Space analysis and tooth size analysis in orthodontic

university of glasgow

Space Analysis in Orthodontic

Mohammed Almuzian

Almuzian

1/1/2013

Mohammed Almuzian, University of Glasgow, 2013 0

ContentsDefinition.....................................................................................................................................2

Space analysis in permanent dentition........................................................................................2

Royal London space analysis........................................................................................................2

Stage 1: Space requirements assessment....................................................................................2

Stage 2, space creation or utilization through treatment............................................................6

Advantages of Royal London space analysis................................................................................7

Disadvantages of Royal London space analysis............................................................................7

Standard method for space analysis in permanent dentition .....................................................7

Space Analysis in the Mixed Dentition.........................................................................................8

(Tanaka and Johnston 1974) Measurement on the cast..............................................................8

Measurement of the Teeth from Radiographs and cast..............................................................8

(Moyer’s Prediction Values 1973) The Combination of cast and Prediction Table method.........9

(Staley and Kerber 1980) Combination of Radiographs and Prediction Table method................9

Conclusion..................................................................................................................................10

Symmetry of the arch.................................................................................................................10

Tooth Size Analysis.....................................................................................................................10

From Bolton 1962......................................................................................................................12

Is the Royal London Space Analysis reliable and does it influence orthodontic treatment decisions?. Al-Abdallah M, Sandler J, O'Brien K. 2008...............................................................14


Space Analysis in Orthodontic

Definition: Procedures of quantifying the space required in each arch which aids in:

1.Diagnosis

2.Treatment planning

3.Assessment of need for extraction

4.Anchorage planning

5.Mechanics planning

6.Informed consent

Space analysis in permanent dentition

Royal London space analysisDeveloped since 1985 but published AJODO 2000 by Kirschen,

Stage 1: Space requirements assessment1. Crowding and spacing

The method recommended for assessment is the visual method by use a clear

ruler over the occlusal or labial surface of study models to measure the

mesiodistal width of misaligned teeth and available space between the

contact points of the adjacent teeth taking in consideration the archform

that represent the majority of teeth.

Incisor chosen to represent the archform should be considered in:

a. Cephalometric analysis


b. Overjet measurement

c. Otherwise double counting occurs

Crowding/spacing assessed anterior to 6s

The assessment of crowding of 2 adjacent teeth can be undertaken together

by measuring the mesiodistal width of each tooth and the combined space

available.

This method is not recommended for 3 or more teeth as the difference

between chord and arc becomes significant, the chord being the space

available as measured in a straight-line and the arc being the curved

archform occupied by well-aligned teeth.

2. Level occlusal plane *

1mm req. for 3mm COS

1.5mm req. for 4mm COS

2mm req. for 5mm COS

Two considerations are relevant:

First, the space implication should be

recorded only if the premolars have not

been assessed as crowded; it would be an

example of double counting for premolars

to be assessed both as crowded and as needing space from levelling the

occlusal curve.


Second, clinical judgment is necessary as occlusal curves need not be

levelled in all cases.

The COS that is measured extend from distal to 6s to anterior teeth.

7s not used because often unerupted and it can be aligned by distal tipping.

3. Arch width change

0.5mm created by each mm of posterior arch width created (Lee, 2000).

Each millimeter increase in the intermolar width resulted in a reduction of

the anteroposterior arch depth of 0.28 mm, equivalent to an decrease in

arch perimeter length of 0.56 mm

Individual tooth expansion ignored

4. Incisor A-P change

Lower incisor position determined by: aims of treatment

Upper incisors position determined by achieving a normal 2mm OJ

For each 1mm incisor change we need 2mm space for each.

Proclination of inciors by arch lengthening will be considered under the

category of AP change and inclination changes (so it is a summative effect

but actually not a linear effect).

The traditional rule of thumb is that 1 mm of labial movement will provide

sufficient space for 2 mm of crowding (1mm on each side of the arch). This

rule of thumb assumes a rectangular arch form. In fact, with a much more


realistic parabolic archform, the situation is more complicated and in

general the labial movement will need to be greater than 1 mm to produce 2

mm of space. The paper by Steyn et al (1996) demonstrates this and

interestingly, also calculates the effect of different arch depths and widths

on the anterior movement of incisors required to accommodate a given

amount of crowding. In general, the wider the intercanine distance and the

shallower the arch depth from the canines to the mid-incisor point, the

greater the A-P expansion required to accommodate a given amount of

crowding

5. Angulation change

(Mx incisors only),

0.5mm for each tooth.*

so 2mm for angulation of all four incisors

Majority of cases this is not required.

6. Torque or Inclination change

(Mx incisors only),

1mm for each 5° change affecting all 4 teeth. 0.5mm if only 2 teeth

proclined.

The objectives of correct incisors torque is for:

I. Better aesthetics

II. Stability

III. Achieving corrects teeth contact without spacing


IV. Avoid incorrect buccal occlusion

Majority of cases this is not required.

Lower incisors not considered unless very proclined.

Proclination of inciors by arch lengthening will be considered under the

category of AP change and inclination changes (so it is a summative effect

but actually not a linear summative or accumulative effect).

Stage 2, space creation or utilization through treatment1.Tooth enlargement, build up

2.Space opening for prosthetics

3.Molar distal change

4.Tooth reduction, IPS

5.Extractions

6.Lee way space

7.Molar mesial change

8.Differential growth (positive for forward growing Class 2, negative for

forward growing Class 3 where a deterioration of arch relationship is

expected)

Advantages of Royal London space analysis1.Easy

2.Reliable

3.Valid


Disadvantages of Royal London space analysis1.Overestimate crowding

2.Little impact on decision for TP

3.Driven toward extraction

4.Doesn’t count vertical and transverse problems

Is the Royal London Space Analysis reliable and does it influence orthodontic treatment decisions?. Al-Abdallah M, Sandler J, O'Brien K. 2008 The purpose of this study was to investigate the reliability of the Royal

London Space Analysis (RLSA) and to evaluate its influence on

orthodontic treatment decisions. Thirty-one case records were collected to

represent various levels of crowding and different types of malocclusions.

Seventeen examiners assessed these records and completed a data sheet

that recorded information on their treatment decision. One month later, the

examiners attended a course on the RLSA and then used the analysis to re-

score the 31 cases. The models were also scored by the expert who led the

course and these were then considered the 'gold standard' scores. After a

further month, the examiners reapplied the RLSA and formulated a

treatment plan for each set of patient records.

RESULTS

•The examiners were reliable in using RLSA

•Regression showed that RLSA did not influence decisions

•May influence perceptual variation

•Did not influence judgemental variation


Other method for space analysis in permanent dentition :

1.Visual method by use a clear ruler over the occlusal or labial surface of

study models to measure the mesiodistal width of misaligned teeth and

available space between the contact points of the adjacent teeth taking in

consideration the archform that represent the majority of teeth.

It overestimate crowding. (Johal 1997), not reproducible, affected by the arc

and cord, accumulative error sue to the use of ruler

2.Segmental approach: divide the dental arch into segments that can be

measured as straight line approximations of the arch eg 6-3/ 3 -1/ \1-3 \3-6

or more for greater accuracy. Use dividers and ruler.(Moorrees and Reed

1954). Calculation of space required: Measure mesiodistal width of each

tooth using divided.

3.Brass wire/calliper method(0.5mm): contour a piece to line of occlusion then

straighten it out for measurement.(Nance 1947). Calculation of space

required: Measure mesiodistal width of each tooth using divided. It

underestimate crowding. (Johal 1997)

4.Microspcopic reflex technique

The reflex microscope and customized computer program. Tooth widths

were measured directly using a reflex microscope interfaced to an IBM

compatible personal computer, in which only the mesial and distal contact

points, from the first permanent molar to first permanent molar inclusive,

were recorded. No attempt was made to record arch perimeter directly; the


latter was calculated by the computer program from the total tooth width

minus the mesio-distal overlaps between adjacent teeth. From this

calculation,the amount of crowding in each arch was expressed in

millimetres. Precise details on the calculation of dental crowding from the

overlap method have been reported previously (Johal, 1995; Battagel, 1996).

Possible problems associated with the reflex microscope technique

1. expensive and a suitable computer program must be devised

2. If the teeth are severely tilted, for example mesially or distally angulated

to any significant degree, the maximum mesio-distal width is difficult to

record.

Space Analysis in the Mixed DentitionFor space analysis in the mixed dentition it is necessary to calculate the

size of the unerupted teeth. This can be done by the following 3 ways:

(Tanaka and Johnston 1974) Measurement on the cast

This technique requires no radiographs or tables (once memorised)

½ mesiodistal width of all 4 lower incisors + 10.5mm = mesiodistal

with of mandibular premolars plus canine(on one side)

½ mesiodistal width of all 4 lower incisors + 11mm =

mesiodistal with of maxillary premolars plus canine(on one side)

Magnification power technique (Measurement of the Teeth from Radiographs and cast)

This technique requires an undistorted image and easier with PA films.

The image must be interpreted with consideration to radiographic

enlargement.


True width of primary molar = True width of unerupted tooth

Radiographic width of premolar Radiographic width of unerupted tooth

Accuracy depends on the quality of the radiograph and is poor for canine

teeth but this technique can be used on all ethnic groups and for mandibular

and maxillary teeth.

(Moyer’s Prediction Values 1973) The Combination of cast and Prediction Table method

Moyer looked at the width of teeth of North American Caucasian children

and found that there was a correlation between the width of the unerupted

canines and premolars and the width of the erupted lower incisors.

The lower incisors were used because of the great variability of the size of

the maxillary laterals. This technique has a tendency to overestimate the

size of the unerupted teeth.

(Staley and Kerber 1980) Combination of Radiographs and Prediction Table method

Because canines are difficult to estimate from radiographs Staley and Kerber

estimated the size from the erupted permanent lower incisors and the

radiographic size of the lower premolars.

A graph was produced with a linear correlation allowing estimation of the

size of the lower canine.

This linear correlation graph was very accurate but only estimated the size of

the mandibular canine and required radiographs.

Conclusion Staley and Kerber most accurate followed by Tanaka and Johnston then

Moyer’s.


All estimation tables are better because they don’t require radiographs.

Can only be used on Caucasian children (race specific)

Should not be used on patients with obvious tooth size anomalies.

Symmetry of the archAn asymmetry of arch form also may be present even if the face looks

symmetric. A transparent ruled grid placed over the upper dental arch and

oriented to the midpalatal raphe can make it easier to see a distortion of

arch form in either physical or virtual casts.

Some author prefer to use the diagonal line which connect the DB and ML

cusp of U6 and it should pass in the U3 tips bilaterally to indicate the arch

symmetry.

Tooth Size Analysis1. If large upper teeth are combined with small lower teeth, as in a denture

setup with mismatched sizes, there is no way to achieve ideal occlusion.

2. A standard table is then used to compare the summed widths of the

maxillary to the mandibular anterior teeth and the total width of all upper to

lower teeth (excluding second and third molars) or we can use the

mathematical value by considering the lower normal and calculating the

ideal size of the upper when the normal ratio is used.

ABI = 77.2 %

OBI = 91.3 %


3. In order to know if the buccal segment has normal size, Bolton mentioned

that the upper to lower buccal ratio should be 1/1

4. Bolton’s ratios only apply well to white females who probably made up

Bolton’s entire original sample.

5. Proffit 2000 suggested that a quick check for anterior tooth size

discrepancy can be done by comparing the size of upper and lower lateral

incisors. He proposed that unless the upper lateral incisors are larger, a

discrepancy almost surely exists. For posterior tooth size discrepancy, he

recommends that a quick visual check be done by comparing the size of

upper and lower second premolars, which should be of approximately

equal size.

6. Studies by Harridien and Othman 2007 have reported

There is high degree of non-reproducibility of TSD, so repeated

measurement is well recommended.

Computerized methods of measurement are significantly more sensitive

than visual one ‘’eyeballing’’.

In the sample group, 17.4% had anterior tooth-width ratios and 5.4% had

total arch ratios greater than 2 standard deviations from Bolton's mean.

It is recommended that expressing the TSD in a form of mm is better than

the SD approach and so the 2 mm of required tooth size correction is an

appropriate threshold for clinical significance.

7. Bolton ratios in different malocclusions

Several authors have compared Bolton ratios in different malocclusions. It is

worth noting the findings of Nie and Lin (1999) who reported a tendency to


maxillary tooth-size excess in class 2 patients and mandibular tooth-size

excess in class 3 patients. Araujo and Souki (2003) also found a

significantly higher mean ratio (mandibular tooth excess) in class 3 cases

and a lower percentage of significant Bolton discrepancy in class 2 cases. It

is interesting to speculate whether this indicates that such discrepancies

contribute slightly to the establishment of the corresponding incisor

relationship or alternatively whether the relative ‘overgrowth’ of a jaw is

associated with growth control mechanisms which also cause relatively

large teeth in that jaw.

8. Bolton ratios and ethnic groups

Several studies have investigated differences in ratios in different ethnic

groups. Smith et al. (2000) found small but statistically different ratios

between black, Hispanic and white groups.

9. Bolton ratios and gender groups

They also found gender differences and suggest that Bolton’s ratios only

apply well to white females who probably made up Bolton’s entire original

sample.

10. Extraction and TSD

Extraction of 4s will effect TSD significantly while exo of 5s has low

effect (Yukay 1998)

From Bolton 1962A number of examples are provided to demonstrate the application of the

analysis.


Let us take this example:

Patient with the following measurement

Over all Ratio=96.46

Anterior Ratio= 86.45

Max. 6 (48mm)

Mand 6 (41.5mm )

The fact that these figures are larger than the mean would suggest that the

maxillary arch is too small for the mandibular arch. By substituting in the

anterior ratio formula

Sum Mand.6 (X)/ Sum Max. 6 (48)* 100 = 77.2

X = 37.05 , this is the ideal value of the mandibular 6 and the actual value

is 41.5mm .

Therefore if a satisfactory anterior relationship is to be achieved then the

mandibular segment needs to be reduced by 4.5mm.

Another example

Patient with this values

Over all Ratio= 82.8

Anterior Ratio= 70.3

Max. 6 (105mm).

Mand 12 (87mm)

The fact that both of these measurements are smaller than the mean

suggests that the maxillary arch is too large for the existing mandibular

arch.


By substituting values into the Over all Ratio

Sum Mand 12 (87)/ Sum Max 12 (X) * 100 = 91.3

X=95.3 i.e. ideal measurement of max 12 instead of actual measurement of

105mm.

Maxillary arch is 9.7mm larger than it should be. It can then be determined

if the xs is in the anterior or posterior regions.

Anterior Ratio Sum mand 6 (36)/ Sum max 6 (X)* 100 = 77.2

X = 46.7mm to be ideal. Actual value = 52

Max. anterior segment is 5.3mm too large and the remainder of 4.4mm is

confined to the buccal segment.

Treatment could involve stripping of maxillary anterior segment and

premolar extraction in the maxillary arch.

Gross disharmonies in tooth size may indicate the removal of a dental unit,

even where there is adequate arch length. Conversely, tooth size

discrepancies may be corrected by the placement of over contoured

restorations where indicated.


Health & Medicine

Space analysis and tooth size analysis in orthodontic