Model analysis 1 /certified fixed orthodontic courses by Indian dental academy


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Model analysis 1 /certified fixed orthodontic courses by Indian dental academy

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Model analysis Introduction: Model analysis is a three dimensional assessment of the maxillary and mandibular dental arches and occlusal relationships for orthodontic diagnosis and treatment planning It is a diagnostic aid, one can analyze the arch form, arch symmetry, alignment of the teeth, palate shape, tooth size, tooth shape, rotations of teeth and other information.
  3. 3. The plaster models for study cast analysis are oriented to the following planes Mid sagittal plane – for assessment of transverse discrepancies Tuberosity plane – for assessment of antero-posterior dental malposition Occlusal plane – for assessment of vertical dental malpositions
  4. 4. Analysis of tooth development : Eruption – predicting emergence Use of tables of development Sequence of eruption Number of teeth Position of teeth Anomalies Size of teeth
  5. 5. Analysis of arch form Sum of upper incisors Anterior arch width Posterior arch width Anterior arch length Palatal height Dental arch width…… PONTS ANALYSIS - indicates ideal value for anterior arch width and helps in (a) determining whether the dental arch is narrow (b) determining the need for lateral arch expansion (c) determining how much expansion is possible at premolar and molar regions
  6. 6. Determination of sum of incisors (S.I.) The mesio-distal width of the 4 maxillary incisors is measured and the values summed up. This value is called sum of incisors (S.I.) Determination of measured premolar value (M.P.V.) The width of the arch in the premolar region from the distal pit of one upper first premolar to the distal pit of the opposite first premolar is measured it is called the measured premolar value
  7. 7. Determination of calculated molar value (M.M.V.) The width of arch in molar region from the mesial pit of one upper first molar to the mesial pit of the opposite first molar is measured. This value is called the measured molar value. Determination of calculated premolar value (C.P.V.) Calculated premolar value or the expected arch width in the molar region is determined by the formula: S.I.x100/80 Determination of calculated molar value (C.M.V.) Calculated molar value or the expected arch width in molar region is determined by the formula: S.I.x100/64 Inference -: If measured value is less than calculated value, it indicates the need for expansion. Thus it is possible to determine how much expansion is needed in molar region and the premolar regions.
  8. 8. Drawbacks of Pont's Analysis: Pont being French, carried out his study over French population. So the standards can't be taken for granted or other population Sum of upper incisors can be variable eg.Peg laterals, so the inference can be misleading Pont hasn't considered the width of basal bone , which led to the illogical and irrational expansion of the dental arches in the past.
  9. 9. Linder Harth index: This analysis is very similar to Pont’s analysis except that a new formula has been proposed to determine the calculated premolar and molar value The calculated premolar value is determined using the formula: S.I.x100/ 85 The calculated molar value is determined using the formula: S.I.x100/ 64
  10. 10. Chadda index: The dental arch width in premolar and molar region is carried out in Indian population by new formula. Its similar to Pont’s index its values are more reliable Anterior arch width = S.I.x100/ 82.7 Posterior arch width = S.I.x100/ 63.7
  11. 11. Dental arch length…. Korkhaus analysis: This analysis is also similar to Pont’s analysis. In addition, this analysis utilizes a measurement made from the midpoint of the inter-premolar line to a point in between the two maxillary incisors. Determination of arch length The arch length is the distance perpendicular to the line connecting the reference points of anterior arch width in the mid-sagittal plane. The formula for calculating the standard value of the upper anterior arch length according to Korkhaus is as follow -: Maxillary arch length (Lu) = SuI x100/ 160 SuI=Sum of upper incisors
  12. 12. Correlation between maxillary and mandibular arch length -: The anterior arch length of the mandible (Ll) is shorter than the maxillary arch length (Lu) by labiolingual width of the incisal edge of the upper central incisor Standard value Ll= standard value of Lu-2mm Inference -: The measurement permits a crude analysis of the anteroposterior position of incisors. An increase in this measurement denotes proclined upper anterior teeth while a decrease in this value denotes retroclined upper anteriors.
  13. 13. Intra maxillary symmetry Transverse symmetry Anteroposterior symmetry Korbitz estimate the right-left differences in transverse and anteroposterior tooth positions To perform these measurements, precisely defined reference Planes are necessary Construction of the reference planes Midpalatal raphe: The mid-palatal raphe is constructed with help of two anatomic reference points on the palatine raphe. Anterior point ; (X) cross section of the second palatine rugae with the palatine raphe. Posterior point ; (^) the border of hard and soft palate on the raphe respectively the midpoint between the paired foveolae, next to the raphe in this segment.
  14. 14. Marking of the reference planes: Construction of midpalatal raphe (MRP) through anatomically defined midpoints on the palatine raphe of the maxilla. The MRP is the maxillary midline and reference plane for assessing transverse symmetry The anteroposterior symmetry assessment is made using the relationship to the tuberosity plane which is perpendicular to the MRP and extends through the most distally positioned maxillary tuberosity.
  15. 15. Analysis of transverse symmetry The transverse distance of the pont reference points to the arch midline is determined and the actual measured value is compared with the half value of standard width of dental arch. According to Schmuth –measurements should not to be taken from these reference points but rather from the linguogingival margin of the teeth, since erroneous measurements can occur in case of tooth rotation From a diagnostic point of view assessment of the transverse symmetry is clinically relevant, particularly in cases of transverse malocclusions Inference -: Symmetry/asymmetric width development between right and left sides of the arch (malposition, symmetric, asymmetric, unilateral)
  16. 16. Midline shift: Midline is shifted in maxillary arch when the contact point of the mesial approximal surfaces of the upper central incisors don't coincide with the midsagittal plane of the upper arch. Differentiation between dental and skeletal midline shift in mandible arch The anterior skeletal midpoint of the mandible is either determined with the help of the mental spine view or by assessing the point of insertion of the lingual frenum. But the radiographic method is most reliable.
  17. 17. Analysis of anteroposterior symmetry The analysis serves to diagnose first and foremost any mesial tooth drift. Asymmetric mesio-distal tooth position of corresponding teeth in the right and left side of the dental arches. In practice this involves drawing a line parallel to the Tuberosity plane, which runs through the posterior surface of distal-most first molar, and comparing the sagittal distances of the individual posterior teeth Inference -: If there is no right-left asymmetry, the teeth are correctly positioned or there has been symmetric mesial migration. Asymmetry of a transverse arch form may result in a relative mesial position of the more buccaly placed teeth
  18. 18. Palatal height index (P.H.I.) According to Korkhaus palatal height is defined as a vertical line perpendicular to the mid palatal raphe, which runs from the surface of the palate to the level of the occlusal plane. This is measured between the reference point of the Ponts index for the posterior width. P.H.I. = palatal height x 100/posterior arch width Measurement of palatal height -: using Korkhaus 3-dimensional orthodontic divider, the palatal height can be measured as well as posterior arch width. Palatal height is measured in the midsagittal plane in the region of the upper first molar on the level of occlusal plane Inference-: Average value is 42% Value is increased when the palatal vault relative to the transverse arch development is high and decreased when palate is shallow.
  19. 19. Analysis in vertical plane Supraversion – over eruption of teeth in relation to the occlusal plane Infraversion – under or insufficient eruption of teeth in relation to occlusal plane Occlusal plane is a constructed plane which does not actually exist, as the occlusal surfaces of teeth do not lie on one plane. Therefore precise measurements cannot be made. Occlusal plane is defined as the tangent which runs through the tips of the mesio-buccal cusps of first molars and the buccal cusps of the premolars. Curve of spee – the depth of the curve of spee is defined as the distance from the vertex of the curvature to the side of a plastic template placed over the lower arch. The template touches anteriorly the incisal edges and posteriorly the distal-most molar cusps
  20. 20. To determine the amount required to the curve of spee of space Balridge formula space required to level the arch = (Rt. Side depth + Lt. side depth / 2)+0.5
  21. 21. Bolton’s analysis Determines the tooth size discrepancy between maxillary and mandibular teeth Sum of mandibular 12 – the mesio-distal width of all the teeth mesial to the mandibular second permanent molars is measured and summed up. Sum of maxillary 12 – the mesio-distal width of all the teeth mesial to the maxillary second permanent molars is measured and summed up. Sum of mandibular 6 - the mesio-distal width of all the teeth mesial to the mandibular first premolars is measured and summed up. Sum of maxillary 6 – the mesio-distal width of all the teeth mesial to the maxillary first premolars is measured and summed up. Overall ratio = sum of mandibular 12 x100 / sum of maxillary 12 Anterior ratio = sum of mandibular 6 x100 / sum of maxillary 6
  22. 22. Inference-: If overall ratio is less than 91.3%, it indicates maxillary tooth material excess If overall ratio is more than 91.3%, it indicates mandibular tooth material excess If anterior ratio is less than 77.2%, it indicates maxillary anterior tooth material excess If anterior ratio is more than 77.2%, it indicates mandibular anterior tooth material excess
  23. 23. Analysis of apical base Ashley howe’s analysis Determines whether the deficiency in arch width or arch length Determination of total tooth material (T.T.M.) –the mesio-distal width of all the teeth mesial to the second permanent molars is measured with help of dividers and all the values are summed up. This is called as total tooth material Determination of premolar diameter (P.M.D.) –the premolar diameter refers to the arch width from the tip of the buccal cusp of opposite first premolar Determination of premolar basal arch width (P.M.B.A.W.) the canine fossa is found distal to canine eminence. The measurement of the width from canine fossa of one side to the other gives us the width of dental arch at apical base. If canine fossa is not clearly distinguishable the measurement is made from a point that 8mm below the crest of interdental papilla distal to the canine
  24. 24. Inference -: P.M.B.A.W.% = P.M.B.A.W. x100 / T.T.M If P.M.B.A.W% is 37% or less, it indicates extraction case If P.M.B.A.W% is 44% or more, it indicates non-extraction case If P.M.B.A.W% is 37-44%, borderline case
  25. 25. Space analysis in permanent dentition Determine the difference between space available and space required for alignment of teeth Nance and Carey’s analysis Determination of tooth material -: measure the mesio-distal width of each tooth mesial to the first permanent molar . The sum total of the width corresponds to the necessary space required i.e. ideal arch length.
  26. 26. Determination of arch length -: measure the actual arch length using soft brass wire. The wire is placed contacting the mesial surface of the first permanent molar of one side and is passed over the buccal cusps of premolar and along the anteriors and is continued on the opposite side in same way upto the mesial surface of the opposite first molar If proclined anteriors, the wire is passed along the cingulum of anterior teeth If retroclined anteriors, the wire is passed over the incisal edge of anteriors Determination the arch length discrepancy -: The discrepancy refers to the difference between the arch length and tooth material
  27. 27. Inference -: If ideal arch length is more than actual then negative value and space deficiency, extraction is required in that case If space available is more than ideal arch length then positive value and space excess, no extraction is required in that case
  28. 28. The Lundstorm segmental analysis Segmental analysis involves an indirect assesment of the dental arch perimeter which can be carried out in following manner-: Division of the dental arch into six straight line segments of two teeth per segment, including the first permanent molars. Measure the mesio-distal width of twelve teeth Summing the individual tooth width of each segment. Measure the available mesio-distal space on the study cast separately for each segment The sum of the difference between ideal and actual length of each segment express the space relationship
  29. 29. Peck and Peck index Peck and peck determined the presence or absence of lower incisor crowding and related to the shape of lower anterior teeth. It is based on the finding that individuals with ideal incisal arrangement had smaller mesio-distal width and larger labio-lingual width than in persons with incisal crowding Method -: 1. Measure the mesio-distal width of lower incisors 2. Measure the labio-lingual width of lower incisor individually 3. Calculate the ratio of mesio-distal width and labio-lingual width separately for lower centrals and laterals 4. Compare the value with ideal mean value Ideal mean values -: For lower centrals -: 88-92% For lower laterals -: 90-95%
  30. 30. Inference -: If calculated value is greater than mean value then mesio-distal width is more than labio-lingual width. Hence proximal stripping can be done to relieve the crowding
  31. 31. Mixed dentition analysis The purpose is to evaluate the amount of space available in the arch for succeeding permanent teeth and necessary occlusal adjustments. Many methods of mixed dentitions analysis have been suggested; however, all fall into two strategic categories: 1. Those in which the sizes of unerupted cuspids and bicuspids are estimated from measurements of the radiographic image , and 2.Those in which the sizes of the cuspids and premolars are derived from knowledge of the sizes of permanent teeth already erupted in the mouth.
  32. 32. The correlation between the sizes of mandibular incisors and the combined sizes of cuspids and bicuspids in either arch is high enough to predict the amount of space required for the unerupted teeth during space management procedures. The mandibular incisors have been chosen for measuring, since they are erupted into the mouth early in the mixed dentition, the mandibular incisors are not used in any of predictive procedures, since they show too much variability in size, and their correlations with other groups of teeth are of lower predictive value.
  33. 33. Moyer’s mixed dentition Analysis Procedure - : 1. Measure with the tooth-measuring gauge or a pointed Boley’s gauge, the greatest mesio-distal width of the four mandibular incisors. 2. Determine the amount of space needed for alignment of the incisors. Set the Boley’s gauge to the left central incisor and left lateral incisor. Place one point of the gauge at the midline of the alveolar crest between the central incisors and let the other part lie along the line of the dental arch on the left side. mark on the tooth or the cast the precise point where the distal surface of the lateral incisor will be when it has aligned. Repeat this process for the right side of the arch.
  34. 34. 3. Compute the amount of space available after incisor alignment. To do this, measure the distance from a point marked in the line of the arch to the mesial surface of first permanent molar. This distance is the space available for cuspid and two bicuspids and for any necessary molar adjustment after the incisor have been aligned. Record the data for both sides on the mixed dentition analysis form. 4. Predict the size of the combined widths of mandibular cuspids and bicuspids. Prediction of the combined widths of cuspid, first and second bicuspids is done by use of probability charts. Locate in the left column of the mandibular chart value that most nearly corresponds to the sum of the widths of the four mandibular incisors. To the right is a row of figures indicating the range of values for all the cuspid and bicuspids sizes that will be found for incisors of the indicated size. The value at the 75 percent level of probability is chosen as the estimate , since it has been found to be the most practical from clinical standpoint.
  35. 35. Tanaka and Johnson analysis Prediction of the size of unerupted canines and premolars can be done They simplified Moyers 75 percent level of the prediction table into a formula Predicted width of maxillary canine and premolar = sum of mandibular incisors + 11 divided by 2 Predicted width of mandibular canine and premolar = sum of mandibular incisors + 10.5 divided by 2
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