James J Xia

Texas A&M University, College Station, TX, United States

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Publications (51)55.97 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this retrospective study was to evaluate the long-term outcomes of using the microscopic minimally invasive approach for the treatment of nonsyndromic craniosynostosis. During the last 10 years, 180 consecutive patients with nonsyndromic craniosynostosis were treated: 67 patients were treated with microscopic minimally invasive approach, and 113 were treated with the open approach. In the microscopic group, there was 1 intraoperative complication (1.5%). There were 10 postoperative complications (14.9%), of which 9 required major reoperations and 1 required a minor procedure. The major complications occurred in 7 unicoronal patients (58.3%) and 2 metopic patients (25.0%). In the open-approach group, there were 8 complications (7.1%), 2 patients required major reoperations and 6 required minor procedures. Chi-squared test showed that there was no statistically significant difference in the overall complication rate between the microscopic and open approaches. However, in the unicoronal patients, the complication rate was significantly higher in the microscopic group (P < 0.001). In conclusion, the microscopic approach is our treatment of choice in nonsyndromic patients with sagittal and lambdoidal craniosynostosis. We no longer use the microscopic approach in patients with unicoronal or metopic craniosynostosis because of the high complication rate.
    The Journal of craniofacial surgery. 07/2014; 25(4):1245-1248.
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    ABSTRACT: Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatment planning of the patients with CMF deformities. However, due to the poor image quality, including very low signal-to-noise ratio and the widespread image artifacts such as noise, beam hardening, and inhomogeneity, it is challenging to segment the CBCT images. In this paper, the authors present a new automatic segmentation method to address these problems. To segment CBCT images, the authors propose a new method for fully automated CBCT segmentation by using patch-based sparse representation to (1) segment bony structures from the soft tissues and (2) further separate the mandible from the maxilla. Specifically, a region-specific registration strategy is first proposed to warp all the atlases to the current testing subject and then a sparse-based label propagation strategy is employed to estimate a patient-specific atlas from all aligned atlases. Finally, the patient-specific atlas is integrated into amaximum a posteriori probability-based convex segmentation framework for accurate segmentation. The proposed method has been evaluated on a dataset with 15 CBCT images. The effectiveness of the proposed region-specific registration strategy and patient-specific atlas has been validated by comparing with the traditional registration strategy and population-based atlas. The experimental results show that the proposed method achieves the best segmentation accuracy by comparison with other state-of-the-art segmentation methods. The authors have proposed a new CBCT segmentation method by using patch-based sparse representation and convex optimization, which can achieve considerably accurate segmentation results in CBCT segmentation based on 15 patients.
    Medical Physics 04/2014; 41(4):043503. · 2.91 Impact Factor
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    ABSTRACT: Current mandibular plating systems contain a wide range of plates and screws needed for the treatment of mandibular reconstruction and mandibular fractures. The authors' hypothesis was that a single diameter screw could be used in all applications in a plating system. Therefore, the purpose of this study was to test if the 2.0-mm locking screws could replace the 2.4-mm screws to stabilize a 2.5-mm-thick reconstruction plate in the treatment of mandibular discontinuity. Thirty-six fresh human cadaveric mandibles were used: 18 were plated using 2.0-mm locking screws (experimental) and the other 18 were plated using 2.4-mm locking screws (control). Each group was further divided into 3 subgroups based on the site of loading application: the ipsilateral (right) second premolar region, the central incisal region, and the contralateral (left) first molar region. The same ipsilateral (right) mandibular angular discontinuity was created by the same surgeon. The mandible was mounted on a material testing machine. The micromotions between the 2 segments, permanent and elastic displacements, were recorded after incremental ramping loads. The magnitude of screw back-out and the separation between plate and bone were recorded using a laser scanner (resolution, 0.12 mm) before and after the loading applications. The data were processed. Descriptive analyses and a general linear model for repeated measures analysis of variance were performed. There was no statistically significant difference in permanent displacement (mean, 1.16 and 0.82 mm, respectively) between the 2.0-mm and 2.4-mm screw groups. There also was no statistically significant difference in elastic displacement between the 2 groups (mean, 1.48 and 1.21 mm, respectively). Finally, there were no statistically significant differences in screw back-out or separation between plate and bone between the 2 groups. All means for screw back-out and separation between screw and bone for each group were judged within the error of the laser scanning system (<0.12 mm). One may anticipate that the mechanical functions of the 2.0-mm locking screws are not different from those of the 2.4-mm screws when a 2.5-mm-thick reconstruction plate is used to reconstruct mandibular angular discontinuity. However, further biomechanical studies (ie, fatigue of screws) are warranted before a randomized clinical trial can be conducted to definitively prove that the 2.4-mm screws can be replaced by 2.0-mm screws.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 09/2013; · 1.58 Impact Factor
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    ABSTRACT: Recent advances in cone-beam computed tomography (CBCT) have rapidly enabled widepsread applications of dentomaxillofacial imaging and orthodontic practices in the past decades due to its low radiation dose, high spatial resolution, and accessibility. However, low contrast resolution in CBCT image has become its major limitation in building skull models. Intensive hand-segmentation is usually required to reconstruct the skull models. One of the regions affected by this limitation the most is the thin bone images. This paper presents a novel segmentation approach based on wavelet density model (WDM) for a particular interest in the outer surface of anterior wall of maxilla. Nineteen CBCT datasets are used to conduct two experiments. This mode-based segmentation approach is validated and compared with three different segmentation approaches. The results show that the performance of this model-based segmentation approach is better than those of the other approaches. It can achieve 0.25 ± 0.2 mm of surface error from ground truth of bone surface.
    Journal of X-Ray Science and Technology 01/2013; 21(2):251-82. · 1.09 Impact Factor
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    ABSTRACT: Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. CBCT scans have relatively low cost and low radiation dose in comparison to conventional spiral CT scans. However, a major limitation of CBCT scans is the widespread image artifacts such as noise, beam hardening and inhomogeneity, causing great difficulties for accurate segmentation of bony structures from soft tissues, as well as separating mandible from maxilla. In this paper, we presented a novel fully automated method for CBCT image segmentation. In this method, we first estimated a patient-specific atlas using a sparse label fusion strategy from predefined spiral CT atlases. This patient-specific atlas was then integrated into a convex segmentation framework based on maximum a posteriori probability for accurate segmentation. Finally, the performance of our method was validated via comparisons with manual ground-truth segmentations.
    Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention. 01/2013; 16(Pt 3):251-8.
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    ABSTRACT: PURPOSE: The purpose of this prospective multicenter study was to assess the accuracy of a computer-aided surgical simulation (CASS) protocol for orthognathic surgery. MATERIALS AND METHODS: The accuracy of the CASS protocol was assessed by comparing planned outcomes with postoperative outcomes of 65 consecutive patients enrolled from 3 centers. Computer-generated surgical splints were used for all patients. For the genioplasty, 1 center used computer-generated chin templates to reposition the chin segment only for patients with asymmetry. Standard intraoperative measurements were used without the chin templates for the remaining patients. The primary outcome measurements were the linear and angular differences for the maxilla, mandible, and chin when the planned and postoperative models were registered at the cranium. The secondary outcome measurements were the maxillary dental midline difference between the planned and postoperative positions and the linear and angular differences of the chin segment between the groups with and without the use of the template. The latter were measured when the planned and postoperative models were registered at the mandibular body. Statistical analyses were performed, and the accuracy was reported using root mean square deviation (RMSD) and the Bland-Altman method for assessing measurement agreement. RESULTS: In the primary outcome measurements, there was no statistically significant difference among the 3 centers for the maxilla and mandible. The largest RMSDs were 1.0 mm and 1.5° for the maxilla and 1.1 mm and 1.8° for the mandible. For the chin, there was a statistically significant difference between the groups with and without the use of the chin template. The chin template group showed excellent accuracy, with the largest positional RMSD of 1.0 mm and the largest orientation RMSD of 2.2°. However, larger variances were observed in the group not using the chin template. This was significant in the anteroposterior and superoinferior directions and the in pitch and yaw orientations. In the secondary outcome measurements, the RMSD of the maxillary dental midline positions was 0.9 mm. When registered at the body of the mandible, the linear and angular differences of the chin segment between the groups with and without the use of the chin template were consistent with the results found in the primary outcome measurements. CONCLUSIONS: Using this computer-aided surgical simulation protocol, the computerized plan can be transferred accurately and consistently to the patient to position the maxilla and mandible at the time of surgery. The computer-generated chin template provides greater accuracy in repositioning the chin segment than the intraoperative measurements.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 06/2012; · 1.58 Impact Factor
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    ABSTRACT: Advancements in Cone Beam Computed Tomography (CBCT) have improved localization of impacted canines. The KPG index is the first 3-D classification system for classifying the position of canines based on their distance from the norm (1). The aim of this study was to determine if this index provides an estimate of the time necessary to treat an impacted canine using closed eruption. CBCT scans of 28 impacted canines at The University of Texas School of Dentistry at Houston Department of Orthodontics were classified using the KPG index. The scores and categories were compared to the time from surgical exposure to proper positioning. Four canines were classified as "Easy," 11 as "Moderate," 9 as "Difficult," and 4 as "Extremely Difficult." Average treatment times associated in months were: "Easy"--11.23, "Moderate"--11.36, "Difficult"--12.76, and "Extremely Difficult"--13.23. The KPG index currently cannot be confirmed as an accurate means of estimating treatment time for an impacted canine. Further verification studies should include larger sample sizes and compare differing mechanics. However, there are limitations to 2-D imaging; therefore, the 3-D CBCT images and the KPG index, with further validation, will become increasingly valuable to orthodontists.
    Texas dental journal 03/2012; 129(3):265-74.
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    ABSTRACT: This paper proposes a nonlinear regression model to predict soft tissue deformation after maxillofacial surgery. The feature which served as input in the model is extracted with finite element model (FEM). The output in the model is the facial deformation calculated from the preoperative and postoperative 3D data. After finding the relevance between feature and facial deformation by using the regression model, we establish a general relationship which can be applied to all the patients. As a new patient comes, we predict his/her facial deformation by combining the general relationship and the new patient's biomechanical properties. Thus, our model is biomechanical relevant and statistical relevant. Validation on eleven patients demonstrates the effectiveness and efficiency of our method.
    Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention. 01/2012; 15(Pt 1):99-106.
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    ABSTRACT: The success of cranio-maxillofacial (CMF) surgery depends not only on surgical techniques, but also upon an accurate surgical plan. Unfortunately, traditional planning methods are often inadequate for planning complex cranio-maxillofacial deformities. To this end, we developed 3D computer-aided surgical simulation (CASS) technique. Using our CASS method, we are able to treat patients with significant asymmetries in a single operation which in the past was usually completed in two stages. The purpose of this article is to introduce our CASS method in evaluating craniofacial deformities and planning surgical correction. In addition, we discuss the problems associated with the traditional surgical planning methods. Finally, we discuss the strength and pitfalls of using three-dimensional measurements to evaluate craniofacial deformity.
    Seminars in Orthodontics 09/2011; 17(3):225-234.
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    ABSTRACT: The purpose of the present study was to evaluate the accuracy of our newly developed approach to digital dental model articulation. Twelve sets of stone dental models from patients with craniomaxillofacial deformities were used for validation. All the models had stable occlusion and no evidence of early contact. The stone models were hand articulated to the maximal intercuspation (MI) position and scanned using a 3-dimensional surface laser scanner. These digital dental models at the MI position served as the control group. To establish an experimental group, each mandibular dental model was disarticulated from its original MI position to 80 initial positions. Using a regular office personal computer, they were digitally articulated to the MI position using our newly developed approach. These rearticulated mandibular models served as the experimental group. Finally, the translational, rotational, and surface deviations in the mandibular position were calculated between the experimental and control groups, and statistical analyses were performed. All the digital dental models were successfully articulated. Between the control and experimental groups, the largest translational difference in mandibular position was within 0.2 mm ± 0.6 mm. The largest rotational difference was within 0.1° ± 1.1°. The averaged surface deviation was 0.08 ± 0.07. The results of the Bland and Altman method of assessing measurement agreement showed tight limits for the translational, rotational, and surface deviations. In addition, the final positions of the mandibular articulated from the 80 initial positions were absolutely agreed on. The results of our study have demonstrated that using our approach, the digital dental models can be accurately and effectively articulated to the MI position. In addition, the 3-dimensional surface geometry of the mandibular teeth played a more important role in digital dental articulation than the initial position of the mandibular teeth.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 07/2011; 70(4):952-62. · 1.58 Impact Factor
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    ABSTRACT: The purpose of this study was to determine whether the surgical outcomes achieved with computer-aided surgical simulation (CASS) are better than those achieved with traditional methods. Twelve consecutive patients with craniomaxillofacial (CMF) deformities were enrolled. According to the CASS clinical protocol, a 3-dimensional computer composite skull model for each patient was generated and reoriented to the neutral head posture. These models underwent 2 virtual surgeries: 1 was based on CASS (experimental group) and the other was based on traditional methods 1 year later (control group). Once the 2 virtual surgeries were completed, 2 experienced oral and maxillofacial surgeons at 2 different settings evaluated the 2 surgical outcomes. They were blinded to the planning method used on the virtual models and each other's evaluation results. The primary outcome was overall CMF skeletal harmony. The secondary outcomes were individual maxillary, mandibular, and chin harmonies. Statistical analyses were performed. Overall CMF skeletal harmony achieved with CASS was statistically significantly better than that achieved with traditional methods. In addition, the maxillary and mandibular surgical outcomes achieved with CASS were significantly better. Furthermore, although not included in the statistical model, the chin symmetry achieved by CASS tended to be better. A regression model was established between mandibular symmetry and overall CMF skeletal harmony. The surgical outcomes achieved with CASS are significantly better than those achieved with traditional planning methods. In addition, CASS enables the surgeon to better correct maxillary yaw deformity, better place proximal/distal segments, and better restore mandibular symmetry. The critical step in achieving better overall CMF skeletal harmony is to restore mandibular symmetry.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 07/2011; 69(7):2014-24. · 1.58 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the clinical feasibility of a new method to orient 3-dimensional (3D) computed tomography models to the natural head position (NHP). This method uses a small and inexpensive digital orientation device to record NHP in 3 dimensions. This device consists of a digital orientation sensor attached to the patient via a facebow and an individualized bite jig. The study was designed to answer 2 questions: 1) whether the weight of the new device can negatively influence the NHP and 2) whether the new method is as accurate as the gold standard. Fifteen patients with craniomaxillofacial deformities were included in the study. Each patient's NHP is recorded 3 times. The first NHP was recorded with a laser scanning method without the presence of the digital orientation device. The second NHP was recorded with the digital orientation device. Simultaneously, the third NHP was also recorded with the laser scanning method. Each recorded NHP measurement was then transferred to the patient's 3D computed tomography facial model, resulting in 3 different orientations for each patient: the orientation generated via the laser scanning method without the presence of the digital orientation sensor and facebow (orientation 1), the orientation generated by use of the laser scanning method with the presence of the digital orientation sensor and facebow (orientation 2), and the orientation generated with the digital orientation device (orientation 3). Comparisons are then made between orientations 1 and 2 and between orientations 2 and 3, respectively. Statistical analyses are performed. The results show that in each pair, the difference (Δ) between the 2 measurements is not statistically significantly different from 0°. In addition, in the first pair, the Bland-Altman lower and upper limits of the Δ between the 2 measurements are within 1.5° in pitch and within a subdegree in roll and yaw. In the second pair, the limits of the Δ in all 3 dimensions are within 0.5°. Our technique can accurately record NHP in 3 dimensions and precisely transfer it to a 3D model. In addition, the extra weight of the digital orientation sensor and facebow has minimal influence on the self-balanced NHP establishment.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 03/2011; 69(3):584-91. · 1.58 Impact Factor
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    ABSTRACT: To test the hypothesis that facial symmetry affects both 2-dimensional (2D) and 3-dimensional (3D) cephalometric measurements. A baseline model of a preferred symmetrical face was first constructed. It consisted of a set of commonly used cephalometric landmarks. Seven cephalometric measurements were selected for testing. Each of them represented a different set of geometrical conditions related to the geometric parameters being measured, the elements involved, and the type of measurements. They served as a control group. The baseline model was then modified to simulate 10 different asymmetric models, 6 with maxillary asymmetries and 4 with mandibular asymmetries. The same 7 cephalometric analysis were utilized again on each of the 10 asymmetric models. They served as an experimental group. The resulted measurements were tabulated and compared. For the measurements of shape, the 2D cephalometric measurement was distorted by roll and yaw asymmetries, while the same measurement in 3D was not. For the measurements of size, the 2D measurement was also distorted by yaw, but not by roll, while again this measurement in 3D was not distorted. For measurements of position, the results were reversed. The 2D cephalometric measurements of position were not distorted, while all measurements in 3D were distorted. Of note, the magnitude of the distortion was much larger for the linear measurement than angular measurement. Finally, measurements of orientation, both 2D and 3D measurements were distorted by asymmetry, although the magnitude of the distortion was larger for the 3D measurements. This study confirmed the hypothesis that facial asymmetry affects both 2D and 3D cephalometric measurements. It also demonstrated that the effects of asymmetry on cephalometric measurements depend on the geometric parameter being measured (ie, shape, size, position, or orientation).
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 03/2011; 69(3):655-62. · 1.58 Impact Factor
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    ABSTRACT: Two basic problems have been associated with traditional 2-dimensional cephalometry. First, many important parameters cannot be measured on plain cephalograms; and second, most 2-dimensional cephalometric measurements are distorted in the presence of facial asymmetry. Three-dimensional cephalometry, which has been facilitated by the introduction of cone-beam computed tomography, can solve these problems. However, before this can be realized, fundamental problems must be solved. These include the unreliability of internal reference systems and some 3-dimensional measurements, and the lack of tools to assess and measure the symmetry. In the present report, we present a new 3-dimensional cephalometric analysis that uses different geometric approaches to solve these fundamental problems. The present analysis allows the accurate measurement of the size, shape, position, and orientation of the different facial units and incorporates a novel method to measure asymmetry.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 01/2011; 69(3):606-22. · 1.58 Impact Factor
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    ABSTRACT: The purpose of this study was to evaluate the long-term effectiveness of presurgical nasoalveolar molding (PNAM) in patients with unilateral cleft lip and palate (UCLP). Twenty-five patients with UCLP treated by either PNAM or non-PNAM therapy between 1998 and 2003 were recruited in the study. During the clinical examination and data analysis, the evaluators were blinded to which patients received PNAM. The patients were reviewed clinically, and their facial morphology was captured with a three-dimensional scanner. Their dental arch configuration and occlusion were recorded by plaster dental models. After the patient evaluations and measurements were completed, the patient list was unblinded. There were 20 patients in the PNAM group and 5 patients in the non-PNAM group. Fisher exact tests and Wilcoxon rank sum tests were used to compare the outcomes. Clinically, the improvement in the PNAM group was most evident in nasal and lip anatomy. However, there were no statistically significant differences between the 2 groups on each of the measurements on three-dimensional facial images and dental models. Our study suggests a trend toward a long-term clinical improvement in nasal and lip anatomy of UCLP patients treated with PNAM. However, these improved results were not confirmed by three-dimensional stereophotography. There was no statistically significant difference in the long-term three-dimensional anthropometric measurements and dental model analysis between the PNAM group and the non-PNAM group.
    The Journal of craniofacial surgery 01/2011; 22(1):333-6. · 0.81 Impact Factor
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    ABSTRACT: The purpose of this study was to determine whether cone beam digital models are as accurate as OrthoCAD (Cadent, Inc, Carlstadt, NJ) digital models for the purposes of orthodontic diagnosis and treatment planning. Digital records of 30 subjects were retrospectively reviewed, and the digital models were obtained as OrthoCAD and InVivoDental (San Jose, CA) digital models. Seven parameters indicating linear measurements from predetermined landmarks were measured and analyzed. The analysis of variance and Bland and Altman Analysis were used to compare and evaluate measurements made from the study models generated from cone beam computed tomography (CBCT) and InVivoDental software. The mean difference between the maxillary InVivoDental models and the maxillary OrthoCAD models ranged from −0.57 to 0.44 mm. The analysis of variance for repeated measures (P < 0.001) was applied to all data obtained from the CBCT and OrthoCAD models. The results indicated a mean score of 35.12 and 35.12 mm, respectively. The mean difference of all values was −7.93 × 10−3 mm. The range of these values at the 95% confidence interval was −0.14 and 0.12 mm for the lower and upper limits, respectively. The results were not statistically significant for both groups. The Bland and Altman analysis was also applied to the data. In the maxilla, the results indicated that the mean difference between InVivoDental and OrthoCAD was −0.01 ± 1.24 mm. The range of the analysis indicated a spread of −2.40 mm and +2.40 mm. In the mandible, the results indicated that the mean difference between InVivoDental and OrthoCAD was −0.01 ± 1.21 mm. The range of the analysis indicated a spread of −2.36 mm and +2.37 mm. The results showed that the linear measurements obtained from CBCT image casts indicated a good level of accuracy when compared with OrthoCAD models. The accuracy was considered adequate for initial diagnosis and treatment planning in orthodontics.
    Seminars in Orthodontics 01/2011; 17(1):49-56.
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    ABSTRACT: Rapid maxillary expansion (RME) splits the midpalatal suture to correct maxillary transverse discrepancies and increase the arch perimeter. The goal of this paper is to evaluate the immediate effects of RME with Hyrax appliances on the dentoalveolar complex using cone beam computed tomography (CBCT). Twenty-eight patients (19 females and 9 males) requiring maxillary expansion therapy were included (mean age, 14.1 years; range, 13 to 20 years). CBCT images were taken at T1 (before maxillary expansion) and T2 (immediately after expansion) as part of clinical records. Maxillary arch width, posterior segment angulation, and buccal bone thickness at the level of the first premolar and first molar were evaluated. Paired t tests determined statistical significance (P < .05). The mean ± SD amount of expansion achieved was 4.7788 ± 2.8474 mm for the maxillary premolars and 4.6943 ± 3.2198 mm for the molars. Significant tipping of the palatal roots of the maxillary right and left premolars as well as that for the maxillary left molar was observed. When present, the thickness of the buccal plate decreased on all observed roots. There is a significant increase in interpremolar and intermolar distance with RME. The increase in root angulation suggests that the movement is more tipping than translation. The thickness of the buccal plate decreases immediately after RME. Therefore, the level of inflammation should be closely monitored to avoid periodontal destruction. There is a need to define standardized reference planes and comparable methodology to achieve compatible results among studies.
    Orthodontics : the art and practice of dentofacial enhancement. 01/2011; 12(3):202-9.
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    ABSTRACT: The purpose of this study was to develop a motion simulator capable of recreating and recording the full range of mandibular motions in a cadaveric preparation for an intact temporomandibular joint (TMJ) and after total joint replacement. A human cadaver head was used. Two sets of tracking balls were attached to the forehead and mandible, respectively. Computed tomographic (CT) scan was performed and 3-dimensional CT models of the skull were generated. The cadaver head was then dissected to attach the muscle activation cables and mounted onto the TMJ simulator. Realistic jaw motions were generated through the application of the following muscle forces: lateral pterygoid muscle, suprahyoid depressors (geniohyoid, mylohyoid, and digastric muscles), and elevator muscles. To simulate muscle contraction, cables were inserted into the mandible at the center area of each muscle's attachment. To provide a minimum mouth closing force at the initial position, the elevator muscles were combined at the anterior mandible. During mandibular movement, each motion was recorded using a high-resolution laser scanner. The right TMJ of the same head was reconstructed with a total TMJ prosthesis. The same forces were applied and the jaw motions were recorded again. CT scan was performed and 3-dimensional CT models of the skull with TMJ prosthesis were generated. Mandibular motions, before and after TMJ replacement, with and without lateral pterygoid muscle reattachment, were re-created in a cadaveric preparation. The laser-scanned data during the mandibular motion were used to drive 3-dimensional CT models. A movie for each mandibular motion was subsequently created for motion path analysis. Compared with mandibular motion before TMJ replacement, mandibular lateral and protrusive motions after TMJ replacement, with and without lateral pterygoid muscle reattachment, were greatly limited. The jaw motion recorded before total joint replacement was applied to the mandibular and prostheses models after total TMJ replacement. The condylar component was observed sinking into the fossa during jaw motion. A motion simulator capable of re-creating and recording full range of mandibular motions in a cadaveric preparation has been developed. It can be used to simulate mandibular motions for the intact TMJ and total joint prosthesis, and to re-create and record their full range of mandibular motions. In addition, the full range of the recorded motion can be re-created as motion images in a computer. These images can be used for motion path analysis and to study the causation of limited range of motion after total joint replacement and strategies for improvement.
    Journal of oral and maxillofacial surgery: official journal of the American Association of Oral and Maxillofacial Surgeons 11/2010; 69(1):66-79. · 1.58 Impact Factor
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    ABSTRACT: In the field of craniomaxillofacial (CMF) surgery, surgical planning can be performed on composite 3-D models that are generated by merging a computerized tomography scan with digital dental models. Digital dental models can be generated by scanning the surfaces of plaster dental models or dental impressions with a high-resolution laser scanner. During the planning process, one of the essential steps is to reestablish the dental occlusion. Unfortunately, this task is time-consuming and often inaccurate. This paper presents a new approach to automatically and efficiently reestablish dental occlusion. It includes two steps. The first step is to initially position the models based on dental curves and a point matching technique. The second step is to reposition the models to the final desired occlusion based on iterative surface-based minimum distance mapping with collision constraints. With linearization of rotation matrix, the alignment is modeled by solving quadratic programming. The simulation was completed on 12 sets of digital dental models. Two sets of dental models were partially edentulous, and another two sets have first premolar extractions for orthodontic treatment. Two validation methods were applied to the articulated models. The results show that using our method, the dental models can be successfully articulated with a small degree of deviations from the occlusion achieved with the gold-standard method.
    IEEE transactions on medical imaging. 09/2010; 29(9):1652-63.
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    ABSTRACT: The purpose of this study was to develop and test a new technique for recording natural head position (NHP) in 3 dimensions and transferring it into a three-dimensional computed tomography (CT) model. In this technique, a digital gyroscope was first attached to a human head using a bite-jig and a face-bow with a set of built-in fiducial markers. The relationship between the gyroscope and fiducial markers was predetermined and kept constant. The orientation (pitch, roll, and yaw) of the head was then recorded by this gyroscope. In next step, the head was CT scanned with the bite-jig and the face-bow in place, and three-dimensional CT models of the head and fiducial markers were generated. The head model was coupled with a predetermined three-dimensional model of the gyroscope assembly via fiducial markers. The three-dimensional head model was reoriented to the recorded orientation by applying the recorded pitch, roll, and yaw to the gyroscope model. Finally, the accuracy of the technique was tested on a human dry skull. The results showed that the NHP was successfully recorded and transferred to the three-dimensional CT model. The orientations between the dry skull and its three-dimensional computer model were absolutely correlated. The difference (the lack of agreement) was within a range of -1.1 to 1.1 degrees, indicating no clinical significance. The authors concluded that our technique could accurately and repeatedly record NHP three-dimensionally and transfer it to a three-dimensional CT head model.
    The Journal of craniofacial surgery 09/2010; 21(5):1452-5. · 0.81 Impact Factor

Publication Stats

588 Citations
55.97 Total Impact Points

Institutions

  • 2013
    • Texas A&M University
      • Department of Electrical and Computer Engineering
      College Station, TX, United States
  • 2011–2013
    • Cornell University
      Ithaca, New York, United States
  • 2012
    • Chang Gung Memorial Hospital
      T’ai-pei, Taipei, Taiwan
  • 2008–2012
    • Houston Methodist Hospital
      Houston, Texas, United States
  • 2003–2011
    • University of Texas Health Science Center at Houston
      • • Department of Otolaryngology - Head and Neck Surgery
      • • Department of Pediatric Surgery
      • • Department of Orthodontics
      • • Division of Oral and Maxillofacial Surgery
      • • Medical School
      • • Department of Surgery
      Houston, TX, United States
  • 2005–2008
    • Rice University
      • Department of Bioengineering
      Houston, TX, United States
  • 2006–2007
    • University of Texas Health Science Center at Tyler
      Tyler, Texas, United States
  • 2004
    • Center For Oral & Maxillofacial Surgery
      Georgia, United States
  • 2002–2004
    • University of Texas Medical School
      • Department of Surgery
      Houston, Texas, United States