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New Standard of Care | Dental Implant | Dentures

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  ABSTRACT: While most implant-based treatment has histori-callyfocusedon fixedprosthetic tooth replacement,the multitude of benefits to the edentulous population from implant overdentures isoverwhelming in terms ofimproved function,emotional stability, physical health,and esthetics.Although there still remains a lack of consistency in terms oftechniques,prosthetic design,and attachment systems,theseaspects have been proven less important to successful outcomes than oncethought.This article presents a simplified approachto patient evaluation,treatment planning decisions,attachment selection,and technique. W  hile most implant-based treatment has historically focused on fixed prosthetic tooth replacement, 1 themultitude ofbenefits to the edentulous populationfrom implant overdentures is overwhelming in terms ofimprovedfunction,emotional stability,physical health,and esthetics.Properevaluation and treatment planning ofthe fully edentulous patienthas been shown to result in an improved quality oflife for patients 2,3 and predictable results leading to clinical success.The indicationfor a fixed prosthesis may be limited due to inadequate quantity and structure ofthe bone.Enhancement ofesthetic appearanceand facial morphology through replacement oflost hard and softtissues may be proven easier,ifnot more effective,with removableoverdentures than with conventional fixed prosthesis,with possi-bly decreased costs and less surgical intervention.Generally,more implants are required to support a fixedprosthesis than an overdenture.Other factors to consider in-clude the health ofthe patient,his or her ability to undergografting procedures,and cost. 4 There has been an abundance of literature presenting a variety oftreatment options,case reports,and clinical techniques over the past 20 years,but more recently there has been general agreement about the treatment protocolsand long-term documented benefits ofimplant overdentures.This treatment option has become the most rewarding care pro-vided in this author’s clinical practice,and with increased lifeexpectancy,its full impact on clinical practice is yet to be real-ized.Although there still remains a lack ofconsistency in termsoftechniques,prosthetic design,and attachment systems,theseaspects have been proven less important to successful outcomesthan once thought.This article presents a simplified approach topatient evaluation,treatment planning decisions,attachment FIGURE 1A Extensive resorption of the maxilla due to tooth loss resultsin a lack ofadequate horizontal support ofthe orafacial soft tissuesin a male patient. FIGURE 2 Ongoing loss ofmaxillary and mandibular basal bone leads to decreased vertical dimension and height offace from overclosurein a female patient.  A Implant Overdentures:A New Standard ofCare for Edentulous Patients—Current Concepts and Techniques ROBERT C.VOGEL,DDS SERIES 1 Dental Implants 1  Article Reprint- FUNCTIONAL ESTHETICS & RESTORATIVE DENTISTRY: Series 1,Number 2  selection,and technique.Whatare agreed upon are the specificindication for this treatment and the benefit derived.First,there is a need to appreciate the sequelae oftooth lossand associated benefits ofimplant overdentures,followed by patient evaluation,treatmentprotocols,and clinical technique.Formany years clinicians realized that placement ofendosseousosseointegratedimplants under a removable prosthesis wouldprovide the definitive advantages ofbone preservation, 5 pros-thetic retention,stability,and a degree ofocclusal supportresulting in improved function,facial esthetics,and comfort.More recently,comprehensive and ongoing studies conducted atMcGill University have documented the improved nutrition,psychosocial status,and quality oflife that have been gainedthrough the use ofoverdenture treatment. 6,7 The use ofim-plants also provides a predictable solution for patients and prac-titioners to the problems associated with conventional denturesby resolving functional and esthetic compromises.The sequelae oftooth loss and edentulous arches is residualridge resorption both in the horizontal and vertical direction.Thisongoing loss ofhardand soft tissue is most noticeable in the lossoforofacial support:facial esthetics,phonetics,and the collapse of vertical dimension.This leads to an aging appearance due to thelack oflip support and decreased facial height (Figures 1 and 2).Concurrent with these changes in facial structures are impairedoral function,pain,insufficient retention,and instability ofcon-ventional dentures,as well as nutritional and psychological changes.Many patients seeking resolution to chronic soreness ofload-bearing tissues and nonstable or retentive dentures will enjoy increased esthetics,function,comfort,and psychological benefitsfrom implant overdentures,without the need for more extensivefixed restorations. 8,9 PATIENT EVALUATION:MAXILLOFACIAL RELATIONSHIP Upon evaluation ofthe edentulous (or soon to be edentulous)patient,facial esthetics and the amount ofextraoral soft tissuesupport ofthe lips and associated structures will become an initialguideline to treatment options.Ifhorizontal loss ofhard and softtissue through resorption,disease,or trauma is so advanced thatteeth need to be placed far anterior to the residual ridge in orderto provide adequate facial support,then an overdenture (ie,acrylic base and flanges) can provide replacement ofthese struc-tures (Figure1B).Alternatively,bone graftingprocedures can be per-formed to augment the missing tissues,but limitations must beevaluated.Limiting factors in grafting procedures include ade-quate blood supply,patient health,and finances.When evaluatingvertical loss ofhard and soft tissues,the resultant interarch spacemust be determined in order to see ifexcessive crown-to-implantratio and biomechanical forces will preclude a conventionalimplant-supported fixed restoration (Figure 3).While graftingprocedures have radically changed how we treat patients,there arelimitations to the amount ofvertical augmentation possible.Any successful overdenture treatmentbegins with the understanding that we mustconform to standard full-denture fabricationprinciples.These include ideal border adapta-tion and extension and full-denture occlu-sion. 10 Through proper articulation anddenture tooth set-up,all parameters offinaltreatment success can be evaluated.An idealtooth set-up and try-in will quickly allow evaluation ofesthetics,phonetics,and sup-port,as well as the critical determination of ridge position relative to the proposed pros-thesis prior to surgery.The set-up will then beused to guide ideal implant position,since themost critical factor in overdenture implantplacement is that implants emerge well withinthe confines ofthe denture.Ifan existing denture is available anddetermined to have adequate tooth position,this can become the surgical guide for im-plant placement.Ifa denture with adequateocclussal and esthetic parameters is not avail-able,then a new ideal set-up is necessary toavoid implant placement in a less-than-ideal FIGURE 3 Excessive interarch space due to advanced bone loss is evaluated through articulation prior to ideal esthetic and functional set-up ofthe denture teeth. FIGURE 1B View ofthe patient seen in Figure 1A following place-ment ofa maxillary overdenture. Note the return offacial estheticsthrough support ofthe soft tissues.  B Proper evaluation and treatment planning ofthe fully edentulouspatient has been shown to result inan improved quality oflife forpatientsand predictable resultsleading to clinical success. ESSENTIALS 2  Article Reprint- FUNCTIONAL ESTHETICS & RESTORATIVE DENTISTRY: Series 1,Number 2  or even nonusable position.Often theauthor duplicates the wax set-up in clearacrylic prior to final processing to serveas a surgical guide (Figures 4A and 4B).The risks ofproceeding with implantplacement prior to tooth set-up and try-in are compromised space for overden-ture attachments,inadequate acrylicthickness,and unforeseen laboratory andcomponent costs necessary to correctpoor angulation. EVALUATION OF RIDGE While the majority ofpatients will realize awealth ofbenefits from the two-implantmandibular overdenture,close evaluation of the residual ridge will provide information about the ideal num-ber and position ofimplants,as well as abutment and attach-ment selection.Single,non-splinted implants can provide idealretention ofthe prosthesis to prevent vertical and lateral displace-ment.However,ideally the majority ofocclusal support is provid-ed by the residual ridge and not the implants.The primary goal of any overdenture attachment is to retain the appliance in positionwith a minimal amount ofmovement.Traditional overdentures are classified as implant-retained  and tissue-supported  prostheses 11 (Figures 5A and 5B).Ifthe patient’sresidual ridge is inadequate to provide the majority ofvertical occlusalsupport in function,as in cases ofextreme “knife-edge”or chronicmucosal soreness due to the nature ofthe tissues,then more implantsor splinting ofthe implants may be indicated to provide moreimplant support and decreased loading ofthe tissues. 12 The benefitofplacing three to four implants (as opposed to only two) is theability to ease the load on a less-than-ideal ridge,decreasingmucosal bearing areas during occlusal function.Additional implantsmay alsobe more desirable when fixtures ofreduced length ordiameter are necessary due to limited bone volume.The benefit ofsplinting implants (ie,bar restorations) is potentialdistribution ofthe forces to more osseointegrated surfaces to sharethe load.The primary reason for splinting is to enable the labora-tory to compensatefor significant malaligned or poorly posi-tioned implants by fabricating a custom substructure.Still,the majority ofpatients will greatly benefit from two tofour non-splinted mandibular implants to provide ideal retentionand some level ofocclusal support.Numerous studies have shownequal outcomes in long-term implantsurvival in mandibular overdenturesregardless ofsplinting. 20 Many fac-tors prove overwhelmingly in favor of individual non-splinted implants,such as decreased cost,decreasedspace requirement inside the denture,and improved access for hygiene.Theindividual non-splinted approachprovides the most ideal outcome withthe greatest cost effectiveness andgreatest efficacy oftreatment for themajority ofedentulous patients.There are several attachments available to provide retention of the prosthesis to the implants.Numerous studies over the yearshave shown that many designs work well.However,in order toprovide a guide to attachment selection,numerous factors shouldbe considered.First,all attachments are either rigid or resilient.Rigid attachments restrict rotational movement and provide only alimited path ofangle insertion,while resilient attachments allow varying amounts ofrotation and angulation correction.In situa-tions where implants are even minimally nonparallel,a resilientattachment will consistently show less friction,wear,and breakage.Considering that patients frequently bite appliances into place,this resiliency will also prevent premature wear and breakage.Clearly the largest overdenture complication and maintenanceconcern relates to attachment adjustment and replacement, 14,15 aswell as fracture from the prosthesis.These can be significantly minimized through proper attachment selection and use of resilient attachments. 16 A resilient connection to the dentureshould allow reduced loading ofthe abutments in so far as thedegree ofmovement takes into account the compressibility (ie,resilience) ofthe mucosa.The greatest portion ofthe occlusalforces are thus adsorbed directly by the alveolar ridges. 13 Thereare attachment systems that allow angulation correction ofup to20 degrees per implant (40 degrees for two divergent implants)within a resilient range. a Other factors in attachment selection include height ofthe attach-ment to minimize space requirements inside the denture and decrease FIGURES 4 A,B  A clear surgical guide fabricated by duplicating the ideal set-up ensures implant placement within the confines ofthe final denture base.  A B FIGURES 5 A,B Views ofan implant-retained/tissue-supported two-implant overdenture system.  A B a Locator,Zest Anchors,Escondido,CA ESSENTIALS 3  Article Reprint- FUNCTIONAL ESTHETICS & RESTORATIVE DENTISTRY: Series 1,Number 2  potential fracture due to inadequate acrylic thickness,and housingswith replaceable matrices.The advantage ofa housing for theattachment is that with any need to change the retentive component,it is not necessary to re-cure the attachment into the denture base.Based on the above factors and clinical experience,the author’sattachment selection is a resilient,non-splinted,prefabricatedattachment ofminimal height with easily replaceable retentive com-ponentsofvarying forces that include a selection ofcuffheights toemerge through the tissue ofa subgingivally placed implant. a Theuse ofindividual resilient attachments allows implant and toothoverdenture abutments to be used in combination,as in the caseofa remaining healthy mandibular cuspid that was endodontically treated and placement ofa “root”overdenture abutment.As previously mentioned,the fabrication ofa bar allows thelaboratory to correct significant implant malalignment,which isoften seen in the maxilla due to the resorptive pattern ofthe basalbone.This suprastructure allows attachments to be cast,soldered,or welded to the bar to provide a common path ofinsertion,as wellas relocate the attachment system within the confines ofthe den-ture base because ofoften buccal-emerging implants.The otherpotential advantage ofsplinting throughthe use ofa bar or telescopic copings isdistribution ofvertical forces to more im-plants so that rotational torqueoftheimplants is resisted under occlusal load-ing in cases where there is limited buccalbone volume and encroachment on theresidual buccal plate.Maxillary overdenture implants tendto be angled,placed in less dense bone,and shorter due to the nature ofresorp-tive patterns and sinus expansion.Moresignificant to the decreased stress transferin maxillary implants is the amount of palatal coverage offered by the applianceto provide greater tissue support. 15 Maintaining palatal coverage to assist inthe potential reduction ofload to the im-plants may be recommended in instancesofreduced implant support due to thequality ofintegration,number ofimplants,or compromised implant positioning andlocation.This adheres to the primary premise ofan “implant-retained and tis-sue-supported”appliance.The down side ofbars to be consid-ered is the added space required insidethe denture, 17 hygiene difficulties,andadditional cost involved.Passivity offit of  FIGURE 6D Housings a were placed to verify the full seating ofthe final prosthesis,without interference from attachments or housings. FIGURE 6A Four regular neck implants b were placed anterior to the mental foremen with ideal distribution.  A B FIGURE 6B  Abutments a were selected based onthe depth ofthe peri-implant sulcus,which wasobtained by measuring the distance from the topofthe implant to the highest point ofsoft tissue(eg,transmucosal cuffheights of1 mm to 6 mmwere available). FIGURE 6E  The final prosthesis was prepared  for incorporation ofthe housings. FIGURE 6F  “Vent Holes”were placed in the area ofthe attachments to allow the escapeofexcess material and prevent complete seating on the tissues.  E  FIGURE 6G View ofhousings with black process-ing males,which were tacked in place with acrylic by means ofthe patient maintaining a mediumbiting force in centric while the material cured. FIGURE 6C  Block out rings were placed to prevent material from flowing into undercuts.Special attention must be given to block out any additional undercut areas to prevent “locking into”these areas. C DF G  b Straumann USA,LLC,Andover,MA ESSENTIALS 4  Article Reprint- FUNCTIONAL ESTHETICS & RESTORATIVE DENTISTRY: Series 1,Number 2
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