The penultimate tooth may be the first molar or the second molar, both of which are very important in the oral cavity. If the first molar or the second molar is extracted and not restored in time, it will affect the chewing efficiency and the stability of the dental arch, as follows. 1. Chewing efficiency: As the grinding teeth for crushing and grinding food, the loss of the first or second molar may lead to a decrease in chewing efficiency, which in turn affects the health of the digestive system. 2. Stability of the dental arch: The teeth in the dental arch have a supporting role for each other, and the absence of the first or second molar will lead to the loosening and shifting of the neighboring teeth, which will easily lead to occlusal trauma, and in severe cases, the neighboring teeth may fall out. If any of the above symptoms occur, it is recommended to go to the hospital in time.