The "infinite" compressive strength for a sample that cannot expand laterally is only an approximation valid for small pressures. At high enough pressures, all

The "infinite" compressive strength for a sample that cannot expand laterally is only an approximation valid for small pressures. At high enough pressures, all materials change their molecular and crystalline structures into structures with higher densities of atoms per volume and the volume of the tested samples diminishes, so the samples collapse at certain pressure thresholds. The well known transformation of graphite into diamond is just an example of what happens with any substance at high pressures. Diamond is a more unusual example just because it remains stable even after the pressure that has created it is removed. Moreover, for non-homogeneous materials, like concrete or many natural rocks used in construction, which are composed of harder particles cemented in a weaker matrix, it is normal to have a tensile strength that is many times smaller than the compressive strength, because when subjected to tension the weaker matrix allows pieces to detach, but in compression the strength may be determined mostly by the threshold where the harder particles break. The snail teeth are also made of composite materials, mineral crystals in a protein matrix, so they are also likely to have different strengths depending on what kind of stresses are applied and in what directions.