Why did Anne say, “One thing is certain: it’ll be a while before Mrs. Van D. makes another dental appointment!”?

Without further context, it is difficult to determine the exact reason behind Anne's statement. However, based on the given statement, it can be inferred that Mrs. Van D. had a negative or unpleasant experience during her dental appointment that would deter her from making another appointment in the near future. This could be due to factors such as pain, discomfort, dissatisfaction with the dental services, or any other negative aspect related to her dental visit.