Examination of enamel-adhesive interface with focused ion beam and scanning electron microscopy.
BACKGROUND
The purpose of this study was to observe, with a scanning electron microscope, the interface between enamel and orthodontic adhesive after focused ion-beam milling. In addition, enamel etched with phosphoric acid was compared with enamel conditioned with self-etching primer.


METHODS
Four freshly extracted human premolars were collected and pumiced by using rubber cups with fluoride-free paste, washed, and dried. The enamel of 2 teeth was etched with 37% phosphoric acid for 30 seconds, washed, and dried; the enamel of the other 2 teeth was conditioned with self-etching primer for 5 seconds. Stainless steel brackets were bonded with Transbond XT adhesive (3M Unitek, Monrovia, Calif) according to the manufacturer's instructions. The specimens were milled by focused ion beam and observed under the scanning electron microscope.


RESULTS
The scanning electron micrographs showed that 37% phosphoric acid seemed to produce more enamel loss than the self-etching primer. Moreover, the enamel-adhesive interface was more irregular when the enamel was etched with 37% phosphoric acid. Finally, a gentler etch pattern of the self-etching primer on the enamel surface was observed, and this conditioner could be used clinically for minimal intervention in the orthodontic bonding procedure.


CONCLUSIONS
Focused ion-beam milling to prepare samples allowed clear observation of the enamel-adhesive interface without artificial damage.
Vilchis
Rogelio José Scougall
RJ
Department of Operative Dentistry, Division of Oral Functional Sciences and Rehabilitation, School of Dentistry, Asahi University, Mizuho City, Gifu Pref, Japan. rogelio@dent.asahi-u.ac.jp
Hotta
Yasuaki
Y
Yamamoto
Kohji
K
D000134:Acid Etching, Dental / Q000379:methods; D001641:Bicuspid / Q000187:drug effects / Q000648:ultrastructure*; D001840:Dental Bonding; D003743:Dental Enamel / Q000187:drug effects / Q000648:ultrastructure*; D003764:Dental Materials; D017220:Dentin-Bonding Agents / Q000627:therapeutic use*; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016910:Orthodontic Brackets; D010756:Phosphoric Acids; D019279:Resin Cements / Q000627:therapeutic use*; D013499:Surface Properties
D003764:Dental Materials; D017220:Dentin-Bonding Agents; D010756:Phosphoric Acids; D019279:Resin Cements; C477790:Transbond XT; C030242:phosphoric acid