Download introduction frequency of bolton tooth size discrepancies outside 2

ORIGINAL ARTICLE
FREQUENCY OF BOLTON TOOTH SIZE DISCREPANCIES OUTSIDE
2 STANDARD DEVIATION OF THE BOLTON'S MEAN AMONG
ORTHODONTIC PATIENTS.
Babur Ashraf Quraishi1
Sheeraz Hussain2
Faiza Ansari3
Fareeha Zeeshan4
BDS, FCPS
BDS, FCPS, MCPS
BDS
BDS
OBJECTIVE: To evaluate, the mesiodistal dimensions of permanent teeth, frequency of Bolton ratio & the
presence of Bolton discrepancy outside 2 SD of the Bolton's mean in an orthodontic population, irrespective of the
type of malocclusion.
METHODOLOGY: The study was carried out at the department of orthodontics Fatima Jinnah Dental College &
Hospital, Karachi. The sample comprised of 150 pairs of good quality pre- treatment study models with fully
erupted & complete permanent dentition from first molar to first molar, which were selected from the orthodontic
patient pool. Dental casts having grossly carious teeth, prosthesis or anomalies of teeth were not included. The
mean, range and standard deviation were calculated for the mesiodistal dimensions of the teeth, anterior ratio and
overall ratio.A2- sample t- test was used to test for the statistical difference between means.
RESULTS: In general there was no difference between the mesiodistal dimensions of the males and females so the
subgroups were combined for further calculations. Mean overall ratio was found to be 91.54 % (SD 2) and the value
ranged from 86.42 % to 96.70 %. Mean anterior ratio was found to be 78.85 % (SD 2.3) and the values ranged from
72.49 % to 83.14 %. This study found that 13 subjects (9.1 %) had overall ratio & 22 subjects (14.7 %) had anterior
ratio outside 2 SD of Bolton's mean.
CONCLUSIONS: With such a high number of significant discrepancies, it is important to routinely perform
Bolton tooth size analysis before starting orthodontic treatment as TSD is prevalent among orthodontic patients.
KEY WORDS: Bolton tooth size discrepancy, Bolton ratio, tooth size discrepancy (TSD), orthodontic population.
J Pak DentAssoc. 2011 (4) ; 250-253
INTRODUCTION
F
or proper alignment & good interdigitation at the
end of orthodontic treatment, the tooth size should
1
be in harmony in both the dental arches . According
2
to Proffit approximately 5% of the population has some
degree of discrepancy among the size of individual teeth.
3
In 1902 G.V. Black was the first to develop means & set
up tables for mesiodistal dimensions of teeth. Several
other authors like Ballard, Neff, Steadman and Lundstrom
4-7
after that followed Black's study with modifications .
females with excellent occlusion & developed two ratios
using the mesiodistal width. The anterior ratio (77.2 % +/1.65) was obtained by measuring the mesiodistal width
from canine to canine in both arches & overall ratio (91.3
% +/- 1.91) which was obtained by measuring mesiodistal
width from molar to molar in both arches. The formulas
derived by Bolton are as follows:
Total ratio (%) =
Anterior ratio (%) = Sum of mandibular “6” X 100
Sum of maxillary “6”
1
Bolton in 1958 developed formula relating the
maxillary dentition to the mandibular dentition which
became a gold standard in orthodontics. He took 55 white
1
2
3
4
Assistant Professor& Head department of
Orthodontics, Fatima Jinnah Dental College, Karachi
Assistant Professor& Head department of
Orthodontics, Karachi Medical & Dental College
Demonstrator, Fatima Jinnah Dental College, Karachi
Demonstrator, Fatima Jinnah Dental College, Karachi
Correspondence: BaburA. Quraishi <[email protected]>
Sum of mandibular “12” X 100
Sum of maxillary “12”
Bolton concluded that if there is discrepancy in the
tooth size ratio then it will be difficult to achieve ideal
overjet, overbite and interdigitation at the end of
8
treatment. Stifter applied all the tooth dimensions studies
of that time on Class I occlusion cases and came to the
conclusion that the anterior ratio is more important for
excellent finishing.
Evidence exists in the literature that tooth size shows
9,10.
9
racial, ethnic & sex differences
Lavelle compared
250
JPDA Vol. 20 No. 04 Oct-Dec 2011
Quraishi B. A / Hussain S /
Ansari F / Zeeshan F
Frequency of bolton tooth size discrepancies
Negroids, Caucasoids and Mongoloids and found greater
overall & anterior ratios in Negroids when compared to
both Caucasoids and Mongoloids, and the overall ratio
was greater in males than in females for all the three races.
10
Smith et al reported that the Bolton's ratio is only
applicable for white females & it's not applicable for white
11
males and other races. Crosby & Alexander reported a
large number of orthodontic patients presented with a
significant Bolton tooth size discrepancy.
The objectives of this study were to identify possible
sexual dimorphism in mesiodistal dimensions, evaluate
anterior & overall ratios and the percentage of patients
who presented with a significant tooth size discrepancy
greater than 2 SD from Bolton's means, at Fatima Jinnah
Dental College & Hospital.
RESULTS
Tooth measurements & gender:
Table I reports the mean, range & standard deviation
of the mesiodistal width of maxillary & mandibular teeth,
from central incisor to 1st molar in both males & females.
In this sample the mesiodistal dimensions of teeth for
males were slightly larger than that of females but no
sexual dimorphism was observed, hence both male &
female subgroups were combined to evaluate the Bolton
ratio.
Tooth
Mesiodistal dimensions of the teeth were measured
using digital calipers with sharpened points (Sontax Co.,
Japan) up to 0.01 decimal at contact points. The
mesiodistal width was obtained, by measuring the
maximum distance between the mesial and distal contact
points of the tooth on a line parallel to the occlusal plane,
12
as described by Morrees . A single investigator (F.A)
measured the casts and not more than 10 casts were done
in a day to avoid eye fatigue. The measurements were
inserted in the Bolton formula and values for the anterior
and overall ratio were obtained.
Mandibilar
Central
5.57 4.6-6.4
Lateral
5.2-7.0
6.0
Canine
6.92 6.1-8.1
Ist Premolar
7.18 6.3-8.3
2nd Premolar 7.01 5.9-8.9
Ist Molar
11.20 9.9-12.8
0.39 5.43
0.41 5.94
0.45 6.64
0.42 7.07
0.59 7.09
0.71 10.87
4.7-6.3
5.0-7.0
5.6-7.9
5.6-8.5
5.9-8.9
9.4-12.5
P-Value
0.32
0.64
0.05
0.98
0.52
0.21
0.27
0.33
0.05
0.22
0.42
0.05
0.37
0.37
0.40
0.48
0.53
0.62
Table 1: Mean, Range & Standard Deviation for the
mesiodistal dimensions for Males & Females (mm)
Anterior and Overall ratio:
Table 2 summarizes the mean overall ratio, which
was found to be 91.54 with a standard deviation of 2.0.
The value ranged from a low of 86.42 to a high of 96.70
with the median as 91.55. The mean anterior ratio for the
orthodontic sample was found to be 77.85 with a standard
deviation of 2.3. The values ranged from 72.49 to a high of
83.14. The overall & anterior ratios were also compared to
Statistical analysis:
The mean, range and standard deviation were
calculated for the tooth widths. To determine gender
differences independent sample t- tests were performed
using Statistical Package for Social Sciences (SPSS)
version 13.0. The second part of the study was to evaluate
the percentage of patients who had tooth size
discrepancies which were within one, two or more than
two standard deviations from Bolton's mean. The mean,
range & standard deviation were calculated for both the
overall ratio & anterior ratio.
JPDA Vol. 20 No. 04 Oct-Dec 2011
Females
Maxillary
Mean Range SD Mean Range SD
Central
8.83 7.8-10.0 0.65 8.59 7.3-10.0 0.56
Lateral
6.91 5.5-8.2 0.55 6.87 5.7-8.7 0.52
Canine
7.94 6.0-9.0 0.59 7.67 6.6-8.8 0.45
Ist Premolar
7.05 6.0-8.0 0.44 7.11 5.8-8.2 0.50
2nd Premolar 6.67 5.2-7.6 0.55 6.65 5.6-7.9 0.49
Ist Molar
10.36 8.9-12.0 .64 10.21 8.9-11.7 0.55
METHODOLOGY
The data for the present study was obtained from the
records taken at Fatima Jinnah Dental College. One
hundred & fifty pre-treatment study casts were selected
from a pool of 950 patients presenting for orthodontic
treatment irrespective of their molar classification. There
were 109 females ( 72.7%) & 41 males ( 27.3%) and they
were selected on the basis that all permanent teeth were
present from 1st molar to 1st molar in both maxillary &
mandibular arches, no previous orthodontic treatment
12- 30
with age range of
years. The dental casts were of good
quality and there were no mesiodistal cavities, fillings,
fractured teeth or prosthetic replacements. There were no
obvious inter-proximal or occlusal wear. Casts having
missing, impacted teeth or gross abnormalities were
rejected.
Males
251
Bolton Study
Bolton Study
Sample Size
55
150
Anterior Ratio Mean
77.2
77.85
SD
1.65
2.28
Range
5.9
10.69
Minimum
74.5
72.9
Maximum
80.4
83.14
Overall Ratio Mean
91.3
91.54
SD
1.91
2.0
Range
7.3
10.28
Minimum
87.5
86.42
Maximum
94.8
96.70
Table 2: Statistical parameters obtained in the present study
compared to Bolton study
Quraishi B. A / Hussain S /
Ansari F / Zeeshan F
Frequency of bolton tooth size discrepancies
the Bolton's original sample, though readings of the
present study were slightly higher for both the ratios but it
was statistically insignificant.
Frequency
91.30 is Bolton mean
89.39- 91.29 & 91.31- 93.21 within 1 SD
87.48- 89.38 & 93.22- 95. 12 within 2 SD
<87.47 & >95.13 outside 2 SD.
50
45
TSD & its Clinical significance:
40
Table 3 gives the frequency of the tooth size
discrepancies of 1, 2 and more than 2 SD from the Bolton
mean for the anterior and overall ratios. . Of the 150 cases
13 (9.1 %) cases had overall ratios outside the 2 SD from
the Bolton's mean (fig 1). About 22 (14.7 %) subjects had
anterior ratio that fell outside of 2 SD from the Bolton's
mean value (fig 2).
35
Anterior Ratio
30
25
20
15
Overall Ratio
Number
Percentage
Number
Percentage
66
62
22
44
40.6
14.6
102
35
13
67.9
23
9.1
Bolton + -1SD
Bolton + -2SD
Bolton + ->SD
10
5
0
Table 3: Number and percentage distribution of Anterior
& Overall TSD from Bolton's SD means.
Frequency
Percentage
<73.89
73.9075.54
75.5577.19
<-2SD
-2SD
-1SD
77.20
Mean
Valid
77.2178.85
78.8680.50
1SD
2SD
>80.57
>2SD
Figure 2: Anterior Ratio: the percentage of subjects in this
study categorized by the SD of Bolton's original study.
Percentage
Comparison of present study with other populations:
60
Table 4 compares the anterior and overall ratios of the
present study with the other studies done exclusively on
subjects selected irrespective of the type of malocclusion.
50
40
DISCUSSION
30
20
10
0
<87.47
87.4889.38
89.3991.29
<-2SD
-2SD
-1SD
91.30
Mean
Valid
91.3193.21
93.329512
1SD
2SD
>95.13
>2SD
Figure 1: Overall Ratio: the percentage of subjects in this
study categorized by the SD of Bolton's original study.
Author
Crosby & Alexander
Freeman et al13
Santoro et al16
Araujo & Souki19
Bernabe et al15
Othman &
Harradine 14
Othman et al2 1
11
Population
Country
Orthodontic
Orthodontic
Orthodontic
Orthodontic
School
Orthodontic
Am erican
Am erican
Dominican
Brazilian
Peruvian
British
Sam ple
Size
109
157
54
300
200
150
A nterior
TS D%
22.9
30.6
28.0
22.7
20.5
17.4
Overall
TSD%
___
13.5
11.0
___
5.4
5.4
In this study, 150 study models were selected out of
950 patients meeting the inclusion criteria. Although the
means of the present study and that of Bolton study were
similar the ranges and standard deviations of the present
study are significantly larger. This result has been
11,13-20
supported by other studies
and can be due to the fact
that in our study all the malocclusions were present in
contrast to Bolton who selected only excellent occlusion
1
subjects. Bolton suggested that values outside 1SD from
his reported mean requires consideration but many
11,13,15,16
authors
have considered a threshold of 2 SD to be a
clinically significant Bolton discrepancy.Again the reason
for this difference of selection for standard deviation is
that Bolton used cases with excellent occlusion and the
other studies used subjects with malocclusion.
In a normally distributed population, 5% of subjects
would
fall 2 SD from the mean. The present study found
Dental
Malaysian
40
47.5
10
that 9.1 % of the sample had overall tooth width ratios
school
Al- Omari
School
Jordanian
367
23.7
9.5
greater than 2 SD (5 % greater than - 2 SD & 4.1 % greater
Present S tudy
Orthodontic
Pakistani
150
14.7
9.1
than +2 SD) from Bolton's mean (fig 1) and similar results
11,13-17,19,21
. The anterior ratio in the
Table 4: Present & previous studies, showing prevalence of were found by others
present sample was 14.7 % greater than 2 SD (6 % greater
discrepancies outside Bolton's 2 SD mean.
17
252
JPDA Vol. 20 No. 04 Oct-Dec 2011
Quraishi B. A / Hussain S /
Ansari F / Zeeshan F
Frequency of bolton tooth size discrepancies
than - 2 SD & 8.7 % greater than + 2 SD) from Bolton's
mean. The results of the present study for the overall ratio
17
were similar to Al- Omari , less than that of other
13, 16, 21
14
studies
and higher than Othman and Harradine .
When the anterior ratio of the present study was compared
to the other studies, it was found to be the least. Almost all
11, 13-21
studies
had a higher percentage of TSD for anterior
ratio. The reason for variation in results for these studies is
variation in the composition, selection and number of
3
examiners doing the measurements. Freeman et al1 had
24 different examiners and this can introduce errors in
measurement as inter-examiner errors were not reported
21
by them. Although Othman et al did perform intra and
inter-examiner systematic and random errors but their
sample size was very small having only 40 dental students
from University of Malaya. The results from such small
sample size may not be a true reflection of the Malaysian
population, as a very high percentage (47.5 %) of the
dental subjects had anterior TSD outside the 2SD Bolton
mean.
The current study found no gender differences and
14,19,22,23
this trend is supported by other studies
, the sample
was selected with strict selection criteria having subjects
of Pakistani origin therefore representative of all
malocclusions for our population. The findings of the
present study suggest that a large number of orthodontic
patients have a Bolton tooth size discrepancy outside of
Bolton 2 SD. This may influence treatment goal and
results so Bolton tooth size analysis should be performed
on all patients prior to initiation of orthodontic treatment
rather than only for cases with small lateral incisors or
premolars as reported by Proffit.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
CONCLUSION
17.
About 14.7 % of the orthodontic patients had
anterior tooth size discrepancy and 9.1 % had overall tooth
size discrepancy greater than Bolton 2 standard 18.
deviations. It is important to routinely perform Bolton
tooth size analysis for all patients for good interdigitation
19.
& results at the end of treatment.
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