clean as a hound's tooth

*clean as a hound's tooth

 and *clean as a whistle 
1. Rur. Cliché very clean. (*Also: as ~.) After his mother scrubbed him thoroughly, the baby was as clean as a hound's tooth. The car was as clean as a whistle after the Girl Scouts washed it.
2. Rur. Cliché innocent and free from sin or wrong. (*Also: as ~.) Jane's record was clean as a whistle; she had never committed even the smallest infraction.
See also: clean, tooth

clean as a hound's tooth

Completely blemish-free or honest. Another Southern expression; hounds' teeth are apparently cleaner than those of other species. Or perhaps just their canine teeth.
See also: clean, tooth