Be it the alpine or the standard variety Dianthus regenerate automatically after deadheading.
Have you made sure they're in full sun, and that the soil hasn't been enriched because they do best in impoverished soil - preferably alkaline rather than acid.

I grow a lot of both varieties here and after deadheading the new growth will flower within a week or so again.

First hello and Welcome Pinky I cant help re the soil but I find with mine after deadheading through the summer I get constant new blooms.

Just to add to Louise's comment they prefer a 'slightly' alkaline soil but will do just fine in neutral soil which is what all our alpine dianthus are in. We do dead head ours but don't see a lot of flower growth thereafter.

I cut back all mine after flowering to keep them tight, the alpines do not reflower and the others produce very little after the first full flush and thats what I expect.

Make sure your dianthus are in a dry place too, as they don't like too much moisture. I have mine in a very dry place, in sun most of the day, and after dead-heading the blooms just keep coming. They're also planted in ordinary, neutral garden soil, and have been very healthy this year. Good luck with yours, Pinky.
Hope you're enjoying this site as much as I am. Everybody's so helpful. Annie (Cumbria)

I grow many different Dianthus, they are poor soil plants and thrive on neglect Pinkey. This year they have been out standing due to the warm and dry spring.
I would be interested in knowing the names of yours Anneasby as I would love to find some real repeat bloomers.

If they are Dianthus chinensis hybrids, just picking the flowers off may not be enough. I usually cut the flowering stems down to the bottom joints, since they don't often grow new blooms from the upper joints, and the empty flowering stems gradually go brown, making the plants look like they are dying. There should be some new growth appearing at the base, and these stems will gradually become new flowers. That species needs more food than other Dianthus, so I would give them a water soluble according to package directions. Avoid "Super Bloom" and the like, since that will not encourage new growth, and they only flower on new growth.