title: Direct restoration modalities of fractured central maxillary incisors: A multi-levels validated finite elements analysis with in vivo strain measurements.
abstract: OBJECTIVE
  To quantify the influence of fracture geometry and restorative materials rigidity on the stress intensity and distribution of restored fractured central maxillary incisors (CMI) with particular investigation of the adhesive interfaces. Ancillary objectives are to present an innovative technology to measure the in vivo strain state of sound maxillary incisors and to present the collected data.
  
  
  METHODS
  A validation experimental biomechanics approach has been associated to finite element analysis. FEA models consisted of CMI, periodontal ligament and the corresponding alveolar bone process. Three models were created representing different orientation of the fracture planes. Three different angulations of the fracture plane in buccal-palatal direction were modeled: the fracture plane perpendicular to the long axis in the buccal-palatal direction (0°); the fracture plane inclined bucco-palatally in apical-coronal direction (-30°); the fracture plane inclined palatal-buccally in apical-coronal direction (+30°). First set of computing runs was performed for in vivo FE-model validation purposes. In the second part, a 50N force was applied on the buccal aspect of the CMI models. Ten patients were selected and subjected to the strain measurement of CMI under controlled loading conditions.
  
  
  RESULTS
  The main differences were noticed in the middle and incisal thirds of incisors crowns, due to the presence of the incisal portion restoration. The stress intensity in -30° models is increased in the enamel structure close to the restoration, due to a thinning of the remaining natural tissues. The rigidity of the restoring material slightly reduces such phenomenon. -30° model exhibits the higher interfacial stress in the adhesive layer with respect to +30° and 0° models. The lower stress intensity was noticed in the 0° models, restoration material rigidity did not influenced the interfacial stress state in 0° models. On the contrary, material rigidity influenced the interfacial stress state in +30° and -30° models, higher rigidity restoring materials exhibits lower interfacial stress with respect to low rigidity materials.
  
  
  CONCLUSIONS
  Fracture planes inclined palatal-buccally in apical-coronal direction (+30°) reduce the interfacial stress intensity and natural tissues stress intensity with respect to the other tested configurations.
authors.affiliation: Calabrodental Clinic, Tecnologica Research Institute, Crotone, Italy.
authors.forename: Apicella
authors.initials: A
authors.lastname: Davide
authors.affiliation: Advanced Materials Lab, Department of Architecture and Industrial Design, Second University of Naples, Naples, Italy.
authors.forename: Aversa
authors.initials: A
authors.lastname: Raffaella
authors.affiliation: Calabrodental Clinic, Tecnologica Research Institute, Crotone, Italy.
authors.forename: Tatullo
authors.initials: T
authors.lastname: Marco
authors.affiliation: Department of Oral Sciences, University "Federico II", Naples, Italy.
authors.forename: Simeone
authors.initials: S
authors.lastname: Michele
authors.affiliation: Oral Basic and Clinical Sciences, Faculty of Dentistry, King Abdul Aziz University, Jeddah, Saudi Arabia.
authors.forename: Jamaluddin
authors.initials: J
authors.lastname: Syed
authors.affiliation: Calabrodental Clinic, Tecnologica Research Institute, Crotone, Italy.
authors.forename: Marrelli
authors.initials: M
authors.lastname: Massimo
authors.affiliation: Tuscan School of Dental Medicine, University of Florence and Siena, Siena, Italy.
authors.forename: Ferrari
authors.initials: F
authors.lastname: Marco
authors.affiliation: Advanced Materials Lab, Department of Architecture and Industrial Design, Second University of Naples, Naples, Italy. Electronic address: antonio.apicella@unina2.it.
authors.forename: Apicella
authors.initials: A
authors.lastname: Antonio
mesh_terms: D000293:Adolescent; D000328:Adult; D017076:Computer-Aided Design; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D007180:Incisor / Q000293:injuries*; D008297:Male; D008437:Maxilla; D013718:Tensile Strength; D014082:Tooth Fractures / Q000628:therapy*
keywords: Biomechanic; FEA; Fracture; In vivo; Incisor; Restoration; Strain; Strain gauge