CAD/CAM - international magazine of digital dentistry

I 29 opinion _ CBCT I CAD/CAM 2_2012 the bone bases have been shifted towards their proper position. The latest dental shift software is able to perform single-element segmentation automatically. The operator can obtain a full 3-D visualisationofthedento-alveolarrelationshipand can consequently modify tip and torque, rotate and shift dental elements in the 3-D space in order to simulate the orthodontic treatment. In order to display the results of the pre-surgical orthodontic treatment immediately, the software showstwooverlappingimages,differentlycoloured to distinguish the initial situation from the ideal one (Figs. 7 & 8). As a result, a digital model is cre- ated, containing all the details to reach a functional occlusion. The first step in the process of creating a cus- tomised bracket is possible thanks to CAD/CAM technology.11,12 TheCAD/CAMtechniqueentailstwo phases: the design phase (CAD) and the manufac- ture phase (CAM),13 performed through computers that send instructions to milling machines in order to create the end-product.6 These machines work either through removal (such as a CNC cutter) or through addition—stereolithography (SLA), 3-D printorplasticmaterials/composites,lasersintering (SLS) or laser fusion (SLF) of metal materials. The elements that allow the bracket customi- sation depend on its base. The base is designed through the CAD software and placed on the centre ofthedentalsurface.Thesoftwarewillthenallowus to customise the bracket (Figs. 9 & 10). In designing the bracket, it is possible to distinguish between a partial and a complete customisation. The first entails the customisation of the size and shape of the bracket portion facing the dental surface, but features a standard angle in the non-customisable portion of the twin bracket. Complete customisa- tionentailstheadditionalmodificationoftheangle between the bracket base and the twin portion. This is the ideal, considering that the spatial parameter of the dental elements might vary according to the different malocclusions. Once the design phase has been finalised, the bracketsarereadyformanufacturebyamillingma- chine. These machines, which mill very small items, need to be run in a standardised environment with maintained conditions to guarantee high precision while minimising the possibility of errors. Conse- quently,thehighertheprecisionrequired,thelarger the milling machine will be. It is also necessary to place the machine in a dedicated environment with a special floor cover with amortising panels that stabilise the cutter and partially absorb the vibra- tion produced. Moreover, a very small cutter of approximately 0.001 mm needs to be used. For example, consider- ing that the smallest cutters can remove up to 3 % of a millimetre each time, three to four passes will be required to create the mesh facing the tooth (Fig. 11). The technological progress represented by CAD/CAMasdescribedisbasedonthedigitaldesign feature and the computer-automated manufac- turing process.14 The main advantages are better control of the production process and a significant reduction in operator-driven errors, while enabling the use of sophisticated materials, such as Grade 5 titanium, which was not possible with traditional techniques.15 _ Editorial note: A complete list of references is available fromthepublisher. Figs. 9 & 10_Customised bracket details. Fig. 11_Bracket mesh. Prof Giampietro Farronato Institute for Clinical Orthodontics / Clinical Orthodontic Institute Via Commenda,10 20122 Milan Italy giampietro.farronato@unimi.it CAD/CAM_contact Fig. 9 Fig. 10 Fig. 11