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I 15 special _ endo-implant algorithm I roots2_2010 microflora leakage and colonisation at and within the FAI are some of the pathological vectors associated with osseous remodelling, both crestal and peripheral to dental implants.48 Occlusal considerations engi- neered into fixture design should enable optimum load distribution for permanent load stability during functionalloading,reducefunctionalstresstransferto the interfacial tissues, and enhance the biological reaction of interfacial tissues to occlusally generated stress transfer conditions.49 Future modifications to implant biomechanics should focus on designs whereintheosseoustrabecularframeworkthatretains the fixture will adapt to the amount and direction of applied mechanical forces, cope with off-axis load- ing, compensate for differences in occlusal plane to implant height ratios, as well as adjust to mandibular flexionandtorsion.50 Inthisneweraofimplant-driven treatment planning, fixtures should be engineered to support single crowns with cantilevers instead of implant–implant or implant–teeth connections for a spanofanydegree.Theseengineeringdesigniterations will minimise high-stress torque load at the implant- abutment interface and obviate areas with degrees of bone insufficiency. The goal should be to biomimeti- cally replicate the natural state to the greatest degree withregardtoloadbearingcapacity(Figs.10a&b). Stable crestal bone levels are the yardstick by which treatment success and health are measured in the orofacial ecosystem, whether success and health relate to natural tooth retention or restorative and/or replacement rehabilitation. It is therefore surprising that the treatment outcome standards for osseointe- grationacceptcrestalboneremodellingandresorption of up to 1.5 to 2mm in the first year following fixture placementandprostheticinsertion.51 The concept of biologicalwidthoutlines the mini- mum soft-tissue dimension that is physiologically necessary to protect and separate the osseous crest fromahealthygingivalmarginsurroundingteethand the peri-implant environment. A bacteria-proof seal, thelackofmicro-movementassociatedwithafriction grip interface and a minimally invasive second-stage surgery(whereindicated)withoutanymajortraumato the periosteal tissues are also important factors in preventing cervical bone loss. The literature suggests that the stability of the implant-abutment interface mayhaveanimportantinitialroletoplayindetermin- ing crestal bone levels.52 Tarnow’s seminal study on crestal bone height support for the interdental papil- lae clearly demonstrated the influence of the bony crest on the presence or absence of papillae between implants and adjacent teeth.53 Twenty years later, logic dictates that anticipated early crestal bone loss and diminished, albeit continual, loss in successive years of function ought to have been engineered out ofthesubstitutionalgorithmforperi-implanttissues.54 _Platformswitching:Bydefaultorbydesign There is no logical way to the discovery of elemental laws.Thereisonlythewayofintuition,whichishelped byafeelingfortheorderlyingbehindtheappearance. —AlbertEinstein Platformswitchingtheorisesthatbyusinganabut- mentdiameterofalesserdimensionthantheperiphery of the implant fixture, horizontal relocation of the im- plant-abutment connection will reduce remodelling andresorptionofcrestalboneafterinsertionandload- ing. The concept implies that peri-implant hard tissue stability will engender soft tissue and papilla preser- vation. Maeda et al. reported that stress levels in the cervical bone area peripheral to a fixture were greatly reduced when a narrow diameter abutment was connected,incomparisontoasizecommensuratewith the fixture diameter.55 The authors concluded that the biomechanical advantage of shifting stress concen- trationsawayfromthecervicalareawilldiminishtheir impact on the biological dimension of hard and soft tissueextendingapicallyfromtheFAI(Figs.11a–c).The inherent disadvantage is that this shifts stress to the abutment screw with the potential for loosening or fracture. Ericsson et al. 56 detected neutrophilic infiltrate in the connective tissue zone at the implant-abutment interface. The facility by which platform switching/ shifting reduces bone loss around implants has been investigated by Lazzara et al.57 The authors hypothe- sisedthatiftheabutmentdiametermatchesthatofthe implant,theinflammatorycellinfiltratewillbeformed intheconnectivetissueatthemicro-gapcreatedatthe FAI.Ifanabutmentofnarrowerdiameterisconnected toawiderneckimplant,theFAIisshiftedawayfromthe Fig. 12a_The platform-switched design negates micro-motion and resultant crestal bone resorption. The goal of ortho-biological replacement is the idealised replication of the natural state. Fig. 12a