Course -NBDE NOTES

Odontogenic Cysts


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
 

HISTOLOGIC CHANGES OF THE PULP


HISTOLOGIC CHANGES OF THE PULP

Regressive changes


Pulp decreases in size by the deposition of dentin.
This can be caused by age, attrition, abrasion, operative procedures, etc.
Cellular organelles decrease in number.

Fibrous changes

They are more obvious in injury rather than aging. Occasionally, scarring may also be apparent.

Pulpal stones or denticles

They can be: a)free, b)attached and/or c)embedded. Also they are devided in two groups: true or false. The true stones (denticles) contain dentinal tubules. The false predominate over the the true and are characterized by concentric layers of calcified material.

Diffuse calcifications

Calcified deposits along the collagen fiber bundles or blood vessels may be observed. They are more often in the root canal portion than the coronal area.

Histology of the Cementum

Cementum is a hard connective tissue that derives from ectomesenchyme.

Embryologically, there are two types of cementum:
Primary cementum: It is acellular and develops slowly as the tooth erupts. It covers the coronal 2/3 of the root and consists of intrinsic and extrinsic fibers (PDL).
Secondary cementum: It is formed after the tooth is in occlusion and consists of extrinsic and intrinsic (they derive from cementoblasts) fibers. It covers mainly the root surface.

Functions of Cementum

It protects the dentin (occludes the dentinal tubules)
It provides attachment of the periodontal fibers
It reverses tooth resorption

Cementum is composed of 90% collagen I and III and ground substance.
50% of cementum is mineralized with hydroxyapatite. Thin at the CE junction, thicker apically.

Fermentation  


Anaerobic organisms lack a respiratory chain. They must reoxidize NADH produced in Glycolysis through some other reaction, because NAD+ is needed for the Glyceraldehyde-3-phosphate Dehydrogenase reaction (see above). Usually NADH is reoxidized as pyruvate is converted to a more reduced compound, that may be excreted.

The complete pathway, including Glycolysis and the re-oxidation of NADH, is called fermentation.

For example, Lactate Dehydrogenase catalyzes reduction of the keto group in pyruvate to a hydroxyl, yielding lactate, as NADH is oxidized to NAD+.

Skeletal muscles ferment glucose to lactate during exercise, when aerobic metabolism cannot keep up with energy needs. Lactate released to the blood may be taken up by other tissues, or by muscle after exercise, and converted via the reversible Lactate Dehydrogenase back to pyruvate

Fermentation Pathway, from glucose to lactate (omitting H+):

   glucose + 2 ADP + 2 P→ 2 lactate + 2 ATP

Anaerobic catabolism of glucose yields only 2 “high energy” bonds of ATP.

Terminology related to Anatomy

A. Anatomic position-erect body position with the arms at the sides and the palms  upward

B. Plane or section

1. Definition-imaginary flat surface formed by an extension through an axis

2. Median plane-a vertical plane. that divides a body into right and left halves

3. Sagittal plane

  • Any plane parallel to the median plane
  • Divides the body into right and left portions

 

4. Frontal plane

  • Vertical plane that forms at right angles to the sagittal plane
  • Divides the body into anterior and posterior sections
  • Synonymous with the term coronal plane

 

5. Transverse plane

  • Horizontal plane that forms at right angles to the sagittal and frontal planes
  • Divides the body into upper and lower portions
  • Synonymous with the term horizontal plane

 

 

C. Relative positions

1. Anterior

  • Nearest the abdominal surface and the front of the body
  • Synonymous with the term ventral
  • In referring to hands and forearms, the terms palmar and Volar are used

2. Posterior

  • Back of the body
  • Synonymous with the term dorsal

3. Superior

  • Upper or higher
  • Synonymous with the term cranial (head)

4. Inferior

  • Below or lower
  • Synonymous with the term caudal (tail)
  • In referring to the top of the foot and the sole of the foot. the terms dorsal and plantar are used respectively

 

5. Medial-near to the median plane

6. Lateral-farther away from the median plane

7. Proximal-near the source or attachment

8. Distal-away from the source or. attachment

9. Superficial-near the surface

10. Deep-away from the surface

11. Afferent-conducting toward a structure

12. Efferent-conducting away from a structure

Mercury hygiene


Mercury hygiene

  • Do not contact mercury with skin
  • Clean up spills to minimize mercury vaporization
  • Store mercury or precapsulated products in tight containers
  • Only triturate amalgam components-in tightly- sealed capsules
  • Use amalgam with covers
  • Store spent amalgam under water or fixer in a tightly sealed jar
  • Use high vacuum suction during amalgam alloy placement, setting, or removal when mercury may be vaporized
  • Polishing amalgams generally causes localized melting of silver-mercury phase with release of mercury vapor, so water cooling and evacuation must be used

Gypsum Products


Gypsum Products

 

Characteristics

Plaster

Stone

Diestone

Chemical Name

Beta-Calcium Sulfate hemihydrate

Alpha-Calcium sulfate hemihydrate

Alpha-Calcium sulfate hemihydrate

Formula

CaSO4 – ½ H2O

CaSO4 – ½ H2O

CaSO4 – ½ H2O

Uses

Plaster Models ,Impression Plasters

Cast Stone, Investment

Improved Stone, diestone

Water(W)

Reaction Water

Extra Water

Total water

Powder (P)

W/P Ratio

 

18ml

32ml

50ml

100g

0.50

 

18ml

12ml

30ml

100g

0.30

 

18ml

6ml

24ml

100g

0.24

Symptoms of Legionella pneumonia


L: Lungs - Atypical pneumonia.
Relatively nonproductive cough
Dyspnea
Pleuritic or non pleuritic chest pain
Confluent or patchy infiltrates on x-ray
Random fact: Interstitial infiltrates aren’t seen often like in other atypical pneumonias.

E: Encephalon - Neurologic abnormalities.
Headache
Confusion or changes in mental status
Encephalopathy

G: Gastrointestinal symptoms.
Abdominal pain
Nausea
Vomiting
Watery diarrhea

ION: Na ion decreases.
Hyponatremia (serum sodium level of 131 meq/L)

HYPERPLASIA


HYPERPLASIA
It is the increase in the size of an organ or tissue due to increase in the number of its constituent cells. This is seen in organs made up of labile and stable cells.

Causes
I. Increased demand:
- Bone marrow in hypoxia and haemolytic states.
- Thyroid gland in puberty

2. Persistant Trauma:
- Acanthosis of the epidermis in chronic inflammations and in warts.
- Hyperplasia of oral mucosa due tooth and denture trauma.
- Mucosa at the edges of a gastric ulcer.

3. Endocrine target organ:
- Pregnancy hyperplasia of breast.
- Prostatic hyperplasia.

4. Compensatory:

Hyperplasia of kidney when the other kidney has been removed.

5. Idiopathic:
Endocrine organs like thyroid, adrenals, pituitary etc. can undergo hyperplasia with no detectable stimulus. .
 

BETA-LACTAM ANTIBIOTICS


BETA-LACTAM ANTIBIOTICS
β-lactam antibiotics are a broad class of antibiotics including penicillin derivatives, cephalosporins, monobactams, carbapenems and β-lactamase inhibitors; basically any antibiotic agent which contains a β-lactam nucleus in its molecular structure. They are the most widely used group of antibiotics available.

Mode of action All β-lactam antibiotics are bactericidal, and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls.β-lactam antibiotics were mainly active only against Gram-positive bacteria, the development of broad-spectrum β-lactam antibiotics active against various Gram-negative organisms has increased the usefulness of the β-lactam antibiotics.

Common β-lactam antibiotics

Penicillins

Narrow spectrum penicillins:  

benzathine penicillin
benzylpenicillin (penicillin G)
phenoxymethylpenicillin (penicillin V)
procaine penicillin

Narrow spectrum penicillinase-resistant penicillins

methicillin
dicloxacillin
flucloxacillin

Moderate spectrum penicillins : 

amoxicillin, ampicillin

Broad spectrum penicillins :      

co-amoxiclav (amoxycillin+clavulanic acid)

Extended Spectrum Penicillins:    

piperacillin
ticarcillin
azlocillin
carbenicillin
 

Cardiac tamponade


Cardiac tamponade
A. Caused by accumulation of fluid in the pericardium. This severe condition can quickly impair ventricular filling and rapidly lead to  decreased cardiac output and death.

1. Signs and symptoms include:
a. Hypotension.
b. Jugular venous distention.
c. Distant heart sounds.