metaphosphoric-acid and Dental-Leakage

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.. 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.. 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.. 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.

Topics: Acid Etching, Dental; Adult; Calcium Phosphates; Chemical Precipitation; Dental Bonding; Dental Leakage; Dental Stress Analysis; Dentin; Dentin-Bonding Agents; Fluorescein-5-isothiocyanate; Fluorescent Dyes; Humans; Light-Curing of Dental Adhesives; Materials Testing; Methacrylates; Microscopy, Confocal; Phenols; Phosphoric Acids; Phosphorous Acids; Polyethylene Glycols; Polymethacrylic Acids; Spectroscopy, Fourier Transform Infrared; Stress, Mechanical; Sulfoxides; Surface Properties; Tensile Strength; Young Adult