A minimally destructive technique for removing the smear layer from dentine surfaces.
OBJECTIVE
To develop a minimally destructive technique for removing the smear layer produced by cutting and polishing specimens of dentine prepared for use in experimental studies, e.g. on occlusion of dentinal tubules by oral health products. The aim was to avoid the damage caused by conventional techniques utilising short exposures to solutions with very low pH.


METHODS
Two acetate buffers, pH 5.5, containing different concentrations of calcium and phosphate, with -log(ion activity product with respect to hydroxyapatite) (pI(HA)) of 55 or 56, were tested on slices of dentine using scanning electron microscopy (SEM).


RESULTS
A solution which, from previous work, was slightly undersaturated with respect to dentine mineral, with a pI(HA) of 56, was found to remove smear layers produced by cutting and/or polishing after 15 min. However, to reliably remove debris occluding the tubules an exposure time of 2h, followed by brief ultrasonication, was necessary. After 2h treatment with this buffer, only a small amount of demineralization of the surface was detectable by SEM, while calcium and phosphorus were detectable by X-ray dispersive spectroscopy.


CONCLUSIONS
It is possible to remove smear layers, and to open dentinal tubules, by a reasonably short exposure to an acidic buffer which is undersaturated with respect to dentine mineral.
Shellis
R P
RP
Applied Clinical Research Group, Dental School, Bristol, UK. r.p.shellis@bris.ac.uk
Curtis
A R
AR
D000085:Acetates / Q000737:chemistry / Q000494:pharmacology; D000134:Acid Etching, Dental / Q000379:methods*; D002021:Buffers; D002118:Calcium / Q000737:chemistry; D055598:Chemical Phenomena; D019343:Citric Acid / Q000494:pharmacology; D003775:Dental Polishing; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D003808:Dentin Solubility / Q000187:drug effects; D017886:Durapatite / Q000737:chemistry; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000494:pharmacology; D013052:Spectrometry, X-Ray Emission; D013997:Time Factors; D019246:Tooth Preparation; D014465:Ultrasonics
D000085:Acetates; D002021:Buffers; D010710:Phosphates; D019343:Citric Acid; D017886:Durapatite; D012973:Sodium Hypochlorite; D002118:Calcium