Sectioning Sawfish Rostral Teeth Using Removable UV Resin

One of the big projects in our lab explores the ecology and life-history of sawfish through a keystone grant from the Save Our Seas Foundation. Our main tool for understanding that ecology is the chemistry and internal structure of the sawfish’s rostral teeth]. To analyze rostral teeth they need to be cut into thin sections that can be analyzed with laser ablation ICPMS.  

This method could be applied to any larger animal hard part; teeth, bones, otoliths, fin rays, operculum, vertebra, etc. The UV resin is removable, which has big advantages for LA-ICPMS since you can put more samples in the sampling chamber without that resin. There may be other reasons why you might not want your sample permanently embedded in epoxy resin, in which case this method might be useful. The UV resin is also much faster curing than other resins, which can be an advantage

The first step in that process is to embed the samples in ultraviolet (UV) cured resin. The video below shows how this is done.It’s important that UV resin not be applied in too thick a layer or the UV rays won’t penetrate far enough to cure the inside and you end up with a rostral tooth gusher.  

The UV is cured in a box filled with UV lights. These are easily found on Amazon and are used to cure certain types of 3D printed parts and figurines. Removing the sample from the mould halfway through gives it a chance for the UV to better penetrate the entire sample. 

Use the saw, set up for gravity cutting, to make an initial cut. You want to cut beside the main growth axis so that you don’t cut away any of the material we want to analyze. Cutting directly on the growth axis would cause you to lose some of the material at the tip of the tooth where it is thinnest. In the video below we’re demonstrating the procedure using a UV embedded piece of scallop shell, but the process is the same for any sample. See this video for how to set up the say for gravity fed cutting. 

Next, we need to glue the sample to a slide so that we can cut the remainder of the sample off and have a thin section we can work with. We use Crystalbond resin to do this. Make sure your hotplate is hot enough that the glue is liquid but not hot enough to burn it. Our hotplates are set on 129 degrees C, but every hotplate is different. 

Finally, once we have a thin section we can remove the UV resin and mount them using Crystalbond many-to-a-slide so that LA-ICPMS analysis is more efficient. 

If you have any questions about this method feel free to get in contact with the lab. We’re always willing to help or collaborate. 

Videos by Linh Truong. Writing by Jens Hegg