Peri-implant tissue alteration around tissue-level and bone-level implants in fresh extraction sockets: a histomorphometric study in dogs

BACKGROUND: To compare tissue alteration in fresh extraction sockets between bone-level and tissue-level implants with different neck designs. METHODS: Bilateral premolars of 6 adult Labrador dogs were extracted, and 24 bone-level and tissue-level implants with two different neck designs were immediately placed. At the same time, buccal bony wall thickness in fresh extraction sockets was also recorded. The Straumann® Bone Level (BL) and Standard Plus (SP) implants were positioned at two insertion depths: 1mm below and flush with the alveolar crest. All animals were sacrificed 6 months after the implant placement. Undecalcified block sections were obtained for histological measurement. Vertical bone resorption and biological widths were documented. Statistical analysis consisted of two sample t-test and Wilcoxon sign-rank test. RESULTS: All implants were histologically osseointegrated. There was no significant difference between BL implants and SP implants in vertical bone resorption regardless of the insertion depths (P>0.05). Meanwhile, significant difference was found in lingual biological width between BL (3.16 mm) and SP (2.43 mm) implants when placed 1mm below the alveolar crest (P<0.05). CONCLUSIONS: Within the limits, it seemed that different implant neck designs had little effect on bone remodeling in fresh extraction sockets. However, longer biological width was found in bone-level implants.