Detection of microRNAs associated with bone remodeling during laser-accelerated orthodontic tooth movement in saliva – A pilot study

Objectives: Low-level laser therapy (LLLT) is a non-invasive adjunctive procedure that, when used along with orthodontic force, can accelerate tooth movement through its photo-biomodulation effect on the cells involved in alveolar bone remodeling. Laser photons are absorbed by the mitochondrial respiratory chain enzymes cytochrome c oxidase, which causes an increase in adenosine triphosphate (ATP) production and subsequently upregulates various transcription and post-transcription factors involved in the process of orthodontic tooth movement (OTM). MicroRNAs ( miRNA ) are excellent biomarkers for tracking the activities of the cells involved in this process . The aim of the present study is to assess the amplification of miRNA genes in salivary samples of patients undergoing orthodontic treatment along with LLLT using polymerase chain reaction (PCR). Material and Methods: In patients undergoing orthodontic treatment involving premolars extraction, laser irradiation was performed in conjugation with force application on the 1 st , 3 rd , 7 th , and 14 th day after activation ( L1, L2, L3 , and L4 ). Saliva samples were collected during these corresponding timelines, and an additional sample was collected 2 weeks post-L4 ( L5 ). Monthly measurements of tooth movement in the maxillary arch were obtained from patient casts using a digital caliper by measuring the distance between the canine cusp tip and the mesiobuccal cusp tip of the first molar. RNA was extracted from the salivary sample using TriZol reagent method. The quantity and quality of RNA were determined using a bio-spectrophotometer and formaldehyde gel electrophoresis. Complementary DNA (cDNA) synthesis was carried out using the PrimeScript synthesis kit. miRNA gene was amplified using the PCR method and the product was analyzed using agarose gel electrophoresis. Results: In the present study, models for OTM demonstrated an average monthly rate of space closure of 1.28 mm and 1.33 mm on the right and left side, respectively. The RNA quantification yielded an average concentration of >200 ng/uL with prominent bands corresponding to the 18s and 28s RNAs. PCR amplification of miRNA genes has revealed the desired product size. Conclusion: LLLT plays an effective role in enhancing tooth movement in orthodontic patients. PCR amplification of miRNA genes supports the molecular insights into the treatment process. The combination of laser therapy and molecular analysis provides valuable clues for improving orthodontic treatment strategies.