The term 'Tooth Surface' can be broken down into two crossword solutions: ENAMEL (6 letters) and Mensa (5 letters). ENAMEL is the hard, protective outer layer of a tooth that helps to prevent decay. It is composed of minerals and is the hardest substance in the human body. Mensa is an organization that provides a forum for intellectually gifted people to meet and discuss topics of mutual interest. It is open to anyone who has achieved a score at or above the 98th percentile on an approved intelligence test.