Domain I Study Guide — Indigo Field Guide

1Start here

Two jobs: read the image, and make a good one.

Half of Domain I is interpretation — densities, landmarks, mounting, numbering. The other half is technique — paralleling vs. bisecting, angulation, and the error "fingerprints." The single densest testing areas are landmark ID, image selection, and panoramic positioning.

2Density — the whole game

White blocks the beam. Black lets it through.

Radiopaque (white / light)→dense, blocks the beam: enamel, bone, metal, amalgam

Radiolucent (black / dark)→beam passes through: caries, pulp, PDL space, cysts, air

Enamel is the most radiopaque (most mineralized) tissue. A cavity is radiolucent — it removes tooth structure. Metal restorations are the brightest thing in the mouth.

3Image types

Match the goal to the receptor.

Interproximal caries & early bone loss→Bitewing (crowns of both arches — no root tips)

Whole tooth, root tip & surrounding bone→Periapical

Large area / floor-of-mouth stone / impaction→Occlusal (mandibular cross-section for a floor stone)

Broad screen — impactions, fractures, TMJ, third molars→Panoramic (extraoral, 2-D)

3-D — implant planning, complex anatomy→CBCT

Ortho profile / skeletal relationships→Cephalometric

4Landmarks

Radiopaque vs. radiolucent — by memory.

Radiopaque (white)→nasal septum, ANS, zygomatic process, maxillary tuberosity, coronoid process, inverted Y, genial tubercles, mental ridge, mylohyoid ridge, lamina dura

Radiolucent (dark)→incisive foramen, median palatal suture, maxillary sinus, nasal cavity, mental foramen, mandibular canal, lingual foramen

Traps: the mental foramen near a premolar apex can mimic a periapical lesion. Of the sinuses, only the maxillary sinus appears on intraoral films.

5Numbering

Universal system: 1–32 (permanent), A–T (primary).

#1 = upper-right 3rd molar → #16 upper-left → #17 lower-left 3rd molar → #32 lower-right.

The four 3rd molars are #1, #16, #17, #32.

6Mounting

The raised dot (pimple) faces YOU = labial mounting (viewing as if facing the patient).

The patient's right is on your left.

Use anatomy to orient: maxillary sinus up top, the wide mandibular canal below.

7Exposure factors

kVp = beam penetration & contrast. Higher kVp → lower contrast (longer gray scale).

mAs = number of x-rays & density (darkness). Higher mAs → darker image.

8Angulation

Vertical too much → foreshortened (too short); too little → elongated (too long).

Horizontal off → overlapped contacts.

foreSHORTened = too much angle.

9Technique & localization

Paralleling, bisecting, and SLOB.

Paralleling→receptor parallel to long axis, beam perpendicular to both — least distortion, standard of care, needs a holder

Bisecting→receptor against the tooth, beam perpendicular to the imaginary bisector — more distortion, backup technique

SLOB — locate an object in 3-D→Same Lingual, Opposite Buccal: object that moves with the tube shift is lingual

10Error fingerprints

See the look → name the cause.

Clear curved band / corner→cone-cut → re-center the PID

Light image + tire-track / herringbone→film packet backward → white (tube) side to the beam

Overlapped contacts→horizontal angulation error

Teeth too short / too long→vertical — foreshortened / elongated

Two images superimposed→double exposure → automatic retake

Completely black / completely clear film→light exposure / no exposure (Light = bLack)

11Panoramic positioning

Chin UP → Frown · Chin DOWN → Smile.

Dark shadow over the maxillary anterior roots→tongue not on the palate (most common pano error)

Flat / reversed "frown" curve, maxillary roots washed out→chin too high

Exaggerated "smile" curve, condyles cut off the top→chin too low

One side magnified/blurry, other side small/sharp→head not centered

Blurry duplicate, higher & on the opposite side→ghost image → remove metal/jewelry

No thyroid collar on a panoramic — it blocks the beam and leaves a radiopaque artifact.

12Most-missed traps

Where Domain I points get lost.

"No root tips visible"→bitewing

Overlap error→horizontal angulation — not vertical

Elongation→too little vertical angle

Object moved same way as the tube→lingual (SLOB)

Round radiolucency at a premolar apex→could be the mental foramen, not a lesion

Domain I in 9 lines

✓ Radiopaque = white/dense (enamel, bone, metal); radiolucent = dark (caries, pulp, air).

✓ Bitewing = interproximal caries, no apices · periapical = whole tooth · occlusal = large area · pano/CBCT = broad/3-D.

✓ Landmarks: know each as radiopaque or radiolucent; mental foramen mimics a lesion; only the maxillary sinus shows intraorally.

✓ Universal 1–32; 3rd molars = 1/16/17/32. Dot (pimple) toward you = labial mounting; patient's right on your left.

✓ kVp = contrast (up → lower contrast); mAs = density (up → darker).

✓ Paralleling = least distortion, standard of care; bisecting = backup.

✓ Vertical error = foreshorten/elongate; horizontal error = overlap.

✓ SLOB: same-lingual, opposite-buccal for localization.

✓ Pano: chin up → frown; chin down → smile (condyles cut off); tongue up to kill the anterior shadow.