Epidemiology of research for temporomandibular disorders.

A systematic review was performed in response to a request by the National Institute of Dental Research to evaluate in broad terms the strength of evidence regarding therapy for temporomandibular disorders (TMD). This report describes the epidemiology of research for TMD in broad terms indicating the total number of citations, the proportion related to therapy, and the distribution according to study design and language or country of origin. Medline and hand searching of article bibliographies and of selected journals produced the set of citations evaluated. From 1980 to 1992, there were more than 4,000 references to TMD, of which about 1,200 regarded therapy. Forty-one percent of the 1,200 references were classified as reviews and only 15% were clinical studies. Less than 5% (n = 51) were randomized controlled trials. This review identified a vast amount of literature on TMD with articles published in several different languages, indicating a worldwide interest in this problem. Because assimilation of this literature cannot be expected of the average practitioner treating patients who have TMD, or of most researchers in this area, it is likely not being used to its maximum potential. The literature on therapy for TMD consists primarily of uncontrolled observations of patients such as uncontrolled clinical trials, case series, case reports, and simple descriptions of techniques. It is generally agreed that such uncontrolled observations, while contributing to knowledge about therapy of TMD, are subject to considerable bias and thus difficult to interpret. If treatment of TMD is going to follow the trend in medicine to base patient-care decisions on evidence rather than expert opinion or pathophysiologic rationales, then more rigorously controlled clinical trials of most therapies will be necessary.

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.

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.

Issues in the economic evaluation of community water fluoridation.

Community water fluoridation has long been recognized as an effective public health intervention in the prevention of dental caries. The recently documented secular decline in dental caries, however, presents for policy makers the challenge of appropriately allocating limited health care resources between a variety of health care programs. Appropriate economic assessment of these alternatives becomes critical for rational distribution of such resources. Cost-benefit and cost-effectiveness analyses are techniques that, when used correctly, can guide policy makers facing such decisions. This paper reviews and critiques the published literature assessing the cost effectiveness and cost benefit of community water fluoridation using criteria developed for economic evaluation. Eight papers met the criteria for inclusion in the present study. In general, the articles failed to incorporate the declining prevalence of dental caries into their analyses and to fully document costs associated with water fluoridation. Treatment savings from dental care averted secondary to water fluoridation were not appropriately incorporated into the cost-effectiveness analyses, thereby overestimating the marginal cost associated with fluoridation. Specification of outcome measures to assess the consequences of water fluoridation failed to incorporate the dynamic nature of dental disease. Suggestions for improving the generalizability and usefulness of future cost-benefit and cost-effectiveness analyses are made.

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.

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.

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.

Cost-effectiveness analysis of periodontal disease control.

Cost-effectiveness analysis was used to evaluate alternative methods of periodontal disease control. The alternatives considered included non-surgical and surgical procedures as well as the use of antimicrobial agents. Data on costs were obtained from American Dental Association publications of average charges for periodontal services. The concept of quality-adjusted tooth-years (QATYs) was developed to provide an outcome measure which could be compared across treatments. The conclusions of this analysis are as follows: (1) Conservative non-surgical treatments for periodontal disease control not only have costs lower than surgical alternatives, as would be expected, but also maximize expected quality-adjusted tooth-years over a wide range of estimates; (2) antimicrobial therapy used as an adjunct to non-surgical treatment is likely to be both effective and cost-effective; and (3) quality of tooth-years is a critical consideration in the determination of outcome of periodontal treatment. For example, when tooth-years are not adjusted for quality, differences between treatments are diminished, and surgical treatment becomes as good as or better than more conservative treatments for some levels of disease severity.

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.