title: Overlays or ceramic fragments for tooth restoration: an analysis of fracture resistance.
abstract: OBJECTIVE
  The aim of this study was to evaluate the mode of fracture and resistance of partial ceramic restorations of posterior teeth.
  
  
  METHODS
  Thirty healthy upper premolars were selected and divided into three groups (n = 10): Group 1- control, healthy unrestored teeth, group 2-teeth restored with ceramic fragments; and group 3-teeth restored with ceramic overlays. The restorations were manufactured with feldspathic ceramic and cemented with RelyX ARC resin cement. After being stored in distilled water for 7 days, the teeth were subjected to axial compression mechanical testing with a universal testing machine. Force was applied to the long axis of the tooth at a speed of 0.5 mm/min until fracture. The data were analyzed with one-way ANOVA and Tukey's test (5%). The mode of fracture was scored according to the degree of involvement of the tooth structure and the type of restoration.
  
  
  RESULTS
  A significant difference (p < 0.05) was showed between groups 2 (1155 N) and 3 (846.6 N), but there was no significant difference between group 1 and the other groups (1046 N), More extensive fractures were prevalent in the healthy teeth group (Group 1), which had no occlusal coverage; less severe fractures were found in groups 2 and 3.
  
  
  CONCLUSIONS
  We conclude that teeth restored with ceramic fragments may offer greater resistance to fractures compared to teeth that have overlay restorations.
authors.affiliation: Professor, Department of Post-Graduation in Dentistry, CEUMA University, São Luis, Maranhao, Brazil.
authors.forename: Rudys Rodolfo de Jesus
authors.initials: RR
authors.lastname: Tavarez
authors.affiliation: Professor, Department of Post-Graduation in Dentistry, CEUMA University, São Luis, Maranhao, Brazil.
authors.forename: Leily Macedo
authors.initials: LM
authors.lastname: Firoozmand
authors.affiliation: Dental Student, Department of Prosthodontics, CEUMA University, São Luis Brazil.
authors.forename: Mônica Barros
authors.initials: MB
authors.lastname: Silva
authors.affiliation: Professor, Department of Prosthodontics, CEUMA University, São Luis Maranhao, Brazil.
authors.forename: Adriana Santos
authors.initials: AS
authors.lastname: Malheiros
authors.affiliation: Professor, Department of Post-Graduation in Dentistry, CEUMA University, São Luis, Maranhao, Brazil.
authors.forename: Matheus Coelho
authors.initials: MC
authors.lastname: Bandéca
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D001641:Bicuspid / Q000503:physiopathology; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D019245:Compressive Strength; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D007284:Inlays; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014082:Tooth Fractures / Q000503:physiopathology; D014867:Water / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D011109:Polymethacrylic Acids; D017680:Potassium Compounds; C462240:RelyX ARC; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D014867:Water; D003776:Dental Porcelain; C016447:feldspar; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D006858:Hydrofluoric Acid