Soft and hard tissue response to an implant with a convergent collar in the esthetic area: preliminary report at 18 months

Aim: The purpose of this prospective cohort study was to investigate, over an 18-month period, soft and hard tissue response to a transmucosal implant with a convergent collar inserted in the anterior maxillary esthetic area. Materials and methods: From June 2013 to January 2014, 14 consecutive patients were enrolled (7 men and 7 women; mean age 63.7 ± 14 years) with 20 implants, needing at least one implant-supported restoration between the canines in the maxillary anterior esthetic area. Six months after hopeless tooth extraction and an alveolar socket graft, a transmucosal-type implant with convergent collar walls was inserted in a midcrestal position with mini-flap surgery. An impression was taken 2 months later, and a definitive abutment with a provisional restoration was positioned. The final restoration was seated 2 weeks later. Clinical parameters, photographs, radiographs, and impressions were taken at this timepoint, and after 6 and 18 months. Using dedicated software, radiographic analysis (to detect marginal bone-level changes) and cast analysis (to detect soft tissue vertical and horizontal changes) were performed. Results: At the 18-month follow-up, all implants were clinically osseointegrated, stable, and showed no sign of infection. At baseline, interproximal radiographs revealed no bone defect around the implant. After an initial minimal bone loss (0.09 ± 0.144 mm), radiographic analysis showed a stable condition of bone remodeling (mean value 0.09 ± 0.08; range 0.0 to 0.5 mm) at the 18-month follow-up. No statistically significant horizontal dimensional changes of the alveolar ridge were observed between each timepoint. Mean soft tissue levels significantly improved between baseline and 18 months. The mean heights of the mesial papilla (MP) and distal papilla (DP) changes were 0.38 ± 0.22 and 0.47 ± 0.31, respectively. The level of the labial gingival margin (LGM) was 1.01 ± 0.63. Periodontal parameters never exceeded the physiological levels. Conclusions: Within the limitations of this preliminary study, the analyzed implants produced positive results in these esthetically demanding cases. This outcome should encourage long-term studies in order to assess, through controlled clinical trials, whether this convergent collar design offers advantages over other designs. Furthermore, due to the peculiar crestal module, together with the use of delayed implant insertion and a postextraction ridge preservation technique with biomimetic hydroxyapatite, the analyzed implants seem to help prevent the negative bone remodeling typically associated with two-piece implant systems, but without the well-known drawbacks of traditionally designed transmucosal implants. Therefore, wherever crestal bone preservation is a critical issue for clinical success in the anterior maxillary area can be considered of particular interest.