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': 'First generation filler used in dental composite resin was: \nSelect and explain. \nA. Strontium glass, B. Colloidal silica, C. Inorganic quartz, D. Barium glass', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Various transparent mineral ﬁllers are employed to strengthen and reinforce composites as well as to\xa0reduce curing shrinkage and thermal expansion (generally between 30% to 70% by volume or 50% to\xa085% by weight of a composite). These include the so-called “soft glass” and borosilicate “hard glass”,\xa0fused quartz, aluminum silicate, lithium aluminum silicate (beta-eucryptite, which has a negative\xa0coeﬃcient of thermal expansion), ytterbium ﬂuoride, and barium (Ba), strontium (Sr), zirconium (Zr),\xa0and zinc glasses. The latter ﬁve types of ﬁllers impart radiopacity because of their heavy metal atoms.\xa0Quartz had been used extensively as a ﬁller in the early versions of dental composites.\nInorganic quartz was one of the first materials to be used and is often considered as first-generation filler.\nPhillips Science of Dental Materials ed 12 pg 280', 'role': 'assistant'}]