Apparatus criticus: methods used to evaluate growth modification in Class II malocclusion.
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Humans↗
Biomedical subjects
J F Tulloch
Publications and source records attributed to J F Tulloch.
Surgical versus orthodontic correction of skeletal Class II malocclusion in adolescents: effects and indications.
To clarify the effects of orthodontic versus surgical treatment and to distinguish more clearly those Class II patients who can be treated successfully with orthodontics alone, we compared three groups of adolescents: forty patients treated successfully with orthognathic surgery, 40 patients treated successfully with orthodontics alone, and 21 patients whose orthodontic treatment was judged to be unsuccessful. Successful surgical treatment was accomplished largely by bringing the mandible forward, but this involved vertically repositioning the maxilla, alone or in combination with advancing the mandible, in 40% of the patients. Successful orthodontic treatment resulted from a combination of retraction of the maxillary incisors and protraction of the mandibular incisors; most of the successfully treated group also had significant vertical growth, and 40% had greater than 2 mm anteroposterior growth. The unsuccessfully treated orthodontic patients initially had greater overjet, more severe mandibular deficiency, and greater anterior facial height than those treated successfully; they also had less retraction of the maxillary incisors and less growth during treatment. In Class II adolescents beyond the growth spurt, surgery is likely to be needed for successful correction of the malocclusion if the overjet is greater than 10 mm, especially if the distance from pogonion to nasion perpendicular is 18 mm or more, mandibular body length is less than 70 mm, or facial height is greater than 125 mm.
Adolescent↗
Update on technology assessment in dentistry.
This review focuses on evaluations of particular clinical problems or technologies in dentistry that have used the recently developed technology assessment techniques of decision analysis, meta-analysis, and cost-effectiveness analysis. It also discusses general methodologic and implementation issues in the assessment of health-care technologies.
Cost-Benefit Analysis↗
Technology assessment in the Normative Aging Study.
This review of publications based on data from the Veterans Affairs Normative Aging Study identified four articles that were considered assessments of health care technologies. Three evaluated methods for research on body composition, the fourth studied ventricular size in patient with presenile dementia. Several additional articles are discussed that provided data on baseline values or risk factors for disease that might be useful in generating hypotheses to be tested in later assessments of technologies.
Aging↗
Technology assessment in the Veterans Administration Dental Longitudinal Study.
Of the 52 studies emanating from the Veterans Affairs Dental Longitudinal Study, 6 were identified as technology assessments. Three of these studies evaluated dental radiographs used for the diagnosis of oral lesions. Two studies compared alternative technologies for the replacement of missing teeth, and one reported the effects of NSAIDs on alveolar bone loss. Four additional articles are discussed that provide data that will be useful in future assessments of dental technologies.
Aged↗
Methods used to evaluate growth modification in Class II malocclusion.
The methods used to study growth modification in orthodontic patients can have considerable impact on the conclusions that may be drawn. Because of the large "between-patient" variation and small mean changes usually observed, apparent differences in response may sometimes be more attributable to study design than to treatment effectiveness. A systematic review of four major orthodontic journals (1980 to 1987) identified 50 studies reporting treatment of young patients with Class II malocclusion. Variables defined to classify the studies included appliance systems, patient selection, comparison groups, research design, data collection, analysis, and reporting. The appliance systems most frequently investigated were the function regulator and the activator, used with and without headgear. Only 11 (22%) studies were prospective, and random assignment to alternative treatments was never used in this sample. Comparison groups used in 76% of the studies were untreated Class II patients (n = 18) and/or patients with alternate appliance systems (n = 17). In only 24% of the reports were groups tested for pretreatment equivalence. Few studies reported fully how patients had been selected, how decisions had been made to discontinue or change treatment, or whether patients had been lost to study. While most studies reported "p values," in only four were alpha levels adjusted for the number of tests (type I error), and no study included a post beta estimate (type II error). Age, sex, maturation, and duration of treatment were usually reported but seldom adjusted for in the analyses. Given the multiple indices of treatment effect, the generally small sample sizes, weak research designs, and incomplete reporting of important data, we cannot yet conclude whether orthodontic treatment influences the growth of Class II patients.
Data Collection↗
Evaluation of the costs and relative effectiveness of alternative strategies for the removal of mandibular third molars.
Decision analysis is used to compare the cost and disability of alternative treatment strategies for asymptomatic mandibular third molars. The analysis shows that extracting only those third molars that remain impacted and become pathologically involved is always associated with less expected cost and disability than prophylactic removal of asymptomatic wisdom teeth.
Adolescent↗
Split-mouth and cross-over designs in dental research.
The presence of paired or multiple organs (arches, quadrants, teeth) and the chronic nature of many dental diseases suggest the use of split-mouth (trials in which each subject receives greater than or equal to 2 treatments, each to a separate section of the mouth) and cross-over research designs (trials in which each subject receives greater than or equal to 2 treatments in sequence). While these designs offer potential savings in resources, their usefulness can be negated if several strict scientific and statistical assumptions are not met. The primary prerequisites for the use of split-mouth and cross-over designs are that: (1) the disease to be investigated is relatively stable and uniformly distributed; (2) the effects of the treatments to be evaluated are short-lived or reversible for cross-over studies, or are localized for split-mouth designs. Other important factors that influence the appropriate use of these designs include: the method of treatment sequencing and assignment, and the cross-over rules used; blinding of patient assignment, patients and observers; assessment of order effects including period, carry-over or spill-over effects; the choice of statistical analysis, the sample size utilized, and the special importance of patients lost to study or of faulty data points. The objective of this study was to review 3 journals for studies using split-mouth or cross-over designs to determine how the assumptions underlying these research designs are considered and applied in dental research. The majority of studies used adequate methods for treatment allocation and sequencing; however, many studies failed to take advantage of the research designs in the statistical analysis of data. In addition, very few studies considered the possibility of order effects or reduced bias through blinding procedures.
Clinical Trials as Topic↗
A review of clinical research in orthodontics.
The orthodontic journals should provide valid and reliable information that helps clinicians make appropriate decisions about patient care. The nature of the published literature has not been categorized. The American Journal of Orthodontics and Dentofacial Orthopedics (formerly the American Journal of Orthodontics) was reviewed for the years 1976, 1981, and 1986, to determine the frequency of clinical articles, the topics reported, the study designs used to obtain information, the senior author affiliation, and the major funding sources. This review demonstrates that more than half the articles in this Journal report data on patients, with the majority focusing on the evaluation or description of therapeutic interventions. Academic institutions contribute the majority of the clinical research, although only a few student theses are published. The major support for this work continues to be from departmental resources with little external funding. Despite the introduction of powerful research designs such as randomized clinical trials, these methods have not been widely adopted for orthodontic clinical research. The case report (study containing fewer than 10 patients with no control nor comparison group) continues to be the most frequently published format. Clinicians should become aware of the inherent weakness in the research designs generally used and recognize the limited information that can be obtained from such methods. Support for this research needs to be greatly expanded if the more powerful type of study required to provide valid and reliable clinical information is to be continued.
Epidemiologic Methods↗
Methodological considerations in the analysis of cost effectiveness in dentistry.
Cost-effectiveness analysis is a technique applied with increasing frequency to help make rational decisions in health care resource allocation. This article reviews the ten general principles of cost-effectiveness analysis outlined by the Office of Technology Assessment of the US Congress and describes a model for such analyses used widely in medicine, but only recently applied in dentistry. The imperative for the formulation of the best current information on both the effectiveness of dental practices and their costs is made more urgent because of the now universally recognized belief that resources available to meet the demands for health care are limited. Today's environment requires critical allocation decisions within categorical health problems, across diseases, or relative to other health problems. If important health benefits or cost savings are to be realized, then these analytic approaches must become widely understood, accepted, and appropriately applied by key decision makers in the dental health sector.
Cost-Benefit Analysis↗
Complications of orthognathic surgery: a comparison between wire fixation and rigid internal fixation.
This retrospective review compares the results of using rigid internal fixation (RIF) and wire fixation for orthognathic surgery patients. The records of two groups of demographically similar patients who underwent comparable surgery, performed by the same four attending surgeons at the same institutions during the same time period (1983 to 1986), were evaluated for complications and unanticipated treatment results. The most striking finding of this study is the general similarity between the two groups. However, differences in frequency of excessive weight loss and persistent restriction of mandibular opening suggest a benefit from early mobility of the mandible that comes with RIF. Because there was no concomitant increase in complications or unexpected results of treatment, the introduction of RIF for orthognathic surgery may offer patients some potential advantages.
Humans↗
Selecting the optimal threshold for the radiographic diagnosis of interproximal caries.
The declining prevalence of dental caries and changes in understanding about the progressive nature of this disease have led to recommendations that new diagnostic criteria be adopted. Selecting the optimum diagnostic threshold requires consideration of the probability of disease, distribution of true and false diagnoses at different test thresholds, and estimates of the consequences of treatment based on these diagnoses. Data from the Veterans Administration Dental Longitudinal Study were used to determine the distribution of true and false diagnoses at progressively more stringent diagnostic thresholds. Estimates of the consequences of treatment provided on the basis of true and false diagnoses were obtained from a randomly selected group of clinicians. The data were combined in a decision analysis to determine the "expected value" of operative treatment at each threshold under varying assumptions about the prevalence of disease, rate of disease progression, and value of treatment. No single diagnostic threshold consistently maximized the benefits of treatment. While patients with a high caries prevalence who experience infrequent recalls would benefit from a diagnostic threshold that includes early lesions, patients with a low caries prevalence who follow good recall schedules should benefit from a more conservative diagnostic threshold.
Dental Caries↗
The application of decision analysis to evaluate the need for extraction of asymptomatic third molars.
A theoretical model using a decision tree is used to compare three alternative strategies: extract all third molars prior to complete root formation; extract only those third molars that become impacted; and extract only those impacted third molars that develop some associated pathology. The model used to determine the expected value of these alternative strategies depends on the probability of eruption, the type of impaction, and likelihood of developing preoperative pathology. The decision tree can be used to identify a preferred strategy either for an individual patient or for a policy recommendation under a variety of clinical conditions.
Decision Making↗
Decision analysis in the evaluation of clinical strategies for the management of mandibular third molars.
Quantitative methods of technology assessment that consider the magnitude of the technology's effect and also incorporate the elements of uncertainty, risk, and preference are needed. This study uses the methods of decision analysis to evaluate a common dental problem: whether or not to extract asymptomatic mandibular third molars. Three alternative strategies are considered. The expected disability of an extraction, measured as equivalent "days of standard discomfort" (DSD), is used as the outcome measure of interest. The analysis suggests that under a wide range of assumptions about the likelihood of different impaction types, chance of pathology, probability of extraction complications, and disability associated with each complication, the strategy of extracting only pathologically involved impacted mandibular third molars is generally the risk-minimizing option. The sensitivity analysis identifies the severity of the outcome in the presence of pathology as a possible risk factor that requires further investigation.
Decision Support Techniques↗
Analysis of moment/force ratios in the mechanics of tooth movement.
Orthodontic tooth movement is analyzed by means of the center of rotation model and the concept of moment/force ratios. Several equivalent force systems are considered at both the bracket and the center of resistance of the tooth. When moment/force ratios are evaluated at the bracket, the laws of physics appear to be suspended: inconsistencies occurring as single forces applied at different points claim equivalent results and pure translational movements purport to be nonzero moment/force ratios. These paradoxes can be reconciled only if the moment/force ratios are analyzed at the center of resistance of the tooth. Here, all of the moments applied to the tooth by the force system are included in the analysis. Only when the force system is evaluated around the center of resistance of the tooth is the concept of moment/force ratios consistently correct.
Biomechanical Phenomena↗
Treatment following loss of second premolars.
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Bicuspid↗
Neonatal respiratory distress. A simple cradle for micrognathia and glossoptosis.
Infants born with micrognathia and glossoptosis may present as a grave emergency, with recurrent bouts of respiratory distress and cyanosis. The management of this condition is discussed, with particular reference to conservative measures. A new cradle has been designed to facilitate the management of these children during the neo-natal period.
Airway Obstruction↗
Overjet stability after treatment of Class II Division 1 malocclusions.
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Humans↗