Root apex is an area of primary importance for an endodontist. When a tooth erupts in the oral cavity the apical foramen undergoes anatomical changes with age. Root development is completed and the root apex is closed three years after eruption of the tooth. Endodontic practice is influenced to a great extent by different stages of root development and the type of tissue present within the roots. Open apices pose a challenging problem for the success of root canal treatment because they favour the extravasation of the irrigating solution and/or sealer into periradicular tissues, thus jeopardizing apical healing. Regenerative endodontics (revascularization/pulpal regeneration) is a straightforward approach accomplished with currently available instruments and materials. A literature review suggests that Mineral Tri oxide Aggregate (MTA) is the most favourable and recommendable material for single-visit apexification, even in cases when regenerative endodontics cannot be performed. A plus point of MTA is its biocompatibility and hermetic apical seal with no micro-leakage. It should be considered as an effective alternate for treating immature teeth with necrotic pulps. Treatment of a tooth with open apex poses multiple challenges. However, it is not easy to decide which material should be used: Calcium hydroxide, Mineral Tri oxide Aggregate, Biodentine, Platlet Rich Fibrin (PRF), or White Portland Cement (WPC). The choice of treatment regimen depends on several factors, e.g. individual cases, experience of the operator, familiarity with handling various materials, and patient's availability for follow-up appointments. This review highlights various challenges in the treatment of open apex, with emphasis on MTA compared with other materials.