Extract from the clinical article written by Dr Franck Diemer, originally appeared in Roots International, issue 1/2019.
Root-canal preparation is an essential step in endodontic treatment aimed at removing the current content of the root canal and preparing the canal or canals for filling.
The objective is to prevent the onset or recurrence of apical periodontitis. The use of rotary instruments with continuous rotation has made treatments faster, more comfortable and more predictable over the past twenty years. Many developments in the instrument realm have helped improve endodontic preparation systems. But despite all these advances, the complexity found in root-canal systems results in residual unprepared or unpreparable areas that require the complementary use of chemicals.
The market is full of different irrigation systems designed to further enhance this step. Many studies have been carried out to find the “perfect” irrigation solution, one that would meet all the criteria in terms of both efficiency and biocompatibility. Unfortunately, there simply is no such solution at this point. Sodium hypochlorite remains the gold standard of antiseptic solutions, while EDTA or citric acid remain the gold standard among chelating agents, required at the end of the preparation process. However, a needle recently developed by Produits Dentaires SA has given us a new choice of irrigation needle.
Irrigation in endodontics
Irrigation is an essential part in endodontic treatment. It is irrigation that allows us to prepare a root canal antiseptically. Irrigation is therefore required from the time of accessing the pulp chamber until the restorative material is introduced into the root canal.
The anatomies of root-canal systems are highly variable and can be very complex, so it will usually be impossible to mechanically prepare the entire system. However, it is still imperative to clean the entire root-canal system to achieve effective cleaning and to perform a successful endodontic treatment. For this reason, irrigation is the mandatory complement to the preparation of canals with rotary instruments, which, while reducing the bacterial count in instrumented areas by up to 90%, have no effect in areas that are not and cannot be instrumented areas.
A needle and a syringe
Various different irrigation systems are currently in use. Root-canal irrigation with a syringe and a needle is still the most common procedure today. Syringes are generally classified according to the design of their tips. Luer tips (which are not necessarily Luer-Lock tips) are conical, with a 6% slope. Luer-Lock tips feature the same conical design but also provide a locking mechanism for the needle that prevents the needle from accidentally sliding off the syringe. All needles have some form of connector with which to attach them to the syringe. The length and thickness of the needle can vary greatly, depending on the procedure to be performed. Its diameter is measured in gauge numbers, which very from 8 to 30, responding to 4.57 mm and 0.31 mm, respectively. The higher the gauge number, the slimmer the needle. It is quite possible to encounter two needles with the same lengths but different diameters.
Closed-ended needles for improved efficiency
The needle can end in a bevel, it can feature one or several lateral openings. Being familiar with these different needles is particularly relevant in endodontics. It has been demonstrated that closed-ended needles must be used to prevent irrigation solution to invade the periapical space. The pertinent studies were based on visualizing and examining the trajectories of irrigant particles of the irrigation solution at the root-canal level.
IrriFlex®, developed by Produits Dentaires, appears to be particularly interesting. This slightly conical 30-gauge needle is made of plastic and possesses two lateral vents arranged back to back just short of its closed end. This unique device facilitates an efficient lateral flow and reflux of the solution while controlling the extrusion risk. In effect, this means that the needle must never get stuck in the root canal (meaning that the preparation must be sufficient at all points) and that the liquid is ejected slowly and at low pressure, 1 to 2 mm from the working length. The lateral flow is conducive to the cleaning of isthmus and root-canal irregularities.
A promising alternative
A comparative scanning electron microscopic (SEM) study on debris removal showed that the IrriFlex® needle/syringe system was more effective than the conventional Endoneedle/syringe system. The IrriFlex® needle displays interesting properties during root-canal irrigation. This might be explained by its flexible nature that allows it to penetrate root canal network more easily without breaking, but also by the presence of several lateral openings at the same level, which balances the pressure and flow of the expelled irrigant. These openings ensure extra-broad exposure of the entire root canal.
Endodontic treatment requires root-canal preparation instruments that work in synergy with an irrigation solution. The complexity of root-canal systems prevents sufficient cleaning by mechanical preparation alone, mandating the additional use of chemical agents. The IrriFlex® needle appears to be a promising device, showing superior results to the traditional syringe/needle method. It is flexible and has a very small diameter (30-gauge), which allows simple and efficient access to the apical areas of curved roots.
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