Factors Affecting the Shear Bond Strength of Orthodontic Brackets to Porcelain

Abstract

The aim of this investigation was to establish a regime for orthodontic bonding to feldspathic porcelain, which ensures adequate bond strength (6–8 MPa) with minimal damage on debond and consisted of an ex vivo investigation measuring the effects of porcelain surface preparation and thermocycling on shear bond strength of orthodontic brackets.

One-hundred-and-twenty feldspathic porcelain bonded crown surfaces were divided into 12 equally-sized groups to assess the effects of: (1) glaze removal, (2) application of hydrofluoric acid, phosphoric acid, or omission of acid treatment, and (3) silane priming upon the bond strength of premolar brackets bonded with Right-on ™ composite resin adhesive. Specimens were subjected to thermocycling and then to shear debonding forces on an Instron machine.

Removal of the porcelain glaze, or use of hydrofluoric acid, prior to bonding were found to be unnecessary to secure the target bond strength. Hydrofluoric acid application was associated with increased porcelain surface damage. Thermocycling caused a significant reduction in shear bond strength to porcelain (P < 0•001). The best regime for orthodontic bonding to feldspathic porcelain was to apply phosphoric acid for 60 seconds, and prime with silane prior to bonding. Usually the porcelain surfaces could be repolished.

Refereed Paper

Keywords:

• Etching
• Porcelain Bonding
• Surface Preparation
• Porcelain Fracture

Acknowledgments

The authors are grateful to Verona Needham for her secretarial assistance and to A Company® (Europe) for the provision of brackets used in this study. Steve Jones made every crown with care and skill.

Notes

Details of manufacturers:

A Company, 11436 Sorrento Valley Road, San Diego, California

3M Unitek, 2724 South Peck Road, Monrovia, California

TP Orthodontics, 100 Center Plaza, La Porte, Indiana

Ivoclar® Vita-matched (IPS Liechtenstein)

Panabond NP®, Panadent Ltd. London, UK

Keramo 3®, Renfert GmBH. Hilzingen, Germany

Ultradent® porcelain etch, Utah, USA