阅读下面材料，在空白处填入适当的内容（一个单词）或括号内单词的正确形式，并将试卷上的答案转写到答题卡上。
Scientists say we clean our teeth the wrong way. Researchers from University College, London found that most of the advice that dentists give us 61 (be) very different. They add that we have been cleaning our teeth the wrong way. The researchers looked at tooth-brushing advice in dental textbooks, toothpaste 62 (instruct) and dental clinics. They found five different 63 (base) ways of tooth-brushing and decided all of 64 were incorrect. Most of the methods involve 65 (move) the toothbrush along the teeth, with the brush moving round and round in small circular movements. The researchers said we should stop doing this and use a back-and-forth movement instead.
Aubrey Sheilam, lead author of the study and professor of dental public health, said: “The public needs to have sound information on the 66 (good) method 67 (brush) their teeth.” The research suggests not brushing teeth too much. More than twice a day damages the enamel on the teeth. The recommended time 68 brushing is no longer than three minutes each time. The research also says using too much pressure and brushing your teeth too hard will also damage teeth. Researchers also advised not cleaning your teeth immediately after eating. This is when acid is strongest in your mouth 69 this acid will damage teeth. A final recommendation was to clean the tongue too 70 it also has a lot of bacteria.