Regenerative endodontic treatment (RET) may not be suitable in some necrotic young permanent molars due to coexistent roots with closed and open apices, and/or inadequate apical bleeding in one or more roots. Here, we present a combined treatment approach utilising conventional root canal treatment in the closed-apex roots and RET on the open-apex roots of necrotic young molars. The closed-apex roots of 8 molars received root fillings, and their open-apex roots were treated with a regenerative endodontic procedure. In another molar, the failed RET on one root was retreated by conventional root canal filling, preserving other revitalised roots. After 4-6 years, all teeth showed periapical healing in the absence of clinical symptoms. The combined conventional and regenerative treatment approach can yield favourable healing outcomes in necrotic, young molar roots with different levels of apical closure. Likewise, failed revitalised roots can be retreated separately with conventional root filling.