Human fetal osteoblast behavior on zirconia dental implants and zirconia disks with microstructured surfaces. An experimental in vitro study.

OBJECTIVES

To measure the lateral surface area of microgrooved zirconia implants, to evaluate the cell geometry and cell density of human fetal osteoblasts seeded on zirconia microgrooved implants, to describe the surface roughness and chemistry, and to evaluate the activity of human fetal osteoblasts seeded on zirconia microgrooved disks.

MATERIALS AND METHODS

This experimental in vitro study used 62 zirconia implants and 130 zirconia disks. Two experimental groups were created for the implants: 31 non-microgrooved implants (Control) and 31 microgrooved implants (Test); two experimental groups were created for the disks: 65 non-microgrooved disks (Control) and 65 microgrooved disks (Test). The following evaluations of the implants were made: lateral surface area (LSA), cell morphology, and density of human fetal osteoblasts seeded on implant surfaces. On the disks, surface parameters (roughness and chemistry) and cell activity (alkaline phosphatase - ALP and alizarin red - ALZ) were evaluated at 7 and 15 days.

RESULTS

LSA was lower for control implants (62.8 mm) compared with test implants (128.74 mm) (P < 0.05). Cell bodies on control surfaces were flattened and disorganized, while in the test group, they were aligned inside the microgrooves. Control group cells showed few lamellipodia, which were attached mainly inside topographical accidents (surface cracks, valleys, and pits). Test group implants presented cells rich in lamellipodia prolongations, attached to the inner walls or to the borders of the microgrooves and in the flat areas between the microgrooves. Cell density was higher in the test group compared with controls (P < 0.05) Surface roughness and oxygen content increased in test disks samples compared with controls (P < 0.05). Carbon and aluminum were reduced in disks test samples compared with controls (P < 0.05), and ALP and ALZ levels were significantly increased on test surfaces (P < 0.05) at both study times.

CONCLUSIONS

Within the limitations of this experimental study, it may be concluded that (i) Roughness is increased and chemical composition enhanced on the surface of zirconia implants with microgrooves. (ii) The LSA of microgrooved zirconia implants is greater and provides more available surface compared with implants of the same dimensions without microgrooves. (iii) Microgrooves on zirconia implants modify the morphology and guide the size and alignment of human fetal osteoblasts. (iv) Zirconia surfaces with microgrooves of 30 μm width and 70 μm separation between grooves enhance ALP and ALZ expression by human fetal osteoblasts.