Abstract
Tooth agenesis is a common congenital anomaly in humans and is more common in oral cleft patients than in the general population. Many previous studies suggested that oral cleft and tooth agenesis share a similar genetic background. Therefore, this study explored the association between isolated tooth agenesis and genetic polymorphisms in genes that are crucial for craniofacial and tooth development. Panoramic radiographs, anamnesis, and genomic DNA from 273 patients were included. Patients were classified as tooth agenesis present, when at least one permanent tooth was congenitally missing. Patients with syndromes and oral cleft were excluded. Only unrelated patients were included. The genetic polymorphisms in BMP2 (rs235768 and rs1005464), BMP4 (rs17563), RUNX2 (rs59983488 and rs1200425), and SMAD6 (rs3934908 and rs2119261) were genotyped by real-time polymerase chain reaction. Genotype and allele distributions were compared between the tooth agenesis phenotypes and controls by Chi-square test. Haplotype and diplotype analysis were also performed, in addition to multivariate analysis (alpha of 0.05). A total of 86 tooth agenesis cases and 187 controls were evaluated. For the rs235768 in BMP2, patients carrying TT genotype have higher chance to present tooth agenesis [p < 0.001; prevalence ratio (PR) = 8.29; 95% confidence interval (CI) = 4.26–16.10]. The TT genotype in rs3934908 (SMAD6) was associated with higher chance to present third molar agenesis (p = 0.023; PR = 3.25; 95% CI = 1.17–8.99). BMP2 was also associated in haplotype and diplotype analysis with tooth agenesis. In conclusion, genetic polymorphisms in BMP2 and SMAD6 were associated with isolated tooth agenesis.
Highlights
Isolated tooth agenesis is one of the most common congenital defects in humans, which affects approximately 20% of the average worldwide population (Vastardis, 2000)
The allele T of the rs235768 in Bone morphogenetic protein 2 (BMP2) was associated with higher chance to present tooth agenesis in comparison with control group (p < 0.001; prevalence ratio (PR) = 3.45; 95% confidence interval (CI) = 2.54–4.70)
The T allele was associated with higher chance to present third molar agenesis (p < 0.001; PR = 4.30; 95% CI = 2.83–6.52) and other agenesis (p < 0.001; PR = 4.48; 95% CI = 2.78–7.21)
Summary
Isolated tooth agenesis (or congenitally missing teeth) is one of the most common congenital defects in humans, which affects approximately 20% of the average worldwide population (Vastardis, 2000). Tooth agenesis can be classified into two main types: non-syndromic and syndromic. Non-syndromic tooth agenesis involves a congenitally missing permanent or primary tooth or teeth in an isolated form without any other major birth defects, such as oral cleft and syndromes. Syndromic tooth agenesis refers to congenitally missing teeth associated with syndromes and oral clefts (such as cleft lip, clef palate, and cleft lip with palate) (Lu et al, 2016). Tooth agenesis is often observed in individuals with oral clefts (in the cleft area and in non-cleft areas) and their non-affected family members (Küchler et al, 2011). Several observational epidemiological and genetic studies suggest that oral clefts and isolated tooth agenesis share a similar genetic background (Phan et al, 2016)
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