Mechanical and electrothermal debonding: Effect on ceramic veneers and dental pulp

Abstract

This study compared the ability of three orthodontic debonding techniques for the removal of brackets from ceramic veneers without creating veneer damage. Three experimental groups included metal brackets debonded by either Howe pliers, lift off debonding instrument (LODI, 3M Unitek), or electrothermal debonder (ETD, “A” Company), as well as a group of electrothermally debonded ceramic brackets. It also evaluated and compared the intrapulpal temperature changes produced by electrothermal debonding metal and ceramic brackets. A sample of 95 extracted maxillary first premolars were prepared and restored with Mirage ceramic veneers (Chameleon Dental Products, Inc.). Veneer buccal surfaces were treated with 2.5% hydrofluoric acid, before silane application and bracket bonding with a no-mix resin. Specimens were thermocycled before debonding. All debonded specimens were examined under ×20 magnification for veneer damage. A thermocouple was positioned at the pulp chamber buccal wall to record temperature increases (due to ETD activation) through a digital thermometer. Results suggest that ETD provides predictable debonding of ceramic brackets with no veneer damage and minimal risk to the pulp. Removal of metal brackets through electrothermal debonding produced ceramic damage in 13% of cases, and elevated temperatures beyond the threshold of irreversible pulpal damage (5.5° C) in 46% of cases. Howe plier and LODI bracket removal are associated with ceramic damage incidence of 21% and 35%, respectively. (Am J Orthod Dentofac Orthop 1997;112:263-70.)