Assessing the prevalence of S-shaped root canal and associated genes in humans.

Background: Multiple signaling molecules have been shown to play crucial roles in dental root development. Therefore, we aimed to investigate the prevalence of S-shaped roots and also to investigate, if single nucleotide polymorphisms (SNPs) in BMP2, BMP4 and SMAD6 are associated with this phenotype in humans.
Methods: This is a cross-sectional phenotype-genotype association study that used radiographs to determine the phenotypes and DNA to investigate SNPs in candidate genes. During the radiographic exam, teeth presenting root canal(s) doubly curved were considered S-shaped roots. SNPs in BMP2 (rs1005464 and rs235768), BMP4 (rs17563) and SMAD6 (rs2119261 and rs3934908) were blindly genotyped by real-time PCR using TaqMan assay. The relative and absolute frequency of S-shaped roots were calculated. Chi-square test was used to compare the genotype distributions between control and S-shaped groups.
Results: Among the 578 subjects, 61 (10.6 %) presented at least one tooth with an S-shaped root. The most commonly affected type of tooth was the premolar. rs1005464 in BMP2 was statistically associated with an S-shaped root (p = 0.036). rs235768 in BMP2 was associated with an S-shaped root also in mandibular teeth (p = 0.017). A statistical significance was observed for the rs3934908 in SMAD6 (p = 0.049) for S-shaped root in the mandible. In the analysis stratified according to the type of tooth, rs235768 in BMP2 was associated with S-shaped roots in premolars (p = 0.029).
Conclusion: The prevalence of S-shaped roots is 10.6 % in permanent teeth. SNPs in BMP2 and SMAD6 could be involved in a higher chance to present S-shaped roots.
Competing Interests: Declaration of Competing Interest All authors have been personally and actively involved in substantial work leading to the paper, and will take public responsibility for its content.This material is the authors’ own original work, which has not been previously published elsewhere..
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