Vertical Dimension of Occlusion, or VDO — also known as Occlusal Vertical Dimension (OVD) — describes how much your front teeth show vertically when you speak or smile. If your VDO is is too short, it will seem as though your smile is very thin — your teeth will not show normally. In severe cases, the chin appears to be too close to the nose, and the lips may appear thin or tilt inward. If the VDO is too long, it may appear as if you have something stuffed into your mouth, and you may have trouble closing your mouth properly. The VDO is one of the many aesthetic details that your Orthodontist takes into consideration when planning your treatment.