Stability and predictability of orthognathic surgery

Skeletal stability after maxillary distraction osteogenesis or conventional Le Fort I osteotomy in patients with cleft lip and palate: A superimposition-based cephalometric analysis

PURPOSE

The aim was to assess skeletal stability after maxillary advancement using either distraction osteogenesis (DO) or conventional Le Fort I osteotomy (CO) in patients with cleft lip and palate (CLP) or cleft palate (CP) utilising a new superimposition-based cephalometric method.

METHOD

This retrospective study included patients who were treated with DO (N = 12) or CO (N = 9). Sagittal and vertical changes after surgery, and skeletal stability at 18 months post-operatively were assessed with superimposition-based cephalometry, comparing lateral cephalograms performed pre-operatively (T0), post-operatively after CO or immediately after completed distraction in DO (T1), and at 18 months of follow-up (T2).

RESULTS

The mean sagittal movements from T0 to T2 in the DO and CO groups were 5.9 mm and 2.2 mm, respectively, with a skeletal relapse rate of 16% in the DO group and 15% in the CO group between T1 and T2. The vertical mean movement from T0 to T2 in the DO and CO groups was 2.8 mm and 2.0 mm, respectively, and the skeletal relapse rate between T1 and T2 was 36% in the DO group and 32% in the CO group.

CONCLUSION

Sagittal advancement of the maxilla was stable, in contrast to the vertical downward movement, which showed more-extensive relapse in both groups. Despite more-extensive maxillary advancement in the DO group, the rates of skeletal relapse were similar.

Soft-Tissue Response following Genioplasty Combined with Anterior Segmental Osteotomy

BACKGROUND

The authors' main aim was to analyze soft-tissue response of the chin following genioplasty with anterior segmental osteotomy, which enables optimal surgical planning of genioplasty.

METHODS

Sixty-two patients who underwent genioplasty with concomitant anterior segmental osteotomy were divided into three groups depending on the direction of pogonion (Pog) movement: G1 (without sagittal change), G2 (advancement genioplasty), and G3 (setback genioplasty). All genioplasties included height reduction. Hard- and soft-tissue measurements with cephalometry were performed at T1 (before surgery), T2 (after surgery), and T3 (after orthodontic treatment) for the analysis of sagittal and vertical changes. Correlation and regression analyses were conducted to analyze soft- to hard -tissue movement and soft-tissue thickness changes.

RESULTS

During the T1 to T2 period, the horizontal soft- to hard-tissue ratio at Pog was 0.85 in G2 and 0.80 in G3, and the vertical ratio at menton (Me) was 0.9 for all groups. The correlation coefficients were 0.64 (G2) and 0.83 (G3) at Pog and 0.9 (all), 0.85 (G1), 0.95 (G3) at Me. There was no significant correlation between initial soft-tissue thickness and soft-tissue response ratio. During the T2 to T3 period, no significant relapses were observed, which demonstrates the stability of anterior segmental osteotomy combined genioplasty.

CONCLUSIONS

Clinically and statistically significant soft-tissue responses were demonstrated at Pog and Me. The higher values in G3 in particular suggest that setback genioplasty with anterior segmental osteotomy is an effective treatment alternative to conventional two-jaw surgery in some patients with bimaxillary prognathism with macrogenia.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Three-dimensional evaluation of skeletal stability after surgery-first bimaxillary surgery for class III asymmetry in 70 consecutive patients

Background/purpose

Skeletal stability after orthognathic surgery is essential for positive treatment outcome. This study evaluated the stability of osteotomy segments after surgery-first bimaxillary surgery for class III asymmetry.

Materials and methods

Seventy adults with class III asymmetry consecutively corrected through surgery-first Le Fort I and bilateral sagittal split osteotomies were investigated. Cone-beam computed tomography before treatment (T0), 1-week after surgery (T1), and after all treatment (T2, ≥1-year after surgery) was used to assess surgical movement (T0 to T1) and skeletal stability (T1 to T2) regarding the translation and rotation of the maxillary, mandibular distal, and proximal segments.

Results

At T1, the maxillary segment had moved forward and upward, turned to the deviated side, and rotated downward (all P < 0.01). The distal segment of mandible had moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment had moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment had moved upward and tilted to the deviated side (both P < 0.01). At T2, significant relapse occurred in the mandible. The distal segment moved forward and upward and rotated upward (all P < 0.001). The deviated proximal segment moved upward, tilted to the opposite side, and rotated upward (all P < 0.001). The opposite proximal segment moved upward and tilted to the deviated side (both P < 0.01).

Conclusion

Clinically significant relapse of class III asymmetry was discovered on the mandibular distal and opposite proximal segments.

Orthodontic-surgical management of severe skeletal class iii malocclusion: A case report

Skeletal Class III malocclusion possess a difficult challenge to treat for clinicians. They are multifactorial and include genetic and environmental factors. Early intervention of Class III needs orthopedic correction, whereas, in adults, orthodontic camouflage can be done to treat mild cases while severe skeletal discrepancies demand orthognathic surgery along with orthodontic therapy. In this case report, a case of mandibular prognathism with Bilateral Sagittal Split Osteotomy (BSSO) setback was presented.

Relapse in class II orthognathic surgery: a systematic review

OBJECTIVES

Relapse after orthognathic surgery seems to depend on diverse factors. Proffit et al. postulated in 2007 a "hierarchy of stability" (Head Face Med 6:66, 2007), ranking posttreatment stability after various orthognathic procedures, but no systematically reviewed evidence was provided. Therefore, the aim of this review was to investigate the extent of class II relapse in orthognathic surgery of Angle class II patients depending on the surgical procedure used.

MATERIALS AND METHODS

Seven databases were searched for randomized and controlled clinical trials to compare relapse in surgical procedures for Angle class II patients. After duplicate study selection, data extraction and risk of bias assessment were performed with the ROBINS-I tool as well as data synthesis by frequency distribution, followed by assessment of the quality of evidence with GRADE.

RESULTS

Four non-randomized cohort-studies with a total of 132 patients were included. Bimaxillary procedures as well mandibular advancement procedures proved to be highly stable. Single jaw interventions at the maxilla achieved mostly stable results at sagittal dimension and problematic stability in the vertical dimension. However, there were only limited data available with low quality of evidence.

CONCLUSIONS

Limited existing evidence of low quality partly support the postulated hierarchy of stability of Proffit et al. (Head Face Med 6:66, 2007) and indicates that a surgical correction of class II dysgnathia with bimaxillary procedures and mandibular advancement seems to be highly stable. However, additional studies are needed to address the relation between relapse and surgical orthognathic intervention. Trial registration PROSPERO 2019 CRD42019144873.

Midpalatal Suture Maturation Method for the Assessment of Maturation before Maxillary Expansion: A Systematic Review

Assessment of midpalatal suture maturation is crucial before deciding which type of maxillary expansion technique will be performed to treat transverse discrepancies. In 2013, Angelieri et al. proposed a new method to evaluate midpalatal maturation using cone-beam computed tomography. The aim of this study was to systematically identify, evaluate, and provide a synthesis of the existing literature about this new method and to rigorously assess the methodological quality of these articles. A bibliographic search was carried out using PubMed, Cochrane Library, SciELO, LILACS, Web of Science, and Scopus using the terms midpalatal suture, cranial sutures, palate, maturation, interdigitation, ossification, maxillary expansion, evaluation, assessment, and assess. Quality assessment was performed using the Observational Cohort and Cross-Sectional Studies tool developed by the National Heart, Lung, and Blood Institute. Hence, 56 articles were obtained, of which only 10 met the selection criteria. We could not include any of the data into an analysis because of the large variation of the data collected and high methodological heterogeneity found among studies. Of all the studies included, 10% had poor quality, 70% fair, and 20% good quality, respectively. Even though age and sex play a role in midpalatal suture obliteration, there is a poor correlation between these variables. Thus, every patient should be assessed individually before choosing the best protocol for maxillary expansion. The midpalatal suture maturation method has the potential to be used for diagnostic purposes, but clinicians should be cautious of routinely using it because an extensive training and calibration program should be performed prior.

Accuracy of virtual surgical planning in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach

Background

This study aimed to assess the accuracy of virtual surgical planning (VSP) in segmental osteotomy in combination with bimaxillary orthognathic surgery with surgery first approach (SFA) by means of three-dimensional (3D) measuring and superimposition, so as to promote the application of digital technology in combined orthodontic-orthognathic treatment.

Methods

20 patients treated with segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA from 2018 to 2020 were included. All of them acquired VSP performed by ProPlan CMF 3.0 software (Materialise Corporation, Belgium). The preoperative (T0) 3D model of VSP and the postoperative (T1) 3D model, reconstructed by the cone-beam computed tomography (CBCT) data acquired one week after surgery, were compared by measuring the 3D coordinates of the landmarks as well as 3D model superimposition for deviation analysis. The deviation analysis was achieved by Geomagic Studio 2013 (3D Systems Corporation, USA). The differences which represented the accuracy of VSP were evaluated by the root mean square deviation (RMSD) and the Bland–Altman method.

Results

There was no statistically significant difference between the 3D coordinates of T1 and T0 (P > 0.05), and the mean overall RMSD was 1.37 mm, within the clinical relevance of 2 mm. The RMSD of sagittal direction (1.76 mm) was greater than that of coronal and vertical directions (1.09 mm and 1.24 mm), and the RMSD of maxillary and mandibular aspects were basically equal (1.30 mm and 1.45 mm). The Bland–Altman method showed the T0 and T1 measurements were in good agreement. The mean RMSD obtained from the deviation analysis was 1.85 mm, within the clinical relevance.

Conclusions

VSP in segmental osteotomy in combination with bimaxillary orthognathic surgery with SFA proved to acquire accurate outcome in this study.

Comparative stability and outcomes of two surgical approaches for correction of class III asymmetry with lip or occlusal cant

OBJECTIVES

To assess and compare the stability and outcomes of the two surgical approaches for patients with roll asymmetry.

MATERIALS AND METHODS

A total of 50 adult patients were consecutively recruited for this prospective study. Patients with class III asymmetry and lip or occlusal cant who underwent bimaxillary surgery were grouped according to surgical approach: asymmetric posterior impaction on both sides (API, n = 31) and posterior impaction on one side and posterior extrusion on the other side (PIE, n = 19). Postsurgical stability and outcomes between groups were determined with cone-beam computed tomography for facial midline, lip, and occlusal cant at 1 week (T1), and at least 12-month postsurgery (T2, completion of orthodontic treatment).

RESULTS

Presurgery, the upper anterior occlusal cant and lip cant were significantly greater for the PIE group (p < 0.05). Postsurgery (T2), the mandible moved upward and rotated upward in both groups. However, the upward rotation was significantly greater in the PIE group compared with the API group. Although the two approaches resulted in significant improvements in facial symmetry, the deviation in the facial midline remained under-corrected for most API patients.

CONCLUSIONS

Patient outcomes for mandibular stability and facial symmetry differed between the two surgical approaches for correction of class III asymmetry with lip or occlusal cant.

CLINICAL RELEVANCE

The findings of this study suggest that planned over-correction is a reasonable option for the approach of asymmetric posterior impaction on both sides.

Evaluation of Condylar Positional, Structural, and Volumetric Status in Class III Orthognathic Surgery Patients

BACKGROUND AND OBJECTIVES

The need to evaluate the condylar remodeling after orthognathic surgery, using three-dimensional (3D) images and volume rendering techniques in skeletal Class III patients has been emphasized. The study examined condylar positional, structural, and volumetric changes after bimaxillary or single-jaw maxillary orthognathic surgeries in skeletal Class III patients using the cone-beam computed tomography.

MATERIALS AND METHODS

Presurgical, postsurgical, and one-year post-surgical full field of view (FOV) cone-beam computed tomography (CBCT) images of 44 patients with skeletal Class III deformities were obtained. Group 1 underwent a bimaxillary surgery (28 patients: 24 females and 4 males), with mean age at the time of surgery being 23.8 ± 6.0 years, and Group 2 underwent maxillary single-jaw surgery (16 patients: 8 females and 8 males), with mean age at the time of surgery being 23.7 ± 5.1 years. After the orthognathic surgery, the CBCT images of 88 condyles were evaluated to assess their displacement and radiological signs of bone degeneration. Three-dimensional (3D) condylar models were constructed and superimposed pre- and postoperatively to compare changes in condylar volume.

RESULTS

Condylar position was found to be immediately altered after surgery in the maxillary single-jaw surgery group, but at the one-year follow-up, the condyles returned to their pre-surgical position. There was no significant difference in condylar position when comparing between pre-surgery and one-year follow-up in any of the study groups. Condylar rotations in the axial and coronal planes were significant in the bimaxillary surgery group. No radiological signs of condylar bone degeneration were detected one year after the surgery. Changes in condylar volume after surgery were found to be insignificant in both study groups.

CONCLUSIONS

At one year after orthognathic surgery, there were no significant changes in positional, structural, or volumetric statuses of condyles.

Distraction Osteogenesis Versus Orthognathic Surgery: Demystifying Differences in Concepts, Techniques and Outcomes

Introduction

The popularity and interest evoked by orthognathic surgery and distraction osteogenesis are undisputed in the field of oral and maxillofacial surgery. However, questions regarding the individual identities of either of them with clarity in their concepts, techniques and outcomes have remained unanswered. The aim of this review is to shed light on these questions.

Methods

This review is structured as a narrative review of thirty years of literature available in the specialities of orthognathic surgery and distraction osteogenesis.

Conclusion

The authors present a review of existing literature combined with contrasting experience gained over the years in providing an overview of the merits and demerits of the two surgical techniques which will aid the clinician in justifying the use of one technique over the other.

[Evaluation of mandibular stability and condylar volume after orthognathic surgery in patients with severe temporomandibular joint osteoarthrosis]

OBJECTIVE

To investigate the effect of preoperative condylar condition for mandible retrognathism deformities with severe temporomandibular joint osteoarthrosis on the stability of the jaw after orthognathic surgery and on the postoperative condylar volume changes.

METHODS

In this retrospective study, from 2014 to 2019, 37 patients including 1 male and 36 female, aged between 21 to 34 years old with an average age of (28.03±6.52) years, were diagnosed with mandible retrognathism deformities with severe temporomandibular joint osteoarthrosis by Peking University School and Hospital of Stomatology and received orthognathic surgery, meeting the inclusion criteria were included. According to the preoperative condylar condition. There were divided into smooth group and non-smooth group, the lateral cephalometric films 1 week (T0), 3 months (T1), 6 months (T2) and 1 year (T3) after surgery were used to establish the coordinate system and cephalometric analysis to determine the stability of the jaw after operation. The three-dimensional model of the condyle was segmented by cone beam computed tomography (CBCT) 1 week (T0), 3 months (T1), 6 months (T2) and 1 year (T3) after surgery and the volume was obtained to evaluate the change of the condyle volume after surgery. CBCT image data was used to evaluate the changes of the condylar condition after surgery, and to clarify the correlation between the postoperative condylar condition and jaw stability. SPSS 20.0 statistical software was used for statistical analysis, Fisher's exact probability methods were used to compare whether there were statistically significant differences in the stability of the mandibular joint at stages T1, T2 and T3 with different preoperative condylar condition.Spearman correlation coefficient analysis and Mann-Whitney test were used to compare whether there were statistically significant differences in the volume changes at stages T1, T2 and T3 after surgery between the two groups.

RESULTS

The recurrence rates of the mandible in the condylar smooth group were T1 36.85%, T2 47.37% and T3 42.11%, respectively. The recurrence rates in the non-smooth condylar group were T1 27.78%, T2 44.44% and T3 55.56%, respectively. There was no statistical difference in the recurrence rates between the two groups at different time points. There was no significant difference in the condylar volume change between smooth group and non-smooth group.

CONCLUSION

For patients with mandible retrognathism deformities with severe temporomandibular joint osteoarthrosis and no significant changes in the condyle observed for one year before surgery, there is no difference in the influence of the preoperative condylar condition on the stability of jaw after operation, and no definite influence on the volume of the condyle after operation. Condylar resorption 3 months after surgery can cause instability of the jaw after orthognathic surgery.

[Efficiency of orthodontic treatment in combination with surgically assisted rapid palatal expansion]

The aim of this study was to evaluate the effectiveness of combined orthodontic and surgical treatment of patients with maxillary transverse deficiency. Forty cone-beam computed tomograms (CBCT) were examined in 20 patients (mean age 23.5 years) who underwent surgically assisted rapid palatal expansion using a tooth-borne appliance (n=10) and a bone-borne appliance (n=10). Evaluation of the effectiveness of skeletal expansion was carried out with the help of cephalometric analysis of the width of the upper jaw in the coronary projection on the CBCT by 22 parameters. Analysis of the degree of skeletal expansion of the upper jaw before treatment and after removal of the expander allowed to assess the degree of expansion of the upper jaw at different bone levels. Surgically assisted rapid palatal expansion allows to achieve stable skeletal expansion of the upper jaw in the transverse direction with minimal risk of long-term relapse.

Relapse after Le Fort I surgery in oral cleft patients: a 2-year follow-up using digitized and 3D models

This retrospective observational study aimed to evaluate and identify the relapse rate after orthognathic surgery for maxillary advancement (Le Fort I maxillary osteotomy) in oral cleft patients through digitized cephalograms and 3D dental models, following 2 years. Lateral cephalograms and dental casts of 17 individuals, enrolled in Orthodontics Department in Hospital of Rehabilitation of Craniofacial Anomalies, were carried out. The digital cephalometric tracings were evaluated in: T1-before surgery, T2-immediate after surgery, T3-6-month to 1-year after surgery. The dental study casts were digitized and evaluated in: F1-before surgery; F2-3-month to 1-year after surgery; F3-1 to 2 years after surgery. The analyses of the dental arches were performed directly on the scanned images. A single examiner previously trained and calibrated performed all the assessments. Repeated measures ANOVA was applied to study the variables and compare the periods, followed by Tukey test to evaluate the statistically significant differences, with level of significance of 5%. The digital cephalogram results showed that the vertical movement statistically differed from T2 to T3 (p = 0.002). The right and left premolar relationship in digitized models revealed that at F2 the individuals exhibited ¼ Class II and Class I, in 29.4 and 23.5% of the cases, respectively; and at F3, Class I, 58.8 and 70.6% of the cases, respectively. The cephalometry showed the relapse in the vertical movement after orthognathic surgery for maxillary advancement, but no relapse in the other evaluated parameters.

Comparative study of postoperative stability between conventional orthognathic surgery and a surgery-first orthognathic approach after bilateral sagittal split ramus osteotomy for skeletal class III correction

Objectives

The purpose of this study is to compare the postoperative stability of conventional orthognathic surgery to a surgery-first orthognathic approach after bilateral sagittal split ramus osteotomy (BSSRO).

Materials and Methods

The study included 20 patients who underwent BSSRO for skeletal class III conventional orthognathic surgery and 20 patients who underwent a surgery-first orthognathic approach. Serial lateral cephalograms were analyzed to identify skeletal changes before surgery (T0), immediately after surgery (T1), and after surgery (T2, after 1 year or at debonding).

Results

The amount of relapse of the mandible in the conventional orthognathic surgery group from T1 to T2 was 2.23±0.92 mm (P<0.01) forward movement and −0.87±0.57 mm (non-significant, NS) upward movement on the basis of point B and 2.54±1.37 mm (P<0.01) forward movement and −1.18±0.79 mm (NS) upward movement on the basis of the pogonion (Pog) point. The relapse amount of the mandible in the surgery-first orthognathic approach group from T1 to T2 was 3.49±1.71 mm (P<0.01) forward movement and −1.78±0.81 mm (P<0.01) upward movement on the basis of the point B and 4.11±1.93 mm (P<0.01) forward movement and −2.40±0.98 mm (P<0.01) upward movement on the basis of the Pog.

Conclusion

The greater horizontal and vertical relapse may appear because of counter-clockwise rotation of the mandible in surgery-first orthognathic approach. Therefore, careful planning and skeletal stability should be considered in orthognathic surgery.

Management of severe skeletal Class III malocclusion with bimaxillary orthognathic surgery

Orthognathic surgery in conjunction with fixed orthodontics is a common indication for interdisciplinary management of severe skeletal Class III malocclusion. A thorough analysis of pretreatment investigations and development of a surgical visual treatment objective is essential to plan the type of surgical technique required. Bimaxillary orthognathic surgery is the most common type of surgical procedure for severe skeletal discrepancies. The present case report is a combined ortho-surgical team management of a skeletally Class III patient. The severity of the case required bilateral upper first premolar extraction for dentoalveolar decompensation and simultaneous "Two-jaw surgery" with maxillary advancement of 4 mm and mandibular setback of 7 mm. Postsurgery, a pleasing good facial profile was achieved with Class II molar relation and positive overjet.

Modern trends in Class III orthognathic treatment: A time series analysis

OBJECTIVE

To examine the current trends in surgical-orthodontic treatment for patients with Class III malocclusion using time-series analysis.

MATERIALS AND METHODS

The records of 2994 consecutive patients who underwent orthognathic surgery from January 1, 2004, through December 31, 2015, at Seoul National University Dental Hospital, Seoul, Korea, were reviewed. Clinical data from each surgical and orthodontic treatment record included patient's sex, age at the time of surgery, malocclusion classification, type of orthognathic surgical procedure, place where the orthodontic treatment was performed, orthodontic treatment modality, and time elapsed for pre- and postoperative orthodontic treatment.

RESULTS

Out of the orthognathic surgery patients, 86% had Class III malocclusion. Among them, two-jaw surgeries have become by far the most common orthognathic surgical treatment these days. The age at the time of surgery and the number of new patients had seasonal variations, which demonstrated opposing patterns. There was neither positive nor negative correlation between pre- and postoperative orthodontic treatment time. Elapsed orthodontic treatment time for both before and after Class III orthognathic surgeries has been decreasing over the years.

CONCLUSION

Results of the time series analysis might provide clinicians with some insights into current surgical and orthodontic management.

Skeletal Stability after Large Mandibular Advancement (> 10 mm) with Bilateral Sagittal Split Osteotomy and Skeletal Elastic Intermaxillary Fixation

OBJECTIVES

The aim of the present study was to assess the skeletal stability after large mandibular advancement (> 10 mm) with bilateral sagittal split osteotomy and skeletal elastic intermaxillary fixation and to correlate the skeletal stability with the vertical facial type.

MATERIAL AND METHODS

A total of 33 consecutive patients underwent bimaxillary surgery to correct skeletal Class II malocclusion with a mandibular advancement (> 10 mm) measured at B-point and postoperative skeletal elastic intermaxillary fixation for 16 weeks. Skeletal stability was evaluated using lateral cephalometric radiographs obtained preoperative (T1), 8 weeks postoperatively (T2), and 18 month postoperatively (T3). B-point and pogonion (Pog) was used to measure the skeletal relapse and the mandibular plane angle (MP-angle) was used to determine the vertical facial type.

RESULTS

The mean advancement from T1 to T2 were 11.6 mm and 13.5 mm at B-point and Pog, respectively. The mean skeletal relapse from T2 to T3 was -1.3 mm at B-point and -1.6 mm at Pog. The nineteen patients characterized as long facial types, showed the highest amount of skeletal relapse (-1.5 mm at B-point and -1.9 mm at Pog).

CONCLUSIONS

The present study showed a limited amount of skeletal relapse in large mandibular advancement (> 10 mm) with bilateral sagittal split osteotomy and skeletal elastic intermaxillary fixation. Bilateral sagittal split osteotomy in combination with skeletal intermaxillary fixation can therefore be an alternative to distraction osteogenesis in large mandibular advancements.

Interrelationship between implant and orthognathic surgery for the rehabilitation of edentulous cleft palate patients: a case report

A 43-year-old woman with a unilateral cleft lip and palate, presenting a totally edentulous maxilla and mandible with marked maxillomandibular discrepancy, attended the Prosthodontics section of the Hospital for Rehabilitation of Craniofacial Anomalies, University of São Paulo for treatment. She could not close her mouth and was dissatisfied with her complete dentures. Treatment planning comprised placement of six implants in the maxilla, four in the mandible followed by prostheses installation and orthognathic surgery. The mandibular full arch prosthesis guided the occlusion for orthognathic positioning of the maxilla. The maxillary complete prosthesis was designed to assist the orthognathic surgery with a provisional prosthesis (no metal framework), allowing reverse treatment planning. Maxillary and mandibular realignment was performed. Three months later, a relapse in the position of the maxilla was observed, which was offset with a new maxillary prosthesis. This isa complex interdisciplinary treatment and two-year follow-up is presented and discussed. It should be considered that this type of treatment could also be applied in non-cleft patients.

A combined periodontal - prosthetic treatment approach to manage unusual gingival visibility in resting lip position and inversely inclined upper anterior teeth: a case report with discussion

Excessive gingival visibility during smile is a common esthetic complaint in dentistry, but excessive gingival visibility in resting lip position is relatively uncommon condition. Several exclusive radical to conservative surgical treatment or its combination with orthodontic therapy to treat this condition are within the reach of every patient nowadays. A case report of an excessive gingival visibility because of altered passive eruption along with inversely inclined maxillary anterior teeth is presented here. A relatively simple treatment approach combining periodontal and restorative therapy is used here to achieve the desirable aesthetic results. The gingival exposure resulting from altered passive eruption was completely managed by a gingivectomy, but the inclined appearance of teeth was still an aesthetic complaint. After complete healing of gingivectomy surgery, appropriately designed crowns were given to rectify the inversely inclined appearance. A complete rehabilitation of patient's smile could be achieved, the case was followed up for 3 years and the condition was found satisfactory.

Evaluation of 3-dimensional superimposition techniques on various skeletal structures of the head using surface models

Objectives

To test the applicability, accuracy, precision, and reproducibility of various 3D superimposition techniques for radiographic data, transformed to triangulated surface data.

Methods

Five superimposition techniques (3P: three-point registration; AC: anterior cranial base; AC + F: anterior cranial base + foramen magnum; BZ: both zygomatic arches; 1Z: one zygomatic arch) were tested using eight pairs of pre-existing CT data (pre- and post-treatment). These were obtained from non-growing orthodontic patients treated with rapid maxillary expansion. All datasets were superimposed by three operators independently, who repeated the whole procedure one month later. Accuracy was assessed by the distance (D) between superimposed datasets on three form-stable anatomical areas, located on the anterior cranial base and the foramen magnum. Precision and reproducibility were assessed using the distances between models at four specific landmarks. Non parametric multivariate models and Bland-Altman difference plots were used for analyses.

Results

There was no difference among operators or between time points on the accuracy of each superimposition technique (p>0.05). The AC + F technique was the most accurate (D<0.17 mm), as expected, followed by AC and BZ superimpositions that presented similar level of accuracy (D<0.5 mm). 3P and 1Z were the least accurate superimpositions (0.79<D<1.76 mm, p<0.005). Although there was no difference among operators or between time points on the precision of each superimposition technique (p>0.05), the detected structural changes differed significantly between different techniques (p<0.05). Bland-Altman difference plots showed that BZ superimposition was comparable to AC, though it presented slightly higher random error.

Conclusions

Superimposition of 3D datasets using surface models created from voxel data can provide accurate, precise, and reproducible results, offering also high efficiency and increased post-processing capabilities. In the present study population, the BZ superimposition was comparable to AC, with the added advantage of being applicable to scans with a smaller field of view.

Use of mini-implants to avoid maxillary surgery for Class III mandibular prognathic patient: a long-term post-retention case

Because of the potential morbidity and complications associated with surgical procedures, limiting the extent of orthognathic surgery is a desire for many orthodontic patients. An eighteen-year-old woman had a severe Class III malocclusion and required bi-maxillary surgery. By changing the patient's maxillary occlusal plane using orthodontic mini-implants, she was able to avoid the maxillary surgery; requiring only a mandibular setback surgery. To accurately predict the post-surgery outcome, we applied a new soft tissue prediction method. We were able to follow and report the long-term result of her combined orthodontic and orthognathic treatment. The changes to her occlusal plane continue to appear stable over 6 years later.

Class III Malocclusion Surgical-Orthodontic Treatment

The aim of the present case report is to describe the orthodontic-surgical treatment of a 17-year-and-9-month-old female patient with a Class III malocclusion, poor facial esthetics, and mandibular and chin protrusion. She had significant anteroposterior and transverse discrepancies, a concave profile, and strained lip closure. Intraorally, she had a negative overjet of 5 mm and an overbite of 5 mm. The treatment objectives were to correct the malocclusion, and facial esthetic and also return the correct function. The surgical procedures included a Le Fort I osteotomy for expansion, advancement, impaction, and rotation of the maxilla to correct the occlusal plane inclination. There was 2 mm of impaction of the anterior portion of the maxilla and 5 mm of extrusion in the posterior region. A bilateral sagittal split osteotomy was performed in order to allow counterclockwise rotation of the mandible and anterior projection of the chin, accompanying the maxillary occlusal plane. Rigid internal fixation was used without any intermaxillary fixation. It was concluded that these procedures were very effective in producing a pleasing facial esthetic result, showing stability 7 years posttreatment.

Positional change of the condyle after orthodontic-orthognathic surgical treatment: is there a relationship to skeletal relapse?

Objectives

The purpose of this study was to evaluate the condylar position in relation to the glenoid fossa before and after orthodontic-orthognathic surgical treatment and to investigate the relationship with skeletal relapse.

Materials and Methods

Lateral cephalograms and temporomandibular joint tomograms from 19 patients with mandibular prognathism who received orthodontic-orthognathic surgery were included in this study. Samples were divided into two groups based on skeletal change during the retention period. The relapse group consisted of 7 patients (3 females and 4 males; mean age, 21.9 years) whose pogonion or menton displaced more than 1 mm during the retention period and the stable group consisted of 12 patients (5 females and 7 males; mean age, 21.7 years). Anterior joint space, posterior joint space, superior joint space, and anteroposterior index were measured on tomograms at pretreatment and posttreatment timepoints. Condyle position and frequency of the positional change were compared between both groups.

Results

In the relapse group and stable group, 42.9% and 45.8% of the condyles, respectively, showed forward or backward displacement at posttreatment. However, the changes were small and the mean anterior, posterior, superior joint spaces and frequencies of the positional changes did not differ statistically between both groups.

Conclusion

Our results suggest that small positional changes of the condyle, which may occur after orthodontic-orthognathic surgery treatment, may not be related to skeletal relapse after removal of the orthodontic appliances.

Unfavourable outcomes in orthognathic surgery

Unfavourable outcomes are part and parcel of performing surgeries of any kind. Unfavourable outcomes are results of such work, which the patient and or the clinician does not like. This is an attempt to review various causes for unfavorable outcomes in orthognathic surgery and discuss them in detail. All causes for unfavorable outcomes may be classified as belonging to one of the following periods A) Pre- Treatment B) During treatment Pre-Treatment: In orthognathic surgery- as in any other discipline of surgery- which involves changes in both aesthetics and function, the patient motivation for seeking treatment is a very important input which may decide, whether the outcome is going to be favorable or not. Also, inputs in diagnosis and plan for treatment and its sequencing, involving the team of the surgeon and the orthodontist, will play a very important role in determining whether the outcome will be favorable. In other words, an unfavorable outcome may be predetermined even before the actual treatment process starts. During Treatment: Good treatment planning itself does not guarantee favorable results. The execution of the correct plan could go wrong at various stages which include, Pre-Surgical orthodontics, Intra and Post-Operative periods. A large number of these unfavorable outcomes are preventable, if attention is paid to detail while carrying out the treatment plan itself. Unfavorable outcomes in orthognathic surgery may be minimized If pitfalls are avoided both, at the time of treatment planning and execution.

Comparative Study of Skeletal Stability between Postoperative Skeletal Intermaxillary Fixation and No Skeletal Fixation after Bilateral Sagittal Split Ramus Osteotomy: an 18 Months Retrospective Study

Objectives

The purpose of the present study was to evaluate skeletal stability after mandibular advancement with bilateral sagittal split osteotomy.

Material and Methods

Twenty-six patients underwent single-jaw bilateral sagittal split osteotomy (BSSO) to correct skeletal Class II malocclusion. One group (n = 13) were treated postoperatively with skeletal elastic intermaxillary fixation (IMF) while the other group (n = 13) where threated without skeletal elastic IMF.

Results

The mean advancement at B-point and Pog in the skeletal elastic IMF group was 6.44 mm and 7.22 mm, respectively. Relapse at follow-up at B-point was -0.74 mm and -0.29 mm at Pog. The mean advancement at B-point and Pog in the no skeletal elastic IMF group was 6.30 mm and 6.45 mm, respectively. Relapse at follow-up at B-point was -0.97 mm and -0.86 mm at Pog. There was no statistical significant (P > 0.05) difference between the skeletal IMF group and the no skeletal group regarding advancement nor relapse at B-point or Pog.

Conclusions

Bilateral sagittal split osteotomy is characterized as a stable treatment to correct Class II malocclusion. This study demonstrated no difference of relapse between the skeletal intermaxillary fixation group and the no skeletal intermaxillary fixation group. Because of selection-bias and the reduced number of patients it still remains inconclusive whether to recommend skeletal intermaxillary fixation or not in the prevention of relapse after mandibular advancement.

Midpalatal suture maturation: classification method for individual assessment before rapid maxillary expansion

INTRODUCTION

In this study, we present a novel classification method for individual assessment of midpalatal suture morphology.

METHODS

Cone-beam computed tomography images from 140 subjects (ages, 5.6-58.4 years) were examined to define the radiographic stages of midpalatal suture maturation. Five stages of maturation of the midpalatal suture were identified and defined: stage A, straight high-density sutural line, with no or little interdigitation; stage B, scalloped appearance of the high-density sutural line; stage C, 2 parallel, scalloped, high-density lines that were close to each other, separated in some areas by small low-density spaces; stage D, fusion completed in the palatine bone, with no evidence of a suture; and stage E, fusion anteriorly in the maxilla. Intraexaminer and interexaminer agreements were evaluated by weighted kappa tests.

RESULTS

Stages A and B typically were observed up to 13 years of age, whereas stage C was noted primarily from 11 to 17 years but occasionally in younger and older age groups. Fusion of the palatine (stage D) and maxillary (stage E) regions of the midpalatal suture was completed after 11 years only in girls. From 14 to 17 years, 3 of 13 (23%) boys showed fusion only in the palatine bone (stage D).

CONCLUSIONS

This new classification method has the potential to avoid the side effects of rapid maxillary expansion failure or unnecessary surgically assisted rapid maxillary expansion for late adolescents and young adults.

Temporomandibular joint condylar changes following maxillomandibular advancement and articular disc repositioning

PURPOSE

To evaluate condylar changes 1 year after bimaxillary surgical advancement with or without articular disc repositioning using longitudinal quantitative measurements in 3-dimensional (3D) temporomandibular joint (TMJ) models.

METHODS

Twenty-seven patients treated with maxillomandibular advancement (MMA) underwent cone-beam computed tomography before surgery, immediately after surgery, and at 1-year follow-up. All patients underwent magnetic resonance imaging before surgery to assess disc displacements. Ten patients without disc displacement received MMA only. Seventeen patients with articular disc displacement received MMA with simultaneous TMJ disc repositioning (MMA-Drep). Pre- and postsurgical 3D models were superimposed using a voxel-based registration on the cranial base.

RESULTS

The location, direction, and magnitude of condylar changes were displayed and quantified by graphic semitransparent overlays and 3D color-coded surface distance maps. Rotational condylar displacements were similar in the 2 groups. Immediately after surgery, condylar translational displacements of at least 1.5 mm occurred in a posterior, superior, or mediolateral direction in patients treated with MMA, whereas patients treated with MMA-Drep presented more marked anterior, inferior, and mediolateral condylar displacements. One year after surgery, more than half the patients in the 2 groups presented condylar resorptive changes of at least 1.5 mm. Patients treated with MMA-Drep presented condylar bone apposition of at least 1.5 mm at the superior surface in 26.4%, the anterior surface in 23.4%, the posterior surface in 29.4%, the medial surface in 5.9%, or the lateral surface in 38.2%, whereas bone apposition was not observed in patients treated with MMA.

CONCLUSIONS

One year after surgery, condylar resorptive changes greater than 1.5 mm were observed in the 2 groups. Articular disc repositioning facilitated bone apposition in localized condylar regions in patients treated with MMA-Drep.

Long-term 3-dimensional stability of mandibular advancement surgery

PURPOSE

To evaluate 3-dimensional changes in the position of the condyles, rami, and chin from 1 to 3 years after mandibular advancement surgery.

MATERIALS AND METHODS

This prospective observational study used pre- and postoperative cone-beam computed tomograms of 27 subjects with skeletal Class II jaw relation and normal or deep overbite. An automatic technique of cranial base superimposition was used to assess positional and bone remodeling changes that were visually displayed and quantified using 3-dimensional color maps. Analysis of covariance with presence of genioplasty, age at time of surgery, and gender as explanatory variables was used to estimate and test adjusted mean changes for each region of interest.

RESULTS

The chin rotated downward and backward 1 to 3 years after surgery. Changes of at least 2 mm were observed in 17% of cases. Mandibular condyles presented with displacements or bone remodeling of at least 2 mm on the anterior surface (21% of cases on the left side and 13% on the right), superior surface (8% on right and left sides), and lateral poles (17% on left side and 4% on right). Posterior borders of the rami exhibited symmetric lateral or rotational displacements in 4% of cases.

CONCLUSION

In the hierarchy of surgical stability, mandibular advancement surgery is considered one of the most stable surgical procedures. However, 1 to 3 years after surgery, approximately 20% of patients had 2- to 4-mm changes in horizontal and vertical chin positions or changes in condylar position and adaptive bone remodeling.

Outcome quantification using SPHARM-PDM toolbox in orthognathic surgery

PURPOSE

Quantification of surgical outcomes in longitudinal studies has led to significant progress in the treatment of dentofacial deformity, both by offering options to patients who might not otherwise have been recommended for treatment and by clarifying the selection of appropriate treatment methods. Most existing surgical treatments have not been assessed in a systematic way. This paper presents the quantification of surgical outcomes in orthognathic surgery via our localized shape analysis framework.

METHODS

In our setting, planning and surgical simulation is performed using the surgery planning software CMFapp. We then employ the SPHARM-PDM to measure the difference between pre-surgery and virtually simulated post-surgery models. This SPHARM-PDM shape framework is validated for use with craniofacial structures via simulating known 3D surgical changes within CMFapp.

RESULTS

Our results show that SPHARM-PDM analysis accurately measures surgical displacements, compared with known displacement values. Visualization of color maps of virtually simulated surgical displacements describe corresponding surface distances that precisely describe location of changes, and difference vectors indicate directionality and magnitude of changes.

CONCLUSIONS

SPHARM-PDM-based quantification of surgical outcome is feasible. When compared to prior solutions, our method has the potential to make the surgical planning process more flexible, increase the level of detail and accuracy of the plan, yield higher operative precision and control and enhance the follow-up and documentation of clinical cases.

Factors influencing the accuracy of cephalometric prediction of soft tissue profile changes following orthognathic surgery

The cephalometric prediction of orthognathic treatment outcome is an important part of the surgical planning and the process of informed consent. The orthodontic and surgical changes must be described accurately prior to treatment in order to assess the treatment's feasibility, to optimize case management and to increase patient's understanding and acceptance of the recommended treatment. The aim of the present article was to investigate on the factors that could influence the accuracy of cephalometric prediction in planning orthognathic surgery. Review of the literature revealed that, besides factors directly related to the prediction method and its use, there exist a considerable number of factors which could affect significantly the accuracy of soft tissue response. These factors could be biological ones such as relapse, centre of mandibular rotation and individual variation in response to treatment and others such as gender, race, pre-operative soft tissue thickness and data bases for mean ratios of soft to hard tissue movement changes. Some of the factors affecting the accuracy of prediction of soft tissue response following orthognathic surgery are inevitable and there are others, difficult to control and predict. However, patients should be informed that predictions are only a guide, may not represent the actual result of the surgical outcome, and as such they should be implemented.

Three-dimensional regional displacements after mandibular advancement surgery: one year of follow-up

PURPOSE

To evaluate the association of 3-dimensional changes in the position of the condyles, rami, and chin at splint removal and 1 year after mandibular advancement surgery.

PATIENTS AND METHODS

This prospective observational study used preoperative and postoperative scans of 27 subjects presenting with a skeletal Class II jaw relationship with a normal or deep overbite. An automatic technique of cranial base superimposition was used to assess the positional and/or remodeling changes in the anatomic regions of interest. The displacements were visually displayed and quantified using 3-dimensional color maps. The positive and negative values of surface distances in the color maps indicated the direction of the displacements. Pearson correlation coefficients and a linear model for correlated data were used to evaluate the association between the regional displacements.

RESULTS

The postoperative adaptations in the chin position between splint removal and 1 year after surgery were significantly negatively correlated with changes in the borders of the posterior ramus (left, r = -0.73, P ≤ .0001; and right, r = -0.68, P = .00) and the condyles (left, r = -0.53, P = .01; and right, r = -0.46, P = .02), indicating that these structures tended to be displaced in the same direction. Even though the mean condylar displacement with surgery was less than 1 mm, individual displacements greater than 2 mm with surgery were observed for 24% of the condyles. The condylar displacements were maintained at 1 year after surgery for 17% of the condyles.

CONCLUSIONS

The surface distance displacements indicated that the postoperative adaptations at different anatomic regions were significantly related.

Postsurgical Orthodontic Treatment Planning: a Case Report with 20 Years Follow-up

Background

Traditionally, maxillofacial deformities are corrected surgically after an initial orthodontic treatment phase. However in, this article, the authors emphasize the postsurgical therapeutic protocol which is extremely important for determining the final and permanent retention of the corrected occlusion.

Methods

A 55 year old female with severe skeletal Class II malocclusion is presented. Combined surgical and orthodontic correction of the malocclusion was used.

Results

: The step-by-step procedure the authors followed for the postsurgical therapy is described. The goals of the postoperative therapy were to restore and rehabilitate neuromuscular function, obtain occlusal stabilization, grind teeth selectively, and final occlusion retention. The importance of a surgical occlusal splint for rehabilitating stomatognathic neuromuscular function postoperatively was demonstrated. Furthermore, the orthodontic-prosthodontic treatment ensured occlusion stability after the surgical correction. The long-term results confirmed the efficacy of the treatment protocol presented here from both functional and aesthetical perspectives.

Conclusions

Postsurgical orthodontic treatment is an important step in the surgical and orthodontic therapy of maxillofacial deformities.

Three-dimensional assessment of mandibular advancement 1 year after surgery

INTRODUCTION

This prospective observational study evaluated changes in the 3-dimensional position and remodeling of the mandibular rami, condyles, and chin at splint removal and 1 year after mandibular advancement surgery.

METHODS

Presurgery, splint removal (4-6 weeks postsurgery), and 1-year postsurgery cone-beam computed tomography scans of 27 subjects were used. Superimposition on the cranial base was used to assess positional or remodeling changes in the anatomic regions of interest. Surface distance displacements were visually displayed and quantified by 3-dimensional color maps. A 1-sample t test was used to assess the average postsurgical changes of each region of interest. The level of significance was set at 0.05.

RESULTS

After antero-inferior chin displacement with surgery (mean, 6.81 +/- 3.2 mm at splint removal), the average 1-year postsurgery displacement was not statistically significant (P = 0.44). Postsurgical adaptations greater than 2 mm were observed in 48% of the patients: 16% with an additional anterior-inferior displacement of the chin of 2 to 4 mm, and 4% with >or= 4 mm; 20% had postero-superior movement of 2 to 4 mm, and 8% had postero-superior movement of >or= 4 mm. The condyles tended to move, on average, <or= 2 mm supero-posteriorly with surgery, and this small positional displacement was maintained 1 year postsurgery (right condyle, P = 0.58; left, P = 0.88). The rami exhibited outward (lateral) movements with surgery, with greater displacement of the inferior part of the rami (2 mm in 65% of the subjects). This torque of the ramus with surgery was stable 1 year postsurgery.

CONCLUSIONS

Three-dimensional assessment of skeletal changes with mandibular advancement surgery shows that nearly half of the patients have >2 mm change in chin position from splint removal to the 1-year follow-up, with approximately equal chances of anterior and posterior movement. Torque of the rami usually occurs with mandibular advancement surgery.

Assessment of mandibular advancement surgery with 3D CBCT models superimposition

OBJECTIVES: To assess surgery and short-term post-surgery changes in the position of the condyles, rami and chin after mandibular advancement. METHODOLOGY: Pre-surgery (T1), 1 week post-surgery (T2), and 6 week post-surgery (T3) CBCT scans were acquired for 20 retrognathic patients with short or normal face height. 3D models were built and superimposed through a fully automated voxel-wise method using the cranial base of the pre-surgery scan as reference. Anatomic regions of interest were selected and analyzed separately. Within-subject surface distances between T1-T2, T2-T3, and T1-T3 were computed. Color-coded maps and semi-transparent display of overlaid structures allowed the evaluation of displacement directions. RESULTS: After an antero-inferior chin displacement with surgery in all cases (>4 mm in 87.5%), 25% of the patients showed some kind of posterior movement (< 3 mm), and 69% showed an antero-superior movement after splint removal. Comparing T1-T3, an antero-inferior (87.5% of the cases) or only inferior (12.5%) displacement was observed (>4 mm in 80%). Considering all directions of displacement, the surface distance differences for the condyles and rami were small: 77.5% of the condyles moved <2 mm with surgery (T1-T2), and 90% moved <2 mm in the short-term (T2-T3) and in the total evaluation (T1-T3), while the rami showed a <3 mm change with surgery in 72.5% of the cases, and a <2 mm change in 87.5% (T2-T3) and in 82% (T1-T3). CONCLUSIONS: Expected displacements with surgery were observed and post-surgery changes suggested a short-term adaptive response toward recovery of condyle and ramus displacements. The changes on the chin following splint removal suggested an acceptable adaptation, but with considerable individual variability.

CONDYLAR RESORPTION IN PATIENTS WITH TMD

The objective of this study is to determine the nature of the difference between condyle morphology of osteoarthritic temporomandibular joint (TMJ) and non-osteoarthritic TMJ, using 3D surface models constructed from cone-beam CT (CBCT) images. Three-dimensional Shape Correspondence was used to localize and quantify condylar morphological differences of 20 patients with RDC/TMD group III (arthralgia, arthritis, arthrosis) compared to 40 asymptomatic subjects. Three-dimensional models of right and left condyles for each subject were constructed from CBCT images and shape analysis performed using the publicly available SPHARM-PDM software. The right and left condyles were normalized using rigid Procrustes alignment to an overall mean condylar surface per group. The mean differences between groups were compared using the Hotelling T2 analysis with permutation-test derived p-values, corrected for False Discovery Rate. The differences between the group mean surfaces were visualized with color-coded magnitude and difference vectors. The condylar morphology of the TMD group was statistically significantly different from the asymptomatic group (p = 0.05, average surface distance differences of 1.9 mm for the right condyles and 2.3 mm for the left condyles). The average condylar morphology in the TMD patients showed resorption of the anterior surface of the lateral pole and flattening of the articular surface compared to the mean morphology in asymptomatic subjects. The condylar morphology and condylar dimensions of the TMD patients were different, on average, from those of the asymptomatic subjects. The preliminary findings in this cross-sectional study will lead to future investigations to elucidate osteoarthritic changes in TMD and their role in the pathophysiology of TMD. Supported by NIDCR DE017727.

The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension

A hierarchy of stability exists among the types of surgical movements that are possible with orthognathic surgery. This report updates the hierarchy, focusing on comparison of the stability of procedures when rigid fixation is used. Two procedures not previously placed in the hierarchy now are included: correction of asymmetry is stable with rigid fixation and repositioning of the chin also is very stable. During the first post-surgical year, surgical movements in patients treated for Class II/long face problems tend to be more stable than those treated for Class III problems. Clinically relevant changes (more than 2 mm) occur in a surprisingly large percentage of orthognathic surgery patients from one to five years post-treatment, after surgical healing is complete. During the first post-surgical year, patients treated for Class II/long face problems are more stable than those treated for Class III problems; from one to five years post-treatment, some patients in both groups experience skeletal change, but the Class III patients then are more stable than the Class II/long face patients. Fewer patients exhibit long-term changes in the dental occlusion than skeletal changes, because the dentition usually adapts to the skeletal change.

Three-dimensional cone-beam computed tomography for assessment of mandibular changes after orthognathic surgery

INTRODUCTION

The purpose of this study was to assess alterations in the 3-dimensional (3D) position of the mandibular rami and condyles in patients receiving either maxillary advancement and mandibular setback or maxillary surgery only.

METHODS

High-resolution cone-beam computed tomography scans were taken of 21 patients before and after orthognathic surgery. Ten patients with various malocclusions underwent maxillary surgery only, and 11 Class III patients received maxillary advancement and mandibular setback. Presurgery and postsurgery 3D models were registered on the surface of the cranial base. A new tool was used for graphical overlay and 3D display with color maps to visually assess the locations and to quantify positional changes in the posterior border of the mandibular rami and condyles between superimposed models.

RESULTS

The average displacements in condylar position were small--0.77 mm (SD, 0.12 mm) and 0.70 mm (SD, 0.08 mm)--for 2-jaw and 1-jaw surgeries, respectively (not significant, P >.05). All 2-jaw surgery patients had backward rotational displacements of the mandibular rami (mean, 1.98 mm; SD, 1.03 mm), with a maximum surface distance change of > or =2 mm in 8 of 11 subjects. For the 1-jaw surgery, all subjects had small backward rotational displacements of the mandibular rami (mean, 0.78 mm; SD, 0.25 mm), with only 1 subject having a maximum surface distance change > or =2 mm. The difference in mean backward rotational displacement was statistically significant (P <.01).

CONCLUSIONS

The visualization of 3D model superimposition clearly identified the location, magnitude, and direction of mandibular displacement. The 3D imaging allowed quantification of vertical, transverse, and anteroposterior ramus displacement that accompanied mandibular, but not maxillary only, surgery.

Superimposition of 3D cone-beam CT models of orthognathic surgery patients

OBJECTIVES

To evaluate the registration of 3D models from cone-beam CT (CBCT) images taken before and after orthognathic surgery for the assessment of mandibular anatomy and position.

METHODS

CBCT scans were taken before and after orthognathic surgery for ten patients with various malocclusions undergoing maxillary surgery only. 3D models were constructed from the CBCT images utilizing semi-automatic segmentation and manual editing. The cranial base was used to register 3D models of pre- and post-surgery scans (1 week). After registration, a novel tool allowed the visual and quantitative assessment of post-operative changes via 2D overlays of superimposed models and 3D coloured displacement maps.

RESULTS

3D changes in mandibular rami position after surgical procedures were clearly illustrated by the 3D colour-coded maps. The average displacement of all surfaces was 0.77 mm (SD=0.17 mm), at the posterior border 0.78 mm (SD=0.25 mm), and at the condyle 0.70 mm (SD=0.07 mm). These displacements were close to the image spatial resolution of 0.60 mm. The average interobserver differences were negligible. The range of the interobserver errors for the average of all mandibular rami surface distances was 0.02 mm (SD=0.01 mm).

CONCLUSION

Our results suggest this method provides a valid and reproducible assessment of craniofacial structures for patients undergoing orthognathic surgery. This technique may be used to identify different patterns of ramus and condylar remodelling following orthognathic surgery.