The phrase "more dense than" is correct and can be used in written English.
It can be used when comparing the densities of two things. For example: "The wood block was more dense than the foam cube."
New York County is the most densely populated county in the United States, and is more dense than any individual American city.
It is always much more dense than people think.
Depleted uranium is nearly two-and-a-half times more dense than steel and more than one-and-a-half times more dense than lead.
Bran inhibits gluten in bread, making wholemeal bread more dense than white.
That holds a grain of truth, because muscle is more dense than fat.
But Manhattan's business district is far bigger and more dense than most.
"These are harder and more dense than summer cabbages, which are softer".
Crucially though, the plasma was not exactly the same everywhere; some regions were slightly hotter and more dense than others.
The chocolate-banana bread pudding enlivened by a sour cherry-bourbon sauce was more dense than most but, nevertheless, appealing.
Although water is much more dense than air, the experiment recreated the effect of air flowing over a snake's body.
It was taller and more dense than before, but not so intertwined that we couldn't tunnel through it.
