Would an MRI scan or ultrasound be better to find problems with implants?

Typically your surgeon will begin with an ultrasound of the breasts to determine if there are obvious concerns, such as rupture. If needed, your surgeon can then order an MRI for more specific analysis of the breasts.

Dear Calm3644,
it depends on what is your surgeon suspecting. I understand your concern. However, without a proper assessment, it would be difficult to determine what is wrong. It is best that you visit your plastic surgeon for further assessment or ask for a second opinion. Only after a thorough examination, you can get proper recommendations and advice.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

MRI is the most sensitive test for evaluating breast implants. Other modalities are unable to detect issues with the implant capsule or evaluate for small leaks. Additionally, the Food and Drug Administration (i.e. FDA) recommends evaluating your implants with imaging approximately 5 years after implantation and then every 2-3 years thereafter.