A histological comparison in the dog of porous-coated vs. threaded dental implants

The histological findings of an 18-month trial, in the dog of a partially porous-coated endosseous dental implant made of Ti-6Al-4V, with a truncated conical shape, are described and compared with those for a cylindrical, threaded, endosseous implant made of commercially pure Ti. Six beagle dogs each received two porous-coated implants on one side of the mandible and two threaded implants on the contralateral side. Each set of two implants supported a two-unit fixed bridge for an 18-month functional period. Methylmethacrylate sections of both the buccolingual and mesiodistal aspects of each implant were examined qualitatively and by computer-assisted morphometry. The morphometric measurements were used for determination of the length of implant surface in direct contact with bone on each aspect of each implant. The data were expressed both as an absolute length and as a fraction of the maximum length available for contact (contact length fraction or CLF). On the buccal and lingual aspects of the implants, both the absolute lengths and CLF were significantly smaller for the porous-coated design. For the mesial and distal aspects, the absolute lengths and CLF were less for the porous-coated design, but the differences were not significant. However, when the absolute contact length was related to the corresponding vertical bone height, significant differences were observed, the absolute contact length being greater for any given bone height for the porous-coated design. Taken together, the data suggest that shorter implants may be used with the porous-coated design.