Analysis of permanent second molar development in children born with cleft lip and palate

Abstract The study of dental development in individuals born with cleft lip and palate (CLP) serves to determine when orthodontic intervention should start. Objective To evaluate the permanent second molar development in children born with cleft lip and palate according to Demirjian’s and Nolla’s methods. Methodology Out of a total of 513 digital panoramic radiographs, 113 pairs of children aged 3 to 16 years were selected. The exams were from children born with or without cleft lip and palate, of the same sex, with an age difference of up to 30 days. The images were analyzed by three examiners and reliability was checked through intra-examiner agreement by the Kappa test. The data were analyzed by Wilcoxon's and Mann-Whitney tests according to each dataset. Results The findings indicated delayed development of the permanent second molars in children with CLP (P<0.001). The development of the right permanent second molar was delayed compared to the left molar in children with CLP. Moreover, mandibular teeth showed significantly earlier development than maxillary teeth in both the case and control groups. There was no significant difference in the development of permanent second molars between sexes. Conclusion Children with CLP presented delay in the development of permanent second molars.


Introduction
Oral clefts are congenital malformations resulting from the non-closure of the frontonasal and maxillary processes during the first weeks of embryonic life. These conditions may manifest as an isolated phenomenon or in association with other congenital anomalies. 1,2 Cleft lip associated or not with cleft palate, and cleft palate alone, are among the most common congenital malformations worldwide, affecting 1 in 700 newborns. [3][4][5][6] These birth defects have been attributed to genetic and environmental factors. 7 Individuals with cleft lip and/or palate (CLP) experience significant impact in their quality of life. 8,9 Morphological alterations resulting from these conditions may cause functional and esthetic issues, which, most often, lead to psychosocial distress. 10 The extension and severity of the cleft will determine the nature of the issues, which generally include difficulty in breastfeeding, recurrent infections of the respiratory tract and middle ear, hearing and speech alterations, as well as occlusal and facial aesthetic problems. 10,11 Orthodontic interventions are required for the rehabilitation of individuals with CLP. 12 Nevertheless, very early orthodontic interventions should be avoided due to poor stability, which makes the rehabilitation process even more exhaustive for patients and their families. 10 Several currently available methods can be used to determine the patient's age or maturity of the dentition, most frequently Nolla's 13 (1960) and Demirjian's methods. [14][15][16] D e m i r j i a n 's m e t h o d 14    Nolla's methods. 13,14 The stages of development of Demirjian's method 14 were codified as follows: 1 for stage A, 2 for stage B, 3 for stage C, and so forth. Wilcoxon's test was used for inter-group comparisons. The differences between the groups (case and control) for the same method, between the arch sides for the same group, and between the methods, correspond to paired data, which justifies the use of the non-parametric paired Wilcoxon's test. Mann-Whitney's test, which is not a paired test, was used for comparison between sexes.
The data were statistically analyzed in SPSS version 21.0 (Statistical Package for the Social Sciences) with a 5% margin of error.

Results
As shown in Table 2       Nolla's methods 13,14 were chosen in our study for their broad applicability worldwide. 12,15,16,[18][19][20][21][22][23][24]26 While children with CLP are known to have normal genetic potential for growth, 27,28 some studies have demonstrated that they may present a delay in dental maturation. 19,20,24 The development of permanent dentition takes longer in children with CLP than otherwise and may be increased depending on the severity of the cleft. 22 In addition, eruption of the permanent teeth is slower on the side of the cleft. 29 Consistent with this, both methods in our study demonstrated a delay in the development of the permanent second molars in individuals with CLP, regardless of the cleft side, compared to those without any clefts.
Heterogeneous distribution of cleft types was present in our study sample, which included unilateral and bilateral CLP, unilateral cleft lip and cleft palate.

Conclusions
The dental development of permanent second molars by Demirjian's and Nolla's methods 13,14 is delayed in children born with cleft lip and palate.
Arch side-related differences in tooth development were observed in individuals with unilateral left cleft lip and palate, with delay most often observed on the right side, that is, on the non-cleft side.
Demirjian's (but not Nolla's) method revealed differences between maxillary and mandibular tooth development in both the case and control groups, but no differences were observed between sexes.

Acknowlegments
The authors are indebted to the participants of the study and the Smile Train for the support of the treatment of cleft lip and palate individuals.

Declaration of conflicting interests
The author(s) declare no potential conflicts of interest with respect to the study, authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the study, authorship, and/or publication of this article.