AIBU to feel a bit resentful about my husband's attitude to my (narcissistic) mother?

It has to be faced that it is newgran2019 mother who is involved in this matter and if she is not happy with the arrangements it is for newgran2019 to "sort it out" with her parent, and nobody else.

It may well be that newgrans mother asked her husband directly to take her to the dental appointment and he agreed if his wife said nothing at that time but we simply do not know.

If the above supposition is correct, he is in a situation from which he simply cannot please everybody no matter what he does.

Perhaps it was the only appointment available, she may be in
pain.

I think it’s more the reasons behind why the appointment has been made on the OP’s birthday. The appointment itself is irrelevant, it can easily be changed. Does your mum live with you OP? Perhaps you need to get help from other family members, social services.

Oh dear newgran sounds like this has been going on for sometime?
Based on what you have described I would be miserable too.
Obviously some discussion is needed long term.
But for now risk arguments and rebook mothers appointment or rearrange lift.
If your husband wont spend the day with you on your birthday, arrange something with others. Or go to the cinema by yourself, followed by a cream tea maybe?
But make a small stand as * hetty* said at the very least it is inconsiderate behaviour.

If you can't stand up to her, I think it is a little unreasonable to expect him to really.

Why don't you arrange a driver AND pay the driver, then phone her and tell her it is already arranged. OR as Hetty says, change the appointment.

newgran2019I believe your husband is being very considerate and unselfish in putting himself forward to take your mother to the dentist. In the foregoing, your parent will well know the person who is taking her to the appointment which can be a nerve wrenching experience for many people on any occasion it may take place.

As it is at midway it will obviously be all over by early afternoon, and then you have the rest of the day and evening to spend with your husband to celebrate your birthday by going out, or staying in for any occasion you wish to create.

With every respect newgran2019, I believe you are looking for faults in your husband that simply are not there in this instance, and in that, I feel you should look to yourself for shortcomings in this matter.

I would change that appointment asap! They are both being very inconsiderate!