title: Niobium pentoxide as a new filler for methacrylate-based root canal sealers.
abstract: OBJECTIVE
  To evaluate the influence of several niobium pentoxide (Nb(2) O(5) ) concentrations on the radio-opacity, flow, film thickness, microhardness and degree of conversion of an experimental root canal sealer.
  
  
  METHODS
  An experimental dual-cured root canal sealer was produced with a methacrylate-based comonomer blend. Nb(2) O(5) was added at four different concentrations: 0, 80, 100 and 120 wt%. Radio-opacity was evaluated according to ISO 6876 using a digital system (n = 5). Flow and film thickness were determined in accordance with ISO 6876 (n = 3). Microhardness was evaluated with 50 g for 15 s (n = 5). Degree of conversion was evaluated with FTIR immediately after photocuring and after 1, 7 and 14 days. The data were analysed using anova and Tukey's test. The degree of conversion over time was evaluated using RM-anova (α = 0.05).
  
  
  RESULTS
  The groups with 80 wt% and 100 wt% of filler showed no significant difference in radio-opacity from that of equivalent 2 mmAl (P > 0.05). The addition of 120 wt% resulted in radio-opacity values higher than 2 mmAl (P < 0.05). The flow was not significantly different amongst the different groups (P > 0.05). All groups had a film thickness of <50 μm (ISO 6876). All groups with Nb(2) O(5) were associated with higher values of microhardness than the control group. The group with 0 wt% was associated with a higher degree of conversion at all times. All groups except those with 80 wt% had higher values for degree of conversion after 14 days than immediately after photocuring.
  
  
  CONCLUSIONS
  The addition of Nb(2) O(5) increases radio-opacity and microhardness; this material may be a promising filler for the production of a new endodontic sealer.
authors.affiliation: Dental Materials Laboratory, School of Dentistry, Porto Alegre, RS, Brazil. vicente.leitune@ufrgs.br
authors.forename: V C B
authors.initials: VC
authors.lastname: Leitune
authors.forename: A
authors.initials: A
authors.lastname: Takimi
authors.forename: F M
authors.initials: FM
authors.lastname: Collares
authors.forename: P D
authors.initials: PD
authors.lastname: Santos
authors.forename: C
authors.initials: C
authors.lastname: Provenzi
authors.forename: C P
authors.initials: CP
authors.lastname: Bergmann
authors.forename: S M W
authors.initials: SM
authors.lastname: Samuel
mesh_terms: D002164:Camphor / Q000031:analogs & derivatives / Q000737:chemistry; D003287:Contrast Media / Q000737:chemistry; D006244:Hardness; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D058567:Photoinitiators, Dental / Q000737:chemistry; D058105:Polymerization; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012212:Rheology; D012387:Root Canal Filling Materials / Q000737:chemistry*; D055116:Self-Curing of Dental Resins; D012821:Silanes / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013997:Time Factors; D014783:Viscosity
chemical_list: D003287:Contrast Media; D008689:Methacrylates; D010087:Oxides; D058567:Photoinitiators, Dental; D011140:Polyurethanes; D019279:Resin Cements; D012387:Root Canal Filling Materials; D012821:Silanes; D009556:Niobium; C029824:urethane dimethacrylate luting resin; C017492:methacryloxypropyltrimethoxysilane; C074277:ethoxylated bis-phenol A dimethacrylate; D002164:Camphor; C073337:niobium pentoxide; C553149:camphorquinone