CDE0211

34 I I industry report _ compobonds designed to minimise removal of tooth substrate (Fig.25).Currentresearchshowsthatitisunnecessary toremovealldecayeddentine.Instead,thecavitymar- ginsareclearlydefinedforcreatingahermeticsealfor guarding against the negative effects of the dental biofilm, which perpetually colonises the tooth sur- face.30 As previously mentioned, in order to improve bond strength to aprismatic enamel, the margins can beeitheretchedorbevelled(Fig.26).Theinitiallayerof Vertise Flow should be less than 0.5 mm in thickness and pressed into the recesses of the cavity floor and walls(Figs.27a&b).TheinitiallayerofVertiseFlowwas first light cured (Fig. 28) before completing the cavity withadditionallayers.Finally,therestorationwaspol- ishedwithOpti1StepPolisherandanOptiShinebrush (KerrHawe SA) to yield a high lustre gloss (Fig. 29). ClassVandsmallbuccalcavities Class V cavities have variable presentations. The exposed dentine in Class V cavities can be the result of enamel loss due to erosion, abrasion abfraction or infectious caries. The dentine reaction is highly er- ratic,oftenleadingtoformationofhyper-mineralised sclerotic dentine that is resistant and less receptive to dentine adhesion.31 Therefore, in the presence of sclerotic dentine, all DBAs are less efficacious and presentachallengefordentinebonding.Forthisrea- son,VertiseFlowisunsuitableforClassVlesionswith blatant dentine hyper-mineralised sclerotic dentine. If sclerotic dentine is absent, adhesion with DBAs is superior (28 MPa) compared with compomers (15 MPa) or a glass-ionomer (2.5 MPa).32 For small buccalcavitieswithinenamel,VertiseFlowistheideal material of choice, as shown in the following case. Preoperative articulation paper marks verified that the buccal lesion was free of occlusal, stress- bearing contacts (Fig. 30). After isolation with a rub- ber dam, the tooth was cleaned with a slurry of pumice (Fig. 31) and a cavity was prepared with bev- elled enamel margins (Fig. 32). The final result shows restoration of the cavity with A3 Vertise Flow after polishing with Opti1Step Polisher (Fig. 33). Stress-relievinglinings The rationale for using different composites for various increments of a restoration is that the mate- rials should possess similar properties to the natural dentine and enamel they are replacing. Dentine has a lower MOE and is therefore better able to absorb stresses than enamel. For this reason, in circum- stances in which the cavity extends into dentine, the initiallayerofcompositeshouldhaveshock-absorb- ing capabilities that are similar to dentine. The polymerisation contraction stresses of a resin-basedcompositearedirectlyrelatedtoitsfiller volume,whichalsoaffectsitsmechanicalproperties, such as wear resistance and MOE. High filler content results in less contraction, which in turn influences themarginalintegrityoftherestoration.33 Flowables have approximately 25 % less filler than their non- flowable counterparts and therefore undergo in- creased volumetric shrinkage. However, since flow- ableshaveabout50%lessMOEthannon-flowables, they can absorb more stresses and, in theory, main- tain superior marginal integrity.34 TheMOEofflowablesrangesfromaslowas1.4GPa (low filler volume) to as high as 12.5 GPa (high filler Figs. 40a & b_A brush is used to spread the Vertise Flow on the cavity walls (a) and floor, ensuing that it is evenly spread with a thickness less than 0.5 mm (b). Fig. 41_The initial Vertise Flow lining is light cured. Fig. 42_A regular composite, Herculite XRV Ultra, is used in increments for replacing dentine and building up individual buccal and lingual cusps. Fig. 43_An endodontic file, loaded with brown Kolor + Plus stain, is dragged through the unset composite resin to create fissure patterns in the second molar restoration. Fig. 44_An endodontic file, loaded with brown Kolor + Plus stain, is dragged through the unset composite resin to create fissure patterns in the third molar restoration. cosmeticdentistry 2_2011 Fig. 40b Fig. 41Fig. 40a Fig. 43 Fig. 44Fig. 42