3.4 Oral and Facial Landmarks, Facial and Tongue Muscles, Paranasal Sinuses & Cervical Lymph Nodes
Key Takeaways
The muscles of facial expression, including orbicularis oris, buccinator and mentalis, are supplied by the facial nerve (CN VII).
The hypoglossal nerve (CN XII) supplies all tongue muscles except palatoglossus, and genioglossus is the muscle that protrudes the tongue.
The parotid papilla opposite the maxillary second molar marks the opening of Stensen's duct; the sublingual caruncles beside the lingual frenum open Wharton's ducts.
The maxillary sinus lies above the maxillary premolar and molar roots, so sinusitis can cause referred tooth pain and an extraction can create an oroantral communication.
Mandibular incisors drain first to the submental nodes, most other teeth to the submandibular nodes, and all head and neck lymph ultimately reaches the deep cervical nodes.
3.4 Oral and Facial Landmarks, Facial and Tongue Muscles, Paranasal Sinuses & Cervical Lymph Nodes
Quick Answer: Domain 2 expects you to identify the landmarks of the face and oral cavity (2.1.1, 2.2.2), the muscles of the face and oral cavity and their actions (2.2.4), the paranasal sinuses (2.2.6) and the cervical lymph nodes (2.2.8). Know these well enough to chart findings, palpate during extraoral exams, place impression trays and receptors, and explain referred pain. The muscles of facial expression are supplied by the facial nerve (CN VII), and the tongue is moved mainly by the hypoglossal nerve (CN XII). The maxillary sinus sits directly above the maxillary posterior roots. Lymph from most teeth drains first to the submandibular nodes, but the mandibular incisors drain to the submental nodes.
1. Landmarks of the Face
| Landmark | Location | Why it matters to the assistant |
|---|---|---|
| Ala of the nose | Winged outer edge of each nostril | The ala–tragus line orients the head for bisecting-angle radiographs (maxillary occlusal plane parallel to the floor) and guides the denture occlusal plane |
| Tragus | Cartilage flap in front of the ear canal | Reference for the ala–tragus line and the Frankfort plane (pano positioning) |
| Nasion / glabella | Midpoint between the eyes / smooth area between the eyebrows | Reference points for facial measurements and cephalometrics |
| Philtrum | Vertical groove from the nose to the upper lip | Midline reference for denture setup and orthodontic photographs |
| Vermilion zone and border | Red part of the lips and its junction with skin | Common site of actinic damage, herpes labialis and cancer; inspect at every exam |
| Labial commissures | Corners of the mouth | Angular cheilitis; protect with lubricant during long procedures |
| Nasolabial sulcus | Groove from the ala to the corner of the mouth | Deepens when vertical dimension is lost |
| Labiomental groove | Horizontal groove between the lower lip and the chin | Deepened in Class II division 1 profiles |
| Mental protuberance | Bony prominence of the chin | Chin rest position in panoramic imaging |
| Angle of the mandible | Lower posterior corner of the mandible | Palpation landmark for the TMJ and the submandibular region |
2. Landmarks of the Oral Cavity
- Vestibule: the space between the lips/cheeks and the teeth. The deepest point is the mucobuccal (or mucolabial) fold, where impression borders must reach.
- Frena: folds of tissue attaching the lip or cheek to the alveolar mucosa (maxillary and mandibular labial frena, buccal frena) and the tongue to the floor of the mouth (lingual frenum). Trays and dental dam must be relieved around them.
- Attached gingiva and alveolar mucosa: firm pink attached gingiva meets red, movable alveolar mucosa at the mucogingival junction.
- Parotid papilla: on the buccal mucosa opposite the maxillary second molar; the opening of Stensen's duct (dry-angle placement).
- Linea alba: a white line on the buccal mucosa along the occlusal plane. Fordyce granules: small yellow spots (normal ectopic sebaceous glands). Both are normal and need no treatment.
- Hard palate: incisive papilla behind teeth 11 and 21 (nasopalatine injection site), palatine rugae (irregular ridges) and the median palatine raphe. Torus palatinus is a benign bony growth in the midline.
- Soft palate and uvula: the movable posterior palate. The vibrating line where the hard and soft palate meet marks the posterior border of a maxillary denture.
- Fauces: the opening to the oropharynx, bounded by the anterior faucial pillar (palatoglossal arch) and posterior faucial pillar (palatopharyngeal arch). The palatine tonsils lie between them.
- Tongue:
- The dorsum carries filiform papillae (most numerous, no taste buds), fungiform papillae (red dots with taste buds), foliate papillae (lateral border) and 8 to 12 large circumvallate papillae arranged in a V in front of the sulcus terminalis.
- The ventral surface shows the lingual veins and the plica fimbriata.
- The lateral and ventral surfaces are high-risk sites for oral cancer.
- Floor of the mouth: the sublingual caruncles (openings of Wharton's ducts) beside the lingual frenum, and the sublingual folds. Mandibular tori are bony growths on the lingual of the premolar region.
- Retromolar pad (behind the last mandibular molar) and maxillary tuberosity (behind the last maxillary molar): impression and denture landmarks.
3. Muscles of the Face and Oral Cavity
Muscles of facial expression (all supplied by the facial nerve, CN VII)
| Muscle | Action | Clinical relevance |
|---|---|---|
| Orbicularis oris | Encircles the mouth; closes and purses the lips | Lip tension can dislodge trays; affects lip support of dentures |
| Buccinator | Compresses the cheek against the teeth during chewing and blowing | Pierced by the parotid duct; controls the buccal flange of dentures; holds food on the occlusal table |
| Mentalis | Raises and protrudes the lower lip and wrinkles the chin | A strong mentalis can lift a mandibular denture or impression |
| Zygomaticus major and minor | Raise the corners of the mouth (smiling) | Lost in facial nerve paralysis after an IANB misplaced into the parotid gland |
| Risorius | Pulls the corners of the mouth laterally | Contributes to a "grimace" |
| Levator labii superioris | Raises the upper lip | — |
| Depressor anguli oris / depressor labii inferioris | Pull the corners and the lower lip down | — |
| Platysma | Tenses the skin of the neck and depresses the mandible slightly | — |
Muscles of the floor of the mouth and suprahyoid group
- Mylohyoid (nerve to mylohyoid, from V3): forms the muscular floor of the mouth and elevates the tongue and hyoid. It attaches to the mylohyoid ridge, which limits mandibular denture and receptor placement.
- Digastric: its anterior belly (V3) and posterior belly (VII) depress the mandible and raise the hyoid.
- Geniohyoid and stylohyoid: elevate and move the hyoid during swallowing.
Tongue and soft palate
- Intrinsic muscles change the tongue's shape. Extrinsic muscles move it: genioglossus protrudes the tongue (the "stick out your tongue" muscle), hyoglossus depresses it, styloglossus retracts and elevates it, and palatoglossus raises the back of the tongue.
- The hypoglossal nerve (CN XII) supplies all tongue muscles except palatoglossus (vagus, CN X).
- The soft palate is raised by levator veli palatini and tensed by tensor veli palatini (V3). This closes off the nasopharynx during swallowing and helps control the gag reflex.
4. Paranasal Sinuses
The paranasal sinuses are air-filled spaces lined with mucous membrane. They lighten the skull, give resonance to the voice, and warm and humidify inhaled air. Each drains into the nasal cavity.
| Sinus | Location | Dental relevance |
|---|---|---|
| Maxillary (largest) | Body of each maxilla, above the premolar and molar roots | Appears as a large radiolucency on maxillary posterior periapicals. Sinusitis can cause referred pain in the maxillary posterior teeth. An extraction or implant can create an oroantral communication |
| Frontal | Frontal bone above the orbits | Seen on extraoral images; sinus headache |
| Ethmoid | Ethmoid bone between the orbits (many small air cells) | Rarely relevant chairside |
| Sphenoid | Body of the sphenoid bone | Deep; seen on CBCT and skull radiographs |
The maxillary sinus drains through an opening high on its medial wall into the middle meatus of the nose, so it drains poorly when the patient is upright. If a root tip or implant enters the sinus, or a patient reports air or fluid passing from the mouth into the nose after an extraction, tell the dentist immediately.
5. Cervical Lymph Nodes
Lymph nodes filter lymph and contain immune cells. Healthy nodes are usually not palpable. During the extraoral exam the dentist or assistant palpates both sides with the pads of the fingers, comparing left with right.
| Node group | Location | Main areas drained |
|---|---|---|
| Submental | Under the chin, between the anterior bellies of the digastrics | Mandibular incisors, the tip of the tongue, the centre of the lower lip, the chin and the anterior floor of the mouth |
| Submandibular | Along the inferior border of the mandible | Most teeth and gingiva (except the mandibular incisors and the maxillary third molars), cheeks, upper lip, lateral lower lip, anterior tongue, hard palate |
| Buccal (facial), preauricular, postauricular, occipital | Cheek, in front of and behind the ear, back of the scalp | Superficial tissues of the face and scalp |
| Superficial cervical | Along the external jugular vein, over the sternocleidomastoid | Superficial neck |
| Deep cervical (including the jugulodigastric node) | Along the internal jugular vein, deep to the sternocleidomastoid | All head and neck nodes ultimately; directly drains the posterior tongue, the maxillary third molars, the tonsils and the pharynx |
Interpreting findings:
- Lymphadenitis/infection: nodes are enlarged, tender, soft and mobile, often with a nearby dental abscess or pericoronitis.
- Possible malignancy: nodes are hard, painless and fixed to surrounding tissue, persisting more than two weeks.
- Record size, consistency, tenderness and mobility, and report any abnormal node to the dentist.
During a mandibular impression, a strong muscle raises the lower lip and lifts the tray border in the anterior vestibule. Which muscle is responsible?
Buccinator
Masseter
Risorius
Mentalis
Which lymph node group receives drainage first from the mandibular incisors and the tip of the tongue?
Preauricular nodes
Submental nodes
Submandibular nodes
Occipital nodes
The day after a maxillary first molar extraction, a patient reports that liquids pass from the mouth into the nose when drinking. What is the most likely explanation?
A hematoma in the pterygomandibular space
An oroantral communication into the maxillary sinus
A dry socket with loss of the blood clot in the socket
Paresthesia of the greater palatine nerve after injection
During an extraoral examination, which lymph node finding is most suggestive of possible malignancy and must be reported to the dentist?
Small, soft and non-tender, noticed after a recent head cold
Soft, tender and freely mobile, close to an abscessed tooth
Hard, painless and fixed, persisting longer than two weeks
Tender and mobile, appearing during an episode of pericoronitis
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