Commonly known as a dental cyst, the periapical cyst is the most common
odontogenic cyst Odontogenic cyst are a group of jaw cysts that are formed from tissues involved in odontogenesis (tooth development). Odontogenic cysts are closed sacs, and have a distinct membrane derived from rests of odontogenic epithelium. It may contain air, ...
. It may develop rapidly from a
periapical granuloma
Periapical granuloma, also sometimes referred to as a radicular granuloma or apical granuloma, is an inflammation at the tip of a dead (nonvital) tooth. It is a lesion or mass that typically starts out as an epithelial lined cyst, and undergoes a ...
, as a consequence of untreated chronic
periapical periodontitis
Periapical periodontitis or apical periodontitis (AP) is an acute or chronic inflammatory lesion around the apex of a tooth root, most commonly caused by bacterial invasion of the pulp of the tooth. It is a likely outcome of untreated dental ca ...
.
Periapical is defined as "the tissues surrounding the
apex
The apex is the highest point of something. The word may also refer to:
Arts and media Fictional entities
* Apex (comics), a teenaged super villainess in the Marvel Universe
* Ape-X, a super-intelligent ape in the Squadron Supreme universe
*Apex ...
of the root of a
tooth
A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
" and a
cyst
A cyst is a closed sac, having a distinct envelope and cell division, division compared with the nearby Biological tissue, tissue. Hence, it is a cluster of Cell (biology), cells that have grouped together to form a sac (like the manner in which ...
is "a pathological cavity lined by
epithelium
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...
, having fluid or gaseous content that is not created by the accumulation of pus."
Most frequently located in the maxillary anterior region, the cyst is caused by
pulpal necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
secondary to
dental caries
Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...
or
trauma
Trauma most often refers to:
*Major trauma, in physical medicine, severe physical injury caused by an external source
*Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event
*Traumatic inju ...
. Its lining is derived from the
epithelial cell rests of Malassez
In dentistry, the epithelial cell rests of Malassez (ERM) or epithelial rests of Malassez (''pax epithelialis pediodontii'') are part of the periodontal ligament cells around a tooth. They are discrete clusters of residual cells from Hertwig's ep ...
which proliferate to form the cyst.
Such cysts are very common. Although initially asymptomatic, they are clinically significant because secondary
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
can cause
pain
Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...
and damage. In
radiograph
Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
s, the cyst appears as a radiolucency (dark area) around the apex of a tooth's root.
Signs and symptoms
Periapical cysts begin as asymptomatic and progress slowly. Subsequent infection of the cyst causes swelling and pain. Initially, the cyst swells to a round hard protrusion, but later on the body resorbs some of the cyst wall, leaving a softer accumulation of fluid underneath the mucous membrane.
Secondary symptoms of periapical cysts include inflammation and infection of the
pulp
Pulp may refer to:
* Pulp (fruit), the inner flesh of fruit
Engineering
* Dissolving pulp, highly purified cellulose used in fibre and film manufacture
* Pulp (paper), the fibrous material used to make paper
* Molded pulp, a packaging material
* ...
causing dental caries. This infection is what causes
necrosis of the pulp.
Larger cysts may cause bone expansion or displace roots. Discoloration of the affected tooth may also occur. Patient will present negative results to electric and ice test of the affected tooth but will be sensitive to percussion. Surrounding gingival tissue may experience
lymphadenopathy
Lymphadenopathy or adenopathy is a disease of the lymph nodes, in which they are abnormal in size or consistency. Lymphadenopathy of an inflammatory type (the most common type) is lymphadenitis, producing swollen or enlarged lymph nodes. In cli ...
. The
alveolar plate may exhibit
crepitus
Crepitus is "a grating sound or sensation produced by friction between bone and cartilage or the fractured parts of a bone".
Various types of crepitus that can be heard in joint pathologies are:
*Bone crepitus: This can be heard when two fragme ...
when palpated.
Complications
Expansion of the cyst causes erosion of the floor of the maxillary sinus. As soon as it enters the maxillary
antrum ''This is a disambiguation page for the biological term. For the 2018 horror movie, see Antrum (film)''
In biology, antrum is a general term for a cavity or chamber, which may have specific meaning in reference to certain organs or sites in the bod ...
, the expansion rate increases due to available space for expansion. Performing a percussion test by tapping the affected teeth will cause shooting pain. This is often clinically diagnostic of pulpal infection.
Causes
Dental cysts are usually caused due to root infection involving
tooth decay
Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...
. Untreated dental
caries
Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...
then allow bacteria to reach the level of the pulp, causing infection. The bacteria gains access to the periapical region of the tooth through deeper infection of the pulp, traveling through the roots. The resulting pulpal
necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
causes proliferation of epithelial rests of Malassez which release toxins at the apex of the tooth. The body's inflammatory response will attack the source of the toxins, leading to periapical inflammation. The many cells and proteins that rush to an area of infection create osmotic tension in the periapex which is the source of internal pressure increase at the cyst site.
These lesions can grow large because they apply pressure over the bone, causing
resorption
Resorption is the absorption of cells or tissue into the circulatory system, usually by osteoclasts.
Types of resorption include:
* Bone resorption
* Herniated Disc Resorption
* Tooth resorption
* Fetal resorption
* Blood resorption
See also
...
. The toxins released by the breakdown of granulation tissue are one of the common causes of bone resorption.
There are two schools of thought regarding cyst expansion.
# Complementary response to inflammation
# Chemical reaction with Interleukin and Prostaglandin
Mechanisms
Periapical cysts develop due to an inflammatory stimulus in 3 stages:
# Initial stage: Epithelial cells from the rests of Malassez at the apex of the roots of a non-vital tooth (one where the nerve and blood supply in the tooth have degenerated and no longer exist) become stimulated due to the body's inflammatory response to bacterial endotoxins infecting the pulp or as a direct response to necrotic pulp tissue, therefore re-entering the growth phase. Bacterial byproducts then are able to seep into the periapical region through the infected pulp.
# Cyst development stage: Epithelial cells form strands and are attracted to the area which contains exposed connective tissue and foreign substances. Several strands from each rest converge and surround the abscess or foreign body.
# Cyst growth stage: Fluid flows into the cavity where the forming cyst is growing due to the increased osmolality of the cavity in relation to surrounding serum in capillaries. Pressure and size increase.
The definitive mechanism by which cysts grow is under debate; several theories exist.
Biomechanical theory
Pressure and concentration differences between the cystic cavity and the growth surroundings influence fluid movement into the cyst, causing size increase.
Biochemical theories
a.
Collagenase
Collagenases are enzymes that break the peptide bonds in collagen. They assist in destroying extracellular structures in the pathogenesis of bacteria such as ''Clostridium''. They are considered a virulence factor, facilitating the spread of ga ...
(breakdown of collagen) in the jaw bone leads to bone degeneration, providing room for cysts to develop. Substances released by the body's immune system as a result of the connective tissue breakdown, such as
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
s and growth factors, contribute to the mobilization and proliferation of epithelial cells in the area.
b. Bone resorption caused by metabolism of acidic substances produced by cysts contributes to cyst growth. Such substances include
Prostaglandin-2 and
Interleukin-1
The Interleukin-1 family (IL-1 family) is a group of 11 cytokines that plays a central role in the regulation of immune and inflammatory responses to infections or sterile insults.
Discovery
Discovery of these cytokines began with studies on t ...
which are both produced by the cyst itself.
Nutritional deficiency theory
Epithelial cells will form a mass inside the cavity and the innermost cells become deprived of nutrients because they are far from the source of nutrients (the blood vessels). The innermost cells die and form an aggregate of dead tissue. The inner cells undergo ischemic liquefactive necrosis which creates the cavity space surrounded by growing epithelial cells. This theory is unlikely in the absence of malignant transformation of epithelial cells as it does not follow the existing relationship between connective tissue and epithelium.
Abscess theory
Epithelial cells have an inherent quality to reproduce and cover any connective tissue that is not already lined with epithelia. Formation of an abscess must precede the epithelial proliferation in order for the cells to carry out this tendency. This theory explains why cysts are lined in epithelia but not why the initial cysts itself forms.
Diagnosis
A non-vital tooth is necessary for the diagnosis of a periapical cyst, meaning the nerve has been removed by root canal therapy.
Oral examination
The surrounding intraoral anatomical structures should be palpated to identify the presence of bone expansion or displacement of tooth roots as well as
crepitus
Crepitus is "a grating sound or sensation produced by friction between bone and cartilage or the fractured parts of a bone".
Various types of crepitus that can be heard in joint pathologies are:
*Bone crepitus: This can be heard when two fragme ...
noises during examination, indicating extensive bone damage. Bulging of the buccal or lingual cortical plates may be present. Age of occurrence in the patient, the location of the cyst, the edges of cystic contours, and the impact that the cyst has on adjacent structures must all be considered for proper diagnosis.
Radiology
Several lesions can appear similarly in radiographic appearance.
Intraoral X-rays or a 3-D cone beam scan of the affected area can be used to obtain radiological images and confirm diagnosis of cysts in the periapical area. Circular or ovoid radiolucency surrounding the root tip of approximately 1-1.5 cm in diameter is indicative of the presence of a periapical cyst.
The border of the cyst is seen as a narrow opaque margin contiguous with the
lamina dura
Lamina dura is compact bone that lies adjacent to the periodontal ligament, in the tooth socket. The lamina dura surrounds the tooth socket and provides the attachment surface with which the Sharpey's fibers of the periodontal ligament perforate. O ...
. In cysts that are actively enlarging, peripheral areas of the margin may not be present. Periapical cysts have a characteristic
unilocular
A locule (plural locules) or loculus (plural loculi) (meaning "little place" in Latin) is a small cavity or compartment within an organ or part of an organism (animal, plant, or fungus).
In angiosperms (flowering plants), the term ''locule'' usu ...
shape on radiographs. There is also a severe border of cortication between the cyst and surrounding bone. Pseudocysts, on the other hand, have a fluid filled cavity but are not lined by epithelium, therefore they have a less severe and more blurred border between the fluid and bony surroundings.
Histopathology
![Histopathology of cholesterol clefts of a periapical cyst of the jaw](https://upload.wikimedia.org/wikipedia/commons/2/2d/Histopathology_of_cholesterol_clefts_of_a_periapical_cyst_of_the_jaw.jpg)
In
light microscopy
Microscopy is the technical field of using microscopes to view objects and areas of objects that cannot be seen with the naked eye (objects that are not within the resolution range of the normal eye). There are three well-known branches of micr ...
, periapical cysts show:
[ Topic Completed: 1 March 2014. Revised: 13 December 2019]
*
Stratified squamous epithelium
A stratified squamous epithelium consists of squamous (flattened) epithelial cells arranged in layers upon a basal membrane. Only one layer is in contact with the basement membrane; the other layers adhere to one another to maintain structural i ...
of variable thickness, except when originating in a
maxillary sinus
The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinuses, and drains into the middle meatus of the nose through the osteomeatal complex.Human Anatomy, Jacobs, Elsevier, 2008, page 209-210
Structure
It is ...
where there is respiratory epithelium (pseudostratified ciliated columnar epithelium).
*A fibrous capsule of varying thickness, with chronic inflammatory cells, wherein a plasma cells may be abundant
They sometimes have the following features:
[
*''Rushton hyaline bodies'', which are amorphic, eosinophilic, linear to crescent-shaped bodies in the cyst epithelium, present in 10% of periapical cysts.
*Scattered ciliated cells
*Cholesterol clefts in the cyst lining.
]
Classification
Periapical cysts exist in two structurally distinct classes:
# Periapical true cysts - cysts containing cavities entirely surrounded in epithelial lining. Resolution of this type of cyst requires surgical treatment such as a cystectomy.
# Periapical pocket cysts - epithelium lined cavities that have an opening to the root canal of the affected tooth. Resolution may occur after traditional root canal therapy.
Differentiation
Radiographically
Radiology ( ) is the medical discipline that uses medical imaging to diagnose diseases and guide their treatment, within the bodies of humans and other animals. It began with radiography (which is why its name has a root referring to radiatio ...
, it is virtually impossible to differentiate granuloma
A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...
from a cyst. If the lesion is large it is more likely to be a cyst. Radiographically, both granulomas and cysts appear radiolucent. Many lesions of the mandible in particular appear cystlike in appearance. It is often necessary to obtain a biopsy and evaluate the tissue under a microscope to accurately identify the lesion.
Treatment
The infected tissue of the periapical cyst must be entirely removed, including the epithelium of the cyst wall; otherwise, a relapse is likely to occur. Root canal treatment should be performed on the tooth if it is determined that previous therapy was unsuccessful. Removal of the necrotic pulp and the inflamed tissue as well as proper sealing of the canals and an appropriately fitting crown will allow the tooth to heal under uninfected conditions.
Surgical options for previously treated teeth that would not benefit from root canal therapy include cystectomy and cystostomy. This route of treatment is recommended upon discovery of the cyst after inadequate root canal treatment. A cystectomy is the removal of a cyst followed by mucosa and wound closure to reduce chances of cyst regeneration. This type of treatment is more ideal for small cysts.
A cystostomy is recommended for larger cysts that compromise important adjacent anatomy. The cyst is tamponaded to allow for the cyst contents to escape the bone. Over time, the cyst decreases in size and bone regenerates in the cavity space.
Marsupialization
400px, Marsupialization
Marsupialization is the surgical technique of cutting a slit into an abscess or cyst and suturing the edges of the slit to form a continuous surface from the exterior surface to the interior surface of the cyst or abscess. ...
could also be performed, which involves suturing the edges of the gingiva surrounding the cyst to remain open. The cyst then drains its contents and heal without being prematurely closed. The end result is the same as the cystostomy, bone regeneration. For both a cystostomy and marsupialization, root resectioning may also be required in cases where root resorption has occurred.
Epidemiology
Periapical cysts comprise approximately 75% of the types of cysts found in the oral region. The ratio of individuals diagnosed with periapical cysts is 3:2 male to female, as well as individuals between 20 and 60 years old. Periapical cysts occur worldwide.
Types of Periapical cysts:
Apical: 70%
Lateral: 20%
Residual: 10%
References
External links
{{DEFAULTSORT:Periapical Cyst
Gross pathology
Oral and maxillofacial surgery
Diseases of oral cavity, salivary glands and jaws