MODEL ANALYSIS

Submitted by:-SATHEESH P B

INTRODUCTION

• Model analysis is one of the essential diagnostic aids.• The important purpose of the orthodontic study model

is to help in model analysis.• The study model provides a three dimensional view of

the maxillary and mandibular dental arches in all three planes of space, i.e., sagittal, vertical and transverse planes.

• Model analysis are used for determination of space discrepancies in the arch, i.e., to determine the difference between the space available and the space required for tooth alignment.

CLASSIFICATION

PERMANENT DENTITION MODEL ANALYSIS

MIXED DENTITION MODEL ANALYSIS

Arch perimeter analysis Moyer’s Mixed dentition analysis

Nance Carey’s analysis Tanaka and johnston analysis

Ashley Howe’s analysis Nance mixed dentition analysis

Pont’s analysis Huckaba’s mixed dentition analysis (Radiographic method)

Linder Harth analysis

Korkhaus analysis

Bolton’s analysis

Peck and Peck index

CAREY’S ANALYSIS

• The arch length-tooth material discrepancy is the main cause for most malocclusions.

• This discrepancy can be calculated with the help of Carey’s analysis.

• The analysis is carried out in the lower arch.

PROCEDURE

• STEP I: DETERMINATION OF ARCH LENGTH (total space available)– Measure the arch perimeter using soft brass wire.

– From mesio-buccal line angle of the mandibular right first molar, pass the wire along the buccal cusp and cingulum in the anterior region, pass the wire on the left quadrant like a mirror image till the mesiobuccal line angle of the left mandibular first molar.

• In case of proclined anteriors, the wire is passed along the cingulum of anterior teeth.

• If the anterior teeth are retroclined, the brass wire is passed labial to the teeth in the anterior region.

• If the teeth are well aligned, the wire passes over the incisal edges of the anteriors.

• Mark the wire, straighten the wire and measure the wire which gives the space available.

STEP II: DETERMINATION OF TOOTH MATERIAL (total space required)– Measure the mesiodistal dimension of all teeth

mesial to the first molar and add. This value gives the total space required.

STEP III: DETERMINATION OF DISCREPANCY– The discrepancy refers to the difference

between the arch length and tooth material.

INTERPRETATION

DISCREPANCY INFERENCE

0 to 2.5 mm Proximal stripping can be carried out to reduce the minimal tooth material

excess

2.5 to 5 mmExtraction of second premolar is

indicated

Greater than 5mmExtraction of first premolar is usually

required

ASHLEY HOWE ANALYSIS

• Ashley Howe considered the crowding of teeth to be the result of deficiency in arch width rather than arch length.

• He found the relationship between the twelve anterior teeth to the permanent second molars and the width of the dental arch in first premolar region.

• This is usually done in the upper arch.

ANALYSIS• DETERMINATION OF TOOTH MATERIAL (TTM):

mesodistal width of all the teeth anterior to the permanent second molars are measured with the help of calipers and all the values are summed up.

• DETERMINATION OF PREMOLAR DIAMETER (PMD): it refers to the distance or arch width from the tip of the buccal cusp of one first premolar to the tip of the buccal cusp of opposite first premolar.

• DETERMINATION OF PREMOLAR BASAL ARCH WIDTH (PMBAW): measurement of width from canine fossa of one side to another gives us the width of the dental arch at the apical base or junction between the basal bone and the alveolar process.

INFERENCE

• There are two inferences derived in Ashley Howe’s analysis.– First one is the comparison of PMBAW and

PMD – Second one is the relationship between the

PMBAW and TTM

INFERENCE I

• The PMBAW and PMD are compared.

• If the PMBAW is greater than the PWD, then it is indicated that arch expansion is possible.

• If on the other hand, the PMBAW is less than PMD, then arch expansion is not possible.

INFERENCE II

• To achieve a normal occlusion with a full complement of teeth, the basal arch width at the premolar region (PMBAW) should be 44% of the sum of the mesiodistal widths of all the teeth mesial to the second molar (TTM).

INFERENCE

PMBAW % INFERENCE

37% or less need for extraction

37-44% Borderline case

44% or more Treatment by non extraction

PONT’S ANALYSIS

• Pont in 1909, proposed a method of determining the ideal dental arch width in premolar and first molar area based on the sum total of upper maxillary incisors

PONT’S ANALYSIS HELPS IN

• Determining whether the dental arch is narrow or is normal.

• Determining the need for lateral arch expansion.

• Determining how much the expansion is possible at the premolar and molar regions.

ANALYSIS

• DETERMINATION OF SUM OF INCISORS(SI): the greatest mesiodistal width of the incisors is measured with calipers, recorded on a line and their sums then recorded (in mm).

• DETERMINATION OF MEASURED PREMOLAR VALUE(PMV): width of the arch in the premolar region from the distal pit of upper first premolar to the distal pit of the second opposite first premolar.

• DETERMINATION OF THE MEASURED MOLAR VALUE (MMV): width of the arch in the molar region from the mesial pit of the upper first molar to the mesial pit of the opposite first molar.

• CALCULATED PREMOLAR VALUE (CPV):

or the ideal arch width in the premolar region is determined by:

CPV = SI X 100

80

• CALCULATED MOLAR VALUE (CMV):

or ideal arch width in the molar region is determined by:

CMV = SI X 100

64

• If calculated value or expected value is more than measured value, it indicates the need for expansion.

• Thus, it is possible to determine how much expansion is needed in the premolar and molar regions.

• Pont’s analysis gives us approximate indications of the degree of narrowness of dental arches in case of malocclusion and the amount of lateral expansion required for the arch to be of sufficient size to accommodate the teeth in perfect alignment.

DRAWBACKS

• Maxillary laterals are the teeth most commonly missing from the oral cavity.

• Peg-shaped laterals can be seen.

• The analysis was done from the casts of French population

• It does not take skeletal mal-relationships into consideration.

LINDER HARTH ANALYSIS

• Linder Harth proposed an index very similar to that of Pont’s analysis.

• He made variation in the formula to determine the calculated premolar and molar values.

FORMULA

• The calculated premolar value (CPV):

CPV = SI X 100

85

• The calculated molar value (CMV):

CMV = SI X 100

64

KORKHAUS ANALYSIS

• This analysis is similar to Pont’s analysis.

• Only difference is that it makes use of Linder Harth’s formula to determine the ideal width in the premolar and molar regions.

• In addition this analysis also utilizes a perpendicular measurement made from a point in between the two maxillary incisors to the midpoint of the inter proximal line.

• According to Korkhaus for a given width of the upper incisors a specific value of the distance between the mid point of the inter premolar line to the point between the two maxillary incisors should exist.

• An increase in this perpendicular measurement denotes proclination of the upper anterior teeth, while a decrease in this value denotes retroclined upper anteriors.

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