cosmetic dentistry_ beauty & science

06 I I CE article _ bioactive materials cosmeticdentistry 1_2013 _Resin bonding of the human dentition has become a “standard” in the United States and Canada. There are more than 80 different bonding systems on the market today. We have seen them evolvethroughmultiplegenerationsinanattempt to “simplify” the bonding process. Yet, as these agents have simplified, many in our profession have seen many challenges arise. A significant number of reports in the litera- ture have been showing that the “immediate bondingeffectivenessofcontemporaryadhesives are quite favorable, regardless of the approach used (however) in the long term, the bonding effectiveness of some adhesives drops dra- matically.”1 The hydrophillicity that both etch- and-rinse and self-etch bonding agents offer initially in the dentin-bonding process becomes a significant disadvantage in terms of longterm durability.2 It is this hydrophillicity of simplified adhesive systems combined with other operator-induced challenges that contribute to these failures. Tay, Carvalho, Pashley, et al. have reported repeatedly intheliteratureofthisproblem.3,4 Theycontinueto report that these bonding agents do not coagulate the plasma proteins in the dentinal fluid enough to reduce this permeability. The fluid droplets contribute to the incompatibility of these simpli- fied adhesives and dual-/auto-cured composites in direct restorations and the use of resin cements for luting of indirect restorations. The term “water-tree” formation has been coined to describe this process, which originated from the tree-like deterioration patterns that were found within polyethylene in- sulation of underground electrical cables. It is now being applied to the water blisters formed by the transfer of dentinal fluid across the dentin- bonding interface. These “water blis- ters...act as stress raisers and form initial flaws that cause subsequent catastrophic failure along the adhesive composite interfaces.” The previously mentioned plasma proteins are released by the dentin when subjected to acids and cause hydrolytic and enzymatic breakdown of the dentin and resin bonding agent interface.5 These enzymes are called matrix metallopro- teinases (MMPs). Currently, there are only three methods of reducing these MMPs: 2 per cent chlorhexidine solutions that are used prior to application of bonding agents; etchants containing benzalko- niumchloride,otherwiseknownasBAC(i.e.,Bisco’s Uni-etch products); and polyvinylphosphonic- acid-producing products (glass ionomer and resin- modified glass ionomers). Due to the short efficacy of these chlorhexidine solutionsbeingusedbeforebonding,thismethod- ology has come into question as of late.6 Etchants with BAC have been shown to be valuable in the reduction of MMPs and should be considered in all bonding processes.7 However, the most intriguing methodology of reducing MMPs and remineraliz- ingtoothstructureiswiththeuseofglassionomer cements (GIC) and resin-modified glass ionomers (RMGIC). Fig. 1 Fig. 2 Fig. 3 Bioactive materials support proactive dental care Author_Dr John C. Comisi, USA By reading this article and then taking a short online quiz,you can gainADA CERP CE credits. To take the CE quiz,visit www.dtstudyclub.com.The quiz is free for subscribers,who will be sent an access code.Please writesupport@dtstudyclub.com if you don’t receive it.Non sub- scribers may take the quiz for a $20 fee. _ce credit cosmeticdentistry (Photos/Provided by Dr John C. Comisi unless noted otherwise)