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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 S t a t i s t i c a l a n a l y s i s Mean values and standard deviations were cal- culated using a BIC descriptive test and bone resorption measurements. The Wilcoxon test was applied to the comparison of mean averages and to quantify relationships between differ- ences. Brunner and Langer nonparametric tests were applied to the mean values for crestal and subcrestal implants and for periimplant mucosa measurement. All histomorphometric parame- ters were analyzed using descriptive methods (IBM SPSS Statistics for Windows version 19.0, IBM Corp., Armonk, N.Y., U.S.). For all of the tests performed, the significance level chosen was 5% (p < 0.05). Results When buccal, lingual, mesial and distal dimen- sions of the entrance to the fresh extraction sockets were measured before implant place- ment, mean alveolar ridge measurements of the extraction sockets were 5.3 ± 0.6 mm (2P2), 5.7 ± 0.2 mm (3P3), 5.9 ± 0.2 mm (4P4) and 8.9 ± 0.5 mm (1M1). H i s t o l o g i c a l e v a l u a t i o n Healing was uneventful for all of the animals and no implants were lost. Operative surgical sites healed without incident. All of the implants were available for histological analysis. The gaps between all of the implants and the bony walls disappeared as a result of bone filling and resorption of the alveolar crest in both groups (control and test). Direct contact between the living bone with slight vestibular resorption was observed, with stable soft tissue at 8 weeks for the crestal position and with a thicker gingiva in implants placed at the subcrestal level. Bone remodeling in the region of the marginal defect was accompanied by marked decreases in the dimensions of the buccal and lingual bone walls at 12 weeks at crestal and subcrestal levels (Figs. 3 & 4). For all of the implants, the kerati- nized oral epithelium was continuous with the junctional epithelium along the implants and the healing screws. Underlying connective tissue was observed with a dense network of collagen fibers around the implants placed in subcrestal healed bone, improving the quality of the periim- plant gingiva (Fig. 5) compared with crestally placed implants. After evaluation of all of the measurements, the distance from the top of the implant neck to the first BIC at the buccal aspect (A-Bc) showed statistically significant differences at 12 weeks in the test group compared with the control group (Figs. 6 & 7). In addition, the distance from the top of the implant collar to the lingual bone crest (A-Lc) showed significant differences between the crestal group and the subcrestal group after the healing period of 8 weeks. The A-Lc measure (distance between the implant collar top and the first BIC in the lingual aspect) was statistically significant after the healing period of 12 weeks in the subcrestal group. Total BIC values were higher for implants of the test group at 8 weeks with subcrestal place- ment and even higher in this group of implants after 12 weeks of healing compared with the crestal placement group (Table 1). The values of the BIC lingual aspect are described in Table 2. These were higher for the subcrestal group, and values increased from 8 to 12 weeks. The direct contact surface between the implant and the bone was larger for the test implants, with no statistically significant differences. Subcrestal placement always showed higher BIC values at 8 and 12 weeks (Figs. 5 & 8). Table 3 shows that the analysis of the periim- plant mucosa and buccal implant shoulder (PM-IS BC) presented higher values for the implants placed crestally at 8 and 12 weeks com- pared with subcrestal placement, with statisti- cally significantly different values at 12 weeks. Discussion The removal of single teeth followed by immedi- ate placement of an implant results in marked alterations to buccal ridge dimensions (30–43%) and the horizontal (63–80%) and vertical (65–69%) gaps between the implant and bone walls.46 The present investigation showed marked alterations after a healing period of 8 weeks that affected both the buccal and lingual bone walls. A-Bc and A-Lc values were lower for implants placed in healed bone at the subcrestal level than for those placed at the crestal level In addition, resorption was more pronounced, which is in agreement with studies previously published by our group.23 The present study revealed a greater depth of crestal bone resorption in the buccal bone than in the lingual crest. This bone dehiscence after implant placement corroborates the previously reported findings.4, 5, 23, 25, 52 32 Volume 3 | Issue 3/2017 Journal of Oral Science & Rehabilitation