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Cephalometrics Important Notes

• Landmarks

• Planes

• Angle of convexity

• Angles

• Wit’s analysis
  • It is a measure of the extent to which the maxilla and mandible are related to each other in antero-posterior direction
  • It is used when the ANB angle is not reliable
• Different analysis

• Tweed’s analysis
  • Forms a triangle by use of three planes

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

Cephalometrics Long Essays

Question 1. What are diagnostic aids? Describe cephalometrics and its uses.
Answer.

Diagnostic Aids

Comprehensive orthodontic diagnosis is established by the use of clinical implements called diagnostic aids

Cephalometrics:

• Introduced by Broadbent in USA and Hofrath in Germany in 1931
• It describes the analysis and measurements made on the cephalometric radiographs

Types Of Cephalometrics:

• Lateral cephalogram: Provides a lateral view of the skull
• Frontal cephalogram: Provides an antero-posterior view of the skull

Technical Aspects:

• Apparatus – X-ray source
  • Cephalostat – two ear rods
  • Orbital pointer
  • Forehead clamp

Landmarks:

• Used for quantitative analysis and measurements

Types Of Landmarks:

• Anatomic landmarks: Represent actual anatomic structures of the skull
• Derived landmarks: Obtained from anatomic structures

Requirements Of Land Marks:

• Easy to view
• Reproducible
• Provide valid measurements

Examples Of Landmarks:

• Nasion
• Orbitale
• Porion
• Sella

Lines And Planes:

• Obtained by connecting two landmarks

Types Of Lines And Planes:

• Horizontal Planes
  • Sella-Nasion Plane: Connecting sella and nasion
  • Frankfort Horizontal Plane: Connecting orbitale and porion
  • Occlusal Plane: Connecting occlusal surfaces of posterior to anteriors
  • Palatal Plane: Connecting ANS and PNS
  • Mandibular Plane:
    • Tangent to lower border of mandible – Tweed
    • The line connecting gonion & gnathion – Steiner
    • The line connecting gonion & mention – Down’s

• Basion – Nasion Plane: Connecting Basion and Nasion
• Bolton’s Plane: Connecting Bolton’s Point and Nation

Vertical Plane

• A.Pog line: Point A to Pogonion
• Facial Plane: Nasion to pogonion
• Facial axis: Ptm point to gnathion
• E.Plane: Soft tissue nose to the soft tissue of the chin

Cephalometrics Uses:

• For diagnosis
• Study of dental and soft tissue structures
• Classify skeletal and dental abnormalities
• Assess facial type
• For treatment planning
• For presuming the changes
• For predicting growth-related changes
• For research work

Cephalometrics Short Essays

Question 1. Cephalogram.
Answer.

Cephalogram

• Cephalogram is a cephalometric radiography introduced by Holly Broadbent and Herbert Hofrath in 1931

Types Of Cephalogram:

• Lateral cephalogram
  • This provides a lateral view of the skull
• Frontal cephalogram
  • Provides an antero-posterior view of skull

Cephalogram Uses:

• For diagnosis
• Study of dental and soft tissue structures
• Classify skeletal and dental abnormalities
• Assess facial type
• For treatment planning
• For presuming the changes
• For predicting growth-related changes
• For research work

Cephalogram Limitations:

• Exposure to a patient is harmful
• Provides two three-dimensional views of three-dimensional structures
• Not well standardized
• Absence of anatomic references
• Has limited relevance

Question 2. Uses of Cephalometrics
Answer.

Uses of Cephalometrics

• For diagnosis
• Study of dental and soft tissue structures
• Classify skeletal and dental abnormalities
• Assess facial type
• For treatment planning
• For presuming the changes
• For predicting growth-related changes
• For research work

Question 3. Cephalostat.
Answer.

Cephalostat

• It is head holding device

• Position: The distance between the X-ray source and the mid-sagittal plane of the patient is 5 feet

Uses Of Cephalostat:

• For standardizing radiography
• Comparing serial radiographs

Question 4. Steiner Analysis.
Answer.

Parameter:

Skeletal

• SNA angle:
  • SN plane and line joining nasion and point A – 82°
  • Increased – Class 2; Decreased – Class 3
• SNB angle:
  • Between SN plane and the line joining nasion and point B – 80°
  • Increased – Class 3; Decreased – Class 2
• ANB angle:
  • Between the line joining Maison and point A and Nation and point B – 2°
  • Increased – Skeletal Class 2; Decreased – Skeletal Class 3
• Mandibular Plane angle:
  • Between SN plane and mandibular plane – 32°
  • Low angle – Horizontal grower; High angle – vertical grower
• Occlusal plane angle:
  • Between occlusal plane and SN plane – 14.5°
  • Indicates growth pattern of individual

Dental:

• Upper Incisor to N-A:
  • Between the long axis of the upper incisor and nasion to point A – 22°
  • Increased – proclination of upper incisors
• Upper Incisor to N-A:
  • Linear measurement between labial surface of upper incisor and line joining nasion to point A – 4mm
• Lower Incisor to N-B:
  • Between long axis of lower incisor and nasion to point B – 25°
  • Increased – Proclined lower incisor
• Lower Incisor to N-B:
  • The linear distance between the labial surface of the lower central incisor and the line joining nasion to point B – 4mm
  • 131°
• Inter-incisor angle:
  • Between the long axis of the upper and lower central incisor
  • Increased – Class 2 div 2, Decreased – Class 2 div 1, Class 1

Soft Tissue analysis

According to Steiner the lips in a well-balanced face should touch a line extending from the soft tissue of the chin to the middle of the ‘S’ formed by the lower border of the nose

• Protrusive – Lips beyond this line – Convex profile
• Retrusive – Lips behind this line – Concave profile

Question 5. Down’s Analysis.
Answer.

Down’s Analysis

Dental

Question 6. Visual treatment objective (VTO).
Answer.

Types Of Visual Treatment Objectives

Clinical VTO:

• It is an aid to decide the type of appliance in skeletal class 2 malocclusion
• The procedure consists of asking the patient to bring the mandible to an edge-to-edge bite relation and note the changes in appearance of the patient at two levels
  • Edge-to-edge relation
  • Midway between existing occlusion and edge-to-edge position
• Interpretation:
• If the profile worsens at the edge-to-edge position, the fault lies in the maxilla
• If the profile improves at the edge-to-edge position, the fault lies in the mandible
• If the profile improves at the midway position, there is a fault in both the maxilla and mandible

Cephalometric VTO:

• It is like a visual plan to predict the normal growth of a patient and anticipate the effects of the treatment for an individual patient
• It permits the development of alternative treatment plans and to set goals in advance for the treatment

Question 7. Tweed’s triangle.
Answer.

Tweed’s triangle

Question 8. Cephalometrics uses, advantages, and disadvantages.
Answer.

Uses Of Cephalometrics:

• For diagnosis
• Study of dental and soft tissue structures
• Classify skeletal and dental abnormalities
• Assess facial type
• For treatment planning
• For presuming the changes
• For predicting growth-related changes
• For research work

Advantages Of Cephalometrics:

• Tangible records that are relatively permanent
• Nondestructive and noninvasive
• Easy to store, transport, and reproduce
• Yield accurate information on the spatial relationship between surface and deep structures
• Low physiological cost

Disadvantages Of Cephalometrics:

• It gives a two-dimensional view of a three-dimensional object
• There can be errors while developing which can limit measuring accuracy to 0.5mm
• Needs a special X-ray apparatus with precise calibration
• Needs complex patient positioning arrays to avoid errors

Cephalometrics Short Questions And Answers

Question 1. Frankfort plane.
Answer.

Frankfort plane

Connects lowest point of orbit and superior border of external auditory meatus i.e. orbitale to portion

Significance Of Frankfort plane: Important in Down’s analysis

• Used in both dental and skeletal parameters

Question 2. Cephalostat.
Answer.

Cephalostat

It is head holding device

Position: The distance between the X-ray source the and mid-sagittal plane of the patient is 5 feet

Question 3. SNB angle.
Answer.

SNB angle

Used in Steiner’s Analysis

Angle: Between SN plane and the line joining nasion and point B

Importance: Indicates relative antero-posterior positioning of the mandible about the cranial base

Value: 80°

Changes:

• Increased – Prognathic mandible [Class 3]
• Decreased – Retrognathic mandible [Class 2]

Question 4. Registration Point.
Answer.

Registration Point

• It is derived from landmarks obtained on cephalogram
• It is the midpoint of the perpendicular drawn from the center of Sella Tursica to the Bolton plane

Question 5. Mandibular Plane.
Answer.

Mandibular Plane

Based on different analysis. There are several mandibular planes

Common are:

• Tangent to lower border of mandible – Tweed
• Line connecting gonion and gnathion – Steiner
• The line connecting Gonion and mention – Down’s

Question 6. SNA angle.
Answer.

SNA angle

Used in Steiner’s Analysis

Angle: Between SN plane and the line joining nasion and point A

Importance: Indicates relative antero-posterior positioning of the maxilla about the cranial base

Value: 82°

Changes:

• Increased – Prognathic maxilla [Class 2]
• Decreased – Retrognathic maxilla [Class 3]

Question 7. Occlusal Plane.
Answer.

Occlusal Plane

It is a denture plane

Extend: Occlusion of posterior to interiors

Significance Of Occlusal Plane:

• The angle formed between the occlusal plane and the SN plane is known as the occlusal plane angle
• It indicates the relation of the occlusal plane to the cranium and face
• It has a mean value of 14.5 degrees

Question 8. Cant of Occlusion.
Answer.

Cant of Occlusion

• Used in Down’s analysis
• The angle between the occlusal plane and the FH plane
• Value: 9.3°
• Range: 1.5 – 14°
• It measures the slope of the occlusal plane relative to the FH plane

Question 9. ANB angle.
Answer.

ANB angle

Used in Steiner’s analysis

Angle: Between line joining nasion to point A and nasion to point B

Significance Of ANB angle: Relative position of maxilla to the mandible

Value: 2°

Changes:

• Increase – Skeletal Class 2
• Decrease – Skeletal Class 3

Question 10. Point A.
Answer.

Point A

It is an anatomic landmark of cephalometric

• The deepest point in the midline between the anterior nasal spine and alveolar crest between two central incisors
• Synonym: Subspinale
• Line/Plane derived from it:
  • A.Pog line
  • A.B plane angle – Used in Down’s Analysis
  • The angle of convexity – Used in Down’s Analysis
  • SNA angle – Used in Steiner’s Analysis
  • ANB angle – Used in Steiner’s Analysis

Question 11. Key Ridge.
Answer.

Key Ridge

• It is an anatomic landmark of cephalometric
• It is the lowermost important point on the contour of the anterior wall of the infratemporal fossa
• In edentulous cases, it is useful in determining occlusion

Question 12. Y axis.
Answer.

Y-axis

Used in Down’s analysis

Synonym: Growth axis

Angle – Between sella – gnathion line and FH plane

Value: 59° [53-66°]

Variations Of the Y axis:

• Increased – Class 2
• Decreased – Class 3

Importance Of Y axis:

• Determines growth pattern
• Greater – Vertical growth
• Lesser – Horizontal growth

Question 13. Wit’s Appraisal.
Answer.

Significance Of Wits’s Apprasial: Measures relation of maxilla to mandible

Use: In nonreliable ANB cases

Obtained by:

Variation Of Wit’s Appraisal:

• Males – BO ahead of AO
• Females – BO coincides with AO
• Skeletal Class 2 – BO behind AO
• Skeletal Class 3 – BO ahead of AO

Question 14. FMA.
Answer.

Cephalometric FMA:

• FM – plane – extending from orbitale to prior
• Mandibular plane
• The angle formed between these two
• Value – 25°

Clinical FMA:

• The angle formed between the lower border of the mandate ble and Frankfort horizontal plane
• Normally intersect at the occipital region

Significance Of FMA:

• Indicates growth pattern
• If coincides
  • At occipital – Normal
  • Beyond occipital – Horizontal
  • Anterior to occipital – Vertical

Question 15. Cephalogram
Answer.

Cephalogram

• Cephalogram is a cephalometric radiography introduced by Holly Broadbent and Herbert Hofrath in 1931

Types Of Cephalogram:

• Lateral cephalogram – provides a lateral view of the skull
• Frontal cephalogram – provides an anteroposterior view of the skull

Cephalogram Uses:

For diagnosis:

• Study of dental and soft tissue structures
• Classify skeletal and dental abnormalities
• Assess facial type
• For treatment planning
• For presuming the changes
• For predicting growth-related changes
• For research work

Question 16. Tweed’s triangle.
Answer.

Formed by:

• Frankfort mandibular plane angle [FMPA] – 25°
  • Angle by the intersection of the FH plane and mandibular plane
• Incisor mandibular plane angle [IMPA] – 90°
  • The angle formed by the intersection of the long axis of lower incisor and mandibular plane
• Frankfort mandibular incisor angle [FMIA] – 65°
  • The angle formed by the long axis of lower incisor and FH plane

Cephalometrics Viva Voce

• Y axis indicates the direction of the growth pattern of the mandible
• Richard A. Riedel introduced the ANB angle
• Cephalometric tracing is made on the frosted surface of an acetate tracing sheet
• E plane is also called the aesthetic plane
• Normal facial angle – 82-95°
• The normal value of the Y axis in Down’s analysis – 53-66°
• The normal value of cant of occlusion – 1.5 – 14°
• Normal value of interincisal angle – 130-150°
• The normal mandibular plane angle in Steiner’s analysis is 29°
• Decreased SNB angle indicates mandibular retrognathism
• Decreased ANB angle indicates skeletal Class 3
• The decreased facial angle indicates skeletal class 2
• A decreased angle of convexity indicates the prognathic profile
• Increased AB plane angle indicates class 3
• Increased upper incisor to NA angle indicates proclined upper incisors
• Increased lower incisor to NB angle indicates proclined lower incisors
• The facial angle indicates antero-posterior positioning of the mandible to the upper face
• AB plane angle signifies the maxilla-mandibular relationship to the facial plane’

Orthodontics Lab Procedures Definitions

• Soldering
  • It is a process of joining metals by the use of a filler metal that has a lower fusion temperature than that of the metals being joined.
• Welding
  • Involves the joining of two metals without introducing a third metal.

Orthodontics Lab Procedures Important Notes

• Types of solders
  • Investment soldering
  • Freehand soldering
• Composition of flux
  • Borax glass – 55%
  • Boric acid – 35%
  • Silica – 10%
• Gases used for soldering.
  • Gas air/oxygen torch flame
  • Hydrogen
  • Natural gas
  • Acetylene
  • Propane

Orthodontics Lab Procedures Short Essays

Question 1. Soldering and Welding.
Answer.

Soldering: It is a process of joining metals by the use of a filler metal that has a lower fusion temperature than that of the metals being joined.

Types of soldering:

Investment soldering:

Indication: Presence of large contact area between metals

• In need of precision
  Procedure: By embedding metals in investment

Freehand soldering:

• Indication: Common orthodontic procedures
• Procedures: Soldering by holding metals precisely

Steps of freehand soldering:

• Clean the surfaces
• Assemble the parts
• Select proper solder and flux
• Select proper joint
• Flux application
• Application of solder
• Quenching

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

Indications of freehand soldering:

• Join parts of appliances
• Fastens attachments to bands

Welding: Involves joining of two metals without introducing a third metal

Welding Procedure:

• Selection of electrode
• Placement of metals between 2 electrodes
• Maintain pressure on it
• Switch on electrode
• Keep it for sometime

Indications of welding:

• For banding
• For brackets and molars tubes

Question 2. Shape Memory Alloy – Nickel titanium alloy is a shape memory alloy.
Answer.

Synonym: Nitinol (Nickel Titanium Naval Ordinance Laboratory)

Inventor: William R. Buchler

Introduced by: Andersen in 1971

Properties of shape memory alloy:

• Super elasticity
• Shape memory
• High working range
• Low stiffness

Advantages of shape memory alloy: Procedure low and more constant force on teeth

Disadvantages of shape memory alloy:

• Cannot be bent
• Cannot be soldered/welded

Orthodontics Lab Procedures Short Questions And Answers

Question 1. Solder and Flux.
Answer.

Solder: Alloys used as filler metal between two metals

Properties of solder:

• Resist tarnish and corrosion
• Low fusion temperature
• Free-flowing
• Similar strength as the metals to be joined
• Colour similar to metals to be joined
• Ex – Gold, silver, copper, zinc, tin and nickel

Flux: means flowing

• Important for good solder joint

Uses of flux:

• Removal of oxide coating of solder
• Dissolves impurities
• Prevents oxidation
• Reduces melting point

Flux Composition:

• Borax glass – 55%
• Boric acid – 35%
• Silica – 10%

Question 2. Antiflux.
Answer.

Flux:

• Means flowing
• Important for good solder joint

Uses of Flux:

• Removal of oxide coating of solder
• Dissolves impurities
• Prevents oxidation
• Reduces melting point

 Composition of Flux:

• Borax glass – 55%
• Boric acid – 35%
• Silica – 10%

Antiflux:

• Confines flow of molten solder
• Ex. Lead pencil markings
  • Graphite lines
  • Iron rouge

Question 3. Gases used for soldering.
Answer.

• Gas air/oxygen torch flame
• Hydrogen
• Natural gas
• Acetylene
• Propane

Question 4. Sensitization and stabilization of stainless steel.
Answer.

Sensitization: At 400-900 c, stainless steel resists corrosion and tarnish

• At lower temperatures, carbon reacts with the surface granules and forms chromium iron carbide causing tarnish and corrosion
• This can be prevented by decreasing carbon content or by cold working of stainless steel

Stabilization:

• The process to prevent sensitization
• For it, two/more metals are added, for example, titanium, niobium

Question 5. Irreversible Hydrocolloids (Alginate).
Answer.

Advantages of Irreversible Hydrocolloids:

• Easy to manipulate
• Comfortable
• Inexpensive
• Pleasant taste
• Hydrophilic
• Biocompatible

Disadvantages of Irreversible Hydrocolloids:

• Tears easily, and require immediate pouring
• Incompatible with epoxy resin

Composition of Irreversible Hydrocollids:

• Potassium Alginate
• Calcium sulfate dehydrate
• Potassium sulfate
• Diatomaceous earth
• Sodium phosphate
• Glycol
• Pigments
• Sodium silicofluoride

Orthodontics Lab Procedures Viva Voce

• Gold foil filling is the best example of cold welding
• Welding is a process of joining two metals directly under pressure
• The space provided between the metals to be joined is 0.5 mm
• Borax glass is the main component of dental flux
• The oxidized layer in the metallic surfaces to be joined is removed by antireflux
• Nickel in dental solder gives a white color to the solder
• The copper component in solder gives the yellow color
• Fusion temperature exceeding 150 degrees is used for brazing

Surgical Orthodontics Important Notes

• Pericision/circumferential suprarenal fibrotomy
  • Performed in case of rotations
  • In it, gingival fibres are incised to prevent relapse
  • Performed under LA with several 11-knife

Surgical Orthodontics Long Essays

Question 1. Classify surgical orthodontics. Discuss minor surgical orthodontic procedures.
Answer.

Surgical Orthodontic Procedure

Minor Procedure:

• Extractions
  • Therapeutic
  • Serial
  • Carious teeth
  • Malformed teeth
  • Impacted teeth
  • Supernumerary teeth
• Surgical uncovering of teeth
• Frenectomy
• Pericision
• Transplantation of teeth
• Corticotomy

Major procedures:

• Orthodontic surgeries
• Cosmetic surgeries
• Surgical corrections of clefts
• Surgical RME

Minor Surgical Procedures:

Extraction:

• Therapeutic extraction
  • To gain space
  • Should be atraumatic
• Surgical extraction
  • Removal of some deciduous teeth followed by specific permanent
  • Done during mixed dentition period
  • In severe arch-length deficient
• Supernumerary teeth
  • It leads to malocclusion or development of cyst
  • Thus, needs to be extracted

Surgical Uncovering of Impacted Teeth:

• Impacted teeth cause deflection of teeth
• Common – Maxillary permanent canine
  • Cause – Arch length deficiency, Mucosal/bony barriers
  • These barriers are removed to allow the eruption of impacted teeth

Frenectomy:

• Abnormal labial frenum causes mid-line diastema
• Frenum is excised along with attached fibrous tissue
• Undermining of the mucosa of the lip is done

Corticotomy:

Indication of Corticotomy:

• Proclination with spacing

The procedure of Corticotomy:

Precision:

Synonym – Circumferential Supra-crystal Fibrotomy [CSF]

• It is the procedure to counter the relapse tendency of stretched gingival fibres

Cause of Relapse: Failure of adaptation of transeptal and alveolar crystal group of gingival fibres to the new tooth position

The procedure of Relapse:

Surgical Orthodontics Short Essays

Question 1. Genioplasty.
Answer.

• Used as an adjunctive.

Types of Genioplasty:

Augmentation genioplasty:

• Horizontal osteotomy cut given
• Mobilize the segment and fix

Reduction genioplasty:

• Horizontal osteotomy cut given
• Setback fragment and fix it

Straightening genioplasty:

• Horizontal osteotomy cut given
• Shift it laterally and fix it

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

Lengthening genioplasty:

• Horizontal osteotomy cut given
• Shift fragment inferiorly
• Sandwich grafts in between them

Question 2. Orthognathic Surgery in Maxilla.
Answer.

• Carried out along with orthodontic therapy to correct dentofacial deformities
• Involves fracturing of facial skeletal parts and repositioning them as desired

Steps of Orthognathic Surgery:

• Diagnosis
• Pre-surgical orthodontics
• Mock surgery
• Surgery and stabilization
• Post-surgical orthodontics

Surgical Orthodontics Short Questions And Answers

Question 1. Frenectomy.
Answer.

• Abnormal labial frenum causes midline diastema
• Frenum is excised along with attached fibrous tissue
• Undermining of the mucosa of the lip is done

Question 2. Precision.
Answer.

• Synonym – Circumferential Supra-crystal Fibrotomy [CSF]
  • It is the procedure to counter the relapse tendency of stretched gingival fibres
• Cause of Relapse: Failure of adaptation of transeptal and alveolar crystal group of gingival fibres to the new tooth position

Procedure of Pericision:

Surgical Orthodontics Viva Voce

• Precision is done to prevent relapse of rotation of teeth.
• Precision involves surgical lysis of the gingival.

Retention And Relapse Definition

• Retention
  • Maintaining newly moved teeth in position, long enough to aid in stabilizing their correction.
• Relapse
  • It is the loss of any correction achieved by orthodontic treatment.

Retention And Relapse Important Notes

Types of retention:

• Limited retention:
  • Class 1 non-extraction
  • Deep bites
  • Class 1, Class 2 Div. 1 and Div. 2 extraction
• Natural retention:
  • Anterior cross bites
  • Serial extraction
  • Highly placed canines
  • Posterior crossbite
• Permanent retention:
  • Midline diastemas
  • Rotation
  • Class 2 div.2 deep bites
  • Abnormal musculature
  • Cleft palate patients

Types of retainers:

• Removable:
  • Hawely’s appliance
  • Begg retainers
  • Clip on retainers
  • Wrap-around
  • Kesling tooth position
  • Invisible retainers
• Fixed:
  • Fixed appliance
  • Banded canine to canine
  • Bonded lingual
  • Band and spur retainer

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

Causes of relapse:

• Periodontal ligament traction
• Growth related changes
• Bone adaptation
• Muscular forces
• Failure to eliminate the original cause
• Role of the third molar
• Role of occlusion

Retention And Relapse Long Essays

Question 1. Enumerate theories of retention. Add a note on causes of relapse.
Answer.

Retention

Definition of retention: By Moyers

• Maintaining newly moved teeth in position, long enough to aid in stabilizing their correction.

Theorems: 9 theorems by Riedel and 10th Moyers

• Moved teeth return to their former position
• Elimination of cause prevents relapse
• Malocclusion should be over-corrected
• Proper occlusion should be achieved
• Bone and adjacent tissues should be provided time to readapt around moved teeth
• Lower incisors must be placed upright
• Corrections carried out during growth periods are less likely to relapse
• Farther the teeth have been moved, the lesser the risk of relapse
• Arch form, particularly mandibular, cannot be permanently altered by appliance therapy
• Many treated malocclusions require permanent retaining devices

Types of retention

Limited retention:

• Class 1 non-extraction
• Deep bites
• Class 1, Class 2 Div. 1 and Div. 2 extraction

Natural retention:

• Anterior crossbite
• Serial extraction
• Highly placed canines
• Posterior crossbite

Permanent retention:

• Midline diastema
• Rotation
• Class 2 div.2 deep bites
• Abnormal musculature
• Cleft palate patients

Retainers: Passive appliances that help in maintaining and stabilizing the position of teeth long enough to permit readaptation of supporting structures

Types of retainers

• Removable retainers
  • Hawely’s appliance
  • Begg retainer
  • Clip on retainer
  • Wrap-around
  • Kesling tooth position
  • Invisible retainer

• Fixed retainers
  • Fixed appliance
  • Banded canine to canine
  • Bonded lingual
  • Band and spur retainer

Relapse: It is the loss of any correction achieved by orthodontic treatment

Causes of Relapse:

• Periodontal ligament traction:
  • Due to orthodontic tooth movement, PDL and gingival fibres are stretched
  • They readapt to the newly moved teeth
  • Different fibres require different periods for it
  • Principle fibres – 4 weeks
  • Gingival fibres – 40 weeks
  • If not provided sufficient time, leads to relapse
• Growth-related changes:
  • Due to the continuation of abnormal growth pattern
• Bone adaptation:
  • Normal, bony trabeculae are arranged perpendicular to the long axis of teeth
  • During orthodontic treatment, arranged parallel to the long axis of teeth
  • After treatment returns to original position
• Muscular forces:
  • Abnormal muscle balance
• Failure to eliminate the original cause:
  • The cause should be properly diagnosed and a treatment plan must be done accordingly
• Role of the third molar:
  • Eruption time – 18-21 years i.e. usually after completion of orthodontic treatment
  • Produces pressure
  • Results in crowding recurrence
• Role of occlusion:
  • Failure to eliminate habits like bruxism
  • Failure to achieve centric occlusion

Retention And Relapse Short Essays

Question 1. Define retention, and explain schools of retention.
Answer.

Retention: Maintaining newly moved teeth in position long enough to aid in stabilizing their correction – By Moyers

Schools Of Retention:

• Occlusion School – By Kingsley
  • Proper occlusion is important as it safeguards the stability in the new position of patients
• Apical base school:
  • By Alex Lundstorm, Mc.Cauley and Nance
    • By Alex Lundstorm – Suggest apical base as an important factor in the correction of malocclusions
    • Mc. Cauley – Added inter-canine and intermolar width should be maintained
    • Nance – Noted arch length cannot be permanently increased to a major extent.
• Mandibular Incisor School – Grieves and Tweed
  • Stability increases if mandibular incisors are placed upright
• Musculature School – Rojer
  • Functional muscle is necessary for post-treatment stability.

Question 2. Permanent retention.
Answer.

Conditions of Permanent Retention:

• Midline diastema
• Severe rotations
• Generalized spacing
• Patients with abnormal musculature
• Arch expansion
• Cleft palate patients
• Class 2 div.2 deep bite

Appliances Used:

Retainers: Passive appliances that help in maintaining and stabilizing the position of teeth long enough to permit readaptation of supporting structures

Types of Retainers:

Removable Retainers

Removed and reinserted at patient’s will

• Hawely’s Appliance – By Charles Hawley
  • Consists of – short labial bow, Adam’s clasps on molars

        Modifications of Hawely’s appliance:

• • Long labial bow – for space closure distal to the canine
  • Fitted labial bow – Excellent retention
  • Soldered labial bow
  • Anterior bite plane – for deep bite

       Advantages of Hawley’s appliance:

• • Simple and easy to fabricate
  • Comfortable to patient
  • Acceptable

Begg retainer – By P.R. Begg

Consists Of Begg retainer:

• Labial wire till last erupted molar, curves around it
• Spans palate – Acrylic portion

Advantage of Begg retainer: Eliminate risk of spacing between canine and premolar

Clip on retainer:

• Labial wire covering incisors and canine then wrapped around same teeth lingually

Wrap around retainer:

• Wire wrapped around all erupted teeth labially as well as lingually

Keeping tooth position – By H.D. Kesling

• Thermoplastic rubber covering the clinical crown of upper and lower teeth
• This leads to difficulty in speech and TMJ problems

Invisible retainers: Covers clinical crowns and part of the gingiva on a transparent thermoplastic sheet

Fixed retainers

• Fixed appliance itself
• Banded canine-to-canine retainer
  • Thicker wire over lingual surface soldered on canine bands
• Bonded lingual retainers
  • Stainless steel/Etglioy wire is etched and bonded lingually over interiors
• Band and spur
  • For rotation
  • The moved tooth is bands and spur are soldered over it.

Retention And Relapse Short Questions And Answers

Question 1. Define retention.
Answer.

By Moyers

• Maintaining newly moved teeth in position, long enough to aid in stabilizing their correction

Question 2. Define relapse.
Answer.

• It is the loss of any correction achieved by orthodontic treatment

Question 3. Causes of relapse.
Answer.

• Periodontal ligament traction
• Due to orthodontic tooth movement, PDL and gingival fibres are stretched
• They readapt to the newly moved teeth
• Different fibres require different periods for it
• Principle fibres – 4 weeks
• Gingival fibres – 40 weeks
• If not provided sufficient time, leads to relapse

Growth-related changes:

• Due to the continuation of abnormal growth pattern

Bone adaptation:

• Normal, bony trabeculae are arranged perpendicular to the long axis of teeth
• During orthodontic treatment, arranged parallel to the long axis of teeth
• After treatment returns to the original position

Muscular forces:

• Abnormal muscle balance

Failure to eliminate the original cause:

• The cause should be properly diagnosed and a treatment plan must be done accordingly

Role of the third molar:

• Eruption time – 18-21 years i.e. usually after completion of orthodontic treatment
• Procedures pressure
• Results in crowding recurrence

Role of occlusion:

• Failure to eliminate habits like bruxism
• Failure to achieve centric occlusion

Question 4. Conditions where retention is not required/Natural retention.
Answer.

• Anterior crossbite
• Serial extraction
• Highly placed canines
• Posterior crossbite

Question 5. Permanent retention.
Answer.

• Midline diastema
• Rotation
• Class 2 div.2 deep bites
• Abnormal musculature
• Left palate patients

Retention And Relapse Viva Voce

• According to Alex Lundstorm, the apical base is the key to retention
• According to Grieves and Tweed, mandibular incisors are a key factor in retention
• Full-time retention after comprehensive orthodontic therapy is needed for 4-5 months
• Upper anterior crossbite correction with no adequate overbite requires retention of 3-6 months
• Opening of premolar space is a drawback of standard Hawley retainer
• Prevention of wedging effect on extraction site by Hawley retainer can be attempted by long labial bow
• Relapse is the loss of any correction achieved by orthodontic treatment

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

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

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
• 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