Abstract: Objective: To investigate the patterns and distributions of roots and root canals of fused roots at maxillary second molars (MSMs) in a northern Chinese population using cone-beam computed tomography (CBCT). Methods: The patients requiring CBCT inspections for diagnosis or treatment at Stomatology Hospital of Qingdao were selected. The gender and age of patients with fused root at MSMs were recorded and the configurations of root and canal of fused root at MSMs were probed. The collected data were analyzed to discover the root fusion variety in respect of genders, ages, and the patterns of fused root canal. Results: Totally 324 patients were involved in this study. The fused roots at MSMs appeared in 139 patients. The number of fused teeth was 222. The prevalence of each section of ages was different (P<0.05), mostly in the age section of 35 to 50 (70.9%). However, there was no significant difference between male and female, or right and left side. Following the 108 root canal mingling of 222 fused roots at MSMs, it was found the different patterns of root fusion inclined to different types of root canal mingling. Conclusion: MSMs commonly have a high prevalence of root fusion and canal mingling in a northern Chinese population. Understanding the various root and root canal patterns of fused root at MSMs is beneficial to the clinical practice.

Key words: Maxillary second molar, Fused root, Cone-beam computed tomography