Underneath the enamel surface the dentin layer contains an organized network of tubules that can be clearly seen on micrographs.

Here's a very cool article on the difference between narwhal tusks and human teeth :=} Towards the end it has a figure/photo of the dental tubules. https://biologicalexceptions.blogspot.com/2015/03/the-search-for-unicorn-slightly-off.html

That's a great review with clear photomicrographs and schematics. Enjoyed reading it. There are updated reviews available via Pubmed, too, for those that want the newest in-depth information--just search "dental caries pathophysiology" and screen for free full text.

Some examples are: https://pubmed.ncbi.nlm.nih.gov/35129809/ and https://pubmed.ncbi.nlm.nih.gov/35129809/

It is interesting that osteoporosis and dental caries have overlapping mechanisms, and together represent "the most prevalent chronic disease in the world" (per the first paper cited above). Osteoporosis affects approx 10% of the global populace and dental caries affect 100%...

Decreased transit time and this with increased osmotic pull is responsible for intraluminal fluid accumulation, aka diarrhea. Gas production from increased bacterial fermentation is also increased causing bloating and flatulence.

True, and a very good example is the multiplex kits available for simultaneously detecting multiple anti-SARS-CoV-19 isotypes (e.g., IgG, IgA, IgM) in blood in response to infection or immunization.

Antibodies are pretty stable molecules but physically attaching any additional moiety, such as a fluorophore, risks creating steric hindrance issues and reducing antibody binding to it's target antigen sequence. Even the smallest modifications such as biotinylation can slightly reduce binding in some instances.

These physical access issues can be more important with '2D' systems when the target is immobilized on flat microtiter plate bottoms, which effectively hides the bottom side of the molecule from exposure and target binding to the ELISA plate can alter its physical structure presented to the antibody, compared to 3D exposure of target/detection antibody in liquid/suspended environments.

Also, secondary antibodies are great for signal amplification, but non-specific background binding goes up, too, versus using a labeled primary ab. This isn't really an issue if appropriate controls are included, and the signal amplification is proportionally greater than any increased background binding.

Signal amplification. The primary antibody is relatively unencumbered of detection tags, so can maximally bind it's target unimpeded. The secondary, often polyclonal, can bind multiple sites on the primary Ig antibody that's already attached to the target molecule. So multiple molecules of secondary (labeled) can attach to each primary antibody, thereby increasing signal strength, whether fluorescence, chemiluminiscence or colorimetric, versus using a labeled primary antibody alone.