Abstract: Objective: To learn the effect of decidous tooth decay on the eruption time of premolar. Methods: Children aged 5-6 were selected in 2010. Decidous teeth were examined until the permanent teeth were completed. They were divided into caries free group, shallow caries group, and deep caries group. The children completed oral examinations at least 4 times during 2010-2017. The baseline data were obtained and a personal oral health record was established. The results were analyzed with SPSS20.0 software package. Results: Between 2010 and 2017, 1,549 children were surveyed, including 762 boys and 787 girls. A total of 1473 maxillary first decidous molars, 1616 maxillary second decidous molars, 1851 mandibular first decidous molars, and 1686 mandibular second decidous molars were investigated. When the decidous molars were deep caries, the replacement time of the premolar was earlier than that without caries or shallow caries, and the average time was more than half a year earlier. The difference was statistically significant (P<0.05). Conclusion: Students of dental caries prevention and intervention is the key. Caries in decidous teeth need early treatment to maintain the integrity and the normal replacement of the teeth.

Key words: Caries in decidous teeth, Time of tooth eruption, Tooth eruption