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': 'Cavity varnish is indicated under amalgam restorations to: \nSelect and explain. \nA. Prevent galvanic currents from reaching the pulp, B. Seal dentinal tubules and improve the marginal seal of the restorations, C. Improve retention, D. Act as an effective thermal insulator', 'role': 'user'}, {'content': 'Answer: B \nExplanation: A varnish is an organic copal or resin gum suspended in solutions of ether or chloroform.\nVarnish is indicated to seal the dentinal tubules, act as barrier to protect the tooth from chemical irritants\xa0from cements and reduce microleakage around\xa0restorations.\nVarnish is contraindicated under glass ionomers as\xa0they interfere the bonding of tooth to these cements.\nWith restorative resins varnish is not used because the\xa0varnish liners dissolve in the monomer of the resin and\xa0also they interfere in their polymerization process.\nLiners are indicated to protect pulp from chemical\xa0irritants by sealing ability and stimulate formation of\xa0reparative dentin.\nCommonly used liners are zinc oxide eugenol, calcium\xa0hydroxide, flowable composites and glass ionomers.\n\nNisha Garg, Amit Garg. Textbook of Operative Dentistry.\xa0 Edition 3. Page:222', 'role': 'assistant'}]