Permeability and morphology of dentin after erosion induced by acidic drinks.
BACKGROUND
The aims of this study were to evaluate 1) the alterations of dentin permeability after single exposure of dentin to several acidic soft drinks with different acid composition; 2) the effectiveness of smear layer on dentin surface to prevent erosion of sound dentin; and 3) the role of brushing procedures.


METHODS
Dentin discs from human third molars were prepared. Each disc was treated with 0.5 M neutral EDTA for 5 minutes to remove the smear layer and to calculate the maximum fluid flow rate for each disc (to which an arbitrary value of 100% was assigned) using a pressure apparatus working at 1.0 psi. An homogeneous thin smear layer was then recreated with an abrasive paper under water. The following acidic drinks were applied for 5 minutes onto dentin surface: cola drink (phosphoric acid), orange fruit juice (ascorbic + citric acid), white wine (tartaric acid), vinegar (acetic acid), and mucolytic syrup (benzoic and tartaric acid). Each sample was then brushed for 3 minutes. Finally, each sample was brushed with a toothpaste and, as the final step, etched with phosphoric acid for 1 minute. Permeability was measured after each step.


RESULTS
All acidic drinks were able to statistically increase dentin permeability and to open dentinal tubules by removing the smear layer.


CONCLUSIONS
The study demonstrated that acidic drinks increased dentin permeability by removing and dissolving the smear layer and smear plugs. The erosion of peritubular dentin and smear plug removal is the main agent responsible for the increase in dentin permeability and probably for clinical dentin hypersensitivity. Brushing procedures reduced dentin permeability, creating a new fine and thin smear layer. Toothpaste may play a protective role in preventing complete smear layer removal and reducing dentin hypersensitivity by producing a new artificial smear layer and deposit inside tubules. The use and the abuse of acidic drinks may damage dentin and increase the risk for dentin hypersensitivity.
Prati
Carlo
C
University of Bologna, School of Dentistry, Dental Emergency Therapy Unit, Department of Dental Sciences, Bologna, Italy. prati@alma.unibo.it
Montebugnoli
Lucio
L
Suppa
Pietro
P
Valdrè
Giovanni
G
Mongiorgi
Romano
R
D000143:Acids / Q000633:toxicity*; D000328:Adult; D000704:Analysis of Variance; D001628:Beverages / Q000633:toxicity*; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D003806:Dentin Permeability / Q000187:drug effects*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016014:Linear Models; D008855:Microscopy, Electron, Scanning; D016369:Smear Layer; D014077:Tooth Erosion / Q000139:chemically induced* / Q000473:pathology; D014099:Toothbrushing
D000143:Acids