Odontogenic cysts

Odontogenic cysts are lined with epithelium derived from the following tooth development structures:

• rests of Malassez: radicular cyst, residual cyst
• reduced enamel epithelium: dentigerous cyst, eruption cyst
• Remnants of the dental lamina: Odontogenic keratocyst, lateral periodontal cyst, gingival cyst of adult, glandular odontogenic cyst

Radicular cyst    
    
Radiology

- A well-defined, round or ovoid radiolucency is associated with the root apex or, less commonly in the lateral position, of a heavily restored or grossly carious tooth.

- A corticated margin is continuous with the lamina dura of the root of the affected tooth.

- The appearances are similar to those of an apical granuloma, but lesions with a diameter exceeding 10 mm are more likely to be cystic
    
Pathology

The cyst lumen is lined by a layer of simple squamous epithelium of variable thickness, which may display areas of discontinuity where it is replaced by granulation tissue.

Arcades and strands of epithelium may extend into the cyst capsule, which is composed of granulation tissue infiltrated by a mixture of acute and chronic inflammatory cells. 

This infiltrate reduces in intensity as the more peripheral areas of the cyst capsule are approached, where mature fibrous tissue replaces the
granulation tissue 

Several features associated with inflammatory odontogenic cysts may be present in the cyst lumen, lining and capsule: cholesterol clefts, foamy macrophages, haemosiderin and Rushton's bodies.
    
    
Residual cyst

Radiology

The residual cyst has a well-defined, round/ovoid radiolucency in an edentulous area. Occasionally flecks of calcification may be seen.

Pathology

The lining and capsule are similar to the radicular cyst; however, both appear more mature, with the former lacking the arcades and strands of epithelium extending into the capsule.    

Keratocystic odontogenic tumor-(Odontogenic keratocyst)

The orthokeratinizing odontogenic cyst is considered an unrelated entity without risk of recurrence or aggressive growth or association with Nevoid basal cell carcinoma syndrome

Epidemiology

- 4 - 12% of all odontogenic cysts (often compared to odontogenic cysts even though WHO classifies as tumor)
- Peaks in second and third decade of life, but can occur over wide age range
- 90% are solitary
- Multiple tumors seen in Nevoid Basal Cell Carcinoma Syndrome / Gorlin Syndrome

Sites

- Mandible most commonly involved (65 - 85% of KCOT)
- Most common site: posterior mandible
- Not uncommonly, but not exclusively associated with impacted teeth
- Rarely occurs in soft tissue

Pathophysiology

- Thought to arise from dental lamina
- Two-hit mechanism results in bi-allelic loss of PTCH ("patched") tumor suppressor on 9q22.3-q31 causing dysregulation of p53 and cyclin D1 oncoproteins

- The presence of daughter cysts within the capsule is a well-recognised finding, particularly in those odontogenic keratocysts arising as a component of the basal cell naevus syndrome.

Clinical features

- Often asymptomatic, incidentally discovered on Xray
- Can cause symptomatic swelling
- Symptoms of pain and drainage if secondarily infected
- Can cause local bone and soft tissue destruction, but usually spares teeth and roots

Radiology

- Small lesions often unilocular radiolucent lesion, variable sclerotic margins
- Larger lesions often multilocular, variable scalloped margins

Dentigerous cyst

Radiology
In dentigerous cysts, there is a pericoronal radiolucency greater than 3-4 mm in width that is suggestive of cyst formation in a dental follicle. The well-defined, corticated radiolucency is associated with the crown of an unerupted tooth. Classically the associated crown of the tooth lies centrally within the cyst, but lateral types occur . 

Pathology

The defining feature of a dentigerous cyst is the site of attachment of the cyst to the involved tooth. This must be at the level of the amelocemental junction. The lining of the cyst is composed of a thin layer of epithelium, either cuboidal or squamous in nature, some 2-5 cells thick . This lining is of even thickness and may  include mucous cells along with focal areas of keratinisation of the superficial epithelial cells. The cyst capsule is, classically, free from inflammation. However, in common with the odontogenic keratocyst, the normal features of the epithelial lining may be distorted when an inflammatory infiltrate is present.

Eruption cyst

Radiology

The extra-bony position of the eruption cyst means that the only radiological sign is likely to be a soft tissue mass.

Pathology

An eruption cyst is basically a dentigerous cyst in soft tissue over an erupting tooth. The histological features are similar to those of the dentigerous cyst, though reduced enamel epithelium is often seen.

Gingival cysts

Gingival cysts are commonly found in neonates but are rarely encountered after 3 months of age. 
Many appear to undergo spontaneous resolution. 
White keratinous nodules are seen on the gingivae and these are referred to as Bohn's nodules or Epstein's pearls. 
Arise from epithelial rests of dental lamina epithelium (rests of Serres) within soft tissue
Many open into the oral cavity forming clefts from which the keratin exudes. 

Radiology

Cyst may cause a superficial "cupping out" of alveolar bone, usually not detected on a radiograph but apparent when cyst is excised
 

Epithelial cysts

    Developmental odontogenic cysts
        Odontogenic keratocyst
        Dentigerous cyst (follicular cyst)
        Eruption cyst
        Lateral periodontal cyst
        Gingival cyst of adults
        Glandular odontogenic cyst (sialo-odontogenic)
        
        
    Inflammatory odontogenic cysts

        Radicular cyst (apical and lateral)
        Residual cyst
        Paradental cyst
        
    Non-odontogenic cysts

        Nasopalatine cyst
        Nasolabial cyst
    
Non-epithelial cysts (not true cysts)

    Solitary bone cyst
    Aneurysmal bone cyst

Garre’s Osteomyelitis (Chronic Osteomyelitis with Proliferative Perosteitis)

• Chronic Non Suppurative Sclerosing Osteitis/ Periostitis Ossificans.
• Non suppurative productive disease characterized by a hard swelling.
• Occurs due to low grade infection and irritation
• The infectious agent localizes in or beneath the periosteal covering of the cortex & spreads only slightly into the interior of the bone.
• Occurs primarily in young persons who possess great osteogenic activity of the periosteum.

Clinical Features

• Uncommonly encountered, described in tibia and in the head and neck region, in the mandible.
• Typically involves the posterior mandible & is usually unilateral.
• Patients present with an asymptomatic bony, hard swelling with normal appearing overlying skin and mucosa.
• On occasion slight tenderness may be noted
• pain is most constant feature
• The increase in the mass of bone may be due to mild toxic stimulation of periosteal osteoblasts by attenuated infection.

Radiographic features

• Laminations vary from 1 – 12 in number, radiolucent separations often are present between new bone and original cortex. (“onion skin appearance”)
• Trabeculae parallel to laminations may also be present.

Histologic Features

• Reactive new bone.
• Parallel rows of highly cellular & reactive woven bone in which the individual trabeculae are oriented perpendicular to surface.
• Osteoblasts predominate in this area.

D/D for Garre’s Osteomyelitis

• Ewing's sarcoma
• Caffey’s disease
• Fibrous dysplasia
• Osteosarcoma

Treatment

• Removal of the offending cause.
• Once inflammation resolves, layers of the bone consolidate in 6 – 12 months, as the overlying muscle helps to remodel.
• If no focus of infection evident, biopsy recommended.

Osteomyelitis

Osteomyelitis is an extensive inflammation of a bone. It involves the cancellous portion, bone marrow, cortex, and periosteum

Conditions that alter HOST IMMUNITY

Leukemia, Severe anemia, Malnutrition, AIDS, IV- drug abuse, Chronic alcoholism, Febrile illnesses, Malignancy, Autoimmune disease, Diabetes mellitus, Arthritis, Agranulocytosis

Conditions that alter vascularity of bone

Osteoporosis, Paget’s disease, Fibrous dysplasia, Bone malignancy, Radiation, Virulence of the organisms

Certain organisms precipitate thrombi formation by virtue of their destructive lysosomal enzymes.

Organisms proliferate in enriched host medium while protected from host immunity.

Etiology

- Odontogenic infections
- Trauma
- Infections of oro facial region
- Infections derived from hematogenous route
- Compound fractures of the jaws.

PATHOGENESIS

DEV . OF INFECTION --> BACTERIAL INVASION -->  PUS FORMATION -->  SPREAD OF INFECTION --> INCREASED INTRAMEDULLARY PRESSURE , BLOOD FLOW , OSTEOCLASTIC ACTIVITY --> INFLAMMATORY RESPONSES --> INCREASED PERIOSTEAL PRESSURE --> PROCESS BECOMES CHRONIC GRANULATION TISSUE FORMATION --> LYSIS OF BONE --> SEQUESTRUM FORMATION

Classification

Classification based on clinical picture, radiology, and etiology

Suppurative osteomyelitis

I. Acute suppurative osteomyelitis

II. Chronic suppurative osteomyelitis

– Primary chronic suppurative osteomyelitis

– Secondary chronic suppurative osteomyelitis

III. Infantile osteomyelitis

Nonsuppurative osteomyelitis

I. Chronic sclerosing osteomyelitis

  – Focal sclerosing osteomyelitis

  – Diffuse sclerosing osteomyelitis

II. Garre's sclerosing osteomyelitis

III. Actinomycotic osteomyelitis

IV. Radiation osteomyelitis and necrosis

Infective osteomyelitis

• Tuberculous osteomyelitis
• Syphilitic osteomyelitis
• Actinomycotic osteomyelitis

Tuberculous osteomyelitis

• Non healing sinus tract formation
• Age group affected is around 15 – 40 years.
• Commonly seen in phalanges and dorsal and lumbar vertebrae.
• Usually occurs secondary to tuberculosis of lungs.
• Cases have been reported where mandibular lesions were not associated with pulmonary disease.
• Another common entrance is through a carious tooth via open pulp.
• Usually affects long bones and rare in jaws.
• Results when blood borne bacilli lodge in cancellous bone. Usually in ramus , body of mandible. may mimic parotid swelling or submassetric abscess.

Syphilitic osteomyelitis

• Difficult to distinguish syphilitic osteomyelitis of the jaws from pyogenic osteomyelitis on clinical & radiographic examination.
• Main features are progressive course & failure to improve with usual treatment for pyogenic osteomyelitis.
• Massive sequestration may occur resulting in pathologic fracture.
• If unchecked, eventually causes perforation of the cortex.

Actinomycotic Osteomyelitis

• The organisms thrive in the oral cavity, especially tissues adjacent to mandible.
• May enter the bone through a fresh wound, carious tooth or a periodontal pocket at the gingival margin of erupting tooth.
• Soft or firm tissue masses on skin, which have purplish, dark red, oily areas with occasional zones of fluctuation.
• Spontaneous drainage of serous fluid containing granular material.
• Regional lymph nodes occasionally enlarged.
• Mimics parotitis / parotid tumors

Infantile Osteomyelitis

• Osteomyelitis Maxillaries Neonatarum, Maxillitis of infancy
• Osteomyelitis in the jaws of new born infants occurs almost exclusively in maxilla.

Etiology

• Trauma – through break in mucosa cause during delivery.
• Infection of maxillary sinus
• Paunz & Ramon et al  believe that disease caused through infection from the nose.
• Hematogenous spread through streptococci & pneumococci

Clinical features

• Fever, anorexia & intestinal disturbances.
• swelling or redness below the inner canthus of the eye in lacrimal region.
• Followed by marked edema of the eyelids on the affected side.
• Next, alveolus & palate in region of first deciduous molar become swollen.
• Pus discharge from affected sites

D/D for Infantile Osteomyelitis

• Dacrocystitis neonatarum
• Orbital cellulitis
• Ophthalmia neonatarum
• Infantile cortical hyperostosis

TREATMENT

• Intravenous antibiotics, preferably penicillin.
• Culture & sensitivity testing
• Incision & drainage of fluctuant areas
• Sequestrectomy
• Supportive therapy