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ePaper created 2016-03-07, 22:38:59 | version 1.38.0
20 Volume 2 | Issue 1/2016 Journal of Oral Science & Rehabilitation I m pla n t pos ition in g wi thi n e xtracti o n so cke ts Discussion The first aim ofthe present studywas to evaluate the influence of implant positioning within an ex- traction socket on the depth of the implant. The apex of the alveolus was used as apical point for preparationandthedrillsweretiltedtowardeither the buccal or the lingual aspects. No bodily dis- placementswereapplied.Theimplantswere,con- sequently,placedincontactwiththebuccalorthe lingual walls of the extraction sockets. Clinically, the lingual positioning of the implant is mainly achieved by a bodily displacement. However, a slightangulationoftheimplantmaybeappliedto- ward the lingual bone wall when necessary for anatomical or prosthetic reasons. In the present experiment, the final position was obtained by changing the angulation in relation to the axis of theextractionsocket.Theprocedureappliedinthe present experiment exaggerated the difference in angulations of the implants between the two groups, B- and L-sites, allowing the limits to be tested. It was shown that placing the implant lin- gually resulted in the implant shoulder being deeperwithrespecttothelingualbonecrestcom- pared with a buccal position, even though the im- plant margin was placed at the same level as the buccal bone crest. This was due to the rotation of the projection that occurred when the surgeon placedtheimplantflushwiththebuccalwallofthe extraction socket, as described previously in an- otherexperimentindogs.9 Fromaclinicalperspec- tive, if a lingual tilting ofthe implant is included in theprocedure,adeeperpositioningoftheimplant canbeexpectedcomparedwithanimplantplaced followingtheaxisofthealveolusorinabuccalpo- sition.Thisshouldbetakenintoaccountifthebuc- cal bone crest of the alveolus is used as the refer- ence level to judge the depth of the recipient im- plantsite. In the present experiment, the placement of an implant in a lingual position resulted in re- duced supracrestal exposure of the implant compared with a buccal positioning. This is in complete agreement with other studies that showed similar results.4–7 In an experiment in dogs,4 implants placed immediately into extrac- tionsocketswereplacedinthecenterofthealve- oli at the control sites, and placed lingually and 0.8 mmdeeperatthetestsites.Thesupracrestal exposure of the implants was higher at the cen- trallycomparedwiththelinguallypositionedim- plants. In another experiment in dogs,6, 7 the im- plantswereplacedinacentralpositionoftheex- traction sockets of third premolars and lingually in the alveoli of fourth premolars. After three months ofhealing, highersupracrestalexposure wasfound atthe implants placed inthe centerof thealveoli.Theseresultswerealsovalidatedbya multivariate multilevel analysis on implants placed into sockets immediately after tooth ex- traction.5 Thereasonforthisoutcomemaybeex- plained bythefactthatthe buccalwall ofthe ex- traction socket undergoes higher resorption than the lingual wall does.8, 10 The healing at an implantplacedintoanextractionsocketimmedi- ately after tooth extraction will be affected by this resorption. The more buccal the implant placement, the greater the supracrestal expo- sure of the buccal surface of the implant will be. This assumption has been further corroborated by other experimental studies on implants placed immediately into extraction sockets.11, 12 Intheseexperimentsindogs,wideimplantswith the same coronal dimensions as the extraction sockets were placed on one side, and implants narrower than the extraction sockets were used onthe otherside. Inthe latter, a gap resulted be- tween the buccal bone wall and the implant. Higher buccal bone resorption was observed at thewidecomparedwiththenarrowimplants. Factors such as the thickness of the buccal bone and the size of the horizontal defects pres- ent at the time of implant placement may influ- ence ridge alterations.13 It was shown that buc- cal bone crests of ≤1mm and residual buccal gapsof≤ 1 mmpresentedhigherverticalandhor- izontal resorption compared with buccal bone crests of >1mm and residual buccal gaps of > 1 mm.13 Thismayindicatethatthedistancebe- tween the outer contour of the bone crest at the buccal aspect and the surface of the implant plays the most important role. This, in turn, means that the closer the implant is placed into an extraction socket with respect to the outer contour of the bone crest, the greater the supracrestal exposure of the buccal surface of theimplantwillbe. After four months of healing, the top of the bone crest at the lingual aspect was located 0.1 mmbelowtheimplantshoulderattheB-sites and 0.8 mm above the implant shoulder at the L-sites. However,this does not meanthat higher resorption occurred at the lingual crest at the B-sites comparedwiththe L-sites. Infact, owing to the different angulation of the implants with respecttotheaxisofthealveolus,theimplantsat the L-sites were located deeper with respect to