Safe and Effective 3-D Endodontic Disinfection: Laser Assisted Endodontic Irrigation

by Gary Glassman, DDS, FRCD(C); Fernando J. Meza, DMD

The ultimate goal of endodontic treatment is the prevention and/or treatment of apical periodontitis such that there is complete healing and absence of infection1 while the overall long-term goal is the placement of a definitive, clinically successful restoration and preservation of tooth structure.

Successful endodontic treatment depends on a number of factors, including proper instrumentation, successful irrigation and decontamination of the root-canal system right to the apical terminus in addition to hard to reach areas such as isthmuses, and lateral and accessory canals.2 (Fig. 1)

Fig. 1

 Micro-CT images of a maxillary molar demonstrate the root canal complexity. (Courtesy Dr. Ronald Ordinola Zapata, Brazil.)
Micro-CT images of a maxillary molar demonstrate the root canal complexity. (Courtesy Dr. Ronald Ordinola Zapata, Brazil.)

The challenge for successful endodontic treatment has always been the removal of vital and necrotic remnants of pulp tissue, debris generated during instrumentation, the smear layer (the organic and inorganic layer that is produced on the wall of the root canal during instrumentation), micro-organisms, and micro-toxins from the root-canal system.3

Even with the use of rotary instrumentation, the nickel-titanium instruments currently available only act on the central body of the root canal, resulting in a reliance on irrigation to clean beyond what may be achieved by these instruments.4

Dual irrigants such as NaOCl with EDTA are often used as initial and final rinses to circumvent the shortcomings of a single irrigant.5-7 These irrigants must be brought into direct contact with the entire canal-wall surfaces for effective action,8, 5, 9 particularly in the apical portions of small root canals where most of the lateral canals and canal ramifications exist.9,10

The combination of NaOCl and EDTA has been accepted as the “gold standard” and used worldwide for antisepsis of root-canal systems. The concentration of NaOCl used for root-canal irrigation ranges from 0.5 to 6%,11 depending on the country and local regulations; it has been shown, however, that tissue hydrolysation is greater at the higher end of this range, as demonstrated in a study by Hand et al. comparing 2.5 and 5.25% NaOCl. The higher concentration may also favour superior microbial outcomes.10 NaOCl has a broad antimicrobial spectrum,8 including E. faecalis. NaOCl is superior among irrigating agents that dissolve organic matter. EDTA is a chelating agent that aids in smear layer removal and increases dentine permeability,12,13 which will allow further irrigation with NaOCl to penetrate deep into the dentinal tubules.14

Irrigation Challenges-Apical Vapour Lock

Unless the root-canal foramen is wide open, the root canal behaves like a close-ended channel since the roots are surrounded by the periodontium. This produces an apical vapour lock, gas entrapment at the apical one third3 that resists displacement during instrumentation and final irrigation, thus preventing the flow of irrigant into the apical region and adequate debridement of the root-canal system.15,16 During irrigation, NaOCl reacts with organic tissue in the root-canal system, and the resulting hydrolysis liberates abundant quantities of ammonia and carbon dioxide.17 This gaseous mixture is trapped in the apical region and quickly forms a column of gas into which further fluid penetration is impossible. Extension of instruments into this vapour lock does not reduce or remove the gas bubble,18 just as it does not enable adequate flow of irrigant. Equally important is the concept that IF the NaOCl irrigant is NOT exchanged, the organic pulpal tissue will consume the NaOCl very quickly during the reaction of hydrolysis and in very short order all that is left over is water, which has no tissue dissolving effects at all.

The phenomenon of apical vapour lock has been confirmed in studies in which roots were embedded in a polyvinylsiloxane impression material to restrict fluid flow through the apical foramen, simulating a close-ended channel. The results of these studies was incomplete debridement of the apical part of the canal walls with the use of a positive-pressure syringe delivery technique.19-22 Micro-CT scanning and histological tests conducted by Tay et al. have also confirmed the presence of apical vapour lock.22 In fact, studies conducted without ensuring a close-ended channel cannot be regarded as conclusive on the efficacy of irrigants and the irrigant system.23-25 The apical vapour lock may also explain why in a number of studies investigators were unable to demonstrate a clean apical third in sealed root canals.21, 26-28

In a paper published in 1983, Chow determined that traditional positive-pressure irrigation had virtually no effect apical to the orifice of the irrigation needle in a closed root-canal system.29 Fluid exchange and debris displacement were minimal. Equally important to his primary findings, Chow set forth an infallible paradigm (Chow’s Paradigm) for endodontic irrigation: “For the solution to be mechanically effective in removing all the particles, it has to: (a) reach the apex; (b) create a current (force); and (c) carry the particles away.29 The apical vapour lock and consideration for the patient’s safety have always prevented the thorough cleaning of the apical 3 mm. It is critically important to determine which irrigation system will effectively irrigate the apical third, as well as isthmuses and lateral canals,30and do it in a safe manner that prevents the extrusion of irrigant.

Irrigant Delivery and Activation

The conundrum that the clinician faces is to SAFELY and effectively deliver the irrigants to the apical terminus, break the Apical Vapour Lock and allow constant exchange of irrigant and thereby continual hydrolysis of pulpal tissue by the NaOCl WITHOUT the risk of apical extrusion.

There are several ways to deliver NaOCL safely and effectively. The EndoactivatorTM Smartlight Pro System (Dentsply Sirona) (Fig. 2) sonically driven system activates intracanal reagents and vigorously produces the hydrodynamic phenomenon, providing the ability to debride into the deep lateral anatomy, remove the smear layer, and dislodge simulated biofilm clumps within the curved canals of molar teeth.31-33

Fig. 2A

 The EndoactivatorTM Smartlight Pro System (Dentsply Sirona) sonic activation system.
The EndoactivatorTM Smartlight Pro System (Dentsply Sirona) sonic activation system.

Fig. 2B

 The EndoactivatorTM Smartlight Pro System (Dentsply Sirona) sonic activation system.
The EndoactivatorTM Smartlight Pro System (Dentsply Sirona) sonic activation system.

The EndoVacTM (KavoKerr) apical negative pressure system (Fig. 3) has the ability to suction, thereby drawing and delivering the irrigant passively to the apex3 and positively addressing the problem of irrigation penetration past the apex into the periapical tissues which may result in treatment complications such as irrigation accidents. 34-37

Fig. 3

The Master Delivery Tip (MDT) accommodates different sizes of syringes filled with irrigant, the macro cannula is attached to the autoclavable aluminium hand piece and the micro cannula is attached to an autoclavable aluminium finger piece. The macro cannula, the micro cannula and the MDT are connected via clear plastic tubing. The tubes are connected to the high volume suction of the dental chair via the Multi-Port Adaptor.
The Master Delivery Tip (MDT) accommodates different sizes of syringes filled with irrigant, the macro cannula is attached to the autoclavable aluminium hand piece and the micro cannula is attached to an autoclavable aluminium finger piece. The macro cannula, the micro cannula and the MDT are connected via clear plastic tubing. The tubes are connected to the high volume suction of the dental chair via the Multi-Port Adaptor.

I have incorporated The Er,Cr:YSGG Waterlase iPlus All Tissue Laser (Biolase) (Fig. 4) for almost two years now in my practice for flushing out debris created during the shaping procedure and during the “main event” of endodontics, the final irrigation protocol. I have been amazed at the precision, accuracy and convenience of laser assisted endodontics, especially when treating complex root canal systems. (Figs. 5, 6,7 & 8)

Fig. 4

 Waterlase iPlus All Tissue Laser (Biolase).
Waterlase iPlus All Tissue Laser (Biolase).

Fig. 5A

 Preop radiograph of tooth #36 with very curved roots. Necrotic pulp with symptomatic apical periodontitis.
Preop radiograph of tooth #36 with very curved roots. Necrotic pulp with symptomatic apical periodontitis.

Fig. 5B

Working radiograph with hand files only negotiating coronal half
of root canal and inability to get to the apices.
Working radiograph with hand files only negotiating coronal half of root canal and inability to get to the apices.

Fig. 5C

Obturation radiograph revealing
complete fill of the root canals to their respective apices.
Obturation radiograph revealing complete fill of the root canals to their respective apices.

Fig. 5D

18 month re-assessment radiograph showing healing of the peri-radicular lesion.
18 month re-assessment radiograph showing healing of the peri-radicular lesion.

Fig. 6A

 Pre operative radiograph of tooth #15, only one canal negotiated with files. Symptomatic irreversible pulpitis with symptomatic apical periodontitis.
Pre operative radiograph of tooth #15, only one canal negotiated with files. Symptomatic irreversible pulpitis with symptomatic apical periodontitis.

Fig. 6B

 Final obturation radiograph with bonded core placed revealing trifurcation of the root canal system at the apical 1/3rd.
Final obturation radiograph with bonded core placed revealing trifurcation of the root canal system at the apical 1/3rd.

Fig. 7A

Pre operative radiograph of tooth #47. Symptomatic irreversible pulpitis with symptomatic apical periodontitis.
Pre operative radiograph of tooth #47. Symptomatic irreversible pulpitis with symptomatic apical periodontitis.

Fig. 7B

 Cone fit radiograph showing canals negotiated several mm short of the apical termini.
Cone fit radiograph showing canals negotiated several mm short of the apical termini.

Fig. 7C

 Final obturation radiograph with bonded core placed revealing “tree-like” branching’ at the apical 1/3rd of the root canal system
Final obturation radiograph with bonded core placed revealing “tree-like” branching’ at the apical 1/3rd of the root canal system

Fig. 8A

Pre-operative periapical of tooth #46. Necrotic pulp with chronic apical abcess (buccal sinus tract.)
Pre-operative periapical of tooth #46. Necrotic pulp with chronic apical abcess (buccal sinus tract.)

Fig. 8B

Pre-operative
CBCT of tooth #46. Sagittal view.
Pre-operative CBCT of tooth #46. Sagittal view.

Fig. 8C

Pre-operative CBCT of tooth #46. Axial view.
Pre-operative CBCT of tooth #46. Axial view.

Fig. 8D

 Post-operative periapical of tooth #46.
Post-operative periapical of tooth #46.

Fig. 8E

 7 month recall periapical of tooth #46.
7 month recall periapical of tooth #46.

Fig. 8F

7 month recall CBCT tooth #46. Sagittal view.
7 month recall CBCT tooth #46. Sagittal view.

Fig. 8G

 7 month recall CBCT tooth #46. Axial view.
7 month recall CBCT tooth #46. Axial view.

The failure rate of endodontic treatment is reported to be 2 to 14 percent.38 Though many factors have been implicated, some of the most common include the persistence of bacteria, poorly cleaned and obturated canals, and complications of instrumentation such as ledges, blockages, and perforations.39 The use of lasers as an adjunct in treatment minimizes failures by helping to ensure that the root canal system of the infected pulp tissue is thoroughly debrided and cleaned so that the canal space can be properly shaped and prepared for obturation. Dental lasers have been found to be effective for ablating hard tissues, opening dentinal tubules, eliminating biofilm and removing the smear layer more efficiently than syringe and needle irrigation.40,41 In addition to the physical effect created by the turbulent motion of the irrigant, lasers produce a chemical effect by increasing the reaction rate of the irrigant.41 The high-speed fluid motion created by dental lasers flushes out the debris attached to root canal walls, evacuates out debris coronally and does this right down to the apical terminus without apical extrusion, thereby satisfying “Chow’s Paradigm”.29

While the EndoActivator and EndoVac improve the delivery of irrigating solutions to the apex, they lack the power of laser derived photoacoustics. Due to the Waterlase’s wavelength of 2780 nm, water molecules are targeted for absorption of the light energy. The effect is a thermo-mechanical system that ablates dental hard and soft tissues and in endodontics, a hydrokinetic system that effectively agitates irrigating solutions.

Root canal therapy can be simplified into two phases: debridement and disinfection. Debridement of vital and necrotic tissue, and smear layer generated from mechanical instrumentation is performed in conjunction with irrigation of the pulp chamber and main canal(s). The Waterlase provides unparalleled debridement of the pulp chamber including the canal orifices. A higher energy is used for this initial debridement. Irrigating solutions are used in a continuous fashion with an irrigating syringe or for added simplicity, the Master Delivery Tip (MDT), from the EndoVac system.

Disruption of pulp tissue and “pulp stones” are observed in this phase of top-down debridement. Isthmuses on the floor of the pulp chamber are cleared, all while allowing for better visibility of canal orifices including calcified ones.

After the initial opening of the canal orifices with rotary NiTi and hand files, we continue on with our top-down approach and enter into the main canal(s). One of the major benefits of the Waterlase iPlus, is that it’s design and protocols give you full control of photoacoustics throughout the root canal treatment; whether it’s in the chamber or in the canal. As we begin instrumentation of the main canal(s), radial firing tips are introduced at lower energies bringing the photoacoustic effect safely and closer to the apex. Smaller tips such as the radial firing tip2 (RFT2), at 200 microns in diameter or approximately a size #20 hand file, allow for mid root placement in the canal(s) for the most conservative preparations or narrow canals. What follows is enhanced irrigation of the entire root canal system as we begin the disinfection phase. Irrigating solutions including NaOCl and EDTA are agitated and slightly warmed by the laser’s mechanical and thermal effects. This is all accomplished while eliminating the above mentioned vapour lock scenarios of traditional endodontics.

Chamber and canal wall boundaries play a role in laser photoacoustics just as the size and walls of a concert hall are customized for maximal acoustics. The final shape of the pulp chamber, endodontics access, and final canal preparation influence the laser generated cavitation and streaming effects. By placing the tips into the chamber and canal(s), proper debridement and disinfection is achieved . While ultrasonic devices are much less expensive and capable of producing cavitation and streaming, their effect is greatly reduced and even eliminated in smaller canal preparations since the ultrasonic tips are prevented from oscillating freely as they touch the canal walls. This dampening effect does not occur in laser photoacoustics and therefore the ultimate goal of canal debridement and disinfection, while maximally conserving tooth structure is realized.30

We have entered into the dawn of tooth-focused treatment aimed at dentin conservation, and shrugged off file-focused treatment, where we sacrifice valuable tooth structure to satisfy our current methodologies. The future of endodontics has never been brighter! With the development of safe and effective protocols resulting in the proper agitation of irrigating solutions, lasers, like the Waterlase iPlus have the potential to remove 100% of the organic tissue and 100% of the microbial contaminants right to the apical terminus. Successful endodontic treatment may be taken to levels never seen before! 

Oral Health welcomes this original article.

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Dr. Gary Glassman raduated from the University of Toronto, Faculty of Dentistry in 1984 and from the Endodontology Program at Temple University in 1987. The author of numerous awards and publications, Dr. Glassman lectures globally on endodontics, is on staff at the University of Toronto, Faculty of Dentistry in the graduate department of endodontics. 

Dr. Meza is a 2002 graduate of the University of Connecticut School of Dental Medicine. Dr. Meza received his Certificate in Endodontics from Temple School of Dentistry in 2004. Dr. Meza has lectured for Biolase in hands-on courses and provided in-office training to endodontists in the USA and Canada.

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