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Appearance of a labial notch in maxillary incisors A population survey.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 80:25-29 (1989)
Appearance of a Labial Notch in Maxillary Incisors:
A Population Survey
I W A BRIN AND YOCHEVED BEN-BASSAT
Department of Orthodontics, Hebrew University Hadassah Faculty of
Dental Medicine, Jerusalem, Israel
KEY WORDS
bial groove.
Dental developmental defects, Gingival contour, La-
ABSTRACT
A labiogingival notch appearing on the enamel of maxillary
central incisors seems to be a potential factor for compromised gingival and
dental health. The objective of the survey was to describe the phenomenon and
its prevalence in a random Israeli population. One thousand eight hundred
eighty children with fully erupted permanent incisors were clinically examined. The appearance of the labiogingival notch on the enamel surface of the
maxillary central incisors was determined. Two depth categories of the
phenomenon were distinguished by probing. The possible differences in the
prevalence of the labial notch appearance, between the sexes as well as
between the right and left sides, were statistically evaluated. The prevalence
ofthe labial notch on at least one incisor in the population examined was 6.5%
(5.1%unilaterally and 1.4%bilaterally). No significant difference between the
sexes regarding the appearance of this phenomenon was found. The shallow
notch was similarly distributed between the right and left sides in both sexes.
However, the deeper malformations appeared significantly more on the left
side in boys ( P < 0.05)and in girls (P < 0.01).The gingivae tended to follow the
enamel contour; however, only in few cases was gingival inflammation or
incipient caries diagnosed. It was concluded that the labio-gingival notch is not
a rare phenomenon, and it should be given special attention to prevent possible
damage to the dental and gingival tissues.
Kovacs (1971) in his systematic description of dental roots reported on a ((fossacoronoradicular” anomaly. He noticed that in
cases presenting with this feature the cementoenamel junction “instead of showing a
bend toward the crown as it generally does,
was divided into two often unequal parts and
showed a t that place a hollow which was
nearly always present in the crown and very
often in the root.’’
The appearance of a similar coronal phenomenon was noticed by us on some maxillary central incisors when a group of school
children was screened for orthodontic treatment. The irregularity appeared as a notch
in the labial enamel surface near the gingival margin. The purpose of the present communication is to describe the clinical appearance of the labial gingival notch and its
prevalence in a random Israeli population.
@ 1989 ALAN R.LISS. INC
MATERIALS AND METHODS
A random population of primary school
children in the Jerusalem school district was
screened for orthodontic treatment. For the
present study only children with fully
erupted central permanent incisors were included. One thousand eight hundred eighty
children with a total of 3,760 fully erupted
permanent central incisors were examined.
The examination was conducted in the classroom in normal daylight. A dental probe was
used for the determination of subgingival
buccal contour of the enamel. The presence
of a notch was established when a depression
in the buccal enamel surface at the gingival
level could be detected by passing the probe
from one side to the other.
Received June 15,1988;accepted October 17,1988
26
I. BRIN AND Y.BEN-BASSAT
To achieve calibration between the two
examiners, the first 150 children were double-checked by both. Further, in borderline
cases the determination regarding the presence or depth of the notch was established
following examination by both investigators.
When a notch was encountered its depth was
recorded as shallow or deep, as evaIuated by
inspection and probing.
The possible differences in the prevalence
of the labial notch appearance, between the
sexes and the right and left sides, were sta-
Fig. 1. The labial gingival notch on a left maxillary
central incisor. A Frontal view. B: Occlusal view.
LABIAL NOTCH IN MAXILLARY INCISORS
tistically evaluated. The chi-squared test
and the McNemar test of symmetry were
used.
RESULTS
The labiogingival notch appeared as a depression in the gingival area of the central
maxillary incisor. Its depth varied from a
shallow depression that could be identified
mainly by probing to a deep groove. The
gingival margin closely followed the enamel
contour: it appeared almost normal in the
case of the shallow notch (Fig. lA,B),while in
the case of a deep notch it acquired an irregular contour because of extension of the gingival tissue into the defect (Fig. 2). In some of
the deep notches accumulation of plaque and
external staining were observed. In three
cases (2.4%of the affected teeth) initial caries was detected in the notch.
The labial notch was found in 123 of the
1,880 children examined; thus the prevalence of the labial notch on at least one
incisor was 6.5%. In 96 children (5.1% of
those examined) the notch appeared unilaterally, while in 27 children (1.4%) it was
bilateral (Fig. 3). The distribution of this
feature accordingto sex is presented in Table
27
1. Statistical analysis utilizing the chisquared test revealed no significant difference (P > 0.05) between the sexes regarding
the appearance of this phenomenon.
The prevalence of the labial notch according to side and depth on individual teeth is
presented in Table 2. The McNemar test of
symmetry was applied to establish occurrence according to side (right or left) in children with unilateral notch. It was found that
the incidence of the shallow notch was similar on the right and the left sides in boys and
in girls. However, the deeper malformations
occurred significantlymore on the left side in
boys ( P < 0.05) and in girls ( P < 0.01).
DISCUSSION
Only scarce information regarding developmental groove-like irregularities on the
labial aspect of the maxillary central incisors
can be found in the literature. Kovacs (1971)
in his chapter on dental root morphology
mentioned some anomalies in the cementoenamel junction of the maxillary central incisors. He described the coronoradicular
fossa as a hollow appearing on the buccal
aspect of the cementoenamel junction, very
often also noticed on the root in a more or less
Fig. 2. Gingival contour in the case of a deep labiogingival notch.
28
I. BRIN AND Y.BEN-BASSAT
Fig. 3. Bilateral appearance of a labiogingival notch.
pronounced form. In his collection of 500 dry
teeth, Kovacs found 15 (3%)teeth presenting
with this phenomenon. Kogon (1986) in his
description of the palatoradicular groove
also mentioned the appearance of a similar
groove on the labial surface of two teeth (in a
collection of 1,382 extracted central incisors).
The prevalence of the labial gingival notch
in our sample was higher (6.5%).This finding could be attributed to a difference in
definition. The coronal appearance of the
labial notch encountered in our survey was
similar to that described by Kovacs (1971)
and Kogon (1986). However, the radicular
portion was not examined and complete sim-
TABLE 1 . Prevalence of the labial notch in the
examined population according to sex
Total
Boys
No.
Percent
Girls
No.
Percent
Total
NO.
Percent
Normal
Notched
948
100
894
94.3
54
5.7
932
100
863
92.6
69
7.4
1,880
100
1,757
93.5
123
6.5
TABLE 2. Prevalance of the labial notch according to depth, side, and sex
Boys
No.
Percent
Girls
No.
Percent
Total
No.
Percent
Right incisor
Shallow
Deep
Deep
Bilateral,
shallow
and deep
14
0.7
7
0.3
16 16
1.7
886
47.5
18
0.9
17
0.9
1,797
47.9
32
0.6
24
0.6
Total
Normal
1,896
100
915
48.3
16
0.8
0.05
911
48.1
1,864
100
898
48.2
19
1.0
4
0.2
3,760
100
1,813
48.4
35
0.9
5
0.1
1
Normal
Left incisor
Shallow
+
11
+ 11
1.2
54
1.4
LABIAL NOTCH IN MAXILLARY INCISORS
ilarity between the phenomena described in
the literature and that described by us could
not be established.
A possible genetic or ethnic factor could
also affect the difference in prevalence: In
our sample the children were from an Israeli
Jewish population, whereas the teeth in
Kogon’s sample were from individuals from
South Wales. The origin of the teeth described by Kovacs is unspecified. The fact
that this phenomenon was not mentioned as
a known feature in any of the widely used
textbooks on dental anatomy may be caused
by its extremely rare appearance in other
populations.
When the occurrence of the labial notch
was studied according to sex, no statistically
significant difference was found. The previously mentioned reports did not refer to sex
differences.
Comparison of the incidences on the right
and left sides revealed a statistically significant preferance for the left side for the
deeper defects. No explanation for this finding can be offered; however, side preferance
has been shown for other developmental
anomalies.
No etiologic factor for this irregularity can
be indicated. Trauma to the deciduous predecessor was considered as a possible etiologic factor. This, however, was looked into
in a longitudinal survey of a group of children who encountered trauma to their primary incisors and who were reexamined
again at the stage of permanent dentition
(Brin et al., 1984). No correlation was found
in that study between the appearance of the
labial notch and a previously encountered
trauma to the deciduous dentition.
Coronal anatomy is considered as a significant factor for periodontal health; thus
there could be a clinical importance to this
feature: uneven enamel contour in the gingi-
29
val region may increase the susceptibility to
periodontal disease, while the lack of a selfcleansing effect in a subgingival notch renders this site susceptible to carious attack as
well. In our clinical examination it was found
that the gingival margin followed the contour of the enamel (Figs. 1-3). However, only
in few cases was gingivitis or incipient caries
found in the area of the notch. The low
susceptibility to pathology may be explained
by the young age of the examined subjects. It
may well be that the incipient lesions can
increase in number or become more pronounced with age if preventive measures
like proper oral hygiene are not taken. It
should be concluded, therefore, that when a
gingival notch is encountered the patient
should be taught an efficient oral hygiene
technique, and regular check-ups should include this particular area, which might serve
as a locus minore resistentia (point of least
resistance).
ACKNOWLEDGMENTS
This study was supported in part by a
grant from the Joint Research Fund of the
Hebrew University-Hadassah
School of
Dental Medicine founded by the Alpha
Omega Fraternity and the Hadassah Medical Organization. The authors thank Mr. I.
Einot for his help in analyzing the statistical
data.
LITERATURE CITED
Brin I, Ben Bassat Y, Fuks A, and Zilberman Y (1984)
Trauma to the primary incisors and its effect on the
permanent successors. Pediatr. Dent. 6:78-82.
Kogon SL (1986)The prevalence, location and conformation of palatopradicular grooves in maxillary incisors.
J. Periodontol. 57:231-234.
Kovacs I(1971) A systematic description of dental roots.
In AA Dahlberg (ed.): Dental Morphology and Evolution. Chicago: University of Chicago Press.
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