"overly dense" is a correct and usable phrase in written English.
You can use it to describe something that is very thick, compacted, or concentrated. For example, you could say, "The fog was overly dense, making it impossible to see more than a few feet ahead."
Overly dense, too, were tamales steamed in corn husks.
Some passages are overly dense, and could have benefited from better editing.
In the years that followed, he trotted out several elephantine proposals, diverse and invariably overly dense residential and commercial mixtures.
Sadly, most sweet potato pie is an overly dense custard in what might as well be a cardboard shell.
To recover its investment, the city may feel the need to fill the area with overly tall, overly dense office buildings.
Other desserts were good without being notable: chocolate cake, carrot cake, overly dense chocolate mousse, apple strudel with mushy apples, under-poached pear.
And really, where was the enjoyment in plying my body full of glucose goo, overly-dense energy bars and too much ibuprofen?
In general, outbreaks are more prevalent on poorer quality sites and where there are large populations of overly-dense, older trees (Fettig et al. [2007]).
Such liquid layering is believed to be common in magma chambers, where foamlike bubbly magma overlies denser magma.
This is often visible for our CHO cells analyzed by flow cytometry and is likely due to a portion of the plated culture that does not release from the synchronization (but is collected for analysis), likely due to overly-dense regions on the periphery of the plate.
Because of this, their attention spans are short and they're usually somewhat cynical when given information about a new product in the form of an advertisement, etc. Make all of your promotional efforts clear, quick, and informative without being overly-dense.
