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08 I I opinion _ CEREC CAD/CAM 1_2011 Fig. 1_LS2 crowns after the two-year recall visit. _In 1985, Prof Werner Mörmann, Dr Marco Brandestini and their team laid thefoundationsforanewtreatmentsystem consisting of optical impression-taking, CAD and numerically controlled milling. This new concept motivated large numbers ofcliniciansandpromptedthemtocarryout their own follow-up investigations. Today, CERECisoneofthemostcloselyscrutinised dental procedures, a fact reflected in more than250clinicalstudiesandapproximately 6,500 longitudinal studies of restorations. Long-termobservationsindicatethatadhesively bonded restorations fabricated using the first ver- sionsoftheCERECsystem(CEREC1and2)achieved higher survival probability rates (according to Kaplan–Meier) than conventional layered ceramic restorations. CEREC restorations with service times in excess of 20 years still display a degree of clinical excellence, which is normally attributed to metal- based restorations. On the basis of this extensive long-termexperience,thereareconvincingreasons forrecommendingCEREC-fabricatedinlays,onlays, partial crowns, veneers, anterior crowns and pos- terior crowns as an alternative to conventional metal-based restorations. _Immediate treatment stabilises enamel The goal was to deploy CAD/CAM technology to create immediate all-ceramic restorations chair- side without the need for temporaries. Clinical expe- rience has demonstrated that provisionally restored inlay cavities have a significant, negative influence on the integrity of the enamel. In the course of chewing simulations, cracks occurred in the oral and vestibular enamel surfaces. In addition, spalling was observedattheenamelmargins.Suchdefectsdidnot occur in cavities that had been treated immediately using chairside CEREC inlays. The conclusion was clear: the immediate treatment of the tooth cavity with chairside inlays and the elimination of the need foratemporaryrestorationreducetheriskofenamel crackingandmarginalspalling.Themicromechanical bond between the ceramic inlay and the hard tooth tissue stabilises the cavity walls. In combination with theadhesivebond,thestabilisingeffectoftheimme- diate CEREC restoration on the residual tooth obvi- ously offsets the consequences of wider adhesive gaps, as evidenced in long-term clinical findings. _High-strength CEREC crowns So far, long-term investigations have concen- trated almost exclusively on CEREC crowns made of feldsparceramicmaterials.AttheSchoolofDentistry, University of Michigan, we set out to investigate the materialsuitabilityoflithiumdisilicate(LS2,IPSe.max CAD, Ivoclar Vivadent) for full contour, monolithic crowns. Our aim was to utilise the enhanced flexural strength of LS2 (360–400 MPa) in order to withstand thechewingforcesinthepremolarandmolarregions. The full crown preparation included 2.0 mm func- tional cusp reduction, 1.5 mm occlusal reduction in the central fissure in combination with rounded shoulders and axial reduction of 1.2 mm. Using the CEREC 3 system, 62 crowns were created for 43 pa- tients and then placed with the aid of dual-cure lutingcement.Therewasasmalldegreeofsensitivity reported in the first week post-operatively. This had subsided by the third week and there were no reports ofsensitivityattheone-ortwo-yearrecallevaluation. After two years of clinical service, there were no clinically identified cases of crown fracture or sur- face chipping. Clinical monitoring revealed a positive long-term survival prognosis. Although two years insitu is a relatively short period of time, the survival ratesareonparwiththoseobtainedinsimilarstudies of ceramic crowns (Fig. 1)._ 25 years of proven clinical performance Author_ Dr Dennis J. Fasbinder, USA Dr Dennis J.Fasbinder is Clinical Professor in the Department of Cariology, Restorative Sciences and Endodontics at the University of Michigan. CAD/CAM_about the author ig. 1