Implant-supported overdenturesoffer many practical advan-tages over conventional com-

plete dentures and removable partialdentures. These include decreasedbone resorption; reduced or elimi-nated prosthesis movement; betteresthetics; improved tooth position;better occlusion, includingimproved occlusal load direction,increased occlusal function andmaintenance of the occlusal verticaldimension. In addition, implant-

Implant-Supported Overdentures:The Standard of Care forEdentulous Patients

From Our Officeto Yours...

Implant-supported overden-tures have been a common treat-ment for edentulous patients forthe past 20 years and predictablyachieve good clinical results. Manypatients, especially those who areuncomfortable with dentures,enjoy the additional retention andsupport implants provide for theirdentures.

The implant-supported over-denture has been accepted as thestandard of care for fully edentu-lous patients and should be thefirst choice of treatment for theedentulous mandible.

In this issue of ThePerioDontaLetter, we discuss themany advantages of implant-sup-ported overdentures over conven-tional dentures and the survivaland success rates of implants sup-porting overdentures in the maxillaand mandible, along with the vari-ous factors which influence them.

As always, we welcome yoursuggestions and comments andare available to team treatmentplan implant-supported overden-tures for your patients.

supported overdentures improvephonetics, the patient’s psychologi-cal outlook and quality of life.

Conventional dentures relyupon the residual alveolar ridge andmucosa for support and retention.Many patients have problems adapt-ing to their complete dentures, espe-cially to the mandibular prosthesis.The widespread use of dentureadhesives is one indication thatthese prostheses generally provideinadequate comfort and function.

Figure 1. Four implantswere placed ina moderate toseverelyresorbedmandible inpreparation foran overdenture.

PDL tm

Summer

I. Stephen Brown, D.D.S. 220 South 16th Street, Suite 300, Philadelphia, PA 19102 (215) 735-3660

The Brown

I. Stephen Brown, D.D.S., Periodontics & Implant Dentistry

denture are lack of retention or stabil-ity, poor function and speech, tissuesensitivity and soft tissue abrasions.

Less Bone Resorption

One advantage of implant-sup-ported full bridges and dentures is thatthey function like tooth roots, whichpreserves jaw bone. Dental implantsintegrate with the jawbone and dra-matically reduce the rate of bone lossattributed to conventional dentures.

Edentulism is characterized byatrophy of the jaw bone. Studiesshow rapid resorption -- an average of4mm -- occurs during the first yearafter tooth loss and thereafter decreas-es to 0.5mm per year. Over a five-year period, 5.2mm of vertical boneheight will be lost under completedentures. Bone loss under completedentures continues with the mandibleexperiencing a fourfold greater verti-cal bone loss than the maxilla.

In contrast, Schwartz-Arad et alfound that 70 percent of their patientswith implant-supported overdentureslost less than .2mm bone in the firstyear. Misch found that only .6mm. ofbone will typically be lost over a five-

Studies show implant-support-ed overdentures have superiorretention to conventional dentures.Regard-less of the type of attach-ment system used -- bar, ball ormagnet -- patients are significantlymore satisfied with implant-sup-ported overdentures than with con-ventional dentures.

Patients find implant-supportedoverdentures significantly more sta-ble and rate their ability to chew awider variety of foods as significant-ly easier, thus improving their nutri-tional state. Furthermore, they findimplant-supported overdenturesmore comfortable and speech easier.

The implant-supported overden-ture may reduce the amount of softtissue coverage and extension of theprosthesis which is especiallyimportant for new denture wearersor those who have low gaggingthresholds.

The 2002 McGill ConsensusStatement cites studies of severalpopulations showing that patientswith implant-supported overden-tures enjoy a significantly higherquality of life than those who wearconventional dentures. The McGillStatement concluded there is over-whelming evidence that the restora-tion of the edentulous mandible witha conventional denture is no longerthe most appropriate choice of pros-thetic treatment. The implant-sup-ported overdenture HAS BECOMEthe standard of care.

Numerous studies show cumu-lative success rates for all implant-supported overdentures at 95.4 per-cent, with implant-supported over-dentures placed in the mandibleenjoying a slightly higher successrate than implant-supported over-dentures placed in the maxilla.

The major indications for amandibular implant-supported over-

Figure 2. Locator attachmentswere placed in the implants andthe overdenture.

Figure 3. Final placement of the removableprosthesis resulted in a very attractive estheticresult and excellent function for the patient.

Figure 4. A final radiograph shows implantplacement and apparent osseointegration.

PerioDontaLetter, Summer

year period and long-term resorptionmay remain as low as .1mm per yearin patients with overdentures support-ed by multiple implants.

Crestal bone loss (CBL) aroundimplants supporting overdenturesappears to be affected by factors suchas location (maxilla or mandible),attachment system, and number ofimplants supporting the overdenture.

Location in the maxilla or themandible appears to most influenceCBL. Studies show implants in themandible exhibit less CBL than im-plants in the maxilla, which could beattributed to the difference in bonequality in the maxilla and the man-dible and to different loading cir-cumstances.

The maxilla normally has lessdensity and quantity of bone than themandible. The resorbed mandibleusually has dense compact bone withan oak-like quality or a combinationof thick porous compact bone on theoutside and course trabecular bone onthe inside. Because the percentage ofbone at the implant interface is 70 to80 percent, mandibular implants arethe most successful.

The type of bone most common-ly found in the long-term edentulous

maxilla is a combination of thinnerporous compact bone on the outsideand fine trabecular bone on theinside, or fine trabecular bone withvery light density and little or nocortical crestal bone. The amount ofbone at the implant-to-bone interfaceranges from 50 percent down to 25percent making maxillary implantsless successful.

Timing of implant loadingappears to be a factor in the success ofimplant-supported overdentures.Immediate loading techniques, anewer approach to implant-supportedrestorations, depends on many factorsand requires precise coordinationbetween the periodontist and therestorative dentist.

Recently, more two-implantmandibular overdentures are beingplaced as an affordable alternative toprostheses requiring several implants.The choice of implant site for theseoverdentures should be governed bythe quantity, quality and volume ofavailable bone, along with the sizeand curvature of the anterior arch.

As it is with all implants, the suc-cess rate of implant-supported over-dentures was lower among patientswho used tobacco. CBL did not

appear to be affected by implantlength, diameter or surface.

The study showed implants withincreased CBL initially regarded asfailing implants could become suc-cessful after an extended follow-upperiod of more than three years.Qyuirynen et al found that the pro-gression of bone loss around implant-supported mandibular overdenturesdecreases with time.

Resorption also causes changesin bone shape making it necessary tocontinually repair and remake con-ventional dentures. These changesare indications for the success ofimplant- supported overdentureswhich do not require continualrepairs and remanufacturing.

Greater ProsthesisStability

The greater stability of animplant-supported overdenture de-rives from the mechanical attach-ment of the implant support systemretaining the restoration.

A mandibular denture may move10mm during function. Under theseconditions, predetermined occlusal

Figure 5. Four implants were placed to attach afixed bar.

Figure 6. Three clips were placed in the overden-ture for retention.

contacts and the control of masticato-ry forces are nearly impossible.Implants stabilize the prosthesis andthe patient is able to consistentlyreproduce a determined centricocclusion. Lateral forces may causea horizontal movement of a conven-tional prosthesis and cause soft tissueabrasions and accelerated bone loss.An implant-supported overdenturelimits lateral movements and conse-quently minimizes soft tissue trauma.

In addition, complete denturesoften move vertically duringmandibular movement and speech.The contraction of the mentalis,buccinator, or mylohyoid musclesmay lift the denture off the soft tis-sue. As a consequence, the teethmay touch during speech and causeclicking noises.

The implant-supported overden-ture remains in place during mandibu-lar movement which allows thetongue and perioral musculature toresume a more normal function sincethey are not required to controlmandibular denture movement.

While prosthesis retention hasbeen found to be good for magnets,balls and clips, bars were the mostretentive. Studies have shown ballsexperienced more complications.

Overdenture bars may be cement-ed or screw-retained. Cemented barspresent the advantages of more pas-sive fit, reduced cost and an easier barimpression technique.

Jemt et al showed a decrease inocclusal force when the bar connect-ing implants was removed and attrib-uted it to the loss of support, stabilityand retention.

The prosthesis support and rangeof motion should be part of the initialdiagnosis. Proven, simple, pre-

dictable and cost-effective deviceslimited to a minimum of hardwaremay present the best options. Themore sophisticated the attachment, themore complex the fabrication andmaintenance procedures.

Better Esthetics, ToothPosition and Occlusion

In severe resorption cases,implant-supported overdentures maybe more esthetic than a fixed restora-tion. Bone loss dictates the appear-ance of the inferior third of the face.An implant-supported overdentureprovides improved support for the lipsand soft tissues of the face allowingthe teeth to be the same length as nat-ural teeth. When there is marked lossof alveolar height, the teeth on a con-ventional fixed restoration will bevery long.

The presence of a large labialflange in a conventional denture mayresult in exaggerated facial contoursfor the patient with recent extractions.Implant-supported prostheses do notrequire as great a labial extension oras much extended soft tissue coverageas is necessary for a conventional den-ture. An implant-supported overden-ture can provide the soft tissue supportto the facial features often required fora patient with advanced bone loss.

Traditional tooth-supported over-dentures must rely on the remainingteeth to support the prosthesis. Thelocation of these natural abutments ishighly variable and they are oftencompromised from past bone lossassociated with periodontal disease.

This is not the case with implant-supported overdentures. For implant-supported overdentures, the implants

may be placed in the anterior posi-tions of choice. The number, location,superstructure, design and prostheticrange of motion can be predeterminedand based on a patient’s expressedneeds and desires as opposed to con-ventional, fixed restorations whichmay have to be placed in a specificmesiodistal location because the pros-thesis does not completely cover theabutment.

Misch found the maximumocclusal force of a patient with den-tures may improve 300 percent withan implant-supported prosthesis. Thisimproves the chewing efficiency ofpatients with an implant-supportedoverdenture by 20 percent over thebite strength of patients with a con-ventional denture. Misch also cites astudy of chewing efficiency compar-ing complete denture wearers withimplant-supported overdentures.Patients with conventional denturesneeded 1.5 to 3.6 times the number ofchewing strokes as patients withimplant-supported overdentures.

Improved Maintenance

Hygiene conditions and homemaintenance procedures are improvedwith an overdenture compared with afixed prosthesis. The overdenturemay be extended over the abutmentsto prevent food entrapment duringfunction.

Professional maintenance is alsoimproved as peri-implant probing isdiagnostic and easier around a bar.

We hope this review of the signif-icant advantages implant-supportedoverdentures offer over conventionaldentures has been helpful to you intreatment planning for youredentulous patients. PDL tm

I. Stephen Brown, D.D.S. 220 South 16th Street, Suite 300, Philadelphia, PA 19102 (215) 735-3660