Dentinal plugs

# Which of the following creates the phenomena of dentinal plugs?
A. Adhesive
B. Debris from the smear layer
C. Oxalic acid
D. Sclerotic dentin
E. Primer (form micro/macrotags)

Dentinal or smear plugs are composed of the debris from the smear layer.

The smear layer is documented to be about
0.5-2mm thick layer of debris with a  mainly granular substructure that entirely coverst he dentin. The surface of the smear layer appears quite irregular.

The orifices of dentinal tubules are
obstructed by debris tags known as smear
plugs or dentinal plugs. These dentinal
plugs extend into the tubules to a depth of
1-10 micrometers.

The smear layer is reported to reduce
dentinal permeability by about 86% due to
dentinal plugging.

Dentinal plugs are removed by acid etching
the tooth surface with phosphoric acid.

HCl secretion and gastric motility

# Which of the following hormone's action results in HCl secretion and gastric motility?
A. GIP
B. Secretin
C. Gastrin
D. Cholecystokinin

The correct answer is C. Gastrin. 

Gastrin is stimulated by amíno acids and

peptides in lumen, distension. It stimulates

HCl secretion and gastric motility.

Other hormones of gastrointestinal system:

Cholecystokinin: Stimulated by fatty acids,

and amino acids in duodenum. Increases

pancreatic digestive enzyme secretion and

increases bile secretion from the

gallbladder.

Secretin: Stimulated by a low pH in the

duodenum. Increases bicarbonate release

from the pancreases and decreases gastric

motility and gastric acid secretion.

GIP: Stimulated by fat and glucose in the

duodenum. Increases insulin release and

decreases gastric motility and gastric acid secretion.

Viruses capable of causing cell transformation

# Which of the following viruses is NOT capable of causing cell transformation?
A. Retrovirus
B. Herpes virus
C. Hepatitis B virus
D. Human papilloma virus
E. Picorna virus

The correct answer is E. Picorna virus.

Picornavirus is an extremely small, ether-
resistant RNA virus which is not capable of
cell transformation. This virus can cause
several different disease conditions.

Diseases caused by Picornavirus include:
- Poliomyelitis
- Herpangina
- Aseptic meningitis
- Encephalomyocarditis
- Foot-and-mouth disease

Prognosis of a tooth

# Which of the following is the MOST critical factor determining the prognosis of a periodontally involved tooth?
A. Mobility of the tooth
B. Probing depth
C. Amount of attachment loss
D. Presence of furcation involvement

The correct answer is C. Amount of attachment loss.

The amount attachment loss determines
the prognosis of periodontally
Compromised teeth.

Teeth with severe attachment loss and
vertical mobility present a hopeless
prognosis and must be extracted to avoid
infection that may compromise other teeth.
The higher the quantity of attachment, the
better the prognosis.

Elevators are instruments designed to:

# Elevators are instruments that are designed to:
A. Engage the tooth coronal to the cementoenamel junction
B. Retract the crestal gingiva before forceps are used
C. Reflect a full thickness flap before forceps are used
D. Engage the tooth apical to the cementoenamel junction

Elevators are instruments used to elevate
the tooth out of its socket.

Elevators are designed to engage the root
portion of the tooth below the
cementoenamel junction.

Elevators are inserted into the periodontal
ligament space, create more room for tooth
movement, and help elevate the tooth out of its socket.

Most undesirable property of sodium hypochlorite

# Which of the following is the most UNDESIRABLE property of sodium hypochlorite?
A. Tendency to bleach tooth structure
B. Reaction with chelating agents
C. Smell
D. Corrosiveness to endodontic files
E. Toxicity to vital tissue

The correct answer is E. Toxicity to vital tissue.

Sodium hypochlorite in undiluted or
excessive amounts is toxic to vital tissues
and can cause periapical tissue damage
and pain.
Sodium hypochlorite is a good disinfectant
that is used in dentistry as an endodontic
canal irrigant at a diluted concentrations.
Sodium hypochlorite is used often used to
disinfect gutta percha points prior to
placement and obturation of the canal.

First step in cavity preparation

# Which of the following describes the 1st step in cavity preparation according to G.V. Black?
A Retention form
B. Outline form
C. Resistance form
D. Convenience form

The correct answer is B. Outline form.

The 1st step in cavity preparation according
to G V Black is to establish the outline form.
The initial extension or the outline form of
the tooth preparation should be visualized
preoperatively by estimating the extent of
the defect, the preparation form requirements of the amalgam, and the need
for the adequate access to place amalgam
into the tooth.

G.V Blacks various steps of cavity preparation are:
- Establish outline form
- Obtain retention form
- Obtain resistance form
- Obtain convenience form