Similar to the bedroom, there was nothing on any of the flat surfaces, not even dust.
Medical surfaces that detect pathogens.
In the late seventies and early eighties scaling these challenging surfaces really caught on.
The plates are compressed from before backwards, the anterior and posterior surfaces (as seen in the worn grinding face of the tooth) being nearly parallel.
When the summits of these are worn by mastication their surfaces present circles of dentine surrounded by a border of enamel, and as attrition proceeds different patterns are produced by the union of the bases of the cusps, a trefoil form being characteristic of some species.