Substantivity of chlorhexidine to human dentin

Abstract

Objectives-To better comprehend the role of CHX in the preservation of resin-dentin bonds, this study investigated the substantivity of CHX to human dentin.Material and Methods-Dentin disks (n= 45) were obtained from the mid-coronal portion of human third molars. One-third of dentin disks were kept mineralized (MD), while the other twothirds had one of the surfaces partially demineralized with 37% phosphoric acid for 15 s (PDD) or they were totally demineralized with 10% phosphoric acid (TDD). Disks of hydroxyapatite (HA) were also prepared. Specimens were treated with: 1) 10 μL of distilled water (controls), 2) 10 μL of 0.2% chlorhexidine diacetate (0.2% CHX) or 3) 10 μL of 2% chlorhexidine diacetate (2% CHX). Then, they were incubated in 1 mL of PBS (pH 7.4, 37 °C). Substantivity was evaluated as a function of the CHX-applied dose after: 0.5h, 1h, 3h, 6h, 24h, 168h (1wk), 672h (4wks) and 1344h (8wks) of incubation. CHX concentration in eluates was spectrophotometrically analyzed at 260 nm.Results-Significant amounts of CHX remained retained in dentin substrates (MD, PPD or TDD), independent on the CHX-applied dose or time of incubation (p<0.05). High amounts of retained CHX onto HA were observed only for specimens treated with the highest concentration of CHX (2%) (p<0.05). Conclusion-The outstanding substantivity of CHX to dentin and its reported effect on the inhibition of dentinal proteases may explain why CHX can prolong the durability of resin-dentin bonds.

Mechanisms of degradation of the hybrid layer in adhesive dentistry and therapeutic agents to improve bond durability—A literature review

“…This is supported by the finding that treating dentin powder with Clearfil SE Bond primer for 2 min instead of 20 s not only increased the collagenolytic activity, but also caused the loss of inhibition by 0.5% and 1.0% CHX, with only 2.0% CHX showing significant inhibition [87]. Also the recent reports of chlorhexidine binding by dentin collagen [86,89] suggest that collagen may compete with MMPs for CHX binding, requiring the use of relatively high CHX concentrations.…”

MMP-2 assay within the hybrid layer created by a two-step etch-and-rinse adhesive: Biochemical and immunohistochemical analysis

“…Due to its substantivity and inhibitory capacity on MMPs, CHX could have altered the protein conformation by hiding some enzyme's epitopes, thereby reducing the probability of MMP-2 to be recognized in the immunohistochemical assay. 35,36 As previous studies have clearly demonstrated the improved preservation of the HL integrity and strength, 19,20 this masking of the epitope is most likely also related to the long-term or inhibition of MMP-2 functional activity in the adhesive-dentine interface.…”

A 2-year in vitro evaluation of a chlorhexidine-containing acid on the durability of resin–dentin interfaces

“…The good results using chlorhexidine in the phosphoric acid for only 15 s also supports the results of a recent study that showed an outstanding substantivity of chlorhexidine on dentin. 28 When ionized in solvent like water, CHX is characterized by being a strong base with cationic properties. The cationic part of CHX molecules bind to the negatively charged surface/site of target-substrates.…”

“…CHX was shown to remain binded in demineralized and mineralized dentin substrates 29 regardless the CHX concentration or incubation time. 28 This is probably due to ability of CHX to bind to phosphate groups or to negative carboxyl groups in mineralized dentin crystallites or collagen matrix, respectively. 27 This prevents the proteases to bind to collagen fibrils, accounting for the preservation of the hybrid layer after longterm water exposure.…”