title: [Effect of different orthodontic interproximal reduction methods on the enamel].
abstract: OBJECTIVE
  To find a suitable interproximal enamel (IER) reduction method for clinical use by pH cycles in vitro.
  
  
  METHODS
  50 human premolars extracted for orthodontic reasons were collected for the experiment. After removal of the roots, the crowns were split vertically into two halves with wafer-thin wheel blade. Then the 100 samples were randomly divided into 5 groups, 20 samples for each group. The enamel in each group was reduced with different IER methods: group I, stripping strip; group II, stripping disk; group III, stripping strip with polishing system and 35% orthophosphoric acid; group IV, stripping disk with polishing system and 35% orthophosphoric acid; group V, no treatment control group. All the samples were treated with pH cycles in vitro for 30 days. The microhardness of enamel surface of all samples was detected by microhardness testing machine. The enamel surface morphology of microstructure was examined by scanning electron microscopy(SEM).The data was analyzed with SPSS13.0 software package.
  
  
  RESULTS
  1.ANOVA detected statistically significant differences between groups. The post SNK-q test showed that there was no significant difference between group I and group II, between group III and group IV(P>0.05); But there was significant difference between group I and group III, group I and group IV, group II and group III, group II and group IV(P<0.01). And there was significant difference between group I and group V, group II and group V, group III and group V, group IV and group V(P<0.05). 2.From naked eye and SEM, there was no distinct difference between the two chemical polishing groups, but better than the others.
  
  
  CONCLUSIONS
  1.There is no significant difference between strip and disk after IER. 2.Chemical polishing group is better than the others after IER. 3.The scratches of the enamel surface caused by IER are hardly repaired even after remineralization.
authors.affiliation: Department of Stomatology, No.401 Hospital of PLA, Qingdao 266071, Shandong Province, China. 33647904@qq.com
authors.forename: Chuan-liang
authors.initials: CL
authors.lastname: Shu
authors.forename: Xin-qiang
authors.initials: XQ
authors.lastname: Liu
authors.forename: Gui-feng
authors.initials: GF
authors.lastname: Wang
mesh_terms: D001641:Bicuspid; D003743:Dental Enamel; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010756:Phosphoric Acids
chemical_list: D010756:Phosphoric Acids; C030242:phosphoric acid