Development of apatite coatings on Ti-6Al-7Nb dental implants by biomimetic process and EPD: in vivo studies

This paper compares the results of the effects of a biomimetic coating and electrophoretic deposition (EPD) of hydroxyapatite (HA) on the bond strength between the bone, implant and cell compatibility of Ti-6Al-7Nb dental implants. In the biomimetic process, screw shaped implants were chemically etched and NaOH activated to form hydroxycarbonated apatite after they were soaked for six days in a solution that was five times more concentrated than regular simulated body fluid (SBF). Electrophoretic deposition was also used to obtain a uniform coating of HA on other batchs of screws. Elemental, structural and in vivo histological and biomechanical investigations were carried out on the modified surfaces of the screws. The results show that there was a faster reaction of bone towards the coated implants compared to the uncoated one. More mature bones were observed on HA coated implants and increased mechanical strength (torque value) of bone-implant interface. Higher torque was needed to remove elephoretically and biomimetically HA coated screws from its bed compared to that needed for uncoated one (55, 50·16 and 37·45 N cm respectively). Biomimetic and electrophoretic coating with a bioactive HA leads to high integration between bone and implant by increasing the bioactivity of the product and to promoting mechanical properties of the implanted screws and enhanced osseointegration during the healing period. Owing to the higher roughness and porosity of the EPD coated screws (average R a = 2921±100 nm), the bone growth was much higher than that coated biomimetically (average R a = 1550±88 nm). Out of the two methods tried to form bioactive surface, EPD yields high bone adhesion when compared to the biomimetic coating.