Implant Tribune Italian Edition

12 Implant Tribune Italian Edition - Settembre 2013Letteratura Internazionale Advantages of 3-D planning for implants A. Grandoch, P. Ehrl Introduction Implantology is predominantly a surgical and prosthetic subject area. Its aim is both functional and aesthetic restoration. Today, one can place an implant in the jawbone with a high probability of success if there is good bone support. There are, however, concerns with regard to bone defects, optimum aesthetic and functional positioning of the implant and the soft-tissue situa- tion, possible requiring partial re- construction. The ideal number of implants for large superstructures is still a matter of debate. Functionality, durability and aes- thetics are aims that should, in general, be achieved as simply as possible using favourable and con- ditionally reversible techniques with minimal damage, even in problematic cases. Restoring teeth today has become easier to achieve but whether the cost–benefit ratio is satisfactory must be established for each case. There is still no consensus on these aims and perhaps success can be defined only individually. Expec- tations regarding implantological solutions have increased owing to significant technological advanc- es. One may distinguish between general success criteria valid for all implants and criteria for special indications. While some scientif- ic societies recommend replacing lost teeth with implants as the optimal treatment, and bearing in mind that the goal is restoration of natural conditions, one has to ascertain whether this is valid for single-tooth and multiple-tooth replacement for each case. Reasons for suboptimal solutions are man- ifold, ranging from poor initial conditions associated with a higher treatment risk to socio-economic limitations. One cannot write about implant treatment in general, as too many parameters play a role, particularly because each case differs from an- other. Moreover, there are no gen- eral recommendations with regard to methodology. This is hardly sur- prising, since various methods are used, of which many have limited application and quickly become out of date. There is no widely agreed upon gold standard1 . Methods In 2000, CBCT was introduced to our clinic with hesitation initial- ly and limited to more extensive problems and progressive diseases. It was used increasingly and has been used for almost all implant surgeries since 2008. Three-dimen- Figs. 1a-f -Single-tooth replace- ment with 3-D planning pre- and post-augmentation: Massive defects in the buccal lamella, re- gions 11 and 21 (a). The dimensions of the defects are visible in the sagittal plane (b). After horizontal bone grafting (c). Three-dimen- sional planning post-augmen- tation (d). Post-implantation (e). Patient with crowns (f). sional diagnostics undisputedly offer greater insight, thus increas- ing the quality of the treatment. Three-dimensional planning, how- ever, always means considering the prosthetic planning and the ana- tomical substratum. This is done digitally or via conventional casts. Even before the introduction of 3-D technologies, backward planning2 demonstrated that viewing the de- sired treatment result is helpful in achieving the result. Here too, we initially applied backward plan- ning to cases requiring extensive treatment at first, until we learned that planning is useful for sin- gle-tooth replacement too. Each of these techniques – con- ventional casts and CBCT scans – can be helpful, contributing to a distinct improvement in the treat- ment results in the hands of the ex- perienced implantologist. The next step would therefore be to connect these two techniques. After purely digitally controlled navigation was found to be inaccurate, surgical guide systems, based on planning software, became available. Currently, we are making the step from plaster cast and wax-up to digital model and digital recon- struction. This interesting new ap- proach has to prove its worth in the practice first. Therefore, we have to determine which of the many dig- ital features are essential in treat- ment of the patient. Main features of 3-D planning Only by the evaluation of 3-D data does a preoperative decision on how the desired prosthetic result can be obtained become possible. With the final result in view and mind, a solid basis for deciding upon the necessity and type of aug- mentation and whether removable or fixed dentures are indicated in edentulous jaws is provided. There are often bone defects, whose ex- tent must be evaluated. They are classified according to Fallschüssel and Atwood and the classification demonstrates that, as a rule, hori- zontal bone loss occurs first, while vertical bone is lost gradually. Restoring horizontal bone is im- portant for prosthetic restoration primarily for aesthetic reasons in the anterior area and primarily for functional reasons in the lateral ar- eas concerning the position of the implant in the dental arch. These defects can be optimally corrected via surgical restoration of the orig- inal bone volume. For each case, measurements for positioning the implant (such as inclination – to be performed by the surgeon) and measurements for the prosthesis (to be done by the dental techni- cian) must be taken. The latter, for example, buccal crown overhangs or mucosal facings, prevent hy- gienic design of the superstructure and quite often result in aesthetic deficiencies. If restoration of vertical bone vol- ume is necessary, for instance with Fallschüssel Class 4 frontal or 2 lateral or Atwood Class 4 defects, a more costly two-step technique has to be followed in most cases. At this point, it should be noted that almost all the atrophy patterns mentioned only involve the jaw and do not concern the functional components of the dental arches. Arutinov et al.3 postulate that this must be compensated for by angled implants. Kinsel et al.4 conclude that only the length of the implant Fig. 2 - Depiction of anatomical varieties in the lateral mandible (classification according to Atwood). Figs. 3a & b - Planning in the lateral mandible with cast in situ (SICAT; a). Post-implantation with surgical guide for control (b). is significant for implant loss. This means that as great a bone volume as possible must be used. All of the above-mentioned planning deci- sions can only be made soundly if information about both the 3-D anatomy and the desired prosthet- ic solution is available. The guidelines of the European Association of Dental Implantolo- gists5 offer a critical discussion of angled and short implants. Angled implants require a bone quality above 3, 3-D planning and guided implantation, among others. Planning based on an impression with fabrication of a planning cast is critical for the final outcome of implant placement and thus for the procedure. This will determine the required treatment steps and desired treatment outcome. Quite often, this step is not accorded the necessary importance in dai- ly practice. Adequate planning should be done by the dentist and a special appointment with the patient should be made to obtain consent. With two-step procedures, repeating planning after augmen- tation and a second 3-D radiograph may become necessary. Digital 3-D planning Today’s prosthetic planning possi- bilities offer alternatives to conven- tional casts. Two digital prosthetic planning tools will be discussed here, SimPlant (Materialise Den- tal) and SICAT/CEREC (Sirona). Both these tools are alternatives to the conventional approach described above via digital planning. With both methods, the surface of the neighbouring teeth and soft tis- sue is scanned and matched to the radiological 3-D data. This can be done from a cast (SimPlant and SICAT) or an intra-oral scan (SICAT OPTIGUIDE procedure). > pagina 13 ARTICOLO IN LINGUA ORIGINALE