The second premolar is treated according to the situation, if the tooth decay is shallow and the cavity is small, you can not do the crown; if the tooth is fragile, it is recommended to do the crown. 1. No crown: If the tooth decay is shallow and the cavity is small, you can fill the tooth directly after removing the decayed tooth tissue, but don’t eat too hard food with your teeth to prevent the filling material from falling off. 2. Do crowns: teeth after root canal treatment due to the loss of nutrient supply will become more fragile, it is best to do crowns can be very good to protect the teeth, to prevent the teeth from splitting. Dental crowns are best to choose all-porcelain teeth, all-porcelain teeth will not lead to black lines on the gums, and does not affect the CT, MRI examination. Whether the second premolar needs to be crowned or not, it is best to visit the hospital in time and choose the most reasonable treatment method under the advice of professional physicians.