Is a cbct or an x-ray good enough for a dentist to know if there is a need for a sinus lift in prep for dental implants(i'd go for a cbct anyway)?

Yes: The sinus can be in the path of an implant. An x-ray can be enough to determine if the sinus lift will be necessary. The cbct would provide more information.

Depends: Much depends on the individual (you) and the degree of risk you are willing to accept. Also, the experience and training of the surgeon is critical. A 3d scan is optimal, but not always necessary as some panographic images are very revealing when the situation is obvious (significant bone loss). Also, the restorative Dentist must be part of this. See a Prosthodontist for opinion. Good Luck.

Of course: Dentist can use of 3-D-CBCT imaging during the implant planning process or surgical phase can aid inserting implants around the maxillary sinus, or assist in surgery where the maxillary sinus is augmented with bone or PRP for sinus lift.

Both Are Helpful: In some cases, a two-dimensional X-ray can give adequate information. However, a three-dimensional CBCT scan will always be better....it will give a lot more information and detail, and the image is in three dimensions, so it can be viewed from any angle. A CBCT also allows exact measurement of the bone/sinus, so the dentist/surgeon will have a much better idea of what to expect. CBCT is ideal.