Lumineers that are of the no-prep variety can act like a shelf for bacteria to sit on at the gum line. Even if you "finish" them as the Lumineer people recommend the finished edge will never be as smooth as highly glazed porcelain. That is why I recommend designing a preparation that does not allow for flash or over contouring.
How Do I Take Care of Lumineers, Especially Around the Gum Line Where I Have Noticed Some Puffiness?
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You should have them checked by your dentist
If you're brushing and flossing thoroughly and your gums look healthy everywhere except around the Lumineers, there may be some cement left under the gum which can cause irritation. Have your dentist check the margins with magnification glasses and smooth the margins if necessary.
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