title: Mandibular tori are associated with mechanical stress and mandibular shape.
abstract: OBJECTIVE
  The influence of mechanical stimulation on the formation of torus mandibularis (TM) is still poorly understood. We sought to understand the etiology of TMs by investigating the role of parafunctional activity and mandibular morphology on the formation of TMs.
  
  
  METHODS
  We designed a case-control study for patients attending the dental clinic of the present study (University of São Paulo School of Dentistry, São Paulo, SP, Brazil). Patients presenting with TMs were defined as cases, and those without TMs were defined as controls. Finite element analysis (FEA) was used in 3-dimensional mandibular models to examine the stress distribution in the mandibles with and without TMs. In addition, the associations of mandibular arch shape, mandibular cortical index, and parafunctional activity with the presence of T were assessed using odds ratio analysis.
  
  
  RESULTS
  A total of 10 patients with TMs and 37 without TMs were selected (22 men and 25 women, mean age 54.3 ± 8.4 years). FEA showed a stress concentration in the region in which TMs form during simulation of parafunctional activity. The radiographic assessment showed that those with TMs were more likely to have a square-shaped mandible with sharp angles (P = .001) and a normal mandibular cortex (P = .03). The subjects without TMs had a round-shaped mandible with obtuse angles and an eroded mandibular cortex.
  
  
  CONCLUSIONS
  Parafunctional activity could be causing the formation of TMs by concentrating mechanical stress in the region in which TMs usually form. Thus, mandibular geometries that favor stress concentration, such as square-shaped mandibles, will be associated with a greater prevalence of TMs.
authors.affiliation: Graduate Student, Department of Stomatology, University of São Paulo School of Dentistry, São Paulo, São Paulo, Brazil.
authors.forename: Arthur Rodriguez Gonzalez
authors.initials: AR
authors.lastname: Cortes
authors.affiliation: Graduate Student, Department of Mining and Materials Engineering, McGill University, Montreal, Quebec, Canada.
authors.forename: Zhaoyu
authors.initials: Z
authors.lastname: Jin
authors.affiliation: Oral-Maxillofacial Surgery Resident, Western University Schulich School of Medicine and Dentistry, London, Ontario, Canada.
authors.forename: Matthew Daniel
authors.initials: MD
authors.lastname: Morrison
authors.affiliation: Professor, Department of Stomatology, University of São Paulo School of Dentistry, São Paulo, São Paulo, Brazil.
authors.forename: Emiko Saito
authors.initials: ES
authors.lastname: Arita
authors.affiliation: Assistant Professor, Department of Mining and Materials Engineering, McGill University, Montreal, Quebec, Canada.
authors.forename: Jun
authors.initials: J
authors.lastname: Song
authors.affiliation: Assistant Professor, McGill University Faculty of Dentistry, Montreal, Quebec, Canada. Electronic address: faleh.tamimimarino@mcgill.ca.
authors.forename: Faleh
authors.initials: F
authors.lastname: Tamimi
mesh_terms: D016022:Case-Control Studies; D005096:Exostoses / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D008334:Mandible / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology; D021362:Palate, Hard / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D011862:Radiography, Panoramic; D013314:Stress, Mechanical