Dentinal hypersensitivity and desensitization

Histological zones of pulp

1. Odontoblastic zone

2. Cell-free zone of Weil

3. Cell-rich zone

4. Pulp core

Outer layers of dentine

• atubular or has tubules that are bent in loops

• less mineralized

• mantle dentine in crown

• Tomes granule layer and hyalin Hopewell-Smith’s layer in root

Primary dentine

forms during initial tooth development

• has organized tubules

Secondary dentine

forms after completion of tooth development

• less structured than primary

• slowly reduces pulp cavity size in tooth

Reactionary dentine

produced in response to pathological event

• less structured than primary or secondary dentine

• shields and protects pulp from noxious stimuli

Sclerotic dentine

forms to cover dentinal tubules

Label the basic layers of dentine

Dentinogenesis

Odontoblasts secrete predentine made of:

• type I collagen

• Non-collagen ECM molecules

Dynamic properties of dentine

Dentine goes from opaque to translucent with age

• increase mineralization and loss of organic matter makes dentine more glassy

Increase in sclerotic dentine with age

• covering of dentine tubules

• increase mineralization of peritubular dentine

Decrease mechanical properties of dentine

• increase risk of fracture

• potential decreased hypersensitivity

What are common triggers of dentinal hypersensitivity

• cold/heat

• acid

• sweet

• air flow

Prevalence of dentinal hypersensitivity

• 4-57%

• may affect eating, drinking, speaking, hygiene

  • can cause chronic dental pain (rare)

• common in periodontal patients and people in 30s-50s

Mechanism of dentinal hypersensitivity

1. Dentine becomes exposed (local lesion)

   • hard/soft tissue damage

2. Localized lesion has to be initiated to become hypersensitive

   • smear layer or tubular plugs are removed

   • acid erosion (prominent factor)

Dentine smear

layer of debris, saliva proteins, cementum fragments that cover dentinal tubules

• can plug openings of dentinal tubules

• can be removed by acid = increase sensitivity

Theories to describe pain transduction through dentine

1. Dentine innervation theory

2. Odontoblast transduction theory

3. Hydrodynamic theory

Dentine innervation theory

• C fibers and A fibers terminate in pulp and dentine

Odontoblast transduction theory

• odontoblasts may have mechanosensory function

• fluid movement in tubules is detected by odontoblasts — transmit signal to neurons in pulp

Hydrodynamic theory

External stimuli causes increased rate of outflow of tubular fluid from open dentine tubules

• sensory nerves in pulp are activated by fluid outflow == short, sharp pain

In-office desensitizing agents

• fluoride

• sealants

• adhesive

• laser treatment

At-home desensitizing agents

• toothpaste

• mouthwash

Mechanical/chemical desensitizing agents

Focus on blocking/covering the dentinal tubules

• salts

• fluoride

• oxalate

• arganine/calcium

• high output laser treatment

Pulpal nerve desensitizing agents

Focus on directly desensitizing pulpal nerves

• pharmacological action

• low output laser treatment

Invasive treatments for desensitization

For hypersensitivity related to abrasion/erosion

• restoration with CR or GI

• crowns/veneers

Related to periodontal disease/root exposure

• tissue regeneration

• flap surgery

• tissue grafting