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
Most common pigment used in composite restorations are: 
Select and explain. 
A. Oxides of iron, B. Oxides of chromium, C. Oxides of aluminium, D. Oxides of barium
A: Oxides of iron
Answer: A: Oxides of iron 
Explanation: Inorganic oxides are usually added in small amounts to provide shades that match the majority of tooth shades. The most common pigments are oxides of iron. Numerous shades are supplied, ranging from very light shades to yellow to gray. Various color scales are used to characterize the shades of the composites. A UV absorber may be added to minimize color changes caused by oxidation. Darker and more opaque shades of composites cannot be cured to the same depth as the lighter translucent shades.