IRRIGATION IN ENDO

Lubricants
Lubricants are used to make instrumentation easier. They reduce the friction between the endodontic instrument and the canal wall. Removing dentin by either hand instrumentation or mechanical instrumentation becomes much easier if the canal is wet or lubricated. Instrument lubrication can be achieved easily by using either sterile water, saline, or sodium hypochlorite (NaOCl) for most routine cases. These are readily available and inexpensive. There are also many commercial products currently being sold on the market today specifically for use as instrumentation lubricants. Most are some form of 17% ethylenediaminetetraacetic acid (EDTA) in liquid, gel, or paste formulations. Clinically, I have not found that any particular physical phase of the EDTA makes it a more effective lubricant than any other. However, only liquid 17% EDTA is easy to get into the canal, coats all the walls, and is easy to get out of the canal when I am finished using it. Therefore, I prefer 17% EDTA Plus (Essential Dental Systems) in water for use as a lubricant when instrumenting tight canals because it contains a surfactant which enables the EDTA to wet the canal walls more easily (Figure 1).

Disinfectants
The disinfectant category of irrigants comprises several products. The most frequently used irrigant is NaOCl. This irrigant has 2 great advantages: (1) it dissolves necrotic tissue, and (2) it kills bacteria quite effectively. In water, NaOCl ionizes to produce Na+, hypochlorite (OCl) and hypochlorous acid (HOCl). HOCl is the active moiety responsible for bacterial inactivation.12 The hypochlorous acid must be in direct contact with the bacteria in order to damage the membrane and kill the bacteria. Direct contact with bacteria and flow of the hypochlorite into the apical area is often quite difficult in canals that are not instrumented to wider apical diameters. Boutsioukis et al13,14 have demonstrated that root canal enlargement to greater than a size 25 appears to improve the performance of syringe irrigation. They also noted that increase tapering (.06) improved irrigant replacement. It has been shown that the presence of dentine caused delays in the killing of Enterocococcus faecalis using 1% NaOCl.15 In addition, E faecalis has been demonstrated to be more resistant to killing by NaOCl than Candidia albicans and Gramnegative rods.16-18 E faecalis has also been found to be present in many failed endodontic treatments. It would seem that the longer the hypochlorite is in contact with the bacteria and tissue, the better the outcome. Stojicic et al19 reported that dissolution of tissue increased almost linearly with the concentration of NaOCl.
They also reported that higher temperatures and agitation considerably enhanced the efficacy of NaOCl. The effect of agitation on tissue dissolution was greater than that of temperature. However, it has been reported by Sirtes20 that there is a 100-fold increase in killing efficacy between corresponding NaOCl solutions at 20°C and 45ºC (113ºF). Preheating NaOCl solutions appears to improve their necrotic pulp tissue dissolution capacity and efficacy against E faecalis cells. Al-Jadaa et al,21 in simulated curved canals, showed that passive ultrasonic irrigation (PUI) with a Ni-Ti tip promoted superior tissuedissolving ability than sonic irrigant activation while maintaining canal anatomy.
In order to take full advantage of the physical properties of NaOCl, I both heat it and use PUI to activate it. Brito et al22 tested the efficacy for killing E faecalis in vitro when using 3 different irrigation techniques. The researchers used conventional irrigation with NaviTip needles (Ultradent Products), conventional irrigation with NaviTip needles and activation with the EndoActivator (DENTSPLY Tulsa); then lastly, irrigation with the EndoVac system (Discus Dental). The EndoVac system is an apical negative pressure irrigation system. Brito et al22 found that, of any one of the irrigation techniques evaluated in their in vitro model, there was no evident antibacterial superiority.
Keeping these research facts in mind, the question then becomes: How do we formulate our endodontic irrigating protocol to make maximum use of the physical properties of NaOCl? The majority of my instrumentation is done using warmed 6% NaOCl as the irrigant. I place NaOCl in the canal using a drop-by-drop method (Figure 2). It is the chemical action of the NaOCl that does the work, not the washing of the canal with the irrigant. Drop by drop placement in the canal greatly reduces the risk of any hypochlorite accidents. This problem occurs when the hypochlorite is extruded past the apex and into the surrounding tissue. I also fill the entire access cavity with NaOCl (Figure 3). As the endodontic instrument is placed into the access cavity and then into the canal, it drags along some of the irrigant via capillary action into the canal. The hypochlorite in the access cavity and in the canal will also act as a lubricant that will facilitate easier instrumentation.