The Production of a Root Surface Smear Layer by Instrumentation and its Removal by Citric Acid

Abstract

The purpose of this study was to characterize, using the scanning electron microscope, the nature of root surfaces denuded by (1) root planing alone or (2) root planing plus citric acid treatment. Six teeth were extracted from three squirrel monkeys, and the coronal half of the root surface was planed to remove attached periodontal ligament fibers and cementum. Citric acid, pH 1, was topically applied to the denuded surfaces of 3 teeth. The surface of only root-planed specimens had an irregular surface which corresponded to a smear layer. Root surfaces that had received acid treatment after root planing exhibited funnel-shaped orifices of dentinal tubules, and intertubular zones with a fibrillar, mat-like morphology. The implications of the different root-surface characteristics are discussed.

The smear layer created by scaling and root planing is physiologically eliminated in a biphasic process

“…A significant difference was found in the presence of the smear layer between ultrasonic scaling and laser treatments. 22 It is important to determine how long the smear layer remains on the root surface after scaling and root planing as it may interfere with the biological events involved in the regeneration of periodontal tissues, 1,12,23 particularly in the early phases of healing. The smear layer, which is interposed between the root and the tissues, can prevent blood clot adhesion and cell attachment to the root surface.…”

“…Chemical agents, such as citric acid, tetracycline, and ethylenediaminetetraacetic acid, modify the root surface by removing the smear layer and endotoxins, opening dentinal tubules, and exposing the collagenous matrix. 1,11,12,18 A significantly higher amount of cell attachment occurs on demineralized dentin surfaces in vitro compared to nonetched dentin surfaces. 25,26 The cellular responses to demineralized and nondemineralized dentin were studied in a subcutaneous transfixation model in rodents, and an improved response was reported in the demineralized samples, which present a surface that is similar to smear layerfree dentin compared to the nondemineralized dentin samples in which the surface is similar to smear layercovered dentin.…”

“…Microscopic analyses have shown that the smear layer contains residual calculus, cementum, bacteria, and bacterial-derived products. 11,12 For this reason, the smear layer can act as a physical barrier between periodontal tissues/blood clots and the root surface, and it inhibits or hinders the formation of new insertions and possibly harbors bacterial growth. 12,13,14 Because the effective removal of the smear layer could increase the potential for periodontal regeneration, many studies have assessed different chemical conditioning procedures for thorough elimination of the smear layer and exposure of the collagenous matrix.…”

“…11,12 For this reason, the smear layer can act as a physical barrier between periodontal tissues/blood clots and the root surface, and it inhibits or hinders the formation of new insertions and possibly harbors bacterial growth. 12,13,14 Because the effective removal of the smear layer could increase the potential for periodontal regeneration, many studies have assessed different chemical conditioning procedures for thorough elimination of the smear layer and exposure of the collagenous matrix. 15,16,17,18 However, the clinical effectiveness of scaling and root planing procedures 19 indicates that the smear layer does not prevent periodontal healing.…”

Gingival recession: part 2. Surgical management using pedicle grafts

“…The aim of this treatment is to remove the smear layer on the root surface to allow connective tissue attachment to the root surface. 6,7 Others have suggested the use of tetracycline hydrochloride to help promote the healing response post surgery however, clinical studies have failed to show any improvements in outcome when using such agents. 8…”