This is one in a series of articles that provide detailed and updated information about Dentin.
In this specific article, which focuses on Dentin – Overview, you can read about:
For additional articles about Dentin, see the Topic Menu.
What is dentin?
Dentin is a mineralized connective tissue that makes up the inner part of the tooth, enclosing the pulp. It is covered by enamel in the crown portion and cementum in the root. Composed of 45%-50% inorganic or mineralized material, 30% organic material, and 25% water, mature dentin is a crystalline substance.
The primary component of mature dentin’s crystalline structure is calcium hydroxyapatite (Ca10(PO4)6(OH)2), which can also be found in enamel, cementum, and bone. However, the quantity of calcium hydroxyapatite crystals varies among these tissues. Enamel contains a higher percentage of these crystals, while both cementum and bone tissue have lower percentages compared to dentin. As a result, mature dentin is less hard than enamel, but slightly harder than bone.
Additionally, the crystals in dentin are plate-like in shape and 30% smaller than those found in enamel. Dentin also contains small amounts of other minerals, such as carbonate and fluoride.
Dentin Function
Dentin is an important component of the tooth, performing several important functions such as:
- Forming the bulk of the tooth in both the crown and root.
- Giving color to the tooth; due to the translucency of the overlying enamel, the coronal dentin provides color for the enamel. Dentin has a yellow hue, which is a deeper tone in permanent teeth. In cases of pulp infection or dead pulp, discoloration of the dentin causes a darkening of the crown.
- Providing elasticity to the tooth due to its high tensile strength.
- Absorbing and transmitting high pressure and forces from the hard enamel layer, preventing fractures. Tooth strength and rigidity are provided by the intact dentinal substrate. During cavity preparation, a conservative approach should be followed; if large preparations are required, the dentist should consider the placement of an onlay or crown.
- Protecting the pulp by forming a hard layer over it.
- Responding to thermal, chemical, or tactile external stimuli as an avascular vital tissue.
What is the role of dentin in teeth?
Dentin forms the bulk of the tooth structure and is a major part of mineralized dental tissues. It is the middle layer of the tooth, present between enamel and pulp in the crown portion and between cementum and pulp in the root portion.
Dentin plays several critical roles in teeth, including:
- Providing foundation and support for the enamel layer to rest upon. Without dentin, the enamel layer would be unsupported and more susceptible to fractures.
- Forming a protective covering around the pulp, which contains the tooth’s nerves and blood vessels. It acts as a barrier, shielding the sensitive pulp from external stimuli and helping to prevent infection.
- Containing tiny tubules that run from the outer surface of the tooth to the pulp cavity, facilitating the transmission of sensations such as hot and cold temperatures.
In summary, dentin is a vital component of teeth, offering structural support, protection, and transmission of senses.
Dentin composition – what is dentin made of?
Dentin is a complex and highly specialized tissue, composed of a delicate balance of mineral and organic materials that work together to provide teeth with the strength and flexibility they need to function properly. Dentin also contains water, which makes up a small percentage of its overall composition.
The composition of dentin can be described as follows:
- Organic matrix – Accounting for almost 35% of dentin composition, the organic matrix can be divided into collagenous and non-collagenous components. The collagenous part is largely made of Type I collagen, which harbors hydroxyapatite mineral crystals. Compared to enamel, dentin has more organic content but less mineral. In addition to Type I collagen, small amounts of Type III and Type V collagen are present. Non-collagenous components include phosphorylated and non-phosphorylated proteins, proteoglycans, lipids, growth factors, and enzymes.
- Mineral content – Making up almost 50% of dentin composition, this part is primarily composed of hydroxyapatite, which gives dentin its hardness and density. This is the crystalline form of calcium phosphate. The hydroxyapatite crystals are plate-shaped but smaller than those in enamel. Dentin also contains small amounts of phosphates, carbonates, sulfates, and some collagen and other proteins. These organic materials provide flexibility and toughness to dentin, allowing it to withstand the stresses of biting and chewing.
- Water- Accounting for the remaining 15-20% of dentin composition..
Summary of Dentin Composition:
| Component | By Weight | By Volume |
|---|---|---|
| Mineral content | 68–70% | 50% |
| Organic content | 21% | 35% |
| Water | 11% | 15% |
Dentin or Dentine?
Dentin is a layer of hard tissue present below the enamel and covering the pulp of the tooth. It can be termed as “Dentin” when used in American English format or “Dentine” when used in British English format. Both terms hold the same definition.
How hard is dentin?
Dentin is a hard tissue, present as the middle layer in the tooth between enamel and pulp. Its complex composition of mineral and organic matrix makes it hard enough to protect the sensitive pulp from external stimuli and flexible to withstand the stresses of biting and chewing
On the Mohs scale, dentin has a hardness of around 2.5-3.5. The Mohs scale is used to measure the hardness of minerals, ranging from 1 to 10, with 1 being the softest (e.g., talc) and 10 being the hardest (e.g., diamond). Enamel, the hardest tissue in the human body, has a hardness of around 5..
How long does dentin last?
Dentin is a hard tissue that protects the pulp and can last for a lifetime, continuing to perform its function. However, the lifespan of dentin can be affected by several factors, including:
- Improper oral hygiene: If teeth are not cleaned properly, debris allows bacterial growth, which can penetrate the enamel layer and reach the dentin, resulting in tooth decay. Severe decay may require a filling or crown to restore the tooth’s function and strength.
- Improper brushing technique: This can lead to tooth abrasion, resulting in dentin loss and dentinal hypersensitivity.
- Dentin loss: Over time, dentin can become worn down by the stresses of biting, chewing, or parafunctional habits such as clenching. This can result in tooth structure cracks or fractures, leading to teeth sensitivity and other dental problems.
- Improper eating and drinking habits: Sugary and acidic foods and drinks can affect dentin by causing loss of surface structure.
- Periodontal diseases: If decay reaches the root due to gum disease, it can easily penetrate the dentin, causing dentin loss.
Why is dentin considered a vital tissue?
Dentin is considered a vital tissue for several reasons, which are primarily related to its structural, protective, and sensory functions within the tooth. As a critical component of the tooth’s anatomy, dentin plays an essential role in maintaining the tooth’s overall health and functionality.
Here are some vital functions of Dentin:
- Structural support: Dentin provides essential support to the tooth by forming the bulk of its structure. It is located beneath the enamel and above the pulp, acting as a foundation for the enamel and a protective barrier for the pulp.
- Elasticity and flexibility: Due to its high tensile strength, dentin grants the tooth elasticity and flexibility, allowing it to withstand the stresses of biting and chewing without breaking or fracturing.
- Protection of the pulp: Dentin forms a hard layer around the tooth’s pulp, which contains nerves and blood vessels. By enclosing the pulp, dentin shields these sensitive structures from external stimuli and potential infections.
- Responsiveness to stimuli: Dentin is considered a vital tissue because it contains cytoplasmic processes of odontoblasts (the cells that produce dentin) and nerve endings that can sense hot and cold temperatures. This responsiveness to external stimuli is a crucial aspect of the tooth’s sensory function.
- Continuous formation: Dentinogenesis, the process of dentin formation, occurs throughout life after teeth have erupted and have been functioning for a short time. This ongoing process helps maintain the tooth’s structural integrity and vitality.
- Repair and regeneration: In response to pathological effects such as dental caries, abrasion, attrition, or operative procedures, dentin can undergo changes, including the development of dead tracts, sclerosis, and the addition of reparative dentin. These changes demonstrate dentin’s capacity to repair and regenerate itself in the face of damage.
- Connection to the pulp: The pulp, which is rich in blood and nerve supply, as well as immunological and regenerative properties, maintains dentin’s vitality. This close connection between dentin and the pulp further highlights the tissue’s essential role in the overall health of the tooth.
Dentin vs. Enamel
Dentin and enamel are two different types of hard tissues found in the teeth. While both are hard, mineralized tissues, they have several differences:
- Color: Dentin is typically yellow-white and slightly darker than enamel.
- Reflectance: Dentin is less reflective to light than enamel surfaces, which appear shiny. Dentin is more opaque and duller in comparison to enamel.
- Hardness: Dentin is softer than enamel; on the Mohs scale, the hardness of dentin is 3, while enamel is 5.
- Location: Enamel forms the outermost layer of the tooth, while Dentin is located beneath the enamel layer and above the pulp.
- Composition: Dentin consists of hydroxyapatite, collagen, and other organic materials. In contrast, enamel is primarily composed of hydroxyapatite.
- Function: Dentin provides structural support to the tooth, protects the pulp, and transmits sensations. Enamel, on the other hand, servers as a protective layer for the underlying dentin and pulp, helping to withstand the stresses of biting and chewing, and resists wear and tear.
Dentin vs. Cementum
Dentin and cementum are two distinct types of hard tissues found in teeth. While they share some similarities, they also have notable differences:
- Location: Dentin is situated beneath the enamel layer and above the pulp. Cementum, on the other hand, is located on the outer surface of the tooth root, covering the dentin layer.
- Composition: Dentin is primarily composed of hydroxyapatite, a crystalline form of calcium phosphate, and organic materials such as collagen and other proteins. Cementum is composed of mineralized tissue like hydroxyapatite, as well as organic materials such as collagen.
- Function: Dentin provides structural support to the tooth, protects the pulp cavity, and transmits sensations like hot and cold temperatures. Cementum, in contrast, helps anchor the tooth to the jawbone and provides a surface for the periodontal ligament to attach to.
Dentin vs. Bone
Dentin and bone are two distinct types of hard tissues found in the body. While they share some similarities, they also have several key differences:
- Location: Dentin is found exclusively in the teeth, specifically in the crown and root. Bone is located throughout the body, including the jaws, face, and skull, making up the skeletal system.
- Composition: Dentin is primarily composed of hydroxyapatite, a mineral form of calcium phosphate, along with collagen and other organic materials. Bone is also composed of hydroxyapatite and collagen fibers, but it has a different organization of these components, with a mineralized matrix forming the bulk of its structure.
- Function: Dentin provides structural support to the tooth, protects the pulp cavity, and transmits sensations such as hot and cold temperatures. Bone, on the other hand, provides support and structure to the body, protects internal organs, produces blood cells, and stores minerals such as calcium.
- Structure: Dentin has a tubular structure, with microscopic channels known as dentinal tubules running from the pulp cavity to the outer surface of the dentin. These tubules contain the cytoplasmic processes of odontoblasts and nerve endings. Bone has a more complex structure, with two main types: compact bone, which is dense and forms the outer layer of bones, and spongy bone (also called trabecular or cancellous bone), which has a honeycomb-like structure and is found mainly at the ends of long bones and in the interior of other bones.
Dentin vs. Pulp
Dentin and pulp are two distinct types of tissues found in teeth, and they differ in many aspects:
- Location: Dentin is situated beneath the enamel layer in the crown of the tooth and constitutes the majority of the tooth structure. It also encloses the pulp cavity. Pulp, on the other hand, is located at the core of the tooth, surrounded by dentin.
- Composition: Dentin is primarily composed of hydroxyapatite, a mineral form of calcium phosphate, along with collagen and other organic materials. In contrast, pulp consists of connective tissue, blood vessels, nerves, and other specialized cells.
- Function: Dentin provides structural support to the tooth, safeguards the pulp cavity, and transmits sensations such as hot and cold temperatures. Pulp nourishes the tooth and delivers sensation, enabling the detection of hot and cold temperatures, pressure, and pain.
- Tooth development: Dentin is formed by odontoblasts, specialized cells that produce the dentin matrix. During tooth development, odontoblasts differentiate from dental papilla cells and secrete the dentin matrix. In contrast, pulp originates directly from the dental papilla, which is a collection of cells that later develops into the pulp chamber, containing blood vessels, nerves, and connective tissue.
- Regenerative abilities: Dentin has a limited ability to regenerate after being damaged, such as through dental caries or trauma. The odontoblasts may produce reparative dentin, a new layer of dentin to protect the pulp. However, this reparative process is relatively slow and limited in scope. Pulp, on the other hand, possesses greater regenerative potential due to the presence of stem cells, blood vessels, and growth factors. In some cases, dental pulp can regenerate and heal itself after mild injury or inflammation.
- Response to stimuli: Dentin is a relatively insensitive tissue and primarily transmits sensations of hot, cold, and pressure to the pulp. The pulp is more sensitive to various stimuli, as it contains nerve fibers and is responsible for the tooth’s pain response. When the pulp is exposed or irritated, it can cause intense pain, while dentin exposure typically results in milder sensations such as sensitivity to hot, cold, or sweet substances.
Dentin Collagen
Collagen, a protein found throughout the body, is a major component of various types of connective tissues, such as bone, cartilage, and skin. Dentin collagen, specifically, is a type of collagen found in dentin, constituting approximately 90% of the organic matrix and providing dentin with its unique mechanical properties. In dentin, collagen fibers are arranged in a highly organized pattern, with most of the collagen being type I collagen, and about 3% comprising type III and/or type V collagens.
Specifically, type I collagen is formed through the self-assembly of two alpha1 and one alpha2 chains, which come together to create a triple helix structure featuring a coiled-coil conformation (interwoven helices). This arrangement results in a supercoil that imparts strength and resilience to dentin.
Dentin layer
Dentin is a hard tissue layer found in teeth, located beneath the enamel in the crown and beneath the cementum in the root. It is yellowish in color and has a softer, more porous structure than enamel.
The Dentin layer is the second hardest tissue in the tooth, harder than bone but not as hard as enamel. It consists of a collagen-rich organic matrix which provide dentin with elasticity and strength, and contains hydroxyapatite crystals, providing dentin its hardness.
The Dentin layer is traversed by tiny channels called dentinal tubules that run from the pulp chamber in the tooth’s core to the dentin layer’s outer surface. These tubules house processes of odontoblasts, specialized cells that produce dentin and transmit sensory information from the tooth surface to the nerve endings in the pulp. Dentin thickness varies depending on the tooth’s location and age, with dentin becoming thicker as the tooth ages.
Dentin matrix
The dentin matrix, the organic component of dentin, comprises about 20-30% of the total dentin volume. It is a complex structure composed of collagenous and non-collagenous proteins, playing a critical role in the tooth’s function, including supporting enamel, transmitting sensory information, and protecting the pulp from damage.
Collagen fibers in the dentin matrix are arranged in a tubular pattern, forming microscopic channels called dentinal tubules that run from the pulp chamber to the dentin layer’s outer surface. These tubules house processes of odontoblasts, specialized cells that produce dentin, and transmit sensory information from the tooth surface to the nerve endings in the pulp.
In addition to collagen, the dentin matrix contains proteoglycans, large molecules composed of a core protein and long chains of carbohydrate molecules called glycosaminoglycans. Proteoglycans in the dentin matrix play a key role in regulating dentin formation and mineralization while providing the tooth with elasticity and strength.
Non-collagenous proteins, including growth factors, enzymes, and other specialized proteins involved in dentin formation and repair, are also present in the dentin matrix.
The dentin matrix is the organic component of dentin, and it makes up about 20-30% of the total dentin volume. The dentin matrix is a complex structure composed of collagenous and non-collagenous proteins. The dentin matrix is an important component of the tooth structure, and its composition and organization play a critical role in the function of the tooth, including supporting the enamel, transmitting sensory information, and protecting the pulp from damage.
Dentin-Pulp Complex
The dentin-pulp complex refers to the functional unit of the tooth where dentin and pulp intersect. This complex is responsible for the tooth’s sensory function, including detecting changes in temperature, pressure, and other stimuli.
Dental pulp, located at the center of the tooth, is a soft vital tissue containing blood vessels, nerves, and connective tissue that nourish and support the tooth, as well as specialized cells called odontoblasts that produce new dentin. Dentin, a hard vital tissue, surrounds the pulp.
The dentin-pulp complex plays a crucial role in protecting dental pulp from damage. The dentin layer acts as a barrier to external stimuli and provides structural support to the tooth. Dentinal tubules running through the dentin layer transmit sensory information from the tooth surface to the nerve endings in the dental pulp, which then send signals to the brain.
Maintaining the health of the dentin-pulp complex is essential for the long-term function and survival of the tooth. Damage to the complex may result in pain, inflammation, and other symptoms.
Dentin Quality
Dentin quality refers to the physical and mechanical properties of dentin that contribute to its strength, durability, and fracture resistance. Various factors influence dentin quality, including collagen fiber composition and organization, hydroxyapatite crystal mineralization levels, and dentin layer thickness and density.
High-quality dentin typically has a higher degree of mineralization and a more organized collagen fiber structure. These characteristics lead to increased stiffness, strength, and resistance to deformation under load, essential properties for the tooth’s long-term function and survival. In contrast, low-quality dentin, often found in older teeth or those affected by certain dental conditions, may have lower mineralization levels, disorganized collagen fibers, and a weaker overall structure, making the tooth more susceptible to damage, fracture, and other forms of mechanical failure.
Dentin quality can also be affected by various dental procedures, such as cavity preparation, bonding, and root canal therapy. These procedures can alter dentin’s structure and composition, impacting its mechanical properties and overall quality.
Assessing dentin quality is an important consideration in restorative and preventive dentistry, as it can influence the choice of materials and techniques used to treat dental conditions and restore tooth function.
