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.