CAD0110

urement depth has been increased by 20 per cent and the focus depth deepened to 14 mm. The sharpness of individual images has been height- ened, and marginal blurring eliminated. Blur con- trol (automatic capture), the sensitivity of which can be pre-selected, checks the intended image, andthecameraautomaticallytakestheimageonly when it is certain there is no blurring. In quadrants and across the dental arch, any number of pictures can be taken as an overlapping sequence. The 3-D image catalogue manages the individ- ual images on the screen. The software assesses their usefulness, marks and rejects useless scans, and joins the images to form a complete row of teeth(matching)andavirtualcastmodelledonthe naturalexample.Imagesacquiredatthebeginning of the sequence, the quality of which may have beenlessenedowingtothepresenceofrubberdam or cotton rolls, are automatically exchanged for asuitableimagepairassoonasthisisfound.Inthis way, inadequate images are quickly replaced. In vitro studies in the laboratory at the Uni- versity of Zurich in Switzerland have shown that the image accuracy deviates from the reference measurement of a master laboratory scanner by only 19µm—this is equivalent to one-third of the diameter of a human hair. This means Bluecam’s accuracy is similar to that of stationary laser scan- ners. Such precision increases the marginal fitting accuracy of the restoration; thus, less excess occurs during adhesive luting, which in turn takes less time to remove. Because of the image depth and focus depth, it is not necessary to keep an exactly determined distance from the preparation; the camera’s prism window can be placed directly on the tooth, which makes image acquisition easier, particularly in the distal region. The Autocapture function, responsi- ble for actually taking the image, engages auto- matically upon ensuring that the image is in focus. Hence, there is no need to operate a footswitch, which requires eye–foot coordination. This means that an entire quadrant can be scanned in 30 sec- onds. The blur control makes the image sequence and menu operation accurate and simple; thus, thisphasecanbedelegatedtothedentalassistant. If the acquisition unit has a wireless or WLAN con- nection to the milling unit, the system can operate without power with no data loss for up to six min- utes, thanks to its own optional, uninterrupted power supply—ideal for changing location during the milling/grinding phase. _Up to four-unit bridges chairside Bluecamtakesabout30secondstoscanacom- plete quadrant and is suitable for scanning stone casts. In addition, bite records with static and dynamic occlusion are digitised and prepared for functional articulation of the restoration. After selecting bridge tooth databank, the preparation for a four-unit bridge can be scanned with Bluecam. This enables the construction and chair- side manufacture of long-term, provisional com- posite-resin restorations employing the CEREC milling unit, which broadens CEREC’s indication spectrum considerably. As when constructing crowns with CEREC 3D, fissure axes and cusps of the adjacent teeth are analysed—if desired, the antagonists’ morphology is also analysed—and incorporated into the occlusal surface calculation. The software adjusts the occlusal contact points and sliding planes of the crown construction to the occlusal surface I 39 industry report _ digital impression-taking I CAD/CAM 1_2010 Fig. 3_Crown restoration: adjusting the counterbite for occlusal surface design, region 24. (Image: Götte) Fig. 4_Completing the crown’s occlusal surface. (Image: Götte) Fig. 3 Fig. 4