Space analysis /certified fixed orthodontic courses by Indian dental academy


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Space analysis /certified fixed orthodontic courses by Indian dental academy

  1. 1. Space analysis INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Space analysis • Space analysis is one of the essential diagnostic aids • Helps to visualize patients occlusion from all aspects & also make necessary measurements of teeth & dental arches & basal bones • Study cast analysis is a three – dimension assessment of the maxillary and mandibular dental arches and the occlusal relationships.
  3. 3. Advantages of study cast analysis 1. Degree of Malocclusion can be diagnosed in the dimensions.. a) Midsaggital plan – Transverse plane b) Tuberosity plan – A-P plane c) Occlusal plan – Vertical plane 2. Inter arch irregularities. Inter arch relationship 3.To view lingual occlusion 4. Transverse discrepancies. 5. Motivation of patient. 6. Prognosis of the case – patient and doctor. 7. Treatment planning – must surgery. 8. Dental health education. 9. Assessment of the palatal vault.
  4. 4. Preparation of study models • Study models are reasonably accurate positive replica of teeth & the associated structures used primarily for the purpose of display &demonstration
  5. 5. Trimming of study models
  6. 6. Gnathostatic model by simon 1922 • The gnathostatic method of trimming casts was, in part, an effort to respond to this problem by relating the models to the orientation of the dentition in the head with reference to the Frankfort plane, the mid-sagittal plane and the preauricular plane. • The method fell into disuse partly because Simon was discredited, partly because the method was more sophisticated than orthodontic treatment at that time, and partly because it was too difficult and time- consuming. • Making models from plaster impressions and the gnathostatic technique probably did more to discourage careers in orthodontics than any other single factor.
  7. 7. Principles of space analysis Space analysis requires a comparison between the amount of space available for the alignment of the teeth & the amount of space required to align them properly
  8. 8. Principles of space Analysis Space analysis requires a comparision between the amount of space available for the alignment of the teeth and the amount of space required to align them properly . Space available space required Compare Space excess ok space deficiency
  9. 9. ANTERIOR DENTAL ARCH LENGTH. • The anterior arch length according to Korkhaus (Lu in the maxilla,Ll in the mandible) is definded as the perpendicular from the most anterior labial surface of the central incisors to the connecting line of the referance points of the anterior arch width . The measurement should reveal the anteroposterior malpositioning of the anterior teeth.
  10. 10. CORRELATION BETWEEN MAXILLARY AND MANDIBULAR ANTERIOR ARCH LENGTHS. • The anterior arch length of the mandible (LL) by the labiolingual width of the incisal edge of the upper central incisor. • As a rule the following relationship applies: • LL = LU – 2mm
  11. 11. INTRAMAXILLARY SYMMETRY. • These symmetry analyses estimate the right-left differences in transverse and anteroposterior tooth positions (Korbitz1909) • Midpalatal raphe & tuberosity plane
  12. 12. Symmetrograph of Bernklau
  13. 13. Analysis of Transverse symmetry • Symmetric / asymmetric width development between right & left sides of the arch • Congruence / incongruence between dental midline & skeletal midline
  14. 14. Midline • Dental midline deviation in the upper arch. • The contact point of the upper central incisors is shifted to the right, in relation to the midsagittal plane, i.e. to the side with lack of space for the canine. • Reichenbach and Bruckel, 1967). dental midline shift in the mandibular arch.The contact point of the lower central incisors is deviated to the left as the result of tooth drift: in an otherwise well aligned arch, the lower right lateral
  15. 15. Mixed dentition analysis • Huckabas analysis • Hixon&Oldfathers analysis • Nance Caryes analysis • Moyers Mixed dentition analysis • Tanaka johnstone • Total space analysis
  16. 16. Mixed dentition • Three approaches have been employed to estimate the mesiodistal crown widths of unerupted canines and premolars: • (1) use of measurements from erupted teeth • (2) use of measurements from radiographs • (3) use of a combination of measurements from erupted teeth and from radiographs of unerupted teeth • This last approach is considered to be the most accurate since it generally has the lowest standard error of estimate.
  17. 17. • The Moyers' 1967 probability tables for computing the sizes of unerupted canines and premolars were formulated at the University of Michigan from a sample consisting of northern European white subjects and are currently used worldwide.
  18. 18. • According to Proffit and Fields, the accuracy with Moyers' method is fairly good for northern European white children on which the data is based, despite a tendency to overestimate the size of unerupted teeth. • Sexual dimorphism has also been confirmed in several studies, with specific teeth statistically significantly larger in males than females.
  19. 19. Hixon & Oldfather • 1977 Kaplan, Smith, and Kanarek compared the prediction methods of Hixon and Oldfather, Moyers, and Tanaka and Johnston by regression analysis and found the Hixon and Oldfather estimate to be the most accurate in their sample of 104 white children. • 1979 Gardner found that the methods of Nance, Moyers, and Tanaka and Johnston tended to overpredict by 1 to 3 mm, whereas the Hixon and Oldfather technique was more likely to underpredict by about 0.5 mm • Hixon and Oldfather prediction did not appear to be seriously influenced by sex or the type of dental occlusion.
  20. 20. • The M-D width of the mandibular 1&2 from casts • Determine width of 3,4,5 from radiograph • Sum up the width of the central & lateral incisor along with the width of unerupted premolar of that side • The estimated sum total width of the cuspids & bicuspids of that particular side can be obtained from the chart • Every measured sum width of incisors & bicuspids has corresponding sum width of the cuspids & bicuspids in the chart •
  21. 21. Nance Careys analysis • Measure M-D width of the erupted permanent teeth • Measure (3,4,5) from radiographs • The total M-D width of all the teeth in each quadrant will indicate space required to accommodate the permanent • Using brass wire, measure the arch perimeter • Compare the space required & space available to arrive at the arch length discrepancy
  22. 22. Tanaka and Johnston prediction values 1974 One half of the M-D width of the four lower incisors + 10.5 = Estimated width of mandibular Canine & premolar in one quadrant + 11.0 = Estimated width of maxillary Canine & premolar in one quadrant
  23. 23. Huckaba 1967 True width of primary molar = true width of unerupted premolar apparent width of primary apparent width of unerupted premolar molar
  24. 24. Total space analysis-Merrifield1978 Anterior area Tooth measurement • Measurement of mandibular incisors widths on the cast were added to values obtained from the radio graphic measurements of the canines.
  25. 25. • Cephalometric correction was calculated for the Tweed method • FMIA was taken into consideration • The incisors were repositioned and the difference in the actual and proposed FMIA is determined. • The difference in angulation is multiplied by 0.8 to get the difference in mm
  26. 26. • Soft tissue modification • Upper lip thickness from the vermilion border of the upper lip to the greatest curvature of the labial surface of the central incisor • The total chin thickness from the soft tissue chin to the N-B line
  27. 27. • If the lip thickness is greater than chin thickness the diff is determined and multiplied by 2 and added to the space required. If it is less than or equal to chin thickness no soft tissue modification is necessary
  28. 28. • Measure the Z angle of Merrifield and add the cephalometric correction to it. • If the corrected Z angle is greater than 80 the mandibular incisor angulation was modified as necessary upto an IMPA of 92 • If the corrected angle is less than 75 additional uprighting of the mandibular incisor is necessary
  29. 29. Middle area • Measure the M-D with of the 1st permanent molar of the cast • Curve of SPEE, the deepest point between the flat surface and the occlusal surface is measured on both sides
  30. 30.
  31. 31. Posterior Area • MD width of the 2nd and 3rd molar is obtained from the radiograph. • Wheelers method is used for calculation Y – X1 X= Y1 X –estimated value of 3rd molar X1 –wheelers value of 3rd molar Y - actual size of 6 Y 1- wheelers value for 6
  32. 32. Permanent dentition analysis • Ponts index • Korkhaus analysis • Linder Harth index • Arch perimeter analysis • Bolton tooth size ratio • Howes analysis • Peck& peck index
  33. 33. Ponts index 1909 • Pont in 1909 suggested a method for determining the ideal dental arch width from the combined M-D width of the maxillary central incisors • Ideal arch width in the premolar region X x 100 80 Ideal arch width in the molar region X x 100 64
  34. 34. • Inference • If calculated value is greater than the measure value ,then arch is narrow for sum of incisors-needs expansion • If measured value is greater - arch wide – no scope for expansion
  35. 35. Linder Harth index • Similar to Ponts • Ideal arch width in the premolar region X x 100 80 • Ideal arch width in the molar region X x 100 64
  36. 36. Korkhaus analysis 1939 • Using Linder Harth measurement introduced a third measurement from the midpoint of the inter-premolar line of upper arch to point incison. • For a particular width of incisors there is a specific value of the distance from incison to the inter-premolar line • An orthometer was devised which directly measures the ideal arch width in premolar and molar region &also perpendicular distance from the inter –premolar line to the incison for a given sum mesio-distal width of the maxillary incisors (21/12)
  37. 37. Ashleys Howes • According to Howe, crowding is not only due to tooth sise ,but as a result when there is inadequate apical base • PMBAW x 100 TM
  38. 38. • Inference • The patient values should fall within the suggested range • If PMD>PMBAW, expansion is contraindicated • If PMBAW>PMD, expansion is indicated • If PMBAW x 100 TM Less than 37% -basal arch deficiency—extraction If 44% --ideal case—extraction not required If between 37% - 44% boderline case
  39. 39. Arch perimeter analysis • This analysis helps to find the difference between the basal bone & the tooth material. • The soft wire is contoured,from the mesio- buccal line angle of molar & pass along the contacts of the premolar& through the incisive papilla on an imaginary repositioned arch . • Tooth material - space required • Arch perimeter - space available
  40. 40. Careys analysis (1949) Inference • If the amount of discrepancy is between 0 to 2.5mm – non-extraction case • If it is between 2.5 to 5mm –extraction of second premolars is recommended • If it is more than 5mm – extraction of first premolar is recommended
  41. 41. Peck and Peck index • According to Peck ideal incisal arrangement had smaller mesiodistal & comparatively larger labio lingual width than in persons with incisal crowding . • On the basis of this Peck suggested certain clinical guidelines. MD x 100 LL Mean value for lower central incisor should be 88% to 92% Mean value for lateral incisors – 90% to 95%
  42. 42.
  43. 43. Boltons analysis • In 1958, Bolton published his work on interpreting mesiodistal tooth size dimensions and their effect on occlusion. • Bolton selected 55 cases with excellent occlusions, most of which (44) had been treated orthodontically (nonextraction). • The mesiodistal widths of the 12 maxillary teeth (first molar to first molar) were totaled and compared with the sum derived by the same procedure carried out on the 12 mandibular teeth. • The ratio derived between the two is the percentage relationship of mandibular arch length to maxillary arch length.
  44. 44. • He concluded that an overall ratio of 91.3 and an anterior ratio of 77.2 were necessary for proper coordination of the maxillary and mandibular teeth.
  45. 45. • If the overall ratio is greater than 91.3% ,then there is an excess of mandibular tooth material • Actual mand 12 – Corrected mand 12 = • Actual max 12 _ corrected max
  46. 46. • He computed the specific ratios of the mesiodistal widths must exist between maxillary and mandibular teeth from both canine-canine and first molar-first molar to obtain optimum occlusion and to achieve proper occlusal interdigitation in the finishing stages of orthodontic treatment.
  47. 47. • Black was one of the first investigators to measure tooth sizes and his tables of mean tooth sizes are still used today. • The tooth size measurements of Wheeler also are frequently used. • Ballard measured 500 sets of models, evaluating asymmetry in tooth sizes. Ninety percent of his sample showed a right-to-left discrepancy of 0.25 mm or more in the mesiodistal width of one or more pairs of teeth. • His observations led to the conclusion that asymmetry is the rule, not the exception, and that judicious enamel reduction or "stripping" is sometimes necessary, particularly in the anterior segments to gain proper interdigitation of teeth
  48. 48. Conclusion
  49. 49.
  50. 50. • Lundström 1954 studied 319 13-year-old children and reported on the variation in intermaxillary tooth width ratio. The mesiodistal widths were recorded and the dispersion for the three tooth size indices were calculated: • His results demonstrated a large biologic dispersion in the tooth width ratio. It was great enough to have an impact on the final tooth position, teeth alignment, and overbite and overjet relationships in a large number of these patients. This same formula originally was developed by Bolton to observe mesiodistal tooth size discrepancies.
  51. 51. Careys analysis
  52. 52. TOTAL DENTITION SPACE ANALYSIS • Merrifield • lSince the original diagnosis and treatment plan must accept the dimensions of the denture presented in the original malocclusion when musculature is normal (i.e., Class I), a total dentition space analysis allows the clinician to develop a differential diagnosis that respects the dimensions of the denture concept during the treatment planning process. • (1) anterior, (2) midarch, and (3) posterior. • (1) simplicity in identifying the area of space deficit or space surplus, • (2) a more accurate differential diagnosis.
  53. 53. ANTERIOR SPACE ANALYSIS • space available in the mandibular arch from canine to canine and a measurement of the six anterior teeth mesiodistally. • The difference is referred to as a surplus or a deficit. • Tweed's diagnostic facial triangle is also used to further analyze this area. • A head film discrepancy, based on the amount of mandibular incisor uprighting that is needed to restore facial balance, is added to the anterior space measurement. The total, if a deficit, is referred to as anterior discrepancy. Anterior discrepancies are most easily resolved, if they are the overriding consideration of the malocclusion, by removal of the first premolar teeth and by using the resulting space to move the canines distally to obtain the space to upright and align the incisors.
  54. 54. MIDARCH ANALYSIS • Careful analysis of this area can show mesially inclined first molars, rotations, spaces, deep curves of Spee, crossbites, missing teeth, habit abnormality, blocked out teeth, and occlusal disharmonies. • Crowding, deep curves of Spee, end-on, and Class II occlusions not accompanied by anterior discrepancy, all indicate a need for second premolar extraction in the lower arch. • careful measurement of the space from the distal of the canine to the distal of the first molar should be recorded as available midarch space. • To this is added the space required to level the curve of Spee. From these measurements one can determine the space deficit or surplus in this area. • Many diagnosticians have suggested that they extract second premolar teeth to eliminate facial retrusion. This is faulty reasoning. These cases have, as a rule, very little anterior discrepancy, and the second premolars are removed because their space is most advantageously used for the midarch problems that these cases usually demonstrate. The midarch space analysis is critical in proper differential diagnosis.
  55. 55. POSTERIOR SPACE ANALYSIS • The posterior denture area has great importance, and has at times been ignored or mistreated by our specialty. The required space in the posterior space analysis is the mesiodistal width of the second molars and the third molars in the mandibular arch. The available space is more difficult to ascertain on the immature patient. It is a measurement in millimeters of the space distal to the mandibular first molars along the occlusal plane to the anterior border of the ramus, plus an estimate of posterior arch length increase, based on both age and sex. • There are certain variables that must be considered in estimating the increase in posterior space available. These variables are as follows: • 1. Rate of mesioocclusal migration of the mandibular first molar. • 2. Rate of resorption of the anterior border of the ramus. • 3. Time of cessation of molar migration. • 4. Time of cessation of ramus resorption. • 5. Sex. • 6. Age.
  56. 56. • A review and study of the literature10-12 reveals that a consensus of researchers suggests 3 mm of increase in the posterior denture area occurs per year until age 14 years for girls and age 16 years for boys. This is a 1.5 mm increase on each side per year after the full eruption of the first molars. In the mature patient, girls beyond 15 years and boys beyond 16 years, one can measure from the distal of the first molar to the anterior border of the ramus at the occlusal plane and have an accurate determination of the space available in the posterior area. It is of extreme importance to know whether there is a surplus or deficit of space in this area during diagnosis and treatment planning. It is imprudent to create a posterior discrepancy while making adjustments in other areas— the midarch, or in the anterior area. It is equally imprudent not to use a posterior space surplus to help alleviate midarch and anterior deficits. The most easily recognizable symptom of a posterior deficit on the young patient is the late eruption of the second molar. If space is not available for this tooth by the age of its normal eruption, then one can pretty well ascertain that there is a posterior space problem. A good lateral jaw radiograph can immediately confirm the clinical observation by using the above-mentioned guidelines.
  57. 57. • In summary, a total space analysis that analyzes the anterior, midarch, and posterior denture areas is a valuable diagnostic tool. It enables the orthodontic specialist to treat within the dimensions of the denture in the case with normal muscular balance. A total dentition space analysis, used within the dimensions of the denture framework, enables the orthodontist to make correct differential diagnostic decisions. • Diagnosis, by definition, is both subjective and objective. Webster defines diagnosis as a "determination of a disease from symptoms, data, or tests and the decisions and judgements made prior to treatment." Thus the determination made in regard to whether, when, and which teeth need to be eliminated for proper space management is a differential diagnostic process. When diagnostic guidelines or decisions are suggested, they can appropriately be called "one man's opinion." The following diagnostic space management guidelines are suggested for use and should not be considered as rules. These space management suggestions are based on space analysis only. Any complete diagnostic scheme has to consider the facial pattern and the skeletal pattern.
  58. 58. • Lower incisor space analysis - Harris, Vaden, and Williams • -------------------------------- • The common situation in which the incisors are labially displaced against the cortical plate is difficult to assess from the casts alone. During uprighting of the incisors, the radius of the anterior arch decreases and, along with it, the actual space available. This sort of error can be minimized by inspecting the incisor positions on the lateral head film and adjusting the space available accordingly. One such method is to calculate a ''head film discrepancy value." This is the millimetric distance the lower incisors must be uprighted in order to be placed over basal bone and into a position of balance with the facial structures.24 Typically this procedure is indicated because often all six anterior teeth need to be retracted and uprighted— and the increase in the required space has to be gained from extractions in the midarch. A case in point has been illustrated (Fig. 2, B); the casts exhibit spacing of the lower anterior teeth, but they are proclined to an IMPA of 97° and are at the anterior limit of the alveolar bone. Treatment involved uprighting the lower incisors 9° and retracting them 6 mm (I to NP decreased 6 mm).
  59. 59. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1987 Nov (375 - 380): Lower incisor space analysis - Harris, Vaden, and Williams • -------------------------------- • One other diagnostic consideration that warrants attention is the soft-tissue profile and its relation to tooth position. A compensation should be made in any diagnostic scheme for a maldistribution of soft-tissue thicknesses. One approach25 is to compare total chin thickness (Pg' measured normal to the nasion-B-point line) with upper lip thickness. Integumental compensation is needed in the direction of more upright lower incisors in those patients possessing less total chin thickness than upper lip thickness. Compensation is not indicated when the total chin and upper lip thicknesses are equal.25
  60. 60. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1994 Nov (535 - 542): Dimensions of the denture - Merrifield • -------------------------------- • INTRODUCTION TO DEFICITS AND DECISIONS Space management guidance • A. Anterior surplus or deficit:+ to -2mm Space Management Nonextraction • 3 to 5 mm without crowding. Extract: • 3 to 5 mm with crowding. Extract: • 5 to 7 mm with less than 3 mm anterior crowding. Extract: • 5 to 7 mm with more than 3 mm anterior crowding. Extract: • 7 to 15 mm anterior deficit. Extract: • 16 mm and above. Extract:
  61. 61. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1994 Nov (535 - 542): Dimensions of the denture - Merrifield • -------------------------------- • B. Midarch surplus or deficit: An anterior deficit or surplus overrides a midarch deficit so the first determination is a decision on the anterior deficit. • + to 3 mm Nonextraction • 3 to 5 mm without crowding. Extract: • 3 to 5 mm with Class II molar. Extract: • 5 to 7 mm with upper anterior protrusion.Extract: • 5 to 7 mm Extract: • 8 to 15 mm Extract: • Over 15 mm Extract: • *(Use X for all molars: first, second, and third.)
  62. 62. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1994 Nov (535 - 542): Dimensions of the denture - Merrifield • -------------------------------- • C. Posterior surplus or deficit: The space analysis m this area is of great importance, although in corrective procedures, anterior and midarch deficits are overriding. The posterior space must be carefully measured and protected. No orthodontic treatment is complete until all decisions and treatment procedures are completed in this area. • + to -5 mm with good position of the third molars. Await full development of the third molars. • + to -5 mm with poor position of third molars. Extract: • Note: Wait for maxillary third molars until age 16 years. Have the mandibular third molars removed immediately if other treatment is necessary. • 5 to 15 mm. Extract: • (Determine the timing of these third molar extractions in relationship to symptoms and other treatment that is necessary.) • Consistent, quality orthodontic treatment results are based on fundamental concepts. The concept of dimensions of the denture is predicated on the conviction that the teeth and their supporting structures should be in a state of maximum environmental harmony (dynamic equilibrium). Total dentition space analysis, based on the dimension of the denture concept, is a valuable tool that can help the orthodontic specialist produce a consistently high quality result that meets the needs and expectations of the patient.
  63. 63. • Anterior space analysis: Anterior space analysis includes the measurment in millimeters of the space available in the mandibular arch from canine to canine and a measurment of the mesiodistal dimension of each of the six anterior teeth. The difference is referred to as a surplus or deficit. The Tweed diagnostic facial triangle is also used to further analyze this area. Lateral headfilm discrepancy is the amount of space required to position the mandibular incisors for facial balance. This value is added to the anterior space measurement. • The thickness of the soft tissue (upper lip versus total chin) must also be considered as part of the anterior space analysis. Total chin thickness should equal upper lip thickness. If it is less than upper lip thickness, the anterior teeth must be uprighted further to create a more balanced profile because lip retraction follows tooth uprighting. • The sum of the anterior tooth arch surplus or deficit, the cephalometric discrepancy, and the soft tissue thickness imbalance is referred to as the anterior discrepancy. Each of the three values in the anterior discrepancy calculation has been given a difficult factor so that an anterior space analysis difficulty value can be calculated.
  64. 64. • Midarch space analysis: The midarch area includes the mandible first molars and the first and second premolars. Careful analysis of this area may show mesially inclined first molars, rotation, spaces, a deep curve of spee, crossbites missing teeth, habit abnormality, blocked out teeth, and occlusal disharmonies. This is an extremely important area of the dentition. Because it is in the center of the arch, this area allows the easiest and most direct method of space management for malocclusion correction when it can be so used. Crowding, a deep curve of spee, and end – on or full – step Class II occlusions, not a accomplained by anterior disctepancy, indicate a need for second premolar extraction in the mandibular arch.
  65. 65. • These variables are the following: • 1. Rate of mesio-occlusal migration of the mandibular first molar. • 2. Rate of resorption of the anterior border of the ramus. • 3. Time of cessation of molar migration. • 4. Time of cessation of ramus resorption. • 5. Gender. • 6. Age.
  66. 66. • A review of the literature 6,22,38 reveals that a consensus of researchers suggests that 3 mm of increase in the posterior denture area occurs per year until age 14 for girsls and age 16 for boys. This is an increase of 1.5 mm on each side per year after the full eruption of the first molars. In the mature patient (girls beyond 15 years and boys beyond 16 years) a measyrement from the distal of the first molar to the anterior border of the ramus at the occlusal plane is a valuable determination of the space available in the posterior area.
  67. 67. • Taken from the JCO 1985 Jun (445-448): Analytical Orthodontic Computer Programs - DENNIS M. KILLIANY, DDS, MSD • -------------------------------- • Analytical Orthodontic Computer Programs • DENNIS M. KILLIANY, DDS, MSD • I have developed a computer program that performs several diagnostic analyses— cephalometric, mixed dentition, and tooth size— and a practice management analysis of patient starts. This program is written in Basica on an IBM PC-XT. It will also run with GWBASIC on many IBM-compatible computers. The two versions of the program (ANALYSES.M— monochrome and ANALYSES.C— color) are available to any interested practitioner.
  68. 68. • Taken from the JCO 1985 Jun (445-448): Analytical Orthodontic Computer Programs - DENNIS M. KILLIANY, DDS, MSD • -------------------------------- • It is not the purpose of this seminar to discuss the validity of each analysis. These analyses, by themselves, may not provide sufficient information upon which to base a diagnosis and treatment plan. Care must be taken in applying a mathematical analysis to patients. For example, although a statistically significant relationship has been shown to exist between the size of lower incisors and their crowding, the strength of the relationship is weak. Hence, indiscriminate mesiodistal narrowing of lower incisors based on their existing faciolingual dimensions may not lead to a clinically significant increase in stability. Although many of the assumptions made in these analyses have been exhaustively argued, the analyses can still be valuable tools for diagnosis when combined with a complete clinical and cephalometic appraisal of a patient.
  69. 69. • Even in children with well proportional faces, the position of the p[ermanent molars changes when primary molar are replaced by the problems. If space analysis is done in the mixed dentition, it is necessary to adjust the space available measurment to reflect the shift in molar position that can be anticipated. • Model Analysis • Model analysis is one of the essential diagnostic aids. Study models helps us to visualize the patient’s occlusion from all aspects and also helps us in making the necessary measurements of the teeth, the dental arches and the basal bone to carry out the various types of model analysis. Most of the model analysis suggested by various authors does not correlate the findings of model analysis with other diagnostic aids such as cephalogram and panoramic radiographs and hence the diagnostic value of such independent model analysis is questionable. However, the model analysis is still used widely in orthodontic practice and provides us with valuable information and when it is completed with other diagnostic aids will help us in diagnosing and planning treatment of a case.
  70. 70. • Study models aid diagnosis in the following wasys. • 1. They enable occlusal relationships to be observed, which might not otherwise be visible. • For example, when the overbile is increased, the point of contact of the lower incisor edges with the opposing arch cannot be determined clinically and yet can easily be seen on the models. • Visulize the lingual occlusion. • Orientetion of study models • Construction of reference plens. • 1. Mid palatal reph – is a reference plane for assessing transverse symetry. • 2. Tuberosly plane – is a refer plann for ass antero posterior symmetry. • Assement of symmtry • 3. Symmetrograph according to Bernklace a transparent plastic frid oriented to the mid palated and tuberosity plane is and for assening symmetical arch shape.
  71. 71. • Baldridge1969studied the effect of leveling the curve of Spee on mandibular arch length in thirty adults with exaggerated curves of Spee and all mandibular teeth anterior to the third molars erupted. He found that leveling the curve of Spee required an average of 3.5 ± 0.14 mm of additional arch length without expansion of the arch buccally or labially. The range of required additional arch length varied from 2.3 mm to 5.2 mm. Baldridge developed prediction equations for estimating the required additional arch length. No method of prediction is available for the mixed dentition; however, consideration for the effect of the curve of Spee needs to be part of an overall mixed-dentition arch length analysis. Merrifield1978 proposed a simplified method of estimating the required space to level the curve of Spee, based on Baldridge findings. He suggested averaging the height of the curve of Spee at its greatest curvature on both sides. The calculated value presents, in millimeters, the additional arch length required for leveling the curve of Spee.
  72. 72. • Molar relationship • Lower incisor inclination • Curve of spee
  73. 73. •(1) the Hixon and Oldfather prediction could be performed before eruption of the lateral incisor • (2) the method tended to underestimate the canine and premolars to the extent that the clinician would be less likely to embark on early extraction regimes.
  74. 74. - Bishara and Staley • Mandibular tooth size— arch length analysis • A step-by-step chart was developed for use in conjunction with the prediction graph to estimate the tooth size— arch length discrepancy for the patient. • The chart and graph would be part of the clinical record developed for patients undergoing mixed-dentition evaluation and/or treatment. A copy of the chart and graph can be obtained by writing to the authors. • The first four steps in the chart involve taking measurements of the predictor variables as illustrated in. • It is important that the periapical radiographs be taken with a long-cone paralleling technique. • The sum of the four predictor variables for each side of the arch is entered in step 5 of the chart. • This sum is then taken to the horizontal (bottom) axis of the prediction graph. The vertical line nearest the point along the horizontal axis where the sum is located is then followed upward to the diagonal prediction line. The point of intersection of the vertical and diagonal lines is then followed leftward on a horizontal line to the vertical (left) axis, where the predicted sum of the unerupted canine and premolars is found.
  75. 75. • - Bishara and Staley • If measurements of predictor variables were available for only one side of the arch, it can be reasonably assumed, on the basis of the high degree of bilateral symmetry in canine and premolar tooth widths, that the predicted sum of unerupted canine and premolar widths would be very similar for the two sides of the arch. Badly rotated premolars on a radiograph are best not measured. If the antimere tooth is not rotated on the radiograph, its measurement can be substituted for that of the rotated tooth. • The standard error of estimate for the prediction graph is 0.44 mm. It is expected that for approximately 68% of the patients with a particular estimate the actual widths of the premolars and canine will be within a range of values as high as 0.44 mm above the estimate to as low as 0.44 mm below the estimate.
  76. 76. • Bishara and Staley • The estimate of canine and premolar size that is obtained from the prediction graph is the mean or aver age estimate. The average estimate at the fiftieth percentile is larger than the true sum of widths for half of all possible patients and smaller than the true sum of widths for half of all possible patients. Some clinicians prefer to choose the predicted sum at a percentile above 50, so that the error or prediction would be on the overestimation side rather than the underestimation side. Moyers3 recommends prediction at the seventy-fifth percentile as a protection against underpredicting the true size. Adding one standard error of estimate to the predicted sum would give a predicted sum of widths at the eighty- fourth percentile. This would assure the clinician that the predicted sum of canine and premolar widths is as large as, or larger than, the true sum in 84% of all possible patients. For those who want protection against underprediction of the tooth widths, we recommend that one standard error of estimate be added to the predicted sum that is obtained from the prediction graph. The standard error of estimate is added to the predicted sum of unerupted canine and premolar widths in steps 7 and 8 of the chart (Fig. 3).
  77. 77. • Posterior arch length is measured as illustrated in Fig. 5 and is entered in step 9 of the chart. When the deciduous canine is present in the arch, an additional arch length measurement in the canine part of the arch is added to the length measured between the mesial surface of the permanent first molar and the distal surface of the deciduous canine. The estimate of the unerupted canine and premolar widths is subtracted from the posterior arch length measurement (step 9, Fig. 3). This step is repeated for the other side (step 10), and then the estimates for the two posterior segments are added (step 11). • Anterior arch length is measured as illustrated in Fig. 6. It is important that the two anterior segments be measured from the same point in the midline. Marking the midline point with a pencil is recommended. The sum of the incisor widths, measured in steps 1 and 2 of the chart, are then subtracted from the anterior arch length. The remainder of this subtraction is entered in step 12 of the chart (Fig. 3). • The total arch length— tooth size relationship is summarized in step 13 of the chart, with a positive number indicating excess arch length and a negative number indicating an arch length deficiency. • As suggested by Merrifield,17 other parameters need to be considered in the space analysis; for example, the anteroposterior relationship of the first permanent molars, the anteroposterior position of the lower incisors, and the degree of curve of Spee.
  78. 78. • An index for assessing tooth shape deviations - Peck and Peck. • . A mandibular central incisor showing the mesiodistal (MD) and faciolingual (FL) crown diameters. The MD/FL index (MD/FL ´ 100) is a numerical expression of the crown's shape as seen from the incisal aspect. For the incisor shown, the MD diameter approximately equals the FL diameter, yielding an MD/FL index of 100. If the MD diameter of this tooth were greater than its FL diameter, the index would be greater than 100. Similarly, if the MD diameter were less than the FL diameter, the index would be less than 100.
  79. 79. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO-DO), Volume 1984 Aug (130 - 135): Mixed-dentition mandibular arch length analysis - Bishara and Staley • -------------------------------- • The molar relationship in the mixed dentition is very frequently end to end (Fig. 7, A). The transition to a full Class I relationship will require either some type of orthodontic intervention or allowing the mandibular molars to migrate mesially in the leeway space. If the latter approach is considered, the amount of mesial migration of the first molars should be estimated by measuring the distance between the mesiobuccal cusp tip of the upper molar and the buccal groove of the lower molar as illustrated by the arrow in Fig. 7, A. This distance, on each side, is then subtracted from the arch length.
  80. 80. • Source: AJO-DO on CD-ROM (Copyright © 1998 AJO- DO), Volume 1984 Aug (130 - 135): Mixed-dentition mandibular arch length analysis - Bishara and Staley • -------------------------------- • To estimate the arch length needed to upright (move lingually) the mandibular incisors (Fig. 7, B), Tweed18 suggested multiplying the number of degrees of uprighting by 0.8. The calculated value represents, in millimeters, the additional arch length required to upright the teeth. Conversely, if the treatment plan requires labial movement of the mandibular teeth, the same formula is used to estimate the additional arch length to be gained.
  81. 81. • Ingervall and Lennartsson1978 and Zilberman, Koyoumjisky-Kaye, and Vardimon1977 also concluded that the unerupted canine and premolars could be predicted more accurately from radiographs than from dental casts alone. • , Moyers' technique is still widely accepted because it does not require radiographs and is, arguably, more readily applied by a spectrum of clinicians ( Runey , Johnson , Merow 1977)
  82. 82. CORRELATION BETWEEN DENTAL ARCH FORM AND SUM OF INCISORS. • The pont –index is based On various examinations of the geometry of normal dental arches. • According tp these graphic diagrams, the size of the near- elliptical shape of the maxillary dental arch is related to the width of the upper incisor teeth. • Depending on the sum value of the upper incisors,the elliptical forms are of different size but of similar shape.
  83. 83. CORRECTION BETWEEN DENTAL ARCH WIDTH AND ARCH LENGTH. • View of a wide, short maxillary arch. The shape of the normal arch depends on the development of width and length which is in the ratio of 2;1 for example if the arch width is increased by 2mm,the arch length is reduced by 1mm. • The ideal arch width value determined according to pont can be individualized if both parameters (length and width) are considered.
  84. 84. MEASUREMENTS OF ANTERIOR ARCH LENGTH. • Overview of the maxillary and mandibular arches,with marking of the referance lines for antrerior arch length determination. • The arch length is defined as the distance perpendicular to the line connecting the referance points of anterior arch width in the midsagittal plane. It is measured from the intersection of the two lines to the labial surface of the most anterior positioned central incisor.
  85. 85. Analysis of Transverse symmetry
  86. 86. • Neff measured the mesiodistal dimensions of the maxillary and mandibular teeth of 200 patients. • He developed an "anterior coefficient" by dividing the sum of the six maxillary anterior teeth by the mandibular mesiodistal sum. • The range was 1.17 to 1.41 mm, but no means were given. • Neff then correlated these ratios to the amount of overbite and concluded that a 20% overbite with a coefficient of 1.20 to 1.22 mm was ideal; the value of 1.17 mm was associated with an edge-to-edge incisor relationship (Class I large mandibular teeth) and the other extreme of 1.41 mm was associated with a deep overbite relationship (Class I small mandibular teeth).
  87. 87. • The first step in space analysis is calculation of space available .This is by measuring the arch perimeter from one first molar to the other ,over the contact points of posterior teeth & incisal edge of anteriors. • The second step is to calculate the amount of space required for alignment of the teeth.
  88. 88. • The first step is space analysis is calculation of space available. • This is accomplished by measuring the arch perimeter from one first molar to the other, over the contact point of posterior teeth and incisial edge of anteriors.
  89. 89. Contouring a piece of wire -
  90. 90. Measured as straight line approximation of arch
  91. 91. • The second step is to calculate the amount of space required for alignment of the teeth. • This is done by measuring the M-D width of each tooth from contact point to contact point • If the sum of the width of the permanent teeth is greater that the amount of space available there is an arch perimeter space deficiency and crowding would occur. • If available space is large then the space required (excess space) gaps between some teeth would be expected.
  92. 92. • Space analysis carried out in this way is based on two important assumption. 1. The A – P position of the incisors is correct. (i.e) The incisors are neither excessively protrusive nor retrusive) 2. The space available will not change because of growth. Neither assumption can be taken for granted.
  93. 93. • If the incisors flare forward, they can align themselves along the arc of a larger circle , which provides more space to accommodate the teeth and alleviates crowding. • Conversely, if the incisors move lingually there is less space and crowding becomes worse. • For this reason, crowding and protrusion of incisors must be considered two aspects of the same thing: how crowded and irregular the incisors are reflects both how much room is available and where the incisors are positioned relative to supporting bone. • For this reason, information about how much the incisors protude must be available from clinical examination to evaluate the results of space analysis.
  94. 94. • The second assumption, that space available will not change during growth, is valid for adults but may not be for children. • In a child with a well proportional face, then is little or no tendency for the dentition to be displaced relative to the jaw during growth, but the teeth after shift artcroly or pertrits in a child with a jaw discrepency. • For this reason, space analysis is less accurate and less useful for children with skeletal problem (class II, Class III, long face , short face) than in those with good facial proportions.
  95. 95. Shortended arch length LINGUOVERSION OF CENTERAL INCISORS • Shortended anterior arch length in the maxilla resulting from lingual inclination of upper central incisors in a class 11 division 2 • Malocclusion
  96. 96. MESIAL POSITION OF PREMOLARS • Markedly shortened anterior arch length in the maxilla as the result of mesial drift of posterior teeth ollowing early loss of deciduous teeth in the supporting zones. • The axial inclination of the upper incisors is approximately corect,in spite of a reducedLu.
  97. 97. Analysis of anteroposterior symmetry. • Serves to analyse any mesial tooth drift. • Symptoms of mesial position of posterior teeth • Crowding and space loss, especialy in the supporting zones. • Dental midline shift with crowding and space loss • Mesial topping of premolars. • Rotation of first permanent molars. • Symmetric / asymmetric width development between right and left sides of the arch (malposition: symmetric, asymmetric, unilateral). • Congruence/incongruence between dental midline and skeletal midline of the arches (dental midline shift). • Dental midline shift. • Dental midline shifts are the result of tooth migration.
  98. 98. Palatal height
  99. 99. Analysis of supporting zones
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  109. 109. Thank you For more details please visit