CLINICAL CONSIDERATIONS OF DENTAL IMPLANT SYSTEM IN IMMEDIATE LOADING IMPLANT CASES

Immediate loading ofdental implant has been researched intensively in the development ofBnnemark's early concept of 2 stages implan. plac€m€nt. This was embarked from both patients and practitioners.' convenienc€ towards a simpler protocol and shorter time fiame. Many recent researches lat€r found that micromotions derived from occlusal loading for a cenain degree, instead of resulting a fibrous tissue encapsulaiion, can enhance the osseointegation process, Dental Implant syslem enhancement towards maximizing the primary stability held a key factor in Branemark's concept development. Surgical protocol and implant design was found to give a significant coniribution to the prognosis of immedialeloading implants. IndonesianJournal ofDentktry 2006; E.lisi Khll:us KPPIKC XIV 338-342.


Introduction Dental implant has b€en widely considered as a predicrable rehabillaron
Lreatnenr since osseointegration concept was introduced by Dr. IV Branemark et al in 1977.His 2-stage implant placement protocol €omp ses 4'6 months nonloading time frame which.became a prerequisite in Dental Implant treatments.' Th€ rational€ for such a delay is that premature loading may lead to fibrous tissue encapsulation instead of direct bone apposition.Funhermore, necrotic bone which is derived liom surgical trauma at tbe implant bed bordef is not capable of load-b€aring and must be first replaced by a new bone.'Rapid remodeling of dead bone layer compromises the strength of orseous fis\ue supponinS lhe bone-implanr sire which leads to implant failure.How€ver, 80 % of th€ir patients have advanced bone resorption, l0o/" wirh exlfeme r€sorption.and the remaining l0% modemte resorption, All patienls have poor bon€ quality offering unfavorable conditions for the mechanical retention of fixation which provides primary srability.raThese limitations accounted for rhe need ro delay loadrng for \uch a longpenod.
Larcr studies were then carried out to shoten th€ non loading tine period through production of new implant d€signs, development of new te€hnique, and implementation of recently gained knowledge.Based on the iheory that mechanical stimulation under bone physioloSical tkeshold can have a profound effect on diff€rentiation and development of mes€nchymal tissu€, immediare loading was then vastly studied.The histological study by Piat€Ui showed that 60-70 % bone irnplant contact with immediate loading had no fibrous encapsularion which confirmed the above theory.Ledermann utilized Titanium Plasma Sprayed l?S) endosteal scr€w implants (Straumann -5arrute.Waldenburg, Switzerland) in antedor :$dibie to stabilize ov€rdentures.The protocol ::rlled for 3-4 rough self-tapped implants, long -ough to get bicortical anchorage, which was r:-mediately splinted and loaded on the same day.;ri up to 81 months follow up report showed 91.2% li{cess rate based on 476 implants placed in 138 :arenis, 8l % ofthe failures occuned during the first ,idr.failures were related ro the lack of primar) ilbility, lack of at least I I mm of available bone, _L(rdl and lingual perforafion.loo earl) insertion in i., extraction socket, and insuffrcient hygiene.rLedermann's study brought a significant :hange in implant treatment perspective.Babbush et rl replicated the Ledermann protocol on implant :e6ined overdentures in 129 patients rehabilitated qirh 5i4 implants.Four TPS implants were placed n $e inierforaminal area of mandible and splinred $rthin 2-3 days by the mean of a dolder bar and loaded.The 5 years follow up showed 96.1% iuccess rat€.All failures occuffed during the first \ear.whereas 80% happen€d during the first 6 ronths.Failures were related to delayed sptinting and perforation ofthe inferior border whh secondary Chiapasco et al. conducted a multicenter study on the similar protocol as Lederman's.The study incorporated 194 patienrs with 4 differenr systensl TPS and ITI screw implants (Shaumann Institure, Waldenburg, Switzerland), NLS scr€rv implants (Friatec, Mannheim, cermany) and Ha-Ti screw implants (Mathys Dental Implants, Betrlach, Switzerland).Immediately afte' the imptants placement, a U-shaped gold bar was fabri€ared and implants were immediately loaded with an overdenture.The study was monirored from a minimum of2 years to a maximum of 13 years, with a mean follow up of 6.4 years.The overalt succ€ss Iate was 96.9%, whereas the failure rate ofba^ was 1.5 %.No statisticaliy significant diflerence was found between differenr impldnr sysrems.atrnougr performed in 4 differenr centers.''Cu(ent researches using diff€rent denral implant systems showed similar results.Lorenzoni et al. reported 100% success rate on their 6 month study on Frialir-2 implants.The implants were placed in interforaminal region located at positions 34, 33, 32, 42, 43, and 44.In oroer ro obtain an in-patient comparison of immediar€ loading and nonloading implants, the ones at 33 and 43 were chosen to be immediately loaded by a dolder-bar retained overdenture.A high intimat€ bone apposition was seen in the imnediate loading implants although with a lower coronal bone level and clinical stability.'"Siddiqui et al. also found a good r€sult in imnediate loading €ases with Advent Screw dental implanls (Zimmmer, cermany).Th€ system carne with an iniraosseous body, selflapping, triple-lead threads and a combination of IlA-coated and blasted surface.r?
Another study on immediare loading implant in anterior mandible region was conducted by Steenberghe et al., using Branemark Nowm protocol (llobel Biocar€, corhenburg.Sweden) in 50 patients.The protocol €all€d for 3 implants inserted in the symphyseal area, connecied by a very rigid horse shoe-shaped ritanium bar.A final screw retajned prosthetic ftamewcrk was placed on top of it immediately or within 2 days after surgery.Ttrey found 92.7% success rate on 12 months follow up study, which is low€r than the expected rate crireria proposed by Albrektsson and Sennerby (95%).reDImmediate loadiog protocol bas also been studied for fixed prosthetic rehabilitations, one or shich uas a j )ears srudy conducred by te'lori er al. Theh study was canied our in 62 patients using the lotal of 325 dual acid-erched cylindrical screw shaped Ossotite implnrs (31, West Palm Beach, FL, USA).Five to six inplants were inserted in rhe inlerfordmrnal drea of mandible $ irh l0 ro l8 mrn rn length and 3.75 to 6 mm in diam€ter uiilizing a 32 Nrn torque.Hybrid prostheses were then delivered within 48 hours of implant placement.During the follow up, two implants were lost within the first 2 months which was related to poor bone quality, leaving a 99.4% success rate.'

Discussion
The basic principle of imm€diate loading implant protocol is primary stability, wh;cb depends on two facbrs, host (bone), aod extemal factor Gurgical proc€dure, implant design, and surface trcaanen0, It has be€n recommended 10 perform immediate procedure jn dense homologous bone, which can be generally found in the anterior part of the mandible.The co(ical lamellar bone may heal $irh lirlle inlerim wo\en bone formation.ensuring good bone strength whil€ healing next to an endost€al implant.lts fine porosity (<10%) favors better rn€chanical interlocking compared to soft can€ellous bone that has 80-95% porosity, which subsequently provides a better stability to withhold any forc€ from immediate loading in maximizing tbe physioiogical threshold to accommodate the osseoinregration proce.s.tt'-On rhe conrrar).rhe Iack ofinitial stabilitv in wDe 4 bone results in ;o*cr success rates, varying fro; 50% to 94%,' 3r? which $as also found b) Testory.Bischol.and fricsson rn then studies.
Alnost all ofthe studies on immediate loading implants recommended the us€ of screw thrcaded implant" $hich nol onl) minimi/e rhe micromotion ofthe implanr due to the increasing surface ar€a, bui also to improve initial stabilily.With a proper surgical procedure, the implanr threads ensure the initial interlocking which is essential in immediate Ioading cases.
Anoth€r implant design related factor is ihe implant length.The b€nefit of increased Iength is needed in providing vertical relention to suppod initial srability ofthe bone-implani interface.This is more crucial in immediale loading cases since in the early phase of function, dental inplant must withsrand the for€es by itself prior to bone-implant integration.Additionally it is also benefits from the increasing of surface area as con€luded by Misch that for ev€ry 3 mm increase in length, the surface area of a cylinder-shaped implant increases by an average of2o-30%.3114 Implant diameler, lhough critical lo withstand the occlusion for€e concentrated at the crestal bone, does not condbule as much in initial srability The main benefit of using wide diamet€r implanr is rhe increasing 'urface area as each 0.2) mm increa'e in diameter 'mproves tunctional area support to more than 5-10 %." Surface treatment ha5 been proven to improve initial stability and bone healing process.'u" tt benefils iom both ihe rough implant surface and the osteoconductive media given on the surface.An appropriate micro-.oughenedsurface is proven to engage and hold the fibrin strands which are formed during rhe inirial cloning proce.' followjng lhe inse(ion of implant fixtures.The stabilizaiion oftbe initial clot is mandatory as the fibrin strands form a bridge for th€ migraiion of osteoblastic cells iiom the surrounding osteotomy onto the implant surface.Favorable surface characterisiic have also be€n sbown to aid the absorprion of proteins, accumulate and activate plat€l€is in providing plat€let derived growth facrors, thus promoting angiogenesis, and b differentiate progenitor cells into mature In principle, there are 2 kinds of surface r:ro.nr: additir/e and redu€tive swfac€-lmPlants .E Tianium Plasma Sprayed (TPS) and HA ;-'eg iall inlo tle 6rst cal€gor) Pure Tihnium :r'Nle which is qrrayed through a plasma flame at ll tm'C is shown to increase the surface area by 6-1: :Des by the apposition of a porous layer 20-50 --:ln dick.On the other halld IIA coating has been rilen ro accelemt€ osseointegration TPS implants t€ snll widely us€d for immediate loading cases =.e they showed a !€ry high success mle.The =am concem for boih surface treatment is the .trrualdelachmenl with subsequ€nt periimplantitrs r:d$ed n some srudies with HA coaling."'"_' Reductive surface aeatm€nt is the development :: dre two surfaces discussed to minimiz€ the risk of ii.i'ace detachment, The micro-roughening process :i Ihe titanium implant sudace is done by electro_ \.iishing, acid-etching, titanium oxide blasting and :larr€tching nethod.39.40Studies on implants w,th r::Jucriv€ surface showed a high success rate, thougn i.esn t differ significantly with the additive surgrcal protocol plays an imponanl role since renral implant proc€dure is technique sensjtive ?roper surgical protocoi in an implant system should rclude adequate cooling to avoid the heat generated juring bone drilling.lt is reconmended to keep the :emperarure belo\ 47'C to avoid bone necrosis.rhlch could detriment lhe osseointegration process :bllowing a good primary stability This can be achieved by increasing the speed and torque together :o allow a more efficient cutting with no significant :ncrease in temperature,3r A proper orientation of osteotome instruments r!1 create an undersized preparation of imPlant site prior to placement is also essential in immediate loading cases.Shallabi proposed the lheory iupporting this protocol that a lot of small bon€ iagments are created and pressed in between the rabecular voids and between the screw threads Juring implant installation, hence ensuring a good o|man sLabiirty and rnducing nell bone Conclusion Defial implant systems used in immediate loading cases must have the propenies that support maximum primary stability.This is to ensure that micromotion can be controlled under physiological thrcshold to induce a mechanical stimulation on mesenchym tissue.The properties must include screw thread€d cylindrical implants, with maximum length and diameter, adequat€ surface treatment, atmumatic and undersized implant bed pr€paration.