In order to adhere the composite material to your teeth, the enamel surface has to be cleaned and treated with an acid gel (35% hydrophosphoric acid). The acid treated surface (etched) is impregnated with a bonding resin that has to be set using a special curing light. Only after these 2 steps can the composite be applied to the tooth surface and sculpted. The composite also must be set using the same curing light.
If NO tooth preparation (shaving) is done beforehand, the final veneers can be quite bulky. This may not be a desirable look for some people. Hence for most veneer cases, some tooth trimming is required.
If no care and attention is paid to shaping the interdental (between the teeth) and palatal (the back surface) contours of the veneers, unhygienic plaque traps can form. If you do not clean in between your teeth with floss, accumulation of food debris and oral bacteria will cause swollen bleeding gums (gingivitis), bad breath and tooth decay.
What tends to happen is staining at the veneer margins (the junction where the composite joins the tooth) especially if the veneer placement has been contaminated with plaque, saliva or blood or if you are at high risk for tooth decay. Tooth decay can burrow underneath veneers.
Should you wish to remove the veneers, your dentist can do it safely without harming your enamel but it is a long and difficult process. Good magnification (use of loupes) and good light is essential.
Regular monitoring and maintenance of composite veneers is mandatory. Xrays may be used to check for decay in between the teeth. After about 9-12 months, the composite surface tends to lose its gloss and needs to be repolished. The average lifespan of a composite veneer is between 3-5 years.