implants - internationalmagazine of oral implantology

isavaluealsoinaclassicalII-stageprotocolandrespectinghardandsofttissuesforlong- termimplantsitestability. Thereisanongoingdebateamongstcliniciansregardingwhichisthebestavailablesys- tem. Vercruyssen summarises this debate.1 The article reviews only some of the published articlesonthistopic.Allofthesearticlesemphasisetheerrormarginsandthattheycanbe consideredclinicallymoreorlessacceptable,anddetermineaccuracyinimplantplacement bymeansofsuperimposition. Inmathematicalterms,“precision”meanstherepeatabilityofameasurement,and“ac- curacy” refers to the correspondence of this measurement to the truth. In our field, accu- racyhasbeenconsideredthecorrespondenceoftheplacedimplanttotheplanning. Fortindefines“accuracy”asanideal,atpresentsomewhatimpractical,whenconsider- ing a definitive prosthesis for immediate loading, with the present systems only offering predictable results (and as such only long-term reinforced provisionals will be available), but does not quantify a threshold.2 According to Di Giacomo, at present a post-operative impression appears to be always necessary for immediate loading with a definitive pros- thesis.3 Guided implantology is far better than a free-hand approach, however. A guard- rail-likeguideiscertainlybetterthannothing. Many systems are available today, and from a theoretical perspective they have been categorisedintosemi-activeandpassivesystems.Thesystemsinthefirstcategory,what- ever the technique used to make the surgical guide (STL or stone surgery), have metal smoothguidingsleeves,whichtheimplantandtheimplant-drivermustpassthrough,and thesecondsystems,alsocallednavigationsystems,donothaveanymetalsleevesandthe surgeonisguidedbythemonitor.Inthiscategory,thesurgicalhandpieceisindexedtospa- tialmarkersinsideasurgicalguidethatisinsertedintothepatient’smouth,butnotinthe surgical area. These spatial coordinates are viewed by an infra-red system, which trans- fers data to the computer, allowing the clinician to follow the surgical steps on the mon- itor. Alarm lights and sounds will warn the clinician of deviations from the desired posi- tion. Iproposeanewdefinitionofapassivesystem:apassivesystemmustallowanyopera- tors(i.e.itmustbeoperatorindependent)toachievethesame,repeatableresultsatanac- ceptable inaccuracy threshold.4 The accepted inaccuracy must allow clinicians to obtain a goodmetal-to-metalfitwithoutplacingtensionontheimplants.This“towhatextent”pre- dictabilitycandeterminethereliabilityoftreatment.Infact,infixedprosthesesonnatural teeth,passivity(atanacceptablegap)isabout40to50µinthearch;thesamevaluescould beconsideredacceptableforprosthesesonimplants.Accordingtothisdefinition,noneof thesystemsonthemarkethasreplicableresults,andhavemetalorvirtualsmoothsleeves. Theymustthusbeconsideredmetalorvirtualsmoothsemi-activesystems. I have developed a new device according to the mathematical concepts of thread tim- ingandimplantphase,whichcanbeappliedtotheimplantmovementwhilebeingscrewed, thusallowingclinicianspassivityduringimplantplacement.Inthefuture,owingtothepre- dictability of implant placement, the proposed device could be fundamental to achieving thedesiredgoalsincomputer-guidedimplantology. _Materials and methods Theimplantswereplacedusingthebottle-neck-likedevice,whichbeginsimplantrota- tionbeforeitcantouchthebone,therebyavoidingboneinterferencewithimplantmove- ment owing to bone density gradients (“bone guidance”). The prototype of the device (Fig.1a)consistsof: –an internally threaded sleeve (“embedded sleeve”, with a “helical gear” feature at its top thatisusefulduringimplantplacement;Fig.1b); bionicstickygranules easy-graft® CRYSTAL Degradable Solutions AG Wagistrasse 23 CH-8952 Schlieren Phone: +41 43 433 62 60 www.degradable.ch dental@degradable.ch Ingenious: Simple handling and accelerated osteocon- duction for long-term volume preservation. Order your free test sample over the internet! AD