title: Effect of application time of maleic acid on smear layer removal and mechanical properties of root canal dentin.
abstract: OBJECTIVE
  To evaluate the effect of maleic acid (MA) on the cleaning efficacy and mechanical properties of root canal dentine with respect to different time exposure.
  
  
  METHODS
  One hundred and eighty single-canal premolars were instrumented with rotary-files and then randomly assigned to test groups receiving 7% MA for 30 s, 45 s, 1 min, or 3 min or to control groups treated with 0.9% saline or 17% ethylenediaminetetraacetic acid for 45 s. The micro-hardness, nano-hardness and elastic modules were measured before and after treatment, while the amount of smear and erosion in the coronal, middle and apical thirds in root canal were evaluated by scanning electron microscopy, finally, the fracture strength was assessed by vertical root fracture testing.
  
  
  RESULTS
  The efficacy of smear layer removal increased with increasing MA application time. The largest effect was observed at 45 s, even in the apical third, whereas the treatment for 1 min resulted in irreversible erosion of the dentine surface. The micro-hardness and nano-indentation testing confirmed that the micro- and nano-scale mechanical properties were significantly decreased after MA application for 1 min. Furthermore, the specimens treated with MA for 3 min presented the lowest fracture resistance among all groups. In contrast, the 45 s treatment appeared to increase the fracture resistance of the tooth.
  
  
  CONCLUSIONS
  The cleaning efficacy and mechanical properties of root canal dentine varied with MA exposure time. The application of MA for 45 s was found to be the most promising for clinical use.
authors: a Department of Endodontics , School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Lin
authors: L
authors: Wang
authors: a Department of Endodontics , School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Yu
authors: Y
authors: Zhao
authors: b Department of Pediatric Dentistry , School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Liqin
authors: L
authors: Mei
authors: c State Key Laboratory of Oral Diseases , West China Hospital of Stomatology, Sichuan University , Chengdu , PR China.
authors: Haiyang
authors: H
authors: Yu
authors: d Institute of Stomatology, School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Ibrahim
authors: I
authors: Muhammad
authors: a Department of Endodontics , School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Yihuai
authors: Y
authors: Pan
authors: d Institute of Stomatology, School and Hospital of Stomatology, Wenzhou Medical University , Wenzhou , PR China.
authors: Shengbin
authors: S
authors: Huang
mesh_terms: D001641:Bicuspid / Q000187:drug effects; D003786:Dental Pulp Cavity / Q000187:drug effects*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000187:drug effects*; D004492:Edetic Acid / Q000627:therapeutic use; D055119:Elastic Modulus; D006244:Hardness; D006801:Humans; D008298:Maleates / Q000627:therapeutic use*; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D012388:Root Canal Irrigants / Q000627:therapeutic use*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods; D016369:Smear Layer / Q000517:prevention & control*; D013314:Stress, Mechanical; D013997:Time Factors; D019227:Tooth Apex / Q000187:drug effects
chemical_list: D008298:Maleates; D012388:Root Canal Irrigants; C030272:maleic acid; D004492:Edetic Acid
keywords: Irrigations solution; fracture resistance; micro-hardness; nano-indentation; smear layer