Acid Treatment
The acid treatment (etching) of implants represents one of the stages of surface treatment of some medical products manufactured by the ABM Technology Medical Product Plant. The principle of acid etching is rather simple: almost ready titanium product is put in the acid container having a definite temperature with the determination of hold up time varying in dependence on the specificities of technology and materials (reagents). The acid entering into a chemical interaction with the part metal and admixtures on its surface (as a rule, the contaminants – the abrasive particles remaining after sandblasting) removes these admixtures simultaneously making the part surface more rough evenslightly porous.
The acids used in different technologies of acid etching applicable at the ABM Technology Medical Product Plant are as follows:
• strong inorganic acids – hydrochloric (HCl) , sulfuric (H2SO4), fluorhydric or fluorohydrogen (HF) acid, nitric (HNO3) acid – are used in the technology of SLA contact surface formation;
• weaker organic acids (oxalic, formic, and trichloroacetic) are used in the technology of RBM contact surface formation.
The main purpose of acid etching in conditions of medical product manufacturing by the ABM Technology Medical Product Plant lies less in the chemical cleaning, elimination of contaminants soluble in the acidic medium and more in the formation of the microscopic reaction (etching) loci or so-called pores in the basic material (titanium and zirconium). The depth of such pores ranges from 2 - 4 µm (SLA surface) to 5 – 10 µm (RBM surface) depending on the nature of treatment.
The porous structure of contact surface etched by acidic method adds to its roughness got on the sandblasting equipment in the aggregate essentially increasing the real area of contact with a living tissue.
The research shows that a large area of the implant contact surface is one of the major factors of its effective and rapid survival to a living bone tissue at site of installation. Only the implants themselves direct contacting a living tissue are subjected to the technology of acid etching.