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DENTAL ANATOMY & PHYSIOLOGY Physiology, Etiology, Epidemiology, Diagnosis, and Treatment Dental Anatomy and Physiology After viewing this lecture, attendees should be able to:
Identify the major structures of the dental anatomy
Discuss the primary characteristics of enamel, dentin, cementum, and dental pulp
Describe the biologic functions that take place within the oral cavity Dental Anatomy and Physiology Primary (deciduous)
Secondary (permanent) Definition (teeth): There are two definitions Dental Anatomy and Physiology A tooth is made up of three elements:
Water
Organic materials
Inorganic materials Elements Primary (deciduous)
Consist of 20 teeth
Begin to form during the first trimester of pregnancy
Typically begin erupting around 6 months
Most children have a complete primary dentition by 3 years of age
Dental Anatomy and Physiology Dentition (teeth): There are two dentitions 1. Oral Health for Children: Patient Education Insert. Compend Cont Educ Dent. Dental Anatomy and Physiology Secondary (permanent)
Consist of 32 teeth in most cases
Begin to erupt around 6 years of age
Most permanent teeth have erupted by age 12
Third molars (wisdom teeth) are the exception; often do not appear until late teens or early 20s Dentition (teeth): There are two dentitions Mandible Maxilla Incisors Canine (Cuspid) Premolars Molars Classification of Teeth:
Incisors (central and lateral)
Canines (cuspids)
Premolars (bicuspids)
Molars
Dental Anatomy and Physiology Identifying Teeth Incisor Canine Premolar Molar Dental Anatomy and Physiology Identifying Teeth2 Incisor Canine Premolar Molar Incisors function as cutting or shearing instruments for food.
Canines possess the longest roots of all teeth and are located at the corners of the dental arch.
Premolars act like the canines in the tearing of food and are similar to molars in the grinding of food.
Molars are located nearest the temporomandibular joint (TMJ), which serves as the fulcrum during function.
Dental Anatomy and Physiology Apical
Labial
Lingual
Distal
Mesial
Incisal Teeth: Identification
Tooth Surfaces Labial Apical Lingual Distal Apical Mesial Incisal Incisal
Dental Anatomy and Physiology Apical: Pertaining to the apex or root of the tooth
Labial: Pertaining to the lip; describes the front surface of anterior teeth
Lingual: Pertaining to the tongue; describes the back (interior) surface of all teeth
Distal: The surface of the tooth that is away from the median line
Mesial: The surface of the tooth that is toward the median line
Labial Apical Lingual Distal Apical Mesial Enamel Alveolar Bone Pulp Chamber Dental Anatomy and Physiology Enamel (hard tissue)
Dentin (hard tissue)
Odontoblast Layer
Pulp Chamber (soft tissue)
Gingiva (soft tissue)
Periodontal Ligament (soft tissue)
Cementum (hard tissue)
Alveolar Bone (hard tissue)
Pulp Canals
Apical Foramen
The Dental Tissues: Dentin Odontoblast Layer Gingiva Periodontal Ligament Cementum Pulp Canals Apical Foramen Anatomic Crown
Anatomic Root
Pulp Chamber The 3 parts of a tooth: Anatomic Crown Anatomic Root Pulp Chamber Dental Anatomy and Physiology Anatomic Crown Anatomic Root Pulp Chamber Dental Anatomy and Physiology The anatomic crown is the portion of the tooth covered by enamel.
The anatomic root is the lower two thirds of a tooth.
The pulp chamber houses the dental pulp, an organ of myelinated and unmyelinated nerves, arteries, veins, lymph channels, connective tissue cells, and various other cells.
Enamel
Dentin
Cementum
Dental Pulp
The 4 main dental tissues: Dental Anatomy and Physiology Enamel Dentin Cementum Dental Pulp Structure
Highly calcified and hardest tissue in the body
Crystalline in nature
Enamel rods
Insensitive—no nerves
Acid-soluble—will demineralize at a pH of 5.5 and lower
Cannot be renewed
Darkens with age as enamel is lost
Fluoride and saliva can help with remineralization Dental Anatomy and Physiology Dental Tissues—Enamel2 Dental Tissues—Enamel2 Dental Anatomy and Physiology Enamel can be lost by:3,4
Physical mechanism
Abrasion (mechanical wear)
Attrition (tooth-to-tooth contact)
Abfraction (lesions)
Chemical dissolution
Erosion by extrinsic acids (from diet)
Erosion by intrinsic acids (from the oral cavity/digestive tract)
Multifactorial etiology
Combination of physical and chemical factors
Softer than enamel
Susceptible to tooth wear (physical or chemical)
Does not have a nerve supply but can be sensitive
Is produced throughout life
Three classifications
Primary
Secondary
Tertiary
Will demineralize at a pH of 6.5 and lower Dental Tissues—Dentin2 Dental Anatomy and Physiology Three classifications:
Primary dentin forms the initial shape of the tooth.
Secondary dentin is deposited after the formation of the primary dentin on all internal aspects of the pulp cavity.
Tertiary dentin, or “reparative dentin” is formed by replacement odontoblasts in response to moderate-level irritants such as attrition, abrasion, erosion, trauma, moderate-rate dental caries, and some operative procedures.
Dental Tissues—Dentin2 Dental Anatomy and Physiology
Dentin Pulp Tubule Fluid Nerve Fibers Odontoblast Cell Dental Anatomy and Physiology Dental Tissues—Dentin (Tubules)2 Dentinal tubules connect the dentin and the pulp (innermost part of the tooth, circumscribed by the dentin and lined with a layer of odontoblast cells)
The tubules run parallel to each other in an S-shape course
Tubules contain fluid and nerve fibers
External stimuli cause movement of the dentinal fluid, a hydrodynamic movement, which can result in short, sharp pain episodes
Dental Anatomy and Physiology Presence of tubules renders dentin permeable to fluoride
Number of tubules per unit area varies depending on the location because of the decreasing area of the dentin surfaces in the pulpal direction Dental Tissues—Dentin (Tubules)2 Association between erosion and dentin hypersensitivity3
Open/patent tubules
– Greater in number
– Larger in diameter
Removal of smear layer
Erosion/tooth wear
Enamel Exposed Dentin Receding Gingiva Tubules Odontoblast Dental Anatomy and Physiology Dental Tissues—Dentin (Tubules)2 Dental Anatomy and Physiology Thin layer of mineralized tissue covering the dentin
Softer than enamel and dentin
Anchors the tooth to the alveolar bone along with the periodontal ligament
Not sensitive
Dental Tissue—Cementum2 Innermost part of the tooth
A soft tissue rich with blood vessels and nerves
Responsible for nourishing the tooth
The pulp in the crown of the tooth is known as the coronal pulp
Pulp canals traverse the root of the tooth
Typically sensitive to extreme thermal stimulation (hot or cold) Dental Tissue—Dental Pulp2 Dental Anatomy and Physiology Pulpitis is inflammation or infection of the dental pulp, causing extreme sensitivity and/or pain.
Pain is derived as a result of the hydrodynamic stimuli activating mechanoreceptors in the nerve fibers of the superficial pulp (A-beta, A-delta, C-fibers).
Hydrodynamic stimuli include: thermal (hot and cold); tactile; evaporative; and osmotic
These stimuli generate inward or outward movement of the fluid in the tubules and activate the nerve fibers.
A-beta and A-delta fibers are responsible for sharp pain of short duration
C-fibers are responsible for dull, throbbing pain of long duration
Pulpitis may be reversible (treated with restorative procedures) or irreversible (necessitating root canal).
Untreated pulpitis can lead to pulpal necrosis necessitating root canal or extraction. Dental Tissue—Dental Pulp2,5 Dental Anatomy and Physiology Gingiva
Alveolar Bone
Periodontal Ligament
Cementum Periodontal Tissues6 Dental Anatomy and Physiology Gingiva Alveolar bone Cementum Periodontal Ligament Gingiva: The part of the oral mucosa overlying the crowns of unerupted teeth and encircling the necks of erupted teeth, serving as support structure for subadjacent tissues.
Dental Tissue—Dental Tissue6 Dental Anatomy and Physiology Gingiva Alveolar Bone: Also called the “alveolar process”; the thickened ridge of bone containing the tooth sockets in the mandible and maxilla.
Dental Tissue—Dental Tissue6 Dental Anatomy and Physiology Alveolar bone Periodontal Ligament: Connects the cementum of the tooth root to the alveolar bone of the socket.
Dental Tissue—Dental Tissue6 Dental Anatomy and Physiology Periodontal Ligament Cementum: Bonelike, rigid connective tissue covering the root of a tooth from the cementoenamel junction to the apex and lining the apex of the root canal. It also serves as an attachment structure for the periodontal ligament, thus assisting in tooth support. Dental Tissue—Dental Tissue6 Dental Anatomy and Physiology Cementum Plaque
Saliva
pH Values
Demineralization
Remineralization
Oral Cavity/Environment7,8 Dental Anatomy and Physiology Dental Anatomy and Physiology Plaque:7,8
is a biofilm
contains more than 600 different identified species of bacteria
there is harmless and harmful plaque
salivary pellicle allows the bacteria to adhere to the tooth surface, which begins the formation of plaque Oral Cavity Dental Anatomy and Physiology Saliva:7,8
complex mixture of fluids
performs protective functions:
lubrication—aids swallowing
mastication
key role in remineralization of enamel and dentin
buffering Oral Cavity Dental Anatomy and Physiology pH values:7,8
measure of acidity or alkalinity of a solution
measured on a scale of 1-14
pH of 7 indicated that the solution is neutral
pH of the mouth is close to neutral until other factors are introduced
pH is a factor in demineralization and remineralization Oral Cavity 3. Strassler HE, Drisko CL, Alexander DC. Dental Anatomy and Physiology Demineralization:7,8
mineral salts dissolve into the surrounding salivary fluid:
enamel at approximate pH of 5.5 or lower
dentin at approximate pH of 6.5 or lower
erosion or caries can occur Oral Cavity Dental Anatomy and Physiology Remineralization:7,8
pH comes back to neutral (7)
saliva-rich calcium and phosphates
minerals penetrate the damaged enamel surface and repair it:
enamel pH is above 5.5
dentin pH is above 6.5 Oral Cavity Dental Anatomy & Physiology—References References
1. Oral Health for Children: Patient Education Insert. Compend Contin Educ Dent. 2005;26(5 Suppl 1):Insert.
2. Sturdevant JR, Lundeen TF, Sluder TB Jr. Clinical significance of dental anatomy, histology, physiology, and occlusion. In: Robertson TM, Heymann HO, Swift EJ Jr, eds. Sturdevant’s Art and Science of Operative Dentistry. 4th ed. Mosby: St. Louis, MO; 2002:13-61.
3. Strassler HE, Drisko CL, Alexander DC. Dentin hypersensitivity: its inter-relationship to gingival recession and acid erosion. Inside Dentistry. 2008;29(5 Special Issue):3-4.
4. Imfeld T. Dental erosion. Definition, classification and links. Eur J Oral Sci. 1996;104(2 (Pt 2)):151-155.
5. Dentin hypersensitivity: current state of the art and science. In: Pashley DH, Tay FR, Haywood VB, et al. Dentin Hypersensitivity: Consensus-Based Recommendations for the Diagnosis and Management of Dentin Hypersensitivity. Inside Dentistry. 2008;4(9 Special Issue):8-18.
6. Dorland’s Medical Dictionary. 29th Ed. Philadelphia, PA: W. B. Saunders Company; 2000.
7. Robertson TM, Lundeen TF. Cariology: the lesion, etiology, prevention, and control. In: Robertson TM, Heymann HO, Swift EJ Jr, eds. Sturdevant’s Art and Science of Operative Dentistry. 4th ed. Mosby: St. Louis, MO; 2002:63-132.
8. Tooth Erosion in Children—US Perspective. Inside Dentistry. 2009;5(3 Suppl):8.
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