Dental Tribune United Kingdom Edition

page 23DTß nique allows for a standardised procedure and easy quality check- ing, in comparison to traditional operator-performed techniques, which are open to in-accuracies. Creating customised multi- bracket appliances In virtual orthodontic and surgical planning, it is possible to create a digital orthodontic model once 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 visualisation of the dento-alveolar relationship and can consequent- ly 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 soft- ware shows two overlapping im- ages, differently coloured to dis- tinguish the initial situation from the ideal one (Figs 7 & 8). As a result, a digital model is created, containing all the details to reach a functional occlusion. The first step in the process of creating a customised bracket is possible thanks to CAD/CAM technology.11,12 The CAD/CAM technique entails two phases: the design phase (CAD) and the manufacture phase (CAM),13 per- formed through computers that send instructions to milling ma- chines 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 print or plastic materials/composites, laser sintering (SLS) or laser fu- sion (SLF) of metal materials. The elements that allow the bracket customisation depend on its base. The base is designed through the CAD software and placed on the centre of the den- tal surface. The software will then allow us to customise the bracket (Figs. 9 & 10). In design- ing 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 cus- tomisation entails the additional modification of the angle be- tween the bracket base and the twin portion. This is the ideal, considering that the spatial pa- rameter of the dental elements might vary according to the different malocclusions. Once the design phase has been finalised, the brackets are ready for manufacture by a mill- ing machine. These machines, which mill very small items, need to be run in a standardised envi- ronment with maintained condi- tions to guarantee high precision while minimising the possibility of errors. Consequently, the higher the precision required, the larger the milling machine will be. It is also necessary to place the ma- chine in a dedicated environment with a special floor cover with amortising panels that stabilise the cutter and partially absorb the vibration produced. Moreover, a very small cutter of approximately 0.001 mm needs to be used. For example, consid- ering that the smallest cutters can remove up to 3 per cent of a mil- limetre each time, three to four passes will be required to create the mesh facing the tooth (Fig 11). The technological progress represented by CAD/CAM as de- scribed is based on the digital design feature and the computer- automated manufac - turing pro- cess.14 The main advantages are better control of the production process and a significant reduc- tion in operator-driven errors, while enabling the use of sophis- ticated materials, such as Grade 5 titanium, which was not possible with traditional techniques.15 DT Editorial note: A list of referenc- es is available from the publisher. Fig. 6_3-D rendering and selection of anatomic structures. Fig 6 Fig. 7_Pre- and post-treatment maxillary superimposition. Fig. 8_Pre- and post-treatment mandibular superimposition. Fig 7 Fig 8 Fig 9 Figs. 9 & 10_Customised bracket details. Fig 10 Fig. 11_Bracket mesh. Fig 11About the author Prof Giampietro Farronato Institute for Clinical Orthodontics / Clinical Orthodontic Institute Via Commenda, 10 20122 Milan, Italy giampietro.farronato@unimi.it October 29 - November 4, 201224 Clinical United Kingdom Edition