National Dental Examining Board of Canada (NDEB) Practice Exam

An expansion screw in a dental appliance is used to gradually widen the dental arch. This means that with each adjustment, the expansion screw will expand a certain amount depending on the treatment plan. Since the question specifies a single adjustment, it is important to note that each millimeter gained will require multiple adjustments over a period of time. Therefore, the other options, B, C, and D, which are all larger measurements, would require multiple adjustments to achieve that expansion. Option A, which is the smallest measurement, would require fewer adjustments to achieve a 0.25mm expansion. Therefore, A is the most accurate answer for a single adjustment.