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ePaper created 2016-01-20, 13:53:08 | version 1.38.0
I 25 case report _ composite restoration I roots1_2015 means that the deeper layers of composite resin are less cured with reduced mechanical properties, and that bulk filling shows significantly less hardness.54 Othershavealsoshownthatbulkplacementandin- creased cavity depth result in a significant decrease intheeffectivenessofpolymerization,regardlessof the exposure time.55 The ADA Professional Product reviewonRestorativeMaterialsevaluatedthedepth ofcureof38restorativeswithrangesof1.2to5mm. with a core material CompCoreAF syringMix Flow (W) being the lowest depth of cure at 1.2mm. In- cluded in the study were measurements of maxi- mum polymerisation shrinkage stress showing that LuxaCore Dual Smartmix W was the highest in stressMPaofthecorematerialstested,withClearfil Photo Core (T) showing the highest development of shrinkage stress rate.56 Dual cure composite materials show the best physical properties and best polymerisation with sufficient light exposure, even though they are claimedtopolymeriseintheabsenceoflight57-61 and ‘thereisnoevidenceforasubstantialchemicallyin- ducedpolymerisationofdualcureresinsthatoccurs after light exposure is completed.’62 This reality is especially critical for dual-cure self-adhesive resin cements Maxcem and RelyX Unicem, which show a better degree of conversion when they are light ac- tivated,withalackoflightactivationdecreasingthe monomerconversionby25to40percent63 andeven in their dual cure mode, the decree of cure at best among the self-etch adhesives is only 41.52 per cent.64-66 Thus, the placement of a bulk filled dual curecompositeintotheendodonticaccessopening, followed by the placement of multiple fibre post segments that carry sufficient light energy to the depthoftheocclusalflooroftheaccesspreparation, will increase the polymerisation conversion, result- ing in a composite that demonstrates superior physical properties. As a final comment, it has been proven that im- mediate high intensity light polymerisation creates the greatest polymerisation stress. Ilie et al state that‘fastcontractionforcedevelopment,highcon- traction stress and an early start of the stress build up cause tension in the material with possible sub- sequent distortion of the bond to the tooth struc- ture’.67 This finding has been collaborated by many others in the scientific literature with resultant rec- ommendations for a soft start or lower energy over a longer period of time.68,69 Miller states that ‘man- ufacturers continue to make outlandish claims of their curing capabilities, most of which fall into the ‘toogoodtobetrue’category’70 andSwiftconcludes that‘thecuringtimesrecommendedbyamanufac- turer might not deliver the amount of energy re- quired to adequately cure composite, even under theideallaboratoryconditions’that‘veryshortcur- ing times are not a good idea in most clinical situa- tions’ and that ‘longer curing times are required’.71 As well, Swift states that ‘instead of obtaining a boost,the“turbo”tipactuallywillreducetheamount of light reaching the composite to initiate the poly- merisation process.’72 Fig. 11_Multiple MacroLock X-RO (Clinical Research Dental) fibre post segments (covered with a bonding agent which is first light cured) are verified for fit into the distal and two mesial canals. Fig. 12_The Cosmecore A2 is injected into the bottom of the pulpal area filling to one half of the crown height, followed by the placement of the MacroLock X-RO segments at the canal orifices. Fig. 13_Occlusal view of the Cosmecore placed half way up the coronal tooth structure with the three segments placed. This first layer was light cured and followed with the completion of the final Cosmecore layer cured for 20 seconds. Fig. 14_Post-operative radiograph of the completed restoration. Fig. 11 Fig. 12 Fig. 13 Fig. 14