Scanning Electron Microscopic Evaluation of Bevel Deformation in Dental Needles After Repeated Anesthetic Insertions

Aim To evaluate the occurrence, magnitude, and pattern of dental needle bevel deformation before and after clinical use, comparing unused needles with needles subjected to different numbers of anesthetic insertions. Materials and Methods This cross-sectional analytical study evaluated bevel deformation in 40 long stainless-steel dental needles (27G), allocated into four groups according to the number of anesthetic insertions: unused, single use, two uses, and four uses. Bevel morphology was analyzed using scanning electron microscopy, and deformation angles were measured. Results Bevel deformation was observed in all groups, including unused needles, with critical defects predominating after one and two uses, while needles subjected to four uses showed only non-critical deformation. Comparisons using raw angles revealed significant differences between the control group and the one- and two-use groups ( p < 0.05), whereas cluster analysis demonstrated a distinct deformation pattern in the four-use group compared with the other experimental groups ( p < 0.05). Conclusion Dental needle bevel deformation may be present even before clinical use, suggesting pre-existing micromorphological irregularities related to manufacturing processes. Clinically relevant deformation was already observed after a single anesthetic insertion. Repeated needle use resulted in a distinct pattern characterized by cumulative, non-critical bevel deformation.