Twenty-month Performance of a Universal Bonding System on Simulated-challenged Dentin Substrates Pretreated with Chlorhexidine
Since the use of dentin antiproteolytic agents with universal adhesives (UAs) can potentially degrade the bonding interface, this study evaluated bond strengths with and without chlorhexidine (CHX) on variously altered dentin surfaces for up to 20 months. Human molar specimens (n=20) were categorized by substrates as S=sound, E=eroded, and C=carious, and by pretreatment as W=water or CHX. These specimens were subjected to micro-tensile bond strength (μTBS) testing at 24 hours, 6 months, and 20 months, after 30 seconds of pretreatment with CHX or W, followed by self-etching and bonding (Adper Single Bond Universal, 3M ESPE). Modes of failure were assessed using optical microscopy (40×) and scanning electron microscopy (SEM), and the results were analyzed by 3-way ANOVA and Tukey’s statistical tests (α=0.05). Substrate (p<0.001), pre-treatment (p=0.0413), and time (p<0.0001) were statistically significant. The sound-dentin group in initial time (W=39.27/CHX=40.55) yielded the higher μTBS values (MPa) in comparison with altered substrates pre-treated with CHX (E-CHX=19.84; C-CHX=18.24) after 20 months, which showed the lowest values. Under SEM analysis, heterogeneous patterns appeared in the hybrid layer of the CHX-treated group, particularly in the altered substrates. Bond strength to dentin decreased over a period of 20 months using UA with 10-methacryloyloxydecyl-dihydrogen phosphate (MDP) in self-etching mode. Substrates altered by erosion or caries have impaired adhesion and associated clinical use of UA with MDP and CHX should be avoided.SUMMARY
Objectives
Methods
Results
Conclusions
Experimental design of study with division of factors and subdivision of levels. Abbreviations: S, sound; E, eroded; C, carious; W, water; CHX, chlorhexidine; h, hours; m, months.
Failure mode distribution (%) regarding all substrates and pretreatment at the initial, 6-month, and 20-month time point. Abbreviations: S-W-I, sound-water-initial; S-W-6m, Sound-Water-6 months; S-W-20m, sound-water-20 months; S-CHX-I, sound-chlorhexidine-Initial; S-CHX-6m, sound-chlorhexidine-6 months; S-CHX-20m, sound-chlorhexidine-20 months; E-W-I, eroded-water-initial; E-W-6m, eroded-water-6 months; E-W-20m, eroded-water-20 months; Eroded-CHX-I, eroded-chlorhexidine-Initial; E-CHX-6m, eroded-chlorhexidine-6 months; E-CHX-20m, eroded-dhlorhexidine-20 months; C-W-I, carious-water-initial; C-W-6m, carious-water-6 months; C-W-20m, carious-water-20 months; C-CHX-I, carious-chlorhexidine-initial; C-CHX-6m, carious-chlorhexidine-6 months; C-CHX-20m, carious-chlorhexidine-20 months.
Representative SEM images (magnification, 75× and 1500×) of failure mode (adhesive, mixed, dentin cohesive, and resin cohesive). A and a illustrate adhesive failure, presenting the more uniform surface of the universal adhesive system. B and b illustrate mixed failure showing the adhesive and dentin substrate. C and c illustrate dentin-cohesive failure with layers of dentin substrate representing parts of a rupture. D and d illustrate a resin cohesive failure through the resin surface.
Representative SEM images (magnification, 1500×) of sound dentin at initial time (a – W; b – CHX), 6 months (c – W; d – CHX), and 20 months (e – W; f – CHX); eroded dentin at initial time (g – W; h – CHX), 6 months (i – W; j – CHX), and 20 months (k – W; l – CHX); and carious dentin at initial time (m – W; n – CHX), 6 months (o – W; p – CHX), and 20 months (q – W; r – CHX). A standard pattern commonly observed for self-etching adhesive systems is verified in sound groups, as homogeneous hybrid layer and thin resinous tags are seen. Altered substrate do not present any specific particular pattern. The heterogeneity of the eroded and carious groups is exacerbated with CHX pretreatment (Fig. h, j, l, n, p, r). Regarding time, especially after 20 months (Fig. e, f, k, l, q, r), a discontinuous adhesive layer is considered, regardless of pretreatment. Abbreviations: R, composite resin; HL, hybrid layer; D, dentin substrate.
Direct comparison between pretreatments (W and CHX) in different substrates (S, E, C) after follow-up (24 hours, 6 and 20 months) showing the worst performance of CHX groups, especially in the final time.
Contributor Notes