In Vitro Effects of Citric Acid Application Techniques on Dentin Surfaces

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Abstract
The present study evaluated the in vitro effects of different application techniques of citric acid on dentin root surfaces. Ten freshly extracted, periodontally involved teeth were obtained and 4 dentin slabs, approximately 4 × 6 × 2 mm, were obtained from the roots of each tooth, for a total of 40 slabs. These slabs were identified by tooth and preserved in 1:1 anhydrous glycerol/absolute alcohol solution. Citric acid pH 1 was applied to 32 of the slabs for 5 minutes with one of 4 different techniques: 1) immersion; 2) placed with a saturated cotton pellet with no rubbing; 3) placed and burnished with a saturated cotton pellet; or 4) applied with a camel hair brush. The remaining 8 dentin slabs were used as negative control specimens, root-planed and non-acid treated. Following the various treatments, the slabs were fixed, dehydrated, critical point dried, and coated for scanning electron microscopic (SEM) evaluation. Scanning photomicrographs were obtained at 2,000, 6,000, and 40,000 magnifications. The surface characteristics of the treated dentin slabs were evaluated descriptively regarding the degree of fiber exposure; the number of exposed tubules and the surface area occupied by tubule orifices were also measured. Friedman's 2-way analysis for block designs was employed. Results demonstrated that root-planed, non-acid treated specimens had an amorphous, irregular surface which corresponded to a smear layer. Corresponding views of instrumented surfaces which had been treated with citric acid by immersion, placed with a cotton pellet, or applied with a camel hair brush exhibited funnel-shaped orifices of dentinal tubules and intertubular zones with exposed connective tissue fibers, mat-like morphology. In contrast, slabs treated with the burnishing technique showed wide surface variations. Surface tufting with widened tubular opening was observed on 2 of the 8 treated slabs. Surface smearing with complete obturation of tubules was present in the remaining 6 slabs. According to the results of the present study, if maximum exposure of intertubular fibrils and dentinal openings is beneficial in periodontal regenerative procedure, it may be undesirable to apply citric acid using excessive pressure. J Periodontol 1992; 63:883– 889.