Should acid etching be performed prior to nonvital bleaching?

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Nonvital bleaching is a common dental procedure.
• Composite resins are widely used for dental restorations.
• Bleaching agents may affect the integrity of the tooth-restoration interface.

Purpose of the Study:

• To measure the microtensile bond strength of nanofilled composite resin to human dentin.
• To evaluate the effect of phosphoric acid etching duration prior to nonvital bleaching on bond strength.
• To analyze fracture modes using scanning electron microscopy.

Main Methods:

• Twenty human maxillary premolars were prepared with Class I defects.
• Samples were divided into four groups: control, bleaching only, 15-second etching + bleaching, and 30-second etching + bleaching.
• Microtensile bond strength testing and scanning electron microscopy (SEM) were performed.

Main Results:

• No significant difference in bond strength was found between the control, bleaching only, and 15-second etching groups.
• A statistically significant reduction in mean bond strength was observed in the group with 30-second etching prior to bleaching.
• SEM analysis provided insights into fracture patterns at the interface.

Conclusions:

• Excessive phosphoric acid etching (30 seconds) before nonvital bleaching compromises the bond strength of nanofilled composite resin to dentin.
• Shorter etching times (15 seconds) appear compatible with nonvital bleaching procedures.
• Clinicians should consider the duration of acid etching when planning restorations after nonvital bleaching.