I've had a dental x-ray on day 4 of my cycle. is it safe to try to conceive this month or is it possible that the x-ray has any influence on the egg / ovulation?

There is no risk here. The dental X-rays and focused with minimal scatter and some dentists also place a lead apron as an extra precaution though that is not really necessary. Even a more direct and stronger X-ray exposure is very unlikely to have any effect on your eggs or ovulation.

Both you and your potential child are safe. Your body has probably had more background radiation in the time between the dental x-ray and your question, than from the x-ray itself. The x-rays were probably collimated, creating little risk of scatter, and you should have been wearing a lead shield when the x-ray was taken. And besides, you cannot expect your Dentest to work blind.