CAD/CAM - international magazine of digital dentistry

06 I I CE article _ practical lessons in CAD/CAM _Despite the increasing popularity of the cur- rent CAD/CAM laboratory systems and continuing technical advances, some clinicians have remained reluctant to incorporate the very same CAD/CAM techniques into their clinical chairside practices. Two often-repeated misconceptions relate to the per- ceived lack of strength and lack of aesthetics of the ceramicsavailableforusewiththesesystems.Awide variety of materials are available to use with the E4D Dentist System (D4D Technologies), and each has a separate set of aesthetic and mechanical properties that must be considered. This article will review cur- rent materials and show clinical examples of resto- rations made using the E4D Dentist System. One distinct advantage of chairside CAD/CAM is havingtheabilitytomakerestorationsinasinglevisit from a solid pre-manufactured block that is essen- tially flawless in construction. A pre-manufactured block is made in ideal conditions, and as a result, has an ideal density with none of the residual porosity found in many layered or pressed porcelains. Porosities may act as a weak point and lead to the build-up of internal tensile stress in the ceramic and eventually cause a catastrophic failure. Monolithic restorations have several distinct advantages over layered restorations when it comes to mechanical properties. Layered restorations are often veneered with weak feldspathic glasses that can chip or break, especiallyifnotsupportedproperlybytheframework. Furthermore,onedoesnotneedtoworryaboutde- lamination and micro-chipping of the veneering por- celain,whichhasbeenreportedtobeashighas25per centforporcelain-fused-to-zirconiumrestorations.1 IPS Empress (Ivoclar Vivdent) is a feldspathic glass with approximately 45 % leucite crystals for disper- sion strengthening. The 5 µm leucite crystals improve strength and fracture toughness by acting as “road- blocks” to prevent crack propagation. IPS Empress is anaestheticmaterialandisavailableinpolychromatic blended shades that give the restoration a layered ap- pearance. Empress Multiblock has a flexural strength around 160 MPa and requires isolation and attention todetailwhenbondingtoensurelong-termsuccess. IPS Empress has been on the market for approxi- mately24years,andasaresult,goodclinicalresearch on the longevity of these restorations exists in the literature. A literature review conducted by Brochu and El-Mowafy evaluated and summarized six clin- ical studies that met their inclusion criteria. They CAD/CAM 3_2013 Fig. 1_Patient presents with crown missing from tooth #9. Fig. 2_E4D Dentist System is used to take a digital impression, then the restoration is designed using E4D DentaLogic Software. (Photos courtesy of Dr Wally Renne) By reading this article and then taking a short online quiz,you can gainADA CERP CE credits. To take the CE quiz,visit www.dtstudyclub.com.The quiz is free for subscribers,who will be sent an access code.Please writesupport@dtstudyclub.com if you don’t receive it.Non sub- scribers may take the quiz for a $20 fee. _ce credit CAD/CAM E4D chairside CAD/CAM restorations:Casepresentations and lessons learned Author_ Dr Wally Renne, USA Fig. 2Fig. 1