Shear/peel bond strength of repositioned ceramic brackets

Area of Science:

• Dental Materials Science
• Orthodontic Technology
• Biomaterials Engineering

Background:

• Proper orthodontic bracket placement is crucial for effective treatment.
• Bracket removal and rebonding are sometimes necessary procedures.
• Ceramic brackets offer aesthetic advantages but require careful handling during debonding and rebonding.

Purpose of the Study:

• To evaluate the residual bonding resin on ceramic bracket bases after electrothermal debonding.
• To determine the bond strength of rebonded ceramic brackets under various surface treatment conditions.

Main Methods:

• One hundred debonded single crystal ceramic brackets were assessed for residual resin using an adapted Adhesive Remnant Index (ARI).
• Brackets were divided into four groups for different treatments: silane coupling agent, heat plus silane, hydrofluoric acid plus silane, and heat plus hydrofluoric acid plus silane.
• Rebonded brackets on bovine teeth were tested for shear/peel bond strength using a universal testing machine.

Main Results:

• The Adhesive Remnant Index showed 79% of debonded brackets had no residual resin.
• The control group (unbonded brackets) exhibited significantly higher bond strength than all treated groups.
• Treatments with silane or heat plus silane yielded bond strengths greater than 9 MPa.
• Hydrofluoric acid treatments significantly reduced bond strength to below 2 MPa.

Conclusions:

• Electrothermal debonding often leaves minimal residual resin on ceramic bracket bases.
• Silane coupling agents, with or without heat, are effective for rebonding ceramic brackets.
• Hydrofluoric acid treatments are detrimental to the bond strength of rebonded ceramic brackets.