Model Analysis Orthodontics Question And Answers

Model Analysis Important Notes

  • Carey’s analysis

Orthodontics Model Analysis Carey's analysis

  • Bolton’s analysis
    • According to Bolton, tooth size is an important factor to be taken into consideration for diagnosis and there exists a ratio between mesio-distal widths of maxillary and mandibular teeth
    • Bolton’s overall ration is 91.3%
    • If overall ratio is less than 91.3%, it indicates maxillary tooth material excess
    • Bolton’s anterior tooth ratio is 77.2%
    • If anterior ratio is less than 77.2%, it indicates maxillary anterior excess
  • Tanaka Johnson analysis
    • This analysis does not require any radiographs or reference tables
    • The width of unerupted canines and premolars can be predicted based on width of mandibular incisors
    • Width of maxillary canine and premolars = 11 + 1/2 width of madibular incisors
    • Width of mandibular canine and premolars = 10.2 + 1/2 width of mandibular incisors
  • Various model analysis

Orthodontics Model Analysis Various Model Analysis

  • Requirements of various analysis

Orthodontics Model Analysis Various Analysis

Model Analysis Long Essays

Question 1. Classify diagnostic aids. Write briefly about Model analysis.
Answer.

Diagnostic Aids:

  • Essential Diagnostic aids
    • Case history
    • Clinical examination
    • Study models
    • Certain radiographs
    • Facial photographs
  • Supplemental diagnostic aids:
    • Specialized radiographs
    • Electromyographs
    • Hand wrist radiographs
    • Endocrines tests
    • Estimation of basal metabolic rates
    • Diagnostic set-up
    • Occlusograms

Model Analysis:

Involves study of maxillary and mandibular dental arches in all the three planes of space

  • Useful in treatment planning
  • Useful in maintaining records

Different Analysis:

Carey’s analysis:

  • Determination of arch length – From anterior of first permanent molar to mesial surface of opposite first permanent molar
  • Determination of tooth material – Mesio-distal width of teeth from 2nd premolar to 2nd premolar
  • Determination of the discrepancy – Difference between arch length and tooth material
    • Interference:
      • 0-2.5 mm – Proximal stripping
      • 2.5-5 mm – Extraction of 1st premolars
      • > 5mm – Extraction of 1st premolars

Ashley Howe’s analysis:

  • Determination of total tooth material [TTM] – Mesio-distal width of teeth from 1st molar to 1st molars
  • Determination of premolar diameter [PMD] – arch width from tip of buccal cusp of 1st premolar to that of opposite side
  • Determination of premolar basal arch width [PMBAW] – width from canine fossa of one side to other
    • Interference:
      • PMBAW% – \(\frac{\text { PMBAW } \times 100}{\text { TTM }}\)
      • 37 or less – Need for extraction
      • 44 or more – Non-extraction
      • 37 to 44 – Borderline cases

Ponts analysis:

  • By 1909
    • Determination of sum of incisors [SI] – Total mesio-distal width of 4 maxillary incisors
    • Determination of measured premolar value [MPV] – From distal pit of upper first premolar to that of opposite side
    • Determination of measured molar value [MMV] – From mesial pit of one upper first molar to that of opposite side

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

    • Determination of calculated premolar value \((\mathrm{CPV})-\mathrm{CPV}=\frac{\mathrm{SI} \times 100}{80}\)
    • Determination of calculated molar value [CMV] – CMV = \(\frac{\text { SI } \times 100}{80}\)
      • Interference:
        • Measured value < Calculated value
        • Need for expansion

Bolton’s analysis:

  • Sum of maxillary 12 – Total mesiodistal width of one 1st molar to that of other
  • Sum of mandibular 6 – Total mesiodistal width of 6 anteriors
  • Sum of maxillary 6 – Total mesiodistal width of 6 anteriors
    • Determines of overall ratio – Overall ratio = \(\frac{\text { Sum of mandibular } 12}{\text { Sum of maxillary } 12} \times 100\)
    • According to Bolton, it should be 91.3%
    • If less than 91.3% – Maxillary tooth material excess
  • Determination of Anterior Ratio:
    • Anterior ratio = \(\frac{\text { Sum of mandibular } 6}{\text { Sum of maxillary } 6} \times 100\)
    • According to Bolton, it should be 77.2%
    • If less than 77.2% – Maxillary anterior excess
    • If more than 77.2% – Mandibular anterior excess

Model Analysis Short Essays

Question 1. Arch perimeter analysis.
Answer.

  • Carey’s analysis used for maxillary arch is called arch perimeter analysis

Methods Of Arch Perimeter Analysis:

  • Determination of arch length – From anterior of first permanent molar to mesial surface of opposite first permanent molar
  • Determination of tooth material – Mesio-distal width of teeth from 2nd premolar to 2nd premolar
  • Determination of the discrepancy – Difference between arch length and tooth material
    • Interference:
      • 0-2.5mm – Proximal stripping
      • 2.5-5mm – Extraction of 2nd premolars
      • > 5mm – Extraction of 1st premolars

Question 2. Mixed Dentition Analysis.
Answer.

Moyer’s Mixed Dentition Analysis: To evaluate amount of space available in arch for erupting permanent canine and premolar

Procedure Of Mixed Dentition Analysis:

Orthodontics Model Analysis Procedure

Inference Of Mixed Dentition Analysis:

  • Compare tooth size of 3,4 and 5 and arch length available
  • Predicted value > arch length available → Crowding

Radiographic method:

  • Determine width of unerupted teeth
  • Erupted teeth in a radiograph and on a cast
\(\text { Formula } Y_1=\frac{X_1 \times Y_2}{X_2}\)

i.e. Width of unerupted tooth to be determined

\(=\frac{\text { Width of tooth erupted on cast } \times \text { Width of tooth erupted on radiograph }}{\text { Width of erupted tooth in oral cavity on radiograph }}\)

Question 3. Bolton’s analysis:
Answer.

Methods Bolton’s Analysis:

  • Sum of mandibular 12 – Total mesiodistal width of one 1st molar to that of other
  • Sum of maxillary 12 – Total mesiodistal width of one 1st molar to that of other
  • Sum of mandibular 6 – Total mesiodistal width of 6 anteriors
  • Sum of maxillary 6 – Total mesiodistal width of 6 anteriors
    • Determination of overall ratio – Overall ratio = \(\frac{\text { Sum of mandibular } 12}{\text { Sum of maxillary } 12} \times 100\)
    • According to Bolton, it should be 77.2%
    • If less than 91.3% – Maxillary tooth material excess
  • Determination of Anterior Ratio:
    • Anterior ratio = \(\frac{\text { Sum of mandibular } 6}{\text { Sum of max illary } 6} \times 100\)
    • According to Bolton, it should be 77.2%
    • If less than 77.2% – Maxillary anterior excess
    • If more than 77.2% – Mandibular anterior excess

Model Analysis Short Questions And Answers

Question 1. Assessment of tooth mass discrepancy.
Answer.

  • Measure the arch length
  • Measure the mesio-distal width of teeth

Discrepancy Of Tooth Mass Discrepancy:

  • Difference between arch length measures and tooth material

Inference Tooth Mass Discrepancy:

  • 0-2.5mm – Proximal stripping
  • 2.5-5mm – Extraction of 2nd premolars
  • > 5 mm – Extraction of 1st premolars

Question 2. Ashley Howe’s analysis.
Answer.

Methods Of Ashley Howe’s Analysis:

  • Determination of total tooth material [TTM] – Mesio-distal width of teeth from 1st molar to 1st molars
  • Determination of premolar diameter [PMD] – arch width from tip of buccal cusp of 1st premolar that of opposite side
  • Determination of premolar basal arch width [PMBAW] – width from canine fossa of one side to other

Interference Of Ashley Howe’s Analysis:

  • PMBAW%
  • 37 or less – Need for extraction
  • 44 or more – Non-extraction
  • 37 to 44 – Borderline cases

Question 3. Carey’s analysis.
Answer.

Methods Of Carey’s analysis:

  • Determination of arch length – From anterior of first permanent molar to mesial surface of opposite first permanent molar
  • Determination of tooth material – Mesio-distal width of teeth from 2nd premolar to 2nd premolar
  • Determination of the discrepancy – Difference between arch length and tooth material
    • Interference:
      • 0-2.5mm – Proximal stripping
      • 2.5-5mm – Extraction of 2nd premolars
      • > 5mm – Extraction of 1st premolars

Question 4. Peck and peck ratio.
Answer.

  • It is based on the concept of stability of rotational corrections of lower incisors rather than tooth size considerations
  • It is calculated as
    • Peck and peck ratio = Mesiodistal width / Faciolingual diameter x 100
  • Normal ratio for central incisors is 88-92% and for lateral incisors is 90-95%
  • This ratio is used to determine whether lower incisor teeth are excessively wider mesiodistally or not

Question 5. Tanaka-Johnston analysis.
Answer.

  • Tanaka-Johnston analysis is mixed dentition analysis
  • It predicts the widths of unerupted canines and premolars based on sum of the width of lower incisors

Methods Of Tanaka-Johnston Analysis:

  • Measure the total arch length
  • Measure the mesiodistal width of lower four incisors and sum them up
  • Divide the value obtained by 2 and
  • Add 10.5 mm to obtain the sum of widths of mandibular canines and premolars in one quadrant
  • Add 10.5 mm to obatin the sum of widths of maxillary canines and premolars in one quadrant
  • Formula to calculate the space available is
    • Space available = Total arch length – Sum of the lower incisors + 2 x Calculated width of canine and premolar

Advantages Of Tanaka-Johnston Analysis:

  • Simple and practical
  • Accurate
  • Require neither radiographs nor reference tables

Question 6. Korkhaus analysis.
Answer.

  • Korkhaus in 1938 proposed a study model analysis which reveals anteroposterior malpositioning of incisors in maxillary and mandibular arches
  • A measurement is made from the midpoint of the interpremolar line to a point between the two maxillary incisors
  • According to Korkhaus, for a given width of upper incisors a specific value of the distance between the two maxillary incisors should exist
  • An increase in this measuremnet denotes proclined upper anterior teeth while a decrease in this value denotes retroclined upper anterior teeth

Model Analysis Viva Voce

  • Bolton’s analysis proposes that tooth size abnormalities causes malocclusion
  • Pont’s analysis indicates the need for expansion rather than extraction
  • Peck and Peck is a model analysis of mandibular arch
  • Ashley and Howe’s analysis indicate tooth extraction if the premolar basal arch width is less than 37%

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