IM0110

I 07 case report _ sinus elevation I implants1_2010 plants were placed without bone grafting (Mattsson T et al. 1999). Theoretically, tilted implants in the residual crestal bone lead to (Aparicio et al. 2001): (a) Placement of longer implants that increases im- plant-to-bone contact area and implant primary stability; (b) Longerdistancebetweenimplantsthatallowsthe elimination of cantilevers in the prosthesis thus improving load distribution; (c) Placementofimplantsinresidualbonethatavoids furthercomplextechniquessuchassinusliftingor bone grafting. Clinically, the anatomy of the bone within the marginsofthenasalcavity,themaxillarysinuses,and thealveolarcrestmarginallallowalternativemesio- distal angulations of implants. The height at the 4 mm width of an alveolar crest, being the measure to describe the available bone volume for total cov- erageoftheimplant,isoftennotenoughforimplant installation in severely resorbed maxillae. Mesio-distal angulations of the implant thus provides better primary stability than conventional straight vertical positioning as it permits the use of a longer implant. A surgical technique was devel- oped to make use of the maximum amount of avail- able bone and to allow the installation of longer im- plants as indicated from computed tomography parasagittalreconstructions(Fig.1;MattssonTetal. 1999). Mattsson et al. described a surgical technique to visualize the total amount of maxillary bone and to place posterior implants at a more than 30 degree angle to the horizontal plane. By this technique the fixed bridge can be extended to at least the first mo- lar position without previous bone grafting. Presurgical examinations include a panoramic radiograph. Yet, in most cases, the extension of the maxillary sinus or the nasal cavity and the volume and density of the remaining bone are evaluated by maxillary computed tomography (Fig. 2). The esti- mationofbonequantityandbonequalityisbasedon presurgical radiography and computer aided plan- ning (Figs. 3 & 4) as well as on the resistance of bone to drilling during surgery (Kerkmanov et al. 2000). Significantly, tilted implants can be anchored in the bone pyramid anterior to the maxillary sinus where anatomic vital structures, such as arteries or nerves, are absent. Multiunit implantation thus al- lows the extension of prosthetic support posteriorly and reduces cantilever arms. The results of biome- chanical analyses and animal study indicate that tilting implants has no adverse effect on bone re- sorption (Gotfredsen K et al. 2001). Thisalternativeisinfactlesstime-consumingfor the patient and the dentist; scientific investigations support the concept of immediate and early func- tion as a modern therapeutic option (Testori T et al. 2004).Table1showsdifferentdegreesofangulations Fig. 4a_Presurgical computer aided planning (IMPLA 3D). Fig.4b_Presurgicalsofttissue appearance(IMPLA 3D). Fig.5_Situationpreoperation (CourtesyDrR.&M.Vollmer). Fig.5a_Drillingofthetitledimplant site.Placingmesialaxialimplants beforetiltedones.Intrasurgicalradi- ographsornavigationarenecessary toassesstheprecisedrillingdirection. Fig.5b_Afterthepilotdrillingforthe titledimplantosteotomesareusedfor enlargementandfinal preparationof theimplantsite.Firsttheaxialimplant wasinserted. Fig.5c_Tiltedimplantinsertionfol- lowingthedirectionoftheinitialhole. Fig.5d_Tiltedimplantinsite. Fig.5e_Radiographafterinsertion. Fig.5f_Exposureandinsertionofthe abutments. Fig.5g_Finalresult. Table 1_Degrees of angulations of tilted implants. Fig. 5a Inclination 15-30° >30° Mesiodistal 0 23 Distomesial 4 0 Number of implants per angulation Fig. 5b Fig. 5c Fig. 5d Fig. 5e Fig. 5f Fig. 5g