Implantology Article Primary Dental Journal

7/28/2019 Implantology Article Primary Dental Journal

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IntroductionIn 2007, the GDC recognised clinicaldental technicians (CDTs) as a professioncomplementary to dentistry. Clinicaldental technicians are registered dental

professionals who provide completedentures direct to patients and otherdental devices on prescription from adentist. They are also qualified dentaltechnicians. Patients with natural teethor implants must see a dentist before theCDT can begin treatment. We hope tobe able to demonstrate the advantageof combining the skills of the dentist andCDT for the benefit of the patient, fromtreatment planning to fitting andaftercare.

Jonathan Hughes (CDT) was treatingthe patient in this case, undertaking theclinical stages of the denture constructionand implant bar verification as well asproviding technical support for the dentalimplant surgeon, Craig Parker.

Complex and highly technical treatmentplans are challenging for dentists anddental technicians operating alone, so tobe able to come together and work as ateam helps to overcome difficulties facedwhen treating these patients. It alsoenables the clinicians to concentrate on

providing aspects of treatment accordingto their own areas of strength. Thisshould lead to a more predictable andsuccessful outcome for the patient.

Case HistoryImplant overdenture treatment for theedentulous maxilla is challenging due toinherent anatomic and biomechanicalproblems. This case demonstrates theclose collaboration between a dentistand a CDT in an attempt to deliver asuccessful treatment outcome for thepatient in a difficult clinical scenario.

The patient was referred by his GDPcomplaining of an inability to tolerate hisupper partial denture due to a gagging

reflex. He was unhappy with hisappearance (figure 1) and inability tomasticate effectively. The patient and hisGDP were happy with the mandibulardentition and requested that we limit ourintervention to the maxilla. The dentalsurgeon and CDT worked alongside oneanother from the initial consultation tothe final review.

A history of the patients presentingcomplaint revealed that he had electedto have many of his failing incisor andpremolar teeth extracted within the lastfew years, with a view to wearing witha partial denture. This had beenunsuccessful because of a gaggingreflex and he been attempting tomanage without a prosthesis. He hadhad his molar teeth extracted over 20years ago without the provision of anyrestoration. The GDP was now hopeful

that we might be able to provide animplant retained restoration as asolution. A social history informed us thepatient was a 55 year old self employedelectrician, with a grown up family. Hismedical history was clear. His diet andthe potential existence of para-functionalhabits were discussed in detail anddiscounted.

ExaminationAn explanation of the different roles of aCDT and dentist was given to the patientand consent obtained for examination.

Visual examination of the patients facesuggested general symmetry with adecreased lower face height, possibly

associated with mandibular overclosure.Extraoral examination revealed nothingof note, except that his masseter musclesseemed large and there were no signsassociated with the temporo-mandibularjoint or muscles of mastication.

Intraorally, the soft tissues were healthyand the periodontal health was good,

with all sextants scoring zero on BasicPeriodontal Examination (BPE). Onlythree maxillary teeth remained at UR3,UL2 and UL3, with UR3 and UL2significantly broken down. A retainedroot was present in the UL6 region. Themandibular arch was largely completebut demonstrated tooth surface loss inthe incisor and canine region. The lowerincisors had some superficial stainingand the molars were restored with old,but sound amalgam restorations (LL5,LR6, LR7 and LR8) and porcelain fused

to a metal full crown (LL6) (figure 2).

Special InvestigationPeriapical radiographs provided bythe GDP indicated that the remainingteeth had no periodontal bone lossand were free of caries and periapicalpathology.

A cone beam computed tomograph(CBCT) was prescribed (see discussion)using the existing upper partial dentureas a radiographic template. Foil markerswere attached to the midline of the

denture teeth. This is an economical,simple and effective way of providinga radiographic template. The CBCT

TEAMWORK IN IMPLANT DENTISTRY: THE PROVISIONOF A MAXILLARY IMPLANT RETAINED OVERDENTURE

CRAIG PARKER(BCHD, MFGDP(UK), DPDS,CERT [DENTAL IMPLANTOLOGY]),DENTAL SURGEON, FGDP(UK) BOARD MEMBER AND PRINCIPAL OFPRIMLEY PARK DENTAL IMPLANTS, LEEDS

JONATHAN HUGHES (DIP. CDT [RCS ENG]), CLINICAL DENTAL TECHNICIAN

AND HEAD OF HUGHES DENTAL LABORATORY, HARROGATE

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Caption here?TEAMWORK IN IMPLANT DENTISTRY: THE PROVISIONOF A MAXILLARY IMPLANT RETAINED OVERDENTURE

(figure 3) was studied and confirmed thepresence of the retained root UL6. Itindicated sufficient vertical and orofacialridge dimensions to accommodatedental implants in the UR4, UR2, UL2and UL4 regions should this be required(figure 4). Reduced vertical alveolarbone in the posterior maxilla necessitatedthat implant placement further backwould require maxillary sinusaugmentation. Measurements from theCBCT indicated that 7mm vertical spaceabove the implant fixture head wasavailable to accommodate restorativeimplant components (figure 4), if

conforming to the existing occlusalvertical dimension. An increase in spacewould require an increase in occlusalvertical dimension.

The CBCT was referred to a consultantradiologist for examination, whoconfirmed the absence of pathologyassociated with structures visible on thescan outside the dento-alveolar region.

DiagnosisThe history, examination and specialinvestigations suggested that the patienthad a healthy periodontal condition andwas suffering overclosure, compromisedaesthetics and poor mastication due tothe loss of the majority of his maxillaryteeth. The inability to tolerate a maxillarydenture was considered to be due topoor stability, although the existingdenture had ideal tooth position,occlusion and fit. The poor toleranceof his existing denture was consideredto be further compromised by gagging,attributed to a conventionally positionedpost dam.

Treatment PlanTreatment options were considered withthe patient (see discussion) including:extracting the remaining maxillary teethand providing a conventional full denture;retaining the maxillary canine rootsand providing a full overdenture, with

or without precision attachments;provision of a fixed, or removable,implant-supported prosthesis on siximplants including possible bilateralmaxillary sinus augmentation; or aremovable implant retained full-archprosthesis on four implants. A decisionwas made to provide the latter withimplants on UR4, UR2, UL2, UL4supporting a milled, titanium Dolder bar,retaining a full denture in the maxilla.

A final treatment plan was formulatedand written consent gained from thepatient:1 Extract UR3, UL2, UL3 and UL6

root and fit an immediate full uppertemporary denture

2 Place dental implants UR4, UR2,UL2, UL4

3 Provide a full upper denture withoutpalatal coverage, retained by animplant-supported milled bar

TreatmentVisit 1CDT presentAlginate impressions were taken and asilicone putty (Express, 3M ESPE, MNUSA) registration was taken in a centrictray (Ivoclar Vivadent, Liechstenstein).The centric tray registration enablesmodels to be articulated at an overclosed vertical dimension, with anindication of antero-posterior intermaxillary

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relationship. This was required for theconstruction of a gnathometer for thenext visit.

Visit 2

CDT presentOcclusion was recorded using agnathometer (Ivoclar Vivadent,Liechtenstein). The gnathometer consistsof an upper plate (figure 6) and a lowerplate with a screw (figure 7). Ink dots

were marked on the patients nose andchin. The patient was asked to speakand count, and the vertical face heightat rest (phonetic rest position) wasrecorded. The screw in the mandibularrim of the gnathometer was thenadjusted to a height that allowedcomfortable closure (2-4mm freewayspace) (figure 8). The maxillary platewas then covered using a chinagraphpencil (figure 9). The patient wasasked to make lateral and protrusivemovements, and the mandibular pindescribed an envelope of movementonto the plate (figure 10). The mostposterior point on the tracing representsthe retruded position of the mandible.A perspex guide was locked to themaxillary plate with sticky wax(Kemdent, UK) restricting the patientto occlude only in the retruded position(figure 11). Occlusal face height waschecked again in the retruded position;it was verified that the patient was

comfortable and that there was anallowance of 2-4mm freeway space(figure 12). Bite registration material(Futar-D, Kettenbach, Germany) wasused to locate the rims to one another(figure 13). An upper special trayimpression was taken with a polyether(Impregum, 3M ESPE, MN USA) in aspaced, cold cure acrylic tray with theperiphery modified with green stickcompound.

Visit 3

CDT present

A wax try-in was carried out to checkcomfort, occlusion, stability, aestheticsand tolerance to the proposed post-damposition (figure 14).

Visit 4Dentist and CDT present

The remaining maxillary teeth wereextracted and an immediate full upperacrylic denture was fitted.

Visit 5Dentist present

Five weeks later dental implants wereplaced on UR4, UR2, UL2 and UL4(4.1mm diameter, 10mm, soft tissuelevel, regular neck, standard-plus,Straumann, Switzerland). For the sakeof brevity, details of surgery have notbeen included here.

Visit 6Dentist present

Implants were reviewed after one weekto check comfort and healing.


Twelve weeks later, full osseointegrationof the dental implants was checked andverified by comfort, clinical appearance(figure 15), gentle periodontal probing

(and baseline probing depths recorded),percussion tests and periapicalradiographs.

A closed-tray impression was takenusing snap-on copings (Straumann,Switzerland) and polyether impressionmaterial in a modified, cold-cured,acrylic special tray (figures 16, 17).


The occlusion was recorded with agnathometer again, as in Visit 2, but

this time with a screw-retained upperacrylic plate for accuracy (figure 18).A cold-cure resin (Pi-Ku-Plast, Bredent,Germany) verification jig was used tocheck the accurate registration ofimplants (figures 19, 20). A special trayhad been constructed to facilitate a pick-up impression should the jig need to besectioned and reconnected. This wasnot required.

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The models were mounted on anarticulator (Gnathomat, Ivoclar Vivadent,Liechtenstein).

Visit 9

CDT presentA screw retained wax try-in on a coldcure acrylic baseplate was carried outand checked as per Visit 3 (figure 21).The try-in is carried out before manufactureof the bar so that the bar can be designed

digitally by the laboratory within the contoursof the proposed prosthesis (figure 22).


A computer aided design and computeraided manufacture (CAD-CAM) producedmilled, titanium, Dolder bar (manufacturedby ISUS, Dentsply-ES, Belgium ) waschecked for passive fit (figure 23).

A bar retained wax try-in on cold-cureacrylic baseplate was carried out andchecked for final verification, as perVisit 9 (figures 24-27).


The full acrylic, bar retained denturewas fitted with checks as per Visit 9 andVisit 10 (figures 28-31). The patient wasinstructed in denture insertion, dentureremoval and appropriate hygieneprocedures.


At the review appointment one weeklater, the patients oral hygiene andcomfort were checked, as were thestability, aesthetics and phonetics of thedenture. No adjustments were necessary.Baseline periodontal probing depthswere repeated.

Visit 13

Dentist presentThree month review checks wererepeated.

Visit 14

Dentist and CDT present

Six month review checks wererepeated with special attention to anyloss of soft tissue support that wouldmake a reline necessary. Noabnormalities were detected and thepatient was happy.

DiscussionAs explained, CBCT was prescribed asa special investigation to aid treatmentplanning. There is little consensus in theUK and Europe regarding the use ofcross-sectional imaging. RecentEuropean guidelines state that if theclinical assessment of implant sitesindicates that there is sufficient bonewidth and the conventional radiographicexamination reveals the relevant

anatomical boundaries and adequatebone height and space, no additionalimaging is required for implantplacement.1 There are many limitationsto conventional clinical and radiographicexaminations, particularly whentreatment planning for full archrestoration in the maxilla. The thickfibrous soft tissues of the maxilla veryoften give the clinical appearance ofa bulky alveolar ridge when in reality

surgery exposes a knife-edged ridge,often with a variety of deficiencies thatcan be quite extensive. The complex andvaried topography of the ridge canmake it enormously difficult to predictthe bony outline form of the maxilla withconventional ridge-mapping techniques.

Also, one of the major benefits of theuse of digital treatment planning is theability to visualise the bone availablefor implants relative to the proposedrestorative position of the restored teeth.This requires CBCT to be taken withthe patient wearing an accurateradiographic template, based on theidealised arch design. In this case, weused the patients existing denture withfoil markers attached to the labialsurfaces of the denture teeth. Thisenables the clinician to accurately assess

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ridge dimensions and horizontal andvertical ridge discrepancies, relative tothe ideal arch design. This is virtuallyimpossible to evaluate with conventionalclinical and radiographic examinationand can have a fundamental influenceon treatment planning. It is the authorsopinion that it is impossible for thepatient to consent to a surgicalintervention when the potentialrestorative options have not been fully

evaluated and communicated to thepatient using three-dimensionaltreatment planning.

The patients existing denture wasconsidered to be well designed andconstructed, yet on evaluation hadinadequate retention and stability,largely because of the inability toincorporate sufficient palatal extensiondue to the patients gagging reflex. Itwas decided that the provision of a newupper denture with or without precisionattachments on the remaining canineswould provide insufficient improvementin retention and stability. The decisionwas made to provide an implantretained overdenture. The literatureindicates that an implant retained,overdenture prosthesis providespredictable results, with enhancedstability, function and a high degreeof patient satisfaction compared toconventional removable dentures.2

It is important here to differentiatebetween an implant retained overdentureand an implant supported overdenture.The former is essentially soft tissue bornewith retention and stability enhancedby a bar, or individual retentive anchorsattached to dental implants. The retainernormally allows some movement of theprosthesis so that stresses are transferredto the oral mucosa rather than to thedental implants. The latter is rigidly

held and normally involves six implantsconnected with a two degree milled barretaining a removable prosthesis with aspark eroded, closely fitting, secondaryframework with parallel friction pinsand swivel latch attachments. Cost andcomplexity of this treatment option inthis instance were deemed to be toohigh. For the same reasons, it wasdecided that a fixed, implant supportedrestoration was not appropriate in thiscase.

Much controversy exists regarding caseselection and the criteria for designing amaxillary implant overdenture. A reviewof the literature reveals that when bonequantity and quality are satisfactory,overdenture and fixed prostheses bothachieved a 92% implant survival overfive years.3 However, it has also beensuggested in the literature that maxillaryimplant overdentures (MIOs) have beendocumented with a high implant loss

relative to other endosseous implanttreatment modalities.4-6

In comparison to the edentulousmandible, implant overdenture therapyfor the maxilla is often compromised byreduced bone quantity/quality7, 8 andalso subjected to higher biomechanicalforces.9

There are no specific guidelines for

the number of implants necessary tosupport a maxillary overdenture.10, 11

However, for a design without palatalcoverage, there appears to be aconsensus in the reviewed literaturethat a minimum of four implants isfavourable.12-15

A decision had to be made regardingwhether to use a bar design, whichsplints the implants together, or a systemof individual, retentive anchor elements.We made the decision to provide asplinted solution because of concernsregarding high occlusal stresses onthe implants. However, on studyingthe literature a lack of standardisationof prosthetic procedures,12 numberof implants,16,17 marginal bonemeasurements,18 bone quantity,8 andloading conditions,4,16 as well asinsufficient sample size,17,18 haveplagued an objective assessment of thepreferred retention system for MIOs.

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In fact, Trakas et al19 concluded thatit appears there is no significantdifference in mean bone loss betweensubjects with ball or bar retainedoverdentures. The use of a bar in this

situation involved similar cost toindividual retentive anchors but futuremaintenance of a bar could prove to bemore complex and costly (see below).

With regard to patient satisfaction,patients appear to be equally satisfiedwith bars or solitary anchors retaininga maxillary, implant overdenture4,16.

Unsplinted anchorage systems mayrequire less space within the prosthesis,be easier to clean and be moreeconomical, as well as being less

technique sensitive and easier whenmanaging splinted designs20. In thevertical axis, a minimum distance of13-14 mm from the implant platform to

the incisal edges is necessary with a bardesign, allowing 4.0 mm for the barand 1.0 mm below the bar for hygiene,as well as space for the clip andacrylic/tooth housing21. Using digital

treatment planning, vertical spaceassessment can be made from theCBCT prior to commencing treatment.Available vertical and orofacial spacefor retentive elements can also then beverified from the digital impression of thepreliminary wax try-in, before definitivebar design is finalised.

Although costs and complexity arereduced in the initial provision of anMIO, it should be recognised thatmaintenance issues can be significant,time consuming and costly in the

longer term. Clarifying this issue withthe patient from the outset is importantto gain informed consent to this form oftreatment. MIOs are reported to have ahigh number of complications11, 22, 23, 24

and may require more post-insertionmaintenance than implant-supportedfixed prostheses23, 25, 26. Higherincidence of mechanical problemswith MIOs, especially without palatalcoverage27, 24 relative to mandibularprostheses may be due to higherloading found in the maxilla fromopposing natural teeth or fixed

restorations11. Furthermore, limitationsin vertical space for prostheticcomponents are more common in themaxilla because of contour and phonetic

REFERENCES

1 Harris D Horner, Grondahl K,Jacobs R, Helmrot E, Benic G etal. E.A.O Guidelines for the useof diagnostic imaging in implant

dentistry 2011. A consensusworkshop organized by theEuropean Association ofOsseointegration at the MedicalUniversity of Warsaw. Clin OralImplant Res. 2012; 23:1243-53.

2 Laurito D, Lamazza L, Spink MJ,De Biase A. Tissue supportedimplant prosthesis (overdenture):the search for the ideal protocol.A literature review. Ann Stomatol(Roma) 2012 Jan;3(1):2-10

3 Jemt T, Lekholm U. Implanttreatment in edentulous maxillae:a 5-year follow-up report onpatients with different degrees

of jaw resorption. Int J OralMaxillofac Implants

1995;10:303-11.4 Bergendal T, Engquist B. Implant-

supported overdentures: alongitudinal prospective study.Int J Oral Maxillofac Implants1998;13:253-62.

5 Jemt T, Chai J, Harnett J, HeathMR, Hut- ton JE, Johns RB, et al.A 5-year prospective multicenterfollow-up report on over-denturessupported by osseointegratedimplants. Int J Oral MaxillofacImplants 1996;11:291-8.

6 Johns RB, Jemt T, Heath MR,Hutton JE, McKenna S,McNamara DC, et al. Int J OralMaxillofac Implants 1992;7:513-522.

7 Chan MF, Narhi TO, de Baat C,Kalk W. Treatment of the atrophicedentulous maxilla with implant-supported overdentures: a review

of the literature. Int J Prosthodont1998;11:7-15.

8 Hutton JE, Heath MR, Chai JY,Harnett J, Jemt T, Johns RB, et al.Factors related to success andfailure rates at 3-year follow-upin a multicenter study ofoverdentures supported by

Branemark implants. Int J OralMaxillofac Implants 1995;10:33-42.

9 Rodriguez AM, Orenstein IH,Morris HF, Ochi S. Survival ofvarious implant-supportedprosthesis designs following36 months of clinical function.Ann Periodont 2000;5:101-8.

10 Kronstrom M, Widbom C,Soderfeldt B. Patient evaluationafter treatment with maxillaryimplant-supported overdentures.Clin Implant Dent Relat Res2006;8:39-43.

11 Chan MF, Narhi TO, de Baat C,

Kalk W. Treatment of the atrophicedentulous maxilla with implant-

supported overdentures: a reviewof the literature. Int J Prosthodont1998;11:7-15.

12 Kiener P, Oetterli M, Mericske E,Mericske-Stern R. Effectiveness ofmaxillary overdentures supported

by implants: maintenance andprosthetic complications. Int JProsthodont 2001;14:133-40.

13 Lewis S, Sharma A, Nishimura R.Treatment of edentulous maxillaewith osseointegrated implants.J Prosthet Dent 1992;68:503-8.

14 Mericske-Stern R. Treatmentoutcomes with implant-supportedoverdentures: clinicalconsiderations. J Prosthet Dent1998;79:66-73.

15 Naert I, Gizani S, vanSteenberghe D. Rigidly splintedimplants in the resorbed maxillato retain a hinging overdenture:

a series of clinical reports for upto 4 years. J Prosthet Dent

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considerations,28 which may result incompromises in design and materialfailure29. After a five year follow up,Watson et al29 reported a threefoldincrease in fractures in the body of

the prosthesis with overdentures forthe maxilla compared to the mandible.However, Smedberg et al30 in a sixyear study found that a cast, chromecobalt framework reinforcementeliminated this complication. We madethe decision not to incorporate such aframework because of space limitations,but in the event of prosthesis fracturewe will attempt to redesign theprosthesis to incorporate astrengthener.

Regardless of the anchorage system, the

predominant complication in maxillaryoverdenture therapy involves failure ofthe retention system resulting fromloosening or fracture. Jemt et al23

reported as high as 17% clip retentionproblems and 22% clip fractures in thefirst year.

The provision of an acrylic dentureincorporating a clip is relativelyinexpensive approach and this enabledus to produce a spare denture for thepatient to use in the event of fracture

while a repair is carried out. Weconsidered it most appropriate toprepare for the failure of the prosthesisand be ready to manage the situationwith the least inconvenience to the

patient.

SummaryThis case demonstrates a pragmatic, yetsystematic, team approach to resolvinga challenging clinical situation. It isessential to understand and accept thechallenges presented and limitations ofthe treatment options available in theprovision of an MIO. The dental surgeonand clinical dental techniciancollaborated using their combinedskills set. Working as a team giveseach clinician a greater appreciation

of the difficulties faced clinically andtechnically. We believe that an enhancedstandard of care is delivered to patientsby using this team approach.

1998;79:156-64.16 Narhi TO, Hevinga M, Voorsmit

RA, Kalk W. Maxillaryoverdentures retained by splintedand unsplinted implants: aretrospective study. Int J Oral

Maxillofac Implants2001;16:259-66.

17 Quirynen M, Naert I, vanSteenbergheD. Fixture designand overload influence marginalbone loss and fixture success inthe Branemark system. Clin OralImplants Res 1992;3:104-11.

18 Schwartz-Arad D, Kidron N,Dolev E. A long-term study ofimplants supporting overdenturesas a model for implant success.J Periodontol 2005;76:1431-5.

19 Trakas T, Michalakis K, Kang K,Hirayama H. Attachment systemsfor implant retained overdentures:

a literature review. Implant Dent2006;15:24-34.

20 Watson CJ, Tinsley D, Sharma S.Implant complications andfailures: the completeoverdenture. Dent Update2001;28:234-8, 240.

21 Phillips K, Wong KM. Space

requirements for implant bar-and-clip overdentures. CompendContin Educ Dent 2001;22:516-8, 520, 522.

22 Ekfeldt A, Johansson LA, IsakssonS. Implant-supported overdenturetherapy: a retrospective study. IntJ Prosthodont 1997;10:366-74.

23 Jemt T, Book K, Linden B, Urde G.Failures and complications in92 consecutively insertedoverdentures supported byBranemark implants in severelyresorbed edentulous maxillae:a study from prosthetic treatmentto first annual check-up. Int J

Oral Maxillofac Implants1992;7:162-7.

24. Widbom C, Soderfeldt B,Kronstrom M. A retrospectiveevaluation of treatments withimplant-supported maxillaryoverdentures. Clin Implant DentRelat Res 2005;7:166- 72.

25 Jemt T, Book K, Lie A, Borjesson T.Mucosal topography aroundimplants in edentulous upperjaws. Photogrammetric three-dimensional measurements ofthe effect of replacement of aremovable prosthesis with a fixedprosthesis. Clin Oral ImplantsRes 1994;5:220-8.

26 Zarb GA, Schmitt A. Theedentulous predicament II:The longitudinal effectiveness ofimplant supported overdentures.J Am Dent Assoc 1996;127:66-72.

27 Sadowsky SJ. The implant-

supported prosthesis for theedentulous arch: design

considerations. J Prosthet Dent1997;78:28-33.

28 Smedberg JI, Nilner K, FrykholmA. A six-year follow-up studyof maxillary overdentures onosseointegrated implants.

Eur J Prosthodont Restor Dent1999;7:51-6.

29 Watson RM, Jemt T, Chai J,Harnett J, Heath MR, Hutton JE,et al. Prosthodontic treatment,patient response, and the needfor maintenance of completeimplant-supported overdentures:an appraisal of 5 years ofprospective study. Int J Prostho-dont 1997;10:345-54.

30 Smedberg JI, Nilner K, FrykholmA. A sixyear follow-up studyof maxillary overdentures onosseointegrated implants. Eur JProsthodont Restor Dent

1999;7:51-6.

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