Study guide
1.1 Head & Neck Cranial Nerves, Osteology & Musculature
National Board Dental Hygiene Examination NBDHE
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1 Chapter 1: Head, Neck & Dental Anatomy, Histology & Embryology
1.1 Head & Neck Cranial Nerves, Osteology & Musculature 1.2 Tooth Morphology, Occlusion & Root Anatomy 1.3 Tooth Development, Histology & Embryology 1.4 Oral Physiology, Salivary Gland Function & TMJ Dynamics 1.5 General Pathology, Inflammation & Immunity Concepts
2 Chapter 2: Oral Pathology, Microbiology & Biofilm Ecology
2.1 Oral Mucosal Lesions, Soft Tissue & Salivary Pathology 2.2 Hard Tissue Anomalies, Cysts, Neoplasms & Radiographic Pathology 2.3 Periodontal Pathology, Plaque Biofilm Ecology & Microbiology 2.4 Cariology, Demineralization Mechanics & Fluoride Chemistry 2.5 Systemic Disease Manifestations & Oral Cancer Risk Factors 2.6 Genetic Conditions, Immunopathology & Diagnostic Biopsy Protocols
3 Chapter 3: Dental Pharmacology, Biochemistry & Nutrition
3.1 Autonomic Drugs, Cardiovascular & Respiratory Pharmacology 3.2 Analgesics, Opioids, NSAIDs & Central Nervous System Agents 3.3 Antimicrobial Therapy, Antibiotic Prophylaxis & Antivirals/Antifungals 3.4 Nutritional Biochemistry, Vitamins, Minerals & Dietary Analysis 3.5 Endocrine Pharmacology, Diabetic Care & Bone Metabolism Agents 3.6 Special Population Pharmacotherapeutics & Drug Interactions
4 Chapter 4: Patient Assessment, Risk Evaluation & Radiographic Interpretation
4.1 Health History Review, ASA Physical Status & Medical Risk Assessment 4.2 Comprehensive Extraoral/Intraoral Examination & Soft Tissue Inspection 4.3 Periodontal Assessment, Probing Techniques & Furcation Classification 4.4 Hard Tissue Examination, Caries Detection & Restorative Evaluation 4.5 Dental Radiography Principles, Physics, Technique & Radiation Safety 4.6 Radiographic Interpretation, Normal Landmarks & Pathologic Artifacts
5 Chapter 5: Periodontal Therapy, Instrumentation & Preventive Services
5.1 Periodontal Disease Etiology, Pathogenesis & Host Response 5.2 Non-Surgical Periodontal Therapy (NSPT) & Scaling/Root Planing (SRP) 5.3 Dental Hygiene Instrumentation, Ergonomics & Sharpness Maintenance 5.4 Preventive Oral Health Agents, Dentifrices, Rinses & Remineralization 5.5 Surgical Periodontal Therapy Overview & Maintenance Protocols 5.6 Patient Motivation, Behavioral Change & Oral Hygiene Instruction 5.7 Care Planning for Special Needs, Medically Compromised & Geriatric Patients
6 Chapter 6: Local Anesthesia Administration, Dental Materials & Special Care
6.1 Local Anesthesia Pharmacology, Neurophysiology & Vasoconstrictors 6.2 Injection Techniques, Anatomical Landmarks & Nerve Blocks 6.3 Local Anesthesia Complications, Toxicity & Nitrous Oxide Sedation 6.4 Dental Materials Chemistry, Impression Media & Restorative Auxiliaries 6.5 Pit & Fissure Sealants, Polishers & Biomaterial Biocompatibility 6.6 Orthodontic, Endodontic, Pediatric & Implant Patient Care
7 Chapter 7: Infection Prevention, OSHA/CDC Protocols & Medical Emergencies
7.1 Infection Control Principles, Transmission Pathways & Standard Precautions 7.2 Sterilization Methods, Biological Monitoring & Chemical Disinfection 7.3 OSHA Bloodborne Pathogens Standard, HazCom & Regulatory Compliance 7.4 Medical Emergency Recognition, CPR/AED & Protocol Management 7.5 Pharmacological Emergency Interventions & Airway Management 7.6 Instrument Processing Safety, Waste Management & Post-Exposure Protocols
8 Chapter 8: Community Oral Health, Epidemiology & Evidence-Based Research
8.1 Dental Public Health Principles, Community Assessment & Needs Analysis 8.2 Oral Epidemiology Indices: DMF, GI, PI, CPITN, Debris & Calculus Indices 8.3 Community Water Fluoridation Standards, Cost-Benefit & Public Health Policy 8.4 Evidence-Based Decision Making, Research Design, Control Groups & Sampling 8.5 Biostatistics in Dental Research: Mean, Median, P-values, Sensitivity & Specificity
9 Chapter 9: Integrated Case-Based Scenarios, Patient Cases & Professional Ethics
9.1 Case Scenario 1: Complex Periodontal Patient with Systemic Conditions 9.2 Case Scenario 2: Pediatric & Adolescent Preventive Management 9.3 Case Scenario 3: Medically Compromised & Special Needs Geriatric Patient 9.4 Case Scenario 4: Oral Pathology Identification & Interprofessional Referral 9.5 Professional Ethics, Jurisprudence & Dental Hygiene Practice Acts 9.6 Risk Management, Informed Consent & Interprofessional Collaboration
1.1 Head & Neck Cranial Nerves, Osteology & Musculature
Key Takeaways Explain This Topic AI
Trigeminus (CN V) is the principal sensory nerve of the head and neck and motor to muscles of mastication; V1 exits superior orbital fissure, V2 exits foramen rotundum, V3 exits foramen ovale.
Facial nerve (CN VII) exits stylomastoid foramen, supplying facial expression muscles, taste to anterior 2/3 of tongue via chorda tympani, and parasympathetic control to submandibular/sublingual glands.
Glossopharyngeal nerve (CN IX) exits jugular foramen, supplying taste and sensation to posterior 1/3 of tongue and secretomotor fibers to parotid gland via otic ganglion.
All four muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid) are innervated by CN V3; lateral pterygoid is the sole muscle responsible for mandibular depression and protrusion.
The hypoglossal nerve (CN XII) innervates all intrinsic and extrinsic tongue muscles except the palatoglossus muscle, which is innervated by the vagus nerve (CN X).
Last updated: July 2026
Head & Neck Cranial Nerves, Osteology & Musculature
NBDHE Core Concept: Mastery of head and neck anatomy requires a precise understanding of the 12 cranial nerves—specifically CN V, VII, IX, and XII—along with the osteological landmarks and masticatory musculature that govern jaw movement, sensory perception, and local anesthesia administration.
1. Cranial Nerves in Dental Hygiene Practice
Twelve pairs of cranial nerves emerge from the brain stem to innervate structures of the head and neck. Four cranial nerves are of paramount clinical significance in dental hygiene practice: CN V (Trigeminal) , CN VII (Facial) , CN IX (Glossopharyngeal) , and CN XII (Hypoglossal) .
Trigeminal Nerve (CN V)
CN V is the largest cranial nerve, functioning as a mixed nerve (sensory and motor). It provides general sensory innervation to the entire face, scalp, teeth, oral mucosa, and anterior two-thirds of the tongue, while delivering motor innervation to the muscles of mastication.
Ophthalmic Branch (V1): Purely sensory. Exits the cranium via the superior orbital fissure . Divides into frontal, lacrimal, and nasociliary nerves to supply the orbit, forehead, and bridge of the nose.
Maxillary Branch (V2): Purely sensory. Exits the cranium via the foramen rotundum into the pterygopalatine fossa. Key terminal branches include:
Infraorbital Nerve: Innervates anterior/premolar labial mucosa, upper lip, side of nose, lower eyelid.
Posterior Superior Alveolar (PSA) Nerve: Innervates maxillary molar pulp (except mesiobuccal root of 1st molar in 28% of patients) and buccal periodontium.
Middle Superior Alveolar (MSA) Nerve: Innervates maxillary premolars and mesiobuccal root of 1st molar.
Anterior Superior Alveolar (ASA) Nerve: Innervates maxillary central, lateral, and canine pulps and facial periodontium.
Greater Palatine Nerve: Innervates posterior hard palate mucosa from premolars to molars.
Nasopalatine Nerve: Exits incisive foramen; innervates anterior hard palate mucosa canine-to-canine.
Mandibular Branch (V3): Mixed (sensory and motor). Exits the cranium via the foramen ovale . It is the largest division of CN V.
Motor Division: Innervates the four muscles of mastication (masseter, temporalis, medial pterygoid, lateral pterygoid), mylohyoid muscle, anterior belly of digastric, tensor veli palatini, and tensor tympani.
Sensory Division: Includes Lingual Nerve (anterior 2/3 tongue general sensation), Inferior Alveolar Nerve (mandibular teeth), Mental Nerve (lower lip/chin), Long Buccal Nerve (buccal mucosa of mandibular molars), and Auriculotemporal Nerve (TMJ and parotid region).
Facial Nerve (CN VII)
CN VII is a mixed nerve exiting the skull through the stylomastoid foramen after traversing the internal acoustic meatus.
Motor Function: Innervates muscles of facial expression (orbicularis oris, buccinator, zygomaticus, platysma), posterior belly of digastric, and stylohyoid muscle.
Special Sensory (Taste): Supplies taste sensation to the anterior two-thirds of the tongue via the chorda tympani nerve (which hitches a ride with the lingual nerve of V3).
Parasympathetic Secretomotor: Supplies the submandibular and sublingual salivary glands (via submandibular ganglion) and lacrimal glands (via pterygopalatine ganglion).
Glossopharyngeal Nerve (CN IX)
CN IX exits via the jugular foramen .
Sensory & Taste: Supplies both general sensation and taste to the posterior one-third of the tongue , palatine tonsils, and pharynx.
Parasympathetic Secretomotor: Innervates the parotid salivary gland . Pre-ganglionic fibers travel via the lesser petrosal nerve to synapse in the otic ganglion , sending post-ganglionic secretomotor fibers via the auriculotemporal nerve to the parotid gland.
Motor Function: Innervates the stylopharyngeus muscle.
Visceral Sensory: Carries baroreceptor and chemoreceptor input from the carotid sinus and carotid body.
Hypoglossal Nerve (CN XII)
CN XII exits via the hypoglossal canal . It is a purely motor nerve that innervates all intrinsic and extrinsic muscles of the tongue (genioglossus, hyoglossus, styloglossus), with the single exception of the palatoglossus muscle , which is innervated by the Vagus nerve (CN X) via the pharyngeal plexus.
2. Summary Table of Key Head & Neck Cranial Nerves
- Cranial Nerve Exit Foramen Primary Sensory Targets Primary Motor / Secretomotor Targets
- CN V1 (Ophthalmic) Superior Orbital Fissure Forehead, upper eyelid, cornea, nasal mucosa None (Purely Sensory)
- CN V2 (Maxillary) Foramen Rotundum Maxillary teeth, periodontium, palate, upper lip None (Purely Sensory)
CN V3 (Mandibular) Foramen Ovale Mandibular teeth, lower lip, anterior 2/3 tongue Muscles of mastication, mylohyoid, ant. digastric
CN VII (Facial) Stylomastoid Foramen Taste: Anterior 2/3 tongue (chorda tympani) Facial expression muscles, submandibular/sublingual glands
CN IX (Glossopharyngeal) Jugular Foramen Sensation & Taste: Posterior 1/3 tongue, pharynx Stylopharyngeus, Parotid gland (via Otic ganglion)
CN XII (Hypoglossal) Hypoglossal Canal None (Purely Motor) Intrinsic & extrinsic tongue muscles (excl. palatoglossus)
3. Osteology of the Cranium and Facial Skeleton
The human skull comprises 22 bones divided into the neurocranium (8 bones protecting the brain) and viscerocranium (14 facial bones).
Neurocranium & Viscerocranium Overview
Neurocranium (8 bones): Frontal (1), Parietal (2), Temporal (2), Occipital (1), Sphenoid (1), Ethmoid (1).
Viscerocranium (14 bones): Mandible (1), Maxillae (2), Zygomatic (2), Nasal (2), Lacrimal (2), Palatine (2), Inferior Nasal Conchae (2), Vomer (1).
Key Cranial & Facial Bones in Oral Health
Sphenoid Bone: Situated at the base of the skull ("keyhole bone"). Contains the sella turcica (housing the pituitary gland), greater and lesser wings , and pterygoid processes (medial and lateral pterygoid plates). The space between the lateral pterygoid plate and maxilla forms the infratemporal and pterygopalatine fossae.
Maxilla: Paired bones forming the upper jaw, hard palate floor, and orbital floor. Key features include the incisive foramen (transmits nasopalatine nerve), infraorbital foramen (transmits infraorbital nerve/vessels), and maxillary sinus .
Mandible: The largest, strongest facial bone. Key features include:
Body & Ramus: Joined at the angle of the mandible.
Coronoid Process: Thin, triangular anterior projection serving as the insertion point for the temporalis muscle .
Condyloid Process (Condyle): Articulates with the mandibular fossa of the temporal bone at the TMJ.
Mandibular Foramen: Located on the medial aspect of the ramus; entry point for the inferior alveolar nerve and vessels.
Lingula: A ridge of bone anterior to the mandibular foramen, serving as the attachment site for the sphenomandibular ligament .
Mental Foramen: Located on the facial aspect of mandible near premolar apices; transmits mental nerve and vessels.
Mylohyoid Line: Internal ridge serving as origin for mylohyoid muscle.
Genial Tubercles: Small bony projections near midline on lingual surface for genioglossus and geniohyoid insertions.
Palatine Bone: Horizontal plates meet at the median palatine suture to form the posterior one-third of the hard palate. Contains the greater palatine foramen (posterior palate near 2nd/3rd molars) and lesser palatine foramina (soft palate).
Temporal Bone: Houses the middle and inner ear; features the mandibular (glenoid) fossa and articular eminence for TMJ articulation, styloid process , and mastoid process .
4. Muscles of Mastication & Jaw Mechanics
All four muscles of mastication develop from the first branchial arch (mandibular arch) and are innervated by the mandibular division of the trigeminal nerve (V3).
Muscle Origin Insertion Main Action(s)
Masseter Zygomatic arch Lateral surface of mandibular ramus & angle Elevates mandible (closes jaw); powerful biting force
Temporalis Temporal fossa & fascia Coronoid process & anterior ramus of mandible Elevates mandible; retrudes mandible (posterior fibers)
Medial Pterygoid Medial surface of lateral pterygoid plate & maxilla Medial surface of mandibular ramus & angle Elevates mandible; assists in protrusion & lateral movement
Lateral Pterygoid Superior head: Greater wing of sphenoid; Inferior head: Lateral surface of lateral pterygoid plate Pterygoid fovea of condyle neck & TMJ articular disc Depresses mandible (opens jaw); protrudes mandible; lateral deviation
Critical Clinical Board Note: The lateral pterygoid is the only muscle of mastication that actively depresses (opens) the mandible. Unilateral contraction of the lateral pterygoid causes lateral deviation of the mandible to the opposite (contralateral) side.
- 5. Hyoid, Facial Expression & Neck Musculature
- Hyoid Musculature
Suprahyoid Muscles (Digastric, Mylohyoid, Geniohyoid, Stylohyoid): Located superior to the hyoid bone. They elevate the hyoid bone during swallowing and assist in depressing the mandible when the hyoid is fixed.
Innervation Note: Anterior belly of digastric and mylohyoid = V3. Posterior belly of digastric and stylohyoid = CN VII. Geniohyoid = C1 via CN XII.
Infrahyoid Muscles (Sternohyoid, Sternothyroid, Omohyoid, Thyrohyoid): Located inferior to the hyoid bone ("strap muscles"). They depress the hyoid bone and larynx during swallowing and speech.
Muscles of Facial Expression
Derived from the second branchial arch (hyoid arch) and innervated by CN VII (Facial nerve) .
Buccinator: Forms the muscular wall of the cheek; keeps food on occlusal surfaces during chewing; pierced by Stensen's duct.
Orbicularis Oris: Encircles the oral orifice; closes and protrudes lips ("kissing muscle").
Platysma: Broad sheet muscle extending from chest to lower border of mandible; depresses mandible and pulls down corners of mouth.
Zygomaticus Major & Minor: Elevate corners of mouth ("smiling muscle").
Sternocleidomastoid (SCM) & Trapezius: Innervated by CN XI (Accessory nerve) ; major neck landmarks dividing anterior and posterior cervical triangles.