Dental Tribune Untited Kingdom Edition

21Lab TribuneApril 16-22, 2012United Kingdom Edition Look out for ourfree sample withinthis issue ofDental tribune chanical and labour-intensive procedures (for example wax- ing, investing, burn-out, cast- ing and pressing) involved in the conventional fabrication of a restoration were essentially automated. The dentist and technician had a consistent, precise method to construct functional dental restorations. A file is created within the design software for each pa- tient. The operator can input the patient’s name or record number and selects the appro- priate tooth number(s) to be treated. Each tooth’s planned restoration is checked (for ex- ample full crown, veneer, inlay and onlay). Lastly, additional preferences include material choices and preferred shade. System defaults that can be set ahead of time or changed for each patient are preferred contact tightness, occlusal contact intensity and virtual die spacer, which determines the internal fit of the final res- toration to the die/prepara- tion. All this information can be entered prior to treatment or changed at any time if the actual treatment differs from what was planned. When the images of the preparation, provisional res- torations and opposing denti- tion are captured, the com- puter has all the required information for preparing the working models, prepara- tion and opposing model. The real 3-D virtual model is then shown on the screen and can be rotated and viewed from any perspective (Fig 8). In designing the restoration, the first step must be to define the final restoration’s parameters digitally. This is achieved by employing the opposing and adjacent teeth for occlusal in- terproximal contact areas and, finally, the gingival margins of the preparation. Using input and neigh- bouring anatomic detail as a basis, the software will place the restorations in an appro- priate position—but not to the clinically ideal location. In- stead, the operator relies on his or her knowledge of form and function and experience to reposition and contour the restoration. As the crown’s position and rotation are fine- tuned, the software’s automat- ic occlusion application will readjust each triangular ridge and cusp tip—and the restora- tion’s contours, contacts and marginal ridges—employ- ing the preferences and bite- registration information. The virtual restoration adapts all parameters in relation to the new position. Instantaneous- ly, the position and intensity of each contact point is illus- trated graphically and colour mapped, where it can easily be modified based on the op- erator’s and clinician’s pref- erences. Through a variety of virtual carving and waxing tools, customisation and art- istry are also possible. These tools can be used to adjust oc- clusal anatomy, preferences and contours, reflecting actual laboratory methods. Each step in the process is updated on the screen; therefore, the ef- fect of any changes is immedi- ately apparent. For this case, three files were loaded into the computer software for res- toration design. Scans of the preparations, provisional res- torations and opposing den- tition were joined to form a composite file that represent- ed the patient’s oral situation accurately (Fig 9). Once the final virtual restorations have been completely designed (Fig 10), the milling chamber with the predetermined shade, opacity and size of the IPS e.max block is loaded, an on- screen button is pressed, and an exact replica of the design is produced in ceramic in a short time. Glass-ceramics are cat- egorised according to their ‘However, as restor- ative dentistry shifts further into the digital era, clini- cians must change their perceptions and definitions of the dental laboratory’ page 22DTà