Karunanayake, G;
Ng, Y;
Knowles, JC;
Delgado, A;
Young, AM;
Gulabivala, K;
NAZHAT, SN;
(2019)
The effect of NaOCl and heat treatment on static and dynamic mechanical properties and chemical changes of dentine.
Journal of the Mechanical Behavior of Biomedical Materials
, 97
pp. 330-338.
10.1016/j.jmbbm.2019.05.042.
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Abstract
Objectives: To determine the effect of heat on flexural strength (FS), maximum strain (MS), storage modulus (SM), tan delta (TD) and chemical changes through micro-Raman spectroscopy of dentine exposed to 2.5% NaOCl or saline. / Methodology: Dentine bars were randomly allocated to 8 test groups. Half (groups 2,4,6,8) were treated with NaOCl for 20 min; the rest (groups 1,3,5,7) remained in saline. FS/MS were measured in groups 1–4 (n = 15) (3/4 were also heated to 200 °C & re-hydrated in saline). Micro-Raman spectroscopy was performed on bars from groups 1–4. SM/TD were measured in 5-8: in 5/6 (n = 10), repeated after heating (200 °C), then following re-hydration; in 7/8 (n = 3) after heating to 25–185 °C. / Results: Increase in MS on heat and FS/MS on heat + NaOCl was not significant (P > 0.05). SM increased (P = 0.06) after heat treatment but reduced to initial state after rehydration (P = 0.03). TD did not change (P = 0.4) after heat (200 °C) treatment but rehydration increased it compared with pre-treatment state (P = 0.001). For dentine bars pre-treated with NaOCl, SM did not change (P = 0.6) after heat (200 °C) treatment or rehydration but TD significantly increased (P = 0.02) upon re-hydration compared with pre- (P=0.007), or post- (P = 0.03) heat-treatment states. SM and TD varied between 25–185 °C with no consistent trend amongst the NaOCl pre-treated bars. Micro-Raman only detected chemical changes following NaOCl treatment in the mineral phase. / Conclusions: Exposure of dentine bars to heat and NaOCl produced only moderate changes to quasi-static but marked changes to viscoelastic properties, which may be explained by chemical alterations.
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