'to using' versus 'to use'

[brightonian]

I have a student who asked me why the sentence following is as it is:

"There are disadvantages to using mobile phones."

The student asked me why it isn't "There are disadvantages to use
mobile phones."........

I couldn't explain - i.e. I couldn't analyse the sentence. Is it because of the use of 'there are'?
This is a student who is a great communicator but has a number of grammar 'gaps'.

Can anyone help?

[wesofix]

Look at 'to'. It's either part of the full infinitive (to learn, to see, to eat...) OR it's a preposition. If it's a preposition, when it is followed by a verb the verb must be the -ing form - the present participle.

This problem crops up quite often when we have a prepositional verb with 'to' as the preposition:

'I still haven't got used to parsing sentences.'