Bone-implant interface and remaining tissues on the implant surface after push-out test: an SEM observation

The purpose of this study was to compare the morphology of the tissues remaining on smooth and dimpled surfaces of a ceramic composite of zirconia-hydroxyapatite (TZ-2Y/25HA) with commercially pure titanium (cp Ti) after a push-out test. The tissue-material interface was viewed on the specimens without being tested mechanically. Cylindrical implants were inserted in the femurs of rabbits for three months. Each femur received three implants. After sacrificing the animals, the target tissues were collected and divided into two groups: group I was fixed in 4% formalin immediately, and group II was tested mechanically by push-out before fixation. Specimens were then dehydrated for SEM observation. The results showed that no remaining tissue appeared on the smooth cp Ti surface, whereas remaining tissues, mineralized and collagenous tissues, were seen on the smooth surface of the TZ-2Y/25HA. New bone had grown into and filled the most of dimple spaces of both the cp Ti and TZ-2Y/25HA implant. A submicron gap between the bone and cp Ti was found, whereas the TZ-2Y/25HA was occasionally in direct contact with new bone. Thus TZ-2Y/25HA showed an intimate contact to bone in some areas, and cp Ti showed an unmineralized tissue separated interface to bone continuously. Taken together, the laser machining seems to have no adverse effects on tissue response and is a potential technique for producing micro-patterned surfaces on dental and medical implants.