Nd: YAG laser for debonding ceramic orthodontic brackets.
BACKGROUND
The purpose of this study was to develop an effective method for debonding ceramic orthodontic brackets with a high-peak power Nd:YAG laser.


METHODS
Two types of ceramic brackets (single crystal and polycrystalline) were bonded to mandibular bovine teeth with 2 types of bonding resins (4-META/MMA and Bis-GMA). The laser was applied to 2 points on each bracket, each with a 1-pulse-per-second shot. Bond strength and thermal effects of the laser on the dentin surface were assessed at 3 laser energy levels: 1.0, 2.0, and 3.0 joules (J). Shear tests were performed on the irradiated test group and on a nonirradiated control group. ANOVA was used to determine significant differences.


RESULTS
The shear test (P < .05) showed that every specimen in the 2.0-J and 3.0-J groups underwent a significant decrease in bonding strength compared with the nonirradiated group. However, the 1.0-J group did not exhibit any such difference. In the 2 former groups, laser irradiation alone was sufficient to debond some specimens. No significant difference was found between bonding resins. The maximum temperature rise measured on the pulpal walls at the lasing points was 5.1 degrees C.


CONCLUSIONS
The application of a high-peak power Nd:YAG laser at 2.0 J or more is effective for debonding ceramic brackets.
Hayakawa
Kotaro
K
Department of Orthodontics, Tokyo Dental College, Masago, Chiba, Japan. kota@eruna.net
D000180:Acrylic Resins; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate; D001831:Body Temperature; D001896:Boron Compounds; D002417:Cattle; D002516:Ceramics; D003460:Crystallization; D017005:Dental Debonding / Q000295:instrumentation*; D003782:Dental Pulp; D003799:Dental Stress Analysis; D006358:Hot Temperature; D007834:Lasers; D008689:Methacrylates; D008768:Methylmethacrylates; D009354:Neodymium; D016910:Orthodontic Brackets; D019279:Resin Cements / Q000737:chemistry; D033081:Shear Strength
D000180:Acrylic Resins; D001896:Boron Compounds; D008689:Methacrylates; D008768:Methylmethacrylates; D019279:Resin Cements; C065742:Transbond; D009354:Neodymium; D017438:Bisphenol A-Glycidyl Methacrylate; C031172:4-META resin; C049495:Super-bond