title: Effect of tooth brush abrasion and thermo-mechanical loading on direct and indirect veneer restorations.
abstract: OBJECTIVE
  This study investigated toothbrush abrasion and in vitro aging on ceramic (indirect technique) and composite veneers (direct technique).
  
  
  METHODS
  Identical composite and individual human incisors were restored with industrially preformed composite veneers, indirectly produced ceramic veneers, and direct composite restorations. Surface roughness was determined before and after tooth brushing. A 5-year period of oral service was simulated by thermal cycling and mechanical loading (TCML). After TCML, all specimens were examined with microscopy and scanning electron microscopy. Specimens without failures during TCML were loaded until failure.
  
  
  METHODS
  analysis of variance; Bonferroni's post hoc analysis, Kaplan-Meier-Log Rank test (α = 0.05).
  
  
  RESULTS
  Tooth brushing yielded a non-significant increase (p = 0.560) in roughness in all materials (industrial veneer, 0.12+/-0.07 μm, direct restoration, 0.18+/-0.14 μm, ceramic, 0.35+/-0.16 μm). No significant differences in roughness could be determined between the materials, neither before nor after testing (p < 0.001). After TCML of artificial teeth, direct and preformed composite veneers on composite teeth showed no failures or damages. Two ceramic veneers showed cracking in the labial area. After TCML of human teeth, transmission microscopy indicated a facial crack in a ceramic veneer and chipping in the cervical area of a preformed veneer. Two direct composite veneers lost retention. No significantly different survival rates were found between the three veneer groups. Fracture force on human teeth varied between 527.8+/-132.4 N (ceramic), 478.3+/-165.4 N (preformed composite), and 605.0+/-263.5 N (direct composite).
  
  
  CONCLUSIONS
  All materials revealed comparable wear resistance. Indirect ceramic, direct restorative composite, and preformed composite veneers showed comparable failure rates and satisfying longevity.
  
  
  CONCLUSIONS
  The results indicate similar longevity of the chosen materials for veneer restorations.
authors.affiliation: Department of Prosthetic Dentistry, University Medical Center Regensburg, 93042, Regensburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
authors.forename: Alexander
authors.initials: A
authors.lastname: Sawaljanow
authors.forename: Michael
authors.initials: M
authors.lastname: Behr
authors.forename: Carola
authors.initials: C
authors.lastname: Kolbeck
authors.forename: Verena
authors.initials: V
authors.lastname: Preis
mesh_terms: D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D019232:Dental Restoration Failure; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D066298:In Vitro Techniques; D007180:Incisor; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D013499:Surface Properties; D014072:Tooth Abrasion / Q000209:etiology* / Q000628:therapy*; D014099:Toothbrushing / Q000009:adverse effects*
chemical_list: D003188:Composite Resins