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An Uncommon Cleft Subtype of Unilateral Cleft Lip and Palate
1 First Department of Oral and Maxillofacial Surgery, Graduate School of Dentistry, Osaka University, 1-8 Yamadaoka, Suita, Osaka, Japan; and Correspondence: * corresponding author, yaman2{at}dent.osaka-u.ac.jp
The finding that the vomer plays a crucial role in maxillary growth suggests that the bilateral cleft configuration of unilateral cleft lip and palate (UCLP), in which the vomer is detached from the non-cleft-side secondary hard palate, negatively influences palatal development, and this hypothesis was tested. Sixty persons with complete UCLP, including those with the vomer detached from (n = 30, b-UCLP) and attached to (n = 30, u-UCLP) the secondary hard palate, were analyzed morphologically, with the use of cast models taken at 10 days, 3 mos, and 12 mos of age. The anterio-posterior palatal length at 12 mos of age in those with b-UCLP was significantly shorter than that in those with u-UCLP, by 8.7% (p < 0.05). In addition, palatal width development in the first year in those with b-UCLP was also significantly retarded. These results suggest that the uncommon bilateral cleft subtype in UCLP should be included in the cleft classification.
Key Words: UCLP • cleft subtype • palatal development
Among individuals with unilateral cleft lip and palate (UCLP), we can see a variance in the anatomical relationship between the vomer and the secondary hard palate. In most persons with UCLP, the vomer is attached to the secondary palate, being indicative of unilateral cleft in the secondary hard palate (u-UCLP). In some people with UCLP, the vomer is detached from the secondary hard palate, that is, these individuals present with bilateral clefts in the secondary hard palate (b-UCLP). Although cleft lip and palate is one of the most common congenital diseases affecting oral functions and facial development, little attention has been paid to this uncommon cleft subtype in UCLP. The vomer, which exists inferior to the nasal septum, is known to play an essential role in antero-posterior development of the palate (Friede, 1998). It has been reported that, in beagle pups, partial or entire resection of the vomer significantly reduces antero-posterior maxillary growth (Squier et al., 1985). Several studies have revealed that surgical procedures for cleft palate with the use of a vomer flap have a worse influence on the maxillary growth than those without a vomer flap (Delaire and Precious, 1985; Friede and Lilya, 1994; Tanino et al., 1997). Based on these investigations, we hypothesized that the bilateral cleft configuration in the secondary palate of persons with UCLP negatively influences palatal development. The bilateral cleft subtype of UCLP has also been little considered in the classification of cleft lip and/or palate. Many studies have developed classifications and representative methods for cleft lip and/or palate (Kernahan and Stark, 1958; Friedman et al., 1991; Schwartz et al., 1993; Mortier et al., 1997), but most have omitted this cleft subtype. Recently, Ortiz-Posadas et al.(2001) proposed a classification for clefts that includes a representation of bilateral cleft in the secondary hard palate. However, they intended to apply the category to persons with cleft palate alone, and did not mention the UCLP category including the bilateral cleft subtype. The aim of this study was to evaluate the palatal morphology of persons with b-UCLP and compare it with that of persons with u-UCLP. If those with b-UCLP possess characteristic features in the palatal developmental pattern, it is necessary for clinicians and researchers to clearly recognize this bilateral cleft subtype of UCLP.
Participants Sixty persons with complete UCLP were enrolled into this retrospective study. They were non-syndromic Japanese who had no known anomaly other than UCLP, and consecutive persons who were referred to two facilities—the First Department of Oral and Maxillofacial Surgery, Osaka University Graduate School of Dentistry (Facility A), and the Department of Oral and Maxillofacial Surgery, Osaka Medical Center and Research Institute for Maternal and Child Health (Facility B)—from March, 1996, to July, 2000. We divided them into two groups according to the morphological characteristics between the vomer and the secondary hard palate (Fig. 1  ): whether the vomer was detached from (b-UCLP group) or attached to (u-UCLP group) the non-cleft-side secondary hard palate. The b-UCLP group consisted of 30 children (15 from Facility A, 15 from Facility B; 18 boys, 12 girls; (cleft side) 9 right, 21 left). The u-UCLP group was comprised of 30 children (15 from Facility A, 15 from Facility B; 17 boys, 13 girls; (cleft side) 11 right, 19 left). Although the treatments were carried out in the two facilities independently, all persons were treated under the same protocol as described below. Briefly, they underwent early pre-surgical orthopedic treatment (Hotz and Gnoinski, 1979). The cleft lip was closed at 3 mos of age, according to the modified Millard method, by two oral and maxillofacial surgeons (MK from Facility A; JN from Facility B). The birthweight, the age at which early orthopedic treatment commenced, and the age at which the participants received cheiloplasty showed no statistical differences between the b-UCLP and u-UCLP groups (p = 0.39, p = 0.35, and p = 0.31, respectively) and between the two facilities (p = 0.25, p = 0.34, and p = 0.19, respectively). This study was approved by the Ethical Committee of Osaka University Graduate School of Dentistry and Osaka Medical Center and Research Institute for Maternal and Child Health.
Measurements We measured palatal dimensions using a consecutive series of dental cast models taken of study participants at 10 days (Stage 1), 3 mos (Stage 2), and 12 mos (Stage 3) of age. The ages at which the cast models were taken showed no statistical difference between the two groups (Stage 1, p = 0.36; Stage 2, p = 0.31; Stage 3, p = 0.32) and between the two facilities (Stage 1, p = 0.34; Stage 2, p = 0.19; Stage 3, p = 0.21). We set the reproducible reference mucosal points on the cast models according to previous studies (Kramer et al., 1996; Schliephake et al., 2006) and measured according to the following parameters (Fig. 2 ): antero-posterior length and transverse widths of the alveolar arch, segment and cleft widths, palatal heights (the distance between the levels of the cleft edges and the alveolar ridges), and slopes of palatal shelves. All of the measurements at stage 1 showed no significant differences between individuals from the two facilities. Since comparison of treatment outcomes between the two facilities was not the purpose of this study, we did not draw statistical comparisons of measurements at stages 2 and 3 between the facilities.
All measurements were performed by two observers with a three-dimensional measurement system (QM Measure, MITSUTOYO Co., Kasugai, Japan). In each model, series were measured twice by each observer, with a two-week interval between measurements. All models of one participant were measured in one session. No statistical differences were found in variable measurements between the two measurement times by each observer.
Statistics
Of the 315 persons with UCLP referred to the two facilities from March, 1996, to July, 2000, we found 30 individuals with bilateral cleft subtype. The occurrence of the cleft subtype was 9.5%.
In Stage 3, the b-UCLP group showed less antero-posterior alveolar arch length (23.1 ± 1.6 mm) than did the u-UCLP group (25.4 ± 1.4 mm), by 8.7% with statistical significance (p < 0.05) (Table
There were no significant differences between the two groups in all measurements involved in maxillary arch width throughout the ages measured, although the increment in TT' from Stage 1 to Stage 3 was 1.7 ± 2.5 mm (5.2%) in b-UCLP and 4.0 ± 2.8 mm (12.9%) in u-UCLP, indicating significant difference between the two groups (p < 0.05) (Fig. 3  ). In stages 2 and 3, the width of the major segment in b-UCLP (stage 2; 10.6 ± 1.8 mm, stage 3; 12.1 ± 1.4 mm) was significantly smaller than that in u-UCLP (stage 2; 12.8 ± 1.5 mm, stage 3; 14.8 ± 1.2 mm) (P < 0.05), whereas the widths in the minor segment showed no significant differences between the two groups in all stages (Table). Increments in major side-segment width from Stage 1 to Stage 3 were 2.6 ± 2.6 mm (27.4%) in b-UCLP and 3.6 ± 2.2 mm (33.0%) in u-UCLP, indicating no significant difference (p = 0.11) (Table).
In stage 3, u-UCLP showed significantly narrower cleft width (8.5 ± 2.1 mm) than b-UCLP (11.2 ± 2.6 mm) (P < 0.05) (Table
This is the first study to analyze the palatal morphology of an uncommon bilateral cleft subtype in persons with UCLP (b-UCLP). We demonstrated that persons with the bilateral cleft subtype of UCLP show more retarded palatal development, particularly in antero-posterior palatal development and the width of the major segment, than did UCLP persons with unilateral cleft in the secondary hard palate (u-UCLP) during the first 12 mos of age. Furthermore, the occurrence of the bilateral cleft subtype was 9.5% in our study, indicating that persons with the bilateral cleft subtype are not uncommon. Dental clinicians should clearly recognize this cleft subtype of UCLP in both clinical practice and research. The antero-posterior length in persons with b-UCLP at the age of 12 mos was smaller than that in persons with u-UCLP by 8.7%. Moreover, compared with persons with u-UCLP, the antero-posterior development of the alveolar arch 9 mos after cheiloplasty was significantly impeded in persons with b-UCLP. These results suggest that persons with b-UCLP possess less potential in antero-posterior palatal development and/or less resistibility against the backward force of oral muscles reconstructed by cheiloplasty than do persons with u-UCLP. Many studies have reported that the vomer plays an important role in antero-posterior maxillary growth (Delaire and Precious, 1986; Friede, 1998). Vomer resection resulted in severe developmental deterioration in the antero-posterior length of the maxilla in dogs (Wada et al., 1980, 1990). It is well-known that palatal surgical procedures with involvement of the vomer negatively influence maxillary development (Delaire and Precious, 1985; Friede and Lilja, 1994; Tanino et al., 1997). These investigations have supported the notion that the vomer-premaxilla suture is a developmental center of forward development of the maxilla. Meanwhile, our study demonstrated that the anatomical morphology of the posterior part of the vomer influences antero-posterior development of the palate. We believe that the posterior part of the vomer also plays an important role in palatal development, as an anchor that mechanically supports growth at the vomer-premaxilla suture. To convey endochondral bone growth at the vomer-premaxilla suture to the maxilla, the posterior part of the vomer would need to be fixed to the surrounding tissue. According to the septal-traction model that explains the mechanism of maxillary forward growth at an early age, the forward and downward growth of the nasal septum pulls the mid-face forward via the septopremaxillary ligament (Mooney and Siegel, 1986; Siegel et al., 1990). It also seems necessary for the vomer to be fixed to the secondary hard palate to convey the forward and downward growth of the nasal septum cartilage to the maxilla. Detachment of the vomer from the secondary hard palate possibly disturbs the sliding growth between the vomer and the maxilla that is observed in early childhood (Friede,1998). Nevertheless, we must closely follow the palatal development of UCLP persons with bilateral cleft in the secondary hard palate, because they have the potential to develop severe crossbite in the permanent dentition. Individuals with b-UCLP showed a narrower width in the major segment at the ages of 3 and 12 mos, and larger cleft width at 12 mos of age, than did those with u-UCLP. In addition, the slope in the major side palatal shelf of those with b-UCLP was steeper than that of those with u-UCLP at the age of 12 mos. Our results also demonstrated that the development of inter-maxillary tuberosity width for the first 12 mos is larger in individuals with u-UCLP than in those with b-UCLP. These results suggest that the vomer is involved in transverse palatal development. The configuration in which the vomer attaches to the secondary hard palate would enhance inward growth of the cleft margin on the major segment. The connection between the vomer and the osseous palate is made by the footplate of the vomer, which supports the lower part of the vomer and initiates ossification at late gestational age (Sandikcioglu et al., 1994). It has been reported that the development of the footplate is dependent on the coalescence of the soft-tissue palatal shelves with the nasal septum (Hansen et al., 2004). Moreover, since the lower part of the vomer presents a marked deviation toward the side at which articulation occurs between the vomer and osseous palate in persons with UCLP (Kimes et al., 1992), a possible development at the footplate should push and widen the major side osseous plate laterally. Development at the vomeral footplate may explain the better transverse palatal development in persons with u-UCLP than in those with b-UCLP. Further study is necessary to explain the phenomenon observed in our study. Many studies have attempted to classify and represent cleft lip and palate since the embryological classification by Kernahan and Stark (1958). Many clinicians now use a composite schematic representation based on the ‘striped Y’ approach. Recently, classifications that include a scoring concept in which the severity of the anatomical deformity is graded to predict the results of surgical treatments have been developed (Friedman et al., 1991; Schwartz et al., 1993; Mortier et al., 1997). Few classifications of cleft lip and palate, however, are able to represent an anatomical configuration of the secondary palate of persons with UCLP. To the best of our knowledge, only one representation method can represent bilateral cleft configuration in the secondary hard palate of persons with UCLP (Ortiz-Posadas et al., 2001). In the secondary palate section of their classification, those authors described bilateral and unilateral clefts, although they made no mention of the bilateral cleft subtype in UCLP. Based on the results described here, we believe that it is crucial for a classification of clefts to possess the ability to represent configurations in the secondary hard palate. In our study, we restricted participants to those with UCLP, but we can also see such a cleft subtype in the secondary hard palate in persons with cleft palate only or submucous cleft palate. It has been reported that, in 53% of persons with submucous cleft palate, the vomer did not fuse with the palatal shelves up to the incisive foramen (Grzonka et al., 2001). Further study is necessary to reveal the pattern of palatal development in persons with cleft palate alone or with submucous cleft palate.
The authors thank Dr. Takeshi Wada and Dr. Kanji Nohara for valuable advice. This research was supported by the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Scientific Research (B) (17390535, 2005), and the 21st Century COE entitled "Origination of Frontier BioDentistry" at Osaka University Graduate School of Dentistry, supported by the Ministry of Education, Culture, Sports, Science and Technology. Received for publication December 25, 2006. Revision received June 16, 2007. Accepted for publication October 17, 2007.
Journal of Dental Research, Vol. 87, No. 2,
164-168 (2008)
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