Personally, I wouldn't withhold anything like that from my partner just to get what I wanted. But everyone's different.
What I would do is sit him down and really have a heart to heart. Explain to him how much you need that to feel fulfilled, or how you feel it's unfair to give to him without receiving something in return.
Maybe he could find another way to pay attention to you during foreplay. Perhaps he could use a clitoral vibe on you while using some of his fingers. I love the dental dam idea, so you might bring that up too. Another option is he could "plug you up" with a vaginal toy (dildo, plug, etc) so that not as much lubrication would be able to come out of you while he pleasures you orally.
If it means a lot to you, or just feel like you're doing all the giving, it's really important to talk to him about it. Do it at a time when you're not really thinking about sex, and try to be non-confrontational, non-judgmental and non-accusatory as much as possible. Best wishes!