Impurity found in nitrous oxide

# The impurity that is theoretically found in nitrous oxide that is considered slightly toxic is:
A. Methane
B. Cyclohexane
C. Ethylene oxide
D. Nitric oxide

The correct answer is D. Nitric oxide.

Nitrous oxide is a gas that creates
analgesia and dissociated anesthesia and
is commonly used in dentistry.

Nitrous oxide was first used by Horace
Wells for his own tooth extraction by his
assistant.

Nitrous oxide is used in general anesthesia
to enhance the effect of other drugs being
administered by allowing the concentration
of other drugs to be decreased without
decreasing their effect.

When nitrous oxide reacts with oxygen and
is converted into nitric oxide, causing
vasodilation.

Causes of Dark appearance of radiograph

# After processing a film, you notice that it appears too dark. What is the most likely cause of this problem?
A. Inadequate development time
B. Developer solution too cool
C. Depleted developer solution
D. Excessive developing time

The correct answer is D. Excessive developing time.

The causes underlying dark appearance of a radiograph are:
- Excessive developing time
- Developer solution too hot
- Inaccurate timer or thermometer
- concentrated developer solution

Solutions for the dark appearance of radiograph
- Chcck development time.
- Check developer temperature.
- Replace faulty timer or thermometer.
- Replenish developer with fresh solutions as needed.

Coronoid process of the mandible often appears in periapical x-rays of:

# The image of the coronoid process of the mandible often appears in periapical x-rays of:
A. The incisor region of the mandible
B. The molar region of the mandible
C. The incisor region of the maxilla
D. The molar region of the maxilla

The correct answer is D. The molar region of the maxilla.

As the mouth is opened, the coronoid process moves forward, and therefore it comes into  view

most often when the mouth is opened to its fullest extent at the time the exposure is made.

It is evidenced by a tapered or triangular radiopacity, which may be seen below, or in some instances superimposed on the molar teeth and maxilla.

The coronoid process appears as a triangular-shaped radiopacity.

Contraindication of Pulpotomy

# Pulpotomies are CONTRAINDICATED on primary molars with which of the following?
A. Radiographic evidence of deep caries approximating the pulp chamber
B. Radiographic evidence of internal resorption
C. Sensitivity to sweets
D. Exposure of the pulp during caries excavation

The correct answer is B. Radiographic evidence of internal resorption.

Root canal therapy is indicated to treat
cases involving internal resorption.

When a carious lesion approximates or
extends into the pulp chamber of a
deciduous tooth, removal of coronal pulp is
performed to prevent the spread of the
infection into the radicular pulp.

Pulpotomies are performed on deciduous
teeth to prevent premature tooth loss and
potential loss of space.

Careful clinical and radiographic
assessment along with the child's medical
and dental history are necessary before
performing a pulpotomy.

Pulpotomy is contraindicated where there is:
- Internal resorption (root canal therapy
indicated)
- Perforation of pulp chamber floor
- Over 2 root resorption
- Cellulitis
- Localized abscess
- Draining sinus
- Inability to isolate the tooth
- Inability to properly restore tooth after the
procedure

Severe pain of dentoalveolar abscess

#Sudden relief of severe pain associated with a dentoalveolar abscess can be explained by which of the following?
A. Neutralizing effect of tissue enzymes
B. Walling-off of the infection by the body
C. Rupture of the abscess from the periosteum into the soft tissue
D. Neurotoxic effects of bacterial toxins anesthetize the nocioceptors

The correct answer is C. Rupture of the abscess from the periosteum into the soft tissue.

Dentoalveolar abscesses are an accumulation of pus within the teeth, gums,
and supporting alveolar bone.

The accumulation of pus within the
dentoalveolar abscess creates hydrostatic
pressure, resulting in the sensation of a
severe pain.

Dentoalveolar abscesses are treated
through root canal treatment and possibly
incision and drainage depending upon case
severity.

Drainage of the lesion releases the pressure
caused by the suppuration and results in a
sudden relief of pain is experienced by the
patient.

The major symptom of dentoalveolar
abscess is a severe, intense, and throbbing
pain which worsens with the passage of
time.

Dentoalveolar abscesses can be partially
diagnosed by noting the presence of a
periapical radiolucency.

Cementoblastoma is more often seen

# The cementoblastoma is more often seen:
A. In the mandible than in the maxilla, and more often posterior than in the anterior regions
B. In the mandible than in the maxilla, and more often anterior than in the posterior regions
C. In the maxilla than in the mandible, and more often posterior than in the anterior regions
D. In the maxilla than in the mandible, and more often anterior than in the posterior regions

The correct answer is A. In the mandible than in the maxilla, and more often posterior than in the anterior regions

The cementoblastoma, also known as the true cementoma, is a rare benign neoplasm of cementoblast origin. It occurs predominantly in the second and third decades, typically before 25 years of age. It is more often seen in the mandible than in the maxilla and more often posterior than in the anterior regions. It is intimately associated with the root of a tooth, and the tooth remains vital. It may cause cortical expansion and, occasionally, lowgrade intermittent pain. Radiographically, this is a well-circumscribed radiopaque lesion that replaces the root of the tooth. It is usually surrounded by a radiolucent ring. Because of the intimate association of this lesion with the tooth root, this lesion cannot be removed without sacrificing the tooth. There is no recurrence.

Note: To distinguish this lesion from condensing osteitis - in condensing osteitis, you can distinguish

the root outline.

Odontogenic keratocyst (OKC) is derived from:

# The odontogenic keratocyst (OKC) is derived from:
A. Hertwig's epithelial root sheath
B. The reduced enamel epithelium
C. Remnants of the dental lamina
D. A pre-existing osteoma

The correct answer is: B. Reduced enamel epithelium.

Keratocysts differ from other odontogenic cysts in their microscopic appearance and clinical behavior.

They may resemble periodontal, primordial, or follicular cysts. Usually, they cannot be distinguished

radiographically. 

Clinical features:

• Wide age range. peak occurrence in 2nd and 3rd decades

• Lesions found in children are often reflective of multiple odontogenic keratocysts as a component

of the nevoid basal cell carcinoma syndrome

• More common in males than females

• The chief site of involvement is the mandible, in approximately a 2 to 1 ratio

• In the mandible. most occur within the posterior portion of the body and ramus region

• Typically asymptomatic

Radiographic features:

• Well-demarcated area of radiolucency with a scalloped, radiopaque margin

• Unilocular or multilocular

Microscopicall y:

• The lining epithelium is thin and parakeratinized.

• The basal layer is palisaded with prominent, polarized, and intensely staining nuclei of uniform

diameter

• The lumen may contain large amounts of keratin debris or clear fluid similar to serum transudate

• The parakeratotic type fonns 85 to 95% of all odontogenic keratocysts; the balance is made

up of the orthokeratinized variant.