Repositioning Of Maxilla Research Articles

Anterior open-bite malocclusion: stability of maxillary repositioning using rigid internal fixation

Abstract A retrospective cephalometric study was performed to investigate the stability of 37 non-growing anterior open-bite cases using mini-plate rigid fixation. The sample was divided into two groups: Group A: maxillary repositioning alone (17 cases) and Group B: bimaxillary surgery (20 cases). Tracings were performed pre-operatively (T1), immediately post-operatively (T2) and at a minimum of one year follow-up (T3) (12–90 months). In Group A, the maxilla was advanced (3.8 +_ 2.8 mm, p < 0.01) and superiorly repositioned at PNS (2.8 +_2.3 mm, p < 0.001). In Group B, the maxilla was advanced (3.5 +_ 3.0 mm, p < 0.01) and superiorly repositioned at PNS (3.7 +_ 1.8 mm, p <0.001); and the mandible (11.7 +_ 3.8 mm, p < 0.001), with no significant change in the vertical plane (p > 0.05). Late relapse due to condylar remodelling or resorption was found as a cause of large horizontal relapse (8.0 < x < 14.0 mm) in three cases (15%), the amount being associated with the amount of operative advancement (r = 0.7, r-sq = 40%, p < 0.01). It was concluded that the correction of anterior open bite by posterior repositioning of the maxilla using rigid fixation is a stable procedure during the follow-up period, and that in bimaxillary cases, post-operative stability depends largely on the stability of the mandibular advancement, which in turn relates to the amounts of advancement, the pre-operative anterior open bite and the mandibular plane angle.

Anatomic guidelines for the placement of external references for maxillary reposition.

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Anatomic guidelines for the placement of external references for maxillary repositioning

Objective. External reference points, particularly Kirschner pins (K-wire), placed in the region of the nasion have been shown to improve the accuracy of maxillary vertical repositioning. Although no complications associated with this technique have been reported, there is a potential for injury to the anterior cranial fossa or frontal sinus. The purpose of this study was to measure the shortest distance from the nasion to the anterior cranial fossa and from the nasion to the frontal sinus. These measurements were used to establish anatomic guidelines governing safe placement of external reference point pins. Study design. Twenty-seven cadaver heads were sectioned in the midsagittal plane for gross study. Using a Boley gauge, two specific measures were obtained: (1) distance from deepest depression of nasion to the most anterior and inferior projection of the anterior cranial fossa, and (2) distance from nasion to the most inferior aspect of the frontal sinus. All measurements were made in the midsagittal plane. Results. The average distance from nasion to anterior cranial fossa was 16.9 mm (range 13.0 to 20.0 mm) and the smallest distance, 13.0 mm, was seen in two specimens. The average distance from nasion to the frontal sinus was 6.2 mm (range 2.0 to 10.0 mm) and the smallest distance, 2.0 mm, was seen in three specimens. Conclusion. Based on our findings, we recommend the following: (1) place pin to a depth of no more than 8 mm into bone, (2) place pin 5 to 10 mm inferior to soft tissue nasion, and (3) place pin in an anterosuperior to posteroinferior direction (i.e., roughly perpendicular to the nasal dorsum). When these anatomic guidelines are followed, one would expect minimal morbidity associated with the placement of ERP pins.

Maxillary stability of combined maxillary superior repositioning and mandibular advancement using rigid fixation

Maxillary stability of combined maxillary superior repositioning and mandibular advancement using rigid fixation

上下顎移動術を受けた下顎前突症患者における顎顔面形態の術後変化

The purpose of this study was to investigate the long-term changes of craniofacial morphology in mandibular prognathism patients treated with two-jaw surgery and to evaluate the stability after surgery. Lateral cephalograms of seven patients (two males and five females) studied for more than two years after surgery, were analyzed for evaluation of craniofacial changes. The materials were obtained at eight stages between the initial and the latest examinations. Dentofacial changes were analyzed and compared between the stages.The results were as follows:1. The maxilla was moved forward and downward by surgery (average; anteriorly 4.2mm, inferiorly 3.3mm). Anteroposteriorly, excellent postoperative stability was achieved, although the maxilla slightly displaced posteriorly during intermaxillary fixation. The maxilla was displaced superiorly 1.5mm on average between immediately and 3 months after surgery. However, the vertical change of the maxilla was minimum after 6 months.2. The mandible was moved backward 12.9mm on average after surgery. Postoperative stability was achieved, while the mandible was displaced forward 1.4mm on average between removal of intermaxillary fixation and 6 months after surgery. A significant negative correlation was found between the amounts of mandibular setback and forward displacement.3. The maxillary and mandibular incisors moved lingually during intermaxillary fixation and then tended to be slightly inclined labially. After one year, no obvious changes in inclination of upper and lower incisors were observed in most cases.4. Appropriate overjet has been maintained, while overbite decreased slightly in some cases after surgery. At the latest examination, an acceptable occlusal relationship in the anterior region was maintained in all cases.From these findings, it was suggested that long-term craniofacial stability and acceptable occlusal relationship in the anterior region were obtained in most cases by two-jaw surgery. On the other hand, vertical relapse of the maxilla occurred immediately after inferior maxillary repositioning. Therefore, it was suggested that an integrated treatment planning be established to prevent vertical relapse of the maxilla.

Influence of DNA contents in squamous cell carcinoma of the oral cavity on prognosis

Lateral head films taken immediately pre-operatively and at least 6 months postoperatively were analysed in 99 selected orthognathic surgery patients to study soft and hard tissue ratios in relation to lip seal creation. The patients were grouped according to the osseous correction carried out.In maxillary advancement patients, the overall position of stomion superius was difficult to predict when important horizontal and vertical movements had been made. The vertical movement of stomion superius was 30% of that seen at the anterior palate point, and 25% of that at the upper incisal point, when the main vector of maxillary repositioning was vertical (either intrusion or extrusion).There was a weak linear correlation between mandibular advancement at pogonion and vertical changes at stomion inferius. The correlation increased if vertical movement at menton and mentolabial angle were added as independent variables. Good linear correlations between vertical changes at stomion inferius and vertical changes at lower incisal point and menton were observed in mandibular set-back surgery. In mandibular autorotation, the best linear correlation with single predictors was found between vertical changes at stomion inferius and those at menton (about 80% + 1 mm upward movement), and vertical changes at stomion inferius and horizontal changes at lower incisal point.Vertical changes at stomion inferius were mainly determined by vertical changes at menton in genioplasties, the change at stomion inferius being 40% of that at menton. The horizontal component at pogonion had almost no influence. In combined genioplasty and Le Fort I procedures, the vertical changes at stomion inferius were 50% of those at menton + 1 mm upward movement, this difference being due to mandibular autorotation.

Soft tissue cervicomental changes after the orthognathic surgery

Our ability to predict the outcome of any orthognathic procedure relies on the surgeon's ability to accurately reproduce the desired skeletal movements and on our understanding of the soft tissue changes associated with those movements. The purpose of this retrospective study was to evaluate the surgical accuracy of maxillary repositioning by comparing the objectives obtained from cephalometric prediction tracings with the actual skeletal changes achieved during maxillary and maxillomandibular procedures. The sample consisted of 46 patients from the files of 1 orthodontist. Presurgical and immediately postsurgical cephalometric radiographs were digitized, and the original surgical prediction was reproduced with Dentofacial Planner (Dentofacial Software, Toronto, Ontario, Canada) software. Vertical and horizontal measurements to several skeletal landmarks were used to assess the differences between the predicted maxillary position and the actual maxillary postsurgical position. Statistical differences were found for some measurements, particularly those related to the vertical placement of the posterior maxilla. Three variables were evaluated for their effect on the surgical discrepancies. The 2 surgeons with the most patients were evaluated and found to have differences in the direction of discrepancies but not the amount (absolute values). Significant differences were also found when evaluating surgical complexity (single-jaw vs bimaxillary procedures) and the direction of movement (impaction vs advancement) in direction only. To assess the overall fit of individual predictions, we calculated an average discrepancy for each patient; 80% of the actual results fell within 2 mm of the prediction, and 43% fell within 1 mm of the prediction. (Am J Orthod Dentofacial Orthop 2002;122:142-54)

Creating lip seal by maxillo-facial osteotomies: A retrospective cephalometric study

Lateral head films taken immediately pre-operatively and at least 6 months postoperatively were analysed in 99 selected orthognathic surgery patients to study soft and hard tissue ratios in relation to lip seal creation. The patients were grouped according to the osseous correction carried out. In maxillary advancement patients, the overall position of stomion superius was difficult to predict when important horizontal and vertical movements had been made. The vertical movement of stomion superius was 30% of that seen at the anterior palate point, and 25% of that at the upper incisal point, when the main vector of maxillary repositioning was vertical (either intrusion or extrusion). There was a weak linear correlation between mandibular advancement at pogonion and vertical changes at stomion inferius. The correlation increased if vertical movement at menton and mentolabial angle were added as independent variables. Good linear correlations between vertical changes at stomion inferius and vertical changes at lower incisal point and menton were observed in mandibular set-back surgery. In mandibular autorotation, the best linear correlation with single predictors was found between vertical changes at stomion inferius and those at menton (about 80% + 1 mm upward movement), and vertical changes at stomion inferius and horizontal changes at lower incisal point. Vertical changes at stomion inferius were mainly determined by vertical changes at menton in genioplasties, the change at stomion inferius being 40% of that at menton. The horizontal component at pogonion had almost no influence. In combined genioplasty and Le Fort I procedures, the vertical changes at stomion inferius were 50% of those at menton + 1 mm upward movement, this difference being due to mandibular autorotation.

Face mask therapy of preadolescents with unilateral cleft lip and palate.

This study evaluates 21 children treated with maxillary expansion and protraction appliances for skeletal discrepancies associated with unilateral cleft lip and palate (UCLP). The subjects were treated by the same orthodontist, using the same techniques and appliances. Mean pre- and posttreatment ages were 7.3 and 8.7 years, respectively. Each child was matched by ethnicity, sex, age, and the SN/MP angle to an untreated (non UCLP) control. Stable cranial and cranial base reference structures were used for superimposing serial cephalograms. The results showed definite protraction of the maxilla for the UCLP group. The posterior maxilla of the UCLP group underwent anterior displacement; the posterior maxilla of the control group displayed posterior growth changes. The maxillary incisor tips of the UCLP group demonstrated greater anterior movement than expected for untreated controls. Vertical changes of the maxilla showed no significant group differences. The mandible of the UCLP group was rotated inferiorly and posteriorly; the control group showed inferior/anterior changes. The lower incisor of the UCLP and control groups remained stable and moved anteriorly, respectively. The UCLP group showed significantly greater inferior movements of the anterior mandible than the control group. We concluded that differences between the control and UCLP groups are primarily related to mandibular clockwise rotation and secondarily to anterior maxillary repositioning.

Long-term stability after inferior maxillary repositioning by miniplate fixation

Nineteen patients underwent Le Fort I osteotomy and inferior maxillary repositioning. Miniplates were used to maintain the maxilla in its new position. The patients were followed from 12 to 58 months, postoperatively. Fourteen patients were considered to be stable over the long term. Five patients had a long-term relapse of more than 30%. A tendency towards greater relapse was seen in patients with more than 5 mm inferior repositioning, and in patients who had concurrent segmental osteotomies of the maxilla. In spite of the use of miniplates, there continues to be an element of unpredictability with regard to vertical relapse after inferior maxillary repositioning, and this may be related to soft-tissue influences.

An assessment of the predictability of maxillary repositioning

The purpose of this investigation was to compare our ability to perform the surgery that is planned in the prediction tracing and model surgery when using the mandible as a guide to maxillary repositioning, using internal and external reference points to establish the vertical dimension at the time of surgery. A total of 146 consecutive patients who underwent maxillary repositioning by means of Le Fort I osteotomy were selected. In all patients the unoperated mandible was used to provide anteroposterior and transverse maxillary position. In 100 patients, measurements made on the lateral wall of the maxilla (internal reference points — IRP) were used to determine the maxillary vertical dimension. In 46 patients, the vertical dimension was established by measuring between a Kirschner wire in the nasal bridge and a maxillary incisor (external reference points — ERP). Comparison between the predicted and actual change in the position of the incisor was calculated. Statistical analysis showed that there were significant differences between the predicted and actual change in vertical and horizontal position of the incisor (p < 0.0001) for both experimental groups. However, there was a significant difference between the 2 experimental groups (p < 0.001) for the accuracy of vertical repositioning. The use of an external reference point proved to be a more accurate method for vertical maxillary repositioning. The results of this investigation indicate that the ability to determine vertical repositioning of the maxilla with internal reference lines is limited.

Long-term soft tissue response to LeFort I maxillary superior repositioning.

The purpose of this study was to compare short-term (approximately 12 months postoperatively) and long-term (24 to 81 months postoperatively) records of 36 patients who underwent superior repositioning of the maxilla via LeFort 1 osteotomies. The parameters of measurement were set up to analyze the net response of the soft tissues of the face to superior repositioning of the maxilla. The results of this study show that soft-tissue changes associated with maxillary impaction are minimal and that no significant differences exist between twelve-month records and five-year records.

Porous block hydroxyapatite in orthognathic surgery.

Seventy-six nonconsecutive patients undergoing orthognathic surgery, in whom blocks of porous hydroxyapatite were implanted into osteotomy gaps in lieu of autogenous bone grafts, are the subjects of this report. Surgical procedures include inferior maxillary repositioning (10 patients), maxillary advancement (24 patients), transverse maxillary expansions (17 patients) and inferior repositioning of the chin (25 patients). A total of 140 anatomic sites were implanted. Eleven patients later consented to open biopsy of the implant material at a mean 10.2 months following implantation. At the time of follow-up, mean 16.3 months, excellent osseous stability was observed. Three patients developed complications relative to the presence of the implant. Twenty-one of 24 biopsy specimens demonstrated an osseous union of implant to bone with osseous deposition within the implant pores. Radiographic follow-up revealed implant blocks to maintain their volume with no change in density or discreteness. The biological behavior and biomechanical properties of porous block hydroxyapatite are discussed. These implant characteristics make it a feasible bone graft substitute in orthognathic surgery and justify its continued use in this context.

Planning and control of vertical dimension in Le Fort I osteotomies

Depending on the different anatomy of the soft and hard tissues, concavity or convexity of the face, measurements of inferior or superior repositioning of the maxilla may be less predictable when using only the osteotomy site for this calculation. A more reliable method would be to measure the distance from a bone mark in the forehead to the incisor edges. This method has been practiced by our clinic during the past five years. The method is thought to offer a more accurate estimation of the position of the upper anterior teeth in relation to the lip, although one must anticipate a certain degree of postoperative relapse especially concerning inferior repositioning. In order to evaluate the accuracy of our method, a comparison has been made of the calculated vertical repositioning and the surgical results in two groups. In group I (12 individuals) conventional estimation of maxillary repositioning in the osteotomy line was made; in group II (12 individuals) measurements were made from a bone mark on the forehead to the incisor edges. A satisfying correlation was found between calculated and achieved results in both groups. In comparison between calculated and immediate postoperative measurements the results showed no statistically significant difference between the two methods.

An assessment of the predictability of maxillary surgery

The purpose of this investigation was to determine the ability to perform the surgery that is planned based on the prediction tracing and model surgery when using the mandible as a guide to maxillary repositioning and internal reference points to establish the vertical dimension at the time of surgery. One hundred consecutive patients who underwent maxillary repositioning by means of Le Fort I osteotomy were selected. In all patients the unoperated mandible was used to provide anteroposterior and transverse maxillary position and measurements made on the lateral wall of the maxilla (internal reference points, IRP) to determine the maxillary vertical dimension. Tracings of all cranial structures were made of the preoperative cephalograms and superimposed on the postoperative cephalogram and on the prediction tracing using cranial base structures. Points were digitized to compare the preoperative, postoperative, and predicted position of the maxillary central incisor and first molar of each patient by computer. Comparison between the predicted and actual change in the position of the incisor and molar was calculated. Statistical analysis showed that there were significant differences between the predicted and actual change in vertical and horizontal position of both the incisor and the molar ( P < .0001). The results of this investigation indicate that the ability to determine vertical repositioning of the maxilla with internal reference lines is limited.

Condylar position in superior maxillary repositioning and its effect on the temporomandibular joint

Twenty-nine patients (58 joints) were tomographically evaluated for condylar position and assessed for temporomandibular joint function following superior maxillary repositioning with mandibular autorotation. Seventy-six percent of the condyles showed postoperative posterior repositioning, whereas tomographic measurement of the joint spaces revealed significant posterior condylar position ( P < .01) relative to the preoperative position. Pre- and postoperative comparative values of condylar displacement from absolute concentricity based on the Pullinger index also showed posterior condylar repositioning postoperatively ( P < .001). However, there was no correlation between condylar position and the presence of temporomandibular joint symptoms in both the asymptomatic and symptomatic groups.

Definitive Surgical Correction of Vertical Maxillary Deficiency

Inferior repositioning of the maxilla to correct vertical maxillary deficiency has been associated with variable degrees of instability and subsequent relapse. Resorption of bone-graft material has been incriminated as the primary cause of postoperative instability. This paper reports on nine patients who have undergone inferior maxillary repositioning resulting in no residual bone contact between the down-fractured maxilla and superior midface. Mean inferior maxillary repositioning was 6.2 mm. Osteotomy gaps were implanted with porous block hydroxyapatite (Interpore 200), and maxillae were rigidly fixed in position with miniplates. No postoperative intermaxillary fixation was utilized in any patient. Follow-up ranged from 11 to 28 months, with a mean of 19.6 months. Cephalometric analyses at follow-up revealed excellent stability of the repositioned maxillae, with a mean vertical relapse of 4.3 percent. No complications were associated with this procedure. The biomechanical rationale contributing to the success of this operative technique is discussed.

Facial growth subsequent to Le Fort I osteotomies in adolescent monkeys

The study goal was to assess qualitatively and quantitatively the craniofacial adaptations following total maxillary osteotomy with and without mandibular autorotation. Six adolescent female Macaca fascicularis monkeys were randomly divided into two surgical groups, and eight others served control. Prior to surgery, metallic implants were inserted in the anterior part of the cranial base, on opposite sides of craniofacial sutures, and in multiple sites of the maxilla and mandible. Group I animals underwent a Le Fort I advancement of 4 mm, while Group II animals had a 5-mm advancement and a 2.5-mm impaction. Lateral cephalometric headfilms were taken at monthly intervals for a total follow-up of 12 months after surgery. At least two cephalograms were taken on each occasion, one with the teeth in occlusion and the other with the mouth wide open. The latter was used to ascertain accurately the outline of the mandibular condyle. Cephalometric superimposition methods were used to quantify the growth changes. The findings indicated that the growth changes in the maxilla and mandible were related to the extent of injury caused by maxillary surgery. The largest increments and rates of growth were observed respectively in the control animals, Group I animals (anterior maxillary repositioning), and Group II animals (anterior and superior maxillary repositioning). The most interesting finding was that mandibular growth pattern followed maxillary growth pattern in both experimental groups, and the immediate postsurgical occlusion in Class II molar relationship was maintained with increased overjet in both experimental groups throughout the postsurgical observation period.

Three-dimensional changes of upper lip and nose following maxillary superior repositioning

Three-dimensional changes of upper lip and nose following maxillary superior repositioning

Intraoperative measurement of maxillary repositioning

Intraoperative measurement of maxillary repositioning