title: An in vitro investigation of the effect of bevel design on the penetration and withdrawal forces of dental needles.
abstract: OBJECTIVE
  To compare the effect on insertion and withdrawal forces using needles with a standard atraumatic bevel to those with a novel asymmetrical bevel in vitro.
  
  
  METHODS
  Maximum needle penetration forces were measured using a 10N load cell mounted on an Instron universal testing machine. Forces were determined during insertion through a 0.4mm 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 10mm 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 50mm/min.
  
  
  RESULTS
  The novel design required less force to penetrate the membrane at 30° and 150° compared to the standard design (mean forces at 30° being 0.75N and 0.98N for novel and standard designs respectively [p<0.001] and at 150° 0.52N and 0.66N respectively [p<0.001] but more force at 90° penetration tests (0.60N and 0.46N respectively [p<0.001]). The novel design required less force to insert 10mm into the polyvinyl siloxane (1.80N and 2.54N respectively [p<0.001]).
  
  
  CONCLUSIONS
  The novel 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 10mm but required more force to penetrate a thin membrane at 90°.
  
  
  CONCLUSIONS
  Needle bevel design affects the penetration and withdrawal forces of dental needles in vitro.
authors.affiliation: Centre for Oral Health Research, School of Dental Sciences, Newcastle University, Framlington Place, Newcastle Upon Tyne NE 2 4BW, UK. andrewsteele74@hotmail.com
authors.forename: A C
authors.initials: AC
authors.lastname: Steele
authors.forename: M J
authors.initials: MJ
authors.lastname: German
authors.forename: J
authors.initials: J
authors.lastname: Haas
authors.forename: G
authors.initials: G
authors.lastname: Lambert
authors.forename: J G
authors.initials: JG
authors.lastname: Meechan
mesh_terms: D000766:Anesthesia, Dental / Q000295:instrumentation*; D000772:Anesthesia, Local / Q000295:instrumentation*; D003799:Dental Stress Analysis / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D007267:Injections / Q000295:instrumentation*; D008422:Materials Testing; D008567:Membranes, Artificial; D009339:Needles; D011140:Polyurethanes / Q000737:chemistry; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D008567:Membranes, Artificial; D011140:Polyurethanes; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane