This issue depends on the tooth and periodontal condition, and is not an absolute conclusion. If you have caries, you should repair it as early as possible, because the cavity can stop the development of caries lesion after repair, restore the function of the tooth as early as possible, and keep the integrity of the tooth. If not treated in time, the lesion will become bigger and bigger, from superficial caries to deep caries, and it will be sensitive to the stimulation of food such as cold, hot, sour and sweet; when the damage reaches the pulp, it will cause pulpitis, and the tooth pain will be very serious; when the lesion develops further, it will cause apical inflammation, periapical abscess, even jaw bone pulpitis, and tooth loss. Tooth decay or even missing will affect chewing, increase the burden of gastrointestinal, and then affect the health. Moreover, there is a large amount of bacteria and pus in the tooth decay, which is a potential lesion, and it can cause sepsis or bacteraemia when the resistance of the body is reduced. The filling can terminate the occurrence and development of these diseases, so it is necessary to fill the teeth early when suffering from caries. In addition, due to the clinical manifestation of caries, it is divided into primary caries and secondary caries. Acute caries is a kind of primary caries, and its lesion progresses quickly. In children or young people, the lesioned tooth tissue is light in color, soft and moist, and the pulp tissue cannot or rarely forms restorative dentin due to the rapid lesion, so it is easy to be infected and pulp lesion occurs. At the same time, children with caries hinder food chewing and nutrient digestion and absorption, and its role of stimulating jaw bone growth and development decreases due to the decrease of chewing power. Patients who receive radiotherapy on face and neck, patients who suffer from Schelling’s syndrome and patients who have reduced salivary secretion due to other reasons, their caries develops rapidly and often involves most of the teeth, which is called fierce caries. For these patients suffering from acute caries and violent caries, they should be treated with filling as soon as possible to stop the rapid development of caries. Scaling is important to help clean up the tartar, calculus or anything that accumulates near the teeth and gums for a long time, some people want to feel whiter after cleaning, but it will not have a rapid development compared to the caries. However, for those patients who have a lot of calculus, it is recommended to scaling to remove those calculus and soft tartar first so that the tooth can be filled for a long time. Also, some affected teeth need periodontal treatment, which may require subgingival scaling, and if the filling is filled first, the filling material may be scraped off. In addition, if the gums are red and swollen, once the filling touches the gums, it may bleed continuously, making it impossible for the doctor to operate, so it is necessary to scaling first. Whether to fill or scaling first depends on the doctor’s need for dental treatment.