MDS PREP
What is the relation of the lower first molar to the upper first molar in an
Angle Class III malocclusion?
1. distal
2. lateral
3. mesial
4. normal
Orthodontics Answer: 3
Angle Class III Malocclusion:
Angle Classification:
The Angle classification system, developed by Edward Angle, is a
widely used method for categorizing malocclusions based on the
relationship of the first molars and the canines.
Class III Malocclusion:
In Angle Class III malocclusion, the lower first molar is positioned
more mesially (toward the midline) relative to the upper first molar.
This means that when the first molars are in occlusion, the lower first
molar is ahead of the upper first molar.
Clinical Implications:
Class III malocclusion is often associated with a prognathic
mandible (where the lower jaw is positioned forward) or a retruded
maxilla (where the upper jaw is positioned backward). This can lead to
various functional and aesthetic concerns, including difficulties with
biting and chewing, as well as facial profile changes.
Baker anchorage utilizes
1) Intermaxillary anchorage with screws
2) Intramaxillary anchorage with screws
3) Intermaxillary anchorage with elastics
4) Intramaxillary anchorage with elastics
Orthodontics Answer: 3
SOLUTION
Intermaxillary anchorage or Baker's Anchorage. This type of anchorage involves using elastics from one jaw to the other, in the form of either Class 2 elastics (moving upper teeth back) where lower molar teeth serve as anchors, or Class 3 elastics (moving lower teeth back) where upper molars serve as anchors.
Intramaxillary anchorage is also used in the form of E-chain, when elastics are used from the back molar teeth to the front teeth in the same jaw to move teeth back of the mouth.
The angle of convexity
1) SNA
2) NAPog.
3) ANB
4) SNB
Orthodontics Answer: 2
SOLUTION
Angle of Convexity The angle of convexity is formed by the intersection of line from N to point A, to point A to pogonion.
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.
Which of the following are included in the Orthodontic camouflage methods for treating class II malocclusion?
1) Retraction of upper teeth and forward movement of lower teeth
2) Retraction of maxillary incisors into pre-molar extraction space
3) Distal movement of maxillary molars
4) All of the above
Orthodontics Answer: 4
SOLUTION
The following three patterns of tooth movement can be used to correct a Class II malocclusion:
· A combination of retraction of the upper teeth and forward movement of the lower teeth, without tooth extractions
· Retraction of maxillary incisors into a premolar extraction space
· Distal movement of maxillary molars and eventually the entire upper dental arch
Premature exfoliation of primary mandibular canine is most often the sequelae of:
1) Caries
2) Trauma
3) Serial tooth extraction
4) Arch length inadequacy
Orthodontics Answer: 4
SOLUTION
The two major symptoms of severe crowding in the early mixed dentition are severe irregularity of the erupting permanent incisors and early loss of primary canines caused by eruption of the permanent lateral incisors. The children with the largest arch length discrepancies often have reasonably well aligned incisors in the early mixed dentition, because both primary canines were lost when the lateral incisors erupted
After a definitive analysis of the profile and incisor position, these patients face the same decision as those with moderate crowding; whether to expand the arches or extract permanent teeth. In the presence of severe crowding, limited treatment of the problem will not be sufficient and permanent tooth extraction is most likely the best alternative.
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
The diameter of labial-bow of the maxillary plate
1) 0.5-0.6 mm
2) 0.6-0.8 mm
3) 0.7-0.8 mm
4) 0.8-1.0 mm
Orthodontics
Answer: 3
The labial bow is a component of the maxillary denture framework that helps in stabilizing the denture and providing support. The diameter of the labial bow is typically measured to ensure proper fit and function. The standard range for the diameter of the labial bow is generally accepted to be between 0.7 mm and 0.8 mm