Microhardness of acid-treated and resin infiltrated human dentine.
OBJECTIVE
The aim is to determine if superficial or deep dentine microhardness (MH) is affected by different chemical dentine pre-treatments performed for resin bonding.


METHODS
Dentine discs of superficial (SD) and deep dentine (DD) were obtained by transversally sectioning the crowns of human third molars. Knoop MH was measured after different treatments: (1) polished up to 4000 grit, (2) polished and etched (37% ortophosphoric acid for 15 s), (3) resin (Single Bond -SB-) infiltrated dentine after acid etching, (4) polished, etched and treated with 5% NaOCl for 2 min, (5) resin infiltrated (SB) after etching and NaOCl treatment. For resin infiltrated surfaces care was taken in order to remove the excess adhesive layer, and obtain infiltrated dentine, by measuring thickness of the sample before resin infiltration and polishing after resin infiltration until obtaining the initial thickness of the sample. Indentations (n=20) were performed on moist surfaces with a standard Knoop MH tester (20 g, 5 s). Data were expressed in Knoop Hardness Numbers (KHN) and analysed by ANOVA and multiple comparisons (P<0.05).


RESULTS
Dentine KHN decreased on both SD and DD after acid etching. NaOCl treatment after acid etching did not affect MH on SD, but KHN of DD was lowered. Resin infiltration increased KHN but did not recover the initial MH values in both SD and DD.


CONCLUSIONS
Treating dentine with either H3PO4 or NaOCl caused marked reduction of its surface hardness and subsequent resin infiltration was not capable to restore it.
Toledano
Manuel
M
Department of Dental Materials, School of Dentistry Granada, University of Granada, Av. Fuerzas Armadasn degree 1, 1 degree B, 18014 Granada, Spain. toledano@ugr.es
Osorio
Raquel
R
Osorio
Estrella
E
Prati
Carlo
C
Carvalho
Ricardo M
RM
D000134:Acid Etching, Dental; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003777:Dental Prophylaxis / Q000295:instrumentation; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006244:Hardness; D006801:Humans; D016877:Oxidants / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry; D012973:Sodium Hypochlorite / Q000737:chemistry; D013499:Surface Properties
D003188:Composite Resins; D017220:Dentin-Bonding Agents; D016877:Oxidants; D010756:Phosphoric Acids; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D012973:Sodium Hypochlorite