title: Incidence of crown fracture and risk factors in the primary dentition: a prospective longitudinal study.
abstract: OBJECTIVE
  Few studies have assessed the incidence and risk factors to crown fractures in preschool children. The aim of this study was to estimate the incidence of crown fracture in the primary dentition over a 1-year follow-up period, identify risk factors, and test the hypothesis that children with previous crown fracture are more prone to experience further cases of crown fracture independently of other risk factors.
  
  
  METHODS
  This study was developed in two phases: cross-sectional and prospective longitudinal study. The cross-sectional study was carried out 261 preschool children. The prospective longitudinal study was carried out 194 children allocated to two groups: exposed group (children with prior exposure to crown fracture) and non-exposed group (children without prior exposure). On both occasions, children were examined for the diagnosis of crown fracture and evaluation of lip coverage and overjet. The parents were interviewed with regard to the socioeconomic indicators. New cases of crown fracture were identified based on the comparison of the two examinations. Data analysis involved Pearson's chi-square test, McNemar's test, and Poisson regression with robust variance.
  
  
  RESULTS
  Among the 261 children who participated in the cross-sectional study, 194 were re-examined (65 in the exposed group and 129 in the non-exposed group). The overall incidence of crown fracture was 55.7% (n = 108). The difference in percentage of increased risk of crown fracture in exposed and non-exposed groups was 13.4%. A greater incidence of crown fracture was found in the exposed group (64.6%; P < 0,001). The children exposed (RR: 1.30; 95% CI: 1.01-1.67) had a greater risk of developing new cases of crown fracture in comparison with the non-exposed group.
  
  
  CONCLUSIONS
  The incidence of crown fracture was high and children with previous crown fracture had a greater risk of suffering new cases of crown fracture during the 1-year follow-up period.
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Patrícia
authors.initials: P
authors.lastname: Corrêa-Faria
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Saul Martins
authors.initials: SM
authors.lastname: Paiva
authors.affiliation: Department of Pediatric Dentistry, Federal University of Vales do Jequitinhonha and Mucuri, Diamantina, Brazil.
authors.forename: Maria Letícia
authors.initials: ML
authors.lastname: Ramos-Jorge
authors.affiliation: Department of Pediatric Dentistry and Orthodontics, School of Dentistry, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Isabela Almeida
authors.initials: IA
authors.lastname: Pordeus
mesh_terms: D002675:Child, Preschool; D003430:Cross-Sectional Studies; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D011446:Prospective Studies; D012307:Risk Factors; D019228:Tooth Crown; D014082:Tooth Fractures; D014094:Tooth, Deciduous
keywords: incidence; primary dentition; tooth fracture