A comparative ex-vivo study of effects of different irrigation protocols with/without laser activation on the root dentine’s micro-hardness

Abstract

To compare the effects of different irrigation protocols, with/without laser activation, on the radicular dentine's micro-hardness. Methods: Eighty-two human extracted premolars were decoronated and divided into 7 groups. Roots were longitudinally split into two halves. The micro-hardness was measured for one half before and after irrigation protocols. The groups were; G1: MTAD without laser-activation, G2: MTAD with laser-activation, G3: sodiumhypochlorite (SH) with laser-activation, G4: SH then EDTA with laser-activation, G5: SH then MTAD with laseractivation, G6: SH without laser-activation. G7: distilled water (control). In the two-irrigants groups G4 and G5), samples were irrigated first with SH then with MTAD or EDTA irrigants, which were activated by the laser. The difference between the before-and after-irrigation micro-hardness was calculated to obtain the microhardness difference. Data were analyzed using the Paired Sample-t and Two-ways ANOVA tests at P=0.05. Results: Overall, the mean dentine's micro-hardness after-irrigation (103.1) was lower than before-irrigation (116.1) (P<0.001); except for the distilled-water group, (116.6 and 112.9, respectively) (P=0.075). The microhardness reduction of SH without laser-activation group (32.5) was the greatest (P<0.001). The single-irrigant or laser-activation irrigation protocols caused significantly less micro-hardness reduction compared to the two-irrigants or no laser-activation protocols. The mean micro-hardness reduction of SH and MTAD groups (both with laser-activation) (5.8 and 9.3, respectively) were significantly lower than other groups, but not from that of the control group (3.7). Conclusion:Using irrigants significantly reduced the root-dentine's micro-hardness. Although irrigants agitation by an Er: Yag laser significantly minimized micro-hardness reduction, it did not suppress the adverse effects on dentine micro-hardness when two-irrigants were used.

Evolution of the combined effect of different irrigation solutions and activation techniques on the removal of smear layer and dentin microhardness in oval-shaped root canal – An in-vitro study

“…In consistent with our results, Akbulut et al found that PIPS activation did not cause an additional decrease in dentin microhardness, indicating that the alterations in dentin mineral content and dentin microhardness were mainly affected by the irrigation solution, not by the activation technique [23]. Differently, Quteifani et al found that Er:Yag laser-activation (2 w power, 15 Hz frequency) of irrigants resulted in significantly less reduction of micro-hardness when compared to no-laser-activation [22]. This discrepancy may be related to the different laser parameters, which results in different degrees of changes in the chemical components [22].…”

“…The flow rate during CNI affects significantly the flow pattern within the root canal [ 32 ]. Unfortunately, this parameter was overlooked in most studies, and low flow rate was adopted [ 10 , 22 , 28 ]. Hardly any irrigant refreshment could be achieved apically to the needle when irrigating at a very low flow rate (0.02 mL/s), but a flow rate at 0.15–0.2 mL/s can provide refreshment up to 1 mm apically to the needle [ 32 , 33 ].…”

“…Although the influences of root canal irrigants on dentin composition and microhardness have been extensively investigated, the results are inconsistent due to the heterogeneity of experimental design [ 20–23 ]. Furthermore, whether the effect of irrigants on these parameters varies according to the activation mode remains controversial [ 22 , 23 ]. Such investigations are essential to strategize irrigation protocols with the better capacity for smear layer removal and less impact on dentin characteristics, such as microhardness, elastic modulus, fracture resistance, etc.…”

Effect of Irradiation with 980-nm Diode Laser on the Microhardness of Young and Old Root Canal Dentin after Treatment with Chemical Solutions

“…It has wavelengths that range from 655 to 980 nm, which are suitable for dental use. The diode laser (810-980nm) has the capacity to penetrate dentinal tubules and reduce bacteria counts up to 500 μm depth (9) .…”

“…In actuality, these variables are related to a rise in the temperature of the dental tissues. As a result, the chemical and physical properties of dentin may change and microhardness may alter as a result of laser activation (9) . Accordingly, the study was intended to evaluate the effect of diode laser 980-nm on the microhardness of young and old root canal dentin after treatment with chemical solutions.…”