Treatment strategy analysis and prevalence of root canal variation of maxillary second molars from a native Chinese population

The anatomical morphology of root canal systems in maxillary second molars (MSMs) is complex and shows diverse variations, which leads to challenging root canal treatments that could end in failure. Therefore, understanding the diverse nature of root canal anatomy is an important prerequisite for the successful treatment of MSMs. The fused root is among the most prevalent root variants of MSMs, exhibiting a distribution rate ranging from 23.9% to 42.25% within the Chinese population. Fused roots are often accompanied by complex root canal fusion, as the incidence of root canal fusion in type Ⅵ fused roots of MSMs is 90.5% within the Chinese population. There are several treatment strategies for the root canal variations in MSMs, including the location of the root canal orifice and clearing and filling of the isthmus within the fused root canal. Cone-beam computed tomography, dental operating microscopy, and digital dynamic and static navigation technologies can be employed to accurately identify the root canal variations associated with fused roots. In the treatment of fused root canals, for the cleaning and filling of the isthmus in fused canals, enhanced chemical preparation, timely application of laser-assisted irrigation, photodynamic therapy, and microapical surgery significantly improve the success rate of endodontic procedures. The treatment strategies and prevalence of root canal variation of MSMs from a native Chinese population were summarized in this paper to provide guidance and reference for the successful treatment of MSMs.