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ePaper created 2015-03-07, 18:13:20 | version 1.33.01
case report _ use of CBCT I tures to obviate injury. Ideally, increased stability of the template, and the placement of the guide tube closer to the top of the implant, should result in a higher degree of accuracy. When evaluating potential dental implant recep- tor sites in the anterior maxilla, posterior maxilla, anterior mandible, or posterior mandible, it is imper- ative that the information derived from the CT/CBCT scanbeproperlyevaluatedinallviewsaffordedbythe software.Implantplacementintheposteriormandible can offer unique challenges. These include lingual undercuts,proximitytothemandibularcanal,quality of bone, reduced alveolar support, and limitations of interarchspace.Recently,differencesinthemorphol- ogy of the posterior mandible have been elucidated.3 The mandibular premolar areas have more caudal di- vergencethanthemolarareas,whichtendtobemore parallel. Greatest variations in buccal and lingual width seem to vary most at 4mm apical to the bony crest.Moreover,malestendtohavewiderridgesthan females, whereas age did not seem to be a significant factor. _Case report A 75-year-old female patient presented with an existingmandibularcompleteoverdenture,supported by three mandibular implants (Straumann) with Lo- catorabutments(Zest,ZestAnchors)(Fig.1)Itwasthe patient’s desire to have a fixed restoration if possible. After a clinical examination, radiographs, and CBCT scan, it was determined that six additional implants couldbeplacedsothatafixedrestorationcouldbefab- ricated. Four of them were placed in the posterior mandibleandtwootherintheanteriorregion.Thenew implants,locatedintheposteriormandible,hadcom- promisedalveolarboneheightandwereincloseprox- imitytothemandibularcanal.Therefore,theneedfor additional stabilization of the guide, beyond that de- rivedfromthebonesupport,wasparamount.Togain therequiredstabilization,aplanwasdevelopedtouse the pre-existing implants with the original Locator abutmentsasamethodofsecuringabone-supported template to increase surgical accuracy. Rathi et al presented a report in which Locator attachments were utilized to stabilize a guide while transitioning a patient from an over-denture to a fixedprosthesisusingan‘AllonFour’protocol.4 While that article highlights the utility of such a procedure, the current clinical case report underscores the need to ensure the stability of the template when the pro- posed implant sites are in close proximity to vital structures. The patient revealed a history of bruxism, which accelerated the loss of retention of the nylon inserts (Locator males), rendering her prosthesis ineffective during function, and required frequent replacement. The need for a completely implant supported fixed restoration became apparent, and the patient was motivated to proceed with the diagnostic phase. The conventionaltreatmentoffiveimplantsbetweenthe mentalforamentosupportafixed-hybridrestoration with a posterior cantilever would not have been acceptable due to the possibility of overloading the implants, given the history of bruxism. Therefore, it was determined that posterior implants were neces- sarytohelpdistributetheloadforafixedrestoration. Whenimplantsareplaceddistaltothementalforamen, the issue of mandibular flexure must be respected5, although this affects a very small percentage of pa- tients.Toaccommodatetheclinicalpresentationand the patient desires, a fixed-type implant-supported Figs. 2a–d_Cross-sectional images of the three existing Straumann implants and the intended abutment projections with superimposed implants: original implant (a); mandibular left first premolar (b); mandibular right central incisor (c); and mandibular left first premolar (d). Fig. 3_Demonstrates a simulated implant within the receptor site with a Locator abutment as selected from the software library of implants and abutments (DENTSPLY Implants) and superimposed on the mandibular 3-D reconstructed volume to aid in the planning process. I 11cone beam1_2015 Fig. 2a Fig. 2b Fig. 2c Fig. 2d Fig. 3