Modelanalysis /certified fixed orthodontic courses by Indian dental academy


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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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Modelanalysis /certified fixed orthodontic courses by Indian dental academy

  1. 1. MODEL ANALYSIS INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Why Model Analysis? • One of the essential Diagnostic aids. • Helps visualize occlusion in all planes. • Necessary measurements can be made of: Teeth Arches Basal bone • Helps in diagnosing and treatment planning when co-related with other aids.
  3. 3. Advantages of model analysis • Better understanding the case for treatment planning • Visual aid for the orthodontist to monitor tooth movement. • Serve in pre and post treatment comparison as a motivating tool. • Predicts values from different analysis. • Helps to judge between extraction and non-extraction cases • Lingual Occlusion can be visualized
  4. 4. Disadvantages of model analysis • All values are compared to standard values. • Morphogenetic alterations are not considered. • Some analysis are designed for specific population. • Not all analysis consider skeletal malrelationships. • Human error gives faulty values
  5. 5. Armamentarium • • • • • • Divider Ruler Wedge Ruler Vernier Calipers Brass wire Radiographs (in few methods)
  6. 6. Orientation of the Model • X axis is Tuberosity plane • Y axis is Midpalatal raphae plane • Z axis is Occlusal plane
  7. 7. Transverse Symmetry • Two points on mid palatal raphae defines maxillary midline • Mandibular midline is defined by lingual frenum and a perpendicular of posterior edge of midpalatine raphae from maxilla to mandible • Bernklau Symmetrograph
  8. 8. Midline shift • Midline shift in maxillary arch. • Dental midline shift • Difference between dental and skeletal midline shift in mandible
  9. 9. Anteroposterior Symmetry • Analysis of anteroposterior symmetry • co-relation between anteroposterior and transverse tooth position • Difference between unilateral and bilateral shift of posterior teeth
  10. 10. • Rotation of molars • anteroposteior symmetry in case of rotated molars • Transverse plane of incisive papilla
  11. 11. Korkhous palatal index The orthodontic divider or The orthodontic divider or orthometer was devised orthometer was devised by Korkhous. by Korkhous. Orthometer helps in Orthometer helps in giving giving •inter molar distance •inter molar distance •palatal depth •palatal depth •anteroposterior length •anteroposterior length
  12. 12. Analysing occlusion • Measuring the overjet • Class I malocclusion • Left= disto-occlusion • Right=mesio-occlusion • Class II & III • Left = neutroclusion • Right=mesio-occlusion
  13. 13. • All occlusal contacts as in an ideal occlusal set up 6 keys to normal occlusion • Molar inter-arch relationship • Mesio-distal crown angulation • Labio-lingual crown inclination • Absence of rotation • Tight contacts • Curve of spee
  14. 14. Lingual occlusion Model analysis enables view of the occlusion form the lingual aspect
  15. 15. Curve of Spee Curve of spee should not exceed 1.5mm
  16. 16. Types of Analysis In Mixed Dentition • • • • • • Huckaba’s analysis Hixton& Old Father’s method Tanaka&Johnson analysis Nance Carey’s analysis Moyer’s mixed dentition analysis Total space analysis In Permanent Dentition • • • • • • • Pont’s Index Korkhaus analysis Linder-Harth Index Arch perimeter analysis Bolton’s tooth size ratio Ashley Howe’s analysis Peck&Peck index indices depend on standard values analysis obtain independent
  17. 17. Pont’s Index(1909) • Determines the ideal dental arch width from the combined mesio-distal width of the maxillary centrals and laterals. • Two values measured and calculated are obtained for comparison. Narrow arch if calculated value> measured value. Wider arch if measured value > calculated value. • • • • Drawbacks: designed on French population- not valid universally doesn’t consider the alignment of teeth doesn’t consider the malformations of teeth. Eg: peg laterals also laterals are the most commonly found missing teeth.
  18. 18. Procedure for Pont’s Index • Measure the mesio-distal width of maxillary centrals and laterals on either sides. • Sum up the width(SI) - let it be X • Measure the arch width in premolar region from distal pits of upper first premolars. (first deciduous molar in early mixed group) • Measure the arch width in molar region from mesial pits of upper first permanent molar. • Calculate the ideal arch width in premolar and molar region by formula respectively X x 100 80 X x 100 64
  19. 19. How and where to measure? • • SI = Sum of m-d width of incisors. U - upper L-lower Tonn formula: SI u=SI L x 4 + 0.5 3
  20. 20. Linder-Harth Index • Almost similar to Pont’s index • slight variation in the formulae: Ideal arch width in premolar and molar regions are given respectively by X x 100 X x 100 85 65
  21. 21. Korkhaus analysis • Linder-Harth measurements are used along with a third measurement from midpoint of the inter premolar line of upper arch to incision between the incisal edges of upper central incisors. • Orthometer was devised to directly read ideal arch width in premolar and molar regions and also to know the perpendicular distance from interpremolar line to incision.
  22. 22. • The anteroposterior length of the mandible is normally 2mm shorter than the maxillary arch. • • L lower = L upper-2mm L is anteroposterior length
  23. 23. Considerations of Korkhaus • Analyses arch width as well as positioning of anterior segments. • Proclined arch- if L upper/L lower > ideal • Retroclined arch- if L upper/L lower < ideal However: The anterior arch length is altered by • malpositionig of anterior teeth • migration of first premolars • rotation of first molars
  24. 24. Arch Perimeter analysis • Determines the discrepancy between the basal bone and the tooth material. • If tooth material > space available crowding/space shortage • If tooth material < space available spacing/space excess
  25. 25. Procedure for maxilla • Sum up all m-d width of all teeth from second premolar on one side to the second premolar on the other side(tooth material) • measure with brass wire from mesiobuccal line angle of max 1st molar on one side and pass wire along the contacts of premolar through the incisive papilla to the opposite side to 1st molar on other side(arch perimeter)
  26. 26. Procedure for lower arch(Carey’s analysis) • Tooth material =m-d width of all teeth from second premolar of one side to other side. • Arch perimeter- measure with brass wire from m-b line angle of 1st molar, pass it along the buccal cusp tips of premolars, cinguli of anteriors and buccal cusp tips of premolars of opposite side upto m-b line angle of 1st molar
  27. 27. Extraction yes/no • Depending upon space shortage, line of suggested treatment plan : • if space shortage is between 1-2.5mm non extraction case between 2.5 - 5mm extract 2nd premolar more than 5 mm extract 1st premolar
  28. 28. Bolton Analysis/tooth ratio • Determines the ratio of m-d widths of maxillary v/s mandibular. • Overall ratio 12 mand to 12 max • anterior ratio 6 mand to 6 max • A prior defined mean value exists for overall and anterior ratios for comparison to infer. • The seventh key of Occlusion
  29. 29. inference • If values are greater than mean then it is excess of mandibular tooth material. • If values are less than mean then it is maxillary excess. • Difference of desired and actual gives the amount of excess
  30. 30. Consequences
  31. 31. Calculating the discrepancy
  32. 32. Bolton’s Chart Overall ratio Anterior ratio
  33. 33. Ashley Howe’s analysis • According to Howe inadequate apical base can also cause crowding. He designed a formula to determine if the apical base can accommodate the teeth. • It is done on both arches. • Cases can be judged for expansion or extraction.
  34. 34. Procedure • Tooth material(TM) - sum up m-d of 1-6 teeth in all quadrants separately for max and mand. • Premolar diameter(PMD)- measured from Buccal cusp tips of 1st premolar of one side to the other side. • Premolar basal arch width(PMBAW)measured from root apices of 1st premolar on one side to the other. • Basal arch length (BAL) is the perpendicular distance from the tangent drawn distally to 1st molars to anterior limit of arch
  35. 35. Calculation Howe’s standard values Upper Lower Tooth material 85-98 78.5-89 PMD 39-45 43.5-48.5 40.5-48 45.5-51.5 29.5-36.5 32.5-39.5 31-37.5 39.5-43 37.5-43.5 45.5-51.5 29-34.5 35.5-39 PMD/TM PMBAW PMBAW/TM % BAL BAL/TM % PMBAW x100% TM <37% extraction 44% ideal case 37-44% borderline
  36. 36. REES’ apical base concept • All lip and cheek frena erased from models. • 3 perpendicular lines 8-10 mm from dental papilla to vestibular fold between premolar and molar. • measure between two premolars. • Adhesive tape used to measure. • Rees standard values are used to compare.
  37. 37. Peck&Peck Index • Based on the observation that persons with ideal incisal arrangement had smaller m-d width & comparatively larger labiolingual width than in persons with incisal crowding. • Proximal stripping cases can be judged.
  38. 38. Procedure • Take m-d width of mandibular incisors individually(MD) • Take Labio/facio lingual width also individually(LL/FL) • calculate the proportion by formula MD x 100 LL/FL • mean value of lower centrals- 88-92 % • mean value of lower laterals- 90-95 % • if value is more than mean, m-d width is more than labiolingual width-- proximal stripping.
  39. 39. Huckaba’s analysis • Both study casts and radiographs are used to determine the width of unerupted teeth. • Proportion relationship is give by : actual width of primary molar (x1) apparent width of primary molar(x2) = actual width of unerupted premolar(y1) apparent width of unerupted premolar(y2) or y1= X1 x y2 X2 • Accuracy of this method-- fair to good. Depends on radiograph quality and position in arch.
  40. 40. Hixon & OldFather’s method • M-d width of mandibular central and laterals are obtained from the casts. • Width of premolars from IOPA using long cone technique. • Sum up width of centrals,laterals and unerupted premolars of that side. • The estimated sum total of the cuspids and bicuspids can be obtained when compared with standard value table.
  41. 41. Every measured sum width of incisors and bicuspids,has a corresponding sum width of cuspids and bicuspids in the following table Measured value in mm Estimated tooth size 46----------------->18.4 47----------------->18.7 48----------------->19.0 49----------------->19.4 51----------------->20.0 52----------------->20.3 53----------------->20.7 54----------------->21.0 55----------------->21.3 56----------------->21.6 57----------------->22.0 58----------------->22.3 58----------------->22.6 60----------------->22.9
  42. 42. Tanaka&Johnson analysis The prediction of the size of unerupted canines and premolars in contemporary orthodontic population can be done with the Tanaka and Johnson Analysis. Tanaka and Johnson did a study to repeat Moyer’s observation to validate it’s equation on a new sample. The possibility of secular changes within the past 20 years was to be examined and they found Moyer’s prediction table to be equally appropriate for contemporary population. However they have simplified Moyer’s 75 percent level of the prediction table into a formula. Predicted width of maxillary canine and premolar = Sum of mandibular incisors + 11 2 Predicted width of mandibular canine and premolar = Sum of mandibular incisors + 10.5 2
  43. 43. Nance Carey’s analysis • Similar to arch-perimeter analysis • measure the m-d width of erupted primary teeth • width of unerupted cuspids and bicuspids from IOPA • total m-d width of all teeth in each quadrant will indicate space required • with brass wire measure arch-perimeter • compare space required with space available to derive discrepancy
  44. 44. Moyer’s mixed dentition analysis • High co-relation among sizes of different groups of teeth--prediction possible for size of other groups depending on one group. • Measure m-d width of mandibular and maxillary incisors. • Space left behind for cuspids and bicuspids is measured from distal aspect of laterals to 1st molars distally. • Using Moyer’s probability chart, probable width of cuspids and bicuspids are got.(75%) • Space available-required= discrepancy
  45. 45. Moyer’s prediction values at 75% level Total mandibular Incisor width 19.5 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 Width of 3 4 5 (male) 20.6 20.9 21.2 21.3 21.8 22.0 22.3 22.6 22.9 23.1 23.4 Width of 3 4 5 (female) 20.1 20.4 20.7 21.0 21.3 21.6 21.9 22.2 22.5 22.8 23.1 Total maxillary incisor width 25.0 25.5 26.0 26.5 27.0 27.5 28.0 25.5 29.0 Width of 345 (male) 23.7 24.0 24.2 24.5 24.8 25.0 25.3 25.6 25.9 Width of 345 (female) 23.4 23.7 24.0 24.3 24.6 24.8 25.1 25.4 25.7
  46. 46. Total tooth space analysis • Developed by Leveren Merrifield • measurements from casts and cephalograms • this method divides the lower arch into 3 parts -------anterior middle and posterior • individual discrepancies together give arch discrepancy Anterior area: space required • width of mandibular incisors on cast and cuspids on radiographs • cephalometric correction of incisor positioning by Tweed’s method (FMIA is considered instead of IMPA of Tweed) • soft tissue modification • measure the ‘z’ angle of Merrifield and add cephalometric correction • if corrected ‘z’ angle is more than 80degree correction achieved; if <75 degree then uprighting is necessary. Space available-- brass wire from m-b line angle of first primary molar of one side to other.
  47. 47. Middle area: • Measure m-d width of first permanent molar on cast and unerupted premolar from IOPA • Curve of occlusion • the following formula gives the space required for leveling the curve of occlusion: Depth on right side + Depth on left side +5mm 2 • space available- brass wire from m-b line angle of 1st primary molar to d-b line angle of 1st permanent molar on either sides.
  48. 48. Posterior area: • Space required-- m-d width of 2nd & 3rd molars obtained from radiographs as they might be unerupted. • If not visible wheeler’s method is employed. X= Y - X1 Y1 X- estimated value of 3rd molar X1- wheeler’s value of third molar Y- Actual size of permanent 1st molar Y1- wheeler’s value of 1st molar • space available space on cast+ estimated increase
  49. 49. Kesling Diagnostic Set-up • HD Kesling introduced the diagnostic set-up which is made from an extra set of trimmed study models. • The diagnostic helps the clinician in treatment planning as it stimulates various tooth movements, which are to be carried out in the patient. • The individual teeth along with their alveolar process are sectioned off from the model using a saw and replaced back in the desired final position.
  50. 50. • The procedure is as follows. • Dental cast is related to FMIA • Constant FMIA = 65 degrees and final ideal position of mandibular incisors mesiodistally. • Align both the lower central and lateral incisors on the lower cast at FMIA = 65 degrees. • Mandibular plane 150 degrees to occlusal plane; mandibular incisors are placed at right angles to mandibular plane. • Canines are the next teeth to be positioned. • First and second premolars are then set on the model • If the remaining space on each side is adequate to receive the permanent first molars, then extraction is not required. • If space is inadequate and amounts to more than can be gained by uprighting the permanent second molars, then some teeth must be extracted usually the first premolar . When the mandibular set-up is completed the maxillary teeth are cut from their base and repositioned, then articulated to the mandibular set-up.
  51. 51. KESLING SET-UP
  52. 52. Recent advances Measurements of mesiodistal width of (a) incisor, (b) canine, (c) premolar, and (d) molar using the OrthoCAD tool, as shown from different views
  53. 53. FIGURE 2. Measurements of (A) intercanine and (B) intermolar distances using the OrthoCAD tool. The upper (u) measurements are made between the tip of the cusps, and the lower (l) between the gingival margins of the teeth
  54. 54. Digital Orthodontics • Service providers like OrthoCAD,Dolphin imaging, Holodent, dentalmodels etc, digitize the study models. • This helps the Orthodontist to get precise data using lesser chair side time. • The reliability of these digitization has been proved. • Storage of models is no more a menace.
  55. 55. Conclusion: A thorough knowledge of the analysis is always beneficial to the Orthodontist for the efficiency in the treatment.
  56. 56. Bibliography • Color Atlas of Dental Medicine Orthodontic Diagnosis - T.Rakosi • Hand book of Orthodontics - Moyers • Hand book of Facial Growth - Enlow • Current principles& techniques orthodontics - Graber & Vanersdall www. orthocad .
  57. 57. Thank you For more details please visit