1. Functional Anatomy of the Oral Cavity and Dentition
Unit II: Oral Health
University of Ottawa Faculty of Medicine
Dr. B. Carol Janik Chief, Division of Dentistry
Children’s Hospital of Eastern Ontario
Dr. Stephanie Lauziere Staff Paediatric Dentist

2. Introduction to the Oral Health Component
Oral wellness and general health have long been considered separately
Changing perspective: putting the mouth back in the body
Primary medical care encompasses the whole body
Physicians: diagnosis of dental disease and oral health promotion
Dentists: link to medical diagnoses
Increasing awareness throughout health-related professions
Caspary G, Krol DM, et al. Perceptions of Oral Health Training and Attitudes Toward Oral Health Screenings Among Graduating Pediatric Residents. Pediatrics 2008; 122 (August):e465-e471.
Objective: To determine if pediatric residents in training are receiving the experience and knowledge required to screen children’s oral health and perform risk assessment.
Conclusions: Residents felt they should be conducting oral health risk assessments, but lacked skills and training needed.

3. Objectives List the components of the oral cavity.
Describe the muscles used in mastication and their nerve supply.
Describe the anatomy of the tooth and supporting bone in cross section and the significant features of each component.
Explain and differentiate primary and permanent dentition including normal eruption, timing, occlusion and function.
Recognize the association of dental anomalies with syndromes and identify two such associations.

4. Functions of the Oral Cavity
Oral Competence
Taste
Mastication
Digestion
Aids in swallowing
Communication
(Respiration)
Oral competence is the ability to hold food and saliva in the mouth without drooling. The specialized lining of the mouth as well as the many saliva glands provide lubrication which aide in speech, swallowing and in the digestion of food. The grinding and crushing of food, mastication, is also important for digestion. Once foods are prepared for swallowing (bolus), the tongue and the mouth push the food backward towards the esophagus. Finally, our highly coordinated and specialized speech, which is so important to communication, would not be possible without the structures of the oral cavity.

5. Oral Cavity - boundaries
Begins at the vermillion border of upper and lower lip
Extends to the palatoglossal folds immediately in front of the tonsils
Bounded by the cheeks at the sides
Hard and soft palate form the roof
Bounded below by the floor of the mouth
The upper jaw (maxilla) and lower jaw (mandible) support the teeth

6. Oral Cavity - components
Upper and lower dental arches
teeth and supporting structures
Vestibule of the mouth
region between the teeth and inner surface of the lips (labial) and cheeks (buccal)
opening of parotid duct
Oral cavity proper
upper and lower dental arches
anterior two-thirds of the tongue
submandibular ducts
multiple small ducts of sublingual glands

7. Oral Cavity - structures
Indicate regions: Vestibule,labial and buccal : Oral cavity proper

8. Oral Cavity - structures
Tongue
anterior anterior two-thirds is visible in the oral cavity
dorsal surface is rough with minute papillae and taste buds
ventral surface is smooth with two thin serrated folds
frenulum controls range of movement
Floor of the mouth
forms the roof of the sublingual spaces
lined by mucous membrane
attaches to the inner surface of the body of the mandible where it becomes continuous with the mucoperiosteum of the gum on the lingual side of the teeth
centrally, becomes continuous with the mucous membrane covering the anterior two-thirds of the tongue
freely movable in association with the great mobility of the tongue, except at the mandibular attachment
ducts of submandibular and sublingual salivary glands and numerous mucous glands open

9. CASE:
A three-year-old boy is brought in by his mother for evaluation of a tongue deformity.
The lingual frenulum is short and thickened and the tongue is notched at the tip.
The mother wonders whether her son's speech problem is related to this condition.
WHAT IS YOUR DIAGNOSIS?

10. Ankyloglossia (tongue-tie)
A tongue deformity in which the lingual frenulum appears abnormally short and thick.
In extreme cases causes a fusion of the tongue to the anterior floor of the mouth.
Reported incidence is > 1%.
Probably results from disruption of the formation of the oral vestibule by an ingrowth of ectoderm.
Parents often blame it for articulation disorders, but its actual interference with speech development is reportedly rare.
If the child can protrude the tongue to the incisor teeth, lingual function for speech probably will not be affected.
In the absence of major difficulty with sucking, treatment is usually not indicated before age four, considering the possibilities of bleeding, infection, and scar formation.

11. Oral Cavity - structures
Roof of the mouth
Hard palate formed primarily by palatine processes of the maxillary bones.
Soft palate is a fibromuscular septum that can be moved to close off the nasopharynx.
Cheeks
opening of duct of parotid gland (Stensen’s duct)
Mucous membrane
stratified squamous epithelium throughout the oral cavity
tightly bound to underlying bone over the alveolar processes and the hard palate forming a mucoperiosteum
firmly attached to the tongue musculature
less firmly attached to the buccinator (cheek) muscle, lip musculature and muscles of the soft palate
more loosely attached to the floor of the mouth and vestibular region, permitting greater freedom of movement of the tongue, cheeks and lips

12. Oral Cavity - structures
Teeth and gums
the alveolar processes of maxilla and mandible support the teeth
gingiva is the mucosa surrounding the tooth that is designed for chewing, attached in part to the cementum of the tooth and in part to the alveolar bone.
Retromolar region
extends from the back of the last lower molar below to the back of the last upper molar above
mucous membrane is firmly attached to the underlying muscle and bone and contains some mucous glands.

13. Oral Cavity – posterior boundary
bounded posteriorly by the palatoglossal folds immediately in front of the tonsils
opens into the oropharynx through the fauces (oropharyngeal isthmus)

14. Anatomy of the tooth and supporting bone
Calcified tissues:
enamel
dentin
cementum
Central pulp cavity:
connective tissue
blood vessels
nerves
Supporting structures:
periodontal ligament
alveolar bone
gingivae
Enamel - outer layer of the exposed tooth, hard thin translucent layer of calcified substance that envelops and protects the dentin (the main portion of the tooth structure) of the crown of the tooth.Enamel is the hardest substance in the body and is almost entirely composed of calcium salts. The hardness of enamel is an important property as the main role of enamel is to protect the softer underlying dentin of the tooth. Enamel also serves as the surface for chewing grinding and crushing of food and this is another reason for its hardness.
Dentin - the main portion of the tooth structure found just under the enamel in the crown and under the cementum in the root; makes up most of the structure the tooth, determines the size and shape of teeth; bone-like substance formed by odontoblast cells; unique structure and composition allows it to function as the substructure for rigid enamel tissue thereby providing teeth with the ability to flex and absorb tremendous functional loads without fracturing; composed of millions of tubules and the number and size of its tubules changes as you move from the periphery toward the pulp chamber - Near the pulp the tubules are very close together and the water content of this deep dentin is high - Near the enamel the tubules are far apart occupying less than 1% of the surface area. Dentin also gives the tooth its color.
Cementum is the thin layer of calcified (tough calcium deposits) tissue covering the dentine of the root and is one of four tissues that support the tooth in the jaw (the periodontium). The others tissues that support the tooth are the alveolar bone the periodontal ligament and the gingivae; adjacent with the periodontal ligament on its outer surface and is firmly fixed to dentine on its deep surface; primary function is to give attachment to collagen fibres of the periodontal ligament.
Alveolar bone: thin layer of compact bone that forms the tooth socket surrounding the roots of teeth.

15. Enamel Dentin Pulp Cementum Periodontal ligament Alveolar bone
extremely hard, highly mineralized, crystalline structure
covers and protects the crown
surface for chewing, grinding, crushing of food
Dentin
bone-like core of the tooth, substructure for rigid enamel
unique structure of dentinal tubules
Pulp
contains blood vessels and nerves, nourishes the dentin
connects to jaw’s vascular and nervous supply through root apex
Cementum
thin calcified covering of the root
Periodontal ligament
attaches root to the surrounding alveolar bone of the socket
Alveolar bone
thin layer of compact bone that forms the tooth socket surrounding the roots
Enamel - outer layer of the exposed tooth, hard thin translucent layer of calcified substance that envelops and protects the dentin (the main portion of the tooth structure) of the crown of the tooth.Enamel is the hardest substance in the body and is almost entirely composed of calcium salts. The hardness of enamel is an important property as the main role of enamel is to protect the softer underlying dentin of the tooth. Enamel also serves as the surface for chewing grinding and crushing of food and this is another reason for its hardness.
Dentin - the main portion of the tooth structure found just under the enamel in the crown and under the cementum in the root; makes up most of the structure the tooth, determines the size and shape of teeth; bone-like substance formed by odontoblast cells; unique structure and composition allows it to function as the substructure for rigid enamel tissue thereby providing teeth with the ability to flex and absorb tremendous functional loads without fracturing; composed of millions of tubules and the number and size of its tubules changes as you move from the periphery toward the pulp chamber - Near the pulp the tubules are very close together and the water content of this deep dentin is high - Near the enamel the tubules are far apart occupying less than 1% of the surface area. Dentin also gives the tooth its color.
Cementum is the thin layer of calcified (tough calcium deposits) tissue covering the dentine of the root and is one of four tissues that support the tooth in the jaw (the periodontium). The others tissues that support the tooth are the alveolar bone the periodontal ligament and the gingivae; adjacent with the periodontal ligament on its outer surface and is firmly fixed to dentine on its deep surface; primary function is to give attachment to collagen fibres of the periodontal ligament.
Alveolar bone: thin layer of compact bone that forms the tooth socket surrounding the roots of teeth.

16. The Dentition
Development of teeth and arrangement of teeth in the mouth.
Comprised of up to four distinct types of teeth, depending on the stage of development.
Incisors (Cutting teeth)
4 front most teeth per jaw, used for the initial biting of food.
straight sharp cutting edge and one root.
Canines (Cuspids)
2 (one each side) per jaw, used with the incisors to bite into/tear food.
sharp pointed edge and one root.
Premolars (Bicuspids)
2 on each side per jaw, similar to molars in form and function, used to crush and grind food.
biting surface has two broad cusps, first upper premolars usually have two roots and other premolars have one root.
Molars
2 or 3 on each side per jaw, larger than premolars, used for crushing and grinding food.
cusped crowns with prominent ridges, three to five cusps and two or three roots.
the third molars (Wisdom Teeth) can become painfully wedged (impacted) behind the 2nd molars if there is inadequate space for eruption.

18. Dentition - stages Primary/deciduous Mixed dentition
~ 6 months to ~ 6 years
Mixed dentition
~ 6 years to ~ 12 years
Permanent dentition
> 12 years
n = 20
n = variable
n = 32
grouped into incisors, canines (cuspids), molars
transitional
grouped into incisors, canines (cuspids), molars, +/- premolars (bicuspids)
grouped into incisors, canines, premolars (bicuspids), molars
smaller, whiter, more prone to wear (to be replaced)
important for maintaining space for the developing permanent dentition
both primary and permanent teeth present in varying proportion
more calcified and stronger than the primary teeth (to last a lifetime)
function for mastication

20. Occlusion The way teeth fit together
tooth contact and interdigitation
bite-relationship
Factors involved in normal occlusal development
temporomandibular joint
associated neuromusculature
teeth
Malocclusion
malalignment of teeth (dental malocclusion), crowding, spacing, tipping, rotation, dental deterioration, anomalies
jaw relationship discrepancy (skeletal malocclusion), airway, low muscle tone, oral habits (thumbsucking)

21. Arrangement of the Teeth and Occlusion

22. Mastication
Chewing action of the teeth brought about by movement of the lower jaw through the muscles of mastication
Stable occlusion
Maximum support to the muscles and joint
Unstable occlusion
muscles of mastication malfunction
increase in load/pressure on the temporomandibular joint
pain, damage, degeneration

23. Temporomandibular Joint (TMJ)
Synovial joint; mandible articulates with the base of the skull (temporal bone)
Allows functional movement of the mandible, eating, speaking, etc.
Function may be affected by the way teeth occlude
Components:
Mandibular condyle
round end of mandible; translates, rotates during function
Temporal fossa
socket where condyle fits; concave
Articular eminence
convex; condyle translates during movement
Articular disc (meniscus)
cartilage-like dense collagen; between condyle and fossa
divides joint into two compartments
Ligaments
hold disc to the condyle; help stabilize the joint
Connective tissue
holds disc to back of the joint; contains blood vessels and nerves
forms capsule that surrounds the joint

24. Muscles of Mastication
A set of complex muscles surrounding the TMJ
Masseter
Temporalis
Lateral Pterygoid
Medial Pterygoid
When relaxed and flexible, they work harmoniously with other components of the TMJ complex for proper function.

25. Masseter muscle zygomatic arch/zygomatic bone
Origin
zygomatic arch/zygomatic bone
Insertion
lateral surface of ramus and angle of mandible
Nerve supply
masseteric nerve from mandibular division of trigeminal nerve V
Action
elevates mandible
powerful chewing muscle

26. Temporalis muscle temporal fossa/temporal fascia
Origin
temporal fossa/temporal fascia
Insertion
coronoid process and anterior surface of ramus of mandible
Nerve supply
anterior and posterior deep temporal nerves from mandibular division of trigeminal nerve V
Action
elevates mandible
retracts mandible
a powerful chewing muscle

27. Lateral Pterygoid muscle
Origin
superior head: greater wing of sphenoid
inferior head: lateral surface of lateral pterygoid plate
Insertion
superior head: capsule & articular disc of TMJ
inferior head: Neck of mandible
Nerve supply
lateral pterygoid branch of mandibular division of trigeminal nerve V
Action
protracts mandible, opens mouth
*The only one of the muscles of mastication that opens the mouth

28. Medial Pterygoid muscle
Origin
Medial surface of the lateral pterygoid plate, pyramidal process of palatine bone, tuberosity of maxilla
Insertion
Medial surface of ramus and angle of mandible
Nerve supply
Medial pterygoid branch of mandibular division of trigeminal nerve V
Action
Elevates and protracts mandible
*Mirrors the masseter m. in position and action with the ramus of the mandible between

29. Oral Cavity – role in digestion
the oral cavity is the beginning of the gastrointestinal tract.
during mastication, saliva moistens and compacts the chewed food while the tongue rolls it into a bolus.
saliva contains digestive enzymes (eg. salivary amylase) which begin the breakdown of carbohydrates.
chewing increases the surface area of foods which helps to accelerate the breakdown of starch molecules into simple sugars by the digestive enzymes.
the bolus is pushed to the back of the oral cavity for swallowing and the soft palate involuntarily closes off the nasal cavity.
Almost no protein or fat digestion occurs in the oral cavity, except for the release of lingual lipase an enzyme secreted by Ebner's glands on the dorsal surface of the tongue.

30. Dental Anomalies
Variations in normal oral structures and dental anomalies can be detected as part of a thorough physical examination which includes the oral cavity.
Dental anomalies can interfere with proper oral function and impact health.
Number
Structure
Size
Shape

31. Dental Developmental Stages
Initiation
Dental lamina activity
Anomalies of tooth number
Proliferation
Development of epithelial enamel organ and formative organ of dentin and pulp
Anomalies of tooth number and size
Histodifferentiation
Continued development of tissues essential for enamel production
Anomalies of enamel structure
Morphodifferentiation
Differential growth establishes basic form and relative size
Anomalies of size and shape
Apposition
Rhythmic deposition of matrix of enamel, dentin and cementum
Anomalies of structure
Maturation
Mineralization
Anomalies of enamel quality

32. Anomalies of Tooth Number
Oligodontia
congenitally missing teeth
Supernumerary Teeth
extra teeth

33. Anomalies of Tooth Structure
Dentinogenesis Imperfecta
Heritable dentin structure abnormality
May occur with Osteogenesis Imperfecta
Amelogenesis Imperfecta
Heritable enamel defect

34. Anomalies of Tooth Shape / Size
Talon cusp
Conical supernumerary tooth

35. Conditions with Associated Dental Anomalies
Turner’s syndrome
enamel hypoplasia
Ehlers-Danlos syndrome
irregular dentin tubules with inclusions
intrapulpal calcifications
Cleidocranial dysplasia
delayed exfoliation of primary, delayed eruption of permanent teeth
supernumerary teeth
roots lack cellular cementum
Cleft Lip/Cleft Palate
congenitally missing teeth
Turner’s: 45X karyotype, females only, webbed neck, near normal IQ, cardiac
Ehlers-Danlos: x-linked; hyperelastic, fragile skin and mucosa; skin hemorrhages, scars; joint hypermobility; irregular dentin tubules with inclusions, intrapulpal calcifications
Cleidocranial Dysplasia: brachycephalic, frontal and parietal bossing; depressed nasal bridge; delayed closure of sutures/fontanels; clavicular defect; high arched palate +/- cleft
Clefting: disruption of the dental lamina, may be abnormal induction or proliferation

36. Down Syndrome (trisomy 21)
Dental Anomalies:
Microdontia
Enamel hypoplasia
Oligodontia
Supernumerary teeth
Tooth morphology
Rotated teeth
Delayed eruption

37. Ectodermal Dysplasia
Abnormal development of skin, hair, nails, teeth, sweat glands
Dental anomalies:
Conical crowns
Oligodontia
Maxillary hypoplasia
Delayed eruption
Is a group of inherited disorders involving ectodermally derived structures

38. How did we do? … a look back at the objectives
List the components of the oral cavity
Describe the muscles used in mastication and their nerve supply
Describe the anatomy of the tooth and supporting bone in cross section and the significant features of each component
Explain and differentiate primary and permanent dentition including normal eruption, timing, occlusion and function
Recognize the association of dental anomalies with syndromes and identify two such associations

39. Resources
American Head & Neck Society. Oral Cavity Cancer. <
AnneCollins.com Digestion in the Mouth: A Short Guide <
British Dental Association 3D Mouth. Dental Anatomy <
Caspary G, Krol DM, et al. Perceptions of Oral Health Training and Attitudes Toward Oral Health Screenings Among Graduating Pediatric Residents. Pediatrics 2008; 122 (August):e465-e471.
DentalFind.com—Cosmetic Dentistry Resources. Dental Glossary <
Epstein, Melvin H. MD, et al. “The Johns Hopkins Atlas of Human Functional Anatomy: Fourth Edition”. The Head and Neck. Ch. 15, page 73. The Johns Hopkins University Press, Baltimore and London.
“The Handbook”. American Academy of Pediatric Dentistry Publication.
The University of Michigan Medical School. Medical Gross Anatomy Learning Resources: Anatomy Tables/Lecture Notes/Dissector Answers—Infratemporal Fossa & Oral Cavity <
Youn W. Park, MD, Mark Matthews, MD. Emergency Medicine. Diagnosis at a Glance <

40. For further information:
Dr. B. Carol Janik
Dr. Stephanie Lauziere