Influence of collar design on peri-implant tissue healing around immediate implants: A pilot study in Foxhound dogs.

PURPOSE: The study aims to assess the soft tissue level (STL) and crestal bone level (CBL), of titanium dental implants with different mixed collar abutments configurations. MATERIALS AND METHODS: This study included 48 implants with the same dimensions. They were divided into two groups of 24 implants each one: implants with a polished collar of 2 mm plus a roughened area of 0.8 mm (CONTROL) and implants with a polished collar of 0.8 mm plus a micro-threated and roughened area of 2 mm (TEST). The implants were inserted randomly in the post-extraction sockets of P2, P3, P4, and M1 bilaterally in the lower jaw of six foxhound dogs. STL and CBL were evaluated after 8 and 12 weeks by histology and histometry. RESULTS: All implants were clinically and histologically osseointegrated. Healing patterns examined microscopically at 8 and 12 weeks for both groups yielded similar qualitative findings for the STL evaluation, without significant differences between groups (P > 0.05). CBL was significantly higher in the buccal side in comparison with the lingual side for both groups (P < 0.05); the comparison between groups at 8 weeks showed IS-B (distance from the implant shoulder to the top of the bony crest) and IS-C (distance from the implant shoulder to the first bone-to-implant contact) values significantly higher for control group in comparison with test (P < 0.05). At 12 weeks, CBL showed increased values for both groups that were higher in controls group in comparison with test (P < 0.05). CONCLUSIONS: Bony crest resorption could not be avoided both at test and control sites. However, the neck conformation at the test sites reduced the buccal bone resorption. Soft tissue dimensions were similar both at the test and control sites.

Crestal bone loss related to immediate implants in crestal and subcrestal position: a pilot study in dogs.

OBJECTIVES: The aim of the present study was to compare crestal bone loss with different implant designs inserted immediately in crestal or subcrestal position in post-extraction sockets in a dog model. MATERIALS AND METHODS: The mandibular second, third, fourth premolars, and the first molars of six adult fox hound dogs were extracted bilaterally, and 48 implants were placed immediately in both hemi-arches of each dog. Randomly, eight implants (sky classic (®) and blue sky (®) ) were inserted, four crestally (control group) and four 2 mm subcrestally (test group). Both groups were treated with a minimal mucoperiosteal flap elevation approach. After a 12-week healing period, the animals were sacrificed, and samples were obtained. Biopsies were processed for ground sectioning. Histomorphometric analysis was carried out to compare buccal and lingual bone height loss. RESULTS: All implants were clinically and histologically osseointegrated. Healing patterns examined microscopically at eight and 12 weeks for both groups (crestal and subcrestal) yielded similar qualitative bone findings. At 12 weeks, the distance from the top of the implant collar to the first BIC (ISBc) showed significant difference between implant positions (crestal or subcrestal) in the buccal aspect (P = 0.1253), values for the crestal group being higher (1.79 ± 0.3 mm) in comparison with the subcrestal group (0.89 ± 0.5 mm). Better results were achieved by both implant designs when implants were placed in the deeper position. No significant differences were found in BIC values (P > 0.05). The total BIC at 8 weeks was (46.22 ± 4.29%) for the crestal group and (49.72 ± 2.21%) for the subcrestal group; at 12 weeks, it was (41.54 ± 3.87%) for the crestal group and (56.87 ± 3.46%) for the subcrestal group. CONCLUSIONS: Within the limitations of this study, the findings suggest that apical positioning of the top of the implant does not jeopardize bone crest and peri-implant tissue remodeling. However, less resorption of the lingual and buccal crest may be expected when implants are placed 2 mm subcrestally, but this is not related to implant design. Moreover, implants placed subcrestally produced better bone-to-implant contact measurements.