Comparison of two 3-dimensional user-friendly voxel-based maxillary and 2-dimensional superimposition methods.

INTRODUCTION: Cephalometric superimpositions have many uses in orthodontics, including growth evaluation and outcome assessment. However, 2-dimensional (2D) cephalograms can be distorted and yield incomplete 2D data. Cone-beam computed tomography (CBCT) imaging provides a 3-dimensional (3D), undistorted, and more complete patient analysis. CBCT imaging provides many unique advantages to the orthodontic practice and can influence how treatment outcomes are assessed. This study aimed to investigate the validity of 3D maxillary voxel-based superimpositions compared with the 2D method recommended by the American Board of Orthodontists. METHODS: This retrospective study included pretreatment and posttreatment CBCT images of 30 adolescent patients. The images were superimposed using the 3D voxel-based tools in Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). Two different 3D anatomic registration areas (3DA-3DB) were tested for the validity and reproducibility of the 3D maxillary superimpositions as compared with the 2D method. Linear and angular measurements were used to evaluate the dental changes of the maxillary right central incisor and first molar. Data distribution was normal by the Shapiro-Wilk W test. A mixed model analysis of variance test was done to compare the 3 superimposition types within each subject, followed by pairwise Tukey-Kramer comparisons when indicated. RESULTS: After applying the Benjamini-Hochberg procedure to control the false discovery rate at 0.05 with multiple testing, the U1 vertical difference was statistically significant (P <0.0001) for the superimposition method, though the mean differences were clinically nonsignificant (0.52 mm, 0.76 mm). The U1 angular and U6 vertical differences were not statistically significant for the superimposition method (P = 0.3636 and P = 0.1863, respectively). CONCLUSIONS: The 3D voxel-based maxillary superimpositions showed similar results to conventional 2D superimpositions recommended by the American Board of Orthodontists.

The Relationship Between Dental Agenesis and Maxillary Hypoplasia in Patients With Cleft Lip and Palate.

ABSTRACT: Both dental agenesis and maxillary growth restriction are well-recognized sequelae in patients with unilateral cleft lip and palate, but their etiology remains controversial. The aim of this study was to evaluate the relationship between hypodontia and maxillary volume. A retrospective review of patients age 6 to 9 with Veau III (unilateral) cleft palate who underwent Cone Beam Computer Tomography in preparation for alveolar bone grafting at 2 major Children's Hospitals between 2010 and 2016 was conducted and serial panoramic radiographs were reviewed. Thirty-eight patients were identified that met inclusion criteria and had adequate imaging. Group 1 ("poor growers") consisted of the bottom 50% of Sella-Nasion-A point minus Sella-Nasion-B point (ANB) angles and Group 2 ("good growers") consisted of the top 50% of ANB angles. Group 1 had a significantly higher mean number of missing teeth (1.58 ±â€Š0.28 missing teeth) compared to Group 2 (0.74 ±â€Š0.23 missing teeth), and significantly lower maxillary volume (12.88 ±â€Š0.61 cm3 versus 15.24 ±â€Š0.88 cm3, respectively). The severity of maxillary hypoplasia in cleft patients increases with increased dental agenesis. These data indicate that intrinsic factors play a significant role in maxillary growth restriction in cleft patients, independent of the sequelae of surgical intervention.

Precision and reliability of Dolphin 3-dimensional voxel-based superimposition.

INTRODUCTION: Superimposition of 2 cone-beam computed tomography images is possible by using landmarks, surfaces, or density information (voxel-based). Voxel-based superimposition is automated and uses the most image content, providing accurate results. Until recently, this superimposition was extremely laborious, but a user-friendly voxel-based superimposition has recently been introduced. Our aim was to evaluate the precision and reliability of Dolphin 3-dimensional voxel-based superimposition (Dolphin Imaging, Chatsworth, Calif). METHODS: This was a retrospective study using existing scans of 31 surgical orthodontic patients with a mean age of 21 ± 8 years (range, 15-47 years). Each patient had a presurgical and a postsurgical scan taken within 12 months. Surgical patients were used since the reference area for superimposition was not affected by growth or surgical procedures. The volumes were superimposed using voxel-based methods from Dolphin Imaging and a tested method used previously. This method uses 2 open-source programs and takes about 3 hours to complete, whereas the Dolphin method takes under 5 minutes. The postsurgical scan was superimposed on the presurgical scan at the cranial base. Postsurgical registrations for both methods were compared with each other using the absolute closest point color map, with emphasis on 7 regions (nasion, A-point, B-point, bilateral zygomatic arches, and bilateral gonions). RESULTS: Intraclass correlations showed excellent reliability (0.96). The mean differences between the 2 methods were less than 0.21 mm (voxel size, 0.38). The smallst difference was in the left zygomatic area at 0.09 ± 0.07 mm, and the largest was in the right gonial region at 0.21 ± 0.13 mm. CONCLUSIONS: Dolphin 3-dimensional voxel-based superimposition, a fast and user-friendly method, is precise and reliable.

kVp, mA, and voxel size effect on 3D voxel-based superimposition.

OBJECTIVES: To evaluate the effect of changing kVp, mA, and voxel size on the accuracy of voxel-based superimposition on the anterior cranial base. MATERIALS AND METHODS: Cone beam computed tomography (CBCT) scans were taken on a phantom skull using different kVp, mA, and voxel size combinations. CBCT scans were superimposed using commercially available software. Two separate open-source software programs were used to generate a three-dimensional (3D) color map objective assessment of the differences in seven different regions: Nasion, Point A, Zygomatic (right and left), Point B, and Gonial (right and left). Each region had around 200 points that were used to calculate the mean differences between the superimpositions. RESULTS: Intraclass correlation showed excellent reliability (0.95). Lowering the kVp made the biggest difference, showing an average discrepancy of 0.7 ± 0.3 mm, and a high mean of 1.4 ± 0.3 in the Right Gonial region. Lowering the mA showed less of a discrepancy, with an average of 0.373 ± 0.2 mm, and the highest discrepancy, also on the Right Gonial Area, of 0.7 ± 0.1 mm. The voxel size had the least impact on the accuracy of registered volumes, with mean discrepancy values of less than 0.2 mm. CONCLUSIONS: Using different CBCT settings can affect the accuracy of the voxel-based superimposition method. This is particularly the case when using low kVp values, while changes in mA or voxel sizes did not significantly interfere with the superimposition outcome.