OK, this is not technically toothpaste. However, it sure looks like it. This is an image of a man's elbow and it's from the New England Journal of Medicine (NEJM).
A 77-yr-old man renal-cell carcinoma (kidney cancer) presented with painful swelling of his elbow. This white chalky substance was a result of an acute flare of previously asymptomatic, chronic tophaceous gout. Hence, this image receives a heading titled, "Gouty Tophi." To read more, visit the NEJMhere.