Association of the <scp>SCN9A</scp> rs6746030 ( <scp>R1150W</scp> ) Polymorphism on Inferior Alveolar Nerve Block Failure in Symptomatic Irreversible Pulpitis

INTRODUCTION: This study evaluated whether the SCN9A rs6746030 (G>A; R1150W) polymorphism is associated with the clinical success or failure of pulpal anaesthesia following an inferior alveolar nerve block (IANB). METHODS: In this prospective clinical genetic association study, 320 patients with symptomatic irreversible pulpitis in mandibular molars were recruited. Each patient received a standardized IANB with 2% lidocaine and 1:80000 epinephrine. Anaesthesia was considered successful if the Heft-Parker Visual Analogue Scale (HP-VAS) score was below 54 mm during access cavity preparation/instrumentation; scores of 54 mm or higher were classified as failures. Buccal swab samples were collected for genotyping of rs6746030 using a TaqMan SNP assay. Genotype distributions were compared between the success and failure groups. Statistical analysis included Hardy-Weinberg equilibrium testing, chi-square comparisons, and binary logistic regression with genotype, age and gender as predictors. RESULTS: Out of 320 patients analysed, 199 experienced failed anaesthesia, while 121 achieved successful outcomes. A significant deviation from Hardy-Weinberg equilibrium was found in the failed anaesthesia group (p < 0.05), suggesting potential genetic influence, while the successful group showed no deviation (p = 0.99). Logistic regression revealed that patients with the AA genotype had significantly lower odds of successful anaesthesia (OR = 0.22; 95% CI: 0.049-0.993). No significant associations were observed for the GA genotype, age, or gender. The model's predictive ability was limited, with an AUC of 0.53. CONCLUSION: The rs6746030 polymorphism of SCN9A in its AA form is associated with a higher likelihood of IANB failure in mandibular molars with symptomatic irreversible pulpitis.