According to Fig. 5, the MBS decreases rapidly when the
thickness of HA layer increases from 0 to 90 mm. Rapid
changes in MBS occur because of low thickness of HA layer.
Further increase from 90 to 120 causes the decrease of the
MBS from 21.75 to 21.27 MPa that is a slight change as the
changes in the thickness of HA layer are small compared to
the thickness of the layer. For 120e180 mm thickness of HA,
the MBS again decreases from 21.27 to 20.3 MPa, while the
minimum of MBS occurs at 180 mm thickness. After that
with increasing HA thickness, the MBS also increases. In
former studies, authors concluded that the best thickness of
HA is about 60e120 mm due to the technology of coating HA
layer,25 but nowadays with enhanced technology of coating
HA layer, it is not limited to 150 mm, and it can even have
300e400 mm thickness.