title: Multifactorial etiology of Torus mandibularis: study of twins.
abstract: OBJECTIVE
  The aim of this study is to investigate the multifactorial etiology of mandibular tori analyzing the influence of genetics, occlusal overload, various clinical variables and their interactions.
  
  
  METHODS
  Overall, plaster casts of 162 twins (81 twin pairs) were analyzed for the presence or absence of mandibular tori. Atypical wear facets on canine tips or incisors were recorded to diagnose bruxism. Angle Class, any kind of anterior open bite and positive, negative or flat curve of Wilson were recorded. Zygosity determination was carried out using a DNA test.
  
  
  RESULTS
  Mandibular tori were found in 56.8% of the cases. In 93.6% of all monozygotic twin pairs both individuals had or did not have mandibular tori (κ=0.96±0.04; p<0.001), compared to 79.4% concordance of mandibular tori in dizygotic co-twins (κ=0.7±0.12; p<0.001). Prevalence of mandibular tori was significantly higher in the group of bruxers (67.5%) compared to non-bruxers (31.3%) (p<0.001). Significant association between mandibular tori and negative or flat curve of Wilson in the maxillary second premolars and first molars was found (OR=2.55, 95% CI (1.19-5.46), p=0.016). In all monozygotic bruxers, 97.1% showed concordance of mandibular tori presence in both co-twins compared to 78.9% dizygotic bruxers, and this difference is statistically significant (p=0.007).
  
  
  CONCLUSIONS
  Our results suggest that the mandibular tori are of a multifactorial origin. Mandibular tori seem to have genetic predisposition, and may be associated with teeth grinding as well as with negative or flat CW in region of maxillary second premolar and first molar.
authors.affiliation: Department of Dental and Oral Diseases, Medical Academy, Lithuanian University of Health Sciences, Eivenių str. 2, 50009 Kaunas, Lithuania. adomas.auskalnis@gmail.com.
authors.forename: Adomas
authors.initials: A
authors.lastname: Auškalnis
authors.forename: Vygandas
authors.initials: V
authors.lastname: Rutkūnas
authors.forename: Olaf
authors.initials: O
authors.lastname: Bernhardt
authors.forename: Mantas
authors.initials: M
authors.lastname: Šidlauskas
authors.forename: Loreta
authors.initials: L
authors.lastname: Šalomskienė
authors.forename: Nomeda
authors.initials: N
authors.lastname: Basevičienė
mesh_terms: D001641:Bicuspid; D002012:Bruxism; D004200:Diseases in Twins / Q000453:epidemiology; D006801:Humans; D008336:Mandibular Diseases / Q000235:genetics*; D015995:Prevalence; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic