title: The post-traumatic colour change of primary incisors: a colourimetric and longitudinal study.
abstract: BACKGROUND
  Tooth colour change after trauma has been described subjectively as ranging from yellow/pink to grey/black.
  
  
  OBJECTIVE
  To investigate the longitudinal colourimetric change of post-traumatic discoloured primary incisor using an intraoral colourimeter.
  
  
  METHODS
  A total of 34 primary incisors from 15 boys and eight girls were studied. The mean post-injury day during clinic visits (SD) and number of visit was 205.4 (194.8) and 3.9 (2.0). CIE L* (lightness), a* (green-red) and b* (blue-yellow) of the maxillary primary incisors were measured at every visit. The colour difference (ΔE*ab ) was calculated between the traumatized tooth and the control. Scatter graphs were made depicting the colour change of discoloured teeth and the ΔE*ab over time.
  
  
  RESULTS
  Mean CIE L*, a* and b* of the unaffected control were 80.8 (2.29), 0.9 (0.77) and 13.1 (2.67), respectively. L* gradually decreased to 70.7 (on day 71), then slowly recovered. a* increased to 3.7 (day 29) and decreased slowly. b* only demonstrated a small change that was within the control range during the follow-up. ΔE*ab increased to 9.58 (day 56) and decreased slowly.
  
  
  CONCLUSIONS
  The earlier recovery of a* was followed by the recovery of L*. During the post-traumatic period, ΔE*ab failed to reach the clinically acceptable threshold.
authors.affiliation: Department of Paediatric Dentistry, School of Dentistry, Dental Research Institute, Seoul National University, Seoul National University Dental Hospital, Seoul, Korea.
authors.forename: Hong-Keun
authors.initials: HK
authors.lastname: Hyun
authors.affiliation: Department of Paediatric Dentistry, School of Dentistry, Dental Research Institute, Seoul National University, Seoul National University Dental Hospital, Seoul, Korea.
authors.forename: Teo Jeon
authors.initials: TJ
authors.lastname: Shin
authors.affiliation: Department of Paediatric Dentistry, School of Dentistry, Dental Research Institute, Seoul National University, Seoul National University Dental Hospital, Seoul, Korea.
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003124:Colorimetry / Q000379:methods*; D005260:Female; D006801:Humans; D007180:Incisor / Q000293:injuries*; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D008437:Maxilla; D010865:Pilot Projects; D013997:Time Factors; D014075:Tooth Discoloration / Q000209:etiology*; D014094:Tooth, Deciduous / Q000293:injuries*; D014947:Wounds and Injuries / Q000150:complications*