A comparative study of three etching solutions: effects on enamel surface and adhesive-enamel interface

Area of Science:

• Dental Materials Science
• Surface Chemistry
• Biomaterials Engineering

Background:

• Chemical treatment of enamel surfaces is crucial for improving dental material adhesion.
• Commonly used etchants include 50% phosphoric acid (H3PO4), zinc oxide-attenuated H3PO4, and citric acid.
• Understanding etching patterns is key to optimizing bonding protocols.

Purpose of the Study:

• To evaluate the effects of three common dental etching solutions on normal and polished enamel surfaces.
• To analyze the etching patterns and surface profiles using scanning electron microscopy and surface profile recordings.
• To compare the etching efficacy of 50% H3PO4, 50% H3PO4 with 7% zinc oxide, and 50% citric acid.

Main Methods:

• Scanning electron microscopy (SEM) was employed to visualize surface morphology.
• Surface profile recordings were used for quantitative assessment of etching depth.
• Enamel surfaces (normal and polished) and their interfaces were examined after treatment with different acids.

Main Results:

• Variable etching patterns were observed for each acid, complicating direct comparisons.
• Etching effectiveness depended on enamel prism orientation, especially on polished surfaces.
• 50% citric acid exhibited the mildest etching action.
• 50% H3PO4 and 50% H3PO4 attenuated with 7% zinc oxide produced comparable and stronger etching responses.

Conclusions:

• The choice of etchant significantly influences enamel surface topography and potential for bonding.
• Citric acid offers a milder alternative for enamel conditioning compared to phosphoric acid-based solutions.
• Phosphoric acid and its zinc oxide-modified variant demonstrate similar, more aggressive etching capabilities.