Will implants be effective if they are going into your sinuses?

If even the mini
implants will go into your sinus, then it sounds like you are in need of a
serious sinus lift procedure before any type of implant can be placed. Implants
must never perforate the sinus cavity, otherwise you will find the implant
failing, and experience severe complications. If you are going to invest in the
treatment, you want it done correctly, not in a way that will cause pain and
loss of the implant.

Implants should not ever be associated with the sinus. They can be close to the sinus but not go into it! It wil lbecome a failure. They can get infection around them as well as the implant needs sufficient bone strength and support for the implant to remain stable. If your dentist is suggesting this then you should reconsider. If you are pushing your dentist to do this to save money, then you should find another alternative to mini-implants. They are not hoghly recommended anyway unless it is short term. Good luck to you.

An implant, mini or regular, needs to be surrounded by bone. An implant perforating your sinus more than >3mm may cause chronic sinusitis.  I recommend you get a regular upper denture until you can have the sinus grafting.