Acute pulpitis is more common at night and is known clinically as nocturnal pain. The specific reasons for this are described below: 1. It is busier during the day, and when dealing with daily affairs during the day, attention is distracted and there is no sensitivity to pain. When it is quieter at night, the level of activity is also lower, so the attention is shifted to dental problems and the pain is found to be particularly unbearable and more painful than during the day; 2. Sleeping in bed produces a change in body position, and the change in body position causes a change in pressure in the teeth. In the hard tissues of the teeth, the only pressure change that can be felt is pain, so it will feel more painful at night than during the day.