Striae of Retzius
Encyclopedia
The striae of Retzius are incremental growth lines or bands seen in tooth enamel
and are the result of disrupted enamel development.
.
Produced during the second stage of enamel calcification, also known as the maturation stage, ameloblast
s produce matrix and enamel at the rate of 4 micrometers per day; however every fourth day there is a change in development. Brownish lines, the striae of Retzius, develop as a result of a change in the growth process. Macroscopically, these lines can be seen on the labial
surface or lip side of anterior or front teeth as horizontal lines on the tooth crown
, also known as "imbrication lines".
can cause some lines to appear darker than those surrounding them. The neonatal line
is the darkest band, which represents the disrupted enamel formation due to the stress of being born.
The formation of the striae of Retzius results from a constriction of Tomes' process
es when the activity of ameloblast
s – cells only present in laying down enamel – is narrowed in conjunction with an increasing process of interrod enamel
development.
on their website:
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...
and are the result of disrupted enamel development.
Appearance
When viewed microscopically in cross-section, they appear as concentric rings. In a longitudinal section, they appear as a series of dark bands. The presence of the dark lines is similar to the annual rings on a tree. They are named after Swedish anatomist Anders RetziusAnders Retzius
Anders Retzius , was a Swedish professor of anatomy and a supervisor at the Karolinska Institute in Stockholm....
.
Produced during the second stage of enamel calcification, also known as the maturation stage, 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 produce matrix and enamel at the rate of 4 micrometers per day; however every fourth day there is a change in development. Brownish lines, the striae of Retzius, develop as a result of a change in the growth process. Macroscopically, these lines can be seen on the labial
Labial
Labial may refer to:*the lips*the labia *In linguistics, a labial consonant*In zoology, the labial scales...
surface or lip side of anterior or front teeth as horizontal lines on the tooth crown
Crown (tooth)
In dentistry, crown refers to the anatomical area of teeth, usually covered by enamel. The crown is usually visible in the mouth after developing below the gingiva and then erupting into place.-References:...
, also known as "imbrication lines".
Causes
Occasional darker striae or grooves of Retzius result from systemic disturbances in the human body. For example, a feverFever
Fever is a common medical sign characterized by an elevation of temperature above the normal range of due to an increase in the body temperature regulatory set-point. This increase in set-point triggers increased muscle tone and shivering.As a person's temperature increases, there is, in...
can cause some lines to appear darker than those surrounding them. The neonatal line
Neonatal line
The neonatal line is a particular band of incremental growth lines seen in histologic sections of a deciduous tooth. It belongs to a series of a growth lines in tooth enamel known as the Striae of Retzius. The neonatal line is darker and larger than the rest of the striae of Retzius...
is the darkest band, which represents the disrupted enamel formation due to the stress of being born.
The formation of the striae of Retzius results from a constriction of Tomes' process
Tomes' process
Tomes' processes are a histologic landmark identified on an ameloblast, cells involved in the production of tooth enamel. During the synthesis of enamel, the ameloblast moves away from the enamel, forming a projection surrounded by the developing enamel...
es when the activity of 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 – cells only present in laying down enamel – is narrowed in conjunction with an increasing process of interrod enamel
Interrod enamel
Interrod enamel is histologically identified on microscopic views of tooth enamel. Because interrod enamel is located around enamel rods, the areas of interrod enamel enhances the "keyhole" appearance of enamel rods by acting as its border...
development.
Qualities
Lines of Retzius (think age bands like tree growth rings) – Stria (A)- artifacts in enamel (not found in dentinDentinDentine 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...
) created by incremental steps of ameloblasts - comparable to the contour "lines of Owen" in dentin
- have increased organic content and show the variations in rhythm as the tooth enamel matrix calcifies
- follow an appositional or side-by-side growth pattern
Illustrations
Several diagrams and photographs of these lines (and others) appears in a document published by the Max Planck Institute for Evolutionary AnthropologyMax Planck Institute for Evolutionary Anthropology
The Max Planck Institute for Evolutionary Anthropology is a research institute based in Leipzig, Germany, founded in 1997. It is part of the Max Planck Society network....
on their website: