One common disagreement I get into in my line of work is: “Why not a plastic replica? They’re just as good, and they don’t involve the use of real people!”
While I do agree that plastic replicas have a place, I don’t agree with the idea that they are an exact replacement for real human osteology.
The first plastic was invented in 1886 by John Wesley Hyatt, in a bid to replace ivory for billiard balls. Because ivory would often shatter upon impact, a suitable replacement was necessary. While plastic has evolved in the 135 years since, I find it telling that plastic was literally invented to have different qualities than bone. When the first fully synthetic plastic was invented in 1907, it was prohibitively expensive for the average person to own. As the technology developed, the cost went down, and after World War II and the Space Age, plastic finally started replacing wood and metal in daily life in a meaningful way. Because the industrialization of plastic meant that plastic can be shaped and molded into any form, some people would assume that this means that plastic replicas are cheaper to produce. This is actually untrue. A good quality, non-Halloween-prop, research-grade skull can easily cost double what a genuine human skull would cost. Why pay double for something that is not the real thing?
Another failure in plastic models is the inability to accurately depict what actual bone does. Plastic cannot truly depict the trabeculae (the tiny porous structures that make up bones), the depth of sutures and minute indentations, the true weight of a bone, nor can it fully depict the interior structures of bones. To cast a human skull, sacrifices must be made to show a general picture of it. This means that bones such as the ones in the nasal passages are depicted as lumpier and less delicate than they are in reality. This problem occurs even in 3D printing, and while injection molds could potentially solve this problem, the cost of this process would also make the final object prohibitively expensive.
Another issue with plastic mold bones is that they cannot depict the difference between teeth and the rest of the skeletal structure. Teeth are made from dental pulp, covered in dentine, and then a layer of enamel. Bone is primarily made from collagen. This distinction is not able to be captured by a single plastic mold.
Finally, plastic molds cannot demonstrate the variety of human-kind. Bones vary by race, by size, by sex, by age, and by the lifestyle of the individual. Everybody is different, and casting one skull thousands of times does not give proper insight into the beautiful variety that happens among all people.
While I do agree that plastic bones can be helpful for basic study, real bones are infinitely more valuable.