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Volume 2 | Issue 1/2016 15 Journal of Oral Science & Rehabilitation I m pla nt po si ti o ni ng wi thi n e xtracti o n so cke ts Introduction Aftertoothextraction,theimmediateplacement ofanimplantintoanalveolusisconsideredapre- dictable procedure, even though a higher loss of implants has been reported.1 Moreover, it has been shown that an implant placed into an ex- traction socket will not avoid bone resorption at thecoronalaspectofthewallsofthealveolus.2,3 Oneofthemostimportantaspectstobecon- sidered is the position of the implant within the extraction socket in relation to the buccolingual walls of the alveolus. It has been shown that a buccal placement will produce, after healing, higher supracrestal exposure of the implant at the buccal aspect compared with a lingual posi- tioning.4–7 This may be explained by the higher resorption of the buccal bone plates compared with the lingual bone plates during healing after tooth extraction so that a slope will be formed, beinghigheratthelingualaspectcomparedwith the buccal aspect.8 This, in turn, means that the closertheimplantistothelingualaspectandthe fartherfromthe buccalaspect,the lesserthe ex- posure ofthe implant body above the bony crest willbe. Owingtoanatomical,functionalandesthetic reasons, in a clinical situation, the axis of an im- plant placed into an extraction socket will be more lingually located compared with the tooth axis.This is explained bythe presence ofresidual defects between the implant body and the walls of the extraction socket that will be larger and more likely to occur at the buccal aspect com- pared with the lingual aspect.2 When an implant is placed into an extraction socket, the recipient sitewillgenerallybepreparedwithalingualbod- ily displacement, maintaining more or less the same axis of the alveolus. However, it has been suggested that, owing to the different projec- tion, if the axis of the implant is tilted in a lingual direction, the implant will be located deeper within the extraction socket than it would have been had the same axis as that of the alveolus been maintained,9 even though the margin will be located at the same level as the buccal bone crest. The concept of implant positioning needs to befurtherclarified.Hence,theaimofthepresent experiment is to evaluate the influence of im- plant positioning within an extraction socket on the depth of the implant at the time of surgery and on the buccal supracrestal exposure of the implantsurfaceafterhealing. Materials&methods The research protocol was submitted to and ap- proved by the ethics committee for animal re- search at the Universidade Estadual Paulista (Araçatuba,Brazil).EightLabradordogswerein- cluded in the study. The animals had a mean weightofapproximately30 kgandameanageof 2 years and were housed in kennels on concrete runs at the university’s field laboratorywith free access to water and moistened balanced dog food. Cli ni cal pro ce du re s At each surgery, the animals were first pre- anesthetizedwithAcepran(0.05 mg/kg;Univet- Vetnil, São Paulo, Brazil) and then anesthetized with Zoletil (10 mg/kg; Virbac, São Paulo, Brazil) and Xilazina (1 mg/kg; Cristália, São Paulo, Brazil), supplemented with ketamine (¼ of the dose of 10 mg/kg; Cristália, São Paulo, Brazil). Before the surgical procedure, the pulp of the mesial roots ofthe fourth mandibular premolars was removed on both sides ofthe mandible, and therootcanalswerefilledwithgutta-perchaand root canal cement (Mtwo, Endopocket, Epfill, Sweden & Martina). The crowns were afterward restored with composite (Adonis, Sweden & Martina). The surgical procedure began with an inci- sion performed within the sulcus. The flaps were elevatedandthe buccalandlingualalveo- lar bone plates were exposed. The fourth pre- molars were first hemisectioned and the distal roots removed, together with the correspon- ding portion of the crowns. The distal alveoli were subsequentlyprepared atthe apexforim- plant placement. However, randomly, the drill was tilted buccally at one site and lingually at the other. Implants 11.5 mm in length and 3.5 mm in diameter (Alvim CM, Neodent, Cu- ritiba, Brazil) and with a rough surface (sand- blasted and acid etched) were placed with the shoulder flush with the buccal bone (Figs. 1a & b). At one site, the implant was placed in a buc- calposition (B-sites), in contactwiththe buccal wall of the alveolus, while in the opposite jaw, the implant was placed lingually (L-sites), in contact with the lingual wall of the alveolus (Figs. 2a & b). Using a #15 UNC probe (Hu-Friedy, Chicago, Ill., U.S.), the horizontal and vertical dimensions of the remaining buccal or lingual Volume 2 | Issue 1/201615