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Purpose: To evaluate the influence on peri-implant soft and hard tissues of one-piece implants with a convergent hyperbolic profile collar placed at different depths with respect to the bone crest., Materials and Methods: Six dogs were included in the experiment. Three months after mandibular tooth extractions, two one-piece implants carrying a 2.8-mm-high convergent hyperbolic profile collar were placed in the alveolar crest with the coronal margin of the rough surface either 0.8 mm (test-1) or 1.8 mm (test-2) deeper with respect to the bone crest (Ct0). Two similar implants were instead placed flush to Ct0 as controls (control-1 and control-2, respectively). Healing screws were connected, and nonsubmerged healing was allowed. After 4 months, block sections were harvested, and histologic slides were prepared in a buccolingual plane., Results: In the histologic analyses, both the buccal crest and coronal level of osseointegration were located more coronally at the test compared to the control implants concerning the implant. However, the buccal bone crest with respect to Ct0 presented a loss of 0.8 ± 0.4 mm at the test-1 and 0.5 ± 0.4 mm at the control-1 implants (P = .028), and a loss of 2.0 ± 1.0 mm and 0.7 ± 0.4 mm at the test-2 and control-2 implants (P = .028), respectively. At the control implants, the collars were exposed above the peri-implant mucosa, while those of the test implants were not. However, the coronal level of the peri-implant mucosa with respect to Ct0 was located more apically at the test compared to the control implants., Conclusion: The placement of implants with a hyperbolic convergent profile collar in the subcrestal position resulted in higher buccal bone resorption and more soft tissue recession compared to the crestal implants with respect to the level of the bone crest at placement.

Objective: To histologically analyze the effect of a curettage of the granulation tissue on healing at implants installed immediately after the extraction of teeth presenting periapical lesions., Material and Methods: In seven dogs, the dental pulp was removed from the pulp chamber and from the root canals of the right and left third and the fourth mandibular premolars and of the left second premolar. The chambers were left opened and, after 3 months, apical lesions were present, and the premolars were extracted. One alveolus each premolar was selected and, before implant installation, the apical lesions of two alveoli were curetted (curettage group) while the other three were not treated (no-treatment group). The second right premolar was also extracted (Negative control group). Six implants each dog were installed, and a fully submerged healing was allowed. Four months after, biopsies were collected, and histological analyses were performed., Results: The proportions of new bone at the entire body of the implant was 70.2 ± 10.7% at the no-treatment group, 72.1 ± 14.8% at the curettage group, and 69.6 ± 3.7% at the negative control group. The respective new bone proportion at the apical aspect of the implants was 68.4 ± 17.5%, 61.5 ± 27.3%, and 78.1 ± 5.7%. None of the differences among the various groups were statistically significant. No inflammatory infiltrates were seen in the apical region., Conclusions: In this experimental study, it is concluded that the removal of the granulation tissue seems not to be necessary to obtain a proper osseointegration of implants installed immediately after the extraction of teeth presenting a periapical lesion., (© 2020. Springer-Verlag GmbH Germany, part of Springer Nature.)