Association of the Interleukin-1β (-511) Gene Polymorphism With Short Tooth Roots

Objectives: The bone resorptive cytokine IL-1β has been implicated as a key component of the complex pathways leading to tooth root resorption. The single-nucleotide polymorphism in the IL-1β gene promoter at -511 has been reported to alter the amount of IL-1β production. A model is proposed where alterations in the level of IL-1β expression may result in an individual’s predisposition to root resorption during orthodontic treatment. Without potential 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 -511 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 obtained from buccal swab samples. PCR amplification of a region encompassing the -511 site was performed, followed by AvaI digest. PCR products and digested fragments were separated by agarose gel electrophoresis.
Results: The fragments of 92 bp and 63 bp corresponded to -511 C and a single 155 bp fragment corresponded to -511 T. 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: This pilot study suggests that the IL-1B -511 polymorphism may not be a factor affecting the presence of short roots. Alternatively, 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.