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CAD/CAM - international magazine of digital dentistry

I special _ guided implantology 14 I CAD/CAM 1_2012 Fig. 15_Vertical clearance paragon. particular, a longer mounting period will force the implantdownwardsintothebone,withconsequent verticalbonestripping,whereasashortermounting period will force the implant to rotate horizon- tally, with consequent horizontal bone stripping. Self-tapping implants should show better torque control. Rigidity The device must be secured to the surgical guide to resist the rotational torque and vertical torque always present during the implant rotation inside the bone. Componentsandundercuts Intheprototypedevice,adriverforaratchetwas used. It was completely redundant because the ratchet can cooperate directly with a plug-top fea- ture for a ratchet at its top; thus, the driver is some- thingthatcanbeeliminated.Oncetheassemblyhas been fixed to the embedded sleeve, the plug can be screwed with the fingers, at least until sufficient torque is found, when a ratchet can be used. When multiple implants have been planned, in case of divergent implants, hex undercuts could preventthesurgicalguidefromreleasingitselffrom thebone,oncetheimplantshavebeenplaced.Inor- der to resolve this, the device, at least the mounting part, must be removed from the surgical guide. The deviceisthusdividedintwocomponentsandthelid, which is integral to the driver, can be unscrewed, leaving the surgical guide along with all the other componentsstillfastenedtoit,butdisengagedfrom the implants, freely and easily removable. For single implant placement, the lid is not nec- essary, because there are no hex undercuts. In this case, a bottle-plug with one component will be sufficient. Crestmodule The implant crest module morphology does not affect this guiding device because the bottle-neck’s internal diameter is just a little wider than the im- plant diameter at any point (platform or below the platform).Bytheway,additionalthreadsinthecrest module are not important either because, mathe- matically speaking, they are harmonic waves of the implant period (thread pitch). Mastercast The helical gear can easily be oriented vestibu- larly in the threaded guiding device before pouring the master model. Verticalclearance To make the correct surgical guide, the helical gear must be engineered in the planning at a multi- ple pitch distance from the bone, just equalling the implant length (the implant must start rotating before it touches the bone to avoid bone guidance). For instance, the distance will be 9 or 10 mm for 9or10mmlongimplantswitha1mmpitch,andthe distance will be a multiple of 0.75 for a 0.75 mm pitch (9 mm will correspond to 12 implant revolu- tions and 10.5 mm to 14 revolutions). The average mouth opening values should be considered. In case of tapered implants, a short distance can be considered because the implant apex can enter the osteotomy hole without being engaged. To reduce verticalclearance,thedevicecanbepre-assembled, thus obtaining a working length even shorter than that of the present systems (Fig. 15). A shorter ver- tical clearance is possible also with trans-mucosal implants because the platform results are more superficial._ Editorial note: This article was first published in Dentale Implantologie8,374–82(2004),SpittaVerlag.Acomplete listofreferencesisavailablefromthepublisher. Fig. 15 Dr Gian Luigi Telara Studio Odontoiatrico LippiTelara ViaVorno,9/4 55060 Guamo Lucca Italy Tel.:+39 0583 947568 lippitelara@gmail.com CAD/CAM_contact