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Application of Raman Spectroscopy and Micro-Indentation to Micro-Map the Path and Boundary of NaOCI-Induced Dentine
Yuan Ng1, Michele Recchia1, Cristina Pereira1
1Unit of Endodontology, Divisions of Restorative Dental Science, UCL Eastman Dental Institute, University College London, London, UK.
Objectives:
To apply Raman spectroscopy and micro-indentation to micro-map the path and boundary of NaOCl-induced dentine collagen changes in an ex-vivo root canal irrigation model.
Material And Methods:
Root canals of extracted single-rooted teeth were prepared and irrigated with NaOCl or saline. Four teeth (NaOCl = 3; saline = 1) embedded in epoxy resin and sectioned transversely into discs were Raman-analyzed on coronal surfaces from inter- and intra-tubular dentine in 4 quadrants over 12, 24, and 48 min-acquisition times. Eight additional teeth stratified by root maturity, irrigated with NaOCl (n = 7) or saline (n = 1), sectioned transversely and then embedded, were Raman-analyzed on apical surfaces at 18 equidistant (50 μm) points/quadrant for Amide bands. Micro-indentation of the corresponding facing sectioned surface was correlated with Amide band changes. Generalized linear and non-linear regression models were used for data analysis.
Results:
Spectral quality at 24/48 min was similar and better than at 12 min. Inter-tubular but not intra-tubular spectra were masked by fluorescence. Spectral features near the canal lumen ( < 500 μm) showed more significant collagen alteration and varied by tooth/quadrant but decreasingly towards the cemento-dentinal junction (CDJ) without a clear boundary. Significant (p < 0.0001) changes in Amide I/III bands up to 300 μm from the canal and were accompanied by deeper corresponding indentations upto 200 μm. Canal instrumentation had a significant (p < 0.0001) effect on both Amide-I and Amide-III bands.
Conclusions:
NaOCl altered dentinal collagen and reduced microhardness but varied with quadrants/teeth, without a definable boundary; collagen changes were obvious within 300 μm of the canal and microhardness changes within 200 μm but evident to a decreasing extent up to the CDJ.
