mixed dentition analysis. / orthodontic courses by indian dental academy

Mixed Dentition AnalysisRelationships of Tooth size and

available space during the Mixed dentition

INDIAN DENTAL ACADEMY

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Factors noted to Complete the Analysis 1.The size of all the Permanent teeth anterior to the first permanent molar. 2.The arch perimeter, 3.Expected changes in the arch perimeter which may occur with growth and development.


The Mixed Dentition Analysis helps one to estimate the amount of spacing or crowding which would exist for the patient if all the primary teeth were replaced by their successors the very day the analysis is done.

It does not predict the amount of natural decrease in perimeter which may occur during the transitional period without the loss of teeth.


Two Strategic Categories-

1.Those in which the size of the unerupted Cuspids and Premolars are estimated from measurement of the radiographic image.

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


Profitt’s Three basic Approaches 1. Estimation from Proportionality Table Moyers (1967), Tanaka and Johnson. 2. Radiographic Method Huckaba G.W Analysis(1964). 3. Combined Radiographic–Prediction Table Hixon and Oldfather (1956) Modified by Staley and Kerbers (1980)


Moyers Analysis Best known prediction table is Moyers(1967) Moyers follow the second strategic condition-

1.It has minimal systematic error and the range of such error is known.

2.It can be done with equal reliability by the beginner and the expert as it does not presume sophisticated clinical judgement.

3.Not time consuming.


4.Requires no special equipment or radiographic projections.

5. Although best done on dental casts, it can be done with reasonable accuracy in the mouth,

6.May be used for both dental arches


Mandibular Incisor have been choosen- a.Eruped early in the mouth. b.Easily measured accurately. c. Are directly in the midst of most space

management problems.

Maxillary Incisors are not chosen- Variability in size and their co-relation with

other group of teeth are of lower predicted value.


Procedure in Mandibular Arch Measure with tooth measuring gauge or a

pointed gauge,the greatest mesiodistal width of each of the four mandibular incisors.


Record these values on the mixed dentition analysis form


Determine the amount of space needed for alignment of the incisors.

Set the Boleys guage to a value equal to the sum of the widths of the left central & lateral incisors .


Place one point of the midline of the crest b/w the central incisors & let the other point lie along the line of the dental arch on the left side.

Mark on the cast the precise point where the distal surface of the lateral incisor will be when it has been aligned.


Compute the amount of space available after incisor alignment.

Measure the distance from the point marked in the line of the arch to the mesial surface of the first permanent molar.

This distance is the space available for the Cuspids & two Bicuspids and for any necessary molar adjustment after the incisors have been aligned.


Predict the size of the combined width of the mandibular Cuspids and Bicuspids.

Long method-

An experienced clinician can use 50% Prediction since it is more precise estimate.

For inexperienced clinicians, they should use the 75% Prediction for combined widths of Canines and two Premolars.


Probability table for predicting the sizes of unerupted Cuspids and bicuspids

Handbook of Orthodontics 4th edition Robert E Moyerswww.indiandentalacademy.com

Contd..

Short Method- less precise method Add the width of the mandibular incisors and

divide by two. To the value obtained add 10.5mm Mandibular Cuspids and Bicuspids 11.0mm Maxillary Cuspids and Bicuspids


Whether using the long or short method, record the estimated values for the combined cuspids and bicuspids widths in the mixed dentition analysis form for both sides and each arch.

Compute the amount of space left in the arch for molar adjustment by subtracting the estimated Cuspid and Bicuspids size from the measured space available in the arch after alignment of the incisors.Record these values for each side.


Procedure For maxillary Arch Procedure is similar to lower arch except- 1. A different probability chart is used for

predicting the upper cuspid and two Bicuspids sum[ widths]

2. Allowance must be made for Overjet correction when measuring the space to be occupied by the aligned incisors.


Probability Table for prediction

Handbook of Orthodontics 4th edition Robert E Moyerswww.indiandentalacademy.com

Although various methods of estimation have been proposed, Moyers regression scheme [utilizing the buccal segments and the mandibular incisors] is widely used because of its simplicity and ease of application.

Prediction of the size of unerupted canines & Premolars in a contemporary orthodontic population.

Marvin M Tanaka, Lysle E Johnston JADA vol 88 April 1974


Tanaka And Johnston Prediction

One half of the mesiodistal width

of the four lower incisors

+ 10.5mm

+ 11.0mm

Estimated width of mandibular Canine & Premolars in one quadrantEstimated width of maxillary Canine & Premolars in one quadrant


Tanaka And Johnston Prediction This method has good accuracy despite a

small bias toward overestimating the unerupted tooth sizes.

Requires neither radiographs nor reference tables, which makes it very convenient.


Huckaba Analysis

Recommended by Huckaba.G.W in 1964. Compensates for radiographic enlargement

of tooth image in periapical film. It is based on the assumption that degree of

magnification for a primary tooth will be the same as that of its underlying permanent successor on the same film.


MethodMeasure- 1. Width of the primary teeth

on the x-ray film: y 2. Width of its underlying

permanent successor x on the x ray film

3. Primary tooth on the cast : y

4. Width of unerupted permanent tooth is calculated by x = x y

y


The value obtained for the mandibular incisors on the cast and those for canines and premolars on the radiographs were added to provide the space required.

Space available is obtained by extending the brass wire from the mesio buccal of 1st permanent molar on one side, passing through the incisal edge of anterior teeth, and to the buccal cusps of 1st molar on the opposite side.


The difference in the value obtained for space required and space available is the amount of discrepancy.


Hixon & Oldfather Analysis This procedures combines measuremnts

from the dental casts and width measurements from the peri apical radiographs.

This method (1956); modified by Staley & Kerbers(1980) is restricted to the analysis of the supporting zone in the mandible.


Procedure Measure the size of unerupted 1st & 2nd

premolar in one mandibular quadrant from a peri apical radiograph.

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


After adding together both figures, the probable width of the permanent canine and 1st & 2nd premolars for the corresponding quadrant can be read off in the prediction graph under the column of the calculated sum total.


X-axis : Mandibular incisor width measured on the dental cast + total width of 1st & 2nd premolar on the peri apical radiograph.

Y-axis : Predicted total width of permanent mandibular canine and 1st & 2nd premolar.

The formula for calculation- Σ3+4+5=[(Σ 1+2+x4+x5) X 0.7158]+2.1267


Stereophotogrammetric: A Stereophotogrammetric camera was

developed for non topographic photogrammetry.

To derive 3 D information from serial cast in either a graphic or mathematical manner and to permit the use of computer for analytic procedure.

Suitable computer programs were designed for the comparative analysis of geometric data such as Vault space, Tissue mass, Surface area, Internal vault slope & Linear dimensions.


The basic principle of Stereophotogrammetry is that of binocular vision.

When 2 photographs of the same object are taken from slightly separated points, they can be viewed in a manner that will give a 3D model surface.

It permits a mathematic and geographic analysis of solid object such as casts.

It can also supply more analytical information than graphic tracing methods.


Stereophotographic system showing two model stages and windows for the placement of casts on the stage plane .The stage plane moves laterally 5 inches.The film magazine accepts a 9 x 9 inch glass plate.A precise grid is placed on the face of the stage plane.

The optic of a schnieder Super Angulon lens with a principle distance of 152.73mm and an equivalent focal length of 95mm.


Three problems particularly suitable for this analysis are: Cast of patient with unoperated complete

unilateral cleft lip and palate. Serial cast of patient with Apert’s syndrome. Comparison of casts treated by rapid expansion

and those treated by conventional full banded orthodontic appliance therapy.


Occulsograms:

Developed by Burstone in 1969. Occlusograms are actual sized photographs

of occlusal surface of dental casts. Tracings of these occlusograms allows the

orthodontist to simulate treatment in occlusal view.


Techniques: Photographic method:

Occlusal surface of U & L dental casts are photographed in a 1:1 ratio and a tracing of the photograph is made.

Photocopying method: The casts are photocopied on a photocopier

machine and the occlusal photocopy is used to obtain a tracing.


Occlusogram procedure: An occlusogram is a 1:1 reproduction of

occlusal surface of plaster models on a sheet of acetate tracing paper.

4x5 inch positive film transparencies are ideal.

These allows occlusograms to be held one over the other to examine cuspal relationship.

The photographs can be taken either with 35 mm camera and enlarged to 1:1 magnification or with a 4x5 inches Polaroid camera for 1:1 instant photographic prints.


Photographic prints are ideal for tracing purposes.

Problem with producing 4x5 inch transparencies or photographic print is maintaining the accurate orientation of the dental cast which must be accurately trimmed in the centric relation position.


Once the dental cast is trimmed in centric relation, registration grooves are made.Both the casts are seated in registration track in centric relation.


Cast is placed on the registration track on the

Occlusostat as soon as it is ready for photograph.

Occlusal surface of teeth are flushed with the leading edge of the occlostat which is also the focal length of the camera.


For photographing both the upper and lower dental cast, the recommended lens has a focal length of 210mm. and can be stopped down to f :45 for the best depth of the field.

The distance from the leading edge to the camera lens and from the camera lens to the film is 42cms. At these settings no enlargement is found at the level of occulsal plane.

Exposure time varies from 5-30 secs. depending on the lighting ( incandescent and fluorescent ) and the film can then be processed with X-ray developer and fixer.


Occlusogram tracing:

A sheet of tracing paper is placed over the photocopy of the cast, rough side up and is secured at the corners using masking tape.

Tracings are made of both U & L occlusograms.

R & L should be marked to avoid confusion. Tracings can be separated by cutting

between the registration lines.


With the U & L occlusogram tracing registered and secured on the sides, the mid sagittal registration line can be copied on the lower tracing.Growing denture bases can be adjusted so that they’ll be in their predicted relationship at the end of treatment periods.


Uses of occlusograms: Micheal R. Marcotte –demonstrated the uses of occlusograms in planning orthodontic treatment.

Determine arch form and width.Solution to arch length discrepancies.Presence and extent of skeletal asymmetries.Anchorage requirements in each quadrant for extraction cases.

Presence and extent of tooth mass discrepancies.


To estimate final occlusal relationship. Estimate tooth movements in all 3 planes. Determine changes in the cant of occlusal

plane. Aid in arch wire construction. Growth prediction with the help of tracing. Quantifying the treatment progress and

discovering the exact nature of many orthodontic problem.


Disadvantages:

Time consuming. Not very precise. Because of difference in magnification, the

combination of occlusogram with a head film has been considered difficult and unreliable.


3 D Occlusogram Software: When performing analysis on a scanned

image, the differences in magnification can easily be accounted for by the computer, increasing speed, easiness and accuracy.

It was therefore, determined to develop a user- friendly software that , in addition to the advantages mentioned by Marcotte, can also provide the basis for the computerized appliance design.


The procedure includes :

Image scanning & setting. Occlusal view processing Lateral cephalometric

processing Occlusogram construction


Advantages Combination of lateral cephalometric image with

the occlusal views of the upper & lower dental casts complete the 3 dimensional set up of the patient.

Demonstrates all the treatment possibilities. All the needed movements of the teeth are clearly visible on the occlusal views in the 3 planes of space allowing the design for the “custom made appliance” & the lateral cephalogram shows the planned displacement for the molars & the incisors.

The software can simulate the results of standard surgical procedures.

Ease in using Accurate & precise Rapid


Holograms

The first Hologram was produced by Leith and upatnieks in 1964.

Holography is a photographic technique for recording and reconstructing images in such a way that the 3D aspect of an object can be obtained. The recorded images is called a “Hologram”.

Holography uses laser light to reproduce very high quality 3D images of a cast.

It permits 3D model analysis, super impositions and storage.


Holograms in Orthodontist: AJODO oct 1995

SYSTEM:

1. Holocamera 2. Automatic Developer 3. illumination and measuring system


Holocamera

Easy to handle. The model being

photographed is placed on glass plate for exposure.

The laser beam used in the camera is divergent.


Automatic Developer Developed to expose

plates without assistance. Consists of series of trays

that contain the various chemicals used, a mechanical engine that controls the movements of the holder in which plates can be placed.

30 plates can be developed simultaneously.

The holder carries the plate from tray to tray each having a different function during exposure.


Developing, Water rinsing ,Bleaching and Wetting procedure are required to develop an exposed holographic plate.

During each steps ,the holder is kept inside the corresponding tray as long as time indicates.

The finished hologram will be either red or green depending on the bleach used.


Measurement System Illumination element:

Halogen lamp: to illuminate the hologram.

Analysis or measuring element: Plate holder mounted on an x-y-z positioner. The z micropositioner has an optical fiber which is connected to a laser diode that projects a small red spot light used for depth measurement.


Orthodontic Applications Measurement of incisor intrusion. Study the effects of high pull headgear. Tooth position measurements. Study the effect of max. expansion on facial

skeleton. Study the effect of class2 elastics on bone

displacement. Study the effect of cervical headgear on

maxilla. Facial & dental arch symmetry. Determine the centre of rotation produced by

orthodontic forces. Lower incisor space analysis.


Advantage Convenient, low bulk Resistant to almost all destructive agents apart

from fire. These films may be scratched or bent or covered in dust without interfering with the latent image.

Superimposition of images is possible, thus detection of any changes & tooth movement are possible.

Holographic image can be measured in 3 dimensions.

Ease in storage, transportation Cost similar to conventional photography.


Disadvantage

Inability to place the holograms immediately next to the patient’s mouth to make side by side comparisons.

Cannot be adjusted once made. Incorrect occlusion of the models when the

holograms are being made.


Photocopies of the study modelsCan be used for : 1) Comparing pre and post treatment arch forms 2) Checking original tooth rotations or the initial

arch form during treatment 3) Communicating with other practitioner about

characteristic of the malocclusion . 4) Producing occlusograms for demonstration

purpose


These photocopies may be less precise for :

1) Measuring arch length 2) Producing occlusograms for space analysis.


COMPUTERIZED ANALYIS DENTAL CASTSOSCOPO Oscopo is a computer program for the

Oscilloscopic Simulation for Correcting Orthodontically , Problems in Occlusion.

It was developed by Robert H. Biggerstaff in 1970.

It is based on a two dimensional representation of the upper and lower dentition as photographed from an occlusal view.


OSCOPO is the computer method for measuring, analyzing and evaluating the dimensional vectors involved in orthodontic correction.

It is a visual method for realigning the dental elements involved in the translation from a malocclusion to a normal occlusion in the individual case.


OSCOPO gives a top view of the tooth images of the mandibular and maxillary dental casts as projected to the occlusal plane while recording the patients usual occluding relationship.

Other portions of the program permit translational, rotational simulations of the image of a tooth or a group of tooth changing the occlusal pattern as originally seen on the dental casts or oscilloscope.


OSCOPO does not have the potential for discriminating between Apical or Tilting movement.

It does however represent graphically the end result of movements produced in the two defined planes of space.


Digital Study Models 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 Retrieval Diagnostic Versatility Transferability Durability


Application Of 3D Imaging Of Teeth Archiving Study Cast Documentation of treatment progress and

communication between professional colleagues is made easy.

Can examine intra & inter arch and transverse relationships between U&L arches

Treatment objectives and planning can be created by using “Virtual set-up” of orthodontic appliance.


Simulation of space following extraction, tooth uprighting or incisor retraction can be easily shown.

3D prefabrication of archwires using specific robotics after setting up brackets position on the dental arches.

Construction of 3D “ Aligners”- The Invisalign technology.


e-MODELS-3D Digital dental models using laser technology-

J.C.O (2)-2003 Three dimensional digital study model.Methods of producing digital models: Destructive imaging: Removes the part of

the cast ,a little at a time ,while it is being imaged.

Non destructive imaging: Uses structural light ,laser light or x-rays to image while leaving the original cast intact.


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.


ADVANTAGES OF e-model Measurements can be made in any plane or orientation. Various analysis such as Bolton’s analysis, arch width &

length analysis can be done. Cross-sectional tools allow e-models to be sliced in any

vertical or horizontal plane to check symmetry, overjet, overbite & complete measurements at any location.

Permits analysis of occlusal relationships. Improves accuracy & efficiency of orthodontic diagnosis,

treatment planning & bracket placement. Midline analysis (skeletal or dental asymmetries can be

evaluated). Mock surgeries & presurgical evaluation can be done. Record keeping Ease in storage


e-plan Latest innovation in 3D

treatment planning. Simulates multiple treatment

options to help determine the most effective treatment plan.

Enables the clinician to simulate tooth rotations ,movements & extractions with a click of the mouse.

They allow pts. to watch the movement of their own teeth from a malocclusion view to a post treatment view.

Effective communication tool for pts., their families & referring dentists.


Ortho CAD TM Technology OrthoCADTM 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.

Alginate impressions of the maxillary and mandibular dentitions are then downloaded manually or automatically from the world wide website using a utility called OrthoCAD downloader.

The average file size for each 3D model is 3 Mb.


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 )

Midline analysis (The ability to split the model sagittally or transversely for better compressions)

Overbite and Over jet analysis.


The step in orthoCADTM virtual set-up

1. Choose your preferred brackets, bands and wires from the available straight wire systems listed.

2. Incisors are positioned, as well as molars.

3&4. The orthodontists should slide maxillary and mandibular teeth into their proper positions or correct the position of the brackets themselves to achieve better inter-and intra-arch relationships.

5. The sagittal inter-arch relationship should be double-checked.

6. Evaluate the transverse relationship.

7. Molar position and jaw closure are adjusted to make sure that the correct form of treatment is chosen.


Align Technology

The Invisalign appliance for Orthodontic tooth movement was developed in 1998.

It is the ‘invisible’ way to straighten teeth into a perfect occlusion using thin, clear, overlay sequential appliance.


Procedure (A) Initial treatment planning with patients’

photographs and radiographs are sent to Invisalign lab.

(b) Impressions are converted into plaster models.

(c ) In lab, models are first coated with protective shells, & encased in a mixture of resin and a hardener.

(d) After chemical setting, the become blocks of the hardened resin with many plaster models inside. Each tray is placed in a destructive scanning machine.

(e) Each 3D models is constructed from about 300 2D scans.

(f) Once the teeth are separated and re-assembled back into the arches, the designers create a final set-up of what the patient’s teeth will look like when the treatment is completed.

(g) For each stereolithographic constructed model a clear invisalign aligner is created by heat.

(h) These aligners are trimmed, polished, cleaned and finally sent to the prescribing orthodontist.


Conclusion There 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. So it does not matter which analysis you follow but what matter is that how efficiently you imply the results of it to your treatment planning and do justice to your patient.


References ORTHODONTICS

PRINCIPLES AND PRACTICE,

- GRABER T.M. Handbook of orthodontics. - ROBERT E. MOYERS. Contemporary orthodontics. - WILLIAM R. PROFFIT. Orthodontics current principles and concepts. - THOMAS M. GRABER & Vanarsdall


Thank You


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mixed dentition analysis. / orthodontic courses by indian dental academy

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