Theeffectofdifferent materialsandpreparation designs on themarginaladaptation andfracture resistanceofestheticonlays

Abstract

Inthisstudy,twomaterials [IPSe-maxCAD (EX),VITA ENAMIC(EN)],andfour different preparation designs were investigated for their effect on marginal adaptation and fracture resistance.Atotalof fifty-six(n=56) cariesfree humanmandibular molars were used. According tothematerials,teethwere dividedintotwomaingroups(ExandEn)(n=28)which werefurthersubdividedintoeightsubgroupsaccording tothefourpreparationdesign(EX&EN, D1, D2, D3, D4 )(n=7). Controlgroups(D1)receivedMODcavitypreparation,withisthmusdepthof2mm, width3mm, whileproximalboxwere reduced1.5mmbelow thepulpalfloor.Cavitywallswere divergedocclusally about6°,allthewallswereroundedandsmoothenedtoavoidany sharp preparations.The remaininggroups receivedthesameMOD preparationof thecontrolgroups (D1)inaddition:ingroup(D2)thebuccalcuspswerereducedby1.5mm,ingroup(D3)the lingualcuspswerereducedby1mm,whileingroup(D4)thebuccalandlingualcuspswere reduced by 1.5and1mmrespectively.Alloftheocclusalpreparationsweredonewith90° cavosurfacemargins. Allthe preparedsamples were scannedusingCERECOmnicamscannerandthe preparationswerecheckedbythesoftwareforanysharpnessandundercutsbeforerestoration fabrications.Allrestorationsweremilledusing CerecMCXL4.4milling machine.The restorations werecheckedforseating ontheircorresponding preparationsbeforefinalfinishing and glazing. Surfacetreatmentwasdoneonthefittingsurfaceofallrestorationsbefore cementation. IPSe-maxCAD andVITA ENAMICwere etchedusing5%hydrofluoricacid20secondand60 seconds respectivelythensilanized for60 secondsbeforecementation. Ontheotherhandallpreparedteethwereselectivelyetchedwith35%phosphoricacid for20secondsontheenamelmargins.Theetchedsurfaceswerethenrinsedwithwaterspray anddriedwithcompressedair.Amicro-brushwasusedtodistributeathinlayerofbonding agent on the enamel anddentine. Allsampleswere lutedtotheteethusing Duo-Linkresincement (automixed)

andinserted directlyintothe cavityof thepreparedteeth.