ORAL ANATOMY 2 - STUDY GUIDE 0

The following questions relate to the paranasal sinuses.

a) List the bones of the skull which contain the paranasal sinuses. (2 marks)

b) List the functions of the paranasal sinuses. (2 marks)

c) Describe the changes in the paranasal sinuses with age. (2 marks)

d) Individuals who suffer from hay fever can suffer from acute maxillary sinusitis. Explain why this occurs, with reference to the position of the openings of the sinus into the nasal cavity and the type of epithelium which lines the maxillary sinuses. (2 marks)

e) What is meant by the term oroantral communication and how might it arise / occur as part of dental treatment? (2 marks)

The paranasal sinuses are air-filled cavities located within the following bones:

·       Frontal bone → Frontal sinuses

·       Ethmoid bone → Ethmoid sinuses

·       Sphenoid bone → Sphenoid sinuses

·       Maxillary bone → Maxillary sinuses

 

Functions of the Paranasal Sinuses

·       Lighten the weight of the skull

·       Humidify and warm inhaled air

·       Enhance voice resonance

·       Provide a buffer against facial trauma

·       Contribute to immune defense through mucus

Changes in the Paranasal Sinuses with Age

·       At birth: Only the maxillary and ethmoid sinuses are present in rudimentary form. (not covered in the lecture)

·       Childhood: Sinuses grow progressively, especially during puberty.

·       Adulthood: Sinuses reach full size and function.

·       Older age: Sinus walls may thin, and mucociliary function can decline, increasing susceptibility to infections.

 

Hay Fever and Acute Maxillary Sinusitis

Hay fever (allergic rhinitis) can lead to acute maxillary sinusitis due to:

Position of the sinus opening: The maxillary sinus drains into the middle meatus of the nasal cavity via the ostium, which is located high on the medial wall. This makes drainage difficult, especially when inflammation or mucus blocks the opening.

Type of epithelium

The maxillary sinus is lined with pseudostratified ciliated columnar epithelium (respiratory epithelium), which relies on ciliary movement to clear mucus. In hay fever, inflammation impairs ciliary function, leading to mucus buildup and infection

Oroantral Communication

Oroantral communication refers to an unnatural opening between the oral cavity and the maxillary sinus.

How it occurs: Most commonly during dental procedures, especially:

Extraction of upper molars or premolars (due to proximity to the sinus floor) Main answer required 

Implant placement or sinus lift surgeries (additional)

Trauma or pathology (e.g., cysts or tumours) additinal)

Clinical concern: If not properly managed, it can lead to oroantral fistula, chronic sinusitis, and persistent oral-sinus communication.

Describe the distribution of minor salivary glands within the oral cavity. 

Distribution of Minor Salivary Glands

Minor salivary glands are numerous and scattered throughout the oral cavity, primarily located in:

• Buccal mucosa (inner cheeks)

• Labial mucosa (inner lips)

• Lingual mucosa (underside and sides of the tongue)

• Soft palate

• Posterior lateral zones of the hard palate

• Floor of the mouth

• Tonsillar and supraglottic regions

• They are not found in the gingiva or the anterior medial hard palate 

Choose one of the major salivary glands. Describe the anatomical location and relationship of the gland and its associated duct to bones and muscles. 

Anatomical Location and Relationships of the Submandibular Gland

The submandibular gland is one of the major salivary glands and is located:

• Beneath the mandible, in the submandibular triangle of the neck.

• Medial to the body of the mandible, and superficial to the mylohyoid muscle.

• The submandibular duct (Wharton’s duct):

• Emerges from the deep part of the gland.

• Travels anteriorly, passing over the mylohyoid muscle.

• Opens into the oral cavity at the sublingual caruncle, near the base of the tongue 

Explain why the side effect of some medications is a dry mouth. 

Dry mouth is a common side effect of many medications due to their impact on salivary gland function:

• Anticholinergic drugs (e.g., antihistamines, antidepressants, antipsychotics) block acetylcholine, which is essential for stimulating saliva production.

• Diuretics and antihypertensives reduce body fluid levels, leading to decreased saliva.

• Chemotherapy and radiation (especially to the head and neck) can damage salivary glands directly.

• Decongestants and muscle relaxants may also reduce salivary flow 

This reduction in saliva can lead to:

• Difficulty speaking and swallowing

• Increased risk of dental decay and oral infections

• Altered taste sensation

 a)       Draw a simple cross section diagram of the temporomandibular joint from a lateral view.  Label the diagram with the following features:             (6 marks)

 

I.                  Articular eminence of the temporal bone

II.                 Articular disc

III.                Articular fossa of the temporal bone

IV.                Attachment of the muscle

V.                 Condyle of the mandible

VI.                Upper and lower synovial cavities

a) Describe some of the common symptoms and signs of temporomandibular joint dysfunction. (2 marks)

b) Describe how you would go about the examination of the temporomandibular joint and associated muscles for a patient as part of an extra-oral examination.  (2 marks)

c) Can you tell if a patient has TMJ dysfunction by examining their panoramic radiograph? Explain your answer.  (2 marks)

a) Describe some of the common symptoms and signs of temporomandibular joint dysfunction. (2 marks)

There is a long list of sysmton but for 2 marks you should list at least four sysmptoms  and signs. TMJ dysfunction, also known as temporomandibular disorder (TMD), can present with a variety of symptoms, including 

• Jaw pain or tenderness, especially around the TMJ area

• Clicking, popping, or grating sounds when opening or closing the mouth

• Limited jaw movement or locking of the jaw

• Pain while chewing or difficulty chewing

• Facial pain, especially around the temples or ears

• Ear-related symptoms such as earaches, tinnitus (ringing), or a feeling of fullness

• Headaches or migraines

• Neck and shoulder pain

• A change in occlusion (the way the teeth fit together)

b) Describe how you would go about the examination of the temporomandibular joint and associated muscles for a patient as part of an extra-oral examination.  (2 marks)

I have highlighted the answers you should include 

Observations 

• Observe the patient’s face for asymmetry, swelling, or deviation of the jaw during opening and closing.

• Note any abnormal movements or limitations in range.

Palpation:

• Place fingers over the TMJs (just anterior to the tragus of the ear) and ask the patient to open and close their mouth. Observe and feel the movement of the jaw as the patienty opens and closes. 

• Feel for crepitus, clicking, or tenderness.

• Palpate the muscles of mastication (masseter, temporalis, medial and lateral pterygoids) for tenderness or hypertrophy.

Range of Motion:

• Measure the interincisal distance (normal is ~35–50 mm).

• Assess lateral and protrusive movements.

Auscultation (optional): ( Not every practice wil keep a stethoscope for this!)

• Use a stethoscope to listen for joint sounds during movement.

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c) Can you tell if a patient has TMJ dysfunction by examining their panoramic radiograph? Explain your answer.  (2 marks)

A panoramic radiograph (OPG) can provide limited information about TMJ dysfunction:

It can show gross bony changes such as:

• Condylar erosion

• Flattening or osteophyte formation

• Asymmetry or fractures

However, it cannot assess soft tissue structures (e.g., articular disc, ligaments, or muscles), which are often involved in TMD. Also, functional issues like joint clicking or muscle pain cannot be visualized.

Conclusion: A panoramic radiograph may support a diagnosis of TMJ dysfunction but cannot confirm it alone. Clinical examination and possibly advanced imaging (e.g., MRI) are needed for a definitive diagnosis

Describe the anatomical location of the pterygomandibular fold and explain its significance to dental treatment. 3 marks 

Anatomical Location: This fold is a mucosal ridge that stretches from the hamulus of the medial pterygoid plate of the sphenoid bone to the posterior end of the mylohyoid line of the mandible. It overlies the pterygomandibular raphe, a tendinous band connecting the buccinator and superior pharyngeal constrictor muscles.

Significance in Dental Treatment: It serves as a key landmark for administering inferior alveolar nerve blocks (IANBs).

Describe the anatomical location, appearance, colour and texture of the incisive papilla. 1 mark  

Location: Found on the midline of the hard palate, just posterior to the maxillary central incisors.

Appearance:

Shape: Small, oval or pear-shaped elevation.

Colour: Similar to surrounding mucosa—pink in healthy tissue. (Sometimes brighter red in colour if it has been traumatised by hot food etc) 

Texture: Firm and slightly raised.

Clinical Relevance:

It covers the incisive foramen, through which the nasopalatine nerves and blood vessels pass.

Describe the location, appearance oof shape and contour, colour and texture of the retromolar pad. 1 mark

The retromolar pad represents the most inferior aspect of the raphe between the buccinator muscle and the superior constrictor muscle of the pharynx. 

Location: Situated posterior to the last mandibular molar, overlying the retromolar triangle.

Appearance:

Shape and Contour: Oval or triangular pad of tissue.

Colour: Pink, similar to adjacent mucosa.

Texture: Soft and compressible, containing glandular tissue (not expecting this detail) , muscle fibers, and connective tissue.

Draw a diagram of the dorsal surface of the tongue and label it with the following for ½ mark each: 

a) Anterior 2/3 and Posterior 1/3

b) Apex

c) Median sulcus  

d) Distribution of the filiform papillae

e) Distribution of the fungiform papillae 

f) Position and distribution of the follate papilla

g) Position and distribution of the circumvallate papilla

h) Terminal sulcus. 

i) Lingual tonsils 

j) Foramen caecum 

This question relates to the sensory innervations of the oral cavity. Name the nerve which supplies the following dental structures.

a)       Pulps of mandibular teeth, periodontal ligaments and supporting bone.                 

b)      Buccal gingiva and mucosa adjacent to the mandibular premolars.                 

c)       Buccal gingival and mucosa adjacent to the mandibular molars.   

d)      Lingual gingival and mucosa on the mandible and floor of the mouth.

e)      Skin and mucosa of the lower lip and chin adjacent to the mandibular anteriors.  

f)        Maxillary 2nd permanent molar and adjacent supporting structures.         

g)       Maxillary premolars and adjacent supporting structures.              

h)      Soft palate and uvula.   

i)        Palatal supporting tissue of the palate in the region posterior to the maxillary canines and incisors.

j)        Skin and mucosa of the upper lip.

Mandibular Region (CNV3 – Mandibular Division of Trigeminal Nerve)

a) Pulps of mandibular teeth, periodontal ligaments, and supporting bone

→ Inferior alveolar nerve

b) Buccal gingiva and mucosa adjacent to the mandibular premolars

→ Buccal nerve

c) Buccal gingiva and mucosa adjacent to the mandibular molars

→ Buccal nerve

d) Lingual gingiva and mucosa on the mandible and floor of the mouth

→ Lingual nerve

e) Skin and mucosa of the lower lip and chin adjacent to the mandibular anteriors

→ Mental nerve (a branch of the inferior alveolar nerve)

Maxillary Region (CNV2 – Maxillary Division of Trigeminal Nerve)

f) Maxillary 2nd permanent molar and adjacent supporting structures

→ Posterior superior alveolar nerve

g) Maxillary premolars and adjacent supporting structures

→ Middle superior alveolar nerve

h) Soft palate and uvula

→ Lesser palatine nerve

i) Palatal supporting tissue of the palate in the region posterior to the maxillary canines and incisors

→ Greater palatine nerve

j) Skin and mucosa of the upper lip

→ Infraorbital nerve

Name the three periods of prenatal development and their timespan. Which of the three period of prenatal development is most critical and why?  2 marks

a) Periods of Prenatal Development

There are three main periods of prenatal development:

1. Germinal Period (Weeks 1–2)

   • Begins at conception and lasts until the zygote implants in the uterine wall.

   • Rapid cell division and formation of the blastocyst occur.

2. Embryonic Period (Weeks 3–8)

   • Major organs and structures begin to form.

   • This is the most critical period because the foundations for all major body systems are established. Any disruption (e.g., teratogens) during this time can lead to significant congenital anomalies.

3. Fetal Period (Week 9 to Birth)

   • Growth and maturation of tissues and organs.

   • The fetus becomes more viable and functional over time.

Why the Embryonic Period is Most Critical:
This is when organogenesis occurs—meaning the basic structures of the brain, heart, limbs, and face are forming. Teratogenic exposure during this time can cause major structural defects.

Briefly describe what pharyngeal/branchial arches are in the human embryo.   Which pharnyngeal/branchial arch forms the muscles of facial expression?       2 marks

Pharyngeal (Branchial) Arches are a series of mesodermal outpouchings in the developing embryo that contribute to the formation of the head and neck structures. Each arch contains:

• A cartilage component

• A cranial nerve

• A muscular component

• An arterial component

There are six arches, but the fifth is rudimentary and often not considered.

Muscles of Facial Expression are derived from the Second Pharyngeal Arch, which is associated with the Facial Nerve (CN VII).

Give two examples of teratogens and explain which period in gestation these factors would have the most influence on facial or palatal malformation.  2 marks

Teratogens are substances or factors that can cause developmental malformations. Two examples include:

1. Alcohol

   • Can lead to Fetal Alcohol Spectrum Disorders (FASD), including facial abnormalities like a smooth philtrum, thin upper lip, and small palpebral fissures.

   • Most harmful during the embryonic period (weeks 3–8) when facial structures are forming.

2. Retinoic Acid (Vitamin A derivatives)

   • Found in acne medications like isotretinoin.

   • Can cause cleft palate, ear malformations, and craniofacial defects.

   • Most critical during weeks 4–7, when the palate and facial prominences are developing.

At what age (on average), are the first signs of mineralization in the mandibular first permanent molar?  1 mark

Around birth (late in utero, approximately 30–36 weeks gestation).

At the time of birth there are no erupted teeth, but teeth will be in various stages of development within the child’s jaws. How many teeth will be present in various stages of development. 1 mark

Calcification of all primary teeth (20) will be in various stages. Calcification of permanent first molars (4) be in intial stages. In addition the tooth germs of some other permanent teeth will be present but no signs of calcification at this stage.  There will be 44 teeth present in various stages of development and calcification. 

Describe the stage of root formation when a permanent tooth erupts into the oral cavity. 1 mark

When a permanent tooth erupts, the root is about two-thirds formed. Root development continues after eruption.

Briefly describe the process of apexification and the approximate time this takes after the tooth has erupted.  2 marks

Apexification is the process by which the root apex (tip) completes formation and closes after the tooth erupts. It involves continued deposition of dentin and cementum.

Describe how the apex is very wide in eraly stages of developemnt but as the root forms and grows longer the apex closes to a small opening .

This process typically takes about 2–3 years after eruption.

On average, at what age is root formation and apexification of the permanent central incisor complete. 1 mark

Around 9–10 years of age.

Enamel can be described as permeable. Briefly explain the clinical significance of the permeability of enamel and the microscopic features in enamel which allow this permeability.  (2 marks)

Clinical significance:

Enamel permeability allows fluoride ions and other remineralising agents to penetrate, helping prevent and reverse early caries.

It also permits acid diffusion, contributing to subsurface demineralisation in caries development.

Microscopic features:

Enamel rods and interrod substance create microporosities.

Enamel tufts, lamellae, and rod sheaths contribute to permeability pathways.

Describe the variations in thickness of enamel over the crown of the tooth. What is the maximum thickness of enamel in millimetres?    (2 marks)

Variation:

Enamel is thickest at cusp tips and incisal edges, where functional stress is greatest.

It becomes thinner toward the cervical margin of the crown.

Maximum thickness:

Up to 2.5 mm, typically on molar cusps

Describe the difference between developmental grooves and fissures by drawing a labelling a diagram. Explain the difference between a developmental groove and fissure and how they develop.  Discuss the clinical significance of fissures. (3 marks) 

Differences:

Developmental grooves: Shallow linear depressions marking the fusion of developmental lobes.

Fissures: Deep, narrow clefts formed when lobes fail to fuse completely during development.

Development:

Grooves form from normal lobe fusion.

Fissures result from incomplete fusion, often in posterior teeth.

Clinical significance of fissures:

Fissures are plaque-retentive, difficult to clean, and high-risk sites for dental caries.

Often require sealants or restorative treatment.

Describe the appearance of perikymata and explain how these features develop.  Where on the surface of a tooth would these features be most visible?   (3 marks)

Appearance:

Fine, horizontal ridges or lines on enamel surface.

Development:

Result from the incremental deposition of enamel, corresponding to the striae of Retzius.

Location:

Most visible on the facial surfaces of anterior teeth, especially near the cervical third.

This question relates to the alveolar process.

a) Explain the difference between the basal bone, alveolar process and alveolar bone as discussed in the lectures. Draw a diagram to illustrate your answer (2 marks)

b) Compare the buccal and lingual cortical bone on the alveolar process of the maxillary bone and the mandibular bone. How does this influence the delivery and effectiveness of local anaesthesia?  (4 marks)

c) Briefly describe how a tooth moves through bone when horizontal orthodontic forces are placed on the tooth with reference to the periodontal ligament, cementum and lamina dura.    (4 marks)

Basal bone is the osseous tissue that lies deep to  the alveolar process, it provides the body of the mandible and maxilla. Extending from that basal bone is the alveolar process which is a thickened ridge of bone which provides the support which surrounds the sockets of the teeth. The alveolar bone proper is the area of bone which lines the tooth socket, where the periodontal ligament attaches the tooth to the bone.

In the maxillary bone, the buccal cortical bone is more porous as compared to the lingual cortical bone which is more dense. That is why the infiltration technique is used in the buccal region on maxillary teeth to anaesthetise the pulps. When injecting on the palate, this is more to numb the soft tissues surrounding the area as diffusion through the more dense lingual cortical bone is not effective. When considering the mandibular buccal and lingual cortical bone, it is very dense and therefore the infiltration technique is not possible to anaesthetise the pulps. Moving more anteriorly, infiltration can be used if needed as the cortical bone becomes thinner in the anterior buccal/labial region.

When horizontal tooth movement occurs by orthodontics, it is made possible by bone resorption taking place in the direction the tooth is being moved. This means that as pressure is placed on the alveolar bone in the direction of movement, the periodontal ligament on the opposing side is being put under tension. The cementum and periodontal ligament are also remodelled in response to the tension created by the movement. As bone resorption occurs on one surface of the lamina dura, the tooth is able to move into that space in that direction and bone is deposited on the opposing side to rebuild where the tooth has moved from to stabilise it in the new position.

You could also add information about the roles of osteoblasts/osteoclasts cementoblasts/ cementoclasts etc to demonstrate your understanding of the roles of the cells in remodelling periodontal ligament and bone etc 

In some areas of the oral cavity the oral mucosa is described by the term mucoperiosteum. Where in the oral cavity is this type of mucosa and why is it described in this way? Your answer should describe the microscopic layers of oral mucosa.  2 marks

The mucoperiosteum can be found on the hard palate and attached gingiva. It is so called this as it is where mucosa is bound with the periosteum in the absence of the submucosal layer. It is comprised of a keratinised outer epithelium lining the loose connective tissue called lamina propria which is connected directly attached to the periosteum of the underlying bone beneath the mucosal membrane.

Drugs used to treat angina are often administered by placing the medication under the tongue on the floor of the mouth. Describe the type of oral mucosa and contents of the submucosa here and why this route of administration is effective. 3 marks 

The epithelium is typical non-keratinised lining mucosa which is thin with underlying lamina propria and submucosa. The epithelium is composed of a the stratum basale (basal layer of cuboidal cells), stratum spinosum (second layer of oval and flattened cells) and stratum superficiale (third superficial layer of flattened cells). The submucosa here is thick and loose, containing salivary glands, blood vessels, nerves and adipose tissue. This means that administering medication in the area under the tongue is effective as it can easily reach the blood stream due to the thin epithelium and through the high vascularity of the underlying connective tissue, to take effect in a timely manner.

Discuss the function of the junctional epithelium and how it changes during tooth eruption and with disease.  3 marks 

The junctional epithelium is a highly permeable epithelial structure that attaches the gingiva to the tooth surface and forms the floor of the gingival sulcus. Its permeability allows gingival crevicular fluid and immune cells to pass into the sulcus for host defence, while bacterial products and antigens can pass into the underlying connective tissue. Before eruption, the reduced enamel epithelium covers the tooth and is attached to the enamel via hemidesmosomes. During eruption, the reduced enamel epithelium fuses with the oral epithelium as the gingival sulcus forms. In a partially erupted tooth, the junctional epithelium is attached to enamel; after eruption, it is located around the cementoenamel junction. With periodontal disease, inflammation causes the junctional epithelium and its attachment to migrate apically along the root surface, resulting in periodontal pocket formation and exposure of cementum.

Draw a diagram to demonstrate the gingival sulcus, sulcular epithelium and junctional epithelium. 2 marks 

How much saliva do we produce in a day and how does the secretion of saliva vary during the day and night?  2 marks

1.4L of saliva is secreted each day. The rate of salivation is minimal during most of the day and night, at about 0.1mL per minute during sleep, but upon stimulation, the flow is high and can be 1mL per minute +/-

What factors might influence the volume of saliva we produce?  2 marks 

Volume of secretion is dependent on stimulation by taste, smell and mastication. The taste and smell play a major role in influencing the salivary flow. The nerve endings in the periodontal ligament and muscles of mastication also play a part. Other factors include sleep, postural position, the level of hydration, diseases present, radio/chemo therapy, medications (prescription and recreational), anxiety, age.

Explain the terms stimulated and unstimulated saliva and the difference in composition and pH between stimulated and unstimulated saliva.  2 marks 

Stimulated saliva is saliva produced when the salivary glands are activated by stimuli such as chewing, taste, or smell. Unstimulated saliva is the continuous baseline secretion produced without deliberate stimulation.

• Unstimulated saliva: mainly produced by the submandibular and sublingual glands; has a lower flow rate and lower pH, with relatively higher concentrations of proteins and antimicrobial components.

• Stimulated saliva: produced mainly by the parotid glands; has a higher flow rate and higher pH, with increased bicarbonate concentration, giving it greater buffering capacity.

Easy exam sentence: Stimulated saliva has a higher flow rate, higher pH and bicarbonate concentration, whereas unstimulated saliva has a lower flow rate and pH and is richer in proteins/antimicrobial components.

What is meant by the term odontogenic infection? What other terms are used instead of odontogenic infection? (2 marks)

An odontogenic infection is an infection involving the teeth and its associated tissues, including the alveolar process, oral mucosa, paranasal sinuses, adjacent structures to the oral cavity. These infections can also be named as dental infections, dento-alveolar infections and dento-facial infections.

The pus from an infected periapical region of a tooth will often drain via a tract onto the outside of the alveolar process adjacent to the tooth root. What is the tract called? What is the name for the opening of the tract onto the mucosa? What is a common name for the opening of the track? Explain why the pus drains in this direction. (2 marks) 

The tract is called a fistula and the opening of the tract onto the mucosa is the stoma. The common name is gum boil. The pus drains via a tract in this direction as the infection needs a way to allow drainage to help prevent the infection becoming worse. It forms a tract to the oral mucosa as it forms in the "pathway of least resistance", where bone is the thinnest and least resistant. The direction that the tract takes can also be influenced by the position of muscle attachments and the fascia surrounding the muscles as they are resistant to breakdown from infection and cannot pass through them, so the infection will travel down the direction the fascia goes before reaching the surface on the oral mucosa instead of in a linear direction straight to the surface.

A patient has a swollen face as result of an infected tooth. The swelling is located beneath the eye and over the cheek. The skin overlying the swelling is slightly red and feels warm to touch. What is the name for this diffuse swelling?  With your knowledge of the spread of infection, which teeth or groups of teeth are possibly responsible? (2 marks) 

The swelling of tissues is called cellulitis. The canine or one of the maxillary posterior teeth are likely responsible for the swelling in this area.  Canines and premolars are more likely. Canine infections often cause swelling beneath the eye.

A patient complains of toothache in a maxillary molar, but you suspect the cause of their pain is not their tooth but infected sinuses. What are the typical signs and symptoms of acute sinusitis and what symptoms might they complain of regarding their teeth? (2 marks) 

Signs and symptoms of acute sinusitis are foul smelling purulent nasal/pharyngeal discharge, warm and red skin over the facial sinus area, tender face, headache over the bones with feeling of pressure build-up which can be felt when tipping the head forward, and there may be difficulty breathing if there is nasal congestion  If the root apices of the posterior teeth are in close proximity to or extending into the sinuses, a patient may then complain of pain in their teeth, like sensitivity and pain on pressure or percussion due to the inflammation being cause around the area from the sinusitis.