CAD/CAM - international magazine of digital dentistry

opinion _ CBCT I Fig. 3_Digital cast. Fig. 4_CBCT digital cast interface. _effective representation of true 3-D morphology ofthecranialstructureswithoutdistortion,avoid- ing projection and identification errors; _reduced operator bias because the measurements are performed automatically; _simplicityandrepeatabilityintheidentificationof landmarks, using true anatomic structures with- out superimposition or the problems of geometric construction; _ability to obtain CA using the three dimensions; and _dento-skeletal alterations can be analysed in 3-D in order to determine appropriate treatment. _Combined orthodontic and surgical planning The introduction of 3-D imaging techniques has revolutionised the planning phase of combined orthodontic and surgical treatment. The use of the computer,togetherwithdedicatedsoftware,allows for a fast, precise and standardised procedure. 3-D virtual planning entails the following: _CBCT scan; _high-definition impression; _reference aligner; _digital scan cast; and _CBCT digital cast interface. Usingvirtualplanning,itispossibletoobtainthe virtual visual surgical treatment objective and the virtualorthodonticmodel.High-definitionimpres- sions are obtained using polyvinyl siloxane, which guarantees well-defined details while allowing for the double-pour method. Double-poured casts are necessary to obtain an adequate scan and require the use of both a full cast and individual dental elements selected from a second cast. Single dental element scans allow for proper analysis of contact points. An optical cast scan is performed using structured-light scanners, which produce a 3-D image captured by a camera. In this manner, a group of points is determined by the software, which then determines the coordinates of the acquired points and finally creates the 3-D image (Fig. 3).5 Moreover, the digital dental cast is then com- bined with the CBCT scan, which allows for a very detailedanalysisofboththebone(throughtheCBCT scan) and the dental structure (through the cast scan). CBCT does not provide enough data regard- ing all the dental details necessary to produce the orthodontic model (Fig. 4).6 In order to superimpose the two records prop- erly,aspecificthree-contactpointbiteregistration wax, known as the reference aligner, has been in- troduced.Thereferencealignerneedstobeapplied to the teeth when the high-definition impres- sions are taken. It is made of Moyco (an extra-hard wax) and consists of a supporting arch and three spheres. These are made of calcium-based glass, which has cast-pouring radiopaque properties. The wax is applied during CBCT and is placed between the cast arches during the optical scan (Fig. 5). I 27CAD/CAM 2_2012 Fig. 3 Fig. 4 GoSx – Me = 77,46 mm ± 2 GoDx – Me = 77,35 mm ± 2,03 CdSx – GoSx = 51,49 mm ± 3,69 CdDx – GoDx = 52,18 mm ± 3,48 S – GoSx = 80,05 mm ± 2,4 S – GoDx = 80,15 mm ± 2,37 ANS PNS ^ GoSx Me = 41,12° ± 0,81 ANS PNS ^ GoDx Me = 41,12° ± 0,9 S N ^ GoSx Me = 46,21° ± 1,11 S N ^ GoDx Me = 45,94° ± 1,24 CdSx GoSx Me = 118,88° ± 2,58 CdDx GoDx Me = 118,83 ± 2,51 CdSx GoSx N = 54,31° ± 1,22 CdDx GoDx N = 54,3° ± 1,2 N GoSx Me = 65,64° ± 0,98 N GoDx Me = 65,58° ± 1,09 PNS – A = 44,82 mm ± 1,1 S – N = 65,3 mm ± 1,35 N – Me = 106,33 mm ± 2,8 N – ANS = 47,92 mm ± 1,33 ANS – Me = 59,49 mm ± 1,62 S N A = 80,66° ± 0,89 S N B = 78,24° ± 0,93 A N B = 2,62° ± 0,31 Ba S N = 130,03° ± 1,76 Table II_Normal values range.