Bonding characteristics of impacted versus erupted permanent teeth.

Erupted and impacted teeth from young (12 to 24 years of age) and older persons (over 50 years of age) were bonded by a standard technique using etching times of 0, 15, 30, and 60 seconds. Two subgroups of teeth were soaked for 7 days and compared with those in the remainder of the group. Test specimens were loaded in shear to bond failure by means of a testing machine with a 200- kg load cell and a crosshead speed of 5 mm/minute. Results indicated insignificant bond-strength differences between young-impacted and young-erupted teeth for any given etching time. Very small bond-strength differences were found for various etching times (15, 30, and 60 seconds). A significant difference was found between 24-hour soak and 7-day soak for the etching times of 30 and 60 seconds only.