9 Radiology in Orthodontics

Radiation Protection Regulations

  • Ionizing Radiation Regulations (2017): Safety for healthcare workers & public

  • Ionizing Radiation (Medical Exposure) Regulations (2018): Patient protection & safety

Purpose of Radiographs

  • Pre-Orthodontic Treatment: Clinical development assessment

    • Presence of permanent teeth

    • Dental & periodontal pathology; ectopic/supernumerary teeth

    • Root morphology; dental/skeletal relationships

    • Growth monitoring

Timing of Radiographs

  • Deciduous Dentition: Following trauma, assessing carious teeth

  • Mixed Dentition: Asymmetric eruption, failure of maxillary incisors, canines

  • Permanent Dentition: Prior to treatment planning, during treatment, post-treatment monitoring

Types of Radiographs

  • Orthopantomogram (OPT)

  • Occlusal Radiographs

  • Periapical Radiographs

  • Bitewing Radiographs

  • Cephalometric Lateral Skull Radiographs

Orthopantomogram (OPT)

  • Low-radiation, useful for screening teeth status and surrounding pathology

  • Can assess temporomandibular joint changes

  • Limitations: unclear in labial segments due to incisor inclinations

OPT Evaluation Elements

  • Film Overview: Chronological & developmental age

    • Mandibular anatomy: body shape, thickness, outline, radiodensity

    • Dental details: present teeth, stage of development, crown condition

    • Apical tissues: integrity of lamina dura, radiolucencies/opacity assessment

    • Periodontal tissues: PDL width, bone loss, calculus deposits

    • Structures: nasal cavity, antra, soft tissue shadows

Cone Beam Computed Tomography (CBCT)

  • 3D representation of oral/facial structures; higher radiation dose than conventional radiographs

    • Uses: orthodontic planning, prognosis of tooth position, TMJ evaluation

    • Equipment specifics

Types of Radiographs Explained

  • Occlusal Radiographs: Views root morphology, unerupted teeth, supernumerary teeth

  • Periapical Radiographs: Assess local pathology, ectopic teeth, and root resorption

  • Bitewing Radiographs: Evaluate dental caries and bone levels

  • Cephalometric Radiographs: Standardized lateral skull view for growth and treatment monitoring

Cephalometry Fundamentals

  • Importance of standardized imaging for comparisons

  • Indications for cephalometric radiography: treatment planning, growth monitoring, research, pathology evaluations

Key Measurements and Analyses

  • Cephalometric points: Sella (S), Nasion (N), etc.

  • Eastman Analysis for skeletal position

  • Definitions for skeletal classes based on ANB angle

Orthodontic Predictions

  • Moving maxilla & mandible for optimal positioning

Summary

  • Radiographs support clinical examinations, should not replace them

  • Utilize radiographs only when beneficial

  • Cephalometric analysis aids in skeletal and dental relationship assessment