Prospective randomized clinical trial evaluating the effects of two different implant collar designs on peri‐implant healing and functional osseointegration after 25 years

Research on oral/dental intra-osseous implantology focuses primarily on discovering techniques that promote mechanical and/or biological osseointegration over the short-term. The present clinical research documents the effects of implant collar length, external versus internal connection collar design, and fixture surface microtexturing on bone and soft-tissue peri-implant healing after 25 years of function with complete mandibular dental prostheses.Objectives Evaluate the effects of two different machined‐collar lengths and designs on peri‐implant healing. Material and Methods An implant with a microtextured surface and 3.6mm‐long internal‐connection machined collar was compared to two implants that had an identical 1.2mm‐long external‐connection machined collar, but one had the microtextured surface while the other's was machined. Participants received the three implants, with microgap at the crest, alternately at five sites between mental foramen, and a full‐arch prosthesis. Peri‐implant bone levels were measured after 23 to 26 years of function. Keratinized tissue height, plaque, probing depth, bleeding, and purulence were also evaluated. Descriptive and mixed models for repeated\measures analyses were used, with Bonferroni correction for pairwise comparisons. Results Twenty‐two participants (110 implants) were evaluated at the 25‐year examination. Microtextured implants with the longer machined collar had significantly greater mean marginal bone loss (−1.77mm ± 0.18, mean ± SE) than machined (−0.85mm ± 0.18, p < .001) and microtextured (−1.00 ± 0.18mm, p < .001) implants with the shorter machined collar. Keratinized tissue height was greater for internal‐connection (0.74mm ± 0.10) versus external‐connection (0.51 ± 0.08, p = 0.01) microtextured implants. No differences were observed for plaque (p = 0.78), probing depth (p = 0.42), bleeding (p = 0.07), and purulence (p = 1.00). Implant survival rate was 99%. Conclusions Implants with the 1.2mm machined collar limited bone loss to 1mm, while those with the longer machined collar showed > 1.5mm loss after 25 years of function with microgap at the crest. Internal‐connection design and fixture surface microtexturing did not result in greater bone preservation

Long-term randomized clinical trial evaluating the effects of fixture surface acid-etching and machined collar design on bone healing

Objectives: An implant with an acid-etched fixture surface and internal-hex collar may achieve greater osseointegration. The goal of this research was to study the effects on long-term bone healing of fixture surface acid-etching and machined collar design. Method and materials: Three two-part implant types were compared: standard Brånemark (with an external-hex 1.2 mm long machined flat collar), Swede-Vent (a copy of the Brånemark design, with an identical collar but a fixture surface acid-etched to 1 to 3 µm), and Screw-Vent (with a fixture surface acid-etched identically to that of Swede-Vent, but a longer internal-hex machined flat collar that did not require countersinking). Fifty-eight subjects each received the three types in alternate fashion at five sites between mental foramen, and a fixed full-arch prosthesis. Abutment-implant interface/microgap (MG) was placed at the crest, and first bone-to-implant contact point-to microgap (fBIC-MG) was measured at mesial and distal sides of each implant. Mean fBIC-MG values were compared after 15 to 20 years of function. Statistical analysis was based on the mixed linear model with the level of significance set at P < .05 and Bonferroni correction for pairwise comparisons. Results: Brånemark had less mean marginal bone loss (-1.08 mm, standard error [SE] 0.20) compared with Swede-Vent (-1.28 mm, SE 0.20), but pairwise comparisons showed that the difference was not statistically significant (mean difference of 0.20 mm, P = .662). Screw-Vent had the greatest loss (-1.92 mm, SE 0.20), and pairwise comparisons showed that the difference was statistically significant compared with Brånemark and Swede-Vent (difference ≥ 0.64 mm, P < .001). Conclusion: According to accepted standards for osseointegration, all three implant types achieved very acceptable long-term results. However, while Brånemark had the least bone loss, the implant with the acid-etched fixture surface and longer internal-hex collar design had the greatest loss. Within the confines of this study, shorter collar length of 1.2 mm may be more important to limit long-term bone loss with microgap placed at the crest