Tung Nguyen

Three-dimensional assessment of maxillary changes associated with bone anchored maxillary protraction

INTRODUCTION Bone-anchored maxillary protraction has been shown to be an effective treatment modality for the correction of Class III malocclusions. The purpose of this study was to evaluate 3-dimensional changes in the maxilla, the surrounding hard and soft tissues, and the circummaxillary sutures after bone-anchored maxillary protraction treatment. METHODS Twenty-five consecutive skeletal Class III patients between the ages of 9 and 13 years (mean, 11.10 ± 1.1 years) were treated with Class III intermaxillary elastics and bilateral miniplates (2 in the infrazygomatic crests of the maxilla and 2 in the anterior mandible). Cone-beam computed tomographs were taken before initial loading and 1 year out. Three-dimensional models were generated from the tomographs, registered on the anterior cranial base, superimposed, and analyzed by using color maps. RESULTS The maxilla showed a mean forward displacement of 3.7 mm, and the zygomas and the maxillary incisors came forward 3.7 and 4.3 mm, respectively. CONCLUSIONS This treatment approach produced significant orthopedic changes in the maxilla and the zygomas in growing Class III patients.

Three-dimensional assessment of mandibular and glenoid fossa changes after bone-anchored Class III intermaxillary traction

INTRODUCTION Conventional treatment for young Class III patients involves extraoral devices designed to either protract the maxilla or restrain mandibular growth. The use of skeletal anchorage offers a promising alternative to obtain orthopedic results with fewer dental compensations. Our aim was to evaluate 3-dimensional changes in the mandibles and the glenoid fossae of Class III patients treated with bone-anchored maxillary protraction. METHODS Twenty-five consecutive skeletal Class III patients between the ages of 9 and 13 years (mean age, 11.10 ± 1.1 year) were treated with Class III intermaxillary elastics and bilateral miniplates (2 in the infrazygomatic crests of the maxilla and 2 in the anterior mandible). The patients had cone-beam computed tomography images taken before initial loading and at the end of active treatment. Three-dimensional models were generated from these images, registered on the anterior cranial base, and analyzed by using color maps. RESULTS Posterior displacement of the mandible at the end of treatment was observed in all subjects (posterior ramus: mean, 2.74 ± 1.36 mm; condyles: mean, 2.07 ± 1.16 mm; chin: mean, -0.13 ± 2.89 mm). Remodeling of the glenoid fossa at the anterior eminence (mean, 1.38 ± 1.03 mm) and bone resorption at the posterior wall (mean, -1.34 ± 0.6 mm) were observed in most patients. CONCLUSIONS This new treatment approach offers a promising alternative to restrain mandibular growth for Class III patients with a component of mandibular prognathism or to compensate for maxillary deficiency in patients with hypoplasia of the midface. Future studies with long-term follow-up and comparisons with facemask and chincup therapies are needed to better understand the treatment effects.

Three-dimensional analysis of maxillary changes associated with facemask and rapid maxillary expansion compared with bone anchored maxillary protraction

INTRODUCTION Our objectives in this study were to evaluate in 3 dimensions the growth and treatment effects on the midface and the maxillary dentition produced by facemask therapy in association with rapid maxillary expansion (RME/FM) compared with bone-anchored maxillary protraction (BAMP). METHODS Forty-six patients with Class III malocclusion were treated with either RME/FM (n = 21) or BAMP (n = 25). Three-dimensional models generated from cone-beam computed tomographic scans, taken before and after approximately 1 year of treatment, were registered on the anterior cranial base and measured using color-coded maps and semitransparent overlays. RESULTS The skeletal changes in the maxilla and the right and left zygomas were on average 2.6 mm in the RME/FM group and 3.7 mm in the BAMP group; these were different statistically. Seven RME/FM patients and 4 BAMP patients had a predominantly vertical displacement of the maxilla. The dental changes at the maxillary incisors were on average 3.2 mm in the RME/FM group and 4.3 mm in the BAMP group. Ten RME/FM patients had greater dental compensations than skeletal changes. CONCLUSIONS This 3-dimensional study shows that orthopedic changes can be obtained with both RME/FM and BAMP treatments, with protraction of the maxilla and the zygomas. Approximately half of the RME/FM patients had greater dental than skeletal changes, and a third of the RME/FM compared with 17% of the BAMP patients had a predominantly vertical maxillary displacement.

3D osteoarthritic changes in TMJ condylar morphology correlates with specific systemic and local biomarkers of disease

OBJECTIVE To assess 3D morphological variations and local and systemic biomarker profiles in subjects with a diagnosis of temporomandibular joint osteoarthritis (TMJ OA). DESIGN Twenty-eight patients with long-term TMJ OA (39.9 ± 16 years), 12 patients at initial diagnosis of OA (47.4 ± 16.1 years), and 12 healthy controls (41.8 ± 12.2 years) were recruited. All patients were female and had cone beam CT scans taken. TMJ arthrocentesis and venipuncture were performed on 12 OA and 12 age-matched healthy controls. Serum and synovial fluid levels of 50 biomarkers of arthritic inflammation were quantified by protein microarrays. Shape Analysis MANCOVA tested statistical correlations between biomarker levels and variations in condylar morphology. RESULTS Compared with healthy controls, the OA average condyle was significantly smaller in all dimensions except its anterior surface, with areas indicative of bone resorption along the articular surface, particularly in the lateral pole. Synovial fluid levels of ANG, GDF15, TIMP-1, CXCL16, MMP-3 and MMP-7 were significantly correlated with bone apposition of the condylar anterior surface. Serum levels of ENA-78, MMP-3, PAI-1, VE-Cadherin, VEGF, GM-CSF, TGFβb1, IFNγg, TNFαa, IL-1αa, and IL-6 were significantly correlated with flattening of the lateral pole. Expression levels of ANG were significantly correlated with the articular morphology in healthy controls. CONCLUSIONS Bone resorption at the articular surface, particularly at the lateral pole was statistically significant at initial diagnosis of TMJ OA. Synovial fluid levels of ANG, GDF15, TIMP-1, CXCL16, MMP-3 and MMP-7 were correlated with bone apposition. Serum levels of ENA-78, MMP-3, PAI-1, VE-Cadherin, VEGF, GM-CSF, TGFβ1, IFNγ, TNFα, IL-1α, and IL-6 were correlated with bone resorption.

Regional 3D superimposition to assess temporomandibular joint condylar morphology

OBJECTIVES To investigate the reliability of regional three-dimensional registration and superimposition methods for assessment of temporomandibular joint condylar morphology across subjects and longitudinally. METHODS The sample consisted of cone beam CT scans of 36 patients. The across-subject comparisons included 12 controls, mean age 41.3 ± 12.0 years, and 12 patients with temporomandibular joint osteoarthritis, mean age 41.3 ± 14.7 years. The individual longitudinal assessments included 12 patients with temporomandibular joint osteoarthritis, mean age 37.8 ± 16.7 years, followed up at pre-operative jaw surgery, immediately after and one-year post-operative. Surface models of all condyles were constructed from the cone beam CT scans. Two previously calibrated observers independently performed all registration methods. A landmark-based approach was used for the registration of across-subject condylar models, and temporomandibular joint osteoarthritis vs control group differences were computed with shape analysis. A voxel-based approach was used for registration of longitudinal scans calculated x, y, z degrees of freedom for translation and rotation. Two-way random intraclass correlation coefficients tested the interobserver reliability. RESULTS Statistically significant differences between the control group and the osteoarthritis group were consistently located on the lateral and medial poles for both observers. The interobserver differences were ≤0.2 mm. For individual longitudinal comparisons, the mean interobserver differences were ≤0.6 mm in translation errors and 1.2° in rotation errors, with excellent reliability (intraclass correlation coefficient >0.75). CONCLUSIONS Condylar registration for across-subjects and longitudinal assessments is reliable and can be used to quantify subtle bony differences in the three-dimensional condylar morphology.

Use of shape correspondence analysis to quantify skeletal changes associated with bone-anchored Class III correction

OBJECTIVE To evaluate the three-dimensional (3D) skeletal changes in the mandibles of Class III patients treated with bone-anchored maxillary protraction using shape correspondence analysis. MATERIAL AND METHOD Twenty-five consecutive patients with skeletal Class III who were between the ages of 9 and 13 years (mean age, 11.10 ± 1.1 years) were treated using Class III intermaxillary elastics and bilateral miniplates (two in the infrazygomatic crests of the maxilla and two in the anterior mandible). Cone-beam computed tomography (CBCT) was performed for each patient before initial loading (T1) and at 1 year out (T2). From the CBCT scans, 3D models were generated, registered on the anterior cranial base, and analyzed using 3D linear distances and vectors between corresponding point-based surfaces. RESULTS Bone-anchored traction produced anteroposterior and vertical skeletal changes in the mandible. The novel application of Shape correspondence analysis showed vectors of mean (± standard deviation) distal displacement of the posterior ramus of 3.6 ± 1.4 mm, while the chin displaced backward by 0.5 ± 3.92 mm. The lower border of the mandible at the menton region was displaced downward by 2.6 ± 1.2 mm, and the lower border at the gonial region moved downward by 3.6 ± 1.4 mm. There was a downward and backward displacement around the gonial region with a mean closure of the gonial angle by 2.1°. The condyles were displaced distally by a mean of 2.6 ± 1.5 mm, and there were three distinct patterns for displacement: 44% backward, 40% backward and downward, and 16% backward and upward. CONCLUSION This treatment approach induces favorable control of the mandibular growth pattern and can be used to treat patients with components of mandibular prognathism.

3D Mandibular Superimposition: Comparison of Regions of Reference for Voxel-Based Registration.

Introduction The aim was to evaluate three regions of reference (Björk, Modified Björk and mandibular Body) for mandibular registration testing them in a patients’ CBCT sample. Methods Mandibular 3D volumetric label maps were built from CBCTs taken before (T1) and after treatment (T2) in a sample of 16 growing subjects and labeled with eight landmarks. Registrations of T1 and T2 images relative to the different regions of reference were performed, and 3D surface models were generated. Seven mandibular dimensions were measured separately for each time-point (T1 and T2) in relation to a stable reference structure (lingual cortical of symphysis), and the T2-T1 differences were calculated. These differences were compared to differences measured between the superimposed T2 (generated from different regions of reference: Björk, Modified Björk and Mandibular Body) over T1 surface models. ICC and the Bland-Altman method tested the agreement of the changes obtained by nonsuperimposition measurements from the patients’ sample, and changes between the overlapped surfaces after registration using the different regions of reference. Results The Björk region of reference (or mask) did work properly only in 2 of 16 patients. Evaluating the two other masks (Modified Björk and Mandibular body) on patients’ scans registration, the concordance and agreement of the changes obtained from superimpositions (registered T2 over T1) compared to results obtained from non superimposed T1 and T2 separately, indicated that Mandibular Body mask displayed more consistent results. Conclusions The mandibular body mask (mandible without teeth, alveolar bone, rami and condyles) is a reliable reference for 3D regional registration.

Comparison and reproducibility of 2 regions of reference for maxillary regional registration with cone-beam computed tomography.

INTRODUCTION The aims of this study were to evaluate the differences between 2 regions of maxillary voxel-based registration and to test the reproducibility of the registration. METHODS Three-dimensional models were built for before-treatment (T1) and after-treatment (T2) based on cone-beam computed tomography images from 16 growing subjects. Landmarks were labeled in all T2 models of the maxilla, and voxel-based registrations were performed independently by 2 observers at 2 times using 2 reference regions. The first region, the maxillary region, included the maxillary bone clipped inferiorly at the dentoalveolar processes, superiorly at the plane passing through the right and left orbitale points, laterally at the zygomatic processes through the orbitale point, and posteriorly at a plane passing through the distal surface of the second molars. In the second region, the palate and infrazygomatic region had different posterior and anterior limits (at the plane passing through the distal aspects of the first molars and the canines, respectively). The differences between the registration regions were measured by comparing the distances between corresponding landmarks in the T2 registered models and comparing the corresponding x, y, and z coordinates from corresponding landmarks. Statistical analysis of the differences between the T2 surface models was performed by evaluating the means and standard deviations of the distances between landmarks and by testing the agreement between coordinates from corresponding landmarks (intraclass correlation coefficient and Bland-Altman method). RESULTS The means of the differences between landmarks from the palate and infrazygomatic region to the maxillary region 3-dimensional surface models at T2 for all regions of reference, times of registrations, and observer combinations were smaller than 0.5 mm. The intraclass correlation coefficient and the Bland-Altman plots indicated adequate concordance. CONCLUSIONS The 2 regions of regional maxillary registration showed similar results and adequate intraobserver and interobserver reproducibility values.

Effect of Class III bone anchor treatment on airway

OBJECTIVES To compare airway volumes and minimum cross-section area changes of Class III patients treated with bone-anchored maxillary protraction (BAMP) versus untreated Class III controls. MATERIALS AND METHODS Twenty-eight consecutive skeletal Class III patients between the ages of 10 and 14 years (mean age, 11.9 years) were treated using Class III intermaxillary elastics and bilateral miniplates (two in the infra-zygomatic crests of the maxilla and two in the anterior mandible). The subjects had cone beam computed tomographs (CBCTs) taken before initial loading (T1) and 1 year out (T2). Twenty-eight untreated Class III patients (mean age, 12.4 years) had CBCTs taken and cephalograms generated. The airway volumes and minimum cross-sectional area measurements were performed using Dolphin Imaging 11.7 3D software. The superior border of the airway was defined by a plane that passes through the posterior nasal spine and basion, while the inferior border included the base of the epiglottis to the lower border of C3. RESULTS From T1 to T2, airway volume from BAMP-treated subjects showed a statistically significant increase (1499.64 mm(3)). The area in the most constricted section of the airway (choke point) increased slightly (15.44 mm(2)). The airway volume of BAMP patients at T2 was 14136.61 mm(3), compared with 14432.98 mm(3) in untreated Class III subjects. Intraexaminer correlation coefficients values and 95% confidence interval values were all greater than .90, showing a high degree of reliability of the measurements. CONCLUSION BAMP treatment did not hinder the development of the oropharynx.

Effectiveness and efficiency of a CAD/CAM orthodontic bracket system

INTRODUCTION The first straight-wire appliance was introduced over 40 years ago to increase the consistency and efficiency of orthodontic treatment. More recently, computer-aided design and computer-aided manufacturing (CAD/CAM) technology has been used to create individualized orthodontic appliances. The purpose of this study was to investigate the clinical effectiveness and efficiency of CAD/CAM customized orthodontic appliances compared with direct and indirect bonded stock orthodontic brackets. METHODS This retrospective study included 3 treatment groups: group 1 patients were direct bonded with self-ligating appliances, group 2 patients were indirect bonded with self-ligating appliances, and group 3 patients were indirect bonded with CAD/CAM self-ligating appliances. Complete pretreatment and posttreatment records were obtained for all patients. The American Board of Orthodontics (ABO) Discrepancy Index was used to evaluate the pretreatment records, and the posttreatment outcomes were analyzed using the ABO Cast-Radiograph Evaluation. All data collection and analysis were completed by 1 evaluator. RESULTS There were no statistically significant differences in the ABO Discrepancy Index or the ABO Cast-Radiograph Evaluation among the groups. Treatment times for the 3 groups were significantly different; the CAD/CAM group was the shortest at 13.8 ± 3.4 months, compared with 21.9 ± 5.0 and 16.9 ± 4.1 months for the direct bonded and indirect bonded groups, respectively. The number of treatment appointments for the CAD/CAM group was significantly fewer than for the direct bonded group. CONCLUSIONS The CAD/CAM orthodontic bracket system evaluated in this study was as effective in treatment outcome measures as were standard brackets bonded both directly and indirectly. The CAD/CAM appliance was more efficient in regard to treatment duration, although the decrease in total archwire appointments was minimal. Further investigation is needed to better quantify the clinical benefits of CAD/CAM orthodontic appliances.