HomeBlogБез категорияIs the presence of Simonart’s band in patients with complete unilateral cleft lip and palate associated with the prevalence of missing maxillary lateral incisors?

Is the presence of Simonart’s band in patients with complete unilateral cleft lip and palate associated with the prevalence of missing maxillary lateral incisors?

Is the presence of Simonart’s band in patients
with complete unilateral cleft lip and palate
associated with the prevalence of missing
maxillary lateral incisors?

Marılia Sayako Yatabe,a Daniela Gamba Garib,b Guilherme Janson,c Raquel Silva Poletto,d
and Terumi Okada Ozawae
Bauru, S~ao Paulo, Brazil

Introduction: The aim of this study was to compare the prevalence of agenesis of the maxillary lateral incisors in the cleft area of patients with unilateral cleft lip and palate with and without Simonart’s band. Methods: A sample of panoramic radiographs of 121 patients with a mean age of 7 years was divided into 2 groups: group 1 included 60 patients with Simonart’s band, and group 2 included 61 patients without Simonart’s band. Patients with syndromes
were not included. Chi-square tests were used for intergroup comparisons (P\0.05). Results: In the pooled subgroup, the prevalences of maxillary lateral incisor agenesis, supernumerary maxillary lateral incisors, 1 maxillary lateral incisor mesial to the cleft, and 1 maxillary lateral incisor distal to the cleft were 40.5%, 12.5%, 8.2%, and 38.8%, respectively. In group 1, these frequencies were 35%, 10%, 6.7%, and 48.3%; in group 2, they were 45.9%, 13.1%, 11.5%, and 29.5%. There was a statistically significant difference between the groups for the prevalence of a maxillary lateral incisor distal to the cleft. Conclusions: The presence of Simonart’s band is associated with a higher frequency of maxillary lateral incisor development in the maxillary process. (Am J Orthod Dentofacial Orthop 2013;144:649-53)

From the University of S~ao Paulo, Bauru, S~ao Paulo, Brazil. aPostgraduate student, Department of Orthodontics, Bauru Dental School.
bAssociate professor, Department of Orthodontics, Hospital of Rehabilitation of Craniofacial Anomalies, Bauru Dental School.
cProfessor, Department of Orthodontics, Bauru Dental School. 
dResident, Hospital of Rehabilitation of Craniofacial Anomalies.
eHead, Dentistry Division, Hospital of Rehabilitation of Craniofacial Anomalies.
All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.
Address correspondence to: Marılia Sayako Yatabe, Alameda Octavio Pinheiro Brisolla, 9-75, 17012-901, Bauru, S~ao Paulo, Brazil; e-mail, msyatabe@
yahoo.com.br. 
Submitted, December 2012; revised and accepted, June 2013.
0889-5406/$36.00
Copyright  2013 by the American Association of Orthodontists.
http://dx.doi.org/10.1016/j.ajodo.2013.06.018

Practical Procedures & AESTHETIC DENTISTRY

It has been proposed that clefting is part of a complex malformation associated with other dental anomalies. 1 According to Hoffmeister’s genetic study,
some microsymptoms such as hypodontia, hyperodontia, fusion of teeth, and twin formation have a common genetic background. Since the cleft is located at the border of the primary and secondary palates, dental anomalies in this area are common.1 Previous embryologic studies have demonstrated
that the maxilla is derived from the maxillary process, which originates from the first pharyngeal arch, called the maxillary growth center, and the premaxilla, which originates from the frontonasal prominence and part of the lateral nasal prominence.2 During prenatal development, the medial part of the maxillary process delivers material to the future premaxilla.3 Therefore, after ossification, the incisive suture delimitating the posterior and anterior segments of the maxilla is positioned more mesially than is the fusion site between the premaxilla and the maxillary processes.2 In 3-dimensional reconstructions, it was possible to observe 2 thickenings of the dental epithelium originating independently from the medial nasal and maxillary
processes separated by a narrow groove.3 The fusion site of the dental epithelia was detectable as a furrow on the germ of the lateral incisor.3 Therefore,
the mesial half of the maxillary lateral incisor might derive from the premaxilla, and the distal half of maxillary lateral incisor might derive from the maxillary process.
This presumed double origin of the lateral incisor could explain the high frequency of dental anomalies of number observed in patients with cleft lip and palate. Those with complete unilateral cleft lip and palate might have agenesis of the maxillary lateral incisors in the cleft region, supernumerary maxillary lateral incisors (1 mesial and 1 distal to the cleft region), or only 1 maxillary lateral incisor that might be positioned mesially or distally to the cleft. The prevalence of these anomalies might be associated with the degree of hypoplasia of the facial processes. In patients with unilateral cleft lip and palate, it is common to observe a tissue known as Simonart’s band (Fig 1). This band is a tissue originating from a supplementary growth center of the maxillary process, called maxillary prime, which grows to form a bridge between the premaxilla and the lateral nasal prominence.2 The prevalence of Simonart’s band in patients with unilateral cleft lip and palate is approximately 20%.4 The presence of this band might mean fewer hypoplastic embryologic processes.3 Hence, a smaller prevalence of agenesis of  maxillary lateral incisors distal to the cleft can be expected in patients with Simonart’s band. However, no previous studies have investigated these associations. The aim of this study was to verify the prevalence of maxillary lateral incisor agenesis at the cleft area in patients with unilateral complete cleft lip and palate, comparing patients with and without Simonart’s band. The null hypothesis tested in this study was that those with and without Simonart’s band have the same prevalence of dental anomalies related to
maxillary lateral incisors at the cleft area.

Fig 1. Examples of small, medium, and large Simonart’s bands from anterior and occlusal aspects.

MATERIAL AND METHODS

From an initial sample of 275 patients with unilateral complete cleft lip and palate (born between 1989 and 1992) from the files of the Hospital of Rehabilitation of Craniofacial Anomalies, University of S~ao Paulo in Brazil, all patients with Simonart’s band (n561) were selected. A control group of 61 patients without Simonart’s band was randomly selected from the same initial sample, matched by age and sex according to chi-square tests. One patient was excluded from the experimental group because of an incomplete set of intraoral photographs. Therefore, the sample included 121 patients with unilateral cleft lip and palate in the mixed dentition (36 girls, 85 boys) with ages ranging from 5 to 9 years. The radiographs were taken before the prebone graft orthodontic treatment. The exclusion criterion was patients with syndromes. Facial and intraoral photographs were analyzed to verify the presence of Simonart’s band. The sample was divided into 2 groups: group 1 comprised 60 patients with Simonart’s band with a mean age of 7 years and a
male:female ratio of 3:1, and group 2 comprised 61 patients without Simonart’s band with a mean age of 7 years and a male:female ratio of 2:1. Using panoramic and periapical radiographs, the maxillary lateral incisor in the cleft area was classified into 4 categories based on the distribution pattern of
the cleft side according to the methodology established by Dentino et al5: subgroup M, subjects with 1 tooth located on the mesial side of the alveolar cleft; subgroup D, subjects with 1 tooth located on the distal side of the alveolar cleft; subgroup MD, subjects with 2 teeth, 1 mesial and 1 distal to the cleft; and subgroup ABS, subjects with congenital absence of teeth in the cleft area (Fig 2). The prevalence of these 4 situations was calculated for both groups and for subgroups M, D, and MD pooled. The chi-square test was used for the intergroup comparison (P\0.05). Based on the desired sample comparison in the study, and at an alpha value of 0.05, a sample size of 60 subjects for each group was found to provide a power of 0.70.

RESULTS

The Table shows the intergroup comparison for the prevalences in subgroups M, D, MD, and ABS. The patients with Simonart’s band demonstrated a higher prevalence of 1 maxillary lateral incisor located on the distal side of the alveolar cleft, compared with the patients without Simonart’s band.

Fig 2. Classification of the position of the lateral incisors: A, absence of lateral incisors; B, supernumerary teeth (1 lateral incisor mesial and the other distal to the cleft); C, a lateral incisor only mesial to the cleft; D, a lateral incisor only distal to the cleft.

DISCUSSION

There are several studies on dental anomalies in patients with cleft lip and palate. However, no previous studies have verified the association between Simonart’s band and dental anomalies of the maxillary permanent lateral incisors in patients with unilateral complete cleft lip and palate.6-10 Conversely, some studies have excluded or separated patients with bands from the complete sample.5,11-13 The results showed that at least 1 maxillary lateral incisor was present in the cleft area in 59.5% of the patients (Table), corroborating previous studies that found prevalences varying between 50.2% and 61.8%.10,14,15 On the other hand, Cassolato et al16 observed a smaller prevalence compared with our study (24.1%).
The variability in the number of maxillary lateral incisors and the position relative to the cleft for the maxillary lateral incisors could be explained by the double embryologic origin of these teeth.3,17 In the pooled subgroup, the most frequent situation was agenesis of the maxillary lateral incisors in the cleft area, observed in 40.5% of our subjects (Table). These findings agree with those of previous studies, which indicated a high prevalence of tooth agenesis in patients with complete clefts.18-20 The second most common situation in the pooled subgroup was only 1 maxillary lateral incisor distal to the cleft (38.8%). According to previous studies and in agreement with our findings, when the maxillary lateral incisor is present in patients with
unilateral cleft lip and palate, teeth distal to the cleft are the most common finding.10,14,15 The third most common situation was 2 maxillary lateral incisors at both sides of the cleft (mesial and distal), observed in 11% of the sample. The least common situation was only 1 maxillary lateral incisor located mesial to the cleft, observed in 9.1% of the pooled subgroup. During prenatal development, the medial part of the maxillary process delivers material to the distal regions of the future premaxilla.3,21,22 There is evidence that incisive sutures develop distally from the location where the medial nasal prominence and the maxillary process fuse.14,17,21,22 These explanations elucidate the common observation of a lateral incisor distal to the
alveolar cleft. In previous studies, the maxillary lateral incisor dental lamina was not found only in the premaxillary segment but was constituted from 2 parts separated by a narrow gap at the site of the early fusion of the medial nasal and maxillary processes.17,23,24 Computer-aided 3-dimensional reconstruction studies found that between days 40 and 42, the medial nasal and maxillary processes are already fused, but the dental epithelia are not. By day 44, it was possible to see that the dental epitheliumhas formed a continuous dentalmound with a clearly detectable fusion site.3 This fusion of facial processes before that of the dental epithelium also explains the occurrence of maxillary lateral incisor supernumerary teeth in patients without clefts.3 By means of scanning electron microscopy, histology, skeletal staining, and drying techniques, Wei et al17 evaluated the formation of the maxilla in monkeys with clefts and found that the maxillary lateral incisor dental lamina is derived from lateral outgrowth of the premaxilla and the maxillary
process.
In patients with Simonart’s band (group 1), the most common situation was the maxillary lateral incisor distal to the cleft (48.3%) followed by agenesis (35%), the maxillary lateral incisor mesial and distal to the cleft (10%), and the maxillary lateral incisor only mesial to the cleft (6.7%) (Table). A different situation was found in patients without Simonart’s band (group 2); they had, in a decreasing sequence, agenesis of the maxillary lateral incisor (45.9%), the maxillary lateral incisor distal to the cleft (29.5%), the maxillary lateral incisor mesial and distal to the cleft (13.1%), and the maxillary lateral incisor only mesial to the cleft (11.5%). There was a statistically significant intergroup difference for the prevalence of the maxillary lateral incisor distal to the cleft (Table). The increased prevalence of the maxillary lateral incisor distal to the cleft in patients with Simonart’s band corroborates the previous suggestion that the maxillary process is less hypoplastic in these patients compared with patients without bands.2 Nevertheless, the similarity of the prevalence of the maxillary lateral incisor mesial to the cleft between groups 1 and 2 corroborates the hypothesis of the double origin of the maxillary lateral incisor; this means that development of the maxillary lateral incisor mesial to the cleft originates from the medial nasal process.3,17
The maxilla is basically formed by fusion of the paired medial nasal and maxillary processes. However, during prenatal development, the medial part of the
maxillary process delivers material to the distal regions of the future premaxilla,3,21,22 inducing the incisive sutures to develop distally from the location where the medial nasal prominence and maxillary process fuse.14,17,21,22 After ossification, the maxillary bone and the premaxilla are separated by the incisive suture. In 1948, Streeter25 described the developing maxilla formed by bilateral maxillary centers, bilateral supplementary maxillary centers, and bilateral premaxillary centers. Bilateral closure of the upper lip involves fusion of the bilateral premaxillary centers, bilateral supplementary maxillary centers, and ventral aspect of the lateral nasal process.25 When comparing mice with and without cleft lips at an early fetal stage, Sulik2 found that the bilateral supplementary maxillary centers and the ventral aspect of the lateral nasal process are distinct entities that can fuse, independently from
each other, with the bilateral premaxillary centers. During lip formation, the bilateral maxillary centersbilateral premaxillary centers fusion overlaps that of
the bilateral supplementary maxillary centers/ventral aspect of the lateral nasal process-bilateral premaxillary centers.2 In patients with cleft lip, the bilateral maxillary centers-bilateral premaxillary centers fusion does not occur, but the bilateral supplementary maxillary centers-bilateral premaxillary centers or the ventral aspect of the lateral nasal process-bilateral premaxillary centers fusion might occur, resulting in Simonart’s band (Fig 3).
In patients with Simonart’s band, a less hypoplastic tissue is expected in the maxillary process, with a higher prevalence of teeth in the cleft area.2 Our results corroborated this hypothesis, showing an increased prevalence of maxillary lateral incisors distal to the cleft in patients with Simonart’s bands. More specifically, evaluating electron micrographs, Sulik2 suggested that the maxillary lateral incisor has its origin in the bilateral supplementary
maxillary centers; this agrees with our findings that the maxillary lateral incisor distal to the cleft has a higher prevalence in patients with Simonart’s
band. Interestingly, maxillary lateral incisor agenesis (subgroup ABS) was more frequent in patients without Simonart’s band compared with patients with bands, but not significantly (Table). As expected, patients with Simonart’s band in this study showed a higher prevalence of the maxillary lateral
incisor (48.3%), suggesting a less hypoplastic tissue in the maxillary process.2 A possible explanation for this result is that when the embryonic maxillary process has a tissue volume deficiency, odontogenesis could be negatively influenced because teeth have the same ectomesenchymal origin as do the maxillary soft and hard tissues. Another hypothesis is that Simonart’s band and the presence of a distal maxillary lateral incisor represent a milder phenotype expression of the same genes related to an oral cleft and tooth agenesis. However, no genetic studies relating Simonart’s band and tooth agenesis were found. There seems to be an association between tissue hypoplasia of the embryonic maxillary process, Simonart’s band, and the maxillary lateral incisor distal to the cleft. Future studies should be conducted to confirm these assumptions.

Fig 3. Scanning electron micrographs of mouse embryos.
LN, Lateral nasal prominence; LNP, supplementary
lateral nasal prominence growth center; MAX,
maxillary prominence; MAX0, supplementary maxillary
growth center (reproduced with permission from Sulik2).

CONCLUSIONS

The null hypothesis was rejected. Patients with Simonart’s band have a higher prevalence of maxillary lateral incisors distal to the cleft compared with patients without Simonart’s band.

References

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