SEM-EDX study of prepared human dentine surfaces exposed to gingival retraction fluids.
OBJECTIVE
To evaluate the effects of gingival retraction fluids (GRF) on prepared dentine surfaces, and to test the null-hypothesis that prior exposure of dentine surfaces for prolonged period to any of the fluids evaluated does not influence acid-etching of the exposed surfaces.


METHODS
The investigation was carried out using SEM and energy-dispersive X-ray analysis (EDX). The GRF studied were Hemodent (HMDT), Astringedent (AST) and Ultradent buffered 25% Aluminium Chloride (ULTB). Longitudinal sections of 220-grit ground dentine surfaces were exposed to GRF for 0.5-, 1-, 2- and 5-min (n=4 each). Another group of samples was produced by 20s application of 35% phosphoric acid (PA) on GRF-pretreated dentine. Control samples were not exposed to GRF. Differences in etching effect-a function of the Ca-contents detected by EDX, were analysed using Friedman's and Wilcoxon's rank test (P<0.05).


RESULTS
The SEM demonstrated the presence of a relatively non-porous amorphous dentine matrix, but many of the dentine tubule orifices remained occluded. Granular precipitates, which remained even after acid-etching, were noted on surfaces exposed to Hemodent for 5 min. Characteristic crystal growth was observed on surfaces exposed to Astringedent for 1- or 2-min prior to acid-etching. The EDX data demonstrated that there were differences in resulting Ca-content; ULTB >AST>HMDT>ULTB+PA>HMDT+PA>AST+PA>PA, but AST and HMDT were not significantly different.


CONCLUSIONS
The exposure of dentine prepared surfaces to these three GRF altered its morphology and reduced the dentine's susceptibility to acid-etching, thus the null-hypothesis is rejected.
Ayo-Yusuf
Olalekan A
OA
Department of Community Dentistry, School of Dentistry, Room 6.43-2, Oral and Dental Hospital, University of Pretoria, P.O. box 1266, Pretoria 0001, South Africa. lekan.ayoyusuf@up.ac.za
Driessen
Cornel H
CH
Botha
Andre J
AJ
D000134:Acid Etching, Dental; D003764:Dental Materials / Q000494:pharmacology*; D003804:Dentin / Q000187:drug effects* / Q000648:ultrastructure; D004577:Electron Probe Microanalysis / Q000379:methods; D006801:Humans; D008855:Microscopy, Electron, Scanning; D009930:Organic Chemicals / Q000494:pharmacology; D018709:Statistics, Nonparametric
D003764:Dental Materials; D009930:Organic Chemicals; C073695:Ultradent drying agent