22
Exercises in Critical Thinking
It is difficult to overstate the value of practice. For a new skill to become automatic or for new knowledge to become long-lasting, sustained practice, beyond the point of mastery, is necessary.
—Daniel T. Willingham
from Practice makes perfect perfect—
But only if you practice beyond the point of
perfection. Am Educator 2004; Spring:31.
Problems
The following excerpts from the dental literature are intended to illustrate some of the concepts introduced in the preceding chapters. To keep the section reasonably brief, the examples have been extracted from papers, and much detail has been omitted. In some instances, the authors discuss the weaknesses or strengths of the particular approach they employed in their article, which is not included here. The intent in presenting these examples is not to criticize or commend the articles in question, but rather to show how the arguments, strategies, and ideas discussed in this book appear in the dental (or popular) literature. To provide a wide range of examples in a reasonable amount of space, only select material was extracted from the papers. Often the problems contain a conclusion drawn from the abstract or summary of the paper and select material from other sections of the paper, such as Materials and Methods and Results, relevant to the conclusion. In approaching these problems, you should assume that the aspects of the conclusions that are not concerned with the information presented in the Materials and Methods and Results extracts are not problematic. For example, in Problem 1 assume that bone gain was actually achieved, even though it is not clear from the material that is presented how bone gain was measured, the time fluoride was applied, and so forth.
Problem 21
Addy M, Carpenter R, Roberts WR. Management of recurrent aphthous ulceration: A trial of chlorhexidine gluconate gel. Br Dent J 1976;141:118–120.
Some relevant information extracted from the paper includes:
“Thirty patients agreed to participate in the trial. They were chosen from a larger group of aphthous-ulcer sufferers who regularly attended dental school and who experienced regular and frequent ulceration. The trial was conducted in a double-blind crossover manner employing an active gel containing 1 percent chlorhexidine gluconate in an aqueous base. Each gel was used for a period of 35 days with 14 days between the two preparations to avoid carry-over effects. At the commencement of the trial each patient was examined and then verbally instructed on the use of gels. Thus, each gel was to be used 3 times a day after meals. The patients were requested to place approximately 2.5 cm of the gel on the index finger, carry it to the mouth and allow the gel to distribute itself throughout the mouth, any residue being swallowed. The patients were also instructed to record the number and duration of the ulcers and to describe the discomfort experienced according to an arbitrary scale of: 1 = uncomfortable; 2 = fairly painful; 3 = very painful.”
See the results in Table P-1. The difference in means of 0.27 between the chlorhexidine treatment and the placebo treatment was significant (P < .05).
From the Discussion:
“Chlorhexidine gluconate as a 1 percent gel produced a significant reduction in the duration and discomfort of ulcers in a group of 20 patients when compared with a placebo gel.”
Identify the experimental design and discuss any problems that there might be in the analysis of the data.