Search

Introduction Airway size increases are associated with maxillomandibular advancement (MMA) surgery and improvement or elimination of obstructive sleep apnea (OSA). The 3-dimensional morphologic, volumetric, height, cross-sectional surface area, and diameter changes of the upper airway in patients with OSA after MMA, however, are not well understood. Methods Patients with moderate or severe OSA who underwent MMA surgery were evaluated by preoperative and postoperative cone-beam computed tomography scans and polysomnograms. The upper airway space was also divided into retropalatal and retroglossal spaces and was analyzed for volumetric, height, cross-sectional surface area, transverse, and anteroposterior diameter changes. Results Ten consecutive OSA patients with an average preoperative apnea/hypopnea index of 46 and treated with MMA surgery were included in this study. There were 8 men and 2 women, with an average age of 46 years and an average body mass index of 28. There was an average of a 2.5-fold increase in the total volume of the upper airway space. The retropalatal space increased by 3.5-fold. The retroglossal space increased by 1.5-fold. The greatest change in a cross-sectional area occurred in the transverse axis in both the retroglossal and retropalatal spaces. The average apnea/hypopnea index was 4 postoperatively. Conclusion MMA surgery results in a significant increase in the volume and a morphologic airway change from a round to an elliptical f shape in the upper airway space in patients with OSA. The combination of these actions reduces the collapsibility of the upper airway space, hence improving or resolving the OSA.

One of the important aspects of diagnosis in the mixed dentition is the determination of the tooth size-arch length relationship. Such a determination is often made before eruption of the permanent canines and first and second premolars. The most commonly used prediction method of Tanaka and Johnston is based on data from a sample of children of Northern European descent. The accuracy of this method when applied to a different ethnic population is questionable. In this study, 201 dental plaster casts of Asia-Pacific-American subjects, all of whom were under the age of 21 years, were used. The actual measurements were compared with the predicted values derived from the Tanaka and Johnston equations and significant differences were found. The data illustrate the limitations of the Tanaka and Johnston method when applied to a sample population of other than European descent. From this data, two linear regression equations were developed for tooth size prediction in Asian-American children. (Am J Orthod Dentofacial Orthop 1998;113:293-9.)

The objectives of this study were to evaluate and compare the shear bond strengths and bond failure locations of 2 currently available orthodontic ceramic brackets. Forty polycrystalline ceramic brackets (Clarity, 3M Unitek, Monrovia, Calif) and 40 monocrystalline ceramic brackets (Inspire, Ormco, Orange, Calif) were bonded to 80 extracted premolars with the same bonding system. All bonded specimens were placed in distilled water for 42 hours at 37 degrees C followed by thermal cycling for 700 complete cycles. Forty ceramic brackets, 20 of each type, were tested on a universal testing machine to determine the shear force levels required to debond them. Forty ceramic brackets were removed with the debonding pliers recommended by the manufacturers. All teeth were examined under an optical microscope, and the adhesive remnant index was used to assess the bond failure locations. The mean shear bond strength of the Clarity brackets was 21.67 +/- 5.19 MPa, and the mean shear bond strength of the Inspire brackets was 20.32 +/- 8 MPa. The mean shear bond strengths of both brackets were higher than those considered clinically optimal. Most of the brackets (85% of Clarity and 75% of Inspire) tested on the machine failed at the bracket-adhesive interface. One premolar bonded with an Inspire bracket had enamel fracture upon debonding. Most of the brackets (90% of Clarity and 95% of Inspire) debonded with pliers failed at the bracket-adhesive interface. No enamel damage was evident in any specimen when the brackets were removed with the appropriate pliers. The results indicate that the safest way to remove ceramic brackets with respect to reducing the chance of enamel damage is to use the debonding technique specifically designed for each.

This study was designed to assess the perceived optimal profiles of African Americans versus white Americans. A survey was conducted using profile silhouettes of 30 African American and 30 white patients, ranging in age from 7 to 17 years. Twenty white orthodontists, 18 African American orthodontists, 20 white laypersons, and 20 African American laypersons evaluated the profiles. The preference of each rater for each of the 60 profiles was scored on an attached visual analog scale. Eighteen cephalometric variables were measured for each profile, and statistical analyses were performed on the profiles that had a mean rating of 60 or greater from an analog scale of 0 to 100. The results show the following 6 cephalometric variables were significant: Z-angle, skeletal convexity at A-point, upper lip prominence, lower lip prominence, nasomental angle, and mentolabial sulcus. All raters preferred the African American sample to have a greater profile convexity than they preferred for the white sample. The raters preferred the African American sample with upper and lower lips that were more prominent compared with the white sample. However, only the choice of the African American orthodontists for the African American sample was significantly different for this parameter. The white orthodontists gave the highest mean scores for the profile chosen, whereas the African American laypersons gave the lowest scores.

Direct bonding of brackets has become a routine procedure in clinical orthodontics. Many techniques and materials are currently advocated and used, the most recent being light-cured composites. Advantages of the light-cured systems are their relative ease of use, improved bracket placement, and more rapid set of the composite. For a new system to be clinically viable, it must possess properties that are at least as reliable as existing systems. The purpose of this longitudinal clinical study was to evaluate and compare the rate of success and/or failure between a visible light-cured bonding material (Sequence) and a chemically cured bonding material (System 1+), using both systems in every patient. Contralateral quadrants were bonded with each system respectively. A total of 32 patients were followed for a mean period of 11 months (range of 3 to 21 months), with a total of 531 brackets bonded, 265 with visible light-cured and 266 with chemically cured resins. Failures for each system were recorded and failure rates calculated. The failure rate of the visible light-cured composite was 11.3% and that of the chemically cured composite was 12%. A Chi-squared (chi2) test did not reveal any statistically significant differences between the failure rates of the two systems, (chi2 = 0.014, df-1, P > 0.9).

The book honors and is dedicated to Thomas M. Graber. current editor of our own AMERICAN JOURNAL OF ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS. It is edited by his son, Lee W. Graber. celebrating 40 years of his father's service to the profession as a clinician, teacher, and researcher. The first chapter was written by Robert E. Moyers who in his inimitable, logical style describes his perception of what is meant by "'good orthodontics." Thereafter, the book is divided into three sections in which essays by the various authors are listed under the following headings: (1) Current Science Related to Treatment. (2) Treatment and Technique Principles, and (3) Practice Management Concerns in Orthodontics. In the first section, the essayists endeavor to answer the many questions that are so frequently posed. In a philosophic debate, Donald Enlow underscores the futility of trying to predict structural and functional changes during growt h because of the paucity Of our understanding of biologic principles. Nakamura and Koski describe what happens to the condylar perichondrium when transplanted into a nonfunctional environment. The enigma of the precise nature and mechanisms that cause pain in hyperactive jaw muscles, and their relationships to temporomandibular joint pain are explained by Lars Christensen. Is the temporomandibular joint a load-bearing joint? William Hylander's reviews of the recent advances in the understanding of the forces acting through the temporomandibular joint are thought provoking. Can we stimulate condylar growth in human patients using functional appliances? Petrovic and Stutzmann attempt to throw new light on the quintessential problem of dentofacial orthopedics. In a separate chapter, Jim McNamara likewise discusses the possibility of stimulating the mandible to grow in human patients. Lysle Johnston, in a series of collaborative experiments with his students, explores the behavior of the condyle in animals under conditions such as condylectomy, loading, and unloading in an effort to establish the true role of the condylar cartilage, hopefully putting to rest many earlier anecdotal reports. Per Rygh provides a fresh insight into the response of the periodontium during tooth movement, and the unwanted side effects such as root resorption and loss of periodontal support--all clinically oriented considerations. Nasorespiratory problems in orthodontics are briefly reviewed by Linder-Aronson. whereas Thomas Rakosi identifies different types of Class II malocclusions and emphasizes the need to recognize the various types in treatment, particularly in the mixed dentition. In the second section of the book under the heading, "Treatment Techniques and Princip!es," finite-element modeling of craniofacial growth and development is eruditely discussed in a section by Moss, Salentijn, and Skalak. Schmuth o f West Germany advocates taking advantage of removable type appliance therapy 'during the early phases of treatment and is in favor of two or even three phases of orthodontic treatment for specific orthodontic problems. The treatment of skeletal open bitesby means of molar extraction, according to Frfinkel and Frfinkel. is not a panacea unless functional factors that include the postural performance of those muscles associated with the creation o f a competent oral seal are taken into consideration. The management of similar cases by means of spring-loaded occlusal bite blocks is the treatment of choice for Woodside and Linder-Aronson. In the nextthree chapters, three superb clinicians namely, "Wick" Alexander, Terrell Root, and Brainerd Swain--each separately discuss at length multiband treatment techniques invaluable material for those clinicians Wishing to improve their treatment skills. Bonding techniques are described by Miura; retention in the adult dentition is covered by Bj0rn Zachrisson. The challenge of the bilateral cleft palate, temporomandibular dysfunction in children, and surgical intrusion of the maxilla for the correction of open bite malocclusions are described by Rosenstein, Thflander, and Thomas and Proffit, respectively. In the final chapter of this section, Vanarsdall highlights the need for

Surgical mandibular advancement results in many soft tissue changes. The purpose of this study was to quantify the changes seen in the cervicomental angle and the lip-chin-throat angles in response to mandibular advancement, as well as hyoid bone positional changes. As a result of statistical analysis of hyoid bone and soft tissue linear and angular changes, prediction models are presented as to the soft tissue response to mandibular advancement in the cervicomental region.

This investigation sought to evaluate the effects of air-rotor stripping on the susceptibility of human enamel to demineralization using an in vitro caries model. Crowns of extracted premolar teeth were abraded (0.5 mm) on one proximal surface by air-rotor stripping. The teeth were placed in a demineralizing gel and removed at various intervals up to 336 hours. Lesion depth and mineral content on the abraded and intact surfaces was measured with contact microradiography and computerized image analysis (double window technique). For each time interval measured, lesion depth was greater (p0.05) on the abraded surfaces and mineral density was significantly less (p0.05). In a second experiment, the effect of fluoride supplements (dentifrice or topical gel) were examined on abraded and intact enamel surfaces that were exposed to the acid gel for 192 hours. The data showed that fluoride treatments significantly reduced lesion penetration on intact and abraded surfaces compared with a no fluoride group. Lesion depth on the abraded, fluoride treated surfaces was significantly greater (p0.05) than on the intact untreated surfaces. No significant differences (p0.05) were apparent between the fluoride treatment groups with respect to lesion depth and mineral density within the lesion. These results suggest that air-rotor stripping significantly increases the susceptibility of proximal enamel surfaces to demineralization. As a result, the clinician should use caution in the application of this technique until the long-term effects on caries susceptibility have been determined.

This study examined systematic and random errors associated with repeated-measure, multiple-cycle unilateral mastication in children during single recording sessions with the Replicator system. Twenty-six recording sessions with 17 children (10 boys, 7 girls) were examined. Nine of these children had a functional-shift unilateral crossbite malocclusion and were recorded before and after crossbite correction. Repeated recordings (trials) of mandibular movement during each session were made of right-side chewing of similar-sized pieces of cheese. The following variables were computed for each chewing cycle (stroke): time closed, maximum closure velocity, maximum opening velocity, chewing rate, vertical opening, and lateral deviation. From the multiple cycles of each trial, two pattern descriptors--the average and standard deviation--were determined for each variable. In addition, the mean and variance of these pattern descriptors were determined from the multiple trials of each recording session and were the dependent variables in a stepwise multiple regression analysis, with treatment status, sex, age, dentition stage, crossbite presence, and right side status the independent variables. The results disclosed bias in repeated measures of human chewing in response to adaptation to the recording session; this was evident in the average response but not in the variability of the measures. Sex and functional status of the subjects were associated with the mean and variance of measures describing the chewing pattern.