title: Dicalcium phosphate (CaHPO4·2H2O) precipitation through ortho- or meta-phosphoric acid-etching: effects on the durability and nanoleakage/ultra-morphology of resin-dentine interfaces.
abstract: OBJECTIVE
  To compare the effects of two etching procedures using meta-phosphoric (MPA) or ortho-phosphoric acid (OPA) on dentine demineralisation, resin-dentine bonds durability and interface nanoleakage/ultra-morphology.
  
  
  METHODS
  Middle-dentine specimens were etched using 37% OPA (15s) or 40% MPA (60s) and submitted to infrared spectroscopy (FTIR) or ultra-morphology dye-assisted (calcium-staining) confocal microscopy (Ca-CLSM). A three-step etch-and-rinse adhesive was formulated, applied onto dentine and light-cured for 30s before composite build-up. After 24h, the dentine-bonded specimens were cut into 1mm(2) beams; half were immediately submitted to microtensile bond strength (μTBS) and half stored in DW for six months. The μTBS results were analysed with repeated-measures ANOVA and Tukey's test (p<0.05). Further teeth were bonded and prepared for interface nanoleakage/ultra-morphology confocal evaluation.
  
  
  RESULTS
  FTIR and Ca-CLSM analyses showed dicalcium phosphate dihydrate (Brushite) precipitation in MPA-etched dentine and on the bottom (front of demineralisation) of the OPA-etched dentine. Statistical analysis showed similar μTBS for both etching procedures after 24h. The μTBS of specimens in OPA-group dropped significantly (p<0.05) after six month; the specimens in the MPA group showed no statistically difference (p>0.05). CLSM depicted no evident sign of nanoleakage within the resin-dentine interface of the MPA-treated specimens, while the specimens in OPA-group presented intense nanoleakage and interface degradation.
  
  
  CONCLUSIONS
  The use of MPA (60s) as an alternative dentine conditioning agent in etch-and-rinse bonding procedures may be a suitable strategy to create more durable resin-dentine bonds.
authors.affiliation: Division of Dental Materials, Piracicaba Dental School, Piracicaba, Brazil.
authors.forename: Victor Pinheiro
authors.initials: VP
authors.lastname: Feitosa
authors.forename: Maria Giulia
authors.initials: MG
authors.lastname: Bazzocchi
authors.forename: Angelo
authors.initials: A
authors.lastname: Putignano
authors.forename: Giovanna
authors.initials: G
authors.lastname: Orsini
authors.forename: Arlinda Luzi
authors.initials: AL
authors.lastname: Luzi
authors.forename: Mário Alexandre Coelho
authors.initials: MA
authors.lastname: Sinhoreti
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Watson
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sauro
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods*; D000328:Adult; D002130:Calcium Phosphates / Q000737:chemistry*; D011232:Chemical Precipitation; D001840:Dental Bonding; D003763:Dental Leakage / Q000145:classification*; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D018613:Microscopy, Confocal / Q000379:methods; D010636:Phenols; D010756:Phosphoric Acids / Q000737:chemistry*; D010757:Phosphorous Acids / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical; D013454:Sulfoxides; D013499:Surface Properties; D013718:Tensile Strength; D055815:Young Adult
chemical_list: D002130:Calcium Phosphates; D017220:Dentin-Bonding Agents; D005456:Fluorescent Dyes; D008689:Methacrylates; D010636:Phenols; D010756:Phosphoric Acids; D010757:Phosphorous Acids; D011109:Polymethacrylic Acids; D013454:Sulfoxides; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C074277:ethoxylated bis-phenol A dimethacrylate; C005044:hydroxyethyl methacrylate; C030242:phosphoric acid; D016650:Fluorescein-5-isothiocyanate; C043639:metaphosphoric acid; C494366:calcium phosphate, dibasic, dihydrate; C016833:xylenol orange
keywords: Bond durability; Calcium-staining technique; Confocal microscopy; Etch-and-rinse adhesives; FTIR vibration analysis; Meta-phosphoric acid; Resin–dentine interface ultra-morphology