If my veneers were not done properly, meaning there was a slight gap between the veneer and gum would this cause a cavity?

Porcelain veneers without proper fit , can cause gum inflammation, seepage of bacteria, and of course cavities in the tooth and root. The fit of veneers is of utmost importance to bring longevity for the veneers and healthy mouth!

The fit of a veneer is equally as important as the look.  If the porcelain does not fit seamlessly to the tooth, there is always a chance that debris can accumulate potentially causing cavities and gingival inflammation.  The precision of the work and the patient's home care are vital to their longevity.

When the veneers are not well adapted, they will cause inflammation of the gums causing gingivitis and can cause periodontal disease.Cavities will definitely be formed sooner or later, no matter what you do at home: dental floss, brushing, the best solution will be to repair the maladaptation.