ABSTRACT
The main goal of this ex vivo study was to assess and compare the cellular and electrophysiological effects of two dental biomaterials, white mineral trioxide aggregate [WMTA] and calcium enriched mixture [CEM] cement, on neuronal cell excitability and electrical properties. A conventional intracellular current clamp technique was used to study the cellular effects of WMTA and CEM on the excitability, firing and the shape of action potential of neuronal soma membrane of F1 nerve cells. The dental biomaterials were prepared according to the manufacturers' directions and were applied to the bathing media and 0.05 mL of total mixture of each dental material at a distance of 3 mm from the cells. Findings indicated that exposure to both dental biomaterials shifted the irregular high frequency firing type observed in control conditions to a more regular low frequency firing pattern. Neuronal exposure to WMTA, but not CEM, significantly hyperpolarized the cell resting membrane potential. Both treatments significantly influenced the duration and the amplitude of action potentials. Extracellular application of either CEM or WMTA caused a significant increase in the after hyperpolarization [AHP] amplitude and AHP area, but the potentiating effect of WMTA was more effective than CEM. Treatment with WMTA or CEM resulted in a profound alteration in the firing behaviour of F1 cells and changed the AP characteristics. Both dental biomaterials reduced the neuronal activity possibly through enhancement of K[+] outward current. This may possibly explain the positive mechanisms of these biomaterials in regenerative endodontics, though further research is needed for such a conclusion
ABSTRACT
Mineral trioxide aggregate [MTA] is an endodontic material with different clinical applications e.g. root-end filling, pulp capping and perforation repair. It has been reported to possess antimicrobial and antifungal activities. The aim of this study was to examine the effect of White MTA on formalin-induced hyperalgesia in a rat with inflammatory pain. Inflammatory pain was induced by subcutaneous [SC] injection of formalin [40 microL, 2.5%] into the rat upper lip. The nociceptive behavioral responses i.e. shaking of the lower jaw and face rubbing were quantified. 40 uL of eugenol [50 mg/kg], WMTA [20 mg/0.2 mL] or ketoprofen were injected solely or in combination with formalin 2.5% and the behavioral responses were compared with those observed after formalin treatment alone. One-way ANOVA, Tukey were used for analysis of data. Formalin 2.5% provoked a biphasic nociceptive response, with an early and short lasting first tonic phase followed by a second phase. Solely SC injection of either WMTA or ketoprofen [a non steroidal anti-inflammatory drug] did not stimulate any significant nociceptive behaviour. However, injection of eugenol [a pain relieving agent] induced the early phase not the tonic phase of nociceptive response. WMTA, eugenol or ketoprofen injection 20 min before formalin injection attenuated the first phase but somehow prevented the induction of the second phase of nociceptive responses which were produced by formalin. Behavioural nociceptive responses including shaking of the lower jaw and face rubbing were significantly reduced when the subject was pretreated with either WMTA or ketoprofen [P<0.001]. In this study, WMTA induced pain reduction by suppression of the formalin-induced nociceptive response