Chapter 1 PP (2022 Peacher)(1)

Objectives

• Discuss the study of embryology, histology, and dental anatomy, and state the value of these studies for dental professionals.

  • Understand developmental processes (embryology) that affect oral structures, enabling preventive guidance and early diagnosis.

  • Recognize microscopic anatomy (histology) to interpret pathology reports and guide tissue-related therapies.

  • Master macroscopic tooth form (dental anatomy) for accurate charting, restorative contours, occlusal harmony, and patient education.

• Define key terms

  • Embryology: study of prenatal development from fertilization through 8 weeks (embryonic period) and 9 weeks to birth (fetal period).

  • Histology (microscopic anatomy): study of tissues and their cellular organization.

  • Related vocabulary: morphogenesis, cytodifferentiation, organogenesis, epithelium, connective tissue, etc.

• Apply correct dental terminology in written and verbal communication with peers and patients.

• Locate and label

  • Regions & surface landmarks of face and neck.

  • Structures of oral cavity and pharynx visible in extra- and intra-oral exams.

• Integrate surface anatomy into patient examination

  • Palpate targeted areas (e.g., lymph nodes, salivary glands, TMJ) and record findings.

• Describe & label landmarks of the lips and nose.

• Correlate anatomic regions/landmarks with esthetic and functional considerations in treatment planning.

Study Strategies & Clinical Considerations

• Red “Clinical Consideration” boxes (clipboard icon) in each chapter emphasize examination tips, pathology alerts, and procedural pearls.

• Recommended reading method: SQ3R

  1. Survey (skim headings/figures)

  2. Question (turn headings into self-tests)

  3. Read (detailed pass)

  4. Recite (summarize aloud)

  5. Review (short, spaced sessions)

• Read before lecture to maximize comprehension & participation.

Eight Regions of the Face

1. Frontal

2. Orbital

3. Nasal

4. Infraorbital

5. Zygomatic

6. Buccal

7. Oral

8. Mental

• Cervicofacial lymph nodes (detailed in BIO 136) reside throughout these regions; palpable nodes and all abnormal findings must be charted.

1. Frontal Region

• Extends from hairline to supra-orbital rims; includes entire forehead and area superior to eyes.

• Frequent site for assessing facial symmetry, skin lesions, trauma.

2. Orbital Region

• Bony orbit houses eyeball, extra-ocular muscles, lacrimal apparatus, nerves & vessels.

• Periorbital puffiness or asymmetry may indicate systemic or sinus pathology.

3. Nasal Region

• Root (between eyes), bridge (superior bony part), dorsum, and apex (tip).

• Each side of apex: naris (plural nares).

• Nasal septum forms midline partition.

• Ala: lateral wall of each naris; palpate for baseline contour, piercings, pathology.

4. Infraorbital Region

• Situated inferior to orbital rims and lateral to nose.

• Important for infra-orbital nerve block; careful needle placement avoids hematoma.

5. Zygomatic Region

• Overlies zygomatic arch (cheekbone) that spans from lateral orbital margin to mid-ear.

• Trauma may compromise infra-orbital nerve & ocular support.

6. Buccal Region

• Soft tissues of cheek; bulk composed of buccal fat pad & muscles (notably masseter).

• Parotid salivary gland extends from zygomatic arch to mandibular angle; palpated extra-orally.

  • Swelling/pain signals mumps, parotitis, neoplasm, or ductal obstruction.

7. Oral Region

• Contains lips & oral cavity.

• Oral cavity subdivisions

  • Oral vestibules (labial & buccal)

  • Jaws with alveolar processes and teeth

  • Oral cavity proper (bounded by dental arches & extends to oropharynx)

Lip Landmarks

• Vermilion border: sharp red margin; transition zone = mucocutaneous junction.

• Philtrum: midline vertical groove from nasal septum to upper lip.

• Tubercle: central fullness at lower end of philtrum.

• Labial commissure: corner where upper & lower lips meet.

Clinical Consideration – Vermilion Disruption

• Trauma, herpetic lesions, scar from actinic (solar) cheilitis may blur vermilion border → hampers shade matching & incisal edge positioning.

Underlying Structures

• Upper lip supported by maxilla; lower lip by mandible.

• Sharp angle just inferior to earlobe = angle of the mandible (palpation landmark for fractures or lymphadenopathy).

8. Mental Region (Chin)

• Prominence under lower lip; skeletal basis = anterior mandible.

• Mandibular symphysis: midline fusion line seen in infants; palpable ridge.

Mandibular Anatomy (palpable / visible)

• Ramus: broad flat plate rising from posterior body.

• Anterior border → tapers superiorly into coronoid process; concave coronoid notch just inferior.

• Posterior border → widens into condylar neck and mandibular condyle; articulates with temporal bone forming temporomandibular joint (TMJ).

• Between coronoid & condyle: mandibular notch.

Facial Esthetics & Golden Proportions

• Face divides into three roughly equal vertical thirds (trichion–glabella, glabella–subnasale, subnasale–menton).

  • Assessed to diagnose skeletal discrepancies, open bite, or prosthetic vertical dimension of occlusion (VDO).

• Golden Proportions (approx. 1 : 0.618 ratios) guide width relationships (e.g., inter-canine vs. inter-pupillary distance) and restorative smile design

Landmarks of the Neck Region

• Anterior Triangle: Bounded by the sternocleidomastoid muscle, the midline of the neck, and the inferior border of the mandible. This region contains vital structures such as the carotid artery, internal jugular vein, and parts of the thyroid gland.

• Posterior Triangle: Bounded by the sternocleidomastoid muscle, the trapezius muscle, and the clavicle. Key contents include the brachial plexus, subclavian artery, and accessory nerve (CN XI).

• Hyoid Bone: A unique U-shaped bone situated in the anterior neck between the mandible and the thyroid cartilage, notable for not articulating directly with any other bone.

• Thyroid Cartilage (Adam's Apple): The largest cartilaginous structure of the larynx, easily palpable and more prominent in males.

• Cricoid Cartilage: A complete ring of cartilage located inferior to the thyroid cartilage, delineating the inferior border of the larynx.

• Trachea: Can be palpated in the midline of the neck, inferior to the cricoid cartilage, extending into the thorax.

• Sternocleidomastoid Muscle (SCM): A prominent, superficial muscle that obliquely crosses the side of the neck, serving as a key landmark and boundary for the neck triangles.

• Trapezius Muscle: A large, superficial muscle covering the back of the neck and upper trunk, forming the posterior boundary of the posterior triangle.

• Clavicle (Collarbone): A long bone that forms the inferior boundary of the posterior triangle.

• Jugular Notch (Suprasternal Notch): The easily palpable depression at the superior border of the manubrium of the sternum, serving as a reference point for thoracic structures.