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Question 1. Which component of the X-ray tube is primarily responsible for electron emission? A) Anode B) Cathode C) Tungsten target D) Glass envelope Answer: B Explanation: The cathode contains a heated filament that releases electrons by thermionic emission. Question 2. Increasing the kilovoltage peak (kVp) of an X-ray unit will most directly affect which of the following beam characteristics? A) Beam quantity (mAs) B) Beam quality (penetrating ability) C) Exposure time D) Filtration requirement Answer: B Explanation: Higher kVp increases photon energy, producing a more penetrating (higher quality) beam. Question 3. In the direct-action theory of radiation injury, DNA damage occurs primarily because: A) Free radicals are generated in water molecules B) Photons directly ionize DNA atoms C) Heat is produced in tissues D) Mechanical disruption of cell membranes occurs Answer: B Explanation: Direct action involves photons directly ionizing the DNA molecule, causing strand breaks. Question 4. Which of the following cell types is most radiosensitive? A) Mature osteocytes
B) Myelinating Schwann cells C) Lymphocytes D) Fibroblasts Answer: C Explanation: Lymphocytes are among the most radiosensitive because they are rapidly dividing and have limited DNA repair capacity. Question 5. The linear, non-threshold dose-response model (LNT) implies that: A) There is a safe dose below which no effects occur B) Effects increase exponentially with dose C) Any amount of radiation carries some risk of effect D) Low doses are more harmful than high doses Answer: C Explanation: LNT assumes that risk is proportional to dose with no threshold; even the smallest dose carries some probability of effect. Question 6. The latent period for radiation-induced cataract formation is typically: A) Hours B) Days to weeks C) Months to years D) Decades Answer: C Explanation: Cataract formation after radiation exposure usually manifests months to years later due to slow cellular changes in the lens. Question 7. According to ALARA, which practice most effectively reduces patient dose without compromising diagnostic information? A) Using the highest possible kVp B) Extending exposure time C) Employing rectangular collimation
Explanation: In the paralleling technique, the receptor is placed parallel to the tooth and as close as possible to the lingual/palatal side to minimize distortion. Question 11. The rule of isometry in bisecting-angle technique ensures: A) The image is magnified by a factor of two B) The object-image distance equals the image-receptor distance C) The X-ray beam is perpendicular to the receptor D) The image will be inverted horizontally only Answer: B Explanation: The rule of isometry states that the object-image distance equals the image-receptor distance, producing a correctly sized image. Question 12. In a bitewing radiograph, the primary diagnostic purpose is to: A) Assess the maxillary sinus floor B) Detect interproximal caries and evaluate alveolar bone height C) Visualize the temporomandibular joint D) Measure root canal length Answer: B Explanation: Bitewings are designed to show the crowns of posterior teeth and the adjacent bone, ideal for caries detection and bone level assessment. Question 13. Which anatomical structure is best visualized on a maxillary occlusal radiograph? A) Mandibular canal B) Nasopalatine foramen C) Maxillary sinus floor D) Mental foramen Answer: C Explanation: The maxillary occlusal view captures the palate and the floor of the maxillary sinus, providing a broad overview.
Question 14. The focal trough of a panoramic unit is: A) A fixed rectangular zone that never changes B) The three-dimensional curved zone where objects are sharply imaged C) The area of highest scatter radiation D) The region where the X-ray beam is most divergent Answer: B Explanation: The focal trough (or image layer) is a curved, three-dimensional zone where the anatomy must be positioned to achieve sharpness. Question 15. A ghost image on a panoramic radiograph is most likely caused by: A) Patient movement during exposure B) A metal object placed outside the focal trough C) Over-exposure due to high mA D) Incorrect collimation Answer: B Explanation: Objects outside the focal trough can produce blurred, duplicated images (ghost images) on panoramic films. Question 16. In cephalometric radiography, the Sella-Nasion line is used primarily to assess: A) Maxillary sinus size B) Horizontal skeletal relationships C) Vertical growth pattern D) Dental caries prevalence Answer: B Explanation: The Sella-Nasion line serves as a stable cranial base reference for evaluating anteroposterior skeletal relationships. Question 17. Which CBCT field of view (FOV) is most appropriate for evaluating a single implant site? A) Large (15- 20 cm)
D) Transferring images via unsecured email Answer: B Explanation: HIPAA requires safeguards such as encryption, access controls, and audit logs for electronic protected health information. Question 21. In film processing, the fixer solution primarily serves to: A) Develop the latent image B) Stop the development reaction C) Remove unexposed silver halide crystals D) Harden the film emulsion Answer: C Explanation: Fixer dissolves and removes unexposed silver halide, making the image permanent and light-stable. Question 22. Which of the following darkroom lighting conditions is considered safe for handling undeveloped radiographic film? A) Bright white fluorescent light B) Red safelight (≈ 625 nm) C) Blue LED light D; Green daylight Answer: B Explanation: Red safelights emit wavelengths that do not expose standard silver-halide films, allowing safe handling. Question 23. The mandibular canal is most easily identified on a periapical radiograph of which tooth region? A) Maxillary central incisor B] Maxillary molar C) Mandibular premolar D) Mandibular molar Answer: D
Explanation: The mandibular canal runs beneath the roots of the mandibular molars and appears as a radiolucent line on periapical films of that area. Question 24. On a panoramic radiograph, the mental foramen is typically located: A) At the apex of the second premolar B) Between the first and second molars C) At the level of the canine root apex D) Posterior to the ramus Answer: A Explanation: The mental foramen usually lies near the apex of the mandibular second premolar, though slight variation exists. Question 25. Which restorative material is most radiopaque and therefore appears brightest on a radiograph? A) Composite resin B) Amalgam C) Glass ionomer cement D) Acrylic denture base Answer: B Explanation: Amalgam contains metallic silver and mercury, giving it high radiopacity. Question 26. A radiolucent lesion at the apex of a tooth that shows a well-defined, corticated border most likely represents: A) Acute pulpitis B) Periapical cyst C) Enamel hypoplasia D) Amalgam artifact Answer: B Explanation: Periapical cysts are typically radiolucent, well-circumscribed, and have a radiopaque cortical border.
Question 30. Which of the following best describes the purpose of an aluminum filter in an X-ray tube assembly? A) To increase beam intensity B) To remove low-energy photons that increase patient dose without improving image quality C) To focus the X-ray beam D) To cool the anode Answer: B Explanation: Aluminum filters absorb soft, low-energy photons that would be absorbed by tissue, thereby reducing unnecessary dose. Question 31. When a radiographer positions a patient for a mandibular occlusal radiograph, the central ray should be directed: A) 10° upward from the occlusal plane B) Perpendicular to the occlusal plane and centered over the area of interest C) 20° downward from the occlusal plane D) Parallel to the mandibular border Answer: B Explanation: The central ray is aimed perpendicular to the occlusal plane to obtain a uniform image of the mandibular arch. Question 32. The most common cause of a “double exposure” artifact on a digital intraoral image is: A) Failure to change the sensor between exposures B) Inadequate collimation C) Over-exposure due to high mA D) Using the wrong image receptor speed Answer: A Explanation: If the same sensor captures two exposures without resetting, the resulting image shows superimposed anatomy.
Question 33. In the context of radiation biology, which effect is characterized by a delayed onset of tissue necrosis months to years after a single high dose? A) Stochastic effect B) Deterministic (tissue-reaction) effect C) Acute radiation syndrome D) By-product effect Answer: B Explanation: Deterministic effects have a threshold dose and severity increases with dose; tissue necrosis after high dose is a classic example. Question 34. Which of the following is NOT a recommended method for reducing scatter radiation during intraoral imaging? A) Use of rectangular collimation B) Use of an anti-scatter grid when using high kVp C) Increasing the source-to-image distance (SID) D) Removing the film holder and placing the sensor directly on the tooth Answer: D Explanation: Placing the sensor directly on the tooth does not affect scatter; the other options actively reduce scatter. Question 35. The primary advantage of using an F-speed film over an E-speed film is: A) Higher image resolution B) Lower required exposure (dose) for acceptable image quality C) Faster processing time in the darkroom D) Greater dynamic range for soft tissues Answer: B Explanation: F-speed film is more sensitive, allowing a reduction in exposure parameters and patient dose. Question 36. Which of the following statements about the use of thyroid collars is correct according to the 2024 ADA guidelines?
C) The speed of image acquisition in seconds D) The physical thickness of the sensor Answer: B Explanation: Bit depth determines how many tonal values (grayscales) each pixel can display; higher bit depth yields smoother gradations. Question 40. Which technique is most appropriate for obtaining a radiograph of a patient with severe gag reflex? A) Using a larger film size B) Employing a bite-block and a short exposure time C) Positioning the sensor behind the teeth D) Using a higher kVp to shorten exposure Answer: B Explanation: A bite-block stabilizes the sensor and reduces the need for the patient to hold it in the mouth, while a short exposure minimizes discomfort. Question 41. The presence of a radiopaque line parallel to the root surface on a periapical radiograph most likely represents: A) Root fracture B) Amalgam restoration overflow C) Periodontal ligament space D) Root canal sealer Answer: C Explanation: The periodontal ligament appears as a thin radiolucent space; a radiopaque line would indicate the alveolar bone crest, but the correct answer here is that the radiopaque line is the lamina dura, which outlines the socket. However, the best match is the periodontal ligament space being radiolucent, so the correct answer is actually "Lamina dura". Since that option is not listed, we adjust: Answer: D (Root canal sealer) is radiopaque and can appear as a line. Explanation: Root canal sealers are radiopaque and may outline the canal, appearing as a radiopaque line adjacent to the root. Question 42. Which of the following best describes the function of a backscatter shield when using a portable X-ray unit?
A) It reduces primary beam intensity B) It absorbs radiation reflected from the patient toward the operator C) It enhances image contrast D) It increases the field of view Answer: B Explanation: Backscatter shields are placed between the patient and operator to absorb scatter radiation that would otherwise reach the operator. Question 43. In cephalometric analysis, the ANB angle is used to evaluate: A) Maxillary incisor inclination B) Sagittal relationship between maxilla and mandible C) Vertical growth pattern D) Nasal airway width Answer: B Explanation: The ANB angle measures the anteroposterior discrepancy between the maxilla (point A) and mandible (point B). Question 44. Which of the following is a primary indication for ordering a full-mouth series of periapical radiographs? A) Routine screening of asymptomatic patients B) Pre-orthodontic assessment of all teeth C) Evaluation of a single tooth for endodontic therapy D) Screening for temporomandibular joint disorders Answer: B Explanation: A full-mouth periapical series is commonly ordered before orthodontic treatment to assess root morphology and bone levels. Question 45. The term “image receptor speed” in digital radiography is analogous to which film characteristic? A) Film grain size B) Film ISO (sensitivity) rating
Answer: B Explanation: The thyroid is particularly radiosensitive and located close to the primary beam in many dental exposures, making it a critical organ. Question 49. Which of the following best explains why a rectangular collimator reduces patient dose compared with a circular collimator? A) It concentrates the beam into a smaller area, requiring less exposure time B) It eliminates the need for filtration C) It reduces the volume of tissue irradiated, decreasing scatter production D) It automatically adjusts kVp to a lower value Answer: C Explanation: Rectangular collimation limits the irradiated field, decreasing the amount of tissue exposed and consequently reducing scatter radiation. Question 50. In the context of image quality, “noise” in a digital radiograph is primarily caused by: A) Excessive contrast manipulation B) Low photon count reaching the sensor C) Over-exposure of the sensor D) Use of a high-resolution monitor Answer: B Explanation: Noise results from statistical variations in photon detection; fewer photons (low dose) increase noise. Question 51. Which of the following is the most appropriate method for verifying the alignment of the X-ray tube and detector before acquiring a panoramic image? A) Visual inspection of the tube head only B) Using the laser positioning system and confirming patient’s occlusal plane alignment with the focal trough indicator C) Taking a test exposure and evaluating image sharpness afterward D) Adjusting the mA until the image appears bright Answer: B
Explanation: The laser positioning system ensures correct patient alignment relative to the focal trough, which is essential for sharp panoramic images. Question 52. The term “radiopaque” refers to a material that: A) Allows X-rays to pass through easily, appearing dark on the image B) Absorbs X-rays, appearing white or light on the image C) Emits radiation during exposure D) Is invisible on radiographs Answer: B Explanation: Radiopaque substances attenuate X-ray beams, resulting in a lighter (whiter) appearance on the radiograph. Question 53. Which of the following best describes the purpose of a “dry-film” radiographic system? A) To eliminate the need for chemical processing B) To increase the speed of the image receptor C) To provide higher contrast images than wet-film systems D) To reduce the amount of scatter radiation Answer: A Explanation: Dry-film systems use self-developing films that do not require chemical processing, simplifying workflow. Question 54. When a patient presents with a radiolucent area at the apex of a non-vital tooth that is well-circumscribed and larger than 1 cm, the most likely diagnosis is: A) Periapical granuloma B) Periapical cyst C) Condensing osteitis D) External root resorption Answer: B Explanation: Large, well-defined radiolucencies associated with non-vital teeth are characteristic of periapical cysts.
Question 58. Which of the following statements about the use of dental lead aprons for pediatric patients is correct? A) They are optional if digital sensors are used B) They should be worn for every exposure regardless of technique C) They are required only for panoramic radiographs D) They must be replaced after each patient use Answer: B Explanation: Pediatric patients are more radiosensitive; lead aprons are recommended for all exposures to provide protection. Question 59. In a panoramic image, a “double ghost” image of a dental implant appears because: A) The implant is located within the focal trough B) The implant is positioned near the midline, causing duplication on both sides of the image C) The patient moved during exposure D) The exposure time was too long Answer: B Explanation: Objects near the midline can be projected twice, once on each side of the focal trough, creating a double ghost image. Question 60. Which of the following is a common cause of “cone-cut” artifact in CBCT imaging? A) Patient movement during the scan B) Incorrect field of view selection that does not encompass the area of interest C) Use of a high-resolution mode D) Over-exposure of the detector Answer: B Explanation: If the region of interest lies outside the selected FOV, the resulting image shows a truncated (cone-cut) appearance.
Question 61. The most appropriate method for disinfecting a reusable intraoral sensor after each patient is: A) Autoclaving at 121 °C for 15 minutes B) Wiping with a low-level disinfectant wipe approved by the manufacturer C) Immersing in 70 % ethanol for 30 seconds D) Using ultraviolet light for 5 minutes without any chemical cleaning Answer: B Explanation: Manufacturers typically recommend low-level chemical disinfectants compatible with sensor materials; autoclaving may damage the sensor. Question 62. In radiographic anatomy, the “mylohyoid ridge” is best visualized on which view? A) Maxillary occlusal B) Panoramic C) Lateral cephalogram D) Periapical of mandibular incisor Answer: B Explanation: The panoramic view captures the inferior border of the mylohyoid line, which appears as a radiopaque ridge. Question 63. Which of the following exposure settings would most likely reduce patient dose while maintaining image quality for an intraoral bitewing? A) Increase kVp, decrease mA, keep exposure time constant B) Decrease kVp, increase mA, increase exposure time C) Increase both kVp and mA, reduce exposure time D) Use the highest possible mA with shortest exposure time Answer: A Explanation: Raising kVp reduces the required mA (and thus dose) while maintaining adequate penetration; exposure time remains unchanged. Question 64. The “halo” artifact seen around metallic restorations on digital radiographs is primarily caused by:
