Effect of acid etchant composition and etch duration on enamel loss and resin composite bonding.
OBJECTIVE
To investigate the effects of different acid etchants' ability to condition enamel as gently as possible to remove a minimum of substance only, to produce a highly retentive pattern, and finally to ensure frosty appearance of the etched enamel for clinical control of the procedure.


METHODS
Two commercial uni-etch gels, Gluma 2000-1 and Scotchbond Multi-Purpose Etchant, were studied together with gels of 5, 10, 20 and 35% phosphoric acid and varying amounts of thickening agents in the 20% gel. Enamel loss was measured with a contact-free method by materials and etch duration, and the shortest etching times for dull frosty enamel appearance were determined. Shear bond strength (SBS) was measured after 24 hours' storage in water.


RESULTS
Enamel loss was very low with the commercial agents and increased with H3PO4 concentrations and with etch duration. While the commercial compounds produced no frosty enamel even after 120-second etch duration, the phosphoric acids produced frosted enamel after 15, 30, 60 and 120-second application of 35, 20, 10 and 5% acids, respectively. All etchants and etch durations tested produced effective retentive patterns. No differences in SBS were noted, and the failure modes were consistently cohesive in resin.
Uno
S
S
Department of Operative Dentistry, Hokkaido University, School of Dentistry, Sapporo, Japan.
Finger
W J
WJ
D000134:Acid Etching, Dental / Q000379:methods; D000704:Analysis of Variance; D003188:Composite Resins; D001840:Dental Bonding; D003743:Dental Enamel / Q000187:drug effects* / Q000648:ultrastructure; D005976:Glutaral; D008298:Maleates / Q000494:pharmacology; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010070:Oxalates / Q000494:pharmacology; D019815:Oxalic Acid; D010756:Phosphoric Acids / Q000494:pharmacology; D011109:Polymethacrylic Acids; D013997:Time Factors
D003188:Composite Resins; D008298:Maleates; D010070:Oxalates; C084019:Pekafill; D010756:Phosphoric Acids; D011109:Polymethacrylic Acids; C030272:maleic acid; C044372:Gluma; D019815:Oxalic Acid; C030242:phosphoric acid; D005976:Glutaral