MCQs in Orthodontics - Orthodontic Biomechanics

1. In orthodontic biomechanics, a low moment-to-force ratio typically results in which type of tooth movement?
A. Bodily movement
B. Controlled tipping
C. Uncontrolled tipping
D. Intrusion
E. Extrusion


2. The center of resistance of a single-rooted tooth is located approximately at what distance from the alveolar crest?
A. One-third of the root length
B. One-half of the root length
C. Two-thirds of the root length
D. At the apex
E. At the cervical margin

3. Increasing the force magnitude in an orthodontic system primarily affects which aspect of tooth movement?
A. Type of movement
B. Rate of movement
C. Direction of movement
D. Anchorage loss
E. Moment creation

4. A couple in orthodontics is defined as:
A. Two equal and opposite forces
B. A single force applied at the bracket
C. Unequal forces in the same direction
D. Forces causing translation
E. Forces causing intrusion

5. Bodily movement of a tooth requires a moment-to-force ratio of approximately:
A. 1:1
B. 5:1
C. 10:1
D. 15:1
E. 20:1

6. In a sliding mechanics system, what factor most influences the tipping of canines during space closure?
A. Wire size
B. Bracket width
C. Force level
D. Moment-to-force ratio
E. Arch form

 

7. The application of a force passing through the center of resistance results in:
A. Pure rotation
B. Pure translation
C. Tipping
D. Torque
E. Extrusion

8. In orthodontic treatment, uncontrolled tipping is associated with:
A. High moment-to-force ratio
B. Low moment-to-force ratio
C. Equal moment and force
D. No moment applied
E. Continuous force

9. The center of rotation during uncontrolled tipping of a tooth is located at:
A. The bracket
B. The center of resistance
C. The apex
D. The cervical third
E. Midway between crown and root

10. Increasing the interbracket distance in an archwire affects the moment-to-force ratio by:
A. Increasing the moment
B. Decreasing the moment
C. Increasing the force
D. Decreasing the force
E. No effect

11. In intrusion mechanics, the optimal force for incisor intrusion is approximately:
A. 10-20 grams
B. 50-100 grams
C. 150-200 grams
D. 250-300 grams
E. 400 grams

12. A V-bend in an archwire creates which type of force system?
A. Single force
B. Couple at both ends
C. Moment only
D. Translation
E. Intrusion

13. The biological response to orthodontic force involves initial:
A. Bone formation
B. Hyalinization
C. Osteoclast activation
D. PDL widening
e. Tooth extrusion

14. In en-masse retraction, to achieve bodily movement, what is essential?
A. Low force
B. High moment
C. Elastic chains
D. No anchorage
E. Tipping allowed

15. The moment generated by an off-center force is calculated as:
A. Force × Distance
B. Force / Distance
C. Distance / Force
D. Force² × Distance
E. Distance² / Force

16. In torque expression, the third-order bend relates to:
A. Mesio-distal angulation
B. Bucco-lingual inclination
C. Vertical position
D. Rotation
E. Intrusion

17. Absolute anchorage in orthodontics is best provided by:
A. Headgear
B. Transpalatal arch
C. Temporary anchorage devices (TADs)
D. Lingual arch
E. Elastic bands

18. The rate of tooth movement is most influenced by:
A. Force magnitude
B. Moment ratio
C. Wire material
D. Bracket type
E. Patient age

19. In a two-tooth system, equal and opposite moments result in:
A. Translation of both
B. Rotation of both
C. Tipping of one
D. No movement
E. Intrusion

20. The center of resistance for a group of teeth, like anterior segment, is located:
A. At the incisor bracket
B. Posterior to the canines
C. At the molar
D. Variable based on roots
E. At the arch center

21. Light continuous forces in orthodontics are preferred because they:
A. Cause rapid movement
B. Minimize hyalinization
C. Increase tipping
D. Reduce anchorage
E. Enhance rotation

22. In loop mechanics, a vertical loop primarily provides:
A. Horizontal force
B. Vertical force
C. Moment
D. Couple
E. Intrusion

23. The force decay in elastomeric chains is due to:
A. Stretching
B. Relaxation
C. Heat
D. Saliva exposure
E. All of the above

24. To correct a deep bite, which movement is primarily used?
A. Extrusion of anteriors
B. Intrusion of anteriors
C. Tipping of posteriors
D. Bodily movement of molars
E. Rotation of incisors

25. In biomechanics, the equivalent force system at the center of resistance includes:
A. Force only
B. Moment only
C. Force and moment
D. Couple only
E. No force

26. Nickel-titanium wires are used for initial alignment due to their:
A. High stiffness
B. Shape memory
C. Low cost
D. High strength
E. Brittleness

27. The optimal force for bodily movement of a canine is approximately:
A. 50 grams
B. 100 grams
C. 150 grams
D. 200 grams
E. 250 grams

28. In a segmented arch technique, what controls the type of movement?
A. Wire size
B. Loop design
C. Anchorage unit
D. Force application point
E. All of the above

29. Hyalinization in PDL occurs with:
A. Light forces
B. Heavy forces
C. Continuous forces
D. Intermittent forces
E. No forces

30. The moment-to-force ratio for controlled tipping is around:
A. 1:1 to 5:1
B. 5:1 to 8:1
C. 8:1 to 10:1
D. 10:1 to 12:1
E. Above 12:1

31. In orthodontic extrusion, the force should pass:
A. Through the center of resistance
B. Lingual to it
C. Buccal to it
D. Apical to it
E. Coronal to it

32. Friction in sliding mechanics is reduced by:
A. Larger wires
B. Self-ligating brackets
C. Heavier forces
D. Angulated brackets
E. Elastic modules

33. The biology of tooth movement involves:
A. Osteoblasts on tension side
B. Osteoclasts on compression side
C. Both A and B
D. Reversal lines
E. All of the above

34. In a utility arch, the primary function is:
A. Intrusion
B. Extrusion
C. Tipping
D. Rotation
E. Torque

35. The center of rotation for pure rotation is:
A. At infinity
B. At the center of resistance
C. At the bracket
D. At the apex
E. Variable

36. Increasing the wire stiffness affects the moment by:
A. Increasing it
B. Decreasing it
C. No effect
D. Depending on span
E. Reducing force

37. In space closure, reciprocal anchorage leads to:
A. Movement of both units
B. No movement
C. Only anterior movement
D. Only posterior movement
E. Tipping only

38. The pressure-tension theory explains:
A. Bone remodeling
B. Tooth eruption
C. Anchorage loss
D. Force decay
E. Wire deflection

39. In miniscrew implants, the primary stability comes from:
A. Osseointegration
B. Mechanical interlock
C. Bone density
D. Screw design
E. All of the above

40. The force for rotation correction of a tooth is typically:
A. 10-20 grams
B. 30-60 grams
C. 70-100 grams
D. 150 grams
E. 200 grams

41. In a cantilever system, the force application creates:
A. Pure force
B. Pure moment
C. Force and moment
D. Couple
E. Translation

42. The lag time in tooth movement is due to:
A. Hyalinization removal
B. Force application
C. Wire activation
D. Patient compliance
E. Appliance type

43. Superelastic wires provide:
A. Constant force
B. Increasing force
C. Decreasing force
D. Variable moment
E. No force

44. In torque control, the play between wire and bracket affects:
A. Force level
B. Moment expression
C. Tipping
D. Rotation
E. Intrusion

45. Group A anchorage requires:
A. Minimal posterior movement
B. Maximum anterior movement
C. Equal movement
D. No movement
E. Tipping allowed

46. The piezoelectric effect in bone remodeling is related to:
A. Electric signals from deformation
B. Chemical signals
C. Hormonal influence
D. Vascular changes
E. Cellular apoptosis

47. In a reverse curve of Spee wire, the effect on molars is:
A. Intrusion
B. Extrusion
C. Tipping
D. Torque
E. Rotation

48. The optimal duration for orthodontic force application is:
A. Continuous
B. Intermittent
C. 24 hours
D. Pulsatile
E. Variable

49. In biomechanics, the determinant plane is used for:
A. Force analysis
B. Moment calculation
C. 3D movement prediction
D. Anchorage planning
E. Wire selection

50. Rapid tooth movement can lead to:
A. Root resorption
B. Bone loss
C. PDL damage
D. All of the above
E. No issues