Chapter 4 Periapical diseases
Teaching Outline:
I. Biological features of the periapical tissues
II. Etiology ★
1. Infection
2. Trauma
3. Chemical irritation
4. Immune factors / Immunifaction
III. Classification of periapical diseases
IV. Clinical and Pathological features ★
1. Acute periapical periodontitis :
Acute serous periapical periodontits
Acute suppurative periapical periodontitis
2. Chronic suppurative periapical periodontitis
3. Periapical granuloma
4. Radicular cyst
V. Immune-pathology of the periapical periodontitis
VI. Summery
Discussion:
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Definition:
Periapical inflammation is usually due to spread of infection following death of the pulp. It characteristically causes tenderness of the tooth in its socket. Local (periapical) periodontitis must be distinguished from chronic (marginal) periodontitis, in which infection and destruction of the supporting tissues spread from chronic infection of the gingival margins. Infection is far the most common cause. The usual sequence of events is caries, pulpitis, death of the pulp and periodontitis.
I. Biological features of the periapical tissues
1. Blood supply of the periapical tissue
The arterial vessels of the periodontal ligament are derived from three sources:
●Branches from apical vessels that supply the dental pulp.
●Branches from intra-alveolar vessels. These run horizontally, penetrating the alveolar bone to enter the periodontal ligament.
●Branches from gingival vessels. These enter the periodontal ligament from the coronal direction.
2. Nerves of periapical tissue
The nerve fibers supplying the periodontal ligament are functionally of two
types; sensory and autonomic. The sensory fibers are associated with the modalities of pressure and pain. The autonomic fibers are associated mainly with the supply of the periodontal blood vessels. Periodontal nerve fibers are both myelinated and unmyelinated.
3. The periapical ligament has the following functions:
■ It is the tissue of attachment between the tooth and alveolar bone. It is thus responsible for resisting displacing forces (the tooth support mechanism) and it protects the dental tissues from damage caused by excessive occlusal loads (especially at the root apex)
■ It is responsible for the mechanisms whereby a tooth attains, and then maintains, its functional position. This includes the mechanisms of tooth eruption, tooth support (particularly the recovery response after loading), and drift.
■ Its cells form, maintain and repair alveolar bone and cementum.
■ Its mechanoreceptors are involved in the neurological control of mastication.
★ II. Etiology
The nature and behavior of lesions that form at the apex of the tooth are a reflection of the conditions that lead to the destruction of the pulp of the associated tooth．The four major factors follow：
1．Presence of an open or closed pulpitis
2．Various kinds of the involved microorganisms
3．Extent of sclerosis of the dentinal tubules
4．Competency of the host immune response
When the factors are optimal，such as the presence of an open chronic pulpitis，bacteria of low virulence，an older tooth with sclerotic dentinal tubules，and a healthy patient，the changes at the apex of the tooth are mild and chronic．Multiple optimal factors are sometimes associated with little or no activation of the inflammatory response；instead they act as stimulants to the fibroblastic and osteoblastic cells and scar tissue and dense bone produced in the area．When conditions are mostly adverse，such as the presence of a closed acute pulpitis，large numbers of highly virulent bacteria，and open dentinal tubules of young teeth，the inflammation at the apex of the tooth will rapidly intensify and large amounts of bacterial toxins and autolytic enzymes will be produced and disseminated．Under these circumstances rapid destruction of the periapical tissue and surrounding bone takes place；the process quickly extends into the adjacent marrow spaces．
Causes of apical periodontitis
●Infection
●Trauma
●Chemical irritation
●Immune factor/ immunifaction
( I ) Infection:
1. Dental caries：Dental plaque Dental caries Pulpitis Periodontitis
2. Periodontal pocket：The necrotic pulp probably becomes infected by bacteria from the gingival margins, leading to apical periodontitis.
3. Systemic infection：（Rare）
( II ) Trauma:
1. The pulp sometimes dies from a blow which damages the apical vessels.
2. During endodontic treatment, instruments may be pushed through the apex or side of the root, damaging the periodontal membrane and carrying infected debris from the pulp chamber into the wound.
3. A high filling, or biting suddenly on a hard object, sometimes causes an acute but usually transient periodontitis.
4. Occlusal trauma and orthodontics lead to trauma：
( III ) Chemical irritation
1. Irritant antiseptics used to sterilize a root canal can escape through the apex and damage the surrounding tissues.
2. A root-canal filling may also extend beyond the apex with similar effect.
( IV) Immune factors / Immunifaction
Reference: Foreign Medical Sciences (Stomatology) 2000;27(5):278
Key points:
Periapical inflammation
Irritant Host defences
▲
nature
severity
duration
Mnemonic for differential diagnosis of pain of pulpal and periapical origin-LOCATE
● Location
● Other symptoms
● Character
●Associations
● Timing
● Evaluation of other investigations, (pulp vitality tests)
III. Classification of periapical diseases
1. Acute serous periapical periodontitis
2. Acute suppurative periapical periodontitis
3. Chronic suppurative periapical periodontitis
4. Periapical granuloma
5. Radicular cyst
6. Granulating osteitis
7. Condensing osteitis
8. Periapical scar
9. Residual cyst
10. Cholesteatoma
11. Periapical particular inflammation
12. Periapical lesions of non-pulpal origin
13. Resorption of root
★IV. Clinical and Pathological features
(I) Acute periapical periodontitis :
The factors leading to the development of acute lesions at the apex of a tooth are usually one or more of the following：
1．Young tooth with open tubules
2．Rampant caries
3．Closed acute pulpitis
4．Presence of highly virulent microorganisms
5．Weakened host defense system
Under most or all of these circumstances the ensuing inflammatory events happen quickly and cause a great deal of pain．If unchecked．infection and purulent exudate date rapidly spread throughout the affected jaw into the adjacent structures and the systemic circulation，where emboli of the infection could lodge in the small capillaries of a number of distant organs or anatomic locations．
●Clinical features:
The patient may give a history of pain due to previous pulpitis. When
periodontitis develops, escape of exudates into the periodontal membrane causes the tooth to be extruded by a minute amount and the bite to fall more heavily on it. The tooth is at first uncomfortable, then increasingly tender, even to mere touch. Hot or cold substances do not cause pain in the tooth. As inflammation becomes more severe and pus starts to form, pain becomes intense and throbbing in character. There is often a large carious cavity or filling in the affected tooth, or it may be discoloured due to death of the pulp earlier. At this stage the gingival over the root is red and tender, but there is no swelling while inflammation is confined within the bone.
●Radiographic features：
Radiographs give little information because bony changes have had too
short a time to develop. Immediately round the apex the lamina dura may appear slightly hazy and the periodontal space may be slightly widened. When acute periodontitis is due to exacerbation of a chronic infection, the original lesion can be seen as an area of radiolucency at the apex. Exudates may penetrate overlying bone and periosteum a day or so after the onset of pain, allowing relief of the pressure. Pain quickly abates but exudates, if it cannot escape, distends the soft tissues to form a swelling.
When an upper canine is affected, the swelling quickly spreads to the face
and eyelid and may close the eye on that side . In spite of the alarming appearance, the swelling is due only to oedema. It subsides when the tooth is extracted or the infection is drained. The regional lymph nodes may be enlarged and tender, but general symptoms are usually slight or absent. Inflammation typically remains localized. Further spread of infection can cause inflammation of the surrounding bone (osteomyelitis) or cellulites , but only exceedingly rarely.
●Pathological features:
Acute apical periodontitis is a typical acute inflammatory reaction with
engorged blood vessels and packing of the tissue with neutrophils. These changes are initially localized to the immediate vicinity of the apex as a consequence of the rich blood supply to this area. The immediately adjacent lamina dura becomes resorbed and an abscess cavity may form if not aborted by treatment.
(II) Periapical abscess
The periapical abscess is the initial lesion that develops when the circumstances are adverse．It is probably the most painful patient condition that confronts clinicians and is potentially one of the most dangerous．It is a progression of an acute pulpitis in which exudate extends into the adjacent soft and hard tissues．Because it often contains one or more strains of virulent bacterial organisms，the exudate usually contains potent exotoxins and lytic enzymes capable of rapidly breaking down tissue barriers．Often absent is an opening to allow drainage from the pulp through the crown to the oral cavity, relieving internal pressure within the periodontal membrane．Such internal pressure causes extrusion of the tooth from the socket and rapid extension of the exudate throughout the underlying medullary bone．
●Clinical features:
Patients with a periapical abscess are in a great deal of pain．Temperature elevation and malaise are common．In most patients the tooth associated with the abscess will extrude from the socket sufficiently to cause occlusal interference and greatly increased pain when it contacts an opposing tooth．In locations where the root apex is in close proximity to the cortex of the overlying alveolar bone, swelling and redness of the area will be present．At this stage the percussion test is most useful in establishing a diagnosis．Although the tooth is relatively insensitive or unresponsive to hot，cold，and electrical stimulation，gently tapping on it produces intense pain.
●Radiographic features：
The area around the apex of the tooth initially exhibits a slight widening of the apical periodontal space，with a gradual loss of the distinctness of the adjacent alveolar bone (lamina dura)．As the exudate extends into the surrounding medullary bone，the radiographic appearance will reflect the bone loss by exhibiting a faintness of the trabecular pattern and an increased radiolucency．Because a periapical abscess is a rapid lytic process，the radiographic appearance will not exhibit a distinct line of demarcation between the inflammatory process and the normal bone．
●Pathological features:
The microscopic features of a periapical abscess are similar to those of an
abscess in other parts of the body．An outer thin capsule of fibrous tissue is infiltrated with lymphocytes and plasma cells．A wide zone of granulation tissue containing a mixture of neutrophils，lymphocytes，plasma cells，and macrophages surrounds a central core of tissue that has undergone disintegration and liquefaction and is composed of purulent exudate．In many lesions，bacterial colonies are readily apparent．
★ Summary： Possible complications of acute periapical periodontitis
●Suppuration
●Regional lymphadenopathy
●Spreading infection
(III) Chronic periapical periodontitis
●Clinical features
The term chronic apicaf periodontitis is used to denote the earliest
radiographic evidence of extension of the inflammatory process from the pulpal chamber into the adjacent periodontal membrane around the apical foramen．Although the outline of the apical alveolar bone is still visible on a radiograph，the periodontal membrane in this region will appear to be widened．Clinically the tooth may still exhibit some faint evidence of vitality when it is electrically stimulated，and it will usually have a positive reaction to a percussion test．The histopathologic findings are variable and will refect the type of inflammation that existed in the pulp．This condition is merely a transitory phase between pulpitis and the more distinct forms of periapical lesions．
Chronic periodontitis is a low-grade infection. It may follow an acute infection
that has been inadequately drained and incompletely resolved. The tooth is non-vital and may be slightly tender to percussion but otherwise symptoms may be minimal. Frequently, chronic periodontitis is first recognised as a rounded area of radiolucency at the apex of a tooth (an ‘apical granuloma’) in a routine radiograph. The area is usually about 5mm in diameter and has well-defined margins. A distinct cortex is sometimes interpreted as early cyst formation, but this cannot be distinguished without a biopsy.
●Pathological features:
Chronic periodontitis is a typical chronic inflammatory reaction
characterized by lymphocytes, macrophages and plasma cells. Infection is confined by inflammatory cells, and granulation tissue surrounds the area.
（IV）Periapical granuloma
●Clinical features：
Frequently, chronic periodontitis is first recognised as a rounded area of
radiolucency at the apex of a tooth (an ‘apical granuloma’) in a routine
radiograph. The area is usually about 5mm in diameter and has well-defined
margins. A distinct cortex is sometimes interpreted as early cyst formation, but
this cannot be distinguished without a biopsy. An uncommon complication,
but sometimes the first sign of periapical periodontitis, is the tracking of a
sinus on to the skin surface. This most frequently happens on or near the chin
as a result of a long-forgotten blow and death of a lower incisor . In such cases
the crown of the damaged tooth is usually discoloured and may be chipped.
●Radiographic features：
The radiographic appearance of periapical granuloma occurs as an oval or
rounded radiolucency with a well-demarcated outline located at the apex of the tooth．Rarely the radiolucency will be located away from the apex and centered on the opening of a lateral canal．A periapical granuloma that periodically under
goes acute exacerbations will have a less distinct line of demarcation between the bone and the granulomatous tissue than a static，quiescent lesion．Frequent findings associated with a long-standing periapical granuloma are hypercemen- tosis of the apical third of the root and resorption resulting in blunting of the root tip．Many patients fail to associate the sinus with dental infection but competent endodontic treatment causes the sinus to heal remarkably quickly.
●Pathological Features:
A periapical granuloma is composed of an outer capsule of dense fibrous tissue and a central zone of granulation tissue．The central zone will often contain macrophages with a foamy cytoplasm caused by phagocytized cholesterol．Some cholesterol crystals may be present，surrounded by multinucleated giant cells．Throughout，the soft tissue will be a diffuse infiltrate of lymphocytes and plasma cells．A frequent finding is the presence of irregular islands and strands of epithelium，a result of prolonged，mild stimulation of the rests of Malassez．These rests are the remnants of the Hertwig root sheath，the epithelial membrane that determines the shape of the roots of developing teeth．
The granulation tissue grows into a rounded mass (a ‘granuloma’), and
steoclasts resorb the bone to accommodate it. Despite absence of symptoms, there is no spontaneous healing because of the persistent reservoir of infection in the root canal. Instead, granulation tissue proliferates round the focus of irritation at the tooth apex, and surrounding bone is resorbed to leave a round area of radiolucency.