Please activate JavaScript!
Please install Adobe Flash Player, click here for download

implants0112

case study I help prevent cortical vascular perfusion disorders (cortical plate perfusions) or arterial vessel damage. This appears to be especially important in areas in which hard- and soft-tissue stability is required for long-term results, for example for biomechanical concepts that require submillimetric precision. Fur- thermore, tissue stability should be considered in all areasofthemouthforaestheticandtrophicreasons. On the one hand, CT scans to date offer low-res- olution 3-D images of the bone. The software avail- able,ontheotherhand,deliversbothgoodplanning andsafesleevepositionsandaxesindependentlyof the technique used to obtain a surgical stent. How- ever,wecannotrelyontheplanning,sinceitcannot discriminate errors. As two superimposed low-res- olution 3-D images cannot result in a high quality imageoftheimplant,relyingontheplanningwould increase imprecision in accuracy measurements. I thereforerecommendplatformpositioningaccord- ing to mathematical criteria in order to achieve a correct, prosthetically driven position. When sleeve placement is considered, jig corre- spondence between the abutments on the master cast analogues and the same abutments’ clinical position on the implants can help avoid inaccura- ciesintermsofeitherthesleevepositionortheaxes ofthesurgicalguide.Furthermore,itcanhelpeval- uate inaccuracies resulting from using a smooth sleeve. Todate,nopublicationshavereportedonsucha technique, presumably because this kind of verifi- cation can impose too much stress on any method owing to the time required to ensure precision this way. Indeed, repeatability seems incidental to the thread-timed sleeve. Thread timing can be an im- passe on the way towards a precisely placed im- plant, since analogues and implants cannot be forced into the same positions both repeatedly and operator independently. In other words, it is un- likelythatallrelevantparameters,suchastheposi- tion in the ridge and the axis, the depth and the ro- tational feature orientation, can be taken into ac- count. No publications have reported on such a tech- nique, either, simply because no method has been concernedwithverifyingaccuracysoprecisely.Re- peatability is incidental to a thread-timed sleeve (that is, something able to force both analogues and implants into place in the same repeatable and operator-independent positions). Thread timing is essential. If we do not accept this, we must accept imprecision. The parameters that define the plat- form—position in the ridge and axis, depth and ro- tational feature orientation—should all be re- spected. If we miss one parameter with a smooth sleeve we miss them all. In the case reports cited, superimpositionoftheplanningwasdoneafterthe pts. had been scanned again post-operatively. There was complete accuracy between the master model and the clinical results. In order to further- more demonstrate how this device could work in- dependently of the way the surgical guide is pro- duced, no industrially manufactured surgical guideswereused.Instead,adigitalcastandastone cast were used with an approximate protocol for transferring data from the software and the stone model, and plain resin was chosen as the provi- sional material. Moreover, it seemed important to understand thatcomparingpost-operativeclinicalCTresultsto the planning through superimposition can be mis- leading in measuring the accuracy of an implant. Contrarily, a comparison between the clinical re- sults with either an STL or stone model on which analogues were placed by using the same threaded guiding device offers better accuracy measure- ment. Although software is essential to planning and creating a surgical guide with an accurately embedded sleeve, accuracy relates to the concepts ofthreadtimingandimplantphaseandnottosoft- ware. In the case reports cited, software was there- fore used to provide qualitative data exclusively. In general, aggressive marketing tactics are an important ethical factor when computer-guided implant placement is considered. The Millennium ResearchGrouphasestimateda20%growthinthe number of guided implant placements by 2013. Similarly,dentistsarelikelytoincreasinglyperceive the need for planning software and drilling tem- plates. In the future, however, CAD/CAM tech- niques will not only be applied in planning, but also be used for surgery in order to enhance prosthesis and tissue stability. A passive device that is easy to handle and based on thread timing can pave the way to computer-guided progress._ Editorial note: A list of references is available from the publisher. I 27implants1_2012 Dr Gian Luigi Telara Studio Odontoiatrico LippiTelara ViaVorno,9/4 55060 Guamo Lucca Italy Tel.:+39 05 8394 7568 lippitelara@gmail.com _contact implants