Four clinical cases of immature teeth that developed periradicular periodontitis or abscess underwent a conservative treatment approach, i.e. without canal instrumentation. Instead, only copious 2.5% NaOCl irrigation was performed. All cases presented herein developed mature apices after 7 months to 5 years after the initial treatment without complications, although narrowing canal space was observed. Our clinical observations support a shifting paradigm toward a conservative approach by providing a favorable environment for tissue regeneration. The mechanism of this continued development and formation of the root end is discussed.