Mandibular Retroguathism Question And Answers

Miscellaneous Short Essays

Question 1. Mandibular retroguathism.
Answer.

• Refers to more backward placement of jaw.

Features of retrognathism:

• Facial profile – convex
• Facial divergence – Posterior divergent
• Anteroposterior relation – Class 2
• Mento labial sulcus – Deep
• Hyperactive mentalis activity
• Reduced nasolabial angle

Treatment of retrognathism:

• In growing patients – Myofunctional therapy Ex. Activator, FR2
• In non-growing patients
  • Orthodontic camouflage – Extraction of 1st premolars
  • Mandibular advancement

Question 2. Causes of Canine impaction.
Answer.

Question 3. Mechanism of Bone Growth.
Answer.

Bone Deposition and resorption

• Together with bone deposition and resorption is called bone remodeling

Effects of bone deposition and resorption:

• Change in size
• Change in shape
• Change in proportion
• Change in bone relationship with adjacent structures

Cortical Drift

• Movement of bone occurs towards bone deposition called cortical drift
• If bone deposition and resorption are equal
• Thickness of bone remains, constant
• If bone deposition is more than resorption
• The thickness of bone is more toward the deposition

Displacement

• Movement of whole bone as a unit

Primary displacement:

• Displacement of bone as a result of its own growth

Secondary displacement:

• Displacement of bone as a result of growth of adjacent bone

Question 4. Causes of Root resorption.
Answer.

Question 5. Envelope of Discrepancy.
Answer.

• It helps in treatment planning
• The choice of treatment depends on the movement of the teeth required
• By orthodontic (fixed mechanotherapy) the tooth can be moved only at a specific distance

Read And Learn More: Orthodontics Short And Long Essay Question And Answers

• If the movement of teeth beyond this limit is required, orthopedic/functional appliances can be used
• Beyond this limit, the treatment of choice is orthognathic surgery

Question 6. Self-correcting Anomalies/Transient Malocclusions.
Answer.

Miscellaneous Short Questions And Answers

Question 1. Apertognathia.
Answer.

It is a condition in which there is space between upper and lower teeth when some teeth are in contact at one/more points

Question 2. Growth site and Growth center.
Answer.

Growth site:

• These are growth fields that have a special significance in the growth of a particular bone
• Posses intrinsic growing potential
  Example. Condyle, maxillary tuberosity

Growth Centres:

• These are growth sites that control the overall growth of bone
• Have growth potential
  Example. Epiphyseal plates of long bones

Question 3. Cranial Base Flexure.
Answer.

• During the embryonic phase, the cranial base is flexed between the pituitary fossa and sphenoccipital junction
• It is accompanied by developing brain stem

Cranial Base Flexure Results

• Downward placement of foramen magnum
• Aids in increased neurocranial capacity
• Downward displacement of the face
  Age: 10th week of IU life, Angle – 65th

Question 4. Carpal Index.
Answer.

• One of the skeletal maturity indicator
• Used as a part of hand wrist
• Carpals – consist of eight small bones arranged in

Proximal Row

• Scaphoid
• Triquetral
• Lunate
• Pisiform

Distal row

• Trapezium
• Trapezoid
• capitate
• Humate
• These bones show specific patterns of appearance, ossification, and union
• These are compared with standards

Question 5. Torquing Auxillaries.
Answer.

Torquing Auxillarie Springs:

• Made of stainless steel /Ni – titanium
• Force exerted is directly proportional to the diameter and modulus of elasticity of the material of the wire
• Stainless steel exerts greater force

Question 6. Sterilization in Orthodontics.
Answer.

Definition: Defined as the destruction of all life forms

Types of Instruments:

• Critical – Penetrate the mucosa
• Semi-critical – Touches mucosa but does not penetrate
• Least critical – Surfaces touched during treatment

Instruments Requiring Sterilization:

• Mirrors
• Explorers
• Banding and bonding instruments
• Bands
• Pillers
• Ligature directors

Question 7. Growth Trends.
Answer.

By overlapping consequent cephalograms Tweed, designed a pattern of growth called “Growth trends”

Groups

Type A

• Simultaneous growth of maxilla and mandible
• 25% of case
• ANB angle unchanged

Type A subdivision

• Protruding maxilla
• ANB angle increased

Type B

• Increase in maxillary growth

Type B subdivision

• ANB angle large
• Unfavorable

Type C

• Increased growth of the mandible
• Decreased ANB angle

Type C Subdivision

• Mandibular incisors touches lingual surfaces of maxillary incisors

Question 8. Growth Curve.
Answer.

• Indicates the degree of difference between two growing individuals in all four planes including the time factor
• As everyone does not have the same growth pattern, deviation from normal growth pattern cannot be diagnosed
• Thus the growth of such individuals is compared with a standard growth chart

Question 9. Fontanelles.
Answer.

• They bridge the gap between bones that limit them.
• Made up of durameter, primitive periosteum and aponeurosis

Frontanelles Importance:

• Indicates brain development
• A depressed level indicates dehydration
• Increased level indicates increased intracranial pressure

Question 10. Safety valve mechanism.
Answer.

• Increase in inter-canine width is one of the important factor in overcoming incisal liability
• At the age of 12, maxillary anterior prolines such that inter-canine width increase

Significance of safety value mechanism:

• This increase in maxillary inter canine width hinders the forward growth of the mandible
• This increase in width behaves like it holds the forwardly growing mandible

Question 11. Curve of Spee.
Answer.

• It is antero-posterior curve of occlusion
• It begins from the tip of lower canine to the cusp tips of bicuspids and molars upto the condyle

Significance of curve of Spee:

• Normal value – 1.5 – 2mm
• If the curve is extended, it forms a circle of about 4 diameter
• It represent the axial alignment of lower teeth
• It requires a gradual progressive increased mesial tilting of teeth towards the molar

Question 12. Anterior bite plane and its mode of action.
Answer.

Uses of anterior bite plane: For treatment of deep bite

Mode of action:

• Consist of the flat ledge of acrylic behind the upper anterior
• When the patient bites the mandibular incisors contact the bite plane, thus dis occlude the posterior due to which they are free to erupt

Components of anterior bite plane:

• Adam’s clasp on molar – As a retainer
• Labial bow – Counter any forward component of force on upper anterior

Question 13. Orbital law of canine.
Answer.

• It is used in Simon’s classification
• Orbital plane perpendicular to Frankfort horizontal plane is used
• This plane is dropped down from the bony orbital margin directly under the pupil of the eye
• According to Simon, this plane should pass through the distal third of the upper canine
• This is known as “Simon’s law of canine “or” Orbital law of canine”

Orbital law of canine significance:

• It is used to describe malocclusion in a sagittal plane
• When the dental arch is farther from the orbital plane it is called protraction
• When the dental arch is closer then it is called retraction