Implant Tribune Italian Edition

13Implant Tribune Italian Edition - Settembre 2013 Letteratura Internazionale www.sirona.it Tel. 045/82.81.811 ORTHOPHOS XG 3D. Ideale per il lavoro quotidiano dello studio dentistico, l’apparecchio ibrido universale ORTHOPHOS XG 3D unisce i vantaggi dell’imaging 2D e 3D. Con un volu- me cilindrico del diametro e dell‘altezza pari a 8 cm, ORTHOPHOS XG 3D è indispensabile per ogni esigen- za diagnostica dello studio dentistico: una scansione è sufficiente per rilevare le intere arcate dentali del paziente. Sarà una buona giornata. Con Sirona. QUALITÀ HD. < pagina 12 Then, a digital cast is created with the prosthetic planning pro- gramme. The objectives of these methods are simplification and shortening of the workflow (Figs. 1a & b). The precision of these methods is particularly notewor- thy and figures for the overlap of the radiographic data and the op- tical scan obtained with the SICAT CAD/CAM method are available. nThe difference between CBCT data and the optical surface scan is between 0.03 (0.33) and 0.14 (0.18) mm6 . After scanning, crowns can be planned with the help of the CEREC crowns and bridges plan- ning software. The precision of the digital SICAT method depends on the resolution of the respective data. For analogue impression techniques, for example, a preci- sion between 0.1 and a maximum of 0.2 mm is required7 , as well as a gap of 0.027 to 0.101 mm between the crown and natural tooth8 . The precision of the two methods therefore is similar. This holds true if all error sources are tak- en into account: CBCT scan, the transfer to the surgical guide, the repositioning of the guide, the play of the drill and deviation when placing the implant. The surface scan improves precision. The advantage of this procedure is that the production of a plan- ning cast is unnecessary (Fig. 1b). The OPTIGUIDE method makes an important step towards the digi- tisation of prosthetic and implant planning, resulting in greater planning reliability and preci- sion. Unfortunately, there are restrictions concerning partially edentulous jaws and cases with extensive metal artefacts. Single-tooth replacement Expectations are high with sin- gle-tooth replacement. The tar- get is to achieve a state equal to the conditions before tooth loss. Tooth replacement in the aesthet- ic region is particularly demand- ing. Anatomical prerequisites pri- marily determine the treatment method. For example, an implant may be placed into a particular alveolus immediately without 3-D planning. For delayed implan- tation, a cast and 3-D radiograph should be used. By planning the implant incli- nation and relation to the neigh- bouring teeth, the emergence profile and the positioning of the crown can be favourably planned. Guided implantation is particularly helpful in individual implants when several individu- al implants have to be placed or neighbouring teeth are endan- gered where there is only limited space. In addition, the patient’s wish to see the expected outcome can be met. However, visualising opti- mum results involves the danger of arousing expectations that cannot be guaranteed. Figures 2a to f show the two-step reconstruction of a horizontal de- fect with 3-D planning. Shortened row of teeth In reconstruction of a shortened row of teeth, the function and particularly the support of the temporomandibular joint is im- portant. The number of teeth necessary for prostheses has not been determined definitively. Within the last few years, recon- structing up to the first molar, and up to the second premolar in cases with an extension, has been usual. Generally, alveolar atrophy pro- gresses most rapidly horizontally in the lateral jaw area, starting buccally, and frequently is later followed by atrophy of the verti- cal dimension. If one avoids augmentation or performs only minor augmenta- tion, longer prostheses are neces- sary for short implants, which are situated more lingually than the natural teeth. The use of short implants in the lateral jaw is subject to several re- strictions, such as good bone qual- ity, primarily connected crowns or caps, no extension bridges, no lateral excursion contacts and no para-functional habits. Angulation is limited to 20 degrees. Furthermore, angled implants are not recommended for a shortened row of teeth according to the guide- lines of the European Association of Dental Implantologists5 . If alignment is carried out with respect to antagonists in the nat- ural dentition, positioning the new implant-borne crowns will not lead to any functional losses, unless the antagonists were not functionally situated in the den- tal arches originally. Space towards the cheeks must be regained, even if patients with a long case history sometimes com- plain about spontaneous cheek biting and bolus retention. > pagina 14