Model Analysis

By,

DR KARAN PUROHIT

DEPT OF ORTHODONTICS

M.S.R.D.C.

contentsIntroduction on Study models

Study model analysis

Pont’s analysisLinderharth analysisKorkhaus[ ant. dental arch length] analysisKorkhaus[ palatal ht.]analysisAshley howe’s analysisBolton’s analysis

Nance analysisCarey’s Arch perimeter analysis Lundstorm analysisPeck& peck analysisLittle’s irregularity index

Mixed dentition analysis--Huckaba’s analysisMoyer’sTanaka &johnstonNance analysis hixon oldfather

Total space analysis

Merrifield

Tweed analysis

Computerized Digital Model Analysis

E-models

Orthocad Technology

Conclusion

References

STUDY MODEL

DEFINITION

• Positive reproductions of the maxillary and

mandibular dental arches and alveolar processes,

including the hard palate, mucobuccal, mucolabial,

sublingual folds and associated muscle and

frenum attachments.

Orthodontic study models are essential diagnostic records, which help to study dentition and occlusion from all three dimensions.

Purpose of Making Study Models

1. It is a valuable aid in planning treatment as they are three-dimensional records of patients dentition.

2. Occlusion can be visualized from all aspects.

3. Provide a permanent record of the intermaxillary relationships and the occlusion at the start of therapy..

4. Help us to monitor changes taking place during tooth movements.

5. Helps to motivate the patients as they can visualize the treatment progress.

6. They are needed for comparison purposes at the end of treatment and act as a reference for post treatment changes.

7. In case the patient has to be transferred to another clinician , study models are an important record.

Objectives of Ideal orthodontic Study Models

Parts of the

S tudy Models

ARTISTIC PORTION

ANATOMIC PORTION

ARTISTIC PORTION

In a well fabricated set of study models the ratio of the anatomic portion to artistic portion should be

3:1

artistic

anatomic

Study model (Study Cast) analysis Study model (Study Cast) analysis

is a three-dimensional assessment of the maxillary

and mandibular dental arches and the occlusal

relationships.

Space availability & requirementTooth size – arch width discrepancyTooth size – arch length discrepancyu/l tooth size discrepancyTooth shape discrepancyEstimation of size of unerupted teeth

ADVANTAGESADVANTAGES

DISADVANTAGES DISADVANTAGES

Model analysis is not correlated with other important diagnostic criteria such as cephalograms and panoramic radiographs.

In model analysis actual value of the individual case is compared with the standard values of the ‘Normal arch’. With present day knowledge, this method is often considered to have minimal diagnostic value.

Pont’s Index

Sum of Incisors- anterior and Posterior arch width

In 1909 Pont devised a method of predetermining an “ideal” arch width based on the mesiodistal widths of the crowns of the maxillary incisors.

Pont suggested that the ratio of combined incisors to transverse arch width (as measured from the centre of the occlusal surface)was ideally 0.8 in bicuspid area and 0.64 in first molar area.

The maxillary arch be expanded 1 to 2mm more during treatment than his ideal to allow for relapse.

Sum of upper Incisors (SI u):

The maximal mesiodistal width of each maxillary incisor is measured and the single values are added together.

Anterior and posterior arch width

Reference points: Maxilla anterior:

Lower-most point of the transverse fissure of the first premolar (distal pit)

Maxilla posterior :

Point of intersection of the transverse fissure with the buccal fissure of the first permanent molar (mesial pit)

Determination of the ideal values of the anterior and posterior arch width from the Pont index formula:

Ideal value for anterior arch width (at premolars)

= SI X100

80

Ideal value for posterior arch width (at molars)

= SI X100

64

Pont’s analysis helps in determining

Dental arch is narrow or normalNeed for lateral arch expansionHow much expansion is possible at PM and molar

area.

The deviation in the transverse development of the arch width is represented by the difference between the actual and the standard (calculated) values.

If the actual value is greater than calculated normal value, the arch is wider for the sum of incisor width and no scope for expansion.

If the actual value is less than calculated normal value then the arch is narrow for the sum of incisor width and there is scope for expansion

Drawback’s of Pont’s analysis:

Pont has carried out his study on French population. So the standard can not be taken for granted for other population.

All his measurements and predictions were related to the maxillary dental arch only.

Sum of upper incisors can be variable e.g. peg laterals, so inference can be misleading.

Tonn formula(SI L):-If upper central or lateral

incisors are missing, determinations may be made based on the sum of the lower incisor width using the Tonn Formula for all four upper incisors which calculates the approximate width.

Tonn FormulaSI u= SI L X 4 + 0.5

3

Correlation table between the sum of upper incisors and dental arch width

Table of mean values for arch width assessment according to different investigators (Weise and Benthake, 1965)

Pont’s Index as applied on Indians: D.S.Gupta et al: Angle Orthodontist: Vol: 49: No:4, Oct 1979

One hundred dental models of normal occlusion was evaluated to check the reliability of Pont’s Index on a Indian population.

Premolar index and molar index were found to be 81.66 and 65.44 as compared with Pont’s original 80 and 64.

Linder Harth Index

Similar to Pont-Index

He made a variation in the formula to determine the calculated premolar and molar value (Rhine-land population)

Ideal value anterior arch width = SI u X 100

85

Ideal value posterior arch width = SI u X 100

65

Korkhaus Analysis

Anterior Dental Arch Length

Perpendicular distance from the most anterior labial surface of the central incisors to the connecting line of the reference points of the anterior width in the midsagittal plane.

L U: maxilla, L L : mandible

measurements reveal anteroposterior malpositioning of the anterior teeth.

L U and L L - not only altered by malpositioning of the anterior teeth, but also by migration of first premolars.

Correlation between maxillary and mandibular arch lengths

Standard Value L L = standard value L u -2mm

Anterior arch length of the mandible (LL) is shorter than the maxillary arch length (L u) by labiolingual width of the incisal edge of the upper central incisor.

Correlation table between SI u and L u

Korkhaus (1938): Formula for calculating the standard value of the upper anterior arch length

L u = SI u X 100

160

SI u 27 27.5 28 28.5 29 29.5 30 30.5 31 31.5 32 32.5 33 33.5 34 34.5 35 35.5 36

Korkhaus 16 16.3 16.5 16.8 17 17.3 17.5 17.8 18 18.3 18.5 18.8 19 19.3 19.5 19.8 20 20.5 21

Weise 16.4 16.6 16.8 17 17.2 17.4 17.6 17.8 18 18.2 18.4 18.6 18.8 19 19.2 19.4 19.6

19.8 20

Brune 16.6 16.8 16.9 17.1 17.2 17.3 17.5 17.6 17.8 17.9 18 18.2 18.4 18.6 18.7 18.8 18.9

19 19.2

Interpretation of measurements of anterior arch length

Finding Anterior arch length

Bilateral mesioversion of posterior teeth L u / L L shortened

Linguoversion of anterior teeth L u / L L shortened

Labioversion of anterior teeth L u / L L increased

Bimaxillary dental protrusionL u + L L increased

Distoversion of premolars L u / L L increased

Mandibular prognathism L L increased

In 1939

Evaluates palatal shape acc. to index..

Vertical line perpendicular to the midpalatal raphae which runs from the surface of the palate to the level of occlusal plane .

Measured between the reference points of the Pont-Index for posterior teeth.

Palatal height is defined as the distance of perpendicular from connecting line between the midpoint of the fissure of both Upper 1st molars to the surface of palate.

[3 dimensional orthodontic divider]

Palatal height index= Palatal height X 100

Posterior arch width

Average index value- 42%

> when the palatal vault relative to the transverse arch development is high,

< when the palate is shallow.

Ashley Howes’ Analysis

Ashley Howe considered tooth crowding to be due to deficiency in arch width .

Relationship between the total width of the MD diameters of the teeth anterior to the 2nd permanent molars & the width of the dental arch in the 1st PM region.

It is a Formula for determining whether the apical bases could accommodate the patient’s teeth.

PROCEDURE

Refers to sum of the

mesiodistal width of

the teeth from first

molar to first molar

TTM:- Total Tooth Material

PMD:- Premolar Diameter

arch width

measured from the

buccal cusp tips of

the first premolar

on one side to the

buccal cusp tip on

other side

PMBAW:-Premolar basal ach Width

measured from the root

apices of the first premolar

on one side to the first

premolar on other

side(CANINE FOSSA TO

CANINE FOSSA)

Howe believed that the PMBAW(he called it the canine fossa diameter) should equal approximately 44% of the mesiodistal width of the 12 teeth in the maxilla if it is to be sufficiently large to accommodate all the teeth.

When the ratio of PMBAW/TM is less than 37%, Howe considered this to be a basal arch deficiency necessitating extraction of premolars.

If the PMBAW is greater than premolar coronal arch width (PMBAW > PMD) expansion of the premolar can be undertaken safely whereas expansion is contraindicated if PMBAW < PMD.

Thus Howe’s analysis is useful in planning treatment of problems with suspected apical base deficiencies and deciding whether to Extract teeth Widen the dental arch Or expand rapidly the palate

Howe’s analysis is more logical and superior to the Pont’s index as it is applicable to each arch and and is widely used.

Bolton Analysis

(Wayne A Bolton, 1958)

Bolton studied the interarch effects of discrepancies in tooth size to devise a procedure for determining the ratio of

1.Total mandibular versus Total maxillary tooth size and

2. Anterior mandibular versus Anterior maxillary tooth size.

Study of these ratios helps in:

Estimating the overbite and overjet relationships that will likely be obtain after treatment is finished.

Effects of contemplated extractions on posterior occlusion and incisor relationships.

Identification of occlusal misfit produced by interarch tooth size incompatibilities.

Overall Ratio = Sum of mandibular “12” X 100

Sum of maxillary “12”

A mean ratio of 91.3 will result in ideal overbite and overjet relationships, as well as posterior occlusion.

Overall Ratio > 91.3 : Difference between the actual and desired mandibular measurement is the amount of excessive mandibular tooth material.

Overall Ratio < 91.3 : Difference between actual maxillary size and desired maxillary size is the amount of excess maxillary tooth material.

If overall ratio is less than 91.3%

indicate maxillary tooth material excess….

amount of max. excess is determined using the formula

max.12 -- mand.12 × 100

91.3

if overall ratio is more than 91.3%

indicate mand. Tooth material excess

Amt of mand excess determined by formula

Mand 12 -- max.12 × 91.3

100

Anterior Ratio = Sum of mandibular “6” X 100

Sum of maxillary “6 A mean ratio of 77.2 will provide ideal overbite and

overjet relationships, if the angulation of the incisors is correct and if the labiolingual thickness of the incisal edges is not excessive.

Anterior ratio > 77.2 : There is excessive mandibular tooth material.

Anterior ratio < 77.2 : There is excessive maxillary tooth material.

Table of average values for overall and anterior ratio

Limitations:

Bolton analysis is applicable only to permanent dentition. Bolton Analysis predictions do not take in to account

the sexual dimorphism, particularly with maxillary cuspid widths.

Since maxillary cuspids are disproportionately larger in men than in women and ideal overbite and overjet, as defined by Bolton is less apt to be achieved in men.

Space Analysis

To quantify the amount of crowding within the arches since the treatment varies depending on the severity of the crowding.

Principle : Since malaligned and crowded teeth usually result from lack of space, this analysis is primarily of space within the arches.

It requires a comparison between the amount of space available for the alignment of crowded teeth and amount of space required to align them properly.

Analysis can be done directly on the dental casts.Analysis can be done by 2 methods—

1.nance& carey analysis

2.lundstrom segmental analysis

The Nance and Carey’s Analysis :

Arch length discrepancy.

Originally Nance (1947) described a method of determining mandibular arch length in mixed dentition.

Later in 1949 Carey modified Nance’s method for permanent dentition. This analysis is usually done in lower arch.

The same analysis when carried out in upper arch is

called as Arch Perimeter analysis.

Recording the mesiodistal width of each tooth mesial to the first permanent molar.

The sum total width corresponds to the necessary space required (ideal dental arch length).

The actual length is measured with the aid of a soft brass wire.

This is contoured to the individual arch shape and placed on the occlusal surfaces over the contact points of the posterior teeth and the incisal edges of the anteriors.

The brass wire should be passed along the cingulum of the anterior teeth if anteriors are proclined and along the labial surface if anteriors are retroclined.

The distance between the mesial contact points of the first permanent molars(recorded from the straightened wire) is the amount of space available in the dental arch (actual arch length

The assessment of space relationship is the result of the difference between the ideal and actual arch length.

Negative value = space deficiency. Positive value = space excess.

If the arch length discrepancy is 0 to 2.5mm :- Proximal stripping can be carried out to reduce

the minimal tooth material excess. 2.5 to 5mm :- Extraction of second premolar is indicated. Greater than 5mm :- Extraction of first premolar is usually

indicated.

The Lundstorm Segmental Analysis

Indirect assessment of dental arch perimeter Division of the dental arch in to six straight line segments

of two teeth per segment, including first permanent molars.

Recording the mesiodistal width of the twelve teeth.

Summing the individual tooth width of each segment.

The available mesiodistal space on the study cast separately for each segment is recorded.

sum of the differences between ideal and actual length of each segment expresses the space relationship.

Peck and Peck Index

Peck and Peck presented data which indicated that the presence or absence of lower incisor crowding was related to the shape of the lower anterior teeth.

It is based on the finding that individuals with ideal incisal arrangement had smaller mesiodistal width and larger labiolingual width than in persons with incisal crowding.

Measure the MD width of lower incisor individually

Measure the FL width of lower incisors individually.

The Peck and Peck index is calculated by the formula:

MD mandibular incisor crown width mm × 100

FL mandibular incisor crown width mm

This Index is calculated separately for lower centrals and laterals and compared with ideal mean values and expressed in %.

Ideal mean values : Lower Centrals: 88-92% Lower Laterals: 90-95%.

If the calculated value is greater than the mean value, then it is suggestive that MD width is more than FL width.

Hence proximal stripping can be indicated to relieve crowding and there by alter the ratio so that it is in favourable range.

The irregularity index

• 1Robert.m little [1975]• A quantitative score of mandibular anterior alignment

• the linear displacement of the anatomic contact point is measured and the sum of these five displacements is calculated which represents the relative degree of anterior irregularity.

Material and methods

Dial caliper calibrated to at least tenth of a mm

.

Mandibular casts

Measurements are obtained directly from the mandibular cast.

Caliper is held parallel to the occlusal plane.Each of the five measurements represents a horizontal

linear distance between the anatomic point of the adjacent teeth.

Each cast was subjectively ranked on a scale ranging from 0-10

0 perfect alignment 1-3 minimal irregularity 4-6 moderate irregularity 7-9 severe irregularity10 Very severe irregularity

MIXED DENTITION ANALYSIS

determine the difference between space available and space required for the unerupted permanent canines and first and second premolars.

supporting zone-- distance between the distal surface of the permanent lateral incisor and the mesial surface of the first permanent molar.

Comprises of deciduous canines and the first and second deciduous molars.

Moyers Mixed Dentition Analysis (1967)

Prediction from Proportionality TablesLower incisors are measured to predict the size of upper as

well as lower posterior teethErupt early into the mouth in the mixed dentition. Easily measured accurately.

The maxillary incisors are not used in any of the predictive procedure since they show too much of variability in size and their correlations with other group of teeth.

Procedure --

Measure the greatest mesiodistal width of each of the four mandibular incisors with tooth measuring gauge or a pointed Boley gauge.

Record these values in mixed dentition analysis form.

Determine amount of space needed for alignment of the incisors:

Set the Boley gauge to a value equal to sum of the widths of left central and lateral incisors.

Place one point of the gauge at the midline of the alveolar crest between the central incisors and let other point lie along 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 been aligned.

Repeat the process for the right side of the arch.

Compute the amount of space available after incisor alignment to,, do this

measure the distance from the point marked in the line of the arch to the mesial surface of the first permanent molar. Record the data for both sides.

This distance is a space available for the cuspid and two bicuspids .

Measurement of supporting zones

Prediction of size of combined width of the mandibular cuspid and bicuspid:

Done by using probability charts. The value at 75% level is chosen as the estimate, since it has been found to be the most practical from a clinical standpoint.

Record these values for both the sides and each arch.

Compute the amount of space left in the arch for molar adjustment by subtracting the estimated cuspid and bicuspid size from the measured space available in the arch after alignment of incisors.

Record these values for each side.

Mixed Dentition Analysis Form

Method of Localization of Space needs in the mixed Dentition

Probability tables for Predicting the Sizes of Unerupted Cuspids and Bicuspids

• The predicted tooth size of 3,4 and 5 is compared with the arch length available for them to determine the discrepancy

• If the predicted value is greater crowding of the teeth can be expected.

Tanaka and Johnston AnalysisTanaka and Johnston prediction values

One half of the mesiodistal width of the four lower incisors

+10.5mm =

Estimated width of mandibular canine and premolars in one quadrant

+11.0mm =

Estimated width of maxillary canine and premolars in one quadrant

Advantage: Does not require radiographs and reference tables.

Drawback: Method is less accurate for populations other than European.

The mesio-distal width of the mandibular central and lateral incisor is obtained from the casts.

Determine the width of the un-erupted premolars from the intra-oral peri-apical radiographs .

Hixon and Oldfather’s method—

Add the width of central and lateral incisors with the width of un-erupted premolars of that particular side.

The estimated sum total width of the cuspids and bicuspids of that particular side can be obtained from the given chart

Every measured sum width of incisors and bicuspids has a corresponding sum width of the cuspids and bicuspids in the chart.

Measured values in mm.Measured values in mm. Estimated tooth size in mm.Estimated tooth size in mm.

2323 18.418.4

2424 19.019.0

2525 19.719.7

2626 20.320.3

2727 21.021.0

2828 21.621.6

2929 22.322.3

Combined Radiographic-Prediction Table Method

The method of Hixon and Oldfather(1956), modified by Staley and Kerbers(1980) is restricted to the analysis of supporting zone in the mandible.

Measurement of size of unerupted first and second premolars in one mandibular quadrant from a periapical radiograph.

Determination of mesiodistal tooth width of the lower central and lateral incisors on the study cast corresponding to the side of the radiograph.

After adding together both figures, the probable width of the permanent canine, first and second premolars for the corresponding quadrant can be read off in the prediction graph under the column of sum total.

Chart for combined radiographic-prediction table method Prediction Graph

X-axis: Sum of mandibular incisor width measured on the dental cast and the total width of the first and second premolars measured on the periapical radiograph. Y-axis: Predicted total width of permanent mandibular canine, first and second premolars.

Huckaba’s analysis.Both study models as well as radiographs are used for

determining the width of un-erupted tooth.

With radiograph, it is necessary to compensate for the enlargement of the radiographic image.

This can be done by measuring an object that can be seen both on radiograph and and on the study model, such as a primary molar tooth.

After the measurement, a proportional relationship can then be established as follows:

Actual width of primary molar(X1) = Apparent width of primary molar(X2) Actual width of unerupted premolar(Y1) Apparent width of unerupted premolar(Y2)

Or Y1= X1×Y2. X2 This technique can be used for all ethnic groups.

Nance analysis

Amount of space required

width of the erupted four mandibular permanent incisors are measured.

width of unerupted mandibular canines, first and second premolars on the radiographs are measured.

Amount of space available

A piece of .026 inch brass ligature wire is placed on the lower cast extending from the mesial surface of the first permanent molar on one side of arch to the mesial surface of the first permanent molar on the opposite side.

wire should pass over the buccal cusp of the posterior teeth and the incisal edges of anterior teeth.

Two measurements are compared .

Total space analysis

CONVENTIONAL METHODSpace required-Four mand. Incisors-greatest MD dia. measured. MD width of Unerupted canines & PM’s [ on R/f] All addedSpace available-Carey’s AND arch perimeter

Discrepancy found

Tweed method;-Here the values for space required and space available were

obtained from conventional method.Assessment of relation b/w axial inclination of mandibular

Incisors & basal bone made on tracing of lateral cephalogram.

Amt. of alveolodental protrusion or retrusion assessed & incorporated in analysis.

Tweed established foll. Relationships—

When FMA [21 -29], FMIA shud be [68 ]

When FMA [30 or >],FMIA shud be [65]

When FMA [20 or<] IMPA shud not exceed [92]

If for a specific FMA , FMIA did not correspond,

an objective line was traced to form the required FMIA..

Distance btw this objective line & line that passed thru the actual axial inclination of the mand. Incisors measured vid calipers..

This figure multiplied by 2 to include rt & lt sides.

This was then added to diff. btw space required & space available to yield total discrepancy..

Total space analysisDivided into 3 areas—Anterior area & Middle area& Posterior area

Anterior area—Measurmnt of mand incisors on cast & canine 4rm R/F.

Cephalometric correction as per Tweed method

Here, the cephalometric correction done by

Actual FMIA [in degrees],subtracted from proposed angle

and The diiference was multiplied by constant (0.8) to give difference in mm.

Soft tissue modification—Measure ‘Z’ angle of merrifield & add ceph correction to it.If z angle> 80,mand incisor inclination modified[IMPA92]IF angle<75, additional uprighting of mand. IncisorsUpper lip thickness was measured[vermillion bordr to

greatest curvature of labial surf. Of C.I.Total chin thickness measured[soft tissue chin to NB line]If lip thickness >chin thickness difference was determined

× 2 & dis added to space requiremntIf lip thickness was less or equall to chin thickness no soft

tissue modification was done done..

Middle area—Tooth measurement is done by adding MD width of perm

mand. 1st molar, to measurement of PM’s [r/f] Curve of occlusion — Space req to level the mand curve of occlusion which is

determind by using Flat object placed on occ surfaces of mand teeth contacting 1st perm molars & incisors..

Deepest pt. btw this flat surf & occ surf of primary molars was measured. Formula to evaluate curve of occlusion

Rt side depth+lt side depth +0.5

2

All added to tooth measurement to complete space required..

Posterior area—Space required—Sum of MD of two 2nd & 3rd molars[if unerpted, r/f]

If 3rd molars not visible on R/F, then wheeler’s measurement used---

x= y- x’ y’X= estimated value of perm mand. 3rd molarX’ = wheeler’s value for 3rd molarY=actual size of the 1st perm molar on the castY’=wheeler’s value for 1st molar.

SPACE AVAILABLE—Brass wire method in all 3 areasAnterior area— place brass wire from MB of primary 1st

mand. Molar to opposite molar,wire is straightened & measured with caliper.

Middle area—2 wires used ,MB of primary 1st molar to DB of the permanent 1st molar.

Posterior area—space available consisted of space presently available & estimated

increase or prediction.Estimated increase was 3 mm per year[1.5 mm side] Until 14 yrs

for girls & 16 yrs for boysAge of patients was subtracted by 14 or 16Result was multiplied by 3 to obtain estimated increase for

individual .To determine Space presently available-Measure distance on occlusal plane btw perpendicular drawn from

occlusal plane tangent to distal surf of perm 1st molar to anterior Border of ramus on lat ceph.

Diff in space available & required---discrepancy..

Computerized Digital Model Analysis

Plaster models are digitized by 3D surface scanning using laser beam and converting into a 3D Image.

Tooth dimensions and arch width are measured on the digital cast virtually using measuring tool.

The analyses are done by a computer algorithm/software automatically.

Computerized software are now capable of scanning study models and storing the scanned data as 3D images.

3D digital study models are designed to over come the problems –

Storage and RetrievalDiagnostic VersatilityTransferabilityDurability

Constructed through a laser scanning process that digitally maps the geometry of a patient’s dental anatomy to a high resolution 3D digital image with an accuracy of +. 01mm.

A laser stripe is projected onto the surface of the plaster cast & a digital camera is used to analyze distortions in the stripe.

The plaster cast is oriented on all axes to expose all its surfaces for scanning.

e - models:

This process produces 3D vertices that are connected into thousands of triangles to form the 3D image.

The software then displays the e-model on the computer screen by assigning color shades to each triangle based on its relative orientation to a digital light source.

This results in a high-resolution 3D image that can be viewed measured & manipulated on the computer screen as if the cast is in your hand.

Ortho CAD TM TechnologyOrthoCADTM software has been developed by CADENT,

Inc. (Computer Aided DENTistry, Fairview, NJ) to enable the orthodontist to view, manipulate, measure and analyze 3D digital study models easily and quickly.

The operator can browse and view the models separately and together from any direction and in any desired magnification on screen.

The software comes with several diagnostics tools such as:

Measurement analyzes e.g. Bolton analysis,

arch width and

length analysis

Advantages

OrthoCADTM are simpler and more effective method of measuring and storing data taken from the ‘virtual’ models.

Simpler storage and integration into the patients ‘digital’ file, along with digital photographs, x-rays and clinical notes.

Simpler retrieval and viewing along with the patients other clinical data.

Easy transferral to others in the patient healthcare circle.

Disadvantages

Virtual models cannot be mounted and articulated in reference to the patient’s tempero-mandibular joint function, although the jaw alignment assessment software does approach this partially.

ConclusionThere are numerous model analysis based on different

criterias.

Now it is left to the orthodontist to accept which ever analysis he feels best suits his group of population and his diagnosis and treatment planning.

The basis remains the same only the ways to express it differs

References--Proffit WR: Contemporary Orthodontics

Moyers : Handbook of Orthodontics

Thomas rakosi:orthodontic diagnosis

Bolton WA: Disharmony in tooth size and its relation to the analysis and treatment of malocclusion. Angle Orthod 1958;28:113.

Ponts analysis ;AO- vol 40,april ,1970

Harvey peck,sheldon peck—peck&peck analysis ajo,vol 61,384-401;1972

Littles analysis, ajo 1975,vol 68

Richard d faler,burstone,david-computerised interactive ortho t/t planning ajovol73,36-46,1978

Orthocad-digital model for digital era-journal of orthodontics,vol 31,344-347,2004

Computer based digital models—ao ,vol 74,2004

THANK THANK

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