MDS PREP
The first ossification center of the mandible in six weeks old human embryo is found in which of the following locations
1) Future coronoid process
2) Future condylar process
3) Future mental foramen
4) Future mandibular foramen
Orthodontics Answer: 3
SOLUTION
The mandible is ossified in the fibrous membrane covering the outer surfaces of Meckel’s cartilages.
These cartilages form the cartilaginous bar of the mandibular arch, and are two in number, a right and a left.
Ossification takes place in the membrane covering the outer surface of the ventral end of Meckel’s cartilage , and each half of the bone is formed from a single center which appears, near the mental foramen, about the sixth week of fetal life.
By the tenth week the portion of Meckel’s cartilage which lies below and behind the incisor teeth is surrounded and invaded by the membrane bone
Which of the following is not one of the consequences of using Herbst appliance in treatment of Class II malocclusion?
1) Increase in mandibular growth
2) Over corrected Class I molar relation
3) Increase in SNB angle
4) Increase in overjet
Orthodontics Answer: 4
Solution
The following are the effects when Herbst appliance used for treatment of Class II malocclusion:
1. Class I molar relation or over-corrected Class I molar relation.
2. Increased mandibular growth
3. Distal driving of maxillary molars which helps to achieve molar relation.
4. Reduction of overjet by increasing mandibular length and proclination of mandibular incisors.
5. Inhibitory effect on sagittal maxillary growth
6. Weislander suggested double contour of glenoid fossa which indicates anterior transformation of glenoid fossa
7. Increased SNB angle and decreased SNA angle.
What is the Angle classification of occlusion based upon?
Orthodontics Answer: 3
1. The position of the maxillary incisors relative to the mandibular incisors
2. The position of the maxillary incisors relative to the mandibular incisors
3. The position of the maxillary canines and first permanent molars relative to the mandibular canines and first permanent molars.
4. The position of the upper lip relative to the lower lip
The position of the maxillary canines and first permanent molars relative to the mandibular canines and first permanent molars
If PMBAW% is 44 in Howe"s analysis, it indicates
1) Extraction case
2) Expansion case
3) Borderline case
4) None of the above
Orthodontics
Answer: 3
The primary purpose of Howe's Analysis is to assess the width of the
dental arches and to identify any discrepancies between the maxillary
(upper) and mandibular (lower) arches. This is particularly important in
cases of malocclusion, where the alignment of the teeth and the relationship
between the jaws may be compromised.
The analysis involves measuring specific distances on the dental casts,
including:
Intercanine Width: The distance between the cusp
tips of the canines.
Interpremolar Width: The distance between the cusp
tips of the first premolars.
Intermolar Width: The distance between the cusp
tips of the first molars.
These measurements are used to calculate the Percentage of
Maxillary Buccal Arch Width (PMBAW%), which is a key indicator in
the analysis.
The results of Howe's Analysis can indicate different treatment needs:
Normal Case: A PMBAW% within a certain range
(typically around 50-60%).
Narrow Case: A PMBAW% below the normal range,
indicating a need for arch expansion.
Wide Case: A PMBAW% above the normal range, which
may suggest the need for extraction or other interventions.
Borderline Case: A PMBAW% around 44, indicating
that the arch width is at a threshold where careful consideration is
needed for treatment options.
The philtrum of the upper lip is formed largely by the
1) Lateral nasal processes
2) Globular process
3) Maxillary processes
4) Mandibular processes
Orthodontics
Answer: 2
Explanation: The philtrum is the vertical groove located in the middle of the upper lip. It is primarily formed by the fusion of the medial nasal processes, which include the globular process. The globular process is a key structure in the embryonic development of the face, contributing to the formation of the upper lip and the philtrum.
Activation of a reverse labial bow is done by?
1) Opening the loop
2) Compressing the loop
3) Reversing the loop
4) Bending the loop
Orthodontics Answer: 1
Reverse labial bow is so called as activation of the bow is done by opening the U-loop, instead of compressing as is seen in the conventional labial bows.
Which of the following shows 200 % of its adult growth by age 9-10 years
1) Lymphoid
2) General
3) Genital
4) Neural
Orthodontics
Answer: 1
The lymphoid system, which includes lymph nodes, spleen, and other lymphatic tissues, undergoes significant growth during childhood. By the age of 9-10 years, the lymphoid tissue can reach approximately 200% of its adult size due to the increased demand for immune function during this period. This growth is part of the body's preparation for increased exposure to pathogens as children interact more with their environment.
Bone tissue grows by
1) Apposition
2) Interstitial growth
3) Osteoclastic growth
4) Mesenchymal tissue growth
Orthodontics Answer: 1
SOLUTION
Interstitial growth, simply means that it occurs at all points within the tissue. When mineralization takes place so that hard tissue is formed, interstitial growth becomes impossible.