Abstract
Dental injection needle integrity may influence tissue trauma during local anesthesia. This study compared needle-tip microstructural deformation after different local anesthesia techniques using field emission scanning electron microscopy (FESEM). A total of 110 single-use needles were allocated to an unused descriptive control set (n = 5), infiltrative local anesthesia (ILA; n = 35), direct inferior alveolar nerve block anesthesia (DIANBA; n = 35), and indirect inferior alveolar nerve block anesthesia (IIANBA; n = 35). After one clinical application, tips were evaluated for bevel edge irregularity (BEI), tip axis deviation (TAD), and bevel edge microstructural breakdown (BEMB). Inferential analyses were restricted to the three equally sized clinical groups. BEI occurred in 5.7%, 28.6%, and 45.7% of the ILA, DIANBA, and IIANBA groups, respectively (overall p = 0.0007; Cramer’s V = 0.371). After Holm adjustment, BEI differed between ILA and DIANBA (adjusted p = 0.0469) and between ILA and IIANBA (adjusted p = 0.0007). TAD frequencies were 14.3%, 34.3%, and 40.0% (overall p = 0.0466; V = 0.242), but no pairwise comparison remained significant after adjustment. BEMB frequencies were 22.9%, 40.0%, and 45.7%, with no statistically significant overall difference (p = 0.117). Thus, the demonstrated finding is greater needle-tip microstructural deformation, particularly BEI, after nerve block techniques; clinical consequences such as pain or tissue trauma were not assessed and require dedicated investigation.