title: The effect of residual calcium hydroxide on the accuracy of a contemporary electronic apex locator.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effect of residual calcium hydroxide [Ca(OH)2] on the accuracy of an electronic apex locator (EAL).
  
  
  METHODS
  Working lengths (WLs) of 56 extracted maxillary incisors were determined initially by two different methods. The first method used the 'APEX' reading of the EAL as a reference point, 0.5 mm was subtracted and recorded as WL0. The second method used the '0.5' reading and the score was recorded as WL0.5 without subtraction. The roots were prepared to WL0 and divided randomly into three experimental groups (n = 16) (1 mm in group A, 2 mm in group B and 4 mm in group C) and a control (n = 8). Specimens in all experimental groups were filled with Ca(OH)2 paste. Following its removal, WLs were re-determined with the same methods.
  
  
  RESULTS
  In group C, pre/post WLs were significantly different (p < 0.05). No significant difference was observed between the other experimental groups and the control group.
  
  
  CONCLUSIONS
  Accuracy of EAL decreased proportionally with the amount of paste remaining at the ±0.5-mm tolerance level. Ca(OH)2 paste remnants may cause incorrect EAL readings.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Erciyes University , Kayseri , Turkey.
authors.forename: Yakup
authors.initials: Y
authors.lastname: Ustun
authors.forename: Ozgur
authors.initials: O
authors.lastname: Uzun
authors.forename: Ozgur
authors.initials: O
authors.lastname: Er
authors.forename: Burhan Can
authors.initials: BC
authors.lastname: Canakcı
authors.forename: Ozgur
authors.initials: O
authors.lastname: Topuz
mesh_terms: D002126:Calcium Hydroxide / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D055615:Electrical Equipment and Supplies / Q000706:statistics & numerical data*; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology; D008422:Materials Testing; D009811:Odontometry / Q000295:instrumentation* / Q000706:statistics & numerical data; D011897:Random Allocation; D012388:Root Canal Irrigants / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D019227:Tooth Apex / Q000033:anatomy & histology*
chemical_list: D012388:Root Canal Irrigants; D002126:Calcium Hydroxide
keywords: apex locator accuracy; calcium hydroxide; endodontics