title: Root curvature: differences among dental morphotypes and modifications after mechanical instrumentation.
abstract: BACKGROUND
  This study was designed to describe a method for measuring root curvature of extracted teeth, compare root curvature of four different dental morphotypes before mechanical instrumentation, and measure root curvature after mechanical instrumentation.
  
  
  METHODS
  Fifty-five maxillary (14 central incisors, 13 lateral incisors, 14 cuspids, 14 premolars) extracted teeth were analyzed. Measurements were recorded on the horizontal plane at the most apical point of the cemento-enamel junction (CEJ). A 4 mm wide root portion on the buccal aspect was selected and recorded on this plane. A digital scanner traced the circle coinciding with the profile of this root portion and calculated its radius, arc, chord, and arrow (i.e., the perpendicular bisector of the chord). Since root curvature is the inverse of the radius (1/r), the radius was related to root curvature; the arc to the mesio-distal dimension of the root portion; and the reduction of the arrow to root flattening after mechanical instrumentation. The measurements were recorded four times: before treatment (baseline), after polishing, after a first root planing, and after a second root planing. The radii of each dental morphotype (upper central incisors, upper lateral incisors, upper canines, upper premolars) recorded in the first measurement were calculated and used for the statistical analyses: one-way analysis of variance (ANOVA) test and the Tukey multiple comparison method were used to study the curvature. The measurements of the radius, the arc, and the arrow at the four times were used for the statistical analyses: the two-way ANOVA test and the Tukey multiple comparison method were applied in the study of the root modifications after mechanical instrumentation. The accuracy and reliability of the method were also evaluated.
  
  
  RESULTS
  The mean radii of the four dental morphotypes were: central incisors: 3.613 +/- 0.258 mm; lateral incisors: 2.558 +/- 0.256 mm; canines: 2.822 +/- 0.238 mm; and premolars: 2.321 +/- 0.179 mm. The statistical analyses revealed differences among central incisors, canines, lateral incisors, and premolars. There was no statistically significant difference between lateral incisors and premolars. Regarding the root modifications after mechanical treatment, the radius did not show statistically significant differences in any of the comparisons. The arc and the arrow did not show significant differences between baseline and polishing, while they did show significant differences after the second root planing.
  
  
  CONCLUSIONS
  This study indicates that: 1) the method of measuring is accurate and reliable; 2) there are statistically significant differences among the root curvatures of different dental morphotypes; and 3) polishing did not modify the root. A vigorous root planing did not modify root curvature, but it did reduce the mesio-distal dimension and flatten the root surface slightly.
authors.affiliation: Private practice, Florence, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Saletta
authors.forename: Carlo
authors.initials: C
authors.lastname: Baldi
authors.forename: Michele
authors.initials: M
authors.lastname: Nieri
authors.forename: Paolo
authors.initials: P
authors.lastname: Ceppatelli
authors.forename: Debora
authors.initials: D
authors.lastname: Franceschi
authors.forename: Roberto
authors.initials: R
authors.lastname: Rotundo
authors.forename: Francesco
authors.initials: F
authors.lastname: Cairo
authors.forename: Giovan Paolo
authors.initials: GP
authors.lastname: Pini Prato
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid / Q000033:anatomy & histology*; D003481:Cuspid / Q000033:anatomy & histology*; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D016745:Root Planing / Q000009:adverse effects; D019237:Tooth Cervix / Q000033:anatomy & histology*; D014092:Tooth Root / Q000033:anatomy & histology*