"shark teeth"-like PCB feature in high voltage section of modern HDTV
You can get rough calculations of the breakdown voltage from calculators. This paper has some measurements from an etched 0.55mm tooth gap:

Wan, F., Pilla, V., Li, J., Pommerenke, D., Shumiya, H., &amp; Araki, K. (2014). Time Lag of Secondary ESD in Millimeter-Size Spark Gaps. IEEE Transactions on Electromagnetic Compatibility, 56(1), 28–34. doi:10.1109/temc.2013.2275922 

As a serious discharge will tend to vaporize the tip of the tooth, the number of teeth is probably an indication of how many events the designer wants it to survive before the circuitry is on its own.
Many products, even consumer products, use commercial GDT (Gas Discharge Tube) devices, which have more predictable characteristics. Of course they cost a few cents more than zero.