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properties, is also an effective inhibitor of MMP-2, -8 and-9 even at very low concentrations.4 Using contralateral Adhesive dentistry has come a long way since the devel- pairs of bonded and subsequently exfoliated primary mo- opment of adhesive monomers by Dr. Oskar Hagger, lars in children, Dr. Josimeri Hebling (Faculty of Dentistry, which were first used by Kramer and McLean,7 and acid UNESP, Araraquara, Brazil) has recently observed that dis- etching of dental hard tissues by Dr. Michael Buono- appearance of the collagen fibrils within the hybrid layer core.1,2 The availability of dentin adhesives has profound- in the control primary molars occurred as early as six ly improved the quality of conservative work performed in months in vivo. Conversely, collagen fibrils within the pediatric and geriatric dentistry, prosthodontics, and late- hybrid layer remained intact in the experimental primary ly, in endodontics. Today, we salute the commercialization molars that were pretreated with chlorhexidine prior to of different classes of etch-and-rinse and self-etch adhe- the placement of a simplified etch-and-rinse adhesive.
sives. Simplified versions of these adhesives have made Thus, there appears to be a glimmer of hope. Can chlor- bonding simpler, faster, and more user friendly. They rep- hexidine or other synthetic, nontoxic MMP-inhibitors be the resent remarkable scientific and entrepreneurial achieve- ultimate saviors of contemporary dentin bonding by im- ments by research scientists, clinicians, and manufactur- proving the longevity of resin-dentin bonds? This practical ers. In all the words spoken and written on dentin adhe- question awaits clinical confirmation from research cen- sives, one theme constantly recurs: how long do these ters all over the world. We know that all clinicians are totally man-made bonds last? Can resin-dentin bonds remain in- committed to the improvement of the quality of service tact in the hostile environment of the oral cavity? delivered to their patients, and to the advancement of Indeed, recent reports by our research colleagues science in adhesive dentistry. We need the help of all our around the world have shown that resin-dentin bonds are colleagues in this exciting arena of dentin bonding re- not as durable as we have perceived them to be, particu- search. As we approach the Golden Jubilee of enamel etch- larly when these bonds are made in the absence of ing in year 2005, let us work together and continue the surrounding enamel.3 The hybrid layer, for example, was legacy of the late Dr. Michael Buonocore, by not simply pro- found to be susceptible to hydrolytic degradation, with the ducing faster and more user-friendly adhesives, but toward disappearance of the collagen fibrillar component over improving the quality of resin bonds created in dentin.
time in laboratory studies.5,6 Such a phenomenon has re-cently been confirmed clinically, using bonded human pri-mary teeth in function that were harvested upon exfolia- tion and examined ultrastructurally for the integrity of thecollagen fibrils in the hybrid layer. In this study, what is in- 1. Buonocore MG. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces. J Dent Res 1955;34:849-853.
triguing is that dentin hybrid layers can disappear beneath 2. Buonocore MG, Wileman W, Brudevold F. A report on a resin composition bonded restorations with cavosurface margins that resid- capable of bonding to human dentin surfaces. J Dent Res 1956;35: ed completely in enamel, in the absence of the influence 3. DeMunck J, Van Meerbeek B, Yoshida Y, Inoue S, Vargas M, Suzuki K, of salivary and bacterial enzymes. We now understand Lambreschts P, Vanherle G. Four-year water degradation of total-etch that matrix metalloproteinases (MMPs) that are fossilized adhesives bonded to dentin. J Dent Res 2003;82:136-140.
within the mineralized dentin can be released and activat- 4. Gendron R, Grenier D, Sorsa T, Maygrand D. Inhibition of the activities of matrix metalloproteinases 2, 8, and 9 by chlorhexidine. Clin Diagn Lab ed during bonding procedures.8 These endogenous col- lagenolytic enzymes represent the “Darth Vaders” of den- 5. Hashimoto M, Tay FR, Ohno H, Sano H, Kaga M, Yiu C et al. SEM and TEM tin bonding. They reside on the very collagen fibrils that analysis of water degradation of human dentinal collagen. J Biomed MaterRes Part B (Appl Biomater) 2003a;66B:289-298.
are used for resin/composite retention. Their slow degra- 6. Hashimoto M, Ohno H, Sano H, Oguchi H. Degradation patterns of different dative enzyme activities are beyond the control of even adhesives and bonding procedures. J Biomed Mater Res Part B (ApplBiomater) 2003b;66B:324-330.
the most astute and meticulous clinician. Reflecting on 7. Kramer IRH, McLean JW. Alterations in the staining reactions of dentine this latest insight into the degradation mechanism of res- resulting from a constituent of a new self-polymerizing resin. Br Dent J in-dentin bonds, one is compelled to ask, is there a future 8. Pashley DH, Tay FR, Hashimoto M, Breschi L, Carvalho RM, Ito S. Degra- dation of dentin collagen by host-derived enzymes during aging. J Dent Res Investigations on the use of synthetic inhibitors of MMPs have been active in other branches of medicalscience, in particular, research on neoplastic diseases. Inperiodontal tissue destruction, host-derived MMPs havelong been recognized as tissue-destructive enzymes, andadjunctive MMP-inhibitor medication (Periostat) hasbeen shown to be effective in prevention of disease pro-gression. Chlorhexidine, better known for its disinfecting

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