Could a plastic retainer be causing cavities to form in my mouth?

Keep it clean. A retainer in and of itself does not cause decay. Bacteria feeding on the debris in your mouth will cause decay. Your teeth need hygiene (need to be brushed and flossed), and to do this, you must remove your retainers. Your retainers also need to be clean, as any food or debris will make the decay bacteria very happy. You don't want that. Clean your retainers also. .
No. It is the bacteria and acids in your mouth that cause cavities. Itis even more important to keep your teeth clean by brushing and flossing well now that you are wearing a retainer because a retainer wil ageist easier for these bacteria to accumulate. Keep your retainer and teeth clean and see your dentist regularly for exams and cleanings.
Possibly. If the retainer is not cleaned properly bacteria and mold may form and be transfered to the mouth. Additionally, be certain to clean mouth properly before placing the retainer in your mouth...Thorough flossing and brushing.
Oral hygiene. The plastic retainer itself won't cause cavities, but poor oral hygiene, unbalanced diet or sweet drinks could. Check with your dentist/orthodontist cavity prevention methods.
No. Bacteria causes cavities. If you are wearing a retainer and not cleaning your teeth and your retainer optimally, cavities can form. Review your Oral Hygiene with your Orthodontic Specialist and with your General Dentist.
No. Retainers or mouthguards don't cause cavities . Poor oral hygiene causes cavities.
It doesn't help. The retainer itself isn't the cause but it increases your chances of getting cavities by sitting against your teeth. The main reason people get cavities is too much sugar consumption and bad brushing/flossing habits. If you take your retainer out and clean it after meals, brush thoroughly twice daily, floss daily, and reduce your sugar intake you should be able to prevent cavities from forming.