Laser beam melting 3D printing of Ti6Al4V based porous structured dental implants: fabrication, biocompatibility analysis and photoelastic study

Abstract

Fabricating Ti alloy based dental implants with defined porous scaffold structure is a promising strategy for improving the osteoinduction of implants. In this study, we use Laser Beam Melting (LBM) 3D printing technique to fabricate porous Ti6Al4V dental implant prototypes with three controlled pore sizes (200, 350 and 500 μm). The mechanical stress distribution in the surrounding bone tissue is characterized by photoelastography and associated finite element simulation. For in-vitro studies, experiments on implants' biocompatibility and osteogenic capability are conducted to evaluate the cellular response correlated to the porous structure. As the preliminary results, porous structured implants show a lower stress-shielding to the surrounding bone at the implant neck and a more densed distribution at the bottom site compared to the reference implant. From the cell proliferation tests and the immunofluorescence images, 350 and 500 μm pore sized implants demonstrate a better biocompatibility in terms of cell growth, migration and adhesion. Osteogenic genes expression of the 350 μm group is significantly increased alone with the ALP activity test. All these suggest that a pore size of 350 μm provides an optimal provides an optimal potential for improving the mechanical shielding to the surrounding bones and osteoinduction of the implant itself.

Conflict of interest statement

The authors declare no competing financial interests.

Figures

Figure 1

(a) The general pattern of one kind of porous implant. The mid-piece area of all types of implants indicated by the white frame are further observed with the SEM. The SEM micrographs of (b), (c) reference screw type implant. Porous structured implant with pore size of 200 μm in (d), (e); 350 μm in (f), (g); 500 μm in (h), (i) at low (×30) and high (×10000) magnification respectively.

Figure 2

(a) The procedure of image post-processing converting a recorded elastograph into a binary image; Reference implant correlated to the fringe pattern under (b) 20, (c) 40, (d) 60, (e) 80 N; subfigure (f–i) parallely for fringe pattern on implant with 350 μm pore size. The manually sketched yellow line marks the layout of the implant.

Figure 3

Fringe pattern under 80 N and the corresponding simulation results of (a), (b) reference implant; (c), (d) 200 μm implant; (e), (f) 350 μm implant; and (g), (h) 500 μm implant. The color calibration in the simulation results represents the relative stress from min. in blue to max. in red. The primary stress is plotted separately from the stationary studies.

Figure 4

(a) Cell viability (b) and ALP activity of MC3T3-E1 cells of each group at different time points, whereby *P < 0.05; **P < 0.01.

Figure 5

Attached MC3T3-E1 cells showed by immunofluorescence after co-cultured with different type of implant for 24 h and 72 h. Typical images of control group (a-1, a-2) for 24 h and 72 h (b-1, b-2) at low (×40) and high (×100) magnification; 200 μm group (c-1, c-2) for 24 h and 72 h (d-1, d-2) at low (×40) and high (×100) magnification; 350 μm group (e-1, e-2) for 24 h and 72 h (f-1, f-2) at low (×40) and high (×100) magnification; 500 μm group (g-1, g-2) for 24 h and 72 h (h-1, h-2) at low (×40) and high (×100) magnification. i) Cell density of MC3T3-E1 cells attached on different type of implant at each time points. *P 

Figure 6

Attached MC3T3-E1 cells at the back side of different type of implant on Day 7. Few cells has migrated to the central axis of the control (a, a-1 for high magnification); 200 μm (b, b-1 for high magnification); 350 μm (c, c-1 for high magnification) group of implant. Plenty of MC3T3-E1 cells can be observed at the central axis of 500 μm pore sized implant (d, d-1 for high magnification). White arrows show the typical morphology of the attached MC3T3-E1 cells on each type of implant.

Figure 7

Relative mRNA expression of ALP in (a); Runx2 in (b); OCN in (c); and OPN in (d), whereby *P < 0.05; **P < 0.01.

Figure 8

The intended design of porous structured implant of (a) front and (b) back side in cross-sectional view