John C. Huang

PTH Differentially Regulates Expression of RANKL and OPG

RANKL and OPG gene expressions were measured with and without PTH at different stages of osteoblast development. Mouse stromal cells were cultured in osteoblast differentiating conditions, and RANKL, OPG, COL1, ALP, OC, and PTHRec genes were measured using qRT‐PCR. OPG:RANKL ratios indicate that PTH may induce a possible switch in the regulatory mechanism of osteoclastogenesis where OPG is inhibited early and RANKL is increased at late stages of osteoblast differentiation.

Comparison of airway space with conventional lateral headfilms and 3-dimensional reconstruction from cone-beam computed tomography

INTRODUCTION Changes in the normal pattern of nasal respiration can profoundly affect the development of the craniofacial skeleton in both humans and experimental animals. The orthodontist is often the first clinician to notice that a child is breathing primarily through the mouth, either at the initial examination or later during treatment. The lateral headfilm, part of the patients normal records, might show increased adenoid masses, suggesting that these could be part of the problem. Previous studies have, however, questioned the validity of the information from lateral headfilm. METHODS Our aim was to compare imaging information about nasopharyngeal airway size between a lateral cephalometric headfilm and a 3-dimensional cone-beam computed tomography scan in adolescent subjects. The nasopharyngeal airway area and volume were measured in 35 subjects (8 boys, 27 girls; average age, 14 years). RESULTS Volumetric measurement errors ranged from 0% to 5% compared with known physical airway phantoms used to calibrate. A moderately high (r = 0.75) correlation was found between airway area and volume; the larger the area, the larger the volume. However, there was considerable variability in the airway volumes of patients with relatively similar airways on the lateral headfilms. Nine of the 35 patients had over 25% of the potential nasopharyngeal airway volume occupied by inferior turbinate protuberances, leading to significant airway restriction in some patients. CONCLUSIONS The cone-beam 3-dimensional scan is a simple and effective method to accurately analyze the airway.

Comparison of cone beam computed tomography imaging with physical measures

OBJECTIVES The goal of this study was to determine the accuracy of measuring linear distances between landmarks commonly used in orthodontic analysis on a human skull using two cone beam CT (CBCT) systems. METHODS Measurements of length were taken using volumetric data from two CBCT systems and were compared with physical measures using a calliper applied to one human adult skull. Landmarks were identified with chromium steel balls embedded at 32 cranial and 33 mandibular landmarks and the linear measures were taken with a digital calliper. The skull was then scanned with two different CBCT systems: the NewTom QR DVT 9000 (Aperio Inc, Sarasota, FL) and the Hitachi MercuRay (Hitachi Medico Technology, Tokyo, Japan). CT data including the landmark point data were threshold segmented using CyberMeds CB Works software (CB Works 1.0, CyberMed Inc., Seoul, Korea). The resulting segmentations were exported from CB Works as VRML (WRL) files to Amira software (Amira 3.1, Mercury Computer Systems GmbH, Berlin, Germany). RESULTS The error was small compared with the gold standard of the physical calliper measures for both the NewTom (0.07+/-0.41 mm) and CB MercuRay (0.00+/-0.22 mm) generated data. Absolute error to the gold standard was slightly positive, indicating minor compression relative to the calliper measurement. The error was slightly smaller in the CB MercuRay than in the NewTom, probably related to a broader greyscale range for describing beam attenuation in 12-bit vs 8-bit data. CONCLUSIONS The volumetric data rendered with both CBCT systems provided highly accurate data compared with the gold standard of physical measures directly from the skulls, with less than 1% relative error.

Evaluation of the human airway using cone-beam computerized tomography

OBJECTIVE The goal of this project was to define and measure human airway space with radiographic volumetric 3-dimensional imaging and digital reconstruction of the pharynx using cone-beam computerized tomography. STUDY DESIGN This was a randomized retrospective study. Ten patient scans were selected randomly from a pool of 196 subjects seeking dental treatment at the University of California, San Francisco. Digital Imaging and Communications in Medicine-format volume images were captured using a low-radiation rapid-scanning cone-beam computerized tomography system (Hitachi MercuRay). RESULTS Detailed progressive rostrocaudal cross-sectional area histograms indicated that 8 of the 10 subjects demonstrated a region of maximum constriction near the oropharynx level. The most restricted cross-sectional area varied from 90 mm(2) to 360 mm(2). CONCLUSIONS The maximum constriction of the airway in 10 subjects quietly breathing for 10 seconds indicated variation in the level of the pharynx and the extent of the rostrocaudal zone of restriction.

Cone-beam computed tomography evaluation of mini-implants after placement: Is root proximity a major risk factor for failure?

INTRODUCTION The purposes of this study were to determine factors favoring successful mini-implant placement and to evaluate root proximity as a possible risk factor for failure of osseointegration-based mini-implants during orthodontic treatment. METHODS Three-dimensional cone-beam computed tomography images were used to examine 50 sandblasted, large-grit, and acid-etched surface-treated mini-implants (C-implant, Seoul, Korea) placed in 25 patients. The images were analyzed for 3-dimensional position of the mini-implant (placement angle and depth) and any contact with root surfaces or maxillary sinuses. RESULTS There were no remarkable differences in horizontal placement angles in the axial plane and placement depths of the mini-implants, but the vertical placement angle was significantly higher on the left side (24.5 degrees +/- 11.0 degrees ) compared with the right side (11.8 degrees +/- 11.6 degrees ). The horizontal mini-implant placement angle had a greater inclination tendency toward the maxillary first molar, and 11 mini-implants with root proximity showed mesiobuccal contact with the maxillary first molar root. Only 1 failure in 15 mini-implants with root proximity and 1 failure in 35 without root proximity were observed on the images. CONCLUSIONS Root proximity alone was not considered a major risk factor for osseointegration-based mini-implant failure.

Comparison of Pharyngeal Airway Changes on Plain Radiography and Cone-Beam Computed Tomography After Orthognathic Surgery

PURPOSE The purpose of the present prospective study was to develop a 3-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether changes in the airway before and after orthognathic surgery correlate on 2-dimensional lateral cephalogram and 3-dimensional CBCT images. MATERIALS AND METHODS Patients requiring orthognathic surgery during 2004 to 2005 were recruited for the present study. Lateral cephalograms and CBCT scans were obtained at 3 points: preoperatively, within 1 month postoperatively, and after 6 months postoperatively. The nasopharynx, oropharynx, and hypopharynx were segmented on both the radiograph and the CBCT scan for each patient in a repeatable manner at each point. For the lateral cephalogram, linear measurements in the middle of each of the 3 segments were obtained. For the CBCT, volumetric measurements of each of the 3 segments were obtained. The intrarater variability was assessed, and Pearsons correlation was used to compare the 2 imaging modalities. RESULTS A total of 20 patients scheduled for orthognathic surgery were recruited for the present study. Of the 20 patients, 13 were female and 7 were male. The mean age at surgery was 23.85 years (range 14 to 43). Of the 20 patients, 6 underwent maxillary advancement only, 8 underwent mandibular advancement with or without genioplasty, and 6 underwent 2-jaw surgery or mandibular setback. We examined the entire cohort without separation into procedure or examination point and found a weak, but statistically significant, correlation between the linear and volume measurements in the nasopharyngeal and oropharyngeal regions but not in the hypopharyngeal region (r = 0.43, P < .002; r = 0.49, P < .0002; r = 0.16, P = .26, respectively). The maxillary advancement group (n = 6) demonstrated a correlation between the linear and volume measurements in the nasopharyngeal region (r = 0.53, P = .03). The mandibular advancement with or without genioplasty group (n = 8) showed a correlation in the nasopharyngeal and oropharyngeal regions (r = 0.55, P < .02, and r = 0.46, P = .05, respectively). For the combination/setback procedures (n = 6), a correlation was found in the oropharyngeal region (r = 0.64, P < .01). All other comparisons between the linear and volume measurements did not correlate. Additionally, no correlations were found between the linear and volumetric change in airway size between 6 months postoperatively and preoperatively, except for the oropharyngeal region (r = 0.67, P < .01). CONCLUSION We present a method of measuring the airway that could be used for both 2-dimensional and 3-dimensional images. It includes segmentation of the pharyngeal airway into its nasopharyngeal, oropharyngeal, and hypopharyngeal components. Correlations were found between the linear and volumetric measurements of the segmented airway in patients who had undergone orthognathic surgery; however, the correlations were generally weak.

Anthropometric analysis of the human mandibular cortical bone as assessed by cone-beam computed tomography.

PURPOSE The purpose of this study is to assess cortical thickness, height, and width with cone-beam computed tomography (CBCT), and determine the relationship of these parameters with age. PATIENTS AND METHODS A total of 113 subjects from the University of California at San Francisco Orthodontic Clinic with a CBCT scan were enrolled. Subjects were stratified by age in decades. Thickness of buccal and lingual cortices and mandibular height and width were evaluated in 5 regions (13 sites). A single factorial ANOVA was used to compare the parameters among age groups. P less than or equal to .05 was statistically significant. RESULTS There were 44 (38.9%) males; 69 females. For all groups, the thickest to the least thick cortical plates were: base of the mandible, lower buccal one third, upper lingual one third, upper buccal one third, and lower lingual one third. In all groups, the mandible increased in height as the midline was approached, and the width of the upper third of the mandible decreased from the second molar to the symphysis whereas the reverse occurred in the lower third. Comparison of the age groups showed that subjects 10 to 19 years old had thinner cortical plates than other age groups (P <or= .05) with peak thickness in subjects 40 to 49 years old. The subjects 10 to 19 years old also had lower posterior mandibular height (P <or= .05). There was no statistical difference in width among the groups. CONCLUSIONS The mandibular cortical bone is thickest at the base, on the buccal side. Subjects who are 10 to 19 years old have thinner cortical bone and decreased mandibular height compared with all other age groups. The mandible continues to mature through 40 to 49 years of age and then decreases in thickness after this period.

Consistency and precision of landmark identification in three-dimensional cone beam computed tomography scans

The purpose of this study was to quantify the consistency and precision of locating three-dimensional (3D) anatomic landmarks. The hypotheses tested are that these landmarks have characteristic and variable error patterns associated with their type and location. The consistency and precision of nine orthodontists identifying 32 landmarks of 19 patients were quantified. The cone beam computed tomography (CBCT) data were acquired using a Hitachi CB MercuRay system. Prior to the study, all examiners were calibrated with respect to the definitions of the landmarks and on the use of the software program (Dolphin) for identifying the landmarks. In addition, a reference guide was provided that had the definitions and sample images of the landmarks. Data were collected in spreadsheets as x, y, and z co-ordinates and statistically analysed to determine the mean and standard deviation (SD). The mean location for a given landmark on a given patient served as the reference point. The mean of the distances from the reference point was used as the consistency, while the SD of this mean was used as a measure of precision. The error in the x, y, and z planes was calculated in order to determine the specific characteristics of each landmark. The consistency in landmark location and precision did not differ significantly among the nine examiners. Sella turcica was the most consistently (0.50 mm) and most precisely (0.23 mm) identified anatomic landmark. The most inconsistent landmark was porion-right (2.72 mm) and the most imprecise landmark was orbitale-right (1.81 mm). Due to the lack of even distribution of the errors, careful use of these landmarks for analysis purposes is needed.

Evaluating the mandible with cone-beam computed tomography.

INTRODUCTION The purpose of this research was to examine methods for assessing the shape and growth of the mandible 3 dimensionally. Furthermore, 1 method was defined and applied. METHODS Thirty mandibles were assessed. An average or mean shape was determined, and the mandibles were ranked quantitatively, by using the root mean square (RMS), according to their variation from the mean. The rankings ranged from mandibles that were small, short, and narrow at the minus-RMS end, to large, tall, and broad at the plus-RMS end. A second analysis provided a method to superimpose a mandible over the average mandible and determine the differences from the average-derived mandible by using a spectrum of colors to indicate changes in a region. RESULTS Variations in the mandible were greatest in the condylar heads, coronoid tips, canine-incisor dentoalveolar segment, and chin point. CONCLUSIONS The visual images of the 30 segmented mandibles suggest that a new method of classification needs to be developed that extends the original 2-dimensional lateral evaluation to a total 3-dimensional view that provides new relationships, such as the direction of the condylar heads to the ramus and the ratio of the intergonial angle length to the intercondylar head length to define the narrowness of a mandible.

Three-dimensional analysis of the airway with cone-beam computed tomography.

INTRODUCTION In this study, using a cone-beam computed tomography system, we evaluated the airways of 30 adults. METHODS The shapes of the 3-dimensional volume of the airway were analyzed and compared among the subjects by using surface superimposition software techniques. RESULTS The airway had the greatest variability in the hypopharynx, in the region below the epiglottis, and above the vocal folds. Moderate variation was apparent at the nares, behind the soft palate, and at the base of the tongue. Conservation of form was seen at the central portion of the nasal airway surrounding the inferior turbinate. CONCLUSIONS The potential for comparing the shape of the airway among subjects is possible.