The ethical dilemmas of using animals as in vivo models in preclinical and
clinical examinations have been increasingly present in recent decades.
Small laboratory animals (rats, rabbits) will continue to be used because
they are cost-effective and permit the formation of statistically testable
cohort groups; a task that, for financial, maintenance and care reasons, is
almost prohibitive for larger animals. Technological advances in the
production of new biomaterials for clinical use are enormous, but screening
tests and methods used to assess biocompatibility lag behind these advances.
The assessment of biological responses is slow and based on millennial
recovery mechanisms in eukaryotic organisms. Therefore, the goal of
researchers in this field is to re-evaluate old methods of biocompatibility
assessment and introduce new methods of evaluation, especially for in vivo
testing. In that sense, a revision of the ISO standards was planned and
conducted in 2017, which insisted on cytotoxicity testing in cell lines and
produced concrete proposals on how biocompatibility should be quantified. In
vivo biocompatibility evaluation of biomaterials used for soft tissue
recovery commonly utilises rats. Rabbits are recommended for implants used
for hard tissues, because of the rabbit?s size, the possibility of
implanting the biomaterials on a larger bone surface, and because of the
peculiarities of rabbit bone tissue that favours rapid recovery after bone
defects and enables easy reading of the results.