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Dental Tribune United Kingdom Edition

I n 1985, Prof Werner Mör- mann, Dr Marco Brandes- tini and their team laid the foundations for a new treat- ment system consisting of op- tical impression-taking, CAD and numerically controlled milling. This new concept motivated large numbers of clinicians and prompted them to carry out their own follow-up investigations. Today, CEREC is one of the most closely scrutinised dental pro- cedures, a fact reflected in more than 250 clinical studies and ap- proximately 6,500 longitudinal studies of restorations. Long-term observations in- dicate that adhesively bonded restorations fabricated us- ing the first versions of the CEREC system (CEREC 1 and 2) achieved higher survival probability rates (according to Kaplan–Meier) than conven- tional layered ceramic restora- tions. 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 exten- sive long-term experience, there are convincing reasons for recommending CEREC- fabricated inlays, onlays,partial crowns, veneers, anterior crowns and posterior crowns as an alternative to convention- al metal-based restorations. Immediate treatment stabi- lises enamel The goal was to deploy CAD/ CAM technology to create im- mediate all-ceramic restora- tions chairside without the need for temporaries. Clinical experience has demonstrated that provisionally restored in- lay cavities have a significant, negative influence on the in- tegrity of the enamel. In the course of chewing simulations, cracks occurred in the oral and vestibular enamel surfaces. In addition, spalling was observed at the enamel margins. Such defects did not occur in cavities that had been treated immedi- ately using chairside CEREC inlays. The conclusion was clear: the immediate treatment of the tooth cavity with chair- side inlays and the elimination of the need for a temporary restoration reduce the risk of enamel cracking and marginal spalling. The micromechanical bond between the ceramic inlay and the hard tooth tissue stabilises the cavity walls. In combina- tion with the adhesive bond, the stabilising effect of the im- mediate CEREC restoration on the residual tooth obviously off- sets the consequences of wider adhesive gaps, as evidenced in long-term clinical findings. High-strength CEREC crowns So far, long-term investigations have concentrated almost ex- clusively on CEREC crowns made of feldspar ceramic mate- rials. At the School of Dentistry, University of Michigan, we set out to investigate the material suitability of lithium disilicate (LS2, IPS e.max CAD, Ivoclar Vivadent) for full contour, mon- olithic crowns. Our aim was to utilise the enhanced flexural strength of LS2 (360–400 MPa) in order to withstand the chew- ing forces in the premolar and molar regions. The full crown preparation included 2.0 mm functional cusp reduction, 1.5 mm oc- clusal 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 patients and then placed with the aid of dual-cure luting cement. There was a small degree of sensitiv- ity reported in the first week post-operatively. This had sub- sided by the third week and there were no reports of sen- sitivity at the one- or two-year recall evaluation. After two years of clinical service, there were no clini- cally identified cases of crown fracture or surface chipping. Clinical monitoring revealed a positive long-term survival prognosis. Although two years in situ is a relatively short pe- riod of time, the survival rates are on par with those obtained in similar studies of ceramic crowns (Fig. 1). DT 25 years of proven clinical performance Dr Dennis J Fasbinder, looks at CEREC About the author Dr Dennis J. Fasbinder is Clinical Professor in the Department of Cari- ology, Restorative Sciences and Endo- dontics at the University of Michigan. Fig. 1_LS2 crowns after the two-year recall visit. ‘This new concept motivated large numbers of clinicians and prompted them to carry out their own follow- up investigations.’ New 2011 or a Belmont equipment package and we will pay the VAT for you Order dental cabinets direct from our factory Register for your discount today at scottdental.co.uk ‘After two years of clinical service, there were no clinically identified cases of crown fracture or surface chipping’ 25ClinicalJune 6-12, 2011United Kingdom Edition