What's wrong with changing toothbrushes?

Changing toothbrushes has once again aroused everyone's curiosity because of the TV series "Pi". The toothbrush was changed a long time ago. It is said that a couple had quarreled before. The wife will secretly take her husband's toothbrush to clean the toilet because of anger, and then she will replace the toothbrush that has been cleaned the toilet because of guilt. Just like in TV series, Lin's mother often changes Lin Dawei's toothbrush, and Lin Dawei is at a loss about the fact that his wife always changes his toothbrush. Because Lin's mother has a bad temper and Lin happens to be in high school, family quarrels are inevitable. So people naturally associate the change of toothbrush with the plot of changing toothbrush in TV series.