# NBDHE practice questions: Scientific basis for dental hygiene practice Ten original NBDHE practice questions on scientific basis for dental hygiene practice, each answered on this page with a rationale and a source. Last updated: 2026-09-08. ## Question 1 In a tooth section, a mineralized tissue lies beneath the crown's enamel and continues into the root around the pulp. Which tissue is it? - A. Dentin - B. Cementum - C. Enamel - D. Gingiva **Answer A:** Dentin Dentin forms the bulk beneath enamel and cementum and surrounds the pulp. Why the other choices do not fit: B: Cementum is the root's external covering. C: Enamel covers the anatomical crown rather than continuing around root pulp. D: Gingiva is supporting soft tissue outside the tooth, not its mineralized core. **Common trap:** Confusing the outer covering with the underlying tissue. Source: [Primary Dentition](https://www.ncbi.nlm.nih.gov/books/NBK573074/) ## Question 2 Which opening at the root tip provides a route for blood vessels and nerves to enter the pulp? - A. Enamel prism - B. Cementoenamel junction - C. Dentinal tubule - D. Apical foramen **Answer D:** Apical foramen The apical foramen is an opening at the root tip through which neurovascular structures reach the pulp. Why the other choices do not fit: A: An enamel prism is part of enamel's structure, not an entry opening. B: The CEJ marks the crown–root tissue boundary. C: A dentinal tubule contains fluid and an odontoblast process; it is not the apical entry route. **Common trap:** Treating every microscopic channel as a root-canal opening. Source: [Primary Dentition](https://www.ncbi.nlm.nih.gov/books/NBK573074/) ## Question 3 A developmental diagram highlights the dental follicle. Which group of tissues derives from this structure? - A. Enamel, dentin and pulp - B. Pulp, cementum and enamel - C. Cementum, ligament and alveolar bone - D. Dentin, enamel and alveolar bone **Answer C:** Cementum, ligament and alveolar bone Follicle-derived cementoblasts, fibroblasts and osteoblasts form cementum, periodontal ligament and alveolar bone, respectively. Why the other choices do not fit: A: Enamel belongs to the enamel organ; dentin and pulp belong to the papilla. B: It incorrectly adds pulp and enamel to the follicle's derivatives. D: Only alveolar bone fits; enamel and dentin have different origins. **Common trap:** Grouping all mineralized tissues under one developmental origin. Source: [Physiology, Tooth](https://www.ncbi.nlm.nih.gov/books/NBK538475/) ## Question 4 Odontoblasts have deposited the first dentin in a developing crown. Which event normally follows in the neighboring enamel-forming tissue? - A. Ameloblasts begin depositing enamel matrix. - B. Cementoblasts begin depositing enamel matrix. - C. Odontoblasts change into enamel-forming cells. - D. Fibroblasts replace the enamel-forming cells. **Answer A:** Ameloblasts begin depositing enamel matrix. Initial dentin formation precedes enamel deposition by ameloblasts; the two cell populations retain distinct roles. Why the other choices do not fit: B: Cementoblasts produce cementum. C: Odontoblasts produce dentin rather than transforming into ameloblasts. D: Fibroblasts produce connective-tissue fibers, not enamel. **Common trap:** Knowing the tissue order but assigning the wrong cell. Source: [Embryology, Teeth](https://www.ncbi.nlm.nih.gov/books/NBK560515/) ## Question 5 A teaching model adds secondary dentin along the inner dentin wall while keeping the tooth's outer dimensions fixed. Which space becomes smaller? - A. Gingival sulcus - B. Pulp cavity - C. Periodontal-ligament space - D. Space between adjacent teeth **Answer B:** Pulp cavity Deposition at the inner dentin boundary reduces the space available for pulp. Why the other choices do not fit: A: The sulcus is outside the tooth, between tooth and gingiva. C: The ligament space lies outside the root. D: An internal addition does not change the stipulated distance between teeth. **Common trap:** Looking for an external change when tissue is deposited inward. Source: [Divisions and Components of the Teeth](https://www.dentalcare.com/en-us/ce-courses/ce500/divisions-and-components-of-the-teeth) ## Question 6 A neural diagram separates facial sensation from motor supply to masseter. Which trigeminal division can carry both sensory signals and this masticatory motor output? - A. Maxillary division, V2 - B. All three divisions equally - C. Mandibular division, V3 - D. Ophthalmic division, V1 **Answer C:** Mandibular division, V3 V3 is the mixed division and supplies motor fibers to primary masticatory muscles. Why the other choices do not fit: D: V1 is sensory. A: V2 is sensory. B: Only V3 among these divisions carries the specified motor supply. **Common trap:** A large sensory territory does not establish motor function. Source: [Cranial Nerve 5 (Trigeminal)](https://www.ncbi.nlm.nih.gov/books/NBK482283/) ## Question 7 In an anatomical model, the mandible is pulled backward from a protruded position. Which muscle portion most directly matches this retraction? - A. Posterior temporalis fibers - B. Anterior temporalis fibers - C. Lateral pterygoid fibers - D. Medial pterygoid fibers **Answer A:** Posterior temporalis fibers Posterior temporalis fibers retract the mandible. Why the other choices do not fit: B: Anterior fibers chiefly elevate. D: Medial pterygoid contributes elevation and protrusion. C: Lateral pterygoid contributes protrusion and lateral movement. **Common trap:** Treating every portion of one muscle as having the same pull. Source: [Mastication Muscles](https://www.ncbi.nlm.nih.gov/books/NBK541027/) ## Question 8 A student groups buccinator with the four primary muscles of mastication because it helps retain food between the teeth. Which correction is accurate? - A. It is a tongue muscle supplied mainly by XII. - B. It is a primary chewing muscle supplied by V2. - C. It is a primary chewing muscle supplied by IX. - D. It is a facial-expression muscle supplied by VII. **Answer D:** It is a facial-expression muscle supplied by VII. Buccinator assists food handling but is a facial-expression muscle with facial motor supply. Why the other choices do not fit: B: V2 is sensory, and buccinator is not in the primary group. A: Buccinator is a cheek muscle, not a tongue muscle. C: IX is not its motor supply. **Common trap:** Classifying a muscle solely by a task it helps perform. Source: [Mastication Muscles](https://www.ncbi.nlm.nih.gov/books/NBK541027/) ## Question 9 A model selectively interrupts taste fibers from the anterior two-thirds of the tongue while leaving its general sensation intact. Which pair explains the preserved and interrupted signals? - A. Touch through VII; taste through V3 - B. Touch through V3; taste through VII - C. Touch through IX; taste through XII - D. Touch through XII; taste through IX **Answer B:** Touch through V3; taste through VII Lingual V3 carries anterior general sensation; chorda tympani VII carries anterior taste. Why the other choices do not fit: A: It reverses the pathways. D: XII is chiefly tongue motor, not the anterior touch pathway. C: IX serves the posterior sensory territory, and XII is not the taste pathway. **Common trap:** Combining touch, taste and movement into one tongue function. Source: [Tongue](https://www.ncbi.nlm.nih.gov/books/NBK507782/) ## Question 10 A TMJ animation highlights rotation between the condyle and the articular disc. Which compartment is highlighted? - A. Lower discotemporal compartment - B. Upper discomandibular compartment - C. Lower discomandibular compartment - D. Upper discotemporal compartment **Answer C:** Lower discomandibular compartment The disc–mandible relationship is the lower compartment, where rotation occurs. Why the other choices do not fit: D: The upper compartment supports translation. B: Discomandibular describes the lower compartment. A: Discotemporal describes the upper compartment. **Common trap:** Memorizing upper or lower without identifying the two bordering structures. Source: [Temporomandibular Joint](https://www.ncbi.nlm.nih.gov/books/NBK538486/) ## Next step [Take the free 15-question NBDHE practice set](https://dentovio.com/nbdhe/free-practice-test) Official reference: [JCNDE — National Board Dental Hygiene Examination](https://jcnde.ada.org/nbdhe). Original exam-style questions written for study, never recalled exam content. Independent educational preparation, not clinical advice, and not affiliated with or endorsed by the Joint Commission on National Dental Examinations.