Antczak-Bouckoms A A, Tulloch J F, Berkey C S
Department of Health Policy and Management, Harvard School of Public Health, Boston, Massachusetts 02115.
J Clin Periodontol. 1990 Aug;17(7 Pt 1):446-53. doi: 10.1111/j.1600-051x.1990.tb02343.x.
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.
成对或多个器官（牙弓、象限、牙齿）的存在以及许多牙科疾病的慢性性质表明可采用分口设计（每个受试者接受两种或更多治疗，每种治疗应用于口腔的不同区域）和交叉研究设计（每个受试者依次接受两种或更多治疗）。虽然这些设计有可能节省资源，但如果不满足一些严格的科学和统计学假设，其效用可能会被抵消。使用分口和交叉设计的主要前提是：（1）待研究的疾病相对稳定且分布均匀；（2）对于交叉研究，待评估治疗的效果是短期的或可逆的，对于分口设计，治疗效果是局部的。影响这些设计合理使用的其他重要因素包括：治疗顺序和分配的方法以及所采用的交叉规则；患者分配、患者和观察者的盲法；顺序效应的评估，包括周期、残留或溢出效应；统计分析的选择、所使用的样本量，以及失访患者或错误数据点的特殊重要性。本研究的目的是回顾3种期刊中使用分口或交叉设计的研究，以确定这些研究设计所依据的假设在牙科研究中是如何被考虑和应用的。大多数研究在治疗分配和顺序安排上采用了适当的方法；然而，许多研究在数据的统计分析中未能充分利用这些研究设计。此外，很少有研究考虑顺序效应的可能性或通过盲法程序减少偏倚。
