Most of the gap between teeth at 40 years old is caused by periodontitis, which can be corrected by correcting the way of brushing, systematic treatment of periodontitis, traditional wire braces or slotless invisible way. 1. Correct the way of brushing: 40 years old teeth gap, if it is caused by dental calculus, you need to improve their brushing way, take the correct way of brushing. Keep good oral hygiene. 2. Treatment of periodontitis: chronic periodontitis treatment needs to be first scaling to clean up the gums of the calculus, and then a week later for subgingival scraping. Local use of chlorhexidine acetate solution to control plaque, with oral amoxicillin and other drugs to fight infection. The medication needs to be directed by a doctor. The treatment of chronic periodontitis requires systematic periodontal therapy, and it is recommended to seek medical attention in time to terminate the disease process. 3. Orthodontics: When you are 40 years old and have a big gap between your teeth, you can close the gap through orthodontics after you have resolved the periodontitis and other dental diseases. At present, there are two kinds of orthodontic methods: traditional wire braces and invisible bracketless braces, which can be chosen according to your actual situation. 40 years old gap between the teeth can first go to the regular hospital stomatology clinic, by the doctor after examination to determine the orthodontic treatment program.