Bitewing Radiographs: Interproximal and Vertical

Objective. Students expose and evaluate standard horizontal and vertical bitewing radiographs of the posterior regions on a typodont, correctly positioning the receptor to capture interproximal contacts and alveolar bone levels.

Bitewing radiographs are among the most frequently exposed images in a dental office. They are designed to show the crowns of the maxillary and mandibular posterior teeth on a single image, along with the interproximal (contact) surfaces and the alveolar bone crest. Mastering bitewing technique is essential for passing the State Dental Radiology exam and for daily clinical practice.

Purpose of Bitewing Radiographs

Bitewing images serve two primary diagnostic purposes. First, they reveal interproximal caries — decay that forms between teeth where the explorer cannot easily reach. Second, they show the alveolar bone crest, allowing the dentist to assess bone height and detect early signs of periodontal (gum) disease. When interproximal contacts are truly open on the image, overlapping enamel does not hide potential decay. When the bone crest is visible just below the cementoenamel junction (CEJ), the dentist can evaluate bone levels accurately.

Horizontal vs. Vertical Bitewings

Horizontal bitewing radiographs are the standard for routine caries detection. The receptor (film or digital sensor) is positioned with its long axis running horizontally (parallel to the floor). A four-image series covering the premolar and molar regions is the most common adult survey. Horizontal bitewings show adequate crown detail and interproximal contacts, but the area of bone captured below the CEJ is limited.

Vertical bitewing radiographs are indicated when the dentist needs to evaluate bone levels in patients with known or suspected periodontal disease. The receptor is rotated 90 degrees so its long axis runs vertically. This orientation shows more of the root and alveolar bone apical to the CEJ while still opening the interproximal contacts. A four-image vertical series covers the same posterior regions as the horizontal series but captures significantly more bone height.

Receptor Placement

For both types, use a size 2 receptor for adults in the posterior regions. The receptor is held in a Rinn bitewing film holder (XCP-DS or similar) or secured with a commercial tab system. The patient bites down gently on the bite block or tab to stabilize the receptor. Key placement rules:

The front edge of the receptor should be placed at the midline of the canine for the premolar image and at the distal of the second premolar for the molar image.
The receptor must be parallel to the crowns of both arches.
The receptor should extend 3–4 mm below the mandibular occlusal plane to ensure the mandibular bone crest is captured.
For vertical bitewings, rotate the receptor holder so the long dimension is vertical; all other placement principles remain the same.

Beam Angulation and the Bitewing Tab Technique

The central ray must pass through the interproximal contacts at a +8 to +10 degree vertical angulation (slightly downward from horizontal). This positive angle prevents the beam from projecting one tooth's crown over another (overlapping). Horizontal angulation is set so the beam is perpendicular to the receptor and directed through the contacts, not from a mesial or distal angle that would cause overlapping.

When using a Rinn holder, the aiming ring aligns the tubehead so that the beam angulation and direction are correct automatically — this is a major advantage over the free-hand tab technique, which demands careful angulation judgment by the operator.

Common Errors and How to Avoid Them

| Error | Cause | Correction |

|---|---|---|

| Overlapping contacts | Incorrect horizontal angulation | Align beam perpendicular to contacts; use Rinn holder |

| Cone cut (missed receptor) | Tubehead not centered on receptor | Use aiming ring; check alignment before exposure |

| Bone crest not visible | Receptor placed too high in arch | Lower receptor; ensure 3–4 mm below occlusal plane |

| Blurry image | Patient or receptor moved during exposure | Stabilize receptor; remind patient to hold still |

| Dark (overexposed) image | Excessive kVp, mA, or time setting | Check exposure settings for patient size and receptor type |

| Light (underexposed) image | Insufficient exposure settings | Verify and adjust settings |

Selecting the Right Projection for the Clinical Scenario

Suspected bone loss / periodontal monitoring: Vertical bitewings — more bone is visible apical to the CEJ.
Routine caries screening: Horizontal bitewings — standard of care for most adults.
Child patient (mixed dentition): Horizontal bitewings using a size 0 or size 1 receptor with reduced exposure settings; four images may be condensed to two depending on arch size.

Radiation Safety in Bitewing Technique

Always apply the ALARA principle (As Low As Reasonably Achievable). Before any exposure:

1. Drape the patient with a lead apron and thyroid collar.

2. Confirm the correct exposure settings for the patient's size and the receptor type (digital sensors generally require less radiation than conventional film).

3. Stand at least 6 feet from the tubehead and behind a barrier during exposure, or step out of the room.

4. Never hold the receptor in the patient's mouth during exposure — use a holder.

5. Verify that the patient is not pregnant or that the clinical need justifies exposure with appropriate shielding.

Following these steps protects both the patient and the dental assistant and reflects the professional and legal standards required for your State Dental Radiology license.

Key terms10

Bitewing radiographA dental radiograph that shows the crowns of maxillary and mandibular posterior teeth on the same image, used to detect interproximal caries and assess alveolar bone levels.

Interproximal contactThe area where adjacent teeth touch; on a correctly angled bitewing, the contacts appear open (not overlapping) so the dentist can evaluate for decay between teeth.

Horizontal bitewingA bitewing image with the receptor positioned so its long axis is horizontal, used primarily for routine caries detection in adult posterior teeth.

Vertical bitewingA bitewing image with the receptor rotated so its long axis is vertical, used when the clinician needs to evaluate more alveolar bone height, particularly in periodontal disease.

Alveolar bone crestThe highest point of the alveolar bone between teeth; its position relative to the cementoenamel junction (CEJ) is a key indicator of periodontal health.

ALARAAs Low As Reasonably Achievable; the guiding radiation protection principle requiring that patient and operator exposure be kept as low as possible while still producing a diagnostically useful image.

Rinn bitewing holder (XCP-DS)A standardized film/sensor-holding device with a bite block and aiming ring that aligns the tubehead to the correct angulation automatically, reducing positioning errors.

OverlappingA positioning error in which incorrect horizontal angulation causes the images of adjacent tooth crowns or contacts to overlap, obscuring interproximal surfaces.

Cone cutAn error that occurs when the x-ray beam is not centered on the receptor, leaving a clear, unexposed area on the image and requiring a retake.

Cementoenamel junction (CEJ)The anatomical boundary where the enamel of the crown meets the cementum of the root; the reference point for evaluating bone levels on bitewing radiographs.

In class: Placement drill: students practice receptor placement and tab or Rinn bitewing holder positioning for premolar and molar regions on a typodont until contacts are consistently open and bone levels are visible, with instructor observing and correcting technique before exposure. · Exposure series: students expose a four-image horizontal bitewing series and a four-image vertical bitewing series, then mount and label both sets, indicating which is more appropriate for each of three provided clinical scenarios (suspected bone loss, caries screening, child patient). · Peer evaluation exercise: students exchange mounted bitewing series with a partner and complete a mutual error critique using the standardized rubric, followed by instructor-facilitated group debrief on the most common errors observed.
Materials: Dental x-ray unit, typodont phantom, Rinn bitewing film holders or tab system, size 2 receptors, imaging software, bitewing positioning reference card, standardized rubric, dental charting forms
Check: Instructor reviews both bitewing series; all eight images must show open contacts, correct coverage of alveolar bone crest, and acceptable density; student must achieve passing score (4–5 on rubric) on at least 7 of 8 images.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.