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.