Comparative Evaluation of Fumaric Acid and Phosphoric Acid in Smear Layer Removal from Coronal Dentin: An Invitro Analysis

Abstract

Background:
Effective smear layer removal is critical for enhancing dentin adhesion and improving the longevity of dental restorations. While phosphoric acid is widely used for etching, its aggressive demineralization may compromise dentin integrity over time. Fumaric acid, a biocompatible organic acid, has shown potential as an alternative etchant due to its smear layer removal properties and milder effect on dentin.

Aim:
To compare the efficacy of 37% phosphoric acid and 0.7% fumaric acid in removing the smear layer from coronal dentin using scanning electron microscopy (SEM).

Methodology:
Twenty-four human mandibular molars extracted for periodontal reasons were prepared by exposing mid-coronal dentin. The samples were randomly divided into two groups (n=12): one treated with 37% phosphoric acid for 10 seconds, and the other with 0.7% fumaric acid for 30 seconds. Following etching, samples were rinsed, kept moist, dehydrated, and subjected to SEM analysis to assess smear layer removal based on percentage of open dentinal tubules. Data were analyzed using an unpaired t-test.

Results:
The mean percentage of open dentinal tubules was 87.92% for the phosphoric acid group and 87.47% for the fumaric acid group. The difference between the two groups was not statistically significant (p = 0.367).

Conclusion:
Fumaric acid demonstrated smear layer removal efficacy comparable to that of phosphoric acid, suggesting it may serve as a viable alternative etchant in adhesive dentistry. Given its biocompatibility and conservative action on dentin, further longitudinal studies are recommended to explore its clinical application and long-term effects.