Clinical studies in orthodontics An overview of NIDR-sponsored clinical orthodontic studies in the US

A number of clinical trials sponsored by the National Institutes of Health (NIH) use rigorous methods of data acquisition and analysis previously developed in fundamental biology and the physical sciences. The naive expectation that these trials would lead relatively rapidly to definitive answers concerning the therapeutic strategies and techniques under study is dispelled. This presentation focuses on delineating differences between the study of central tendencies and individual variation, more specifically on the strategy to study this variation: measure additional sources of variance within each patient at more timepoints and perhaps with greater precision. As rigorous orthodontic research is still in its infancy, the problem of defining the proper mix between prospective and retrospective trials is discussed. In view of the high costs of prospective clinical trials, many of the questions germane to orthodontics can be answered by well-conducted retrospective trials, assuming that properly randomized sampling procedures are employed. Definitive clinical trials are likely to require better theoretical constructs, better instrumentation, and better measures than now available. Reasons for concern are the restricted resources available and the fact that current mensurational approaches may not detect many of the individual differences. The task of constructing sharable databases and record bases stored in digital form and available either remotely from servers, or locally from CD-ROMs or optical disks, is crucial to the optimization of future investigations.     

Clinical studies of plaque control agents: an overview.

Dental plaque is massed packed bacterial cells which accumulate on the supra- and subgingival surfaces of the teeth as well as on the oral mucosa. The microorganisms of plaque have been shown to be associated with both dental caries and periodontal disease. This overview of clinical studies of plaque control agents reviews the properties and effects of chemical compounds which have demonstrated a potential for the control of plaque microorganisms. The search for clinically effective antiplaque agents has been stimulated by findings in laboratory and animal studies of plaque dynamics. Based upon these in vitro and in vivo experiments, chemotherapeutic agents such as antibiotics, antiseptics, enzymes, detergents, bacteriosides, antimetabolites, and oxidizing agents have been evaluated against human plaque microorganisms using the ultimate biological model -- man. Continued study of chemotherapeutic agents should be encouraged because many of these drugs have been shown to be safe for human use and may require only the development of a delivery system to potentiate their concentration in a specific local site. Use of these chemotherapeutic agents, which can be self-administered, becomes an attractive way of providing the public with a cost-effective method of preventing caries and periodontal disease.     

Further studies in retention of the orthodontic band.

A statistical analysis of 1,976 conventional orthodontic bands cemented to the teeth of 102 patients was carried out to try to establish the relationship of sex of the patient, age of the patient, and the type of malocclusion to the retention of the orthodontic band. The effect of treatment time and the presence or absence of extraoral traction on band recementation were also considered. The results obtained from the study led to the following conclusions: 1) There is no significant difference in the degree of band recementation occurring during orthodontic treatment between girls and boys. 2) There appears to be a tendency for bands to be recemented less frequently in patients 17 years of age and over. A larger sample would be necessary before being more definite. 3) The Class II, Division 2 type of incisor relationship may predispose to a higher rate of band recementation. Once again a greater sample size would be essential to be more categorical. 4) The percentage of bands recemented increased as the duration of treatment increased. 5) The use of early Kloehn cervical facebow therapy leads to a higher rate of band recementation on the maxillary molars.     

Sample size estimation: an overview with applications to orthodontic clinical trial designs

Proper sample size estimation is an important part of clinical trial methodology and closely related to the precision and power of the trial's results. Trials with sufficient sample sizes are scientifically and ethically justified and more credible compared with trials with insufficient sizes. Planning clinical trials with inadequate sample sizes might be considered as a waste of time and resources, as well as unethical, since patients might be enrolled in a study in which the expected results will not be trusted and are unlikely to have an impact on clinical practice. Because of the low emphasis of sample size calculation in clinical trials in orthodontics, it is the objective of this article to introduce the orthodontic clinician to the importance and the general principles of sample size calculations for randomized controlled trials to serve as guidance for study designs and as a tool for quality assessment when reviewing published clinical trials in our specialty. Examples of calculations are shown for 2-arm parallel trials applicable to orthodontics. The working examples are analyzed, and the implications of design or inherent complexities in each category are discussed.     

Bending deformation studies of orthodontic wires.

Bending deformation has been measured for orthodontic wires ranging in diameter from .010 to .051 inch. Results establish a revised expression for Young's modulus and show that either the stiffness tester or the torque meter will yield essentially the same measured values of bending properties. The dependence of test span length in determining Young's modulus and flexural yield strength is discussed.     

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目的研究成人错畸形患者的心理状态,探讨解决方案。方法选择2007年1月至2008年12月在大庆油田总医院集团五官医院口腔科和大庆油田总医院口腔正畸科就诊的成年错畸形患者30例,应用汉密顿焦虑(HAMA)、汉密顿抑郁(HRSD)量表对成人口腔正畸患者矫治前后进行心理状况评定。结果矫治前患者HAMA、HRSD的测量结果明显高于正畸矫治加心理支持治疗后的结果,其差异有统计学意义(P<0.05)。结论成人正畸患者在治疗前普遍存在焦虑、抑郁等临床心理问题,正畸矫治加有针对性的心理支持可改善患者的心理问题。     

Clinical radiography in the orthodontic practice

One practitioner's approach to minimizing patient exposure in diagnostic x-ray procedures in an individual orthodontic practice.     

Friction and orthodontic mechanics: clinical studies of moment and ligation effects

The efficiency of tooth movement associated with orthodontic sliding mechanics can be compromised by friction between arch wire and tube or bracket slot. The described studies measured the apparent coefficient of static friction (μ_a) during sliding along an arch wire. Known moments were applied to simulate tooth tipping. Measurements tested whether intraoral vibration during gum chewing reduced friction. The first experiments measured intraoral friction associated with the sliding of 4 and 8 mm stainless steel (SS) tubes along a SS auxiliary arch wire, in 10 subjects. Mean intraoral μ_a for 4 and 8 mm tubes were 0.12 (SD = 0.04) and 0.17 (SD = 0.05), respectively. Analysis of variance (ANOVA) showed that μ_a was significantly higher (P < 0.001) for the longer tubes. Although intraoral vibration decreased μ_a compared with bench-top tests (P < 0.001), frictional resistance was never completely eliminated.

The second experiments studied the effects of ligation. Ten professionals performed exercises to characterize average tight and loose SS ligation forces. These ligation forces (F_{N Ligation}), and those associated with elastic ligation, were reproduced by a calibrated operator in a modified intraoral device, where SS orthodontic brackets slid along a SS auxiliary wire. Ten subjects chewed gum with the device in place. Nested ANOVA and Tukey Honest Significant Difference tests determined the effects of ligation type and environment. No significant differences (P > 0.01) were found between ex vivo and intraoral μ_a values for tight and loose SS ligation. Intraoral values for μ_a were significantly greater than ex vivo values (P < 0.001) for elastic ligation. Overall, the results suggested that vibration introduced by gum chewing did not eliminate friction. Tipping moments and ligation forces were equally significant in determining frictional forces. As well, there was considerable intraoperator variation in F_{N Ligation} for SS ligatures. Variations in clinical ligation forces are likely to be equal or greater than these experimental data and have potential to affect treatment efficiency during orthodontic sliding mechanics.     

Clinical experience with direct-bonded orthodontic retainers.

The experience obtained in clinical evaluation of forty-three direct-bonded mandibular canine-to-canine retainers after a minimum observation period of 1 year (range, 1 to 2.5 years) is summarized. Results indicate that the bonded retainer has all the advantages of a fixed soldered retainer, in addition to being invisible. Patient acceptance was excellent, and the failure rate in terms of loose retainers was low. Also, for a number of other retention problems, direct bonding with different types of lingual wire seems to open up a range of promising new possibilities.     

A clinical evaluation of a locking orthodontic facebow.

Standard orthodontic facebows may accidentally detach from the appliance buccal tubes at night; this could reduce the effectiveness of extra oral traction and occasionally cause an injury. To try and prevent facebow detachment at night a facebow with a locking mechanism was introduced. This study assessed the ability of 706 consecutively treated patients to learn to wear and use this facebow. The facebows were fitted in 9 different practices supervised by 12 orthodontists. Data from the patients and orthodontists were collected over a 2-year period and covered approximately 166,550 nights. All the orthodontists were able to fit and adjust the facebow; a total of 697 patients successfully used the facebow. Accidental detachment of the facebow at night was reported to be less than 1%. This indicates a significant improvement in the safety of the facebow and should help to improve compliance by increasing the number of hours of wear achieved by the patients.     

Neuromuscular occlusion in the orthodontic treatment of craniomandibular disorders. A clinical case

In the last few years, it has been observed a considerable increase of cranio-mandibular disorders which presently represent one of the most common commitments for dentists and, in particular, for orthodontists. The aim of this paper is to evaluate the efficacy of Jankelson's therapeutic protocol, followed by an orthodontic treatment, in a patient with cranio-mandibular disorders associated with occlusal pathologies. The cranio-mandibular electromyography and kinesiography promoted by Jankelson provide objective diagnostic measurements, while tens, relaxing masticatory muscles, allows a correct recording of myocentric occlusion. In this case, the authors utilise these devices, according to a well established diagnostic and therapeutic protocol. The first step is purely gnatologic, and consists of the application of an orthotic to temporarily treat pain and dysfunction. The following phase is a simple orthodontic treatment representing the final therapy. Orthodontic and/or prosthodontic rehabilitation of dentition, in fact, is the ultimate step of the therapeutic scheme which allows long-lasting RESULTS.     

Lower incisor extraction in orthodontic treatment. Four clinical reports

Four different clinical cases in which the treatment plan finally selected included the extraction of one lower incisor and reduction of upper anterior tooth width.     

Expert systems in orthodontic clinical diagnosis

Computer-aided diagnosis of orthodontic anomalies is of particular interest in the screening of potential patients. General practitioners and public dental health workers would find considerable benefit in a reliable automated system capable of reflecting the clinical assessments of orthodontists. This study investigates the application of an expert system (Xpert Rule) to the assessment of treatment need using thirteen traits of malocclusion to construct a knowledge base. Decision trees were generated using a pruning option available with the expert system. The results of the study are encouraging and suggest that an expert system is able to generate a useful clinical screening device. Further modification of the knowledge base is required to provide a broader range of case types, particularly those of less common occurrence. It is also suggested that the random aggregation of cases is not the most effective means of developing a knowledge base.