Model Analysis 1 / orthodontic courses by Indian dental academy

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Model analysisModel analysis

Introduction:Introduction:Model analysis is a three dimensional Model analysis is a three dimensional assessment of the maxillary and mandibular assessment of the maxillary and mandibular dental arches and occlusal relationships for dental arches and occlusal relationships for orthodontic diagnosis and treatment planningorthodontic diagnosis and treatment planningIt is a diagnostic aid, one can analyze the arch It is a diagnostic aid, one can analyze the arch form, arch symmetry, alignment of the teeth, form, arch symmetry, alignment of the teeth, palate shape, tooth size, tooth shape, rotations palate shape, tooth size, tooth shape, rotations of teeth and other information.of teeth and other information.


The plaster models for study cast analysis The plaster models for study cast analysis are oriented to the following planesare oriented to the following planesMid sagittal plane – for assessment of Mid sagittal plane – for assessment of transverse discrepanciestransverse discrepanciesTuberosity plane – for assessment of Tuberosity plane – for assessment of antero-posterior dental malposition antero-posterior dental malposition Occlusal plane – for assessment of Occlusal plane – for assessment of vertical dental malpositionsvertical dental malpositions


Analysis of tooth development :Analysis of tooth development :

Eruption – predicting emergence Eruption – predicting emergence Use of tables of developmentUse of tables of developmentSequence of eruptionSequence of eruption

Number of teethNumber of teeth

Position of teethPosition of teeth

AnomaliesAnomalies

Size of teethSize of teeth


Analysis of arch formAnalysis of arch formSum of upper incisorsSum of upper incisorsAnterior arch widthAnterior arch widthPosterior arch widthPosterior arch widthAnterior arch lengthAnterior arch lengthPalatal heightPalatal height

Dental arch width……Dental arch width……

PONTS ANALYSIS - indicates ideal value for anterior arch width PONTS ANALYSIS - indicates ideal value for anterior arch width and helps inand helps in(a) determining whether the dental arch is narrow(a) determining whether the dental arch is narrow(b) determining the need for lateral arch expansion(b) determining the need for lateral arch expansion(c) determining how much expansion is possible(c) determining how much expansion is possible

at premolar and molar regionsat premolar and molar regions


Determination of sum of incisors (S.I.)Determination of sum of incisors (S.I.) The mesio-distal width of the 4 maxillary incisors The mesio-distal width of the 4 maxillary incisors

is measured and the values summed up. This is measured and the values summed up. This value is called sum of incisors (S.I.)value is called sum of incisors (S.I.)

Determination of measured premolar value Determination of measured premolar value (M.P.V.)(M.P.V.)

The width of the arch in the premolar region from The width of the arch in the premolar region from

the distal pit of one upper first premolar to the the distal pit of one upper first premolar to the distal pit of the opposite first premolar is distal pit of the opposite first premolar is measured it is called the measured premolar measured it is called the measured premolar value value


Determination of calculated Determination of calculated molar value (M.M.V.)molar value (M.M.V.) The width of arch in molar region from the mesial pit of one upper first molar 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 to the mesial pit of the opposite first molar is measured. This value is called the measured molar value.the measured molar value.

Determination of calculated premolar value (C.P.V.)Determination of calculated premolar value (C.P.V.)

Calculated premolar value or the expected arch width in the molar region is Calculated premolar value or the expected arch width in the molar region is determined by the formula: S.I.x100/80determined by the formula: S.I.x100/80

Determination of calculated molar value (C.M.V.)Determination of calculated molar value (C.M.V.) Calculated molar value or the expected arch width in molar region is Calculated molar value or the expected arch width in molar region is

determined by the formula: S.I.x100/64determined by the formula: S.I.x100/64

Inference -:Inference -:

If measured value is less than calculated value, it indicates the need for 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 expansion. Thus it is possible to determine how much expansion is needed in molar region and the premolar regions.in molar region and the premolar regions.www.indiandentalacademy.comwww.indiandentalacademy.com

Drawbacks of Pont's Analysis:Drawbacks of Pont's Analysis:

Pont being French, carried out his study over Pont being French, carried out his study over French population. So the standards can't be French population. So the standards can't be taken for granted or other populationtaken for granted or other populationSum of upper incisors can be variable eg.Peg Sum of upper incisors can be variable eg.Peg laterals, so the inference can be misleadinglaterals, so the inference can be misleadingPont hasn't considered the width of basal bone , Pont hasn't considered the width of basal bone , which led to the illogical and irrational expansion which led to the illogical and irrational expansion of the dental arches in the past.of the dental arches in the past.


Linder Harth index:Linder Harth index:

This analysis is very similar to Pont’s analysis This analysis is very similar to Pont’s analysis except that a new formula has been proposed to except that a new formula has been proposed to determine the calculated premolar and molar determine the calculated premolar and molar valuevalue

The calculated premolar value is determined The calculated premolar value is determined using the formula: S.I.x100/ 85using the formula: S.I.x100/ 85

The calculated molar value is determined using The calculated molar value is determined using the formula: S.I.x100/ 64the formula: S.I.x100/ 64


Chadda index:Chadda index:The dental arch width in premolar and molar The dental arch width in premolar and molar region is carried out in Indian population by region is carried out in Indian population by new formula.new formula.

Its similar to Pont’s index its values are more Its similar to Pont’s index its values are more reliable reliable

Anterior arch width = S.I.x100/ 82.7Anterior arch width = S.I.x100/ 82.7

Posterior arch width = S.I.x100/ 63.7Posterior arch width = S.I.x100/ 63.7


Dental arch length….Dental arch length….

Korkhaus analysis:Korkhaus analysis: This analysis is also similar to Pont’s analysis. In This analysis is also similar to Pont’s analysis. In addition, this analysis utilizes a measurement made from addition, this analysis utilizes a measurement made from the midpoint of the inter-premolar line to a point in the midpoint of the inter-premolar line to a point in between the two maxillary incisors.between the two maxillary incisors.Determination of arch length Determination of arch length The arch length is the distance perpendicular to the line The arch length is the distance perpendicular to the line connecting the reference points of anterior arch width in connecting the reference points of anterior arch width in the mid-sagittal plane.the mid-sagittal plane.The formula for calculating the standard value of the The formula for calculating the standard value of the upper anterior arch length according to Korkhaus is as upper anterior arch length according to Korkhaus is as follow -:follow -:

Maxillary arch length (Lu) = SuI x100/ 160Maxillary arch length (Lu) = SuI x100/ 160 SuI=Sum of upper incisors SuI=Sum of upper incisors


Correlation between maxillary and mandibular arch Correlation between maxillary and mandibular arch length -:length -:The anterior arch length of the mandible (Ll) is The anterior arch length of the mandible (Ll) is shorter than the maxillary arch length (Lu) by shorter than the maxillary arch length (Lu) by labiolingual width of the incisal edge of the upper labiolingual width of the incisal edge of the upper central incisorcentral incisor

Standard value Ll= standard value of Lu-2mmStandard value Ll= standard value of Lu-2mm

Inference -:Inference -:The measurement permits a crude analysis of the The measurement permits a crude analysis of the anteroposterior position of incisors.anteroposterior position of incisors.An increase in this measurement denotes An increase in this measurement denotes proclined upper anterior teeth while a decrease in proclined upper anterior teeth while a decrease in this value denotes retroclined upper anteriors.this value denotes retroclined upper anteriors.


Intra maxillary symmetryIntra maxillary symmetryTransverse symmetry Transverse symmetry

Anteroposterior symmetryAnteroposterior symmetry

Korbitz estimate the right-left differences in transverse and anteroposterior Korbitz estimate the right-left differences in transverse and anteroposterior tooth positions tooth positions

To perform these measurements, precisely defined reference To perform these measurements, precisely defined reference Planes are necessary Planes are necessary Construction of the reference planesConstruction of the reference planes

Midpalatal raphe: Midpalatal raphe: The mid-palatal raphe is constructed with help of two anatomic reference points The mid-palatal raphe is constructed with help of two anatomic reference points

on the palatine raphe.on the palatine raphe. Anterior point ;Anterior point ; (X) cross section of the second palatine rugae with the palatine (X) cross section of the second palatine rugae with the palatine

raphe.raphe. Posterior point ;Posterior point ; (^) the border of hard and soft palate on the raphe respectively (^) the border of hard and soft palate on the raphe respectively

the midpoint between the paired foveolae, next to the raphe in this segment.the midpoint between the paired foveolae, next to the raphe in this segment.


Marking of the reference planes:Marking of the reference planes:

Construction of midpalatal raphe (MRP) through Construction of midpalatal raphe (MRP) through anatomically defined midpoints on the palatine anatomically defined midpoints on the palatine raphe of the maxilla. The MRP is the maxillary raphe of the maxilla. The MRP is the maxillary midline and reference plane for assessing midline and reference plane for assessing transverse symmetrytransverse symmetryThe anteroposterior symmetry assessment is The anteroposterior symmetry assessment is made using the relationship to the tuberosity made using the relationship to the tuberosity plane which is perpendicular to the MRP and plane which is perpendicular to the MRP and extends through the most distally positioned extends through the most distally positioned maxillary tuberosity.maxillary tuberosity.


Analysis of transverse symmetryAnalysis of transverse symmetryThe transverse distance of the pont reference points to the The transverse distance of the pont reference points to the arch midline is determined and the actual measured value is arch midline is determined and the actual measured value is compared with the half value of standard width of dental arch.compared with the half value of standard width of dental arch.According to Schmuth –measurements should not to be According to Schmuth –measurements should not to be taken from these reference points but rather from the taken from these reference points but rather from the linguogingival margin of the teeth, since erroneous linguogingival margin of the teeth, since erroneous measurements can occur in case of tooth rotationmeasurements can occur in case of tooth rotationFrom a diagnostic point of view assessment of the transverse From a diagnostic point of view assessment of the transverse symmetry is clinically relevant, particularly in cases of symmetry is clinically relevant, particularly in cases of transverse malocclusionstransverse malocclusions

Inference -:Inference -:Symmetry/asymmetric width development between right and Symmetry/asymmetric width development between right and left sides of the arch (malposition, symmetric, asymmetric, left sides of the arch (malposition, symmetric, asymmetric, unilateral)unilateral)


Midline shift: Midline shift: Midline is shifted in maxillary arch when the Midline is shifted in maxillary arch when the contact point of the mesial approximal surfaces of contact point of the mesial approximal surfaces of the upper central incisors don't coincide with the the upper central incisors don't coincide with the midsagittal plane of the upper arch.midsagittal plane of the upper arch.Differentiation between dental and skeletal midline Differentiation between dental and skeletal midline shift in mandible arch shift in mandible arch The anterior skeletal midpoint of the mandible is The anterior skeletal midpoint of the mandible is either determined with the help of the mental spine either determined with the help of the mental spine view or by assessing the point of insertion of the view or by assessing the point of insertion of the lingual frenum. But the radiographic method is lingual frenum. But the radiographic method is most reliable.most reliable.


Analysis of anteroposterior Analysis of anteroposterior symmetrysymmetry

The analysis serves to diagnose first and foremost any The analysis serves to diagnose first and foremost any mesial tooth drift.mesial tooth drift.Asymmetric mesio-distal tooth position of corresponding Asymmetric mesio-distal tooth position of corresponding teeth in the right and left side of the dental arches.teeth in the right and left side of the dental arches.In practice this involves drawing a line parallel to the In practice this involves drawing a line parallel to the Tuberosity plane, which runs through the posterior surface Tuberosity plane, which runs through the posterior surface of distal-most first molar, and comparing the sagittal of distal-most first molar, and comparing the sagittal distances of the individual posterior teethdistances of the individual posterior teeth

Inference -:Inference -:If there is no right-left asymmetry, the teeth are correctly If there is no right-left asymmetry, the teeth are correctly positioned or there has been symmetric mesial migration.positioned or there has been symmetric mesial migration.Asymmetry of a transverse arch form may result in a Asymmetry of a transverse arch form may result in a relative mesial position of the more buccaly placed teethrelative mesial position of the more buccaly placed teeth


Palatal height index (P.H.I.)Palatal height index (P.H.I.)According to Korkhaus palatal height is defined as a vertical line According to Korkhaus palatal height is defined as a vertical line perpendicular to the mid palatal raphe, which runs from the surface of the perpendicular to the mid palatal raphe, which runs from the surface of the palate to the level of the occlusal plane.palate to the level of the occlusal plane.This is measured between the reference point of the Ponts index for the This is measured between the reference point of the Ponts index for the posterior width.posterior width.

P.H.I. = palatal height x 100/posterior arch widthP.H.I. = palatal height x 100/posterior arch widthMeasurement of palatal height -: using Korkhaus 3-dimensional Measurement of palatal height -: using Korkhaus 3-dimensional orthodontic divider, the palatal height can be measured as well as orthodontic divider, the palatal height can be measured as well as posterior arch width.posterior arch width.Palatal height is measured in the midsagittal plane in the region of the Palatal height is measured in the midsagittal plane in the region of the upper first molar on the level of occlusal planeupper first molar on the level of occlusal plane

Inference-:Inference-:

Average value is 42% Average value is 42% Value is increased when the palatal vault relative to the transverse arch Value is increased when the palatal vault relative to the transverse arch development is high and decreased when palate is shallow.development is high and decreased when palate is shallow.


Analysis in vertical planeAnalysis in vertical planeSupraversion – over eruption of teeth in relation to the Supraversion – over eruption of teeth in relation to the occlusal plane occlusal plane Infraversion – under or insufficient eruption of teeth in Infraversion – under or insufficient eruption of teeth in relation to occlusal plane relation to occlusal plane Occlusal plane is a constructed plane which does not Occlusal plane is a constructed plane which does not actually exist, as the occlusal surfaces of teeth do not lie actually exist, as the occlusal surfaces of teeth do not lie on one plane. Therefore precise measurements cannot be on one plane. Therefore precise measurements cannot be made. Occlusal plane is defined as the tangent which made. Occlusal plane is defined as the tangent which runs through the tips of the mesio-buccal cusps of first runs through the tips of the mesio-buccal cusps of first molars and the buccal cusps of the premolars.molars and the buccal cusps of the premolars.Curve of spee – the depth of the curve of spee is defined Curve of spee – the depth of the curve of spee is defined as the distance from the vertex of the curvature to the as the distance from the vertex of the curvature to the side of a plastic template placed over the lower arch. The side of a plastic template placed over the lower arch. The template touches anteriorly the incisal edges and template touches anteriorly the incisal edges and posteriorly the distal-most molar cusps posteriorly the distal-most molar cusps


To determine the amount required To determine the amount required to the curve of spee of spaceto the curve of spee of space

Balridge formulaBalridge formula space required to level the arch = space required to level the arch =

(Rt. Side depth + Lt. side depth / 2)+0.5 (Rt. Side depth + Lt. side depth / 2)+0.5


Bolton’s analysisBolton’s analysisDetermines the tooth size discrepancy between maxillary and Determines the tooth size discrepancy between maxillary and mandibular teethmandibular teethSum of mandibular 12 – the mesio-distal width of all the teeth Sum of mandibular 12 – the mesio-distal width of all the teeth mesial to the mandibular second permanent molars is measured mesial to the mandibular second permanent molars is measured and summed up.and summed up.Sum of maxillary 12 – the mesio-distal width of all the teeth Sum of maxillary 12 – the mesio-distal width of all the teeth mesial to the maxillary second permanent molars is measured mesial to the maxillary second permanent molars is measured and summed up.and summed up.Sum of mandibular 6 - the mesio-distal width of all the teeth Sum of mandibular 6 - the mesio-distal width of all the teeth mesial to the mandibular first premolars is measured and mesial to the mandibular first premolars is measured and summed up.summed up.Sum of maxillary 6 – the mesio-distal width of all the teeth mesial Sum of maxillary 6 – the mesio-distal width of all the teeth mesial to the maxillary first premolars is measured and summed up.to the maxillary first premolars is measured and summed up.

Overall ratio = sum of mandibular 12 x100 / sum of maxillary 12Overall ratio = sum of mandibular 12 x100 / sum of maxillary 12

Anterior ratio = sum of mandibular 6 x100 / sum of maxillary 6Anterior ratio = sum of mandibular 6 x100 / sum of maxillary 6


Inference-:Inference-:

If overall ratio is less than 91.3%, it indicates If overall ratio is less than 91.3%, it indicates maxillary tooth material excessmaxillary tooth material excessIf overall ratio is more than 91.3%, it indicates If overall ratio is more than 91.3%, it indicates mandibular tooth material excessmandibular tooth material excessIf anterior ratio is less than 77.2%, it indicates If anterior ratio is less than 77.2%, it indicates maxillary anterior tooth material excessmaxillary anterior tooth material excessIf anterior ratio is more than 77.2%, it indicates If anterior ratio is more than 77.2%, it indicates mandibular anterior tooth material excessmandibular anterior tooth material excess


Analysis of apical baseAnalysis of apical baseAshley howe’s analysisAshley howe’s analysis

Determines whether the deficiency in arch width or arch length Determines whether the deficiency in arch width or arch length

Determination of total tooth material (T.T.M.) –the mesio-distal width of 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 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 help of dividers and all the values are summed up. This is called as total tooth material total tooth material

Determination of premolar diameter (P.M.D.) –the premolar diameter 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 refers to the arch width from the tip of the buccal cusp of opposite first premolar premolar

Determination of premolar basal arch width (P.M.B.A.W.) the canine Determination of premolar basal arch width (P.M.B.A.W.) the canine fossa is found distal to canine eminence. The measurement of the 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 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 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 the measurement is made from a point that 8mm below the crest of interdental papilla distal to the canineinterdental papilla distal to the canine


InferenceInference -: -:

P.M.B.A.W.% = P.M.B.A.W. x100 / T.T.MP.M.B.A.W.% = P.M.B.A.W. x100 / T.T.MIf P.M.B.A.W% is 37% or less, it indicates If P.M.B.A.W% is 37% or less, it indicates extraction caseextraction caseIf P.M.B.A.W% is 44% or more, it indicates If P.M.B.A.W% is 44% or more, it indicates non-extraction casenon-extraction caseIf P.M.B.A.W% is 37-44%, borderline case If P.M.B.A.W% is 37-44%, borderline case


Space analysis in permanent Space analysis in permanent dentitiondentition

Determine the difference between space available and space Determine the difference between space available and space required for alignment of teethrequired for alignment of teeth

Nance and Carey’s analysis Nance and Carey’s analysis

Determination of tooth material -:Determination of tooth material -:

measure the mesio-distal width of each tooth mesial to the first measure the mesio-distal width of each tooth mesial to the first permanent molar . The sum total of the width corresponds to the permanent molar . The sum total of the width corresponds to the necessary space required i.e. ideal arch length.necessary space required i.e. ideal arch length.


Determination of arch length -:Determination of arch length -:

measure the actual arch length using soft brass wire. measure the actual arch length using soft brass wire. The wire is placed contacting the mesial surface of the The wire is placed contacting the mesial surface of the first permanent molar of one side and is passed over first permanent molar of one side and is passed over the buccal cusps of premolar and along the anteriors the buccal cusps of premolar and along the anteriors and is continued on the opposite side in same way and is continued on the opposite side in same way upto the mesial surface of the opposite first molar upto the mesial surface of the opposite first molar If proclined anteriors, the wire is passed along the If proclined anteriors, the wire is passed along the cingulum of anterior teeth cingulum of anterior teeth If retroclined anteriors, the wire is passed over the If retroclined anteriors, the wire is passed over the incisal edge of anteriorsincisal edge of anteriors

Determination the arch length discrepancy -:Determination the arch length discrepancy -:The discrepancy refers to the difference between the The discrepancy refers to the difference between the arch length and tooth material arch length and tooth material



If ideal arch length is more than actual If ideal arch length is more than actual then negative value and space deficiency, then negative value and space deficiency, extraction is required in that case extraction is required in that case

If space available is more than ideal arch If space available is more than ideal arch length then positive value and space length then positive value and space excess, no extraction is required in that excess, no extraction is required in that case case


The Lundstorm segmental analysisThe Lundstorm segmental analysisSegmental analysis involves an indirect assesment of Segmental analysis involves an indirect assesment of the dental arch perimeter which can be carried out in the dental arch perimeter which can be carried out in following manner-:following manner-:Division of the dental arch into six straight line Division of the dental arch into six straight line segments of two teeth per segment, including the first segments of two teeth per segment, including the first permanent molars.permanent molars.Measure the mesio-distal width of twelve teeth Measure the mesio-distal width of twelve teeth Summing the individual tooth width of each segment.Summing the individual tooth width of each segment.Measure the available mesio-distal space on the study Measure the available mesio-distal space on the study cast separately for each segmentcast separately for each segment

The sum of the difference between ideal and actual The sum of the difference between ideal and actual length of each segment express the space relationshiplength of each segment express the space relationship


Peck and Peck indexPeck and Peck indexPeck and peck determined the presence or absence of Peck and peck determined the presence or absence of lower incisor crowding and related to the shape of lower lower incisor crowding and related to the shape of lower anterior teeth.anterior teeth.It is based on the finding that individuals with ideal incisal It is based on the finding that individuals with ideal incisal arrangement had smaller mesio-distal width and larger arrangement had smaller mesio-distal width and larger labio-lingual width than in persons with incisal crowdinglabio-lingual width than in persons with incisal crowding

Method -:Method -:1.1. Measure the mesio-distal width of lower incisorsMeasure the mesio-distal width of lower incisors2.2. Measure the labio-lingual width of lower incisor individuallyMeasure the labio-lingual width of lower incisor individually3.3. Calculate the ratio of mesio-distal width and labio-lingual Calculate the ratio of mesio-distal width and labio-lingual

width separately for lower centrals and lateralswidth separately for lower centrals and laterals4.4. Compare the value with ideal mean valueCompare the value with ideal mean value

Ideal mean values -: Ideal mean values -: For lower centrals -: 88-92%For lower centrals -: 88-92%For lower laterals -: 90-95%For lower laterals -: 90-95%



If calculated value is greater than mean If calculated value is greater than mean value then mesio-distal width is more than value then mesio-distal width is more than labio-lingual width. labio-lingual width. Hence proximal stripping can be done to Hence proximal stripping can be done to relieve the crowdingrelieve the crowding


Mixed dentition analysisMixed dentition analysis

The purpose is to evaluate the amount of space available in the The purpose is to evaluate the amount of space available in the arch for succeeding permanent teeth and necessary occlusal arch for succeeding permanent teeth and necessary occlusal adjustments.adjustments.Many methods of mixed dentitions analysis have been Many methods of mixed dentitions analysis have been suggested; however, all fall into two strategic categories:suggested; however, all fall into two strategic categories:

1. Those in which the sizes of unerupted cuspids and bicuspids 1. Those in which the sizes of unerupted cuspids and bicuspids are estimated from measurements of the radiographic image , are estimated from measurements of the radiographic image , andand

2.Those in which the sizes of the cuspids and premolars are 2.Those in which the sizes of the cuspids and premolars are derived from knowledge of the sizes of permanent teeth already derived from knowledge of the sizes of permanent teeth already erupted in the mouth.erupted in the mouth.


The correlation between the sizes of mandibular The correlation between the sizes of mandibular incisors and the combined sizes of cuspids and incisors and the combined sizes of cuspids and bicuspids in either arch is high enough to predict the bicuspids in either arch is high enough to predict the amount of space required for the unerupted teeth amount of space required for the unerupted teeth during space management procedures. during space management procedures. The mandibular incisors have been chosen for The mandibular incisors have been chosen for measuring, since they are erupted into the mouth early measuring, since they are erupted into the mouth early in the mixed dentition, the mandibular incisors are not in the mixed dentition, the mandibular incisors are not used in any of predictive procedures, since they show used in any of predictive procedures, since they show too much variability in size, and their correlations with too much variability in size, and their correlations with other groups of teeth are of lower predictive value. other groups of teeth are of lower predictive value.


Moyer’s mixed dentition AnalysisMoyer’s mixed dentition AnalysisProcedure - :Procedure - :

1. Measure with the tooth-measuring gauge or a pointed 1. Measure with the tooth-measuring gauge or a pointed Boley’s gauge, the greatest mesio-distal width of the Boley’s gauge, the greatest mesio-distal width of the four mandibular incisors.four mandibular incisors.2. Determine the amount of space needed for alignment 2. Determine the amount of space needed for alignment of the incisors. Set the Boley’s gauge to the left central of the incisors. Set the Boley’s gauge to the left central incisor and left lateral incisor. Place one point of the incisor and left lateral incisor. Place one point of the gauge at the midline of the alveolar crest between the gauge at the midline of the alveolar crest between the central incisors and let the other part lie along the line of 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 the dental arch on the left side. mark on the tooth or the cast the precise point where the distal surface of the cast the precise point where the distal surface of the lateral incisor will be when it has aligned. Repeat this lateral incisor will be when it has aligned. Repeat this process for the right side of the arch.process for the right side of the arch.


3. Compute the amount of space available after incisor alignment. 3. Compute the amount of space available after incisor alignment. To do this, measure the distance from a point marked in the line of 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 the arch to the mesial surface of first permanent molar. This distance is the space available for cuspid and two bicuspids and for distance is the space available for cuspid and two bicuspids and for any necessary molar adjustment after the incisor have been aligned. any necessary molar adjustment after the incisor have been aligned. Record the data for both sides on the mixed dentition analysis form.Record the data for both sides on the mixed dentition analysis form.

4. Predict the size of the combined widths of mandibular cuspids 4. Predict the size of the combined widths of mandibular cuspids and bicuspids. Prediction of the combined widths of cuspid, first and and bicuspids. Prediction of the combined widths of cuspid, first and second bicuspids is done by use of probability charts. Locate in the second bicuspids is done by use of probability charts. Locate in the left column of the mandibular chart value that most nearly left column of the mandibular chart value that most nearly corresponds to the sum of the widths of the four mandibular incisors. 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 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 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 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 chosen as the estimate , since it has been found to be the most practical from clinical standpoint. practical from clinical standpoint.


Tanaka and Johnson analysisTanaka and Johnson analysisPrediction of the size of unerupted canines Prediction of the size of unerupted canines and premolars can be doneand premolars can be doneThey simplified Moyers 75 percent level of They simplified Moyers 75 percent level of the prediction table into a formulathe prediction table into a formulaPredicted width of maxillary canine and Predicted width of maxillary canine and premolar = sum of mandibular incisors + premolar = sum of mandibular incisors + 11 divided by 211 divided by 2Predicted width of mandibular canine and Predicted width of mandibular canine and premolar = sum of mandibular incisors + premolar = sum of mandibular incisors + 10.5 divided by 210.5 divided by 2


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Model Analysis 1 / orthodontic courses by Indian dental academy