CDE0211

Other classes of materials include siloranes and ormocers. Whilst the silorane-based composites have the lowest polymerisation shrinkage of any resin, they display mixed mechanical properties: flexuralstrength(FS)andmodulusofelasticity(MOE) are higher, but their compressive strength and microhardness are lower compared with methacry- late-based composites.5 Ormocer technology is anotheradditiontothedentalrestorativearmamen- tarium, having excellent wear resistance, but poor polishability.Theevolutionofcompobonds,launched in 2009, is based on the premise of the promising clinical outcomes of dentine bonding agent (DBAs) and resin-based composites. _Dentine bonding agents The acid-etch technique, introduced by Buono- core in 1955, was seminal and opened the doors to the possibilities of achieving a bond to natural tooth substrates with artificial acrylic-based restoratives.6 Whilst bonding to enamel has changed little since its inception more than half a century ago, bonding to dentine has proved far more elusive, under- going enormous changes. A major advancement for achieving a sustainable bond to dentine was the introduction of the total-etch (TE) technique7 in the late seventies (Fig. 1). The first self-etching (SE) primer, combining an etchantandprimerinasinglestep,wasintroducedin theearlynineties.8 TheSEprimersnotonlysimplified bonding to dentine, but also eliminated the clinical errors associated with this exacting procedure. The result was a more predicable dentine bond and longevity of a composite resin filling. The next decade witnessed many formulations, including etchant+primer followed by adhesive, etchant fol- lowed by primer+adhesive, and more recently in the mid-nineties, combining all three constituents, etchant+primer+adhesive, in a single product and a one-step procedure (Fig. 2). Contemporary DBAs can be divided into two varieties: TE or SE. To complicate matters further, the TE bonding systems are available as either three- or two-step systems, and SE as either two- or one- step systems, which are available as three-, two- or one-bottle components. Therefore, to resolve some of these dilemmas in choosing a DBA, simplifying clinicaltechniquesandminimisingerrors,thecurrent trend is moving away from multi-component and multi-step bonding systems.9 Also, encouragingly, both TE and SE varieties have bond strengths to dentine that are comparable to that of enamel (approximately 22 MPa).10 The salient difference between the TE and SE agents is that an initial etching stage is required with the former, but unnecessary with the latter. ForTE,bothenamelanddentinearesimultaneously etched, usually with phosphoric acid, and followed by application of the primer and adhesive, or both components together in a single liquid. With SE agents, precursory etching is superfluous, since this is concurrently performed with the primer and adhesive. Although SE agents expedite the bonding proce- dure, the major difference between TE and SE bond- ing agents concerns the smear layer. With TE agents, the etching and drying of dentine is susceptible to Fig. 2_SE DBAs combine the etchant, primer and adhesive into a in a single product and a one-step clinical procedure. Fig. 3_One of the limitations of composite fillings is polymerisation shrinkage, leading to marginal breakdown. Fig. 4_Polymerisation shrinkage of resin-based composites results in marginal staining. Fig. 5_Vertise Flow is a self-adhering flowable composite, combining an SE bonding agent with a resin-based composite. Fig. 6_The bonding agent in Vertise Flow is based on the technological advances of OptiBond, the first filled dentine-bonding agent introduced in 1992, which has now evolved into an SE system. Fig. 7_When using Vertise Flow, it is advisable to either bevel or etch aprismatic enamel of the cavity margins. I 27 industry report _ compobonds I cosmeticdentistry 2_2011 Fig. 3 Fig. 4Fig. 2 Fig. 6 Fig. 7Fig. 5