An in vitro investigation of the effect of bevel design on the penetration and withdrawal forces of dental needles

Objectives pare the effect on insertion and withdrawal forces using needles with a standard atraumatic bevel to those with a novel asymmetrical bevel in vitro. s m needle penetration forces were measured using a 10 N load cell mounted on an Instron universal testing machine. Forces were determined during insertion through a 0.4 mm polyurethane membrane mounted at 90° (n = 30 of each design), 30° (n = 16 of each design) and 150° (n = 16 of each design) to the needle bevel and during a 10 mm insertion into a polyvinyl siloxane block mounted at 90° to the bevel (n = 16 of each design). In all tests the rate of insertion was 50 mm/min. s vel design required less force to penetrate the membrane at 30° and 150° compared to the standard design (mean forces at 30° being 0.75 N and 0.98 N for novel and standard designs respectively [p < 0.001] and at 150° 0.52 N and 0.66 N respectively [p < 0.001] but more force at 90° penetration tests (0.60 N and 0.46 N respectively [p < 0.001]). The novel design required less force to insert 10 mm into the polyvinyl siloxane (1.80 N and 2.54 N respectively [p < 0.001]). sion vel design needed less force than the standard version to penetrate a thin membrane when used at 30° and 150° to the surface and to penetrate a polyvinyl siloxane block to a depth of 10 mm but required more force to penetrate a thin membrane at 90°. al significance bevel design affects the penetration and withdrawal forces of dental needles in vitro.