1, improper operation: the bow expander is a medical device that needs to be operated correctly, not in accordance with the requirements of the instructions for the correct operation, resulting in the bow expander does not turn.
2, instrument failure: the bow expander is a mechanical device, the instrument itself fails, will lead to the bow expander can not turn.
3, instrument aging: long-term use of the bow expander, the instrument will appear aging phenomenon, resulting in the rotation does not work. An arch expander is a medical device that is used to help patients expand the arch of their teeth to improve the occlusal relationship and appearance of the teeth.