Peri-implant tissues at submerged and non-submerged titanium implants

The present experiment was performed to study the peri-implant tissue respo nse to non-submerged (1-stage) and initially submerged (2-stage) implant in stallation procedures. 6 beagle dogs were used. All mandibular premolars an d the ist, 2nd and 3rd maxillary premolars were extracted. After 3 months o f healing, 3 fixtures of the Astra Tech System were installed and submerged in the right (or the left) edentulous, premolar region in each of the 6 do gs. Radiographs were obtained immediately after fixture installation. In th e radiographs, the distance between the abutment-fixture junction and the m ost "coronal" bone in contact with the implant surface was determined. 3 mo nths later, abutments were connected to the initially submerged fixtures an d another 3 fixtures of the same system were installed in the contralateral , edentulous premolar region. Abutments were, however, immediately connecte d to the newly-installed fixtures (non-submerged side; test side). The muco sal flaps were replaced, adjusted and sutured in such a way that the corona l portion of the abutments remained exposed in the oral cavity. A new set o f radiographs were obtained from all 6 implant sites in each animal. A peri od of plaque control was initiated. Clinical examinations were performed an d radiographs obtained from all implant sites after another 3 months and at the termination of the experiment. 9 months after the Ist fixture installa tion procedure, the animals were sacrificed, the mandibles were removed, an d each implant region dissected. The most mesially-located implant sites we re processed for ground sectioning. The remaining biopsies were processed a nd embedded in EPON. The histometric analysis included assessment of the ve rtical dimension of the marginal soft and mineralized peri-implant tissues. The ground sections were used for measurements describing (i) "bone to imp lant contact" and (ii) "bone density". It was observed that the mucosa and bone tissue that formed at implants placed in a non-submerged or a submerge d procedure had many features in common. Thus, figures describing (i) the h eight of the mucosa, (ii) the length of the junctional epithelium and the h eight and quality of the zone of "connective tissue integration", (iii) the % of bone to implant contact as well as (iv) the density of the peri-impla nt bone, were similar in the submerged and the non-submerged groups. It is therefore suggested that a non-submerged (1-stage) installation technique m ay provide conditions for tissue integration that are similar to those obta ined using a submerged (2-stage) approach.