Which of the following statements about radiopaque bases or liners is true?

• A. All of the above are radiopaque
• B. Glass ionomer
• C. Zinc oxide
• D. Calcium hydroxide

Answer: (A)

Radiopacity on radiographs helps you see where a liner or base sits and to verify proper coverage and margins. Materials used as bases or liners are made radiopaque by adding heavy elements or radiopaque fillers so they show up clearly against tooth structure. Glass ionomer cements contain radiopaque glass particles (often strontium- or barium-containing glass), which makes them visibly radiopaque. Zinc oxide-based liners include radiopaque fillers and rely on the zinc oxide itself to contribute to radiopacity. Calcium hydroxide liners are formulated with radiopaque fillers such as barium sulfate, so they also appear on X-rays. Because each of these common liner/base materials has been designed to be radiopaque, all listed options are radiopaque.