The causes of old mouth ulcers, also known as recurrent mouth ulcers, are mainly the following: 1, local stimulation in the mouth, such as residual crowns, residual roots, bad restorations, bad orthodontics, etc. Removing these local stimuli can reduce the occurrence of mouth ulcers. 2, lack of nutrition, vitamins and also the lack of trace elements can lead to frequent occurrence of mouth ulcers. 3, genetic factors, both parents who are prone to The company’s main business is the development of a new product, a new product for the company.