Dental X-rays explained — how to read shadows, decay, abscesses and bone loss

Key facts

• White = dense (enamel, fillings); dark = less dense
• Decay shows as a dark area in the tooth
• A dark shadow at a root tip may mean infection
• Bone loss shows as a lowered bone level
• X-rays are read together with an examination

Light and dark: the basics

X-rays pass easily through soft or less dense tissue and are blocked by dense material. On the image, areas that block more X-rays appear white or light grey (radiopaque), and areas that let them through appear dark (radiolucent). Enamel is the brightest natural tissue; dentine beneath it is slightly greyer; the pulp in the centre of the tooth and the root canals appear as darker channels. Metal fillings, crowns and implants look bright white, while many tooth-coloured fillings appear light grey. Healthy bone has a fine, sponge-like pattern, and a thin white line usually outlines each tooth socket.

What decay looks like

Tooth decay removes mineral, so it appears as a darker area within the white enamel or grey dentine. Between back teeth, early decay often shows as a small dark triangle or notch on the side of the tooth just below the contact point; this is why bitewing X-rays are taken. Deeper decay spreads into the dentine and may approach the pulp. Decay under an existing filling may appear as a dark line or area beneath it. Not every dark area is decay — natural anatomy, the gum line, or certain filling materials can mimic it — so dentists compare X-rays with what they see and feel in the mouth.

What a shadow at the root means

A common question is “what does a shadow on a tooth X-ray mean?” A dark, rounded area at the tip of a root (a periapical radiolucency) often indicates that infection from a dying or dead nerve has spread into the surrounding bone — a dental abscess or granuloma. It may be associated with pain, swelling or a gum boil, but sometimes causes no symptoms at all. A widened dark space around a root can indicate inflammation. Other causes include cysts or healing areas after root canal treatment. Your dentist will usually check with tests such as tapping and cold testing, and may suggest a CBCT scan if the picture is unclear.

How bone loss and other findings appear

In healthy gums, the bone level sits just below where the crown meets the root. In gum disease, the bone crest is lower, and the loss can be even (horizontal) or deeper along one root (vertical). Tartar under the gum may appear as small bright spurs on the root surface. X-rays also show impacted or missing teeth, extra teeth, root fractures in some cases, cysts and the position of the sinuses and nerve canal. Panoramic X-rays give an overview of all of this, while small periapical or bitewing views show more detail. Your dentist will explain which findings need treatment and which simply need monitoring.

Reviewing your X-rays with Dr. Fariba Alnoory

At Manhal Medical Center, Office 101, SMJ1 Building, central Dubai, digital X-rays are shown on screen during your appointment, and CBCT/3D imaging is available when a 3D view is needed. Dr. Fariba Alnoory, a general dentist with more than 14 years of experience, explains what each area shows, which findings are normal anatomy, what needs treatment and what simply needs watching. You are welcome to ask for copies of your images for your records or a second opinion. If you have an X-ray from elsewhere that worries you, bring it to a consultation. Seek prompt care for facial swelling, fever or difficulty swallowing.

A check-up is a full examination of teeth, gums, bite and soft tissues. Problems found early are simpler, quicker and less costly to treat.

Prepared by the Manhal Medical Center editorial team · Updated: 2026-10-18 · Treating specialist: Dr. Fariba Alnoory

This page is general information and does not replace a consultation. Suitability, risks and results vary between patients.