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
In classifying molar relation in patient with premature loss of primary molar, additional relation to be noted is
1) Incisor relation
2) Canine relation
3) Midline relation
4) Premolar relation
Orthodontics Answer: 2
SOLUTION
Which of the fibers attached to cementum are most likely to contribute to relapse of tooth rotation:
1) Gingival group of fibers
2) Apical fibers
3) Horizontal fibers
4) Oblique fibers
Orthodontics Answer: 1
SOLUTION
Gingival group of fibers
Principal fibers of the periodontal ligament rearranges themselves quite rapidly to the position in about 4 weeks.The supra-alveolar gingival fiber take as much as 40 weeks to rearrange around the new position and thus predispose to relapse.
The basic principle of Orthodontic spot welder lies on the concept of :-
1 Heat technique
2) Quenching
3) Diodelasers
4) Electrode Technique
Orthodontics Answer: 4
SOLUTION
The type of welding used to join Orthodontic components is called Spot welding. The heat source usually a high amperage electricity. Orthodontic spot welders employ the electrode technique, in which current is conducted through two copper electrodes. The copper electrode in a welding unit serve the following purposes :
1. Transmit current to the metals to be joined so as to cause a rapid increase in temperature.
2. The electrodes help in conducting the heat produced away from the area so as to preserve the properties of stainless steel around the weld spot.
3. The electrode also help in holding together the two metals to be joined.
4. The electrodes are designed to apply pressure on the metals being joined. As soon as the temperature increases, the pressure exerted by the electrodes helps in squeezing metal into each other.
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.
Slow progression in molar uprighting in an adult patient is due to
1) Occlusion not being relieved
2) Overcontoured spring
3) Back of anchorage control
4) All of the above
Orthodontics
Answer: 1
Slow progression in molar uprighting can occur if the occlusion is not
adequately relieved. If the opposing teeth are still in
contact, it can hinder the movement of the molar being
uprighted.
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.