ORIGINAL ARTICLE

Cleft sidedness and congenitally missing ormalformed permanent maxillary lateral incisorsin Korean patients with unilateral cleft lip andalveolus or unilateral cleft lip and palateNa-Young Kima and Seung-Hak Baekb

Seoul, Korea

Introduction: The purpose of this study was to investigate the differences in the prevalence of cleftsidedness, the number of congenitally missing or malformed permanent maxillary lateral incisors (MLIs), andthe presence of supernumerary teeth in Korean patients with unilateral cleft lip and alveolus (UCLA) and thosewith unilateral cleft lip and palate (UCLP). Methods: Seventy-five patients with UCLA and 129 patientswith UCLP (ages, 6.0 to 13.0 years) were studied by using their charts, models, radiographs, andintraoral photographs. The chi-square test, the binomial test, and the relative risk assessment were used.Results: There was a male dominant tendency in both UCLP (P �.001) and UCLA (P �.05) patients. TheUCLP patients were 1.3 times more involved on the left side and had 2.2 times more congenital missing MLIthan did the UCLA patients. When an MLI was present, malformation occurred more frequently than normalshape in the UCLA (P �.001) and UCLP (P �.01) patients. Incidence of supernumerary teeth was 4.6 timeshigher in UCLA than in UCLP patients. Conclusions: When the cleft extended to the secondary palate,left-sided involvement was more predominant than in UCLA patients. When cleft involvement was confinedto the primary palate, present MLIs were more common than congenitally missing teeth, and supernumeraryteeth were more prevalent than in UCLP patients. These are important characteristics to be considered in the

diagnosis and treatment planning of cleft patients. (Am J Orthod Dentofacial Orthop 2006;130:752-8)

Cleft lip and palate (CLP) is a common congen-ital craniofacial deformity. The frequency ofclefting is higher in Asian people than other

races.1,2 Clefts are caused by the failure of fusion betweenthe medial nasal process and the maxillary process, orbetween the palatal processes. These failures are theresult of genetic and environmental factors.3,4

Dental abnormalities such as hypodontia, malfor-mation, and abnormal eruption pattern occur frequentlyin cleft patients.5-11 The permanent maxillary lateralincisor (MLI) was of particular interest in studies ofcleft patients because of its esthetic and functional role.A congenitally missing MLI on the cleft side is themost common finding in those patients.8,12-16 A super-numerary tooth in the cleft region is the second most

From the Department of Orthodontics, College of Dentistry, Seoul NationalUniversity, Seoul, Korea.aResident and postgraduate student.bAssociate professor.Reprint requests to: Seung-Hak Baek, Assistant professor, Department ofOrthodontics, College of Dentistry, Seoul National University, #28 Yeonkun-dong, Jongro-ku, Seoul, 110-749, Korea; e-mail, drwhite@unitel.co.kr.Submitted, December 2004; revised and accepted, February 2005.0889-5406/$32.00Copyright © 2006 by the American Association of Orthodontists.

doi:10.1016/j.ajodo.2005.02.029

752

common anomaly.8,14,17-19 The patterns of dentalanomalies in the cleft area are important for accurate,timely, and effective orthodontic treatment planning.

Although there have been many studies on dentalanomalies in cleft patients, most included differenttypes of clefts in the study sample, making informationabout a specific pattern for each cleft type difficult toascertain.8,20-22 Because of small sample sizes in theprevious studies, statistically significant differencescould not be obtained.8,20-22 Moreover, there wasno consideration of the developmental etiology of thecleft.23 T h e cause and time of formation of clefts vary;cleft lip and alveolus (CLA) results from fusion failurebetween the medial nasal process and the maxillaryprocess in the primary palate (lip and premaxilla)during the fourth to the seventh weeks of gestation.Cleft palate (CP) results from fusion failure betweenthe palatal processes in the secondary palate during theseventh to the twelfth weeks. Therefore, a developmen-tal classification is needed for the epidemiologic studieson CLP.

In addition, well-defined criteria for tooth determi-nation are lacking. Because radiographic images in the

cleft area are often distorted,6,17 it is difficult to

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Kim and Baek 753

distinguish a malformed MLI from a supernumerarytooth.10,15,24 Therefore, well-established criteria areneeded to distinguish a congenitally missing MLI froma supernumerary tooth on the cleft side.

The purpose of this study was to investigate thedifferences in the prevalence of cleft sidedness, con-genitally missing and malformed permanent MLIs, andsupernumerary teeth between unilateral CLA (UCLA)and unilateral CLP (UCLP) in a sample of Koreanpatients.

MATERIAL AND METHODS

A total of 690 Korean children with clefts visitedthe Department of Orthodontics at Seoul NationalUniversity Dental Hospital from January 1999 to De-cember 2003. Among them, 6 unilateral cleft lip onlypatients were excluded because of the small numbers;bilateral cleft patients were excluded because of thewide range in severity of the clefts on both sides; andpatients with CP only were also excluded because thecleft did not involve the alveolar ridge in the primarypalate. None of the subjects had other known syn-dromes, such as Van der Wöude syndrome or PierreRobin sequence.

The prevalence of hypodontia in the region outsidethe cleft is common. Congenitally missing premolarsand the MLI on the noncleft side could have differentgenetic and environmental etiologies than a congeni-tally missing MLI on the cleft side.25 Therefore, thepatients with congenitally missing teeth except the MLIon the cleft side were excluded to investigate the effectof the cleft itself on the MLI on the cleft side.

The calcification of the MLI tooth germ begins at10 to 12 months after birth, and complete crowncalcification of the MLI occurs 4 to 5 years after birth.Because the formation of the MLI crown can beidentified 6 years or later after birth, the subjects rangedin age from 6.0 to 13.0 years, with an average of 8.53years in this study. They included those in the earlymixed dentition to the permanent dentition.

The following established criteria were used todetermine congenitally missing MLIs and the presenceof supernumerary teeth on the cleft side.26 Our studyconsidered the MLI as a single tooth near the cleft onthe mesial or the distal side. Any morphology wasaccepted. These criteria were chosen because it wasassumed that the tooth bud of an MLI can develop ateither the mesial or the distal side of the cleft. Further-more, the tooth on the cleft side is almost certain to bean MLI, not a supernumerary canine.27 Therefore, if the

tooth was present on the cleft side, it was regarded as an

MLI, and subjects with supernumerary teeth on thecleft side only were selected. If 2 teeth were betweenthe maxillary permanent central incisor and the canine,the smaller and more deformed tooth was defined as thesupernumerary tooth.

Malformation of the MLI was defined as a tooththat is morphologically abnormal in shape, such as peglateralis, conical, or canine shaped.27 In addition, asupplemental tooth with a crown shape similar to anMLI, but 30% smaller than the antimere in the orth-odontic models, radiographs, and intraoral photo-graphs, was also considered as a malformation in thisstudy.

As a result, the records of 75 patients with UCLA(49 male, 26 female) and 129 patients with UCLP (92male, 37 female) were selected as our final sample.Using the patients’ orthodontic and cleft charts, diag-nostic models, orthopantomograms, maxillary occlusalfilms, periapical films, and intraoral photographs, weinvestigated the prevalence of cleft sidedness, congen-itally missing and malformed MLIs, and the presenceof supernumerary teeth on the cleft side; 1 observer(N.Y.K.) reassessed the data again two weeks later. Themeasure of agreement showed no difference betweenthe 2 assessments (� � 0.95); therefore, the laterassessment was used. The relationships among clefttypes, sex, sidedness, congenitally missing or presentMLIs, crown shape of MLI, and presence of supernu-merary teeth were analyzed by chi-square and binomialtests, and the relative risk assessment was used tocompare the frequency of the data.

RESULTS

Male sex had a higher tendency for UCLP (P�.001) and UCLA (P �.05). There was no statisticallysignificant difference in the male dominant patternbetween 2 groups (Fig 1).

Although the UCLA patients did not show anydifference in distribution of cleft sidedness, the UCLPpatients had a significantly higher incidence on the leftside than on the right (P �.001). The UCLP patientsdemonstrated left-sided dominance more than did theUCLA patients (P �.05) and were 1.3 times moreinvolved on the left side than the UCLA patientsaccording to the relative risk assessment (Fig 2).

In the UCLA patients, MLIs were more commonthan congenitally missing MLIs (P �.001). However,among the UCLP patients, there was no statisticaldifference in the frequency of congenitally missing andpresent MLIs. There was a significant difference in thefrequency of congenitally missing and present MLIs

between the UCLA and the UCLP patients (P �.001).

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754 Kim and Baek

The UCLP patients had 2.2 times more congenitallymissing MLIs than did the UCLA patients (Fig 3).

When the MLI was present on the cleft side,malformation occurred more frequently than normalshape, regardless of the cleft type, in both the UCLA(P �.001) and UCLP (P �.01) patients (Fig 4).

Between sexes, there was no significant differencein the congenitally missing or present MLIs in the

Fig 1. Distribution of sex by cleft type: UCLA, unilateralcleft lip and alveolus; UCLP, unilateral cleft lip andpalate. Binomial test for sex analysis (P � .011 for UCLAand P � .000 for UCLP patients, *P �.05, **P �.01,***P �.001). Chi-square test for analysis of UCLA andUCLP according to sex, �2 � 0.796, P � .372.

Fig 2. Distribution of cleft sidedness by cleft type.Binomial test for cleft sidedness analysis (P � .818 forUCLA and P � .000 for UCLP patients, *P �.05, **P�.01, ***P �.001). Chi-square test for analysis of UCLAand UCLP according to cleft sidedness (aP �.05, bP�.01, cP �.001), �2 � 4.789, P � .029. �relative risk ofUCLP over UCLA on left side was 1.30 (95% CI: about1.012-1.663).

UCLP patients (Table I). However, in the UCLA

patients, the MLI was more frequently present in malesthan in females (P �.001) (Table II).

In males, there was a significant difference in thedistribution of congenitally missing and present MLIsbetween the UCLA and the UCLP patients (P �.001),and the male UCLP patients had 2.7 times morecongenital missing MLIs than the UCLA patients(Table III). However, in the females, there was no

Fig 3. Distribution of present or congenitally missingMLIs by cleft type. Binomial test to analyze difference inUCLA and UCLP (P � .000 for UCLA and P � .725 forUCLP patients, *P �.05, **P �.01, ***P �.001). Chi-square test to analyze differences in UCLA and UCLP(aP �.05, bP �.01, cP �.001), �2 � 15.23, P � .000.�Relative risk of UCLP over UCLA was 2.17 (95% CI:about 1.400-3.345).

Fig 4. Distribution of normal shape and malformation ofMLIs by cleft type. Binomial test to analyze differencesbetween cleft side in UCLA and UCLP subjects (P �.000 for UCLA and P � .001 for UCLP patients, *P �.05,**P �.01, ***P �.001). Chi-square test to analyze differ-ence between UCLA and UCLP in normal shape ormalformation, �2 � 0.109, P � .741.

significant difference between the 2 groups (Table IV).

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Although the presence of supernumerary teeth wassignificantly lower in both groups (P �.001), theincidence of supernumerary teeth was more prevalentin the UCLA patients than in the UCLP patients (P�.05) and 4.6 times higher in the UCLA patients thanin the UCLP patients (Fig 5).

DISCUSSION

Cleft lip (CL) and CLP are known to be morecommon in males, with CP only more common infemales. Cooper et al28 reported the ratio of males tofemales as 1.6:1 for CL and CLP and 1:1.3 for CP.However, Baek et al23 grouped Korean cleft patientsaccording to the developmental classification and re-

Table I. Distribution of present or congenitally missingMLIs in UCLP patients by sex

Tooth Male (n) Female (n) Total (n)

Present 46 (50.0%) 16 (43.24%) 62 (48.06%)Congenitally missing 46 (50.0%) 21 (56.76%) 67 (51.94%)Total 92 (71.32%) 37 (28.68%) 129 (100%)

Binomial test to analyze difference on cleft side in UCLP patients(P � 1.00 for males, P � .511 for females). Chi-square test toanalyze difference between male and female UCLP patients, �2 �0.483, P � .487.

Table II. Distribution of present or congenitally missingMLIs in UCLA patients by sex

Tooth Male (n)*** Female (n) Total (n)

Present 40 (81.63%) 17 (65.38%) 57 (76.0%)Congentially missing 9 (18.37%) 9 (34.62%) 18 (24.0%)Total 49 (65.33%) 26 (34.67%) 75 (100%)

Binomial test to analyze difference on cleft side in UCLA patients(P � .000 for male and P � .169 for female patients; *P �.05,**P �.01, ***P �.001). Chi-square test to analyze differencebetween male and female UCLA patients, �2 � 2.459, P � .117.

Table III. Distribution of present or congenitally miss-ing MLIs in male subjects by cleft type

Toothc UCLA (n)*** UCLP (n) Total (n)

Present 40 (81.63%) 46 (50.00%) 86 (60.99%)Congenitally missing 9 (18.37%) 46 (50.00%)† 55 (39.01%)Total 49 (34.75%) 92 (65.25%) 141 (100%)

Binomial test to analyze difference on cleft side in UCLA and UCLPpatients (P � .000 for UCLA and P � 1.00 for UCLP patients;*P �.05, **P �.01, ***P �.001). Chi-square test to analyzedifference between male UCLA and UCLP patients (aP �.05,bP �.01, cP �.001), �2 � 13.48, P � .000.†Relative risk of UCLP over UCLA patients for missing MLI was2.72 (95% CI: about 1.458-5.084).

ported that the ratios of males to females were about

2.1:1 for UCLA and 2.75:1 for UCLP. In our study, theratios of males to females were 1.88:1 for UCLA and2.49:1 for UCLP, again showing the male-dominanttendency in UCLP (P �.001) and UCLA (P �.05)patients (Fig 1). Although there was no statisticallysignificant difference in sex distribution between theUCLA and the UCLP patients, there was a highertendency for male dominance in the UCLP patients(Fig 1).

In studies of Korean unilateral cleft patients, left-sided involvement was found to be about 65% to70%.23,29,30 In studies of other races, Fraser31 reportedthe prevalence of left-sided clefts to be 66.6%, andWilson32 and Drillien et al33 both reported it as 60%.Our results showed that the prevalence of left-sidedclefts in the UCLP patients was 67.4% (Fig 2); this was

Table IV. Distribution of present or congenitally miss-ing MLI in female subjects by cleft type

Tooth UCLA (n) UCLP (n) Total (n)

Present 17 (65.38%) 16 (43.24%) 33 (52.38%)Congenitally missing 9 (34.62%) 21 (56.76%) 30 (47.62%)Total 26 (41.27%) 37 (58.73%) 63 (100%)

Binomial test to analyze difference on cleft side in female UCLA andUCLP patients (P � .169 for UCLA and P � .511 for UCLPpatients). Chi-square test to analyze difference between femaleUCLA and UCLP patients, �2 � 3.00, P � .083.

Fig 5. Distribution of absence and presence of super-numerary teeth by cleft type. Binomial test to analyzedifference in UCLA and UCLP subjects (P � .000 forUCLA and P � .000 for UCLP patients, *P �.05, **P�.01, ***P �.001). Chi-square test to analyze differencebetween UCLA and UCLP in absence or presence ofsupernumerary teeth (aP �.05, bP �.01, cP �.001), �2 �6.486, P � .011. �relative risk of UCLA over UCLP withsupernumerary tooth was 4.59 (95% CI: about1.255-16.763).

similar to the other Korean studies.23,29,30 However, in

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756 Kim and Baek

our UCLA patients, there was no statistically signifi-cant difference in the distribution of cleft sidedness (Fig2). When the degree of cleft involvement extendedfrom the primary to the secondary palate, the UCLPpatients had a more predominant pattern of left-sidedinvolvement than did the UCLA patients (P �.05) andwere 1.3 times more involved with the left side thanwere the UCLA patients (Fig 2). Baek et al23 suggestedthat the incidence of the left-sided cleft increased fromCL to CLA to CLP in ascending order; this was similarto the tendency found in this study.

The deficiency of the blood supply near the cleft,either congenital or as a result of surgery,34 or adeficiency in the mesenchymal support to the MLI nearthe cleft,19,34 could account for the high prevalence ofcongenitally missing MLIs. Töndury35 reported thatdental lamina differentiation into tooth germs occurredafter the establishment of a cleft. Because deficiency ofthe mesenchyme can lead to insufficient mesenchymalsupport to the bud of the MLI, cleft patients with severedeficiency of mesenchymal mass would be likely tohave congenitally missing MLIs.15

In the normal population, the frequency of congen-itally missing MLIs was about 0.64% to 2.2%.36-41 Theprevalence of congenitally missing MLIs in cleft pa-tients is known to be higher than in the generalpopulation.5,9,42,43 In this study, an MLI was congeni-tally missing in 41.7% of the total unilateral cleftpatients.

The prevalences of congenitally missing MLIs were24.0% in the UCLA group and 51.9% in the UCLPgroup (Fig 3). The rate in the UCLP patients of thisstudy was similar to those studied by Tsai et al19

(51.8%) and Ribeiro et al44 (49.8%). However, theprevalence we found was lower than that reported byShapira et al21 (74% of 278 patients with CL, CP, orCLP), by Kang et al10 (61.4% of 70 patients withunilateral cleft), and by Baek and Yang24 (61.2% of116 patients with UCLP, 43.2% of 37 patients withUCLA). These differences can be explained by thedifferent criteria for congenitally missing or presentMLIs in those studies and ours. In the study of Shapiraet al,21 the types of cleft samples were mixed, and, inthose of Kang et al10 and Baek and Yang,24 obviouslymalformed MLIs were considered supernumerary teeth.In this study, if any tooth on the cleft side was presentregardless of its shape or position, it was considered anMLI.

When the degree of cleft involvement was confinedto the primary palate, the presence of MLI was morecommon than congenitally missing teeth in the UCLApatients (P �.001) (Fig 3). In addition, the UCLA

patients had a more dominant pattern for the presence

of MLIs on the cleft side than the UCLP ones (P�.001) (Fig 3). However, when the degree of cleftinvolvement extended from the primary to secondarypalate, the subjects with UCLP had 2.2 times morecongenitally missing MLIs than did the UCLA patients(Fig 3).

When an MLI is on the cleft side, it usually has anabnormal size and shape.44,45 In this study, if an MLIwas on the cleft side, a malformed tooth was morefrequent than a normally shaped tooth in both theUCLA (P �.001) and the UCLP (P �.01) subjects (Fig4). Hellquist et al18 reported that only 6.2% of the 172children with CL with or without CP had teeth withnormal sizes and shapes. Kraus et al7 insisted that mostpatients with CL only or CLP had some deformity ofthe anterior teeth near the cleft.

In this study, although there was no statisticaldifference in the frequency of congenitally missingMLIs by sex in the UCLP subjects, the percentage ofcongenitally missing MLIs was higher in females thanmales (Table I). Ranta15 reported a similar result to thisstudy. On the contrary, the UCLA patients (both sexes)had more present MLIs than congenitally missing teeth,especially the male UCLA patients (P �.001) (TableII). When we compared the male UCLP and UCLApatients, the UCLP patients had 2.7 times more con-genitally missing MLIs than did the UCLA patients (P�.001) (Table III). However, in the females, there wasno significant difference between the UCLA and theUCLP groups in spite of a reverse tendency (Table IV).

There are several hypotheses about the cause ofsupernumerary teeth in cleft patients. One is the length-ening of the precanine section of the oral epithelium,because a cleft lengthens this area. Extension of thedental lamina could develop into a supernumerary toothinstead of being resorbed.15,46 Another thought is thatthe supernumerary tooth develops from the epithelialremnants of the dental lamina.47 A third hypothesis isthat the cleft directly causes the tooth germ to split andthe supernumerary tooth to develop.15,48,49

Supernumerary teeth were found in 5.4% of thesubjects in this study. This was lower than the 26.8% inthe study of Kang et al,10 in which all supernumeraryteeth both inside and outside the clefts were counted.However, the total incidence was higher than thefrequency of supernumerary teeth in normal Koreanchildren (2.75%)50 and was similar to that found byNagai et al,6 who also found a higher incidence ofsupernumerary teeth in cleft patients than in normalpeople. Swanson et al42 reported that a supernumerarytooth is related to the cleft site, and Kraus et al7

proposed that supernumerary teeth occur more fre-

quently in the MLI region adjacent to the cleft.

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Kim and Baek 757

Nagai et al6 reported that the frequency of asupernumerary tooth was higher in an incomplete cleftthan in a complete cleft. Baek and Yang24 reported thatthe incidences of supernumerary teeth were 13.5% in37 UCLA patients and 9.5 % in 116 UCLP patients. Inour study, the incidence in the UCLA group (10.7%)was higher than in the UCLP group (2.3%). The UCLApatients had nearly 4.6 times more supernumerary teethon the cleft sides than did the UCLP patients (Fig 5).Baek and Yang24 reported the descending order to beCL, CLA, CP, and CLP. Therefore, when cleft involve-ment was confined to the primary palate, supernumer-ary teeth were more prevalent in the UCLA patients.

There are limitations in generalizing the resultsfrom this study because of the small number of patients.Therefore, we believe that a multi-center study with alarger sample size is required.

CONCLUSIONS

When cleft involvement was confined to the pri-mary palate, the presence of a MLI was more commonthan a congenitally missing tooth, and supernumeraryteeth were more prevalent in the UCLA patients than inthe UCLP ones. When the primary and secondarypalate were involved, the left-sided involvement wasmore predominant in the UCLP patients than in theUCLA ones. These are important characteristics to beconsidered in the diagnosis and treatment planning ofcleft patients.

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