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T a p e r e d i m p l a n t s f o r b u n d l e b o n e p r e s e r v a t i o n Crestal Subcrestal Mean ± SD p value Significance Mean ± SD p value Significance 8 weeks 35.22 ± 0.87 12 weeks 41.52 ± 0.11 0.4333 0.0231 p > 0.05 47.22 ± 0.87 p > 0.05* 54.87 ± 0.23 0.324 0.012 p < 0.05* p < 0.05* Implant placement PM-IS BC PM-IS LC IS BC IS-LC BC-LC (healing period) Mean ± SD Median Mean ± SD Median Mean ± SD Median Mean ± SD Median Mean ± SD Median Crestal (8 weeks) Subcrestal (8 weeks) Crestal (12 weeks) 3.20 ± 0.12* 3.2 2.92 ± 0.46* 2.9 2.17 ± 0.90 2.10 ± 0.16* 2.0 2.88 ± 0.90* 2.8 1.80 ± 0.40 2.70 ± 0.82* 2.7 3.12 ± 0.18* 3.0 1.99 ± 0.60 2.1 1.7 1.9 1.78 ± 0.80 1.60 ± 0.10 1.72 ± 0.30 1.7 1.6 1.7 1.61 ± 0.80 1.40 ± 0.90 1.61 ± 0.60 1.6 1.4 1.6 PM-IS BC = distance from the periimplant mucosa to the buccal bone crest; PM-IS LC = distance from the periimplant mucosa to the lingual bone crest; IS-BC = distance from the top of the implant shoulder to the first BIC at the buccal aspect; IS-LC = distance from the top of the implant shoulder to the lingual bone crest; BL-LC = difference between buccal bone crest and lingual bone crest; SD = standard deviation; * indicates statistical significance. Table 2 Table 3 Table 2 Mean values of BIC % ± standard deviation at the different time periods. Description of the data in healed bone. Table 3 Brunner and Langer test (non- parametric repeated measures analysis of variance) applied to mean values ± standard deviation and median values (mm) related to implants placed subcrestally. The level of significance was set at p < 0.05. Moreover, the delicate marginal portion of the buccal bone wall frequently contains proportion- ally larger amounts of bundle bone than the lin- gual wall does.11 Bundle bone is a tooth- related tissue that, after tooth loss, will model and even- tually disappear.4, 5 In the present study, BIC values decreased in the subcrestal group from the healing period of 8 weeks to the 12-week healing period in implants placed in healed bone. This finding corroborates that of Araújo et al.6, 7 The authors concluded that the BIC established during the early healing phase after implant insertion was partially lost when the buccal bone wall was resorbed. The gaps between the implant and the walls of the alveoli for immediate post- extraction implants were filled with bone tissue after the 8-week healing period. In the present study, a more coronal BIC was obtained in the test group (subcrestal). The total BIC revealed higher values in the subcrestal group. The higher BIC values of the test group after 8 and 12 weeks of healing suggest that bone regeneration may be more favorable for implants placed subcrestally, which is in agreement with results reported by other authors.55 Therefore, subcrestal insertion of dental implants may facil- itate anterior BIC at the implant neck. It was also observed that a comparatively larger portion of the implant surface was in direct contact with the bone within the defect area after a period of 12-week wound healing for the control and test implants compared with the 8-week healing period. This is in accordance with previous arti- cles published by other authors.55 They con- cluded that higher BIC values were found after 3 months of healing, compared with results after 1 month of healing. The present study demonstrated that, regardless of the vertical positioning, subcrestal placement (test group) and crestal placement (control group) showed similar outcomes and bone resorption patterns, with minor differences between them. The buccal and lingual BIC values were always higher for the subcrestal implants. Therefore, for these measurements, more favorable results should be obtained with subcrestal placement of implants. Clinically, implants are often inserted at crestal bone level.13, 14 However, implants can be inserted subcrestally in esthetic areas to min- imize the risk of exposure to metals and to allow sufficient space in the vertical dimension to develop an adequate emergence profile.24, 38, 39 The modeling in the marginal defect region was accompanied by marked attenuation of the dimensions of both the delicate buccal and the wider lingual bone walls. At the buccal aspect, this resulted in some marginal loss of osseointe- gration.6, 7 In this regard, Caneva et al. suggested that implants should be placed 1 mm subcrestally to reduce or eliminate exposure of the rough por- tion of the implant above the alveolar ridge.24 In addition, subcrestal placement of an implant may facilitate BIC earlier at the implant neck. 34 Volume 3 | Issue 3/2017 Journal of Oral Science & Rehabilitation