Bone atrophy is often encountered in the endentulous patient. With many clinicians performing bone grafting and augmentation techniques, there appears to be a decreased use of the subperiosteal implant modality for prosthetic stabilization. In recent years, there seems to be a decreasing number of literature reports and fewer academic presentations about the subperiosteal implant technique. Additionally, the American Academy of Implant Dentistry deleted this requirement for fellowship in its bylaws at its 1999 annual meeting. The purpose of this paper is to present the success and complication rates of 22 hydroxyapatite-coated subperiosteal implants placed over a 10-year period. Correlations between arch type and full vs unilateral subperiosteal implant cases are analyzed.

ORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemANALYSIS OF HA-COATED SUBPERIOSTEALIMPLANTSRESEARCHJohn C. Minichetti, DMDKEY WORDSHydroxyapatiteSubperiosteal implantCT scanningBone impressionJohn C. Minichetti, DMD, is an attendingdentist at the Englewood Hospital, Englewood,NJ, as well as in private practice. Addresscorrespondence to Dr Minichetti at 370 GrandAvenue, Englewood, NJ 07631 (e-mail:dminichett@aol.com).modality of choice. The subperiostealimplant technique is not recommendedas frequently as it once was.The subperiosteal implant was designedto rest on top of the bone andbeneath the periosteum. Its design wascreated to distribute stress from theprosthesis to large areas of supportingbone. Retention is obtained by the mucoperiosteum;when it becomes reattached,it stabilizes the infrastructurecasting.Gustav Dahl proposed the originalimplant design and insertion protocolin 1937.1(p431) Many clinicians modifiedthe technique and design of this im-Bone atrophy is often encountered in the endentulous patient. With manyclinicians performing bone grafting and augmentation techniques, there appearsto be a decreased use of the subperiosteal implant modality for prostheticstabilization. In recent years, there seems to be a decreasing number of literaturereports and fewer academic presentations about the subperiosteal implanttechnique. Additionally, the American Academy of Implant Dentistry deleted thisrequirement for fellowship in its bylaws at its 1999 annual meeting. The purposeof this paper is to present the success and complication rates of 22hydroxyapatite-coated subperiosteal implants placed over a 10-year period.Correlations between arch type and full vs unilateral subperiosteal implant casesare analyzed.I m esis rosth Th . s tul y e rwh e w n is y o plantoltagtion tecohniqovues, rootlminglform imthetureouusuallarchy usede pfor the fullyostendenfe e v o an r o r c r e c e a e n o ding e unadvdenrstant, developmenf bot, andugmbettenr-ostealompletimaplanth suppois fabrt ficated tordofreferri- over the past decade. With the Godberg in 1948.1(p432) The full subpef rsh Ge y b o u introd te af a adv n r g mendoImplantNTRODUCTIONusdentistryowth ahad sseenntrecesplant,r itsprimarilyctiinn the UnitedoStaf ates,nnd--orim 29_304 Mp_111File # 04emquently used with a full subperiostealis the RP-4 (a removable implant-supportedprosthesis).1(p429) The unilateralsubperiosteal implant is usually employedas the distal abutment for afixed prosthesis such as an FP-2 orFP-3. An FP-2 is a fixed prosthesis withtooth and root structure, and an FP-3is a fixed prosthesis with tooth, root,and soft tissue structure.2HA coatingSubperiosteal implants have been fabricatedfrom chrome cobalt alloy since1940.1(p433) Coating of the subperiostealJournal of Oral Implantology 111tics with HA-coated subperiosteal implantsusing both the direct bone impressiontechnique and CT-generatedsubperiosteal implants. In 1991, Kay,Golec, and Riley4 reported 4 years ofclinical experience with HA-coatedsubperiosteal implants. Their findingsshowed an overall success rate of98.2% in over 300 cases using the boneimpression technique and CT scan-fabricated subperiosteal implants. Thesame year, Misch and Dietsh publishedtheir results on 24 unilateral HA-coatedsubperiosteal implants. Their findingsreported an impressive successrate of 100% over a 10-year period.5 In1992, Benjamin presented a 6-year retrospectivestudy on over 700 CT-scan,HA-coated subperiosteal implants, reportinga success rate of 98%. Heshowed a ,10% complication rate inhis report.7A more recent publication in 1997by O'Roark reported success rates of85-100% on 362 subperiosteal implantsover a 6-10-year period.11 The consensusreport of the American Academy ofImplant Dentistry (AAID) presentedby clinicians Weiss, Linkow, Clark, andNathan concluded that both maxillaryand mandible, full and unilateral, HAcoatedsubperiosteal implants were viableand recommended techniques forboth fixed and removable prostheses.12Mandibular unilateral subperiostealimplantsLess than 10 mm of vertical boneheight often precludes the use of endosseousroot form implants withoutvertical augmentation (Division Cbone). Division C bone is an endentulousarea, which exhibits either ,2.5mm in width, ,10 mm in height, acrown-implant ratio $1, and/or an angulation.30 degrees, regardless of theposition of the implant body into theendentulous site.13 Therefore, the primaryindication for a unilateral subperiostealimplant is a partially endentulousKennedy Class II patient, missingall posterior teeth on one side, withORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemHA-COATED SUBPERIOSTEAL IMPLANTS10 YEARSimplant with hydroxyapatite (HA) wasintroduced by Rivera in the 1980s toimprove the likelihood of direct bonecontact to the implant.3 The use of HAcoating provided a stimulus for thereinterest in the placement of the subperiostealimplant in the late 1980s andearly 1990s. Several authors reporteddata on the use of HA-coated implantsduring that time period.4-7 The use ofHA coating with implants is recommendedbecause it has been observedand reported to improve the chance ofdirect bone-to-implant interface, to decreasestrut dehiscence, and to improvethe soft tissue environment.8Subperiosteal fabricationThere are two main techniques for fabricatingthe subperiosteal implant. Adirect bone impression technique is theoriginal method employed. It involvesa 2-stage surgical maneuver. On thefirst surgical visit, a bone impressionand bite registration is taken, usuallywith a polyvinyl siloxane material. Abone model is made in dental stoneand mounted at the proper vertical dimensionfor the subperiosteal implantfabrication. After the implant is cast, asecond surgical visit is required for itsinsertion. The first and second surgicalvisits are usually separated by a 6-week period to allow for periosteal reattachment.1(p441)In 1985, Truitt developed a computerizedtomography (CT) scanningtechnique.9 This method enabled theclinician to obtain a bone model usingCT and a computer-generated model(CAD/CAM), or sterolithography,thereby eliminating the first-stage surgery.The CT scan is performed on thepatient prior to any surgical visit. Thebone model is mounted using a biteregistration or the buccal tube and stylustechnique as described by Cranin.10One surgical visit is needed to insertsubperiosteal implants fabricated withthis technique.LITERATURE REPORTSIn the late 1980s and early 1990s, severalauthors reported favorable statis-112 Vol. XXIX/No. Three/2003METHODSorim 29_304 Mp_112File # 04emDivision C bone.1(p444) A Kennedy ClassII patient has a unilateral endentulousarea located posterior to the remainingnatural teeth.14 Bone atrophy and resorptionof the ridge often follow thelack of posterior teeth in the mandibulararch, particularly if a removablepartial denture has been worn over extendedperiods.The unilateral subperiosteal implantcan be fabricated from a bone impressionor with a CT-generated model.For the bone impression, an incisionis made over the crest of the ridge witha vertically ascending ramus-releasingincision. It is also recommended thatan anterior releasing incision be usedto allow for adequate ridge exposure.1(p445) A full-thickness periostealflap is made in order to expose the underlyingresidual ridge and lateral aspectsof the mandible. After the impressionis made, a bone bite registrationis necessary for mounting the bonemodel and achieving accurate locationfor the planned fixed prosthesis abutments.Primary closure with 3-O silkor chromic gut sutures is common.The direct bone impression isboxed and poured with die stone, andthe framework is designed. The gingivalcollar areas and the abutments arethe only polished surfaces. The implantis cast in chrome-cobalt-molybdenumalloy and coated with HA. Implantplacement is performed at least 6weeks after the bone impression to allowfor the healing of the periosteum.16The surgical incision is the same as instage I surgery. Adequate reflection isnecessary in order to confirm the properseating of the periosteal. Stability ofthe implant is observed, and the connectionof the infrastructure to the underlyingbone is confirmed. Any minordiscrepancies between the implant andunderlying bone are filled with particulateHA.1(p441) A tension-free primaryclosure is made, and a provisionalacrylic temporary prosthesis is constructedwith light occlusal contacts.The patient is given postoperative instructions,appropriate antibiotics, andanalgesics. Sutures are removed 1 to 2orim 29_304 Mp_113File # 04emJohn C. Minichettiweeks postoperatively, and final prostheticconstruction is begun 6 to 8weeks later. Postoperative complicationsare few, and can include temporarytooth sensitivity, incision line dehiscence,swelling, pain, and buccinatormuscle pull.The final prosthesis in this serieswas an FP-2 (fixed prosthesis withtooth and root structure) porcelainfused-to-high noble metal restorationconnecting 2 abutments of the subperiostealimplant to the anterior teeth(Figure 1). Small buccal/lingual occlusaltables of premolar width were usedto minimize lateral forces on the implant.Adequate embrasure spaces forsufficient oral hygiene were emphasized(Figure 2).Full maxillary subperiosteal implantThe maxillary full subperiosteal implantsin this study were fabricatedwith a direct bone impression or theCT scan technique. The surgical procedurefor the bone impression techniquewas similar to that described forthe unilateral implant. In several atrophicmaxillae, the CT scan techniquewas invaluable because dehiscent sinuseswere often encountered. The implantswere designed with the infrastructuresupported by the zygomaticarch, nasal spine, and midpalatine suture,thereby circumventing the maxillarysinuses and nasal floors (Figure 3).STUDY CASESRecords of 22 subperiosteal implantsplaced over an 11-year periodwere reviewed. Patients were categorizedinto age, sex, date of placement,complications, full or unilateral subperiostealimplant, CT scan-generatedconstruction, arch type, current status,opposing dentition, months in function,and whether splinted to naturalteeth (Table 1). Time of implant in situORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemFIGURE 1. Two distal abutments of the subperiosteal implant will be splinted to the anteriorimplant abutment. Abutment posts are tapered for conventional cementable fixed porcelainfused to metal prosthesis fabrication.FIGURE 2. Inserting a 3-unit fixed bridge creates an implant-independent prosthesis.FIGURE 3. Full palatal reflection allows for placement of a subperiosteal implant from acomputerized tomography scan and computer-generated model. Note the intimacy of fitof the subperiosteal implant. Defects in thebone are augmented with guided tissue regeneration(GTR) membranes and allogenicbone grafts.Journal of Oral Implantology 113*B indicates bone grafting; Comp, complication; CT, fabricated with the use of a computer-generated model; Curr, curettage and irrigation;F, full subperiosteal implant; Hyp, removal of hyperplastic tissue; Mand, mandibular; Max, maxillary; N, no; Sect, sectioning of strut; U,orim 29_304 Mp_114File # 04emMonths Splinted Opposing JawNNNNYY14412010410487108Root FormsRoot FormsSubperiostealSubperostealNaturalNaturalYYNNNY10810593938888NYYNYY888547717169NYY685151Y 46Four subperiosteal implants requiredcurettage and irrigation around theabutment posts. One full subperiostealimplant required surgical removal ofhyperplastic tissue. Four implants requiredflap surgery and bone augmentationof osseous defects that developedbeneath the permucosal abutmentareas. Four implants (2 of whichfailed) required sectioning of one ormore of the peripheral struts becauseof significant bone resorption in combinationwith bone grafting. Whengrafting was performed, it consisted ofHA and demineralized freeze-driedbone allograft (DFDB) mixtures withor without strut removal.The complication rates of fullsubperiosteal implants comparedwith unilateral implants were 29% to41%. A 100% success rate was foundfor the 4 CT-generated implants (Figure6). There was a 33% complicationrate in the maxillary arch (of 12 implants,4 needed treatment) and a40% complication rate in the mandibulararch (of 10 implants, 4 neededtreatment).ORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemHA-COATED SUBPERIOSTEAL IMPLANTS10 YEARSPatient12345678910111213141516171819202122unilateral subperiosteal implant; Y, yes.ranged from 46 to 144 months (4 to 12years) with a mean range of 86 months(7 years). The ages of patients treatedranged from 39 to 81 years. The meanaverage age of patients treated was60.8 years. Seven of the implants wereof the full arch design and 15 were unilateral.Twelve had been placed in themaxilla and 10 in the mandible. Fourof the implants had been constructedwith the CT scan technique, and 18 hadbeen cast from a bone model impression.All 22 subperiosteal implantswere restored with either a Misch/Judy classification FP-2 (fixed prosthesisreplacing tooth and root structure)or FP-3 (fixed prosthesis with tooth,root, and soft tissue) fixed-implantprosthesis.2A successful implant was classified asany subperiosteal implant remainingin occlusal function over the study period.A failure was any implant thathad to be totally removed because ofpain, swelling, infection, or significantbone loss. A subperiosteal implant wasclassified with a complication when-114 Vol. XXIX/No. Three/2003Date Placed Sex AgeFFFFMF7664545466517/28/9310/22/9310/28/9410/28/943/14/953/22/95FMFFFM5168555577873/28/956/22/954/13/968/1/968/8/9610/21/96FMFMMF77656660805711/29/966/20/976/20/97MFF56404011/21/97 M 39RESULTSStatistical data10 years*CompY/Sect/BNY/HypNY/Sect/B7/25/907/22/924/21/934/21/934/26/937/28/93 NNY/Sect/BNNNNY/CurrNY/Sect/BY/CurrY/CurrNNNNNever treatment or intervention was necessary,such as curettage and irrigationof abutment posts or struts, surgicalpocket elimination, bone grafting, orrevisional sectioning of any portion ofthe subperiosteal struts.Of the 22 subperiosteal implants, 2required complete removal, for anoverall success rate of 91% (Figure 4).Analysis of the 12 maxillary subperiostealimplants indicated a 100% successrate. The longest implant in functionwas in place for 12 years. In themandibular arch, there was an 80%success rate, with 2 mandibular unilateralsubperiosteal implants removed(Figure 5). Comparison of full subperiostealimplants to unilateral subperiostealimplants showed a 100% successrate for full subperiosteal implants andan 87% success rate for unilateral implants.Complication rates for the subperiostealimplants were higher than successrates. An overall complication rateof 36% was noted. This complicationrate includes the 2 failed implants and6 implants that required some type oftreatment, with or without surgery.TABLEPresent Jaw TypeFirmFirmFirmFirmFailedFirmMaxMaxMandMaxMandMandFFFFUU/CTFirmFirmFirmFirmFirmFirmMandMaxMaxMaxMaxMaxU/CTUUUFUFirmFirmFailedFirmFirmFirmMaxMaxMandMandMaxMandF/CTUUUUUFirmFirmFirmMaxMandMandF/CTUUFirm Mand UNaturalNaturalRoot FormsRoot FormsRoot FormsRoot FormsBladesRoot FormsNaturalNaturalNaturalNaturalOverdentureNaturalNaturalNaturalORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemDISCUSSIONAll of the patients in this study hadsignificant bone atrophy that wouldhave required bone grafting proceduresprior to placement of root formimplants. Therefore, subperiosteal implantswere chosen. The subperiostealimplant offers the advantage of eliminatingbone augmentation prior to implantplacement. This can can reducetreatment time significantly; when CTscanning is used, the implant can beplaced and restored within a fewweeks. This is particularly beneficialfor elderly patients. The subperiostealimplant is often more cost effectivethan traditional root form implants.Disadvantages of the subperiostealtechnique include larger surgical flapelevation and management. Postoperativeswelling and edema are common.The placement technique is more demandingthan that of conventional rootform implant placement.Failure rates in this report are similarto those reported by others.4-7 Theoverall complication rate of 36% reportedin this analysis is higher thanthose reported by others. This could bea result of the definition of complicationin this report, which ranges fromminor curettage to surgical intervention.The complication rate for HAcoatedsubperiosteal implants in thisstudy might be one of the factors thatinfluences clinicians in their choice ofimplant modalities.CONCLUSIONof bone regenerative technology in thepast decade facilitating the use of rootform endosseous implants might beThe purpose of this paper was to presentthe results of 22 subperiosteal implantsplaced over a 10-year period. Anoverall success rate of 9% was similarto those found in previous reports,4-7but a complication rate of 36% washigher. In general, there appears to beless interest in the literature and continuingeducation courses with regardto subperiosteal implants. An explanationcould be that potential complicationsfor this technique are high, andclinicians might be challenged whentreating these problems. Proliferation another explanation.orim 29_304 Mp_115File # 04emJohn C. MinichettiFIGURE 4. Chart demonstrating an overall success rate of 91% for a total of 22 subperiostealimplants.FIGURE 5. Chart comparing the overall success rate of maxillary vs mandibular arch subperiostealimplants.FIGURE 6. Chart comparing the success rates of the computerized tomography scanning vsbone impression technique for fabrication of the subperiosteal implant.ACKNOWLEDGMENTSThe author acknowledges CreativeCustom Service laboratory and A CJournal of Oral Implantology 115ORAL IMPLANTOLOGYFriday Apr 25 2003 01:50 PMAllen Press x DTPro SystemHA-COATED SUBPERIOSTEAL IMPLANTS10 YEARSlaboratory for their assistance withthese cases, as well as Lauren Minichettifor her assistance with the statisticaldata and graphs.REFERENCES1. Misch CE. Contemporary ImplantDentistry. 2nd ed. St. Louis, Mo: Mosby;1999.2. Misch CE. Bone classification:training keys. Dent Today. 1989;8:39-44.3. Rivera E. HA castings on thesubperiosteal implant. InternationalCongress of Oral Implantology, SanJuan, Puerto Rico, 1983.4. Kay JK, Golec TS, Riley RL. Hydroxylapatitecoated subperiostealdental implants status and four yearclinical experience. J Oral Implantol.1991;8:11-16.5. Misch CE, Dietsh F. The unilateralmandibular subperiosteal im-116 Vol. XXIX/No. Three/2003plantindications and technique. JOral Implantol. 1991;8:21-27.6. Golec TS, Krauser JT. Long-termretrospective studies on hydroxyapatitecoated endosteal and subperiostealimplants. Dent Clin North Am. 1992;36:39-65.7. Benjamin L. Long-term retrospectivestudies on the CT scan CAT/CAD one stage surgery hydroxypatitecoatedsubperiosteal implants, includinghuman functional retrievals. DentClin North Am. 1992;36:77-93.8. Han J. The unilateral subperiostealimplant. Int J Oral Implantol. 1991;8:136-145.9. Truitt HP. Noninvasive techniquefor mandibular subperiostealimplant: a preliminary report. J ProsthetDent. 1986;55:494-500.10. Cranin N, Klein M, Sirakian A.Tech for mounting computer generatedorim 29_304 Mp_116File # 04emmodels for subperiosteal implants: theBrookdale tube and stylus centric system.J Oral Implantol. 1993;16:52-56.11. O'Roark W. Survival rate ofdental implants: an individual practitioner'sanecdotal review of 25 years ofexperience. J Oral Implantol. 1994;20:43-47.12. Weiss CM, Reynolds T. A collectiveconference on the utilization ofsubperiosteal implants in implant dentistry.J Oral Implantol. 2000;26:127-128.13. Misch CE, Judy KWM. Classi-fication of partially endentulous archesfor implant dentistry. Int J Oral Implantol.1990;7:9-17.14. Baker JL, Goodkind RJ. Theoryand Practice of Precision Attachment of RemovablePartial Dentures. St Louis, Mo:Mosby; 1981.15. Cranin AN. An Atlas to Oral Implantology.1st ed. New York, NY: ThiemeMedical Publishers; 1993.