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May 2009 | Dental Products Report How to: Fabricate strong restorations Lithium disilicate is used to give a patient with carious teeth strong, esthetic restorations. Dentists today require materials that offer outstanding esthetics, high strength and efficient productivity. Dentistry has always been faced with the challenge of finding ways to combine two incompatible materials in a synergistic way, whether that combination is metal with metal-ceramic or zirconia with zirconia layering ceramic. Simultaneously, dental practices are seeking ways to realize the wonderful opportunities presented by CAD/CAM and digital fabrication techniques that offer the benefits of consistency in the production of a restoration and expanded material options. In satisfying these requirements, lithium disilicate glass ceramic has the potential to provide new options for improving patient care. For the dentist, lithium disilicate is an esthetic, high strength material that can be conventionally cemented or adhesively bonded. In terms of dealing with incompatible restorations, lithium disilicate provides a solution with its ability to offer a full-contour restoration fabricated from one high-strength ceramic, thereby eliminating this challenge. It can be used in all areas of the mouth when specific considerations are accounted for. Case presentation A patient, who had not been to a dental office in almost three years, presented with recurrent caries on existing restorations (Figs. 1 and 2). We decided to treat two to three teeth at a time because of financial restrictions. The existing form and function of the teeth made it necessary to copy the pre-operative size and shape of the patient’s existing restorations. To do this, we used the correlation technique (Fig. 3). After removing the existing restorations, we found a tremendous amount of caries on the patient’s teeth. Although additional procedures were needed, the large amount of dental caries present required immediate attention. IPS e.max CAD LT was used to fabricate the restorations. 01. The decay was removed. A diode laser was used to remove the inflamed tissue (Fig. 4). 02. Cord was packed after the diode laser to further retract the tissue for optical imaging. 03. An opaquing medium was used to spray the teeth to prepare them for optical imaging (Fig. 5). 04. Optical scans were captured by Sirona’s CEREC intraoral acquisition unit and the software used to design the restorations (Figs. 6 and 7). 05. Because of limited clearance on the teeth and the desire for increased strength, the e.max material was used to fabricate the restorations. 06. The milled e.max crown was tried in before crystallization (Fig. 8). 07. After milling, the restorations were stained and glazed in an oven with vacuum to achieve final color and strength (Fig. 9). 08. The restorations were cemented in place. (Fig. 10). Closing thought Indications for the machinable lithium disilicate material are inlays, onlays, veneers, partial crowns, anterior and posterior crowns, telescope primary crowns and implant superstructures. For a posterior crown fabricated to full contour using CAD methods, lithium disilicate offers 360 MPa of strength through the entire restoration. As a result, restorations demonstrate a “monolithic” strength.
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