Objective to investigate the relationship between toothabrasion and long-term chewing betel nut.
目的：探讨长期咀嚼槟榔与牙体磨损的关系。
2
The scroll wrap is the main movement part of compressor, only have the tooth, have no abrasion, thus the life is longer, so this is free maintenance compressor.
涡旋压缩机主要运动件涡盘只有啮合没有磨损，因而寿命更长，被誉为免维修压缩机。
3
On the other hand, a hard-bristled brush, coupled with vigorous brushing can result in recession of the gums and the abrasion of tooth enamel and exposed root surfaces.