Using Contemporary Concepts of Occlusion and ... - Dentropolis

Using ContemporaryConcepts ofOcclusion andRetention forImplant-SupportedComplete DentureRestorationsGeorge Priest, DMD and Ernest Caragol, CDTGeorge Priest, DMDErnest Caragol, CDTncorporating dental implants for theedentulous patient significantly improvesdenture base stability, thus increasing thepatient’s ability to transmit greater occlusalforces during chewing, swallowing and,particularly, clenching/bruxing to a level fargreater than with conventional dentures.Therefore, the importance of occlusion cannot be understated for the long term successof dental implants supporting removableimplant supported prostheses. Thetechnician and clinician are therefore facedwith the challenge of determining the idealposterior denture tooth form and occlusalscheme that would best satisfy thefunctional and esthetic requirements of thepatient, without causing undue stress onthe implants and the associated oralstructures.Several authors 1,2,3 have accepted theconcept of lingualized (lingual contact)occlusion as the contemporary occlusalscheme of choice for implant supportedremovable denture restorations. Some ofthe many advantages of lingualizedocclusion as it applies to implant supportedremovable restorations include; occlusalforces that are centered over the ridge crestin centric relation, effective transfer offorces more “lingual” to the ridges duringworking side excursions (Fig. 1) andminimized occlusal disharmonies createdfrom errors in jaw registrations, dentureprocessing changes and/or eventual settlingof the denture base. Additionally, the“mortar and pestle” type of occlusionminimizes the occlusal contact area andprovides more efficient bolus penetration,while minimizing destructive horizontalforces. Furthermore, such an occlusalscheme eliminates the preciseintercuspation of anatomic teeth that oftencomplicates the setting and equilibration ofdenture teeth.Fig. 1To this end, the SR Ortholingual toothmould is specifically designed to satisfy thebiomechanical requirements of lingualizedCJDT • Spectrum January/February 2003

Fig. 10Fig. 2Fig. 3Shallow MandibularCusp AnglesFig. 4 Fig. 5occlusion (Fig. 2). The tooth designprimarily consists of a dominant maxillarylingual cusp (Fig. 3) and an uncomplicatedmandibular central fossa (Fig. 4). Themaxillary lingual cusps can articulateanywhere along the mandibular centralfossa, while the maxillary buccal cusps areintentionally left out of contact. This leavesthe maxillary lingual cusps as the onlycentric holding contacts, which helps tostabilize the upper and lower dentures andminimizes the number of tooth contacts.(Fig. 5).The following case presentationhighlights the selection, set-up andequilibration of the SR Ortholingual posteriordenture tooth mould that easily satisfies thetenants of lingual contact occlusion. Inaddition, a uniquely designed implantoverdenture retention system (Kugel-B barimplant system/Georgia Dental Laboratory)is described.Case PresentationAn 81-year-old female who had beenedentulous for 25 years presented forreplacement of her missing teeth. As part ofthe treatment plan, four implants (ImplantInnovations, Inc.) were placed six monthsprior to obtaining a preliminary alginateimpression. A custom retentive bar wasfabricated and placed using the Kugel Bretentive bar pattern (Fig. 6). Custom trayswere border molded with a hydrophilicmonophase vinyl polysiloxane materialFig. 6(Virtual) and washed with the samemonophase material. Customary centricand vertical jaw registrations were madeusing denture base wax rims.SR Ortholingual posterior denture teethwere selected based on their specific design,which facilitates the establishment of alingualized (lingual contact) occlusalscheme. The clinician and laboratorytechnician reviewed the treatment plan andthe patient's aesthetic requirements in orderto select the appropriate tooth arrangement,alignment and shade.After receiving the occlusal registrationfrom the doctor, the master casts weremounted on the Stratos 200 articulatorusing the horizontal guide to orient thelower cast to an average Bonwill position.The six anterior maxillary teeth were setaccording to the markings on the occlusalrim: midline, cusped line, high lip line, andincisal edge position. The six anteriormandibular teeth were positioned tocoordinate with the maxillary anterior.The posteriormandibular teeth werepositioned using atooth set-up template(2D template) (Fig. 7)which is a componentof the Stratos 200Fig. 7articulation system.This particulartemplate is simple to use, since it is attachedto the articulator (Fig.s 8 & 9). Hand-heldtemplates can also be used but aresomewhat more difficult to manage. TheFig. 8Fig. 9Fig. 11template assures that the mandibularposterior teeth are set bilaterallysymmetrical on a predetermined anteroposteriorand mesiolateral curve. Thisgreatly facilitates the positioning of themaxillary posterior teeth and thesubsequent balanced occlusion. TheSR Ortholingual tooth mould easily workswith a template, since each cusp tip isdesigned to contact the template (Fig. 10).This allows the teeth to be positioned rathersimply and quickly.The case was prepared for a wax try-in,(Fig. 11) and returned to the laboratory withphotos of the intra-oral tissue andinstructions for acrylic characterization. Thedentist specified one of the following skinand hair combinations corresponding to thepatient's appearance: fair skin/light haircolor; olive skin/dark hair color; ebonyskin/dark brown/black hair. Based thisinformation, the technician selected theappropriate characterization scheme andtinted the following areas of the denturebase: interproximal spaces to simulatevascularity; root eminences, especially thecanine eminence to create a blanched effect;and the labial frenum. The stains areinternally colored, methymetharylate-based40 CJDT • Spectrum January/February 2003

Fig. 13Fig. 14Fig. 12co-polymer (Kayon denture tinting kit) andwill not alter the physical properties of thedenture resin, fade or change with time.Processing was completed using theSR Ivocap injection system (Fig. 12) Thissystem is preferred due to its capacity tocompensate for the polymerizationshrinkage that occurs during conventionalacrylic resin processing. A second processingprocedure was required for the addition of aheat cured silicone liner in the area of theKugel B retention bar (fig. 13). Thisprocedure provided the denture withpredictable retention and easy maintenancewhen compared to other conventionalretentive attachment systems. This retentivebar system is patented as the Georgia DentalLaboratory Kugel-B liner Process. To obtainmore information on this process, pleaserefer to the end of the article.Typically minimal adjustments wererequired at the denture insertionappointment. The lingual contact occlusalscheme provided a rather simplistic methodof adjusting the occlusion after processing.The re-establishment of lingual cuspcontacts to the central fossa of themandibular teeth was easy to visualize andquite simple to adjust. Adjustments can bedone chairside or by mounting the denturesusing a new centric record. The processedsilicone provided reliable retention and easyinsertion as well. The results were maximumesthetics, minimal adjustment, excellentfunction and predictable retention (Fig. 14).ConclusionLingualized (lingual contact) occlusion wasthe occlusal scheme of choice for thisimplant supported restoration due to themany advantages previously stated. TheSR Ortholingual tooth mould from IvoclarVivadent has provided a tooth form that isspecifically designed for this concept andhas greatly facilitated the establishment ofthis desired occlusal scheme withoutsacrificing esthetics or function. A uniqueoverdenture retentive bar system (Kugel Bbar implant system) was also described.References1. Lang BR, Razzoog ME: A practicalapproach to restoring occlusion foredentulous patients: Part 1. Guidingprinciples of tooth selection. J ProsthetDent 50:455-458, 19832. Lang BR, Razzoog ME: Lingualizedintegration: tooth molds and anocclusal scheme for edentulous implantpatients. Implant Dent (3): 204-211,19923. Garg A, Practical Implant Dentistry,Taylor Publishing Company, 199642 CJDT • Spectrum January/February 2003