Which of the following practices is most effective in preventing cross-contamination in the dental office?

Changing gloves after each procedure is essential for preventing cross-contamination in a dental office because it directly reduces the risk of transferring pathogens from one patient to another. Gloves act as a barrier to protect both the dental professional and the patient from potential infections. Once a procedure is completed, the gloves can harbor contaminants from the patient's mouth, blood, or other bodily fluids. By changing gloves, dental professionals ensure that they are not introducing any microbes, viruses, or bacteria to the next patient, thereby significantly lowering the chances of cross-contamination.

While the other practices listed do contribute to overall infection control in a dental setting, they are not as significant in preventing cross-contamination as the practice of changing gloves. Washing hands after every patient is important for hygiene, but without appropriate glove changes, there is still a risk of transferring pathogens. Wearing a mask helps to protect against respiratory droplets but does not impact skin-to-skin or instrument contact. Using disposable instruments, although reducing the risk of cross-contamination, is not always feasible for all types of dental procedures. Hence, changing gloves after each procedure stands out as the most effective individual practice in preventing cross-contamination specifically.