Mandibular Two-Implant-Retained Overdenture:Prosthetic Design andFabrication Protocol

CE2

Compendium • February 2007;28(2):80-89

Treatment options for the reha-bilitation of the edentulousmandible include a conven-

tional complete denture and a dentalprosthesis supported or retained bydental implants.1-3 Dental literature isunequivocal on the advantages of theimplant-anchored prosthesis (eg, im-proved quality of life for the patientand long-term preservation of theremaining alveolar and basal bone).4-9

Several designs of the implantprosthesis have been used in the reha-bilitation of the edentulous mandible.These designs have been classified bythe nature of the support provided tothe prosthesis: implant-supported fixedprosthesis, implant-supported remov-able overdenture, and an implant-re-tained and tissue-supported removableoverdenture.3 In the first 2 options, thedental prosthesis is completely sup-

ported by dental implants. Thesedesigns require at least 3 well-distrib-uted implants and sophisticated fabri-cation protocols that usually translateinto a higher cost of treatment.3,10-15 Inthe case of the implant-retained over-denture, retention to the dental pros-thesis is provided by the dental im-plants, and most of the support isgained from the coverage of the alveo-lar ridge.3,16,17

In contrast to the implant-support-ed alternatives, this treatment can becarried out with a minimal number ofimplants, and its fabrication is a rela-tively straightforward practice.16,18,19

Consequently, these characteristics ex-plain the lower treatment cost associat-ed with this design and its widespreadacceptance.13,14,20-23 Also, the efficacy ofthis treatment has been validated bynumerous clinical trials.4,5,24-26

Alexander Shor, DMD, MSDAffiliate Assistant ProfessorDepartment of Restorative DentistryUniversity of WashingtonSeattle, Washington

Private PracticeSeattle, Washington

Yoshihiro Goto, DDS, MSDClinical Assistant ProfessorDepartment of Restorative DentistryUniversity of Southern CaliforniaLos Angeles, California

Private PracticeLos Angeles, California

Kavita Shor, BDS, MSDPrivate PracticeSeattle, Washington

Abstract

Among different treatment options, an implant-retained overdenture is a simple, cost-effective solution in the rehabilitation of the edentulous mandible. Despite wide-spread acceptance of this treatment, some controversies still exist with regard to thedesign of the overdenture, selection of the appropriate attachment system, and themost optimal techniques for the overdenture fabrication. In this article, the authorsdescribe a mandibular overdenture retained by 2 freestanding implants placed in theanterior region of the mandible. The overdenture design includes a metal-reinforcingframework and uses prefabricated stock abutments and hinge-type resilient attach-ments for its retention. The proposed fabrication technique requires a minimal num-ber of clinical appointments, and resilient attachments are incorporated into the over-denture in the laboratory.

• explain the characteristics of severaldesigns of the implant prosthesis.

• describe advantages and disadvan-tages of different designs of theimplant prosthesis.

• discuss a design and fabrication tech-nique of the implant-retained over-denture that uses 2 freestandingmandibular implants.

Learning ObjectivesAfter reading this article, the reader should be able to:

Compendium • February 2007;28(2):80-89

The most common protocol used in the implant-retained overdenture treatment includes placement of 2implants in the anterior area of the mandible. The designof the 2-implant-retained overdenture can be carried out in2 ways.3,25,26 In the first approach, implants are splintedwith a rigid interconnecting bar that incorporates anattachment mechanism for the overdenture retention. Inthe other approach, implants are not connected to eachother, and the retention mechanism is provided by an abut-ment that incorporates some form of retentive mechanism.

Clinical evaluation of these designs has been carriedout in numerous clinical trials, and literature indicatessimilar outcomes for the implant longevity irrespective ofimplant splinting.25-28 However, prosthodontic mainte-nance and patient satisfaction differ depending on theindividual attachment system, which potentially is ofmore importance than the splinting of the implants.26,27,29-

31 For example, attachments that have low retentivestrength negatively affect patient satisfaction.26,30 Someattachments also have a high rate of mechanical failure,which requires continuous investment of time and main-tenance cost.31 Based on this data, it is evident that thechoice of the individual attachment system is of criticalsignificance.

Given these design options, freestanding implantshave distinct advantages over the splinted implants suchas a reduced number of fabrication steps and lower treat-ment cost. However, optimal performance of the free-standing attachments requires relatively good parallelismand correct angulation of the implants.32,33 Conversely,splinting of the implants may be beneficial where im-plants have less than ideal angulation. Splinting of theimplants also can be advantageous in clinical scenariosof malpositioned implants, where implants encroach onthe overdenture contours. In these situations, fabricationof the bar allows for the relocation of the attachmentmechanism into the greatest bulk of the overdenture.34

Fracture of the prosthesis is a rare but potentiallygrave complication that occurs with implant-retainedoverdentures.26,29 A common etiology of this problem in-cludes minimal thickness of the denture base resin over-lying the attachment hardware. Evaluation of the verticalspace for the prosthetic components and denture thick-ness should be performed at the treatment planningstage to prevent this untoward problem.35,36 Potentialsolutions to the inadequate vertical space include alve-

oloplasty surgery at the time ofimplant placement, selection of theattachment hardware with a mini-mal height, and incorporation ofthe metal-reinforcing frameworkinto the overdenture.3,37

Another dilemma associatedwith overdenture treatment is thetechnique of incorporating the at-tachment matrices into the overden-

ture. Several possible approaches have been described inthe dental literature. One approach includes incorporationof the matrices into the overdenture in the dental laborato-ry. The other approach is their pick-up intraorally in theclinic.16,38-40 This is an extremely important step and, if notperformed correctly, can negatively influence overdenturefit or contribute to the dislodgement of the matrix from theoverdenture. Unfortunately, dental literature does not pro-vide definitive guidelines, and limited information existson the advantages and disadvantages of the available tech-niques.

This article presents a design and fabrication tech-nique of the implant-retained overdenture that uses 2 free-standing mandibular implants. The overdenture designincludes a metal-reinforcing framework and uses prefabri-cated stock abutments and hinge-type resilient attach-ments for its retention. The proposed fabrication tech-nique requires a minimal number of clinical appoint-ments, and resilient attachments are incorporated into theoverdenture in the laboratory, reducing the number ofclinical steps (Table 1).

Case PresentationA 67-year-old woman presented for the prosthodon-

tic rehabilitation of her edentulous jaws. Her dental his-tory included extraction of the hopeless teeth and theirreplacement with maxillary and mandibular immediatedentures, which were relined on several occasions. Sheexpressed desire for the improved retention of the den-tures and asked for changes in the appearance of herprostheses. Clinical and radiographic examination re-vealed a moderate to severe degree of alveolar ridgeresorption. Evaluation of the existing dentures revealedinadequate denture extensions, poor retention and stabil-ity, and satisfactory position of the denture teeth (Figures1 through 3). A treatment plan was prepared after a stan-dard protocol that took into consideration the patient’sdesires, treatment alternatives, and treatment costs. Theplan included fabrication of a conventional completedenture for the maxilla and a 2-implant-retained overden-ture for the mandible.

Implant Placement SurgeryBecause of the adequate position of the denture

teeth, a decision was made to use a duplicate of themandibular denture as a surgical template for the implant

Table 1—Summary of clinical and laboratory procedures for overdenture fabrication.Clinical procedures Laboratory procedures1. Preliminary impression 1. Fabrication of the custom tray

Fabrication of the occlusal registration tray 2. Final pick-up–type impression 2. Fabrication of the master cast

Centric relation recording Mounting of the master castFabrication of metal frameworkPick-up of the attachments to the frameworkFabrication of the wax trial overdenture

3. Try-in of the wax trial overdenture 3. Processing of the overdenture4. Prosthesis delivery

surgery. The mandibular denture was duplicated in a 2-part top and bottom polyvinylsiloxane flask using clearautopolymerized acrylic resin (Figure 4). For the plan-ning of the surgery, a duplicate denture was seated intothe patty of fast-setting stone. The desired implant loca-tion was marked on the duplicate denture and stone cast.In the transverse plane, it corresponded to the interprox-imal area between the mandibular cuspid and lateral inci-sor. Anteroposteriorly, it was placed in the crest of themandibular ridge. The duplicate denture was modified forthe surgery by creating window-like openings in the areas

of proposed implant sites. Corresponding implant posi-tion and angulation was marked on the surgical templatewith an indelible ink pen (Figure 5). Vertical space analy-sis of the denture was performed for the selected attach-ment system (Locator Implants Attachmenta). Otherproducts available are ERAb and VKS-OC RSc. It revealedthat 3 mm of vertical ridge reduction would be requiredto provide for the adequate thickness of the overdenture.

Implant surgery included alveolar ridge reductionand placement of the implants with the help of a surgicaltemplate. Implant surgery was carried out in a 1-stagesurgical protocol, and after completion, the mandibulardenture was relined with a soft-tissue conditioning mate-rial. No complications were encountered during the sur-gical phase. Three months later and after confirmation ofthe osseointegration, the patient presented for the defin-itive prostheses fabrication (Figure 6).

Final Impression and Mounting to the ArticulatorThe following preparations were made for the maxil-

lary and mandibular final impressions. The maxillary den-ture was duplicated in a silicone mold similar to the previ-ously described fabrication of the mandibular duplicate

Compendium • February 2007;28(2):80-89

Figure 1—Initial presentation of the patient. Figure 2—Occlusal view of the edentulous mandible at the time of initial presentation.

Figure 3—Smile view of the patient.

a Zest Anchors, Escondido, CA 92029; www.zestanchors.comb Sterngold, Attleboro, MA 02703; www.sterngold.comc Bredent USA, Miami, FL 33186; www.bredent.com

Figure 4—Duplication of the denture is carried out in 2-part polyvinylsiloxanemold.

Figure 5—Duplicate denture is converted into a surgical template.

Compendium • February 2007;28(2):80-89

denture. The intaglio surface of the maxillary duplicatedenture was relieved by several millimeters, and numerousholes were created for the retention of the impression mate-rial. The patient’s mandibular denture was seated into thesilicone putty to obtain a diagnostic cast of the mandible. Alight-polymerized custom tray (Triad TruTrayd) for thefinal impression was fabricated on this cast. Also, a flatlight-polymerized occlusal registration tray in the form of amandibular arch was fabricated on the same cast. Twoopenings in the location of the implants were created in thetray. Multiple notches were created on the occlusal surfaceof the tray posterior to the openings to serve as an orienta-tion guide for the occlusal registration material.

A maxillary final impression was taken using a com-bination of high and low viscosities of the polyvinylsilox-ane impression material placed inside the duplicate den-ture. Care was taken to center the denture during seating,and standard border molding procedures were used.After setting, the final impression was inspected anddeemed acceptable (Figure 7). The duplicate denture wasreinserted intraorally for the dentofacial evaluation(Figure 8), and the ideal location of the maxillary midlineand incisal-occlusal plane was recorded. Standard photo-graphs of the patient’s smile also were taken to be used in

the laboratory for the denture tooth setup. The case was returned to the laboratory where stan-

dard protocols were used for the fabrication of the mastercast. The maxillary cast with the duplicate denture waspositioned on the flat plane of the Kois Index Traye seatedon the Kois Adjustable Platforme. The duplicate denturewas secured to the index tray and mounted to the uppermember of a semiadjustable articulator (Panadent PCHe)(Figure 9). The corresponding location of each maxillarytooth was marked on the index tray, and the vertical rela-tionship between each denture tooth and the index traywas recorded in millimeters and marked on the plane. Inpreparation for the denture tooth setup, an autopolymer-ized acrylic resin record base was fabricated on the maxil-lary master cast. The master cast with the attached recordbase was repositioned to the upper member of the articu-lator against the index tray. Artificial denture teeth wereselected based on the references provided by the existingdentures and the patient’s preference for a specific shade.The maxillary denture tooth setup was completed usingthe references provided by the index tray (Figure 10).

For the mandibular final impression, pick-up–typeimpression copings were seated on the implants (Figure11). The complete seating of the copings was verified with

Figure 6—Two implants are placed in the anterior region of the mandible. Figure 7—Maxillary final impression is taken inside the maxillary duplicatedenture.

Figure 8—Dentofacial evaluation of the duplicate denture. Figure 9—Maxillary master cast is mounted to the upper member of the articulator.

d Dentsply International, York, PA 17405; www.dentsply.com e Panadent, Grand Terrace, CA 92313; www.panadent.com

periapical radiographs. The mandibular final impressionwas taken using a combination of high and low viscositiesof the polyvinylsiloxane impression material placedinside the custom tray (Figure 12). The maxillary wax-trial denture was placed intraorally, and tooth positionwas evaluated using standard prosthodontic protocols.Proposed changes to the tooth position were recorded.

Centric relation recording was completed in the fol-lowing manner: A second set of pick-up–type impressioncopings was secured to the implants with the help of stan-dard retaining screws. The previously described occlusalregistration tray was seated over the impression copings

and attached by placing the light-polymerized composite(Triad Geld) in the area of the tray’s openings. A smallamount of modeling wax was placed behind the maxillarycentral incisors in the form of a flat plane, and the maxil-lary denture was placed intraorally. The light-polymerizedcomposite was placed in increments in the anterior area ofthe occlusal registration tray to form a cone-like verticalextension of the tray. This vertical extension was builtagainst the flat wax plane of the opposing maxillary den-ture, and its height was built to the desired level of the ver-tical dimension of occlusion (Figure 13). The centric rela-tion record was obtained by placing the occlusal registra-tion material on the posterior extensions of the tray andguiding the patient’s mandible into closure (Figure 14).

In the laboratory, implant analogs were attached tothe impression copings, and a soft-tissue model was madearound the implant analogs. A master cast was poured intype IV dental stone. The occlusal registration tray wasseated on the mandibular master cast. The mandibularand maxillary master casts were articulated to each otherwith a centric relation record, and the mandibular castwas mounted to the lower member of the articulator.

Metal Framework FabricationThe overdenture abutments (Locator Abutmenta)

were selected on the mandibular master cast based on theexisting soft-tissue depth around the implants. Abut-

Compendium • February 2007;28(2):80-89

Figure 10—Completed maxillary denture tooth setup. Figure 11—Pick-up–type impression copings are secured to the implants.

Figure 12—Mandibular final impression. Figure 13—Occlusal registration tray is attached to the impression copingsand cone-like extension is fabricated.

Figure 14—Centric relation recording.

Compendium • February 2007;28(2):80-89

ments were positioned on the master cast. The selectedattachments (Processing Capa) were placed on the abut-ments. Undercut areas of the attachments were blockedout with wax. One layer of the baseplate wax was placedin the edentulous areas on the master cast. The refracto-ry cast was fabricated by duplicating the mandibularmaster cast. The metal-reinforcing framework was waxedin a mesh-like form on the refractory cast, with theexception of the attachment areas, which were leftuncovered. Several vertical retentive elements werewaxed around the attachments on the framework. Theframework was fabricated in the chrome-cobalt alloy

using standard “lost wax” production techniques. The fitof the framework was verified, and its surface was fin-ished and polished. The framework was positioned onthe master cast (Figure 15). Attachments were picked-upto the framework with an autopolymerized acrylic resin,and polymerization was completed in the pressure pot(Figure 16). After completing this step, autopolymerizedacrylic resin extensions were fabricated over the distalextensions of the framework on the master cast.

Prostheses Fabrication and DeliveryThe mandibular master cast was repositioned on the

articulator, and the mandibular denture tooth setup wascompleted against the maxillary denture tooth setup (Figure17). The wax-trial dentures were returned to the clinic forthe try-in. The fit, occlusion, and esthetics of the prostheseswere verified intraorally and approved by the patient.

The prostheses were processed with a heat-polymer-ized acrylic resin using a standard compression moldingprotocol. The surfaces of the dentures were finished andpolished (Figure 18). Processing clips were replaced withthe light retention clips (Pink Malea) in the mandibularoverdenture (Figure 19).

In the clinic, abutments were attached to the mandib-ular implants and torqued to the manufacturer’s recom-mended value (Figure 20). The prostheses were seated,and excessive pressure areas were adjusted with the help

Figure 15—Completed metal framework is seated on the master cast. Figure 16—Attachments are connected to the framework with an autopolymer-ized acrylic resin.

Figure 17—Completed maxillary and mandibular denture tooth setup. Figure 18—Completed maxillary and mandibular prostheses.

Figure 19—Intaglio surface of the overdenture.

of pressure-indicating paste. The desired occlusal schemewas verified and adjusted intraorally. The patient receivedmaintenance instructions, and the recall appointmentsschedule was established. At the subsequent recall appoint-ment, the patient expressed satisfaction with the treat-ment (Figures 21 and 22).

DiscussionA major advantage of the freestanding implants is

the fact that they allow for the use of the prefabricatedstock retentive abutments. The use of the interconnect-ing implant bar requires additional laboratory and clini-cal procedures for its fabrication and the associatedincrease in treatment cost. However, in case of the mis-aligned or malpositioned implants, stock abutments maynot provide the desired compensation, and the splintingof the implants with the interconnecting bar can over-come these problems. Another advantage of the prefabri-cated stock abutments is that the abutment itself can beeasily replaced in case of abutment failure (eg, abutmentwear or abutment fracture). Because stock abutments areidentical, their replacement does not require remakingthe overdenture. On the other hand, if the implant inter-connecting bar has to be remade in the case of failure, itusually requires remaking the overdenture.

Performance data of the implant-retained overden-tures indicate that most of the complications and

prosthodontic maintenance are related to the attachmentcomponents of the overdenture.16,26,29,31 Literature alsoindicates that the rate of complications and maintenanceintervals is somewhat attachment dependent, whichunderscores the design characteristics of the specificattachment system. The most common problems includedegradation of the retention of the attachment matrixover time, mechanical failure of the matrix and retentiveabutment, dislodgement of the matrix from the overden-ture, and fracture of the overlying denture base resin.29

Based on these problems, the most desirable charac-teristics of a well-designed attachment system shouldinclude good retentive strength and longevity of theretentive components over time, ease of component re-placement, adequate structural strength of the compo-nents, adequate retention of the attachment matrix in theoverdenture, and minimal dimensional requirements forthe structural integrity of the overdenture. Despite thefact that a large body of literature is available on the clin-ical performance of the attachments, selection of theappropriate attachment system is not an easy task be-cause of the large number of available options and con-tinuous introduction of new designs in the dental mar-ket. Although no clinical performance data have beenreported for the Locator attachment in a well-controlledclinical trial, the authors believe that its design satisfiesthese requirements. The authors also would like toemphasize that this statement is solely based on theirclinical experience and believe that additional clinicalresearch is required to validate it.

The presented design of the overdenture incorporat-ed a metal-reinforcing framework for the prevention ofpotential overdenture fracture. This additional designelement is especially warranted in situations where theprosthesis presents with minimal thickness and/or theopposing jaw includes natural dentition or an implant-supported reconstruction.3 The metal framework re-quires additional investment of laboratory time; never-theless, it results in only a minimal increase in the cost oftreatment. Other than this drawback, it does not carryany other obvious disadvantages.

Another crucial step in the prosthesis fabrication is the

Compendium • February 2007;28(2):80-89

Figure 20—Intraoral view of the abutments. Figure 21—Intraoral view of the completed prostheses.

Figure 22—Smile photograph of the patient.

Compendium • February 2007;28(2):80-89

incorporation of the attachments into the overdenture. Inthe presented approach, the authors recommend connec-tion of the attachments to the metal framework as a sepa-rate step performed before the overdenture processing. Itappears that subsequent polymerization of the large vol-ume of acrylic resin in the overdenture does not have anysignificant effect on the displacement of the attachmentsbecause when secured to the metal framework, they resistpotential distortions associated with the processing of theoverdenture. On the other hand, incorporation of theattachments into the overdenture at the time of dentureprocessing has higher potential for distortion and poor fitbecause of the large volume of acrylic resin shrinkage. No

distortion analysis has been conducted for the overdentureprocessing techniques in a well-controlled clinical and lab-oratory trial, and the authors would like to state that ration-ale for this approach is solely empirically based.

Incorporation of the attachments into the frame-work at an early stage has additional advantages. It offersa good preview of the overdenture fit at the time of try-in, which provides a fail-safe mechanism where potentialdistortions associated with restorative and laboratoryprocedures can be detected at an early stage ahead ofdenture processing. Because the overdenture is securedto the abutments, it also offers an improved evaluationand recording of occlusal relationship at the time of thetry-in appointment.

Another approach for the incorporation of the attach-ments into the overdenture is their chairside pick-upafter overdenture processing. An advantage of this ap-proach is that it avoids potential distortions associatedwith the clinical and laboratory procedures during over-denture fabrication, ensuring acceptable fit of the over-denture. However, it requires additional clinical time andis technique sensitive. In contrast to the laboratory pick-up, which offers a well-controlled environment, adequateconnection of the attachments in the mouth can bepotentially hampered by the presence of moisture con-tamination and incorporation of the porosities into theresin, which can contribute to their dislodgment. On theother hand, chairside pick-up can be a technique ofchoice in situations where the existing denture is con-verted to the overdenture prosthesis.

In the presented approach, centric relation recordingwas carried out with the help of a prefabricated occlusalregistration tray secured to the implants. Its advantage isthat it does not require fabrication of the traditionalrecord base and wax rim, and this step can be carried outat the same appointment as the final impression proce-

dure, which reduces the number of clinical appointments.Design and fabrication of the implant-retained over-

dentures can be carried out in several ways. Despitemuch clinical research conducted on the subject, dentalliterature does not provide definitive answers on alldesign aspects and fabrication techniques of the implant-retained overdentures. In many instances, available re-search is not directly applicable to the clinical settingsbecause of the differences between the individual prod-ucts and fabrication techniques. Taking these limitationsinto account, clinicians and dental technicians have toadhere to sound design principles such as longevity, sim-plicity in fabrication, ease of maintenance and repair, pa-tient friendliness, and cost control.

ConclusionThis article has described an implant-retained

mandibular overdenture design and its fabrication tech-nique. Retention of the overdenture is provided by the 2freestanding implants placed in the anterior region of themandible. The design characteristics included incorpora-tion of the metal-reinforcing framework into the overden-ture and attachment system consisting of prefabricatedstock abutments and hinge-type resilient attachments. Somecontroversies associated with the design and fabrication ofthe implant-retained overdenture also have been discussed.

AcknowledgmentsThe authors would like to thank Darrin Rapoport

BDS, MSD, for the surgical management of the case andKunio Imaizumi for the processing of the dentures.

References1. Carlsson GE. Facts and fallacies: an evidence base for com-

plete dentures. Dent Update. 2006;33:134-136,138-140,142.2. Adell R, Eriksson B, Lekholm U, et al. Long-term follow-up

study of osseointegrated implants in the treatment of totallyedentulous jaws. Int J Oral Maxillofac Implants. 1990;5:347-359.

3. Zitzmann NU, Marinello CP. A review of clinical and technicalconsiderations for fixed and removable implant prostheses inthe edentulous mandible. Int J Prosthodont. 2002;15:65-72.

4. Melas F, Marcenes W, Wright PS. Oral health impact on dailyperformance in patients with implant-stabilized overdenturesand patients with conventional complete dentures. Int J OralMaxillofac Implants. 2001;16:700-712.

5. Awad MA, Lund JP, Dufresne E, et al. Comparing the efficacy ofmandibular implant-retained overdentures and conventionaldentures among middle-aged edentulous patients: satisfactionand functional assessment. Int J Prosthodont. 2003;16:117-122.

6. Bergman B, Carlsson GE. Clinical long-term study of completedenture wearers. J Prosthet Dent. 1985;53:56-61.

7. Lindquist LW, Rockler B, Carlsson GE. Bone resorption aroundfixtures in edentulous patients treated with mandibular fixed tis-sue-integrated prostheses. J Prosthet Dent. 1988;59:59-63.

8. Wright PS, Glantz PO, Randow K, et al. The effects of fixedand removable implant-stabilised prostheses on posteriormandibular residual ridge resorption. Clin Oral Implants Res.2002;13:169-174.

Selection of the appropriate attachmentsystem is not an easy task because

of the large number of available options and continuous introduction of

new designs in the dental market.

Dr Shor can be contacted at alexshor38@hotmail.com.

9. Adell R, Lekholm U, Rockler B, et al. A 15-year study ofosseointegrated implants in the treatment of the edentulousjaw. Int J Oral Surg. 1981;10:387-416.

10. Lekholm U. Clinical procedures for treatment with osseointe-grated dental implants. J Prosthet Dent. 1983;50:116-120.

11. Ortorp A, Jemt T. Clinical experiences of computer numericcontrol-milled titanium frameworks supported by implants inthe edentulous jaw: a 5-year prospective study. Clin ImplantDent Relat Res. 2004;6:199-209.

12. Galindo DF. The implant-supported milled-bar mandibularoverdenture. J Prosthodont. 2001;10:46-51.

13. Zitzmann NU, Marinello CP, Sendi P. A cost-effectivenessanalysis of implant overdentures. J Dent Res. 2006;85:717-721.

14. Zitzmann NU, Sendi P, Marinello CP. An economic evaluationof implant treatment in edentulous patients—preliminary re-sults. Int J Prosthodont. 2005;18:20-27.

15. Attard NJ, Zarb GA, Laporte A. Long-term treatment costsassociated with implant-supported mandibular prostheses inedentulous patients. Int J Prosthodont. 2005;18:117-123.

16. Klemetti E, Chehade A, Takanishi Y, et al. Two-implant mandi-bular overdentures: simple to fabricate and easy to wear. J CanDent Assoc. 2003;69:29-33.

17. Mericske-Stern R, Zarb GA. Overdentures: an alternativeimplant methodology for edentulous patients. Int J Prosthodont.1993;2:203-208.

18. Cordioli G, Majzoub Z, Castagna S. Mandibular overdentureanchored to single implants: a five-year prospective study. JProsthet Dent. 1997;78:159-165.

19. Takanashi Y, Penrod JR, Chehade A, et al. Does a prosthodontistspend more time providing mandibular two-implant overden-tures than conventional dentures? Int J Prosthodont. 2002;15:397-403.

20. Heydecke G, Penrod JR, Takanashi Y, et al. Cost-effectiveness ofmandibular two-implant overdentures and conventional den-tures in the edentulous elderly. J Dent Res. 2005;84:794-799.

21. Takanashi Y, Penrod JR, Lund JP, et al. A cost comparison ofmandibular two-implant overdenture and conventional den-ture treatment. Int J Prosthodont. 2004;17:181-186.

22. Carlsson GE, Kronstrom M, de Baat C, et al. A survey of theuse of the mandibular implant overdentures in 10 countries.Int J Prosthodont. 2004;17:211-217.

23. Feine JS, Carlsson GE, Awad MA, et al. The McGill ConsensusStatement on Overdentures. Montreal, Quebec, Canada. May24-25, 2002. Int J Prosthodont. 2002;15:413-414.

24. Attard NJ, Zarb GA. Long-term treatment outcomes in eden-tulous patients with implant overdentures: the Toronto study.Int J Prosthodont. 2004;17:425-433.

25. Naert I, Alsaadi G, van Steenberghe D, et al. A 10-year random-ized clinical trial on the influence of splinted and unsplintedoral implants retaining mandibular overdentures: peri-implantoutcome. Int J Oral Maxillofac Implants. 2004;19:695-702.

26. Naert I, Alsaadi G, Quirynen M. Prosthetic aspects and patientsatisfaction with two-implant-retained mandibular overden-

tures: a 10-year randomized clinical study. Int J Prosthodont.2004;17:401-410.

27. Timmerman R, Stoker GT, Wismeijer D, et al. An eight-yearfollow-up to a randomized clinical trial of participant satisfac-tion with three types of mandibular implant-retained overden-tures. J Dent Res. 2004;83:630-633.

28. Oetterli M, Kiener P, Mericske-Stern R. A longitudinal studyon mandibular implants supporting an overdenture: the influ-ence of retention mechanism and anatomic-prosthetic vari-ables on periimplant parameters. Int J Prosthodont. 2001;14:536-542.

29. Watson GK, Payne AG, Purton DG, et al. Mandibular overden-tures: comparative evaluation of prosthodontic maintenanceof three different implant systems during the first year of serv-ice. Int J Prosthodont. 2002;15:259-266.

30. Cune M, van Kampen F, van der Bilt A, et al. Patient satisfac-tion and preference with magnet, bar-clip, and ball-socketretained mandibular implant overdentures: a cross-over clini-cal trial. Int J Prosthodont. 2005;18:99-105.

31. Walton JN. A randomized clinical trial comparing two mandibu-lar implant overdenture designs: 3-year prosthetic outcomesusing a six-field protocol. Int J Prosthodont. 2003;16:255-260.

32. Gulizio MP, Agar JR, Kelly JR, et al. Effect of implant angula-tion upon retention of overdenture attachments. J Prosthodont.2005;14:3-11.

33. Walton JN, Huizinga SC, Peck CC. Implant angulation: ameasurement technique, implant overdenture maintenance,and the influence of surgical experience. Int J Prosthodont. 2001;14:523-530.

34. Shor A, Shor K, Goto Y. Implant-retained overdenture design forthe malpositioned mandibular implants. Compend Contin EducDent. 2006;27:411-419.

35. Phillips K, Wong KM. Space requirements for implant-retainedbar-and-clip overdentures. Compend Contin Educ Dent. 2001;22:516-522.

36. Lee CK, Agar JR. Surgical and prosthetic planning for a two-implant-retained mandibular overdenture: a clinical report. JProsthet Dent. 2006;95:102-105.

37. Pasciuta M, Grossman Y, Finger IM. A prosthetic solution torestoring the edentulous mandible with limited interarchspace using an implant-tissue-supported overdenture: a clini-cal report. J Prosthet Dent. 2005;93:116-120.

38. Boudrias P, Chehade A. Two-implant overdentures with ballattachments: a step-by-step approach. In: Feine JS, Carlsson GE,eds. Implant Overdentures: The Standard of Care for EdentulousPatients. Carol Stream, Ill: Quintessence Publishing Co;2003:129-143.

39. Shifman A, Marshak B. Implant-retained mandibular overden-tures: a simplified, cost-effective treatment approach. QuintessenceInt. 1994;25:825-828.

40. Dominici JT, Kinderknecht KE, Patella-Clark E. Clinical pro-cedure for stabilizing and connecting O-ring attachments to amandibular implant overdenture. J Prosthet Dent. 1996;76:330-333.

Compendium • February 2007;28(2):80-89

(#16151) Reprinted from the February 2007 issue of Compendium. © 2007 Ascend Media LLC.For more information about reprints from Compendium, contact PARS International Corp. at 212-221-9595.