Histomorphometrical and clinical study of connective tissue around titanium dental implants with porous surfaces in a canine model

Connective tissue (CT) reactions and collagen fiber orientation were evaluated on titanium implants with porous surfaces made by a laser method. Three groups in which the diameters of pores were 10 +/- 5 mu m, 40 +/- 5 mu m, and 70 +/- 5 mu m were involved in this test, together with a machined group as control. A total of 24 implants were randomly placed in mandibles after 3 months of premolars and the first molar extraction in beagle dogs. All the implants were firmly anchored in the bone after 3-month insertion. Histological sections showed that the gingival tissue was attached tightly to implant surface and there was no significant difference in inflammatory cell invasion and probing depth among all groups (p > 0.05). Histomorphometric analysis demonstrated that no significant difference in total CT length was observed among four groups (p > 0.05), however, the gingival recession in the 40 +/- 5 mu m and 70 +/- 5 mu m porous groups was less than in the 10 +/- 5 mu m porous group and control group (p < 0.05). Collagen fibers at the inner zone of the CT around the 40 +/- 5 mu m and 70 +/- 5 mu m porous implants aligned mostly in an oblique orientation, while there was a mainly parallel fiber direction around the 10 +/- 5 mu m porous and control implants. It was noted that some fibroblasts and fibers in the 70 +/- 5 mu m porous group was inserted into the pores of implant surface, indicating that pores of a proper size on the implant surface could induce the insertion of CT and prevent gingival recession.