A Brooklyn man bicycled up to an acquaintance he thought had stolen his “fronts,” or gold tooth caps, and slashed his right ring finger with a samurai sword, police sources said yesterday.

Ryan Mathesion, 29, confronted Henry Ferreya, 44, at Richmond and Etna streets in Cypress Hills shortly after 5 p.m. on March 22. Mathesion was busted Sunday.