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CDE0211

30 I I industry report _ compobonds cosmeticdentistry 2_2011 Fig. 18b_Vertise Flow is dispensed onto the entire occlusal surface. Figs. 19a & b_A brush is used to press Vertise Flow onto the enamel surface for 15ā€“20 seconds (a) and to obtain a layer of < 0.5 mm thickness (b). Fig. 20_The set Vertise Flow after appropriate light curing. Fig. 21_Articulation paper is used to verify occlusal contacts. Notice extraneous flash material at the distal aspect of the permanent molar. Fig. 22_For mandibular teeth, all occlusal contacts are removed, except those on the buccal supporting cusps. Notice that the distal flash material has been removed. thatsecondarycariouslesionswillensueinthepres- enceofanopenordiscolouredcavo-surfacemargin. The current thinking is that patient risk factors, such as oral hygiene, dietary considerations and attitude towardsdentaltreatment,arepivotalindetermining whether decay will occur.21 As previously stated, marginal breakdown is at- tributed to polymerisation shrinkage of a composite duringitssettingstage,rangingfrom2to5%byvol- ume,22 causing stresses that lead to bonding failure and gap formation (Figs. 3 & 4). Polymerisation stresses can be mitigated by the clinical technique, MOE of the material and cavity configuration or the ā€œCā€ factor. In an effort to circumvent polymerisation shrinkage, manufacturers have altered the chemical compositionofcompositestohavefavourableprop- erties. These include varying the size, shape and volume of the inorganic filler particles, as well as improving adhesion of the fillers to the organic resin matrix. Other factors that reduce stresses are the method of setting reaction, for example using pulse curing,23 and incremental build-up of the composite filling during placement.24 Another technique (dis- cussed below) is using flowable composites with a lower MOE as the initial base-lining layer to absorb polymerisation stresses and counteract forces at the restoration-dentine interface.25 _Flowable composites Flowables, introduced nearly two decades ago, havebecomeubiquitousformanyapplications.They exhibit greater fluidity and elasticity, offering better adaptation to internal cavity walls and are very user friendly. In addition, the radiopacity of these resins allows effortless detection of secondary caries, and revealsmarginalintegrityoropenmargins.Arestora- tive material should possess radiopacity that is slightly greater than enamel to distinguish decay,26 andgreaterthantheISOminimumstandardorequal to or greater than an equivalent thickness of alu- minium. This is especially significant if flowables are used as intra-coronal initial lining layers below subsequent increments of universal composite. The ISO standard for minimum FS of outer occlusal restorativematerialsis80MPa,whichisdisplayedby most of the current flowables on the market. The FS dependsonthespecificproprietarymaterial,ranging from 70 to approximately 100 MPa, deteriorating overtime,andisapproximately80%comparedwith non-flowable analogues. Although micro-leakage is a multifactorial phe- nomenon, MOE of the material is a crucial factor that determines its magnitude. Similar to FS, MOE is variable, depending on the product, ranging from 3 to over 11 GPa, and also decreasing over time. The viscoelastic properties of a flowable determine its flowabilityandclinicalhandling.Theflowcharacter- isticsofflowablecompositescanbedividedintolow, medium and high flow.27 Each variety is suitable for differentclinicaltasks.Forexample,ahighlyflowable material is desirable as a liner or fissure sealant, to adhere to cavity walls or fissures crevices intricately, while a less flowable variety is preferable for small cavitiesorrepairs,whereexcessiveslumpingisanui- sance. Currently, most of the flowable composites possesslittlebacterialinhibitorypotential,especially against S. mutans, the main infective agent of den- tal caries. Whilst a few flowables on the market claim anti-bacterial activity, the effect is usually Fig. 19a Fig. 19bFig. 18b Fig. 21 Fig. 22Fig. 20