Improving orthodontic bonding to gold alloy

Abstract

Flat tabs of cast gold alloy (n = 156) were subjected to either of three surface treatments: (1) roughening with diamond bur, (2) aluminum oxide sandblasting, and (3) sandblasting plus tin electroplating. Mandibular incisor edgewise brackets were bonded with Concise (BIS-GMA resin) (Unitek, Monrovia, Calif.) or Superbond C&B (4-META metal bonding resin) (Sun Medical Co. Ltd., Kyoto, Japan), or with Concise after application of an intermediate resin. All-Bond 2 Primers A and B (Bisco Dental Products, Itasca, III.), or B alone. All specimens were stored in water at 37° C for 24 hours, and 60 were then thermocycled 1000 times from 5° C to 55° C and back. The tensile bond strength testing was performed in a Lloyd 1000R machine (Fareham, Hants, England). Alignment and uniform loading during testing were secured by engaging a hook in a circular ring soldered onto the bracket slot before bonding. Similar control brackets ( n = 24) were bonded with Concise to extracted human premolars and lower incisors according to a routine procedure. Bond failure sites were classified by a modified ARI system. The results showed that sandblasting produced significantly stronger bonds to gold alloy than roughening with diamond bur. Superbond C&B provided significantly stronger bonds to gold alloy than Concise. There were generally insignificant differences in bond strengths between the water stored and the thermocycled specimens. Bond failures of Concise to sandblasted plus tin-plated gold alloy invariably occurred at the gold/adhesive interface, whereas those of Superbond C&B occurred within the adhesive or in the adhesive/bracket interface. The bond strengths obtained with Superbond C&B and sandblasted gold alloy surfaces were comparable to those of the brackets bonded to conventionally etched human teeth with Concise. Tin-plating improved the orthodontic bond strengths to sandblasted gold alloy only marginally. The bond strength of Concise to sandblasted gold alloy was significantly improved with the intermediate application of All-Bond 2 primers A and B. It is concluded that successful bonding to gold alloys is feasible with several combinations and clinical recommendations for bonding brackets and lingual retainer wires to high-noble alloy surfaces are discussed. (A M J O RTHOD D ENTOFAC O RTHOP 1995;108:510-8.)