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implants the journal of oral implantology United Kingdom Edition

22 I I clinical_ guided implantology implants2_2012 like guide is certainly better than nothing. Many systems are available today, and from a theoretical perspective they have been cate- gorised into semi-active and passive systems. The systems in the first category, whatever thetechniqueusedtomakethesurgicalguide (STL or stone surgery), have metal smooth guiding sleeves, which the implant and the implant-driver must pass through, and the second systems, also called navigation sys- tems, do not have any metal sleeves and the surgeon is guided by the monitor. In this cat- egory, the surgical handpiece is indexed to spatial markers inside a surgical guide that is inserted into the patient’s mouth, but not in the surgical area. These spatial coordinates are viewed by an infra-red system, which transfers data to the computer, allowing the clinician to follow the surgical steps on the monitor. Alarm lights and sounds will warn the clinician of deviations from the desired position. I propose a new definition of a pas- sive system: a passive system must allow any operators (ie it must be operator indepen- dent) to achieve the same, repeatable results at an acceptable inaccuracy threshold.4 The accepted inaccuracy must allow clinicians to obtain a good metal-to-metal fit without placingtensionontheimplants.This“towhat extent” predictability can determine the reli- ability of treatment. In fact, in fixed prosthe- ses on natural teeth, passivity (at an accept- able gap) is about 40 to 50μ in the arch; the same values could be considered acceptable for prostheses on implants. According to this definition, none of the systems on the mar- ket has replicable results, and have metal or virtual smooth sleeves. They must thus be considered metal or virtual smooth semiac- tive systems. I have developed a new device according to the mathematical concepts of thread timing and implant phase, which can be applied to the implant movement while being screwed, thus allowing clinicians pas- sivity during implant placement. In the fu- ture, owing to the predictability of implant placement, the proposed device could be fundamental to achieving the desired goals in computer-guided implantology. _Materials and methods The implants were placed using the bottle- necklike device, which begins implant rota- tion before it can touch the bone, thereby avoiding bone interference with implant movement owing to bone density gradients (“bone guidance”). The prototype of the de- vice consists of: an internally threaded sleeve (“embedded sleeve”, with a “helical gear” fea- ture at its top that is useful during implant placement; an externally threaded sleeve Fig 1i_Assembly while being screwed. Fig 2_Surgery planning for the STL case. Fig 3a&b_Surgery planning for the stone case. Fig. 1g Fig. 1h Fig. 1i Fig. 2 Fig.3a Fig.3b