1548-1336(2004)30_134_APICBL_2.0

AICRG, PART II: CRESTAL BONE LOSSASSOCIATED WITH THE ANKYLOS IMPLANT:LOADING TO 36 MONTHS

Cherng-Tzeh Chou, DDSHarold F. Morris, DDS, MSShigeru Ochi, PhDLori Walker, DDSDeborah DesRosiers, DDS, MS

KEY WORDS

Dental implantsEndosseous implantsOsseointegrationImplant designClinical studies

Cherng-Tzeh Chou, DDS, is a clinicalinstructor in the School of Dentistry, TaipeiMedical University, Taipei, Taiwan.

Harold F. Morris, DDS, MS, is codirectorof the Dental Clinical Research Center(DCRC) and project codirector of theAnkylos Implant Clinical Research Group(AICRG), Department of Veterans AffairsMedical Center (VAMC), Ann Arbor,Mich. Correspondence should be addressedto Dr Morris at the DCRC (154), VAMedical Center, 2215 Fuller Road, AnnArbor, MI 48105.

Shigeru Ochi, PhD, is codirector of theDCRC and project codirector of theAICRG, VAMC, Ann Arbor, Mich.

Lori Walker, DDS, is a staff dentist at theVAMC, Sepulveda, Calif.

DeborahDesRosiers, DDS,MS, is a staffdentist at the VAMC, Ann Arbor, Mich.

Problem: The Ankylos endosseous dental implant is a new implant

design that will be available in the United States in early 2004. It

features an internal tapered abutment connection, a smooth polished

collar without threads at the coronal part of the implant body, and

a roughened surface with variable threads on the body of the

implant fixture. A precise, tapered, conical abutment connection

eliminates the microgap often found in 2-stage implant systems.

This microgap may allow the accumulation of food debris and

bacteria, as well as micromovement between the parts during

clinical function, both of which can lead to a localized inflammation

and crestal bone loss. Purpose: The purpose of this section of the

study was to assess any crestal bone loss associated with this new

implant. Method: The clinical performance of this new implant

design was studied under well-controlled clinical conditions. Over

1500 implants were placed and restored. The vertical crestal bone

loss was measured ‘‘directly’’ between the time of implant

placement and uncovering, using a periodontal probe. Serial dental

radiographs were taken between loading, and the 12-, 24-, and 36-

month follow-up visits to determine ‘‘indirect’’ crestal bone loss

within a specific period. Results: Bone loss varied among the

participating centers from less than 0.5 mm to 2.0 mm. The largest

amount of bone loss occurred between the time of placement and

uncovering. Following loading, the mean bone loss for all implants

for a period of 3 years was about 0.2 mm/y. Conclusions: The

extent of the crestal bone loss after loading was minimal for patients

regardless of age, gender, prosthetic applications, bone density, and

remote or crestal incisions, as well as for smokers or nonsmokers.

Bone loss per year is well within the guidelines of 0.2 mm/y

proposed by others.

134 Vol. XXX/No. Three/2004

SPECIAL REPORT

BACKGROUND

The United StatesNational Institutesof Health (NIH)/National Instituteof Dental ResearchConsensus Confer-

ence Development Statement1 in1988 stressed the need for long-term clinical studies to comparethe clinical performance of dif-ferent types of implants underconditions similar to those en-countered in the dental office.Stable bone levels are believedto be critical to the long-termsuccess of an implant becauseexcessive bone loss can lead to

peri-implantitis and the eventualloss of the implant. In view of thelack of extensive and creditablecrestal bone loss data during the1988 NIH Consensus Conference,it was suggested that futurestudies include longitudinalevaluation of radiographicchanges in the supporting bone.Dentistry has long been con-cerned about crestal bone loss,and the potential influence ofimplant design certainly warrantsadditional research. Dentistry iswithout an acceptable worldwideconsensus as to how to accuratelymeasure any changes in the crest-al bone and what, if any, lossrepresents acceptable limits.

Many clinical studies fail tomeasure crestal bone loss betweenplacement and abutment con-nection (ie, uncovering/abutmentconnection). Most information inthe literature includes data onlyfor the period from loading of theprosthesis to a specific follow-upperiod after loading. Bone loss hasbeen reported to range from 0.5mm to as high as 2 mmwithin thefirst year of implant placement.2,3

More recently, in 2002 Warren etal4 reported that crestal bone lossof between 1.0 and 1.5 mm mayoccur almost immediately aftersecond-stage surgery and implantloading. In view of the limiteddata from scientific clinical stud-ies, additional data are needed.The range of bone loss, fromimplant placement to 36 monthsfollowing restoration, can varywidely from 0.0 to 2.1 mm. Initialbreakdown of the implant-tissueinterface generally starts at thecrestal region of successfully in-tegrated implants for both 1-stageand 2-stage implants with about0.2mmof loss after the first year ofclinical function.5 The loss ofcrestal bone has also been re-ported to be influenced by thelocation of the implant/transmu-cosal abutment interface (ITAI)relative to its relationship to thecrestal bone.6 Scanning electronmicroscopic evaluation of failedimplants has demonstratedsignificant amounts of plaqueaccumulation at the ITAI, whichmay produce localized inflamma-tion and subsequent crestal boneloss. Cochran et al7 suggest thatthe crestal bone loss around im-plants may be attributed to thebiological width that is physiolog-ically formed at the abutment-implant connection.

In 1997, Herman et al8 studiedthe crestal bone loss in relation tothe location of the microgap thatexists between the implant fixtureand the abutment in 2-stage im-

FIGURE 1. (A) Method used to determine crestal bone loss from radiographs. The actualbone loss (a) is calculated from the proportion of measurements in millimeters; A ¼actual length of implant from records; r¼ length of implant on radiograph; a¼ actual(calculated) bone loss; r¼measured bone loss on radiograph. (B) Crestal bone loss ateach time period from loading to 12, 24, and 36 months. Average bone loss is about 0.2mm each year for the 36-month period that was well within the loss suggested fordetermining implant success. CBL indicates crestal bone loss on mesial or distal ofimplant; LI, length of implant.

Cherng-Tzeh Chou et al

Journal of Oral Implantology 135

plants. He reported that the bonedensity adjacent to the microgapappeared less dense than otherareas of bone and that the bonelevel was consistently found to belocated below this gap. Boneremodeling for 2-stage implantsgenerally occurs after abutmentconnection. It has been suggestedthat this change may be a re-sponse to the presence of themicrogap.9 More recent studiessuggest that the influence of themicrogap is dependent less on itssize than on the fact that move-ment occurs at the interface be-tween the implant fixture and theabutments of 2-stage implants.This movement may influencethe amount of crestal bone loss.10

The anatomy, physiology,histology, and embryology ofbone in the oral cavity have beendiscussed extensively.11-15 Therelationship of the biologicalproperties to crestal bone re-sponse, as related to dental im-plants, has been reported.16

Chiarenza17 discussed the differ-ences in the histology and boneresponse at the bone-implant in-terface, depending on the type ofbone present at the implant site.Albrektsson et al18 were amongthe first to propose criteria for theevaluation of dental implant suc-cess, which included the criterionof vertical bone loss. Their crite-rion suggested the loss should beless than 0.2 mm annually afterthe first year of the loading of thedental prosthesis. Similar criteriawere later proposed by Smithet al.19 Excessive crestal bone losscan be problematic for someimplant systems. One study20

evaluated 2 implant systems forsuccess using the crestal bone lossat less than 1.5 mm after 3 years offunction as the criterion for de-termining success and found thatonly 76% to 86% of the implantscould be rated as being ‘‘success-ful.’’ By changing the critical level

of bone loss to less than 3.5 mm,success of the implants increasedto between 93% and 100%.

Other methods for assessingcrestal bone responses have beenutilized throughout the evolu-tion of the endosseous implant.Schnitman and Shulman21 sug-gested criteria for implant successbe less than one third of theheight of the implant. Malmqvistand Sennerby22 reported thatvertical crestal bone loss may beas high as 2 mm and that someimplants have losses greater thanone third of the implant length.Different amounts of bone losshave been reported for variousimplant designs and surface char-acteristics.23 In spite of the lack ofconsensus, the values generallyaccepted as a reasonable guide-line for bone loss is less than1.5 mm for the first year post-loading of the prosthesis and lessthan 0.2 mm of additional loss foreach following year.18,19

Direct measurements of boneloss between the time of implantplacement and abutment connec-tion provides a means of deter-mining the amount of crestalbone loss during this criticalperiod. Although most likely theresult of surgical trauma, fewclinical studies attempt to deter-mine and report this information.This was, however, a critical focus

in the comprehensive, indepen-dent evaluation of this new im-plant. During the follow-upperiod, the most commonmethodof assessing crestal bone lossinvolves the use of serial radio-graphs. The X-ray tube reposi-tioned within 208 for allsubsequent radiographs is be-lieved to provide diagnostic ra-diographs.24 With natural teeth,the cemento-enamel junction(CEJ) is readily visible and thecrestal bone height is about 1 to1.5 mm below the CEJ. In the caseof dental implants, the CEJ is notpresent. Indices were developedfor use in large clinical studies tospeed up the measurement pro-cess for crestal bone responsesand to address the problems ofnonstandardized radiographs.25-27

In most studies, the indices havebeen abandoned in favor of othermethods such as subtraction radi-ography and simple proportionalmeasurements of serial radio-graphs.

The use of radiographs to de-termine crestal bone loss betweenimplant placement and uncover-ing using serial radiographs hasnot been widely used becauseof concerns that the radiationmight damage the ‘‘new matur-ing bone’’ during the healingprocess.28-30 Stenstrom et al31 cal-culated the volume of tissue

TABLE

Mean crestal bone losses for various periods of implant treatment

Time IntervalMean Crestal

Bone Loss (mm)Annual Increase inBone Loss (mm)

Placement to uncovering* 0.70* —Uncovering to loading* 0.81 0.11Loading to 12 mo 0.15 0.15Loading to 24 mo 0.48 0.24Loading to 36 mo 0.64 0.16Overall mean from

placement to 36 mo 0.60 0.20

*Indicates values determined by ‘‘direct measurement’’ at the time the tissue flapswere reflected to expose the bone-implant relationships. Measurements were from thetop of the implant to the top of the crestal bone. All other measurements weredetermined from serial radiographs. The boldface value was used as a baseline fromwhich future changes in crestal bone height were calculated.

AICRG. II. BONE LOSS ASSOCIATED WITH IMPLANT


exposed to secondary radiationoriginating from the 2 metalinterfaces of the threads andassessed the risk for the tissuecells during a radiograph. Boneimmediately in contact with themetal implants was estimated tobe exposed to secondary elec-trons. This exposure could easilydouble with an implant withthreads, as the 2 surfaces of thethreads would contribute to theamount of exposure.

SPECIFIC AIM

The specific aim of this paper is to(1) determine the crestal bone lossassociated with the Ankylos im-plant design (Friadent GmbH,Mannheim, Germany) betweenthe time of implant placementand uncovering using directmeasurements; (2) calculate thebone loss between uncoveringand loading, loading of the pros-

thesis and 12 months, loadingand 24 months, and loading and36 months using serial radio-graphs; and (3) to assess thepossible influence of other varia-bles such as jaw region, age ofpatient, the patient’s health sta-tus, smokers vs nonsmokers, bonequality, placement incision type,and uncovering incision type.

METHODS

The patients for this compre-hensive clinical evaluation of theAnkylos implant were recruitedfrom 30 VA medical centers, 2dental schools, and 2 foreigndental clinics. The study protocolwas reviewed and approved bythe research committees andinstitutional review boards at allcenters before the study wasactivated. Both the protocol andconsent forms included all infor-mation recommended in the US

Food and Drug Administration(FDA) Guidelines for clinical trials.Sample size was calculated for thestudy to enable meaningful statisti-cal analyses. A comprehensive op-erations manual, which containeddetailed information about all pro-cedures to be followed during thecourse of the study, was developedand provided to all participatingcenters. All clinical investigatorswere provided training and stan-dardization at a 2-daymeetingpriorto the start of the study. Trainingincluded patient screening (inclu-sion and exclusion criteria), surgicalprocedures to be followed for plac-ing theAnkylos implant, restorativeprocedures, and completion ofstudy forms. The procedures to befollowed in the event of failure of animplant, a complication, or seriousadverse event were also clearlydefined. Over 1500 implants wereplaced to support dental prostheses.The implant prostheses designs in-cluded maxillary (anterior) com-pletely edentulous cases, maxillaryposterior partially edentulous cases,mandibular (anterior) completelyedentulous cases, and mandibu-lar posterior partially edentulouscases. Single-tooth restorationswere placed in appropriate loca-tions depending on the clinicalneeds of the patient.

Bone loss data collection

The surgical instructions for theAnkylos implant recommend thata tissue punch be used for re-moving the soft tissue coveringthe implant to allow for theconnection of the tapered abut-ment. For this study, this step wasmodified to allow ‘‘direct boneloss’’ measurements between thetime of implant placement andabutment connection. Althougha conservative tissue flap wasused to obtain these measure-ments, it is possible that the tissueflap procedure may have in-

FIGURE 2. Clinical case photographs (courtesy of Dr Cherng-Tezh Chou, Taiwan,China). (A) Abutment connection; (B) clinical case, 4 years postloading (note health ofsoft tissue surrounding the implant restoration). (C) Radiograph of postloading to 24months (no apparent clinically significant crestal bone loss). (D) Radiograph ofpostloading to 48 months (no apparent clinically significant crestal bone loss).



creased the crestal bone lossreported in this section of thestudy. The direct measurementswere made in millimeters (mm)from the top of the implant to thetop of the crestal bone (Figure 1A)using periodontal probes with 1-mm divisions. All measurementswere made at the time of implantplacement and repeated at thetime of uncovering. All measure-ments were rounded off to thenearest 0.5 mm. The differences inthese 2 measurements deter-mined the amount of crestal boneloss that occurred during thisstage. Serial radiographs weretaken at uncovering and loading,and at 12, 24, and 36 monthsfollowing implant placement.The radiographs were sent to thedata management center in AnnArbor, Mich, where they werelabeled with the patient’s studycode and the evaluation visit thatthey represented. They were thencatalogued for future reference.

Although the direct measure-ments were rounded to the near-est 0.5 mm, the radiographs werethen placed on a view box andmeasurements were made to thenearest 0.1 mm using verniercalipers. Radiographs providedistorted images, and correctionsmust be made to more accuratelydetermine the correct measure-ment. The actual bone loss wascalculated using the equation forproportions shown in Figure 1A,and the change was entered intothe computer database. All dataentries were double-checked andverified to ensure that entryerrors were kept to a minimum.

RESULTS AND DISCUSSION

Many clinical studies of crestalbone loss around endosseousdental implants do not measurethe amount of crestal bone lostboth for the healing period (place-

ment to uncovering) as well as forthe period from uncovering to theloading of the prosthesis. Anyloss during this period is mostlikely associated with the surgicaltrauma during the preparation ofthe implant site. Because this lossis not caused by a characteristic ofa specific implant design, it isimportant data that needs to bedetermined and separated fromany bone loss that may be relatedto the implant. Although thetissue punch for abutment con-nection is recommended for thisimplant, to facilitate bone lossmeasurements tissue flaps werecarefully established to minimizetrauma at the time of implant

placement and uncovering. Di-rect measurements from the topof the implant body to the top ofthe crestal bone were made todetermine crestal bone loss dur-ing this period. It is again impor-tant to note that as a result of thisdeviation from the proceduresrecommended for abutment con-nection by the manufacturer, thereal bone loss may actually be lessthan that reported in this study.

From the time of implantplacement to abutment con-nection (uncovering), the meancrestal bone loss was 0.70 mm(the Table, Figure 1B). The 0.70mm of bone loss is the result ofthe surgical trauma that occurs at

FIGURE 3. (A) Crestal bone loss for each jaw region ranged from 0.6 to 0.8 mm for theperiod from loading to 36 months. This represented an annual loss of between 0.20and 0.26 mm. (B) The crestal bone loss for patients under the age of 60 and those overthe age of 60 was not found to be significantly different. The mean crestal bone lossfrom loading to 36 months was 0.59 mm (around 0.2 mm annually). UPPE indicatesmaxillary posterior partially edentulous; UCE, maxillary completely edentulous;LPPE, mandibular posterior partially edentulous; LCE, mandibular completelyedentulous.



the time of implant placementand not the implant design. Theslightly higher loss in BoneQuality-1 (BQ-1) is also mostlikely caused by frictional heatduring the preparation of theimplant site in dense bone insome less experienced clinicalresearch centers. Between thetime of abutment connection andloading of the prosthesis, therewas an additional increase of 0.11mm (total 0.81 mm) of bone loss,which can also be attributed tothe original surgical trauma at thetime of placement.

The mean crestal bone loss forall study implants from the timeof loading of the prosthesis to 12,24, and 36 months of clinicalloading is shown in the Table

and Figure 1B. The amount ofcrestal bone loss during theperiod from loading to 12 monthswas 0.15 mm (SE¼ 0.04), which iswell within the guidelines of 0.2mm/y following loading. For theperiod of 24 months followingloading, the mean loss was 0.48mm (SE¼ 0.09), which represent-ed an annual increase in the lossof bone of slightly more than 0.2mm. For the period from loadingup to 36 months, the crestal boneloss increased to 0.65 mm (SE ¼0.03), an additional increase of0.16 mm. These small increasesaveraged around 0.2 mm over the36 months postloading period,and although any crestal bone lossis of clinical interest, the lossesrecorded would not be large

enough to be clinically significant.The total overall mean loss fromthe time of implant placement to36 months was only 0.60 mm,which is less than that reportedfor other implants. From the timeof loading, the mean crestal boneloss each year fell within the range(0.2 mm/y) recommended as aguideline for clinical success ofendosseous dental implants (theTable, Figure 1A and B).

Figure 2 represents a typicalclinical case and the crestal boneresponse for most implants in thisstudy. It documents the clinicallyfavorable soft tissue response andthe radiographic documentationof minimal crestal bone loss asso-ciated with this new implantsystem. The radiographs at 36and 48 months postloading donot demonstrate any clinicallysignificant amount of crestal boneloss. Because loading of the finaldental prosthesis can have aneffect on the amount and type ofstresses the crestal bone is sub-jected to during clinical function,these data were was recorded.

The bone loss associated withdifferent prosthetic applicationsfor the period from loading to 36months is shown in Figure 3A.The largest amount of bone loss(0.8 mm) was found for themaxillary anterior completelyedentulous cases, followed bythe mandibular anterior com-pletely edentulous cases (0.7mm).The maxillary anterior jaw regionis an area well known for havingpoor bone density, so the largerbone loss is not surprising. Themaxillary posterior partiallyedentulous cases and the man-dibular posterior partially eden-tulous cases both had 0.6 mm ofloss in this same period. Thesedifferences among the variousprosthetic applications were notstatistically significant. When pa-tients were grouped into those 60years or younger and 60 years or

FIGURE 4. (A) Crestal bone loss associated with the health status of the patient (ASA-Iindicates healthy; ASA-2, mild systemic disease; ASA-3, severe systemic disease).There was no major difference in the crestal bone loss for ASA-1 and ASA-2 groups,whereas ASA-3 patients experienced somewhat higher amounts of bone loss. (B)Crestal bone loss associated with patients with a history of smoking and those whodid not smoke. There was no significant difference between the 2 groups.



older, the amounts of crestal boneloss was strikingly similar for theperiod from loading to 36 months(Figure 3B).

The health of the patient isoften a concern when evaluatingfor implant therapy. Patients be-ing entered into the study wereclassified using the AmericanSociety of Anesthesiology classi-fication.32,33 Healthy patients(ASA-1) lost 0.61 mm (about 0.2mm/y) of crestal bone heightfollowing loading to 36 months(Figure 4A), and patients withmild systemic disease lost aboutthe same amount of bone(0.56 mm). The largest bone loss(0.83 mm—slightly greater than0.2 mm/y) was found for thosepatients with a severe systemicdisease classification (ASA-3), butthis was not statistically signifi-cant from that recorded for theother health groups.

The influence of smoking onendosseous dental implant healthreported in the dental literaturesuggests that smoking may haveboth an adverse local and syste-mic affect on bone response.34-39

When grouped into smokers andnonsmokers, the loss of the heightof the crestal bone around theimplant was not found to besignificantly different (Figure4B). Bone density is of primaryimportance to implant survival. Itis interesting to note that BQ-1exhibited slightly more bone lossthan the other bone densities(Figure 5A); however, the differ-ences were not clinically signifi-cant. The slightly larger lossassociated with BQ-1 is mostlikely related to the greater den-sity of the bone and the surgicalexperience of the dentist. The typeof incision (remote vs crestal)used for implant placement didnot result in a significant differ-ence in bone loss (Figure 5B) nordid the type of incision used forabutment connection (Figure 5C).

CLINICAL RELEVANCE

Crestal bone response is believedto be critical to the long-termclinical success of an endosseousdental implant. The Ankylos im-plant represents a new implantdesign that departs from theidea of engaging cortical bone toprovide primary and long-termstability of endosseous implants.Instead, it attempts to engagetrabecular bone for primary andlong-term stability by directingthe stress during clinical functionaway from the cortical bone andonto the trabecular bone. This ap-proach is highly unusual and hasconsiderable theoretical merit, be-cause trabecular bone is moreresilient, and when damaged by

repetitive microstrains, it repairsmore rapidly than the crestalbone. Aside from the bone lossthat is the result of the surgicaltrauma, the crestal bone lossfollowing loading was minimalfor this implant. This suggeststhat the theory behind the im-plant design has been wellthought out, and that the implantworks well in a wide variety ofclinical situations.

SUMMARY AND CONCLUSIONS

Within the conditions establishedin the clinical protocol for theassessment of crestal bone re-sponse, this implant design iswellsuited for use in the rehabilitation

FIGURE 5. (A) Crestal bone loss associated with each bone density: bone loss wasgreater for dense BQ-1, which is more resistant to the preparation of the implant siteand can result in an increase in surgical trauma. (B) Crestal bone loss associated withthe type of incision used for implant placement: there was no significant differencebetween the remote and the crestal incisions. (C) Crestal bone loss associated with thetype of incision used for the connection of the abutment: the crestal bone loss wasalmost identical to that found during the placement of the implant.



of fully edentulous and partiallyedentulous patients of all races,ages, health status, bone density,and tobacco use. Crestal bone losswas less than the suggested limitsfor clinical success: less than 1.5mm for the first year and 0.2 mmeach year thereafter followingloading of the prosthesis. Morespecifically, the data suggest thefollowing conclusions:

� Direct measurement of thecrestal bone loss caused bysurgical trauma was found tobe around 0.7 mm betweenimplant placement and abut-ment connection. This is wellwithin what is considered ac-ceptable limits.

� After abutment connection,there was an additional lossof crestal bone of about 0.11mm, which is most likely theresult of a carryover effect fromthe surgical trauma duringimplant placement.

� The total overall mean crestalbone loss from implant loadingto 36 months postloading was0.6 or 0.2 mm per year, whichincluded the loss that can beattributed to surgical trauma.This is an excellent overallresponse.

� The final prosthesis design, thepatient’s age, the patient’shealth status, the use oftobacco, the bone density, theincision type used for implantplacement, and abutment con-nection did not produce signif-icant differences in the amountof crestal bone loss.

ACKNOWLEDGMENTS

This investigation was supportedby Friadent GmbH, Mannheim,Germany (formerly Degussa AG,Hanau, Germany). Study investi-gators often spent time outside oftheir assigned duties to collect

and record data. The authorsgratefully acknowledge the dedi-cation and contributions of thecurrent and former clinical inves-tigators:

Ewha Woman’s Hospital (SouthKorea): Jang Woo Choi, DDS,PhD; Myung Rae Kim, DDS, MS,PhD.* Cathay General Hospital(Taiwan): Chin-Sung Chen, DDS;Shyuan-Yow Chen, DDS; Cherng-Tzeh Chou, DDS; Hong-Jeng Lin,DDS; Yueh-Chao Yang, DMD,MS.* Medical College of Virginia(Virginia): C. Daniel Dent, DDS;Julie Sharp, DDS.* University ofLouisville (Kentucky): John W.Olson, DDS, MS.* Vanderbilt Uni-versity (Tennessee): SamuelMcKenna, DDS, MS.* VAMC Bed-ford (Massachusetts): WilliamBornstein, DDS; Mohamad B.Ayas, DDS; Noah I. Zager,DMD.* VAMC Bronx (New York):Ira H. Orenstein, DDS*; ThomasE. Porch, DMD. VAMC Chill-icothe (Ohio): John Hofer,DMD*; Craig A. Holman, DDS;Diane E. Land, DDS; Lura Mar-shall, RDH; Richard Mauger,DDS. VAMC Danville (Illinois):James T. Freestone, DDS; Kevin J.Malley, DDS; John L. Reyher,DDS.* VAMC Dayton (Ohio):James R. Cole, DDS; Paul M.Lambert, DDS.* VAMC Detroit(Michigan): Rami Jandali, DMD,MS; Ahmad A. Kanaan, DDS, MS;Michael L. Linebaugh, DDS, MS;Richard A. Plezia, DDS, MS.*VAMC Houston (Texas): AllanW. Estey, DDS; Harry D. Gilbert,DDS*; George V. Goff, DDS.VAMC Huntington (West Vir-ginia): Stanley E. Dixon, DMD;Eugene M. Riehle, DDS.* VAMCKansas City (Missouri): James L.Beatty, DDS; John Bellome, DDS*;Richard J. Crosetti, DDS; LindaFilbern, RDH; Douglas A Pear-son, DDS; Rosa B. Solomon, DDS.

VAMC Lexington (Kentucky):Dolph R. Dawson, DMD; JohnDominici, DDS, MS*; Robert Mar-ciani, DMD. VAMC Little Rock(Arkansas): C. Gary Black, DDS; J.Robert Spray, DDS.* VAMC LomaLinda (California): James E. Ye-ager, DMD; Warren S. Yow, DMD,MS, MPH.* VAMC Louisville(Kentucky): Paul X. Dattilo,DMD*; Reid Nelson; John W.Olson, DDS; James W. Shaugh-nessy, DMD. VAMC Memphis(Tennessee): William D. Caldwell,DDS, MS; Daniel L. Reaves,DDS.* VAMC New Orleans (Lou-isiana): Henry H. Chen, DMD;Arthur G. Howe, DDS*; Daniel D.Gammage, DMD; LaurieMoeller, DDS. VAMC Northport(New York): David A. Abroff,DDS; Anthony J. Casino, DDS*;Richard S. Truhlar, DDS. VAMCPhoenix (Arizona): D. Barnes,DMD*; Vance Cox, DDS. VAMCPittsburgh (Highland Drive,Penn): Arthur M. Rodriguez,DMD, MS.* VAMC Portland (Or-egon): Larry B. Thompson, DDS,MS; J. Ernest Weinberg, DMD,MSD.* VAMC Richmond (Vir-ginia): C. Daniel Dent, DDS;William E. Hunter, DDS*; Law-rence E. Masters, DDS. VAMCSalem (Virginia): Phillip R. Davis,DDS; C. Dudley Parks, DDS*;Michael J. Vasisko, DDS. VAMCSan Francisco (California): Ri-chard Navarro, DDS, MS; RebekaG. Silva, DMD*; Dennis J. Weir,DDS, MA. VAMC Seattle (Wash-ington): John A. Bucher, DMD*;Randall R. Sobczak, DDS. VAMCSepulveda (California): Mark L.Monson, DDS; Lori A. Walker,DDS.* VAMC Washington, DC:Michael T. Curran, DDS*; GlennT. Haggan, DDS.* VAMC WestLos Angeles (California): StephenAncowitz, DDS; James Callahan,DMD*; Richard Nagy, DDS; Don-ald Sze, DDS. VAMC West PalmBeach (Florida): Carlos Alvarez,DMD; John Ball, DMD; Alfredo*Principal investigator.



Fernandez, DMD; Jerry Neidlin-ger, DDS.* VAMC Wichita (Kan-sas): John David Ball, DDS.*

Laboratories

DVA Central Dental Laboratory(Texas): Eugene Jones, DDS, MS.DVA Central Dental Laboratory(Washington, DC): John McCart-ney, DDS.

Project Office and DataManagement Center

VAMC Ann Arbor (Michigan):Harold F. Morris, DDS, MSy;Shigeru Ochi, PhDy; Jeanne Mid-dlebrook; Leigh Ann Dudley.

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NOTE

This is government-supported re-search and there are no restric-tions on its use. The results andopinions presented are those ofthe authors and do not necessar-ily reflect the opinions of theDepartment of Veterans AffairsMedical Research, the Office ofDentistry, or the American Acad-emy of Implant Dentistry. Thismanuscript does not represent anendorsement of the evaluatedimplant by the Department ofVeterans Affairs or the AmericanAcademy of Implant Dentistry.



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