G. Fräns Currier

The effect of a modified functional appliance on obstructive sleep apnea

This study combined the use of cephalometrics and overnight polysomnographic monitoring to analyze the effects of a modified functional appliance on airway, sleep, and respiratory variables in patients with obstructive sleep apnea (OSA). Twelve patients without overt anatomic or pathologic evidence of obstruction were selected on the basis of an initial single night of polysomnographic monitoring, which confirmed the diagnosis of obstructive sleep apnea syndrome. The patients subsequently were fitted with a modified functional appliance designed to securely hold the mandible in an anterior-inferior position. A subsequent overnight polysomnographic study was obtained with each patient wearing the appliance. Lateral cephalometric radiographs with and without the appliance in place were also obtained. The mean vertical and horizontal changes in mandibular position while wearing the appliance were 8.49 mm and 2.28 mm, respectively. The findings indicate that 10 of the 12 patients had decreases in the rate of complete airway obstructions from a mean of 28.86 to 18.69 events per hour, and in the total apnea index from a mean of 53.81 to 35.99 events per hour. A reduction in the rate of obstructive events is attributed to the effect of the appliance on the oropharyngeal structures. Six cephalometric measurements are presented to provide a means of assessing effects of the appliance on the oropharynx and associated structures. The modified functional appliance is a conservative, successful treatment alternative that could benefit patients with obstructive sleep apnea syndrome.

A 3-year evaluation of skeletal stability of mandibular advancement with rigid fixation

The postsurgical changes associated with mandibular advancements using the sagittal ramus osteotomy and rigid fixation were evaluated. This retrospective study was based on examination of lateral cephalometric radiographs of 19 individuals (16 females and 3 males) with a mean age of 26.6 years. These radiographs were evaluated presurgically, immediately postsurgery, and 3 years postsurgically (2 years, 9 months to 4 years, 5 months). The mean amount of sagittal surgical advancement was 6.7 +/- 2.3 mm, and the mean amount of postsurgical relapse was 1.3 +/- 2.0 mm, representing a 14% relapse of the original surgical advancement. However, individual variation in the amount and direction of movement of the mandible was found during the follow-up period. Postsurgical relapse was found to be related to the amount of surgical advancement. Linear-regression analysis between these two variables resulted in an R2 value of 0.448. Fourteen of the subjects relapsed in the posterior direction, with 2 relapsing more than 50% of the surgical advancement. Five of the subjects moved further anteriorly, with 1 advancing as much as 50% more than the original advancement. The findings of this study suggest that mandibular advancement with the sagittal ramus osteotomy and rigid fixation does not provide consistently stable postsurgical results. However, when compared with previously reported relapse studies using nonrigid fixation techniques, rigid fixation yielded superior results.

Stability of transverse expansion in the mandibular arch

This was a retrospective, longitudinal cephalometric and cast study of 29 white patients at pretreatment, posttreatment, and an average of 6 years 3 months postretention. The goal was to assess changes with treatment and retention with the expanding mandibular lingual arch appliance in conjunction with fixed edgewise treatment. Seven mandibular cast measurements were assessed, including arch crowding, arch perimeter, arch length, and arch width at the permanent canines, first premolars, second premolars, and first molars. Cephalometric radiographs were digitized, and 16 cephalometric measurements were made. Repeated-measures analysis of variance and 2-sample t tests were used to determine statistically significant changes. It was found that the expanding lingual arch used for less than 6 months with the mandibular fixed edgewise appliance caused an increase in both the transverse and sagittal dimensions of the mandibular dental arch. Transverse expansion was more stable in the posterior region of the mandibular dental arch than in the anterior region. Mandibular intercanine width increase could be maintained only by fixed retention. Although the maxillary and mandibular incisors were advanced and proclined, lip protrusion did not occur.

The skeletal stability of Le Fort I downfracture osteotomies with rigid fixation

Twenty subjects receiving Le Fort I downfracture osteotomies stabilized with rigid fixation were studied for relapse. The analysis was based on longitudinal cephalometric radiographs taken within 2 weeks presurgically, 1 week postsurgically, and after a minimum period of 6 months postsurgically. Vertical and sagittal changes in the maxilla were evaluated in reference to the Frankfort horizontal plane. It was found that the mean postsurgical relapse was minimal and not significant. It was smaller than that reported for patients who had received stabilization of the maxilla with intraosseous and maxillomandibular wiring. It was concluded that the rigid fixation technique is dependable and yields stable postsurgical results in the maxilla.

Evaluation of 3 retention protocols using the American Board of Orthodontics cast and radiograph evaluation

INTRODUCTIONnThe purpose of this study was to quantify tooth movement among different retention protocols after the orthodontic appliances were removed.nnnMETHODSnA total of 90 patients were evaluated using the American Board of Orthodontics discrepancy index and the cast and radiograph evaluation at debond and the 1-year recall. These patients were equally divided into 3 retention protocols: upper Hawley/lower Hawley, upper Hawley/lower bonded, and upper Essix/lower bonded. The patients were then equally grouped by extraction or nonextraction treatment and case complexity. Paired t tests were used to compare the paired sample means. Analysis of variance tests were used to compare the means for more than 2 groups. A 2-sided 0.05 alpha level was used to define statistical significance.nnnRESULTSnThe upper Hawley/lower bonded showed the greatest amount of settling, and the upper Essix/lower bonded had the least settling, but these differences were statistically insignificant. The differences between the extraction and nonextraction treatments were not significant. The group with low discrepancy index scores showed significantly more settling than did the group with high discrepancy index scores.nnnCONCLUSIONSnThe cast and radiograph evaluation variables that improved overall were marginal ridges, overjet, occlusal contacts, interproximal contacts, root angulation, and total cast and radiograph score. The cast and radiograph evaluation variables that worsened were alignment/rotation, buccolingual inclination, and occlusal relationship. Extraction or nonextraction treatment led to no real difference in settling. The discrepancy index, or initial case complexity, was the greatest factor in determining the improvement of occlusion or settling during the retention phase.

Postsurgical volumetric airway changes in 2-jaw orthognathic surgery patients

INTRODUCTIONnFindings from early cephalometric studies on airway changes after 2-jaw orthognathic surgery have been challenged because the previous anteroposterior interpretation of airway changes can now be evaluated in 3 dimensions. The aims of this study were to use cone-beam computed tomography to quantify the nasopharynx, oropharynx, and total airway volume changes associated with skeletal movements of the maxilla and mandible in a sample of patients undergoing 2-jaw orthognathic surgery for correction of skeletal malocclusion.nnnMETHODSnSkeletal movements and airway volumes of 71 postpubertal patients (31 male, 40 female; mean age, 18.8 years) were measured. They were divided into 2 groups based on ANB angle, overjet, and occlusion (Class II: ANB, >2°; overjet, >1 mm; total, 35 subjects; and Class III: ANB, <1°; overjet, <1 mm; total, 36 subjects). Presurgical and postsurgical measurements were collected for horizontal, vertical, and transverse movements of the maxilla and the mandible, along with changes in the nasopharynx, oropharynx, and total airways. Associations between the directional movements of skeletal structures and the regional changes in airway volume were quantified. Changes in the most constricted area were also noted.nnnRESULTSnHorizontal movements of D-point were significantly associated with increases in both total airway (403.6 ± 138.6 mm(3); P <0.01) and oropharynx (383.9 ± 127.9 mm(3); P <0.01) volumes. Vertical movements of the posterior nasal spine were significantly associated with decreases in total airway volume (-459.2 ± 219.9 mm(3); P = 0.04) and oropharynx volume (-639.7 ± 195.3 mm(3); P <0.01), increases in nasopharynx (187.2 ± 47.1 mm(3); P <0.01) volume, and decreases in the most constricted area (-10.63 ± 3.69 mm(2); P <0.01). In the Class III patients only, the vertical movement of D-point was significantly associated with decreases in both total airway (-724.0 ± 284.4 mm(3); P = 0.02) and oropharynx (-648.2 ± 270.4 mm(3); P = 0.02) volumes. A similar negative association was observed for the most constricted area for the vertical movement of D-point (-15.45 ± 4.91 mm(2); P <0.01).nnnCONCLUSIONSnOptimal control of airway volume is through management of the mandible in the horizontal direction and the vertical movement of the posterior maxilla for all patients. The surgeon and the orthodontist should optimally plan these movements to control gains or losses in airway volume as a result of orthognathic surgery.

Digital tooth-based superimposition method for assessment of alveolar bone levels on cone-beam computed tomography images

INTRODUCTIONnCone-beam computed tomography images have been previously used for evaluation of alveolar bone levels around teeth before, during, and after orthodontic treatment. Protocols described in the literature have been vague, have used unstable landmarks, or have required several software programs, file conversions, or hand tracings, among other factors that could compromise the precision of the measurements. The purposes of this article are to describe a totally digital tooth-based superimposition method for the quantitative assessment of alveolar bone levels and to evaluate its reliability.nnnMETHODSnUltra cone-beam computed tomography images (0.1-mm reconstruction) from 10 subjects were obtained from the data pool of the University of Oklahoma; 80 premolars were measured twice by the same examiner and a third time by a second examiner to determine alveolar bone heights and thicknesses before and more than 6 months after orthodontic treatment using OsiriX (version 3.5.1; Pixeo, Geneva, Switzerland). Intraexaminer and interexaminer reliabilities were evaluated, and Dahlbergs formula was used to calculate the error of the measurements.nnnRESULTSnCross-sectional and longitudinal evaluations of alveolar bone levels were possible using a digital tooth-based superimposition method. The mean differences for buccal alveolar crest heights and thicknesses were below 0.10 mm for the same examiner and below 0.17 mm for all examiners. The ranges of errors for any measurement were between 0.02 and 0.23 mm for intraexaminer errors, and between 0.06 and 0.29 mm for interexaminer errors.nnnCONCLUSIONSnThis protocol can be used for cross-sectional or longitudinal assessment of alveolar bone levels with low interexaminer and intraexaminer errors, and it eliminates the use of less reliable or less stable landmarks and the need for multiple software programs and image printouts. Standardization of the methods for bone assessment in orthodontics is necessary; this method could be the answer to this need.

Flexural properties of rectangular nickel-titanium orthodontic wires when used as ribbon archwires.

OBJECTIVE:nTo compare the flexural properties of rectangular nickel-titanium (Ni-Ti) orthodontic wires in occlusoapical and faciolingual orientations using a standardized test method.nnnMATERIALS AND METHODS:nTwenty-two rectangular Ni-Ti wire groups were tested in occlusoapical (ribbon) orientation: eight conventional Ni-Ti products, five superelastic Ni-Ti products, and nine thermal Ni-Ti products (n = 10 per group). Six products of thermal Ni-Ti wire were tested in faciolingual (edgewise) orientation. A three-point bending test was performed to measure deactivation force at 3.0-, 2.0-, 1.0-, and 0.5-mm deflections of each rectangular wire at 37.0 ± 0.5°C. Analysis of variance and post hoc Student-Newman-Keuls tests were used to compare the mean values of the different groups (α = .05).nnnRESULTS:nThe ranges of deactivation forces varied greatly with different kinds, sizes, products, and deflections of Ni-Ti wires. One product of conventional and superelastic Ni-Ti wires had steeper force-deflection curves. Four products had similarly shaped flat force-deflection curves, whereas the sixth product had a moderately steep force-deflection curve. Thermal Ni-Ti wires had smaller deactivation forces ranging from 0.773 N (78.8 g) to 2.475 N (252.4 g) between deflections of 1.0 and 0.5 mm, whereas wider ranges of force from 3.371 N (343.7 g) to 9.343 N (952.7 g) were predominantly found among conventional Ni-Ti wires between deflections of 3.0 and 2.0 mm.nnnCONCLUSIONS:nClinicians should critically select archwires for use in the occlusoapical orientation not only based on Ni-Ti wire type, size (0.022 × 0.016-in or 0.025 × 0.017-in), and product but also with deactivation deflections from 0.5 and 1.0 mm to obtain light forces in the occlusoapical orientation.