retainer with balls

例句：

1. 1. The dentist used a retainer to hold her tooth in place.
   牙医用一个保持器来固定她的牙齿。
2. 2. The patient needed a retainer after the surgery to keep his jaw closed.
   病人在手术后需要一副保持器来保持他的下巴闭合。
3. 3. The retainer helped her regain her confidence after the accident.
   这个保持器帮助她在事故后恢复了自信。