Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 23 0 2026 05 30 4972 4972 Mohammad Mahdi Kiafar Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Farzaneh Afkhami 1. Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2. Department of Endodontics, School of Dentistry, The University of Queensland, Brisbane, Australia Sholeh Ghabraei Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran Ove A Peters Department of Endodontics, School of Dentistry, The University of Queensland, Brisbane, Australia Chun Xu Centre for Orofacial Regeneration, Reconstruction and Rehabilitation (COR3), School of Dentistry, The University Seyyed Ali Abaee Department of Endodontics, School of Dentistry, Tehran University of Medical Sciences, Tehran, Iran 2023 09 27 2023 10 28 This case report describes guided pulpal regeneration (GPR) of two immature permanent molar teeth with chronic apical abscess, thin dentinal walls, and open apices. Both teeth were treated with an identical protocol in two sessions, with minimum instrumentation with hand files, irrigation with 1.5% sodium hypochlorite (NaOCl), and application of 1:1 mixture of ciprofloxacin and metronidazole as an intracanal medicament, blood clot as a scaffold, and mineral trioxide aggregate (MTA) as the capping material. At the one-year follow-up, both treated teeth were asymptomatic. However, the root development procedure was different even in different roots of the same tooth, varying from only an increased thickness of dentinal walls to complete closure of the apex along with an increase in root length and dentinal wall thickness. It is concluded that the outcome of GPR is not completely predictable, and may vary among teeth with similar initial conditions and treatment approaches. https://fid.tums.ac.ir/index.php/fid/article/view/4972 https://fid.tums.ac.ir/index.php/fid/article/download/4972/2215