CAD/CAM - international magazine of digital dentistry

30 I I industry report _ lithium disilicate CAD/CAM 1_2012 functional components, occlusal parameters, pho- netics and aesthetics, and continues throughout therestorativeprocess,fromtheinitialconsultation through treatment planning and provisionalisation to final placement. The primary and conventional communication tools between the dentist and technician are: _photography; _written documentation; _impressions of the patient’s existing dentition; _clinical preparation; and _opposing dentition. This information is used to create models, which aremountedonanarticulatortosimulatetheman- dibular jaw movements. Traditionalindirectrestorativeprocess The indirect restorative process involves the following steps: 1. The clinician prepares the case according to the appropriate preparation guidelines, takes the impressions, sends these and other critical com- municationaspectstothelaboratory,andthe lab- oratoryreceivesallthematerialsfromthedentist. 2. Then,theimpressionsarepoured,modelsmount- ed, and dies trimmed. 3. Appropriaterestorations—layered,pressed,milled, cast, or combinations—are made. However, as restorative dentistry shifts further into the digital era, clinicians must change their perceptionsanddefinitionsofthedentallaboratory. Traditionally, a laboratory is the site that receives and processes patient impressions and returns the completedrestorationstotheclinician,whoadjusts and delivers them to the patient. Similar to how the Internethastransformedthecommunicationland- scape,thepossibilityofusingCAD/CAM-restoration files electronically has spurred evolutions in the waydentalrestorativeteamsperceiveandstructure the dentist–laboratory relationship. Thedigitalprocess When the E4D LabWorks system (D4D Technolo- gies) was introduced in 2008 (Fig. 7), it was the first computerisation model to present a real 3-D virtual modelaccuratelyandaccountfortheocclusaleffect of the opposing and adjacent dentition automati- cally.Itenablestheusertodesign16individual,full- contour, anatomically correct teeth simultaneously. The device condenses the information from a com- plex occlusal case and displays it in a user-friendly format that allows clinicians with basic knowledge of dental anatomy and occlusion to modify the de- sign.Oncethishasbeencompleted,theinformation is sent to the automated milling unit. The innovation of digitally designed restora- tions meant that some of the more mechanical and labour-intensive procedures (for example waxing, investing, burn-out, casting and pressing) involved intheconventionalfabricationofarestorationwere essentially automated. The dentist and technician hadaconsistent,precisemethodtoconstructfunc- tional dental restorations. A file is created within the design software for each patient. The operator can input the patient’s name or record number and selects the appropriate toothnumber(s)tobetreated.Eachtooth’splanned restoration is checked (for example full crown, ve- neer, 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,whichdeterminestheinternalfitofthefinal restoration to the die/preparation. All this informa- tioncanbeenteredpriortotreatmentorchangedat any time if the actual treatment differs from what was planned. When the images of the preparation, provisional restorations and opposing dentition are captured, the computer has all the required information for preparing the working models, preparation and opposing model. The real 3-D virtual model is then shownonthescreenandcanberotatedandviewed from any perspective (Fig. 8). In designing the restoration,thefirststepmustbetodefinethefinal restoration’s parameters digitally. This is achieved by employing the opposing and adjacent teeth for Fig. 11_IPS e.max milling blocks, shown in blue stage. Fig. 11