MDS PREP
What is force applied per unit area?
1) Strain
2) Stress
3) Couple
4) Center of resistance
Orthodontics Answer: 2
SOLUTION
Stress is the force applied per unit area while strain can be defined as the internal distortion per unit area.
Stress and strain are inter-related terms as stress is an external force acting upon a body while strain is the resultant of stress on that body.
Strain can be expressed in the form of a change in either the external dimension or internal energy of the body.
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
Which dimension in which arch is considered as a safety value for pubertal growth spurts?
1) Maxillary intercanine dimension
2) Mandibular intercanine dimension
3) Maxillary intermolar width
4) Mandibular intermolar width
Orthodontics Answer: 1
SOLUTION
Intercanine width serves as safety valve for dominant horizontal basal mandibular growth spurt.
Which of these is the ideal appliance for correction of posterior cross bite due to digit sucking habit?
1) Tongue spikes
2) Hay rakes
3) Maxillary lingual arch with palatal crib
4) Quad helix
Orthodontics Answer: 4
Classification of appliances for thumb-sucking
1. Removable appliances- These are passive appliances. These are retained in the oral cavity by means of clasps and they norm have one of these following additional components:
a. Tongue spikes
b. Tongue guard
c. Spurs/rake
2 Fixed appliances
a. Quad helix
b. Hay rakes
c. Maxillary lingual arch with palatal crib
The ideal appliance to correct posterior cross-bite caused due to digit sucking is Quad Helix. It is a lingual arch which is adjustab and needs very little patient cooperation because it is fixed and is reliable and easy to use.
The main disadvantage of uprighting first molar with a loop lingual arch is
1) Extrusion of molars
2) Overcorrection of molars
3) Flaring of mandibular incisors
4) All of the above
Orthodontics
Answer: 3
One of the main disadvantages of using a loop lingual arch to upright the first molar is that it can lead to flaring of the mandibular incisors due to the forces applied.
Relative to a heterogenous population the incidence of malocclusion in a homogenous population is
1. lower
2. slightly higher
3. significantly higher
4. about the same
Orthodontics
Answer: 1
In a homogeneous population, the genetic variation is less compared to a heterogeneous population. Malocclusion is influenced by both genetic and environmental factors. A homogenous population, which is more genetically similar, would be expected to have a more uniform expression of dental traits, including a lower incidence of malocclusion, assuming that the specific genetic factors for malocclusion are not prevalent in that particular population. In a heterogeneous population, the greater genetic diversity can lead to a higher incidence of malocclusion due to a wider range of genetic combinations contributing to dental misalignments.
Ashley-Howe model analysis is used to predict
1) Tooth material excess
2) Maxillo - mandibular relationships
3) Basal bone-transverse relationship
4) Growth prediction
Orthodontics
Answer: 3
Ashley-Howe Model Analysis
The Ashley-Howe model analysis is a method used in
orthodontics to assess the relationship of the dental arches and the position of
the teeth, particularly in the context of planning orthodontic treatment. This
analysis is particularly useful for evaluating the transverse dimension of the
dental arches and understanding how the maxilla (upper jaw) and mandible (lower
jaw) relate to each other.
Measurement Parameters:
The analysis involves measuring specific distances and angles on dental
casts or models. Key measurements may include:
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 help in determining the transverse relationships of
the dental arches.
Classification:
The results of the Ashley-Howe analysis can help classify the dental
arch relationships into different categories, such as:
Normal: Where the measurements fall within the
expected range.
Narrowed: Indicating a constricted arch that may
require expansion.
Widened: Indicating a broader arch that may need to
be reduced or managed differently.
Clinical Application:
The Ashley-Howe model analysis is particularly useful in treatment
planning for orthodontic cases involving:
Crossbites: Where the upper teeth are positioned
inside the lower teeth.
Crowding: Where there is insufficient space for
teeth to erupt properly.
Expansion Needs: Determining if a patient requires
arch expansion to correct transverse discrepancies.
Treatment Implications:
Based on the analysis, orthodontists can decide on appropriate treatment
modalities, which may include:
Orthodontic Appliances: Such as expanders to widen
the arch.
Extraction: In cases of severe crowding or when
space needs to be created.
Comprehensive Orthodontic Treatment: To align the
teeth and improve occlusion.
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