JCDA Express Issue 7 2012

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Is Ultrasonic Irrigation Needed in Endodontics?

Dr. Bettina Basrani, associate professor in the University of Toronto's faculty of dentistry, brings forward 3 articles that examine recent evidence in root canal irrigation techniques, with a focus on passive ultrasonic irrigation.

Introduction

• Successful endodontic treatment depends on effective removal of the remains of vital and necrotic pulp tissue, microorganisms, and microbial toxins from the root canal system.
• The intricate nature of root canal anatomy makes it impossible to shape and clean the root canal completely using the endodontic procedures at our disposal. Irregularities of the root canal wall, including oval extensions, isthmuses and apical deltas, are a major concern in particular.
• Within oval canals only 40% of the apical root canal wall area can be contacted by instruments when a rotating technique is used.
• Irrigation is an essential part of root canal treatment as it allows for cleaning beyond the root canal instruments.
• There is a need to evaluate the clinical efficacy of specific irrigation methods in well-controlled studies.

What devices are available for irrigant delivery and agitation for root canal irrigation?

Gu LS, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of Contemporary Irrigant Agitation Techniques and Devices. J Endod. 2009;35(6):791–804.

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JCDA Clinical Pearl: The question of whether currently available irrigant agitation methods are really necessary to clinically improve the outcome of endodontic treatment remains unresolved—their clinical efficacy has not been correlated with improved treatment outcomes.

Key Points:

• Technological advances in the last decade have resulted in new agitation devices that rely on various mechanisms of irrigant transfer, soft tissue debridement, and, depending on treatment philosophy, removal of smear layers.
• The devices can be divided into manual (like conventional syringes, manually pumping files or gutta percha points) and machine-assisted agitation systems. Overall, machine-assisted agitation systems appear to have resulted in improved canal cleanliness when compared with conventional syringe needle irrigation.
• Despite numerous in vitro studies on the effectiveness of various endodontic irrigation regimes, there are few well-controlled clinical studies. The review authors suggest that more studies are needed to effectively evaluate specific irrigation methods by using standardized debris or biofilm models.
• No evidence-based study is available to date that attempts to correlate the clinical efficacy of these devices with improved treatment outcomes.

Reasons for recommending this article: This article presents a comprehensive overview of the irrigant agitation methods currently available—categorized into the 2 broad categories of manual agitation techniques (like syringe and manual agitation) and machine-assisted agitation devices (like ultrasonic and sonic agitation and negative vacuum)—and their debridement efficacy. Understanding their clinical efficacy is crucial for scientists to improve the design and user-friendliness of future generations of irrigant agitation systems and for manufacturers' contentions that these systems play a pivotal role in contemporary endodontics.

Is passive irrigation more effective than syringe irrigation in cleaning the root canal?

van der Sluis LWM, Versluis M, Wu MK, Wesselink PR. Passive ultrasonic irrigation of the root canal: a review of the literature. Int Endod J. 2007;40(6):415–26.

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JCDA Clinical Pearl: Based on this literature review, passive ultrasonic irrigation (PUI) appears to be an adjunctive treatment for cleaning the root canal system. PUI is more effective than conventional syringe irrigation alone, in terms of removing remnants of pulp tissue, dentine debris, and planktonic bacteria.

Key Points:

• Ultrasonic irrigation of the root canal can be performed with or without simultaneous ultrasonic instrumentation.
• PUI describes ultrasonic irrigation using noncutting methodology that does not shape the canal.
• PUI can be performed with a small file or smooth wire (size 10–20) that oscillates freely to transmit acoustic energy to an irrigant in the root canal, inducing powerful acoustic microstreaming (the rapid movement of fluid in a circular or vortex-like motion around a vibrating file that occurs in the root canal).
• PUI can be an important supplement for cleaning the root canal system and is more effective in cleaning canals than traditional syringe irrigation, in terms of removing more organic tissue, planktonic bacteria, and dentine debris.
• PUI can be effective in curved canals and a smooth wire can be as effective as a cutting K-file.
• The taper and the diameter of the root canal are important parameters in determining the efficacies of dentine debris removal.
• During PUI, irrigation is more effective with sodium hypochlorite than with water.
• Two studies included in the review found ultrasonic irrigation is more effective than sonic irrigation in the removal of dentine debris from the root canal; one study found no difference.

Reasons for recommending this article: Even though this paper is a literature review and not a systematic review with meta-analysis, the authors provide a detailed critique of PUI, very clearly explaining the different parameters involved in enhancing the efficacy of commonly used irrigants. The review authors have expertise in the area and have published extensively on this matter.

Why use ultrasound as a technique for agitating irrigants in root canals?

Mozo S, Llena C, Forner L. Review of ultrasonic irrigation in endodontics: increasing action of irrigating solutions. Med Oral Patol Oral Cir Bucal. 2012;17(3):e512-6.

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JCDA Clinical Pearl: There is a general consensus that PUI is more effective than conventional syringe and needle irrigation in eliminating pulp tissue and dentin debris. However, the review authors conclude that higher success rates for endodontic treatment are achieved if conventional syringe irrigation is used in the initial phase of canal preparation, supplemented by a final phase of intermittent PUI after preparing the root canal system.

Key Points:

• Existing literature reveals that ultrasonic irrigation may have a very positive effect cleaning and disinfecting the root canal system as investigated in many in vitro studies.
• The combination of conventional irrigation together with ultrasonic irrigation facilitates access to difficult areas of the canal, improving the elimination of bacteria and the smear layer throughout the canal system, thereby contributing to higher success rates for endodontic treatment.
• PUI may be more effective than conventional syringe and needle irrigation in eliminating pulp tissue and dentin debris because ultrasound creates a higher speed and flow volume of the irrigant in the canal during irrigation. This eliminates more debris, produces less apical packing, creates better access for the chemical product to accessory canals, and produces the flush effect.
• Complete elimination of the smear layer with PUI appears to be achieved with 3% NaOCl, but other studies using different irrigants or NaOCl concentrations were less conclusive.
• Numerous researchers have shown that the use of PUI after manual and rotary instrumentation significantly reduces the number of bacteria, achieving significantly better results than needle and syringe irrigation.
• According to some authors ultrasound activation of the irrigant is most effective after the root system has been shaped, in the final phase of irrigation, as this enables the needle to be introduced throughout the working length thereby increasing irrigation efficacy. Some authors show the factors that favour irrigation are: needle depth, proportion of the radius of the root canal and the irrigation needle and diameter to which the channel is prepared.

Reasons for recommending this article: This is an interesting review of the existing literature which attempts to address the practical issues associated with using ultrasonics, particularly PUI, as a complement for cleaning difficult anatomic areas at the end of root canal treatment procedures. It is well documented that one of the most important procedures in nonsurgical root canal treatment and retreatment is chemomechanical preparation of the root canal followed by supplementary disinfection, such as through PUI, to effectively clean locations that are difficult to reach.