Length of junctional epithelium is:

 # Length of junctional epithelium is:

A. 0.25-1.35 mm

B. 0.5-0.75 mm

C. 1.0-2.0 mm

D. 1.0-1.5 mm

The correct answer is A. 0.25-1.35 mm.

Junctional Epithelium: The epithelium that attaches the gingiva to the tooth's surface, it consists of stratified squamous non-keratinizing epithelium. It is 3-4 layers thick in early life but the number of

layers increases with age to 10-20. It is thicker in the coronal portion but becomes thinner toward the cemento-enamel junction only a few cell layers. The length of the JE ranges from 0.25 to 1.35mm. 

Chronic atrophic candidiasis is commonly referred to as:

 # Chronic atrophic candidiasis is commonly referred to as:

 A. Oral Thrush

B. Denture stomatitis

C. Angular cheilitis

D. Erythema multiforme

The correct answer is B. Denture stomatitis.

Denture stomatitis should be mentioned because it is often classified as a form of erythematous candidiasis, and some authors may use the term chronic atrophic candidiasis synonymously. This condition is characterized by varying degrees of erythema, sometimes accompanied by petechial

hemorrhage, localized to the denture-bearing areas of a maxillary removable dental prosthesis. 

Although the clinical appearance can be striking, the process is rarely symptomatic. Usually, the patient admits to wearing the denture continuously, removing it only periodically to clean it. Whether this represents actual infection by C. albicans or is simply a tissue response by the host to the various microorganisms living beneath the denture remains controversial.

Stress shielding effect is seen in:

 # Stress shielding effect is seen in:

 A. Miniplates

B. Compression bone plating

C. Lag screw

D. Transosseous wiring

The correct answer is B. Compression bone plating.

Stress shielding is the reduction in bone density (osteopenia) as a result of removal of typical stress from the bone by an implant. This is because by Wolff's law, bone in a healthy person or animal remodels in response to the loads it is placed under. 

The most obvious postoperative complications of internal fixation using compression plates are misplaced bone segments or fixation devices. These complications are readily identified by clinical examination (e.g. malocclusion) or postoperative radiographic examinations. A second surgical procedure will correct such complications. Other complications related to rigid internal fixation include palpability, infection, extrusion or exposure, translocation, stress shielding, cortical osteopenia, and nonunion.

MCQs on Dental Materials - Metallurgy

# All of the following statements about cast cobalt alloys are true EXCEPT:
A. They have a modulus of elasticity twice that of gold alloys
B. They are more rigid than gold alloys
C. They have higher ductility than gold alloys
D. They have a lower proportional limit than gold alloys

# The contraction of gold alloys on solidifying is approximately:
A. 0.4%
B. 1.4%
C. 2.4%
D. 3.4%

# Addition of large amounts of platinum to a casting gold alloy will:
A. Decrease its strength and ability to be hardened
B. Decrease its tarnish resistance
C. Increase its fusion temperature
D. Redden the alloy

# The pattern for the metallic framework of a removable partial denture is fabricated from:
A. Inlay wax type-II
B. Boxing wax
C. Modelling wax
D. Casting wax

Which of the following drugs is likely to damage the eighth cranial nerve when administered for a long period of time ?

 # Which of the following drugs is likely to damage the eighth cranial nerve when administered for a long period of time ?

 A. Ethambutol

 B. Isoniazide

 C. Rifampicin

 D. Streptomycin

The correct answer is D. Streptomycin.

Nephrotoxicity, ototoxicity, and contact sensitization (due to this, topical application is not indicated) are common side effects of Streptomycin. 8th nerve is usually affected. Vestibular involvement is more common and cochlear involvement is less common. 

Which of the following structures is not of ectodermal origin?

 # Which of the following structures is not of ectodermal origin?

A. Hunter Schreger bands

B. Enamel spindles

C. Enamel tufts

D. Enamel lamellae

The correct answer is B. Enamel spindles.

Enamel spindles are odontoblastic processes, which extend into enamel. Enamel spindles are mesenchymal in origin.

Malocclusion representing a transverse deficiency is often referred to as:

 # Malocclusion representing a transverse deficiency is often referred to as:

A. Open bite

B. Closed bite

C. Cross bite

D. Deep bite

The correct answer is C. Cross bite.

Patients with maxillary transverse deficiency usually have a narrow palate and a posterior crossbite. If the maxilla is narrow relative to the rest of the face, a diagnosis of transverse maxillary deficiency is justified. Occlusal relationships must be considered in all three planes of space. Lingual posterior crossbite (i.e., upper teeth lingual to lower teeth) is the major deviation from the normal transverse dental relationship and reflects deviations from ideal occlusion in the transverse plane of space.

Ref: Contemporary Orthodontics, William R. Proffit, 6th Edition.