Hi Georgina,
We know from experience that people with significant mitral valve disease can develop a bacterial infection called endocarditis. The bacteria in your mouth enter your blood stream during procedures like dental cleanings and root canals. It can stick to the rough surface of the diseased valve and lead to very dangerous infection.
Ironically, the same is not true for the tricuspid valve. It is very rare. In fact, the risk of giving the antibiotics (which is very low) is greater than the risk of developing tricuspid valve endocarditis. I can only speculate as to why that is case. I looked for a reason online and in a few textbooks and didn't see it addressed. Pressure in the left heart (where the mitral valve is) are about 3-5 times higher than pressure in the right side of the heart (where the tricuspid valve is). That increased pressure and turbulence my make the surface the mitral valve more coarse and roughed up, making a better nesting site for blood bacteria. This is only speculation.
You should not worry about developing endocarditis on your tricuspid valve.
I hope this helps.
http://www.clevelandclinicmeded.com/diseasemanagement/infectiousdisease/prophylaxis/prophylaxis.htm