Radiographical and histological characteristics of submerged and nonsubmerged titanium implants. An experimental study in the Labrador dog.

Using 5 Labrador dogs, certain characteristics of the peri-implant tissues were analyzed after a 1-step surgical procedure for installation of Brånemark implants. Six titanium implants, in each mandibular quadrant, were installed in the regions of the right and left first molars and the fourth and third premolars. In the right mandibular quadrant, a traditional 2-step procedure was employed, whilst in the left quadrant, a 1-step procedure was carried out. The animals were monitored during a 6-month period. Biopsies of the healed peri-implant mucosa showed signs of superficial inflammation. The histological analysis revealed that i) the connective tissue lateral to the junctional epithelium showed limited accumulations of inflammatory cells (PICT), and ii) that at implant sites that had been exposed to the oral cavity for 6 months (1-step implants), an inflammatory cell infiltrate (abutment ICT) consistently was present in the tissues facing the abutment-fixture junction (AFJ). This infiltrate was separated from the bone crest by a 0.8-mm-wide zone of normal connective tissue. Irrespective of the surgical procedure applied, the radiographic and histometric measurements disclosed that i) the crestal bone loss was about 2.4 mm, ii) the height of the peri-implant mucosa varied from 3.5 mm to 3.9 mm, iii) the bone crest was located 1.1-1.5 mm apical of AFJ as well as of the apical termination of the junctional epithelium (aJE), and iv) a junctional epithelium of 2.1-2.4 mm faced the implant surface. In conclusion, this study demonstrates that, using a dog model, titanium dental implants ad modum Brånemark installed according to a 1-step or to a 2-step surgical procedure will obtain similar soft tissue adaptation and proper bone anchorage (osseointegration). Further studies are, however, required to ascertain the long-term clinical feasibility of the 1-step approach.