TL;DR

Key Facts

What Is It?

Intraoral radiography encompasses all radiographic examinations in which the image receptor (film, PSP plate, or digital sensor) is positioned inside the patient’s mouth during exposure. This distinguishes intraoral from extraoral techniques (panoramic, cephalometric, CBCT) in which the receptor is held outside the mouth.

Intraoral radiographs provide the highest resolution images of individual teeth and their immediate supporting structures, making them the primary tool for caries diagnosis, periapical pathology assessment, root canal anatomy, bone level evaluation, and periodontal assessment. They are the most commonly performed radiographic procedure in general dentistry.

Three main types of intraoral radiographs exist, each serving a distinct clinical purpose:

1. Periapical radiographs: image the entire tooth from crown to root apex, plus at least 2–4 mm of surrounding alveolar bone
2. Bitewing radiographs: image the crowns of upper and lower posterior teeth simultaneously on a single receptor; the film/sensor is positioned horizontally (or vertically for bone assessment) with a bitewing tab or holder
3. Occlusal radiographs: image a broad section of the dental arch (maxillary or mandibular) using a larger-format receptor; the patient occludes gently on the receptor

Why It Matters

Intraoral radiographs remain the highest-resolution imaging tool for individual tooth and alveolar bone assessment. No other modality delivers equivalent detail of the periodontal ligament space, lamina dura, interproximal enamel, and root apex in routine clinical use. Their diagnostic yield and cost-effectiveness make them indispensable at every stage of dental care, from first examination to post-treatment review.

Clinical Relevance

• Caries detection: bitewing radiographs reveal interproximal caries not visible clinically, detecting lesions at the enamel-dentin junction before cavitation. Periapical films detect caries on root surfaces.
• Periapical assessment: periapical films are essential for endodontic diagnosis, revealing periapical radiolucency (granuloma, cyst, abscess), root morphology, and canal anatomy.
• Bone level assessment: both bitewing (crestal bone) and periapical (full root length) radiographs are essential for periodontal diagnosis and treatment planning.
• Restorative and prosthetic planning: root length, bone support, crown-to-root ratio, and proximity to anatomical structures (sinuses, inferior alveolar canal) are all revealed intraorally.

Periapical Radiography

Periapical (PA) radiographs are the workhorse of intraoral imaging. Their defining feature is that they capture the entire tooth — crown, root, and apex — together with at least 2–4 mm of surrounding periapical bone, enabling comprehensive assessment of both the tooth and its immediate supporting structures.

Purpose and Indications

The primary purpose of a periapical radiograph is to visualise the entire tooth and the periapical bone. Specific indications include:

• Endodontic diagnosis and treatment (working length, obturation check, post-treatment review)
• Detection and characterisation of periapical pathology (radiolucency suggesting granuloma, cyst, or abscess)
• Assessment of root morphology, number of canals, and root curvature
• Pre-extraction assessment and surgical planning
• Implant site evaluation (bone height and width)
• Periodontal disease assessment as part of a full-mouth radiographic series
• Dental trauma assessment (root fractures, luxation injuries)

Film and Sensor Sizes

Receptor size selection is determined by the patient’s age, arch size, and area to be imaged:

• Size 0 (22 × 35 mm): young children — anterior and posterior
• Size 1 (24 × 40 mm): adult anteriors, narrow arches
• Size 2 (31 × 41 mm): adult posteriors — most common size; also used for anteriors in adults
• Size 4 (57 × 76 mm): occlusal view (see below)

Paralleling Technique (Preferred)

The paralleling technique — also called the long-cone or right-angle technique — is the preferred method for periapical radiography because it produces accurate, reproducible, and minimally distorted images. The key principles are:

1. The receptor is placed parallel to the long axis of the tooth, held away from the tooth by a film holder (e.g., Rinn XCP, Dentsply)
2. The central ray is directed perpendicular (at 90°) to both the tooth and the receptor
3. A long-cone PID (16-inch/40 cm) is used — the increased source-to-film distance reduces magnification and beam divergence
4. Results in accurate dimensional representation, reproducible images, and less geometric distortion
5. Disadvantage: rigid palate, shallow palate, tori, or a strong gag reflex may complicate receptor placement

Paralleling Technique — Step-by-Step

1. Select appropriate film or sensor size for the area to be imaged
2. Cover sensor with a disposable barrier sleeve (infection control)
3. Mount sensor in film holder (e.g., Rinn XCP) with indicator arm attached
4. Position patient upright; select correct head position (maxillary: occlusal plane parallel to floor; mandibular: slight upward tilt so mandibular occlusal plane is parallel to floor)
5. Insert holder with sensor into the patient’s mouth — place parallel to the long axis of the teeth being imaged, with the sensor away from the teeth
6. Align the PID (cone) with the indicator ring of the holder so the beam is directed perpendicular to the sensor
7. Direct the beam through the contact points in the horizontal plane to open interproximal contacts
8. Instruct patient to bite gently on the holder bite block to stabilise the receptor
9. Step back at least 6 feet (or behind a barrier); activate exposure
10. Review the image for diagnostic quality before dismissing the patient

Bisecting-Angle Technique (Alternative)

The bisecting-angle technique is used when the paralleling technique is not feasible due to anatomical limitations (shallow palate, tori, gag reflex). It relies on the rule of isometry: two triangles sharing a common side are equal in size if two of their angles are equal.

1. Receptor is placed as close to the tooth as possible, touching the lingual or palatal surface
2. An imaginary bisecting plane is drawn between the long axis of the tooth and the plane of the receptor
3. The central ray is directed perpendicular to this bisecting plane
4. Short-cone or long-cone PID may be used
5. Disadvantages: geometric distortion (elongation if too little angle; foreshortening if too much angle), less reproducible, and difficult to standardise across operators and appointments

Periapical Angulations Reference

The following table provides approximate vertical and horizontal angulations for periapical radiographs taken with the paralleling technique. When using a film holder with an indicator ring, manual angulation calculation is largely eliminated — the ring guides the cone automatically.

Bitewing Radiography

Bitewing radiographs simultaneously image the crowns of maxillary and mandibular posterior teeth on a single receptor. The receptor is stabilised by the patient biting on a bitewing tab or holder — hence the name. They are the gold standard for interproximal caries detection and crestal bone height assessment.

Purpose and Indications

• Interproximal caries detection — the primary and most clinically important indication
• Crestal bone height assessment for periodontal diagnosis
• Detection of overhanging restorations and open margins
• Detection of recurrent (secondary) caries beneath existing restorations
• Assessment of crown-to-root ratio and restoration fit

Horizontal Bitewings

The standard bitewing orientation. The receptor is placed with its long axis horizontal, showing the proximal surfaces of premolars and molars, contact areas, and crestal bone height.

• Vertical angulation: +8° to +10° (slightly upward to prevent the crestal bone from being obscured by the crowns)
• Horizontal angulation: beam directed through the contact areas of the teeth being imaged — the most frequently misaligned parameter
• Standard adult series: 4 bitewings (2 premolar + 2 molar per side) for adults with full posterior dentition; 2 bitewings (1 premolar + 1 molar per side) for patients with smaller arches

Vertical Bitewings

The receptor is oriented with its long axis vertical. This captures more of the root and alveolar bone compared to a horizontal bitewing, making vertical bitewings the preferred choice for patients with moderate to advanced periodontal disease where accurate bone level assessment is required along the root length. The same angulation principles apply; the film holder is simply rotated to accommodate the vertical orientation.

Full-Mouth Series (FMX / FMS)

A complete radiographic survey typically consists of 18–20 images: 14–16 periapical radiographs covering all regions plus 4 horizontal bitewings. It is indicated for new patients without recent comprehensive radiographs and for patients with extensive dental disease requiring a full diagnostic baseline.

ADA Bitewing Selection Criteria

• Children and adolescents (primary or transitional dentition): every 6–12 months if at increased caries risk; every 12–24 months if low risk
• Adolescents (permanent dentition): every 6–12 months (high risk) to 18–36 months (low risk)
• Adults: every 12–18 months (high risk) to 24–36 months (low risk)
• Full-mouth series: every 3–5 years for adults with no significant dental disease; as clinically indicated for new patients

Occlusal Radiography

Occlusal radiographs image a large section of the maxillary or mandibular arch using a larger-format receptor (Size 4 film or occlusal-format PSP plate). The patient occludes gently on the receptor while the beam is directed from above (maxillary) or below (mandibular). Occlusal radiographs are less commonly ordered than periapical or bitewing radiographs and are used for specific clinical indications where a broad arch view is needed.

Maxillary Occlusal Views

• Vertex occlusal (topographic): beam directed from above, perpendicular to the film; shows the palate and relationship of structures in the sagittal plane
• Cross-sectional (lateral) occlusal: beam directed from the side; reveals buccal-lingual relationships
• Indications: supernumerary teeth, displaced or impacted anterior teeth, cleft palate assessment, salivary duct stones (sialoliths in the parotid duct), fractures of the palate

Mandibular Occlusal Views

• Topographic occlusal (90° to film): beam directed through the floor of the mouth; shows the mandibular symphysis, teeth, and surrounding bone
• Cross-sectional occlusal: reveals buccal-lingual width and position of structures
• Indications: sialoliths in the submandibular duct (Wharton’s duct), symphysis fractures, extent of cysts or tumours, supernumerary or impacted teeth

Intraoral Radiograph Comparison

Clinical Considerations

Safe and effective intraoral radiography demands attention to infection control, patient management, and accurate image interpretation. The following considerations are relevant to both clinical practice and examination preparation.

• Infection control: all intraoral receptors must be placed in a disposable barrier sleeve before insertion. Barriers prevent cross-contamination; they do not replace cleaning and disinfecting the sensor after use. Sensors should be wiped with an intermediate-level disinfectant between patients.
• Gagging: for patients with a strong gag reflex, consider topical anaesthetic applied to the receptor, distraction techniques, acupressure at the P6 point on the wrist, using smaller sensors, or attempting mandibular views first. Placing the receptor quickly and initiating exposure promptly minimises the time that triggers gagging.
• Tori: mandibular tori (lingual protuberances) and palatal tori interfere with receptor placement for the paralleling technique. For lingual tori, use a smaller sensor, angle the beam around the obstruction, and use cotton rolls to hold the sensor away from the soft tissue. The bisecting-angle technique may be necessary.
• Anatomical landmarks on periapical radiographs: candidates must recognise the maxillary sinus, nasal fossa, incisive foramen, mental foramen, mandibular canal, lamina dura, periodontal ligament space, alveolar crest, and nutrient canals as normal structures that must not be mistaken for pathology.
• Mounting conventions: radiographs are mounted with the identification dot (raised convexity) facing the viewer — the labial mounting convention most commonly used in the United States. The raised dot on the film or receptor should face the X-ray tube during exposure; the raised side indicates the side closest to the tube.

Common Mistakes & Misconceptions

The following errors recur regularly on INBDE-style board examinations and in clinical practice. Each represents a conceptual distinction that must be understood, not memorised.

• Misconception: “Bitewing radiographs can detect periapical pathology.”
  Correction: Bitewing radiographs only show the crowns and crestal bone. They do not extend to the root apex and cannot reliably detect periapical pathology. A periapical radiograph is required for endodontic diagnosis.
• Misconception: “Foreshortening in a periapical radiograph is caused by too little vertical angulation.”
  Correction: Foreshortening is caused by excessive (too much) vertical angulation. Too little vertical angulation causes elongation — a very common exam confusion. Remember: too much angle = short (foreshortened); too little angle = long (elongated).
• Misconception: “Vertical bitewings are used instead of periapical films for endodontic diagnosis.”
  Correction: Vertical bitewings show more root structure than horizontal bitewings but are used for periodontal bone assessment — not endodontic diagnosis. Periapical films remain necessary for full apex-to-crown endodontic assessment.
• Misconception: “Overlapping on a bitewing is caused by too much vertical angulation.”
  Correction: Overlapping of proximal contacts is caused by incorrect horizontal angulation. The beam must pass through the contacts at 90°. Vertical angulation errors cause elongation or foreshortening — not overlapping.
• Misconception: “A full-mouth series should be taken at every comprehensive exam.”
  Correction: Full-mouth series are indicated for new patients without recent radiographs or those with extensive disease — not routinely at every recall visit. Frequency must be individualised to caries risk, age, and clinical findings per ADA selection criteria.

Related Topics

Intraoral radiography connects directly to several foundational and applied areas of dental science.

References & Sources

The following foundational texts and authoritative guidelines inform this article.

1. White SC & Pharoah MJ, 2014. Oral Radiology: Principles and Interpretation. 7th ed. Elsevier Mosby.
2. Whaites E & Drage N, 2013. Essentials of Dental Radiography and Radiology. 5th ed. Churchill Livingstone.
3. ADA Council on Scientific Affairs, 2012. Dental Radiographic Examinations: Recommendations for Patient Selection and Limiting Radiation Exposure. American Dental Association.
4. Langland OE, Langlais RP & Preece JW, 2002. Principles of Dental Imaging. 2nd ed. Lippincott Williams & Wilkins.
5. Haring JI & Howerton LJ, 2006. Dental Radiography: Principles and Techniques. 3rd ed. Saunders.

Summary

Intraoral radiography — encompassing periapical, bitewing, and occlusal techniques — remains the highest-resolution, most clinically versatile tool in dental imaging. No other routinely available modality matches the detail with which intraoral films reveal interproximal caries, periapical pathology, the periodontal ligament space, and crestal bone levels. Mastery of receptor placement, angulation, film holder selection, and the clinical indications for each radiograph type is foundational to diagnostic excellence. Understanding the diagnostic hierarchy — periapicals for endodontics and full tooth assessment, horizontal bitewings for caries and crestal bone, vertical bitewings for bone loss, and occlusals for arch-wide pathology — enables the clinician to select the right image for every clinical question and to interpret findings with confidence.

About the Author

Dr. Andries Smith

Founder, Dental Panda

Dr. Andries Smith founded Dental Panda in 2020. As an immigrant to the United States, he had to take the INBDE exam, even though he was practicing dentistry for over 10 years. This revealed an opportunity. Andries noticed that INBDE prep course companies were putting profit over students. With his expertise and experience in dentistry, he created free dental wiki resources for students and the general public to have access to.