As far as I know there are no such regulations for dental labs at all. Probably due to the fact that the dental ceramic materials (glass ceramics and zirconia) can be considered non-toxic. In case of milled parts there could however be some milling dust on top of the samples which to the largest extent will sinter onto the material and will not be released, the particles released into the kiln are mostly sintered agglomerates. Anyway post treatment after milling should be done in such a way to avoid release dust as far as possible (much more dust will be released during milling and handling of the white bodies).

Compared to manufacturing of ceramics in industrial scale where thousands of pieces are fired at a time the customized manufacturing of dental implants (one or a few pieces sintered at a time) has negligible output of dust, at least compared to other sources.