WASHINGTON — American drones were devastating the upper ranks of Al Qaeda, his men were killing suspected spies, and Osama bin Laden wondered: Could an Iranian dentist have planted a tracking device in his wife’s tooth?

“The size of the chip is about the length of a grain of wheat and the width of a fine piece of vermicelli,” he wrote, using the nom de guerre Abu Abdallah.

A few paragraphs later, Bin Laden signed off and then added, “Please destroy this letter after reading it.”

The letter was among thousands of pages of documents and other materials seized by Navy SEALs during the raid on Bin Laden’s compound in Abbottabad, Pakistan, in May 2011, and it was declassified on Tuesday with 112 other pieces of writings and letters found in the Qaeda leader’s hide-out.