Tissue reaction to primers used in the "single-step" bonding system

Area of Science:

• Dental Materials Science
• Oral Histopathology
• Biocompatibility Testing

Background:

• Direct-bonding systems are widely used by orthodontists for bracket adhesion to enamel.
• Accidental contact between bonding agents and oral soft tissues (gingiva, mucosa) is common during application.
• The biocompatibility of these frequently used orthodontic materials remains inadequately studied.

Purpose of the Study:

• To evaluate the gingival tissue response to the primer component of the Mono-Lok direct-bonding system.
• To compare the effects of Mono-Lok primer with a control primer and saline solution on gingival tissues.

Main Methods:

• Primer components of Mono-Lok and a Control agent were applied to the gingival tissues of Macaca mulatta monkeys.
• Saline solution served as a negative control.
• Clinical and histological examinations of gingival biopsies were performed over a 21-day period.

Main Results:

• Gingival tissues exposed to Mono-Lok primer showed pronounced inflammation, including redness, swelling, and bleeding.
• Histological analysis revealed significant inflammatory cellular infiltration, notably eosinophils, in response to Mono-Lok primer.
• Gingiva exposed to the Control primer or saline solution exhibited normal histological architecture.

Conclusions:

• The primer component of Mono-Lok demonstrates significant gingival irritancy and inflammatory potential.
• The Control primer and saline solution were found to be non-irritating to gingival tissues.
• Further investigation into the biocompatibility of orthodontic bonding materials is warranted.