Prevalence of Missing Lateral Incisor Agenesis in an Or¬thodontic Arabs Population in Israel(Arab48)
Published on: Mar 4, 2016
Transcripts - Prevalence of Missing Lateral Incisor Agenesis in an Or¬thodontic Arabs Population in Israel(Arab48)
International Journal of Public Health Research
2015; X(X): XX-XX
Published online MM DD, 2015 (http://www.openscienceonline.com/journal/ijphr)
Prevalence of Missing Lateral Incisor Agenesis in
an Orthodontic Arabs Population in Israel(Arab48)
Muhamad Abu-Hussein1, *
, Nezar Watted2
, Abdulgani Azzaldeen3
, Mohammad Yehia4
, Obaida Awadi5
University of Naples Federico II, Naples, Italy, Department of Pediatric Dentistry, University of Athens, Greece
Clinics and Policlinics for Dental, Oral and Maxillofacial Diseases of the Bavarian Julius-Maximilian-University, Wuerzburg, Germany
Department of Conservative Dentistry, Al-Quds University, Jerusalem, Palestine
Triangle R&D Center, Kafr Qara, Israel
Center for dentistry, research and Aesthetics, Jatt /Israel
Statistics and Actuarial Faculty, University of Haifa, Haifa, Israel
firstname.lastname@example.org (M. Abu-Hussein)
To cite this article
Muhamad Abu-Hussein, Nezar Watted, Abdulgani Azzaldeen, Mohammad Yehia, Obaida Awadi, Yosef Abu-Hussein. Prevalence of Missing
Lateral Incisor Agenesis in an Orthodontic Arabs Population in Israel(Arab48). International Journal of Public Health Research.
Vol. X, No. X, 2015, pp. XX-XX.
Tooth agenesis is defined as congenital absence of one or more teeth in primary or permanent dentition and is a common oral
variation that affects a large population group. Among the missing one’s, maxillary lateral incisor is more frequent causing
esthetic and functional impairments in the affected individual. It might be associated with systemic problems, syndromic
conditions or other oral anomalies. Management of missing lateral incisors involves a multi-disciplinary approach for
rehabilitation of impaired esthetics and function. This study was carried out to determine the prevalence of congenital absence
(agenesis) of maxillary lateral incisors in Arabs population in Israel(Arab48).
Tooth Agenesis, Hypodontia, Maxillary Lateral Incisor, Congenitally Missing Teeth, Epidemiology, Arab48
Many terms can be used to describe missing teeth.
Anodontia is the complete absence of teeth; Oligodontia or
partial anodontia means absence of six or more teeth;
hypodontia denotes missing teeth, but usually less than six
and often the size and shape of remaining teeth are altered as
well, congenitally missing teeth or agenesis is defined as
teeth that failed to develop or are not present at birth.
Agenesis of any tooth can cause dental asymmetries,
alignment difficulties, and arch length discrepancies but
when the missing tooth is in the anterior region of the maxilla,
the discrepancies can be quite noticeable.[1,2]
The maxillary lateral incisor is the second most frequently
missing tooth after the mandibular second premolar even
though Muller et al. found that maxillary lateral incisors
experience the most agenesis (not including third molars).
Agenesis of the maxillary lateral incisor is also linked with
anomalies and syndromes such as agenesis of other
permanent teeth, microdontia of maxillary lateral incisors
(peg laterals), palatally displaced canines and distal
angulations of mandibular second premolars.
Woolf presented data on anomalies associated with
agenesis of the maxillary lateral incisor, such as peg
laterals. His study sample consisted of members of the
Mormon Church in Salt Lake City because of the extensive
family records they keep.
Woolf studied 103 participants who had either unilateral or
bilateral agenesis of the maxillary lateral incisor, and the
relatives of this test group (187 families) from the same area
acting as controls. Results showed that 17.7% of parents and
siblings of the sample population also had agenesis of the
maxillary lateral incisor or pegshaped laterals, compared to
only 2.8% in the control group. Twenty-four of the 103
participants who had agenesis of the maxillary lateral incisor
also had a peg-shaped lateral incisor. Members in the same
family tended to show the same location and pattern of
agenesis (bilateral, unilateral or right versus left). From these
2 Muhamad Abu-Hussein et al.: Prevalence of Missing Lateral Incisor Agenesis in an Orthodontic Arabs Population in Israel(Arab48)
Woolf concluded that some genotypes result specifically in
agenesis of the maxillary lateral incisor, some cause agenesis
of multiple teeth, and some cause agenesis of the maxillary
lateral incisor and anomalies such as peg laterals. Evidence
of a genetic association was demonstrated in this population;
however genetic mapping was not used at the time the study
was conducted in 1971 to verify genetic links.
In the 1975 Symposium on Genetics, Bailit presented on
variations in tooth size, gender, agenesis and race. The
mouth was divided into 3 ‘groups’ per side consisting of
incisors (central and lateral), premolars (first and second) and
molars (first, second and third). The most distal tooth in each
tooth group was shown to be the least stable, except for the
mandibular central incisor, and therefore more likely to be
congenitally missing. This theory of tooth instability is also
known as Butler’s Field Theory.
Bailit theorized that the most distal tooth in a group is
more influenced by environmental factors rather than
genetics. He believed that genetics had a greater affect on the
size of the central incisor, first premolar and first molar
whereas the maxillary lateral incisor, second premolar and
second molar are more affected by the environment. The last
tooth to erupt in a segment (most distal) has a predetermined
space in which to erupt, giving it more phenotypic flexibility.
Bailit stated that except for the maxillary lateral incisors,
tooth sizes are fairly symmetrical bilaterally and when a
maxillary lateral incisor is missing, it is most likely the left
one. At the time the paper was written in 1975, there was
little knowledge about the extent to which genetics affects
agenesis, but Bailit suspected it was important.
Since the development of genetic mapping, Brook et al.
have shown that some genes are implicated in the agenesis of
teeth, including PAX9, MSX1 and AXIN2. The PAX9 gene is
on chromosome 14 with a controlling factor for dental
development and mutations related to missing teeth.
Peck, Peck and Kataja linked palatally displaced canines,
transposition of mandibular lateral incisors and canines and
maxillary canine and premolar transposition with agenesis.
They studied 161 subjects and found that patients with
maxillary canine-first premolar transposition were 13 times
more likely (26%) to have agenesis of a maxillary lateral
incisor. They agreed with Brook et al. that PAX9 and MSX1
mutations contribute to tooth agenesis , however they also
pointed out that the PAX9 and MSX1 genetic mutations are
associated with posterior tooth agenesis while a strong
causative gene mutation for anterior agenesis has yet to be
found. Peck, Peck and Kataja believe signaling proteins such
as bone morphogenic proteins (BMP) and fibroblast growth
factor (FGF) may be responsible for agenesis early in
Pirinen et al. focused their research on palatally displaced
canines and agenesis of incisors and premolars. They
examined 106 patients (77 females, 29 males) who had
undergone surgical exposure of a palatally impacted canine
to determine whether they also expressed agenesis. One
hundred and ten first-degree relatives of these patients and 93
second-degree relatives were also examined while pedigrees
were created to establish a genetic link. Results showed that
36% of the test patients exhibited agenesis, which is 4.5
times the population prevalence. First and second-degree
relatives showed 19-20% agenesis or 2.5 times the
population prevalence. This illustrates that there is a strong
genetic link between palatally displaced canines and
Dempsey and Townsend aimed to quantify the relative
contributions of the environment and genetics to the mesio-
distal (MD) and buccal-lingual (BL) sizes of teeth in
monozygotic and dizygotic twins.The MD and BL of 596
participants’ teeth were measured on plaster casts. Different
model analyses were created to separate twin pairs of males
and females, monozygotic twins that were raised apart
(different environments), and dizygotic twins. Mandibular
lateral incisors were found to be the least sexually dimorphic
permanent teeth. For most teeth, the variation in crown size
can be explained by the additive genetic and unique
environmental variation. Environmental influences on tooth
crown size can be substantial, but heritability of most crown
sizes is moderate to high.
Arte et al. also found strong genetic relationships between
hypodontia and tooth anomalies such as ectopic maxillary
canines. They studied 11 people (aged10-36 years) with
hypodontia of 1 to 6 permanent teeth and their relatives,
totaling 214 Finnish individuals. The mean number of tooth
agenesis in the test group was 2.3 and 1.7 in their families
indicating a strong genetic link. Data was collected
retrospectively through dental history and radiographs and
the controls were established with published population
prevalence. Results showed 4.5-4.9 times the occurrence of
hypodontia in first and second degree relatives (39% and 36%
respectively). They also found an equal maternal and paternal
inheritance. Rotated premolars and ectopic permanent
canines were seen more frequently in patients with
hypodontia and their families; 2 to 3 times that seen in the
general population. The authors concluded that incisor-
premolar hypodontia is associated with many dental
anomalies and is transmitted in an autosomal dominant
Since the development of genetic mapping, Brook et al.
have shown that some genes are implicated in the agenesis of
teeth, including PAX9, MSX1 and AXIN2. The PAX9 gene is
on chromosome 14 with a controlling factor for dental
development and mutations related to missing teeth.[6,12]
Brook et al. measured the tooth sizes on maxillary and
mandibular dental casts in the test group, 10 people with a
known PAX9 mutation in one family and 10 people in a
control group matched for sex, age and ethnicity, who were
not related to the test group and did not have the PAX9
mutation. Differences in the test group with the mutation and
hypodontia were found; these teeth were significantly smaller
than controls. Canines and first molars were least affected in
the test group. This contradicts Bailit’s theory that genetics
mostly affects the first tooth in each group: the central incisor,
canine, first premolar and molar.17 Brook et al. found that
the second tooth in each group was more affected by the
International Journal of Public Health Research 2015; X(X): XX-XX 3
PAX9 mutation. The study concluded that the PAX9 mutation
not only decreased tooth number, but also tooth size
throughout the dentition.
Hypodontia (excluding the third molar) is relatively
common findings in different populations. Its frequency
varies from 2.3 to 8% (5, 13). Maxillary lateral incisors were
the second most commonly absent teeth as reported by
several authors (Claton, 1956 (2); Glenn 1964 (3); Ingervall
wt al., 1972 (4); Wisth et al., 1974 (5); Rolling, 1980(6)).
Muller et al/, 1970 (7), found that in those people with
missing one tooth, the maxillary lateral incisors are
congenitally absent in 46.4 % of U.S.A. subjects.
Magnusson TE., 1977 (8), found that agenesis of maxillary
lateral incisor was present in 18% after examining 1116
In Saudi Arabia, the prevalence of hypodontia and peg-
shaped maxillary lateral incisors were studied by Al-Emran et
al. 1990 , in 500 Saudi Arabia male students within the age
range 13-14 years, he reported that agenesis of maxillary
lateral incisor was present 0.6%. Whereas, deviation from
normal dental morphology (peg-shaped) maxillary lateral
incisor was observed in 4% of the sample.
Salama and Abdel-Megid, 1994 , conducted a study on the
prevalence of agenesis and peg-shaped maxillary lateral
incisors in 1300 Saudi Arabia male students. They found that
agenesis of maxillary lateral incisor was present in 9 %. Peg-
shaped maxillary lateral incisor was found in 0.7 % of the
total sample size.
Both of the previous studies were done in the Central
Region, (Riyadh city), and further studies in the eastern
region are needed to confirm their findings m
The purpose of this investigation is to determine the
prevalence of congenital absence (agenesis) maxillary lateral
incisor among Arabs population in Israel. And to compare the
data with other similar studies.
2. Materials and Methods
We conducted a retrospective study of all
orthopantomograms (OPGs) of 2200 Palestinian patients
aged 12 to 39,5 years (Mean age #16,2), taken between 2006
and 2013, which were available in the Center for
Ambiguous OPGs of subjects with no proper record of date
of birth and poor quality image were excluded.
All students attending on the day of examination were
examined. Inclusion criteria were as follows:
1.Palestinian Arabian origin.
2. No pervious history of maxillary lateral incisor
3. No pervious restorative reshaping or crowning of the
maxillary lateral incisors
4. No pervious orthodontic treatment.
The clinical examination was carried out in the our dental
center in good daylight using disposable tongue depressors to
retract the lips if needed during anterior segment examination.
The patient were questioned about possible earlier
extractions and those with positive history were excluded
from the study. If the lateral incisors were missing and the
patient has no positive history of pervious extraction, the
patient was referred to the our center for diagnostic
panoramic radiograph to be taken.
Agenesis of lateral incisor was determined from
radiograph; patient with impacted maxillary lateral incisors
were also excluded from the study.
Fig. 1a, b.: Unilateral missing lateral Incisor.
Fig. 2a, b.: Bilateral missing lateral Incisors.
4 Muhamad Abu-Hussein et al.: Prevalence of Missing Lateral Incisor Agenesis in an Orthodontic Arabs Population in Israel(Arab48)
Table 1. Gender distribution of patients treated.
Treated (Orth.) N=2200 %
Female 1354 61.60%
Male 846 38.40%
Of the 2200 patients, 846 were males (38,4%) and 1354
were females (61,6%) (Table 1)(Fig.3); the mean age was
16,2years, ranging from 10,2 to 39,5 years. (Table 2).
Table 2. Means age Hypodontia.
Age, Impacted Min Max Avg
10.2 39.5 16.2
Of the 2200 subjects (1354 females- [61,6%], 846males -
[38,4%]) exa-mined, 24(13 females 54,[17%], 11 males) were
found to have MLI agenesis. Thus, the prevalence of MLI
agenesis in our sample was 2,6%, and 0,6%per cent of the fe-
males and 0,5% of the males were affected.
Fig. 3. Gender distribution of patients treated.
Table 3. Patients with Missing Lateral Teeth N=24 .
Missing Lateral N=24 %Missing
Female 13 54.17%
Male 11 45.83%
Fig. 4. Patients with Missing Lateral Teeth.
Table (4) presents, the percentage distribution of normal,
maxillary lateral incisor values among the 2200 patients .
2176 (98,90%) of the sample had normal lateral incisors, 24
(1,09%) had congenital absence (agenesis) maxillary lateral
Table 4. Number of Persons Having Missing Lateral Incisors.
Female Male Total
13 11 24
Normal lateral incisors 1341 835 2176
Total 1354 846 2200
Table 5. Number OF Examinees with Unilaterally and Bilaterally Missing
12 3 5.26 0.14 2 3.51 0.09
22 3 5.26 0.14 2 3.51 0.09
7 12.28 0.32 7 12.28 0.32
Total 13 22.8 0.6 11 19.3 0.5
Bilateral agenesis of MLI occurred in 14 subjects ( 0,64%)
and unilateral agenesis in 10 patients ( 0,45% ). Of those
presenting with unilateral agenesis of the MLI, 6( 60%) were
on the right side and 4 (40%) on the left side. No gender
difference was observed in the side-to-side distribution of
MLI agenesis (p > 0.05).
The number of patients seeking orthodontic treatment in
Arabs population in Israel has increased markedly during
recent years. Therefore it is important to have relevant
epidemiological data on different types of malocclusion in
order to estimate the total need for treatment.
In the present study, analysis of a large sample was done in
order to obtain a clear and valid picture of the distribution
pattern of congenital absence (agenesis) of maxillary lateral
incisor in the Arabs population in Israel.
Investigators in other populations (United State, German,
Iceland, and Swedish populations) reported also different
prevalence pattern of agenesis and peg-shaped maxillary
lateral incis ors. This indicates that differences do exist
between various populations. The most likely expansion is
the differences in racial and ethnic origin.
Sofaer et al. in 1971 provided one theory on tooth size and
agenesis. He measured the teeth of 17,000 high school
students in Hawaii ranging in age from 11-
20 years, some with agenesis of the maxillary lateral
incisor and some with a fullcomplement of teeth. Teeth were
measured intra-orally with oral proof of agenesis; no
radiographs were taken of the subjects. Peg laterals were
associated with a smaller than normal central incisor adjacent
to it. A missing lateral incisor tended to have a larger than
normal central incisor adjacent. Central incisors were more
asymmetrical than normal in cases of a missing lateral incisor
and were also slightly, but not significantly, larger than
International Journal of Public Health Research 2015; X(X): XX-XX 5
normal when maxillary lateral incisors were bilaterally
missing. Sofaer hypothesized that the size of the lateral
incisor depends on the amount of space the central and
canine have left for it during primordial development. Since
the canine and central incisors develop before the lateral
incisor, he theorized that it must compete with its neighbors
for size. Sofaer believed that inadequate environment, poor
primordium or both may cause this tooth size asymmetry.
In 2001, Basdra et al. investigated a relationship between
Class III and Class II division 1 malocclusions who had not
received orthodontic treatment and congenital tooth
anomalies.  They examined 215 total patients with these
malocclusions looking for: maxillary incisor hypodontia,
maxillary canine impaction, transpositions, supernumerary
teeth, and tooth agenesis. The age range of the patients was
7.2-45.8 years, roughly half males and half females. A dental
history and radiographs were used to confirm the tooth
anomalies. While 5.5% of the Class III patients and 1.9% of
the CL II division 1 patients presented with agenesis of their
maxillary lateral incisors, the frequency was not different
from that of the general population. In fact, none of the
anomalies in these two malocclusion groups showed variance
from that in the normal population; results were not
Le Bot’s study found similar results as Baidas and Hashim.
 He measured the teeth of 200 French males with
maxillary lateral incisor agenesis confirmed radiographically.
The sum of the bucco-lingual and mesio-distal dimensions of
maxillary teeth in dental arches with the agenesis of a lateral
incisor were shown to be significantly smaller than normal.
Interestingly, dental arches in the test group who experienced
‘peg’ laterals with no agenesis expressed even smaller teeth
than the group with agenesis. Premolars and canines within
the arch showed the greatest reduction in dimensions when
the maxillary lateral was missing; molars were least affected.
Le Bot also noted that 39.6% of the test sample with agenesis
had a missing a third molar compared to 12.4% in the control
In contrast to Sofaer, Baidas and Hashim found that
maxillary anterior teeth were smaller than normal in patients
with unilateral or bilateral agenesis of maxillary lateral
incisor. Thirty dental cases were measured, 12 had a
missing lateral incisor unilaterally, 18 had missing lateral
incisors bilaterally. However, the test population race was not
disclosed and male and female measurements were analyzed
together.The authors used Bolton’s analysis4,8 and Wheeler’s
index37 to evaluate anterior maxillary and mandibular tooth
size ratios. The Bolton Index ratios were larger forpatients
with bilateral or unilateral agenesis of a maxillary lateral
incisor (79.1% and 81.7% respectively with the norm of
77.2%); thus demonstrating lack of maxillary tooth structure.
The reliability of Bolton ratios on racially unknown study
population should be questioned, mainly because Bolton
ratios have been shown to best apply toCaucasian
In 2007, Othman and Harradine studied tooth size
discrepancies in an orthodontic population to determine how
frequently they occur, the amount of discrepancy that is
clinically significant and if these discrepancies can be
visually evaluated without measurement (recommended by
Bosio39 and Proffit27). Their population did not contain
agenesis, but complete, permanent dentitions. They measured
the mesio-distal widths of teeth on 150 (96 female, 54 male)
pretreatment casts from Caucasian patients and used the
Bolton Analysis4 to calculate tooth size discrepancies.
Othman and Harradine found that in this orthodontic
population, 17.4% of people had anterior ratios and 5.4% had
total tooth-width ratios greater than 2 standard deviations
from Bolton’s norms. They believe that Bolton’s selection
criteria may have skewed his results because he chose his
sample based on ‘excellent occlusions’ , which is not typical
for an orthodontic practice. The authors also determined that
2mm of tooth size discrepancy within an arch (1mm per side)
is considered clinically significant, compared to other
literature stating a discrepancy of 1.5mm per ach is clinically
significant.They also concluded that visualization of a
tooth size discrepancy by comparing the size of the maxillary
lateral incisor to the size of the mandibular lateral incisor is
not an accurate method of evaluating tooth
size discrepancies. Thirty percent of teeth visually
examined this way were deemednot to have a discrepancy
even though measurements showed they did have a
significant tooth size deficiency.
Many other studies, we found a significantly higher
prevalence of MLI agenesis in females. Our findings that
both MLIs were just as likely to be missing as one incisor,
and when one lateral incisor was missing it was likely to be
on the right side, agree with previous researches . However,
we urge caution when interpreting these results because of
the methodological shortcomings in retrospective studies of
Previous studies have shown that tooth age-nesis may be
related to other dental anomalies such as microdontia or peg-
shaped incisors, taurodontism, transposition, supernumerary
tooth, ectopic eruption, retained primary tooth, and ectopic
eruption. However, agenesis of MLI and associated dental
anomalies were limited in the literature. Most of the papers
published about MLI agenesis investigated reduced crown
size or peg shaped form of the contralateral MLI among the
subjects with unilateral absence of this tooth.
Pinho et al. investigated other associated developmentally
absent teeth and supernumerary tooth. Although no
supernumerary tooth was found, they found that 12.8 per cent
of the subjects with MLI agenesis had absence of other teeth
and most frequently observed missing teeth were maxillary
and mandibular premolars. The prevalence of the subjects
with agenesis of other teeth (9.6 per cent), in this study, was
very close to the data reported by Pinho et al. and the
missing teeth were maxillary and mandibular premolars (63.6
per cent) and mandibular central incisors (36.4 per
Celikoglu et al. reported MLI-canine transposition in
the cases of MLI agenesis and Peck et al.  showed
transposition in the mandible. In this study, one subject with
6 Muhamad Abu-Hussein et al.: Prevalence of Missing Lateral Incisor Agenesis in an Orthodontic Arabs Population in Israel(Arab48)
MLI-canine transposition in the same side with MLI agenesis
was observed. Additionally, we found 6 subjects with
dilacerations, 5 with the impaction of maxillary canines, 1
with a supernume-rary tooth, and 1 with a transmigrated
maxillary canine. Supernumerary tooth was an extra
premolar in the same side with the MLI agenesis. In addition,
transmigration and transposition of the maxillary canine were
also in the same side with the MLI agenesis.
In 78.7 per cent of the patients with the agenesis of MLIs,
the space was orthodontically closed, while in the remaining
21.3 per cent the space was orthodontically maintained for
prosthetic replacements and implant placement. The lateral
incisor space was closed in the patients with crowded arches,
while space was maintained in the patients with uncrowded
arches. Since crowding was present in the study group
and implant treatment is deferred until the jaws have stopped
growing to avoid the complications caused by implants , the
space was orthodontically closed in most of the patients.
Robertsson et al.  investigated the aesthetics according to
the opinions of the patients, occlusal function, and
periodontal health in subjects with one or two MLI agenesis
who had received either orthodontic space opening or closure
followed by a modern prosthetic replacement for the MLI
agenesis. The authors indicated that orthodontic space
closure produced treatment results that appear to be
reasonably stable, and better accepted by the patients than
Orthodontic patients do not necessarily reflect the number
of individuals in the population with tooth agenesis, this will
be dependent on the availability of orthodontic treatment and
its uptake in this particular population. However,
retrospective studies rely on good record keeping and
orthodontic patients often have more complete records. Thus,
some reports have shown the prevalence of tooth agenesis in
To summarize the studies presented on tooth size and
agenesis: tooth size discrepancies do exist in combination
with agenesis of a maxillary lateral incisor. Central incisors
adjacent to the missing lateral incisors were larger than
‘normal’ in an early, intra-oral study, whereas other studies
measuring teeth on dental casts showed smaller than average
maxillary anterior teeth when the lateral incisor was missing.
Premolars and canines within the arch with agenesis have
also been shown to be smaller than normal and third molar
agenesis is more common as well.
In an orthodontic population without agenesis, tooth size
discrepancies are fairly
i.The prevalence rates for lateral incisor agenesis 1,1%,
respectively, in Arabas populationin Israel.
2. The present study also shows that Arabs population in
Israel had less agenesis maxillary lateral incisors than
3.The prevalence of missing teeth was more common is
females than males.
4. The prevalence of missing teeth was more bilateral than
In the diagnosis of agenesis of maxillary lateral incisors it
is necessary to perform a good clinical examination and
subsequent radiographic confirmation in order to observe not
only the absence itself but also all the anomalies that may be
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