This is a saying used by people in the southern U.S. to imply that a person or organization is without corruption or completely honest.
Buford: I hear that the 34th Precinct of the AtlantaPolice Force has Cops on the take.
Bubba: No that's not true,I hear that they are Clean as a Hounds Tooth.
Much like a sweet tooth craves sweets, the ranch tooth craves Wendy's ranch chicken sandwiches. However this makes social situations awkward, as the foot-tall, hatted tooth is prone to shout out "RANCH!" in any situation.