This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
[{'content': 'Which of the following material form hard tissue barrier? \nSelect and explain. \nA. IRM, B. Super EBA, C. Retroplast, D. None', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Two composite resin-based materials, Retroplast and Geristore have been advocated for use as root-end filling materials.\nThere is evidence that Retroplast promotes hard-tissue formation at the root apex, and some have suggested that this is a form of cementum.\xa0\nIn a limited number of case reports, Retroplast root-end fillings have demonstrated regeneration of the periodontium with a cementum layer over the root-end restoration.\nRetroplast is a dentin-bonding composite resin system developed in 1984 specifically for use as a root-end filling material.\nThe formulation was changed in 1990, when the silver was replaced with ytterbium trifluoride and ferric oxide. Retroplast is a two-paste system that forms a dual-cure composite resin when mixed.', 'role': 'assistant'}]