Enamel spindles are "short, linear defects, found at the dentinoenamel junction (DEJ) and extend into the enamel

Tooth enamel

Tooth enamel, along with dentin, cementum, and dental pulp is one of the four major tissues that make up the tooth in vertebrates. It is the hardest and most highly mineralized substance in the human body. Tooth enamel is also found in the dermal denticles of sharks...

, often being more prevalent at the cusp

Cusp (dentistry)

A cusp is an occlusal or incisal eminence on a tooth.Canine teeth, otherwise known as cuspids, each possess a single cusp, while premolars, otherwise known as bicuspids, possess two each. Molars normally possess either four or five cusps...

 tips." The DEJ is the interface

Interface (chemistry)

An interface is a surface forming a common boundary among two different phases, such as an insoluble solid and a liquid, two immiscible liquids or a liquid and an insoluble gas. The importance of the interface depends on which type of system is being treated: the bigger the quotient area/volume,...

 of the enamel and the underlying dentin

Dentin

Dentine is a calcified tissue of the body, and along with enamel, cementum, and pulp is one of the four major components of teeth. Usually, it is covered by enamel on the crown and cementum on the root and surrounds the entire pulp...

. Because they are "formed by entrapment of odontoblast

Odontoblast

In vertebrates, an odontoblast is a biological cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the creation of dentin, the substance under the tooth enamel....

 processes between ameloblast

Ameloblast

Ameloblasts are cells, present only during tooth development, that deposit tooth enamel, the hard outermost layer of the tooth that forms the chewing surface....

s prior to and during amelogenesis

Amelogenesis

Amelogenesis is the formation of enamel on teeth and occurs during the crown stage of tooth development after dentinogenesis, which is the formation of dentine. Although dentine must be present for enamel to be formed, it is also true that ameloblasts must be present in order for dentinogenesis to...

," they cannot be found at the enamel surface protruding inward, as enamel lamellae

Enamel lamellae

Enamel lamellae are a type of hypomineralized structure in teeth that extend either from the dentinoenamel junction to the surface of the enamel, or vice versa. In essence, they are prominent linear enamel defects, but are of no clinical consequence...

 are often located.

Enamel spindles are often confused with two other entities: enamel lamellae

Enamel lamellae

Enamel lamellae are a type of hypomineralized structure in teeth that extend either from the dentinoenamel junction to the surface of the enamel, or vice versa. In essence, they are prominent linear enamel defects, but are of no clinical consequence...

 and enamel tufts

Enamel tufts

Enamel tufts are hypomineralized ribbon-like structures that run longitudinally to the tooth axis and extend from the dentinoenamel junction one fifth to a third into the enamel...

. Lamellae are linear enamel defects that extend from the surface of the enamel towards the DEJ, or vice versa. Enamel tufts are "small, branching defects that are found only at the DEJ, protruding into the enamel towards the enamel surface. Enamel spindles however, are in fact odontoblast processes that extend into the enamel.