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.

Y shaped occlusal pattern is found in which teeth?

 # Y shaped occlusal pattern is found in which teeth?

A. Mandibular first premolar

B. Mandibular second premolar

C. Maxillary first premolar

D. Maxillary second premolar

The correct answer is B. Mandibular second premolar. 

The three cusp type mandibular second premolar manifests as a Y shaped occlusal pattern. The three-cusp type appears square lingual to the buccal cusp ridges when highly developed. Each cusp has well-formed triangular ridges separated by deep developmental grooves. These grooves converge in a central pit and form a Y shape on the occlusal surface. 

Y axis is used to analyze:

 # Y axis is used to analyze:

A. Maxillary growth

B. Mandibular growth

C. Both maxillary and mandibular growth

D. To design appliance

The correct answer is B. Mandibular growth.

Y-axis is obtained by joining the sella - gnathion line with the F.H. plane. The mean value is 59 degree with a range of 53 to 66 degree. The angle is larger in Class II Facial patterns than in patient exhibiting Class III pattern. In addition, Y axis indicates the growth pattern of the individual. If the angle is greater than normal, it indicates greater vertical growth of mandible. If the angle is smaller than normal, it indicates greater horizontal growth of mandible.