Gunsolley J C, Yeung G M, Butler J H, Waldrop T C
Baltimore College of Dental Surgery, University of Maryland, Department of Periodontics, Richmond, VA 21201-1586, USA.
J Periodontol. 2001 Mar;72(3):349-53. doi: 10.1902/jop.2001.72.3.349.
Following root planing and scaling many studies have implied an association between a loss of clinical attachment at sites with initially shallow pockets (1 to 3 mm) and gains in attachment level for deeper probing depths. However, these effects are also consistent with a statistical phenomenon referred to as regression towards the mean. This principle suggests that extreme values will moderate the next time they are recorded. The purpose of this report was to estimate the effect that regression towards the mean has on perceived changes in attachment level after root planing and scaling.
During the initial examination, 2 different investigators conducted 2 full-mouth probings. Two quadrants were randomly selected to be root planed and scaled until the root surfaces were smooth by tactile touch of an explorer. The 2 remaining quadrants were not treated. At 4 to 6 weeks after treatment, another full mouth probing was done. An examiner who was blind to the quadrants that had been scaled measured attachment level and probing depth after therapy. This study design provided periodontal measurements before and after root planing and scaling, measurements before and after a period of 4 to 6 weeks of no therapy, and duplicate measurements at the beginning of the study.
Using the repeat examination when no true change could occur, shallow sites (< or =3 mm of probing depth) showed average negative differences between repeat attachment level measurements (-0.23 mm), which mimicked loss of periodontal attachment. Deep sites, (>6 mm) showed average positive values (0.40) mimicking gain in attachment level. These results suggest that regression towards the mean is a significant effect in this data set. Both shallow non-scaled and scaled sites had similar differences in repeat measures (-0.28 mm, -0.25 mm) which were also similar to and not statistically different from changes after therapy for both non-scaled (-0.21 mm) and scaled sites (-0.08 mm). Thus not only does this data set exhibit regression towards the mean, but it explains the majority of perceived loss of periodontal attachment after scaling at sites that have minimal probing depth.
These results suggest that the majority of perceived loss of attachment due to scaling at sites of minimal probing depth that have been reported in many studies may be due a statistical phenomenon called regression towards the mean.
在根面平整和龈下刮治后，许多研究表明，初始牙周袋较浅（1至3毫米）部位的临床附着丧失与较深探查深度处附着水平的增加之间存在关联。然而，这些效应也与一种称为均值回归的统计现象一致。该原理表明，极端值在下次记录时会趋于缓和。本报告的目的是评估均值回归对根面平整和龈下刮治后附着水平感知变化的影响。
在初始检查期间，两名不同的检查者进行了两次全口探查。随机选择两个象限进行根面平整和龈下刮治，直到用探针触诊根面光滑为止。其余两个象限不进行治疗。治疗后4至6周，进行另一次全口探查。一名对已刮治象限不知情的检查者在治疗后测量附着水平和探查深度。该研究设计提供了根面平整和龈下刮治前后的牙周测量数据、4至6周未治疗前后的测量数据以及研究开始时的重复测量数据。
在无真实变化的重复检查中，浅部位（探查深度≤3毫米）在重复附着水平测量之间显示出平均负差异（-0.23毫米），这模拟了牙周附着丧失。深部位（>6毫米）显示出平均正值（0.40），模拟附着水平增加。这些结果表明，均值回归在该数据集中是一个显著效应。浅的未刮治部位和刮治部位在重复测量中的差异相似（-0.28毫米，-0.25毫米），这也与未刮治部位（-0.21毫米）和刮治部位（-0.08毫米）治疗后的变化相似且无统计学差异。因此，该数据集不仅表现出均值回归，而且解释了在探查深度最小的部位刮治后大多数感知到的牙周附着丧失。
这些结果表明，许多研究报告的在探查深度最小的部位刮治导致的大多数感知到的附着丧失可能是由于一种称为均值回归的统计现象。
