistical difference in the pre‐ and postoperative incidence of TMJ signs and symptoms between the two groups. It can be concluded that miniplate fixation for the BSSO procedure has the advantages of shortening the maxillomandibular fixation period and maintaining the postoperative stability of the mandible without causing adverse effects on the TMJ.     

Stability of simultaneous maxillary intrusion and mandibular advancement: A comparison of rigid and nonrigid fixation techniques

This study examines the short-term stability of bimaxillary surgery following Le Fort I impaction with simultaneous bilateral sagittal split osteotomies and mandibular advancement using two standard techniques of postsurgical fixation. Fifteen adults had skeletal plus dental maxillomandibular fixation, and fifteen adults had rigid internal fixation using bone plates in the maxilla and bicortical bone screws between the proximal and distal segments in the mandible. The group with rigid internal fixation did not undergo maxillomandibular fixation. Radiographic cephalograms were analyzed during the postsurgical period to evaluate skeletal and dental stability. There was no statistical difference in postsurgical stability with rigid internal fixation or skeletal plus dental maxillomandibular fixation other than the vertical position of the maxillary molar; the skeletal plus dental maxillomandibular fixation group had a significant amount of postsurgical intrusion of the maxillary molar when compared with the rigid internal fixation group. Although the other measures showed no statistically significant difference between the experimental groups, the amount of variability in postsurgical stability in the group with skeletal plus dental maxillomandibular fixation was greater than that found in the group with rigid internal fixation.     

Superior repositioning of the maxilla combined with mandibular advancement: mandibular RIF improves stability.

Postsurgical changes in 24 patients who had rigid internal fixation (RIF) of the mandible with screws after combined superior repositioning of the maxilla and mandibular advancement were compared with 53 patients who underwent the same surgery but who had intraosseous wire fixation, skeletal suspension wires, and 8 weeks of maxillomandibular fixation (MMF). During the first 8 weeks after surgery, the mean posterior relapse of the mandible was greater in the MMF group than in the RIF group (for example, -1.1 mm versus 0.15 mm at B point), and the percentage of patients with clinically significant vertical and horizontal changes was greater in the MMF group. By 1 year, there had been slight additional mean relapse in the MMF group (-1.5 mm net relapse at B point, with 42% of the patients showing 2 mm or more relapse). In the RIF group, the mandible was more likely to be repositioned forward than posteriorly (net mean change at B point, 0.7 mm forward; 33% had 2 mm or more forward movement). In the RIF group, all but one of the patients (96%) were judged to have an excellent clinical result; in the MMF group, the corresponding figure was 60%.     

Stability of skeletal class III malocclusion after combined maxillary and mandibular procedures: rigid internal fixation versus wire osteosynthesis of the mandible.

PURPOSE: The aim of this study was to evaluate skeletal stability after double-jaw surgery for correction of skeletal Class III malocclusion to assess whether there were any differences between wire and rigid fixation of the mandible. PATIENTS AND METHODS: Thirty-seven Class III patients had Le Fort I osteotomy stabilized with plate and screws for maxillary advancement. Bilateral sagittal split osteotomy for mandibular setback was stabilized with wire osteosynthesis and maxillomandibular fixation for 6 weeks in 20 patients (group 1) and with rigid internal fixation in 17 patients (group 2). Lateral cephalograms were taken before surgery, immediately after surgery, 8 weeks after surgery, and 1 year after surgery. RESULTS: Before surgery, both groups were balanced with respect to linear and angular measurements of craniofacial morphology. One year after surgery, maxillary sagittal stability was excellent in both groups, and bilateral sagittal split osteotomy accounted for most of the total horizontal relapse observed. In group 1, significant correlations were found between maxillary advancement and relapse at the posterior maxilla and between mandibular setback and postoperative counterclockwise rotation of the ramus and mandibular relapse. In group 2, significant correlations were found between mandibular setback and intraoperative clockwise rotation of the ramus and between mandibular setback and postoperative counterclockwise rotation of the ramus and mandibular relapse. No significant differences in postoperative skeletal and dental stability between groups were observed except for maxillary posterior vertical position. CONCLUSIONS: Surgical correction of Class III malocclusion after combined maxillary and mandibular procedures appears to be a fairly stable procedure independent of the type of fixation used to stabilize the mandible.     

Anterior skeletal fixation as an adjunct to oblique sliding osteotomy of the mandibular ramus. A cephalometric study

Positional changes of the mandible and upper and lower incisors were studied by means of cephalometric analysis after oblique sliding osteotomy for the correction of mandibular prognathism. In addition to intermaxillary fixation, skeletal fixation between the anterior nasal spine and the chin was used. The patients were followed up for 18 months after surgery. During the fixation period no increase in anterior facial height was observed and at 18 months this had decreased by 2.2 mm. Nevertheless, there was an increase in the mandibular plane angle by 3.8 degrees which mainly occurred during the fixation period. The posterior facial height decreased by 4.0 mm. As to the changes of the incisors these varied between individuals, but the mean values were small. Anterior skeletal fixation prevented increase in anterior facial height and seemed to limit the posterior shortening of the mandible and the extrusion of the mandibular incisors. However, the benefits remained rather limited.     

The stability of facial osteotomies. 4. Maxillary and mandibular (with or without chin) advancement with rigid internal fixation

The short-term (6 weeks postoperative) and long-term (12 months postoperative) horizontal skeletal stability of combined maxillary and mandibular advancement was evaluated by cephalometric analysis of 15 patients.
The mean horizontal advancement of the maxilla was 5.84 mm. Six weeks later a mean horizontal relapse of 0.03 mm (0.05%) was identified. The mean horizontal relapse at long-term follow-up was 0.59 mm (10.1%).
The mean horizontal advancement of the mandible was 12.35 mm at menton and 12.65 mm at pogonion. At 6 weeks, mean horizontal relapse, respectively at the above landmarks, was 0.11 mm and 0.21 mm (1.3%). The mean horizontal relapse at long-term follow-up was 2.19 mm and 1.98 mm (16.6%) respectively for the same landmarks.
Subjectively and objectively, improvements were seen in facial aesthetics and dental occlusion. The results indicate that rigid fixation of osteotomies undertaken to correct 'horizontal facial deficiency' is a surgically predictable and relatively stable procedure when reviewed up to 12 months after surgery.     

Skeletal stability after mandibular advancement with rigid versus wire fixation.

PURPOSE: This study examined the stability of skeletal changes after mandibular advancement surgery with rigid or wire fixation up to 2 years postoperatively. PATIENTS AND METHODS: Subjects for this multisite, prospective, clinical trial received rigid (n = 78) or wire (n = 49) fixation. The rigid cases were fixed with three 2-mm bicortical position screws and 1 to 2 weeks of skeletal maxillomandibular fixation with elastics, and the wire fixation subjects were fixed with inferior border wires and had 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric radiographs were obtained before orthodontics, immediately before surgery, and at 1 week, 8 weeks, 6 months, 1 year, and 2 years after surgery. Linear cephalometric changes were referenced to a cranial base coordinate system. RESULTS: Before surgery, both groups were balanced with respect to linear and angular measurements of craniofacial morphology. Mean anterior sagittal advancement of the mandibular symphysis was 4.92 +/3.01 mm in the rigid group and 5.11 +/- 3.09 mm in the wire group, and the inferior vertical displacement was 3.37 +/- 2.44 in the rigid group and 2.85 +/- 1.78 in the wire group. The vertical changes were similar in both groups. Two years postsurgery, the wire group had 30% sagittal relapse of the mandibular symphysis, whereas there was no change in the rigid group (P < .001). Both groups experienced changes in the orientation and configuration of the mandible. CONCLUSIONS: Rigid fixation is a more stable method than wire fixation for maintaining mandibular advancement after sagittal split ramus osteotomy.     

Stability two years after mandibular advancement with and without suprahyoid myotomy: an experimental study

Ten adult rhesus monkeys underwent mandibular advancement surgery of 4-6 mm with and without suprahyoid myotomy. Serial lateral cephalograms using radiopaque bone markers were obtained during maxillomandibular fixation and for 96 weeks after release of fixation to determine the effects of suprahyoid myotomy on short-term and long-term adaptations in the advanced mandible. The non-myotomy group exhibited a significant reduction in the length of the advanced mandible (relapse) during the fixation period but showed no significant change in mandibular length after release of fixation. The myotomy group exhibited no relapse during the fixation period and after release of fixation displayed a slight but statistically significant increase in mandibular length. This supports the hypothesis that stretching of the suprahyoid musculature as a result of mandibular advancement surgery is a major factor leading to skeletal relapse.     

Rigid versus wire fixation for mandibular advancement: Skeletal and dental changes after 5 years

The bilateral sagittal split osteotomy (BSSO) is the most common surgical procedure for the correction of mandibular retrognathism. Commonly, the proximal and distal segments are fixated together with either wire or rigid screws or plates. The purpose of this study was to compare long-term (5 years) skeletal and dental changes between wire and rigid fixation after BSSO. In this multisite, prospective, randomized clinical trial, the rigid fixation group received three 2-mm bicortical position screws, and the wire fixation group received inferior border wires and 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric films were obtained 2 weeks before surgery and at 1 week, 8 weeks, 6 months, 1 year, 2 years, and 5 years after surgery. Linear cephalometric changes were referenced to a cranial base coordinate system. Before surgery, both groups were comparable with respect to linear and angular measurements of craniofacial morphology. Both groups underwent similar surgical changes. Skeletal and dental movements occurred in both groups throughout the study period. Five years after surgery, the wire group had 2.2 mm (42%) of sagittal skeletal relapse, while the rigid group remained unchanged from immediately postsurgery. Surprisingly, at 5 years, both groups had similar changes in overbite and overjet. This was attributed to dental changes in the maxillary and mandibular incisors. Although rigid fixation is more stable than wire fixation for maintaining the skeletal advancement after a BSSO, the incisor changes made the resultant occlusions of the 2 groups indistinguishable.     

Stability of orthodontic-maxillofacial surgical treatment of anterior open bite deformities]

A sample of 267 patients with maxillary hyperplasia, a Class I or Class II occlusion and anterior open bite, collected from three different institutions, was analysed regarding stability after Le Fort I intrusion osteotomies or bimaxillary osteotomies. Skeletal and dento-alveolar stability of the maxilla, postional changes of the mandible and of incisors were evaluated on cephalometric radiographs. The stability of maxillary arch dimensions after correction of the open bite is measured on dental casts. Patients with anterior open bite, treated with a Le Fort I osteotomy in one-piece or in multi-segments, with or without bilateral sagittal split osteotomy exhibited good skeletal stability of the maxilla. Rigid internal fixation showed better maxillary and mandibular stability than intraosseous wire fixation. Considerable relapse of transverse dimensions, however, was measured after orthodontic and surgical expansion. The mean overbite at the 69 months follow-up was 1.24 mm and lacking of overlap between opposing incisors was present in 19%.     

Comparison of relapse in bilateral sagittal split osteotomies for mandibular advancement: rigid internal fixation (screws) versus inferior border wiring with anterior skeletal fixation

A retrospective study of 28 patients treated by bilateral sagittal split ramus osteotomies for mandibular advancement and stabilized by two different methods of fixation was performed. Fourteen patients received rigid fixation, and 14 patients had inferior border wiring with anterior skeletal fixation. The postoperative and long-term cephalograms (greater than 6 months) were analyzed in a horizontal and vertical direction for relapse. In the horizontal direction, the rigid group experienced a 1.5% relapse in point B and a 3.2% relapse in pogonion. In the vertical direction, the rigid group experienced a 4% relapse in point B and a 9% relapse in pogonion, while the wire osteosynthesis group had a 13% relapse in point B and a 6% relapse in pogonion. These results support the belief that rigid fixation is more stable than is wire osteosynthesis and that it helps prevent relapse in the long-term results.     

A comparative study of skeletal and dental stability between rigid and wire fixation for mandibular advancement

This study examined the skeletal and dental stability after mandibular advancement surgery with rigid or wire fixation for up to 2 years after the surgery. Subjects for this multisite, prospective, randomized, clinical trial were assigned to receive rigid (n = 64) or wire (n = 63) fixation. The rigid cases received three 2-mm bicortical position screws bilaterally and elastics; the wire fixation subjects received inferior border wires and 6 weeks of skeletal maxillomandibular fixation with 24-gauge wires. Cephalometric films were obtained before surgery, and at 1 week, 8 weeks, 6 months, 1 year, and 2 years after surgery. Skeletal and dental changes were analyzed using the Johnston's analysis. Before surgery both groups were balanced with respect to linear and angular measurements of craniofacial morphology. Mean anterior advancement of the mandibular symphasis was 5.5 mm (SD, 3.2) in the rigid group and 5.6 mm (SD, 3.0) in the wire group. Two years after surgery, mandibular symphasis was unchanged in the rigid group, whereas the wire group had 26% of sagittal relapse. Dental compensation occurred to maintain the corrected occlusion, with the mandibular incisor moving forward in the wire group and posteriorly in the rigid group. However, at 2 years after surgery, when most subjects were without braces, the overjet and molar discrepancy had relapsed similarly in both groups.     

Adaptation of the suprahyoid muscle complex to large mandibular advancements

The purpose of this study was to provide quantitative data concerning the changes and adaptations that take place within the suprahyoid complex to larger mandibular advancements. Mandibular advancement of 6.5 mm was performed on 12 adult rhesus monkeys. Six underwent maxillomandibular fixation (MMF) using the dentition, six underwent MMF using the dentition plus skeletal suspension wires. Mandibular position and changes in the length of the various anatomic regions of the suprahyoid complex were evaluated cephalometrically with the aid of radiopaque bone, muscle, and tendon markers implanted preoperatively. Relapse of the mandible in the dental MMF animals was 27% of the advancement, whereas there was none in the dental plus skeletal MMF group. Results of adaptations within the suprahyoid complex showed that 1) the suprahyoid complex was elongated slightly less than the mandible, and 2) the major adaptations (lengthening) occurred at the muscle-bone interface, the muscle-tendon interface, and within the belly of the anterior digastric muscle. On the basis of these results, it was concluded that adaptations within the suprahyoid complex to mandibular lengthening occur first at the connective tissue attachments of the muscle, and then within the muscle belly itself. The methods of dealing with the potentially distracting forces from the stretch within the suprahyoid complex are discussed.     

The skeletal stability after maxillo-mandibular osteotomy with a “physiological positioning strategy”

The aim of this study was to estimate skeletal and dental stability after maxillomandibular osteotomy with physiological positioning. Ten patients (7 men and 3 women) with skeletal mandibular prognathism were treated by conventional Le Fort I osteotomy for the maxilla and unfixed short lingual osteotomy for the mandible together with physiological positioning. We used cephalometric analysis to evaluate the skeletal and dental stability preoperatively, immediately after maxillomandibular osteotomy, and more than 1 year later. The immediately postoperative measurements for the SNA and the SN-palatal planes were 0.15^o (p = 0.67) and 1.0 ^o (p = 0.17), respectively. The positions of the anterior nasal spine, posterior nasal spine, and A point showed minimal changes 1 year postoperatively. The postoperative difference for SNB was 0.76 ^o (p = 0.04). Dental stability was apparent postoperatively. We conclude that reliable stability of both the maxilla and the mandible was achieved after maxillomandibular osteotomy with physiological positioning in patients with mandibular prognathism.     

Stability of simultaneous maxillary and mandibular osteotomy for treatment of class III malocclusion: an analysis of three-dimensional cephalograms.

PURPOSE: The current investigation was undertaken to study the three-dimensional (3-D) stability of simultaneous maxillary advancement and mandibular setback using rigid fixation. The study also aimed to analyse the factors involved in postsurgical relapse by evaluation of changes in various parameters. PATIENTS: Twenty-five cases were evaluated of simultaneous Le Fort I maxillary advancement and mandibular setback using rigid fixation. METHODS: Preoperative, immediate and 6-month postoperative skeletal and dental changes were analysed using 3-D cephalograms obtained from biplanar stereoradiography. Maxillary fixation screws were used as landmarks to evaluate postoperative stability. RESULTS: The mean maxillary advancement was 3.7 mm. Relapse in the sagittal, vertical, and transverse planes was not detectable in the maxilla (p > 0.05). However, for an average mandibular setback of 5.7 mm, mean mandibular relapse was 1.1 mm or 19.3% anteriorly (p < 0.05). Surgical or postsurgical skeletal changes in the maxilla had no detectable influence on mandibular relapse (p > 0.05). Vertical alterations of the facial skeleton achieved surgically predicted the mandibular relapse (R2 = 0.27, p < 0.05). CONCLUSION: Maxillary advancement and vertical changes of +/- 2 mm did not influence the postoperative stability of the mandible. Relapse of the mandible seems to be influenced mainly by the amount and direction of the surgical alteration of mandibular position.     

Cephalometric changes after long-termearly treatment with face mask and maxillary intraoral appliance therapy

This article reports on a retrospective study of 25 children (mean age, 4 years 2 months) exhibiting Class III malocclusions and anterior cross-bites who were treated with a face mask and a maxillary intraoral appliance. Cephalometric radiographs were taken for all treated patients at three intervals: before treatment (TO), after treatment (T1), and at posttreatment follow-up (T2). A control group consisted of 10 untreated Class III children (mean age, 3 years 11 months). Cephalometric radiographs were taken periodically for observation in this group. Paired t tests and independent t tests were performed to determine the significance of skeletal and dental changes related to treatment. Early therapy produced significant skeletal and dentoalveolar changes. The maxilla moved further forward in the treated group. Mandibular growth was similar in both treated and untreated groups. There was an improvement in the maxillomandibular relationship in the treated group. This was because of the proclination of the maxillary incisors and the retroclination of the mandibular incisors. Self-correction of the original anterior cross-bite in the untreated group occurred. Long-term follow-up revealed a decrease in overjet mainly caused by the proclination of the mandibular incisors. However, positive overjet was maintained throughout the study period. Despite some relapse, the treated group showed a net positive improvement in occlusion.     

Mandibular remodeling after bilateral sagittal split osteotomy for prognathism of the mandible.

PURPOSE: To describe the postoperative remodeling changes in the mandible after bilateral sagittal split osteotomy to correct mandibular prognathism. PATIENTS AND METHODS: Twenty patients who underwent bilateral sagittal split osteotomy for the correction of mandibular prognathism were studied for postoperative remodeling changes within the mandible. The 6-week, 1-year, and long-term postoperative cephalometric mandibular tracings of 12 patients were superimposed using the fixation wires as the stable reference points to demonstrate the specific locations of the intrabony remodeling. RESULTS: There was a general direction of remodeling at the condylion and gonion anteriorly and superiorly, while the B point and pogonion did not show much change in remodeling. At the condylion, 60% and 40% of the cases showed significant horizontal and vertical remodeling, respectively. At the gonion, 50% and 55% of the cases showed significant horizontal and vertical remodeling, respectively. No correlation was found between the remodeling changes at condylion and gonion and the surgical movement or relapse at B point and pogonion. There was a significant correlation between the observed horizontal relapse at gonion and the horizontal remodeling changes at this point showing that the postoperative displacement of this point is a result of both positional translocation and remodeling changes. CONCLUSION: The results of this study show that there are intrabony remodeling changes that occur in the mandible after sagittal split osteotomy and that these continue for a long period of time in some patients. This remodeling occurred more in the condylar and gonial areas, while the chin remained relatively stable.