Interleukin-1β (-31) Gene Polymorphism in Patients Exhibiting Short Tooth Roots

Objectives: IL-1β has been characterized as a potent bone resorptive cytokine and implicated as a key component of the complex pathways leading to tooth root resorption. IL-1β -31 C/T, a TATA-box single-nucleotide polymorphism, has been reported to alter the amount of IL-1β expression. Alterations in the expression of IL-1β may result in an individual’s predisposition to root resorption during orthodontic treatment. In the absence of genetic markers, pre-treatment radiographic evidence of short roots is the only indication of a predisposition to resorption during orthodontic treatment. The objective of this study was to assess the frequency of the alleles and genotypes of the IL-1β -31 gene polymorphism in patients exhibiting short roots with no history of orthodontic treatment.
Methods: A total of 27 subjects were categorized as exhibiting short roots (16) or normal roots (11), based upon the root morphology of incisors and mandibular premolars evident on 3D CBCT pre-treatment scans. Genomic DNA was isolated from buccal swab samples. PCR amplification of a region encompassing the -31 site was performed, followed by AluI digest. PCR products and digested fragments were separated by agarose gel electrophoresis.
Results: The fragments of 137 bp and 102 bp corresponded to -31 T and a single 239 bp fragment corresponded to -31 C. The allelic distribution showed no predominance in either short root or normal subjects. The heterozygote genotype (CT) was the most frequent, both for short root (7 of 16) and normal subjects (4 of 11); however, without statistical significance.
Conclusions: The findings from this pilot study suggest that this polymorphism is not a major factor affecting the presence of short roots. However, this may represent a false negative result due to the small sample size. Additional patient recruitment is underway to increase the sample size and power of the study.