Dr. Pierre Machtou Paris France Irrigation: Controversies and Facts



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Dr. Pierre Machtou

Paris France

Irrigation: Controversies and Facts
Dr. Machtou first acknowledged the previous presenters and their discussions of irrigation. He offered his clinical insights as to the possibilities for irrigation today.

Controversies in Irrigation – Machtou points out that we really don’t agree about much of the protocol:



  1. Types of Solutions?

  2. Concentrations?

  3. Combinations?

  4. Ultra-Sound Activation?

  5. Heating?


NaOCL

  • has antibacterial and Solvent Effects

  • but has a level of cytotoxicity as well

  • we don’t know what the best concentration


Evidence Based Dentistry (EBD)
Machtou believes that EBD is the intersection of three circles of influence:

1. Patient (preferences) 2. Dentist (expertise) and 3. Literature (evidence)



EBD is: “The integration of the best research evidence with clinical expertise and patient values” Sackett et al 2000. Machtou says that the clinical experience of the operator is very important (the main factor).
Dr. Machtou does not like the term “Apical Periodontitis” (AP). When we use the term “periodontitis”, it can be confused with periodontology. And when we use the term “Apical” we limit the location of the radiolucency to the area around the apical portion of the root. There is also no mention of the origin of the lesion when using the term AP. He prefers Schilder’s term Lesions of Endodontic Origin (LEO) or more precisely Periradicular Inflammation of Endodontic Origin (PIEO).
The goal of treatment is to remove this infection and eradicate the bacteria (Sjogren et al 1997). We then neutralize the root canal system with a good 3D filling to isolate the Periodontium from the oral environment. It is critical (as we have see in other presentations) to place a tightly sealing coronal restoration as soon as possible after completion of Endo treatment.


  • Bystrom & Sundqvist 1981 (studied impact of each stage of cleaning and shaping on outcomes. They used hand instrumentation and saline.)

They concluded: Instrumentation alone is inadequate for the complete elimination of infection.

  • Orstavik et al 1991

  • Dalton et al 1998 repeated Bystrom & Sundqvist’s 1981 study but this time using hand instrumentation and saline.) They got the same results – saying that there was no difference between hand instrumentation and rotary instrumentation.

Dr. Machtou thinks that this conclusion is misleading because the focus of the research was on instrumentation, without considering the effects of their irrigation protocol on the results.
We know that the main action of irrigation is to flush out debris. This important action and compliments the act of instrumentation. Baker et al JOE 1975


  • Siquera et al JOE 1999 said that it was “the combined effects of instrumentation AND irrigation that cause a significant decrease in bacterial cell numbers in the root canal.”

Endodontic research then moved to the concept of “Chemomechanical Preparation” where the researchers used NaOCl instead of saline.

  • Bystrom & Sundqvist 1983 used 0.5% NaOCl (Hand Inst.) – much better efficiency than saline

  • Bystrom & Sundqvist 1985 used 0.5% NaOCl or 5% NaOCl +EDTA (Hand Inst.) – surprisingly, they did not find any difference between the different concentrations. It was difficult to understand why a weaker solution would give the same results as the stronger solution. They theorized that the action of the EDTA on the smear layer permitted the weaker solution to be just as efficient.

  • Shuping et al 2000 used 1.25% NaOCl (Rotary Inst.) – got the same result as Bystrom & Sundqvist 1983

  • Siquera et al JOE 1999 used 1%, 2.5%, 5.25% NaOCl (Hand Inst.)

From these studies we can conclude that the by using either hand or rotary instrumentation – we can get the same results when the same solutions are used.


  • Dalton et al JOE 1998 – Bacterial Reduction with NiTi Rotary Instrumentation

  • 48 patients, Mandib. Premolar and MB of molars

  • Used saline, manual step back vs. ProFile .04 – 3 bacterial samples

Concluded- No significant difference in intracanal bacterial reduction was detected between hand and rotary instrumentation (negative samples 28%). Substantial reduction was achieved with progressive filing regardless of the file type. The larger we make the canals the greater the reduction of the bacteria.

  • Shuping et al JOE 2000 – Bacterial Reduction with NiTi Rotary Instrumentation and Various Medications

  • 42 patients, Mandib. Premolar and MB of molars

  • Used 1.25% NaOCl, ProFile .04, and Ca(OH)2/5 bacterial samples

Concluded- NaOCl irrigation with rotary instrumentation is an important step in the reduction of intracanal bacteria (negative samples 61.9%) significant difference in intracanal bacterial reduction was detected between hand and rotary instrumentation (negative samples 28%). Substantial reduction was achieved with progressive filing regardless of the file type.

The increase in size of the NiTi rotary files and one week use of Ca(OH)2 intra canal medication significantly reduce bacteria from infected canals (negative samples 92.5%)

  • Card et al JOE 2002 – The effectiveness of Increased Apical Enlargement in Reducing Intracanal Bacteria

  • 40 patients, Cuspids, Mandib. Premolar and MB of mandib. Molars

  • Profile .04 to 60 on single rooted teeth and 45 on molars

  • Light Speed to size 80 in single rooted teeth and 60 on molars

  • Used 1. % NaOCl

Concluded- After Profile – 100% of cuspid/bicuspid canals were bacteria free and 91.5% of molars. After Light Speed – the molar results improved to 89%. They said that simple root canal systems may be rendered bacteria free when preparation of this type is utilized.

  • McGurkin-Smith et al JOE 2005 – Reduction of Intracanal Bacteria Using GT Rotary Instrumentation

  • 31 patients with AP

  • Used GT vs. Larger instrumentation

  • 3 samples taken 1. Pre-instrumentation, 2. Post instrumentation, 3.After >1 week Ca(OH)2

  • Used 5.25% NaOCL, EDTA and Ca(OH)2.

Concluded- GT protocol failed to render the canal bacteria free in more than half of the cases. Ca(OH)2 application significantly further reduced bacterial levels. Larger apical instrumentation removed more bacteria in than small apical preparations.


    • The trend toward increase the size of the apical preparation was shown in Baugh & Wallace JOE 2005 The role of apical instrumentation in root canal Treatment: a review of the literature.

Machtou said that larger apical preparations evolved because of the concern about bacteria in the dentinal tubules and not just in the canals themselves. The more we enlarge the canal system – the more we seem to be able to reduce bacterial levels. He then discussed these results in detail:

Machtou says the conclusion by Card et al JOE 2002 that canals could be rendered 100% bacteria free is wrong- because we know that the current culturing techniques can only identify 12 species. With molecular monitoring techniques we can identify 40 species. The actual estimated number of species in the RCS is 90 – close to that of the number involved in Perio flora.
IS BIGGER BETTER?

In order for us to answer this question, we must understand the structure of dentin the areas that we are working.



    • Mjor et al IEJ 2001- showed that the apical dentin differs greatly from that in the middle and coronal aspects. It is a fibrodentin and it has fewer dentinal tubules (sometimes none).

    • Love JOE 1996 – showed that the pattern of penetration of bacteria (Strep. Gordini) varies with the level of the root canal system. In the cervical areas where there are many dentinal tubules penetration can reach 200 microns. But in the apical area where fewer tubules are present, penetration is only 60 microns.

Machtou believes that because of this minimal penetration of approx. 60 microns in the apical region, it is possible to remove this 60 micron layer of infected dentin with apical enlargement of only approximately TWO FILE SIZES. This has major implications with regard to “how big” is “big enough”.
Permeability of Root Dentin

    • Paque et al IEJ 2006- showed that tubular sclerosis (rather than the smear layer) impeded dye penetration into the dentin of endodontically instrumented teeth. Tubular sclerosis is a physiological phenomenon that starts in the third decade in life in the apical region and advances coronally with age. This was found to be the MAIN factor that influenced permeability of root dentin.

In infected teeth, the bacterial “front” is located close to the level of the foramen. So we have to treat the bacteria at this level.



    • Molven et al Endod Traumatol 1991 showed that bacteria are located in the apical 2 mms of root canals in 83.3% of untreated teeth with AP.

Machtou believes that instead of thinking in terms of apical enlargement, it should be better to think of length. If we stay short in this area, we are going to miss the apical anatomy that is the most complex part of the canal system. Instead of opening the lateral canals- greater enlargement of the apical area with instrumentation is:

    1. MORE likely to block the apical areas with smear layer debris

    2. MORE likely to block the lateral canals and dentinal tubules

    3. EDTA will then be unable to remove the smear layer in these and inaccessible and plugged areas




    • Paque et al IEJ 2006- concluded: “Consequently, the apical root dentin of the average endodontic case is most likely impermeable both to disinfectants and bacteria.” Bacterial clusters in teeth affected by AP are most frequently found around the apical portals of exit of the RCS where they have access to tissue fluid. When considering this, the clinical relevance of laboratory models using infected human or bovine dentinal tubules would appear to be somewhat questionable.

Machtou says that when you take cervical human or dentin samples with large tubules, remove the protecting cementum layer and then immerse the sample in a bacteria filled broth – of course you are going to get bacteria all the way inside the tubules! But how clinically relevant is this study? Is this a reliable model?
Bacteria can be found in 2 forms:

  1. A Planktonic state- a freed suspension , easily removed during cleaning and shaping procedures

  2. Biofilms – mostly found on the canal walls – we expect to remove these bacteria mechanically and by irrigation. But they are difficult to remove, especially in the isthmus areas.

Many studies (e.g. / Peters et al IEJ 2001) have shown that large amounts of canal remain uninstrumented. (In this study it was 35%). This results in a lot of biofilm remaining. BUT when shaping procedures are carefully carried out (he showed 3D reconstructions of canals shaped by himself and Ruddle) very little canal surface was left untouched – less than 10 %( with the exception of an isthmus area in the apical third). It is possible to do this with a crown down approach. If we use a “pre-enlargement” technique we can address these areas.
Patency

Machtou says that Apical Patency is a controversial issue but that in infected teeth it is a critical factor. (Routine patency checks and the use of patency files were first advocated by Schilder in his classic Dent. Clin of N. Am articles.) Because each time we use a patency file between an active or working file we:



  1. Confirm the end of the canal is not blocked

  2. Stir debris into solution

  3. Move fresh irrigant into the apical 2mm

This does not mean that we will place all files to the point of patency. Use of patency files in this way does not transport large amounts of bacteria into the apical area because the file sizes are very small and the files are only placed a very small distance past the foramen when checking patency. We shape “behind” (coronal to) this file. This means that the subsequent files are placed to a level coronal to this file and NOT at the level of the patency check.

Machtou points out that the main entity responsible for the periapical tissue repair is the PDL, therefore it does not matter whether or not the pulp stump is removed by the patency files. (Sequeira JF- Endodontic Topics 2005) Machtou insists that use of the patency file is very important for the elimination of procedural errors.

Machtou said that there are two main factors that affect the successful outcome of treatment and that these had been confirmed by the results of the Toronto Study (Faranzeh et al JOE 2004 – part 2 of the study) and Marquis et al JOE 2006 – part 3 of the study). They are:


  1. The presence of apical periodontitis prior to treatment

  2. Treatment Technique (The Schilder technique was significantly more efficient regarding the outcome). Machtou says that this shows that treatment technique and operator proficiency have a great influence on the results and are important factors.

Chugal et al OOO 2003 – Endodontic infection: some biologic and treatment factors affecting outcome. In infected teeth, each mm lost in working length decreases the rate of success by 49%. Therefore Machtou asks “Why do we choose to work short?”


John West (Boston U Thesis) asked Oral Surgeons to send him extracted, previously Endo treated teeth. After discarding perio involved and other non endo related failures he cleared the 95 sample teeth. In 100 % of the cases, he found at least one POE had not been cleaned and filled. Most of the cases had one thing in common -> blockage of the apical portion of the canal by dentin mud – not allowing for cleaning and filling of the complex apical anatomy.
The Dynamics of Irrigation

Irrigation has two main objectives:



  1. Mechanical Effects

  • Flush or loosen debris

  • Lubricate the dentinal Walls

  1. Chemical Effects

  • Have antibacterial effectiveness

  • Dissolve organic matter

  • Prefer to have limited or No cytotoxicity (to patient tissues)

Machtou says that while literally hundreds of papers have been written about the chemical effects of irrigation solutions, very few have focused on the most important aspects of penetration and exchange of these solutions – the DYNAMICS of irrigation. Because even the most powerful solution will be useless if it cannot penetrate the apical portions of the canal where it can dissolve the tissues and it also needs to be exchanged frequently for best effect.
NaOCL as a Tissue Solvent

Noenni et al JOE 2004 - Soft Tissue Dissolution capacity of currently used and potential Endodontic Irrigants. They used 1%(wt/vol) NaOCl, 10% Chlorhexidine (CHX), 3% and 30% Hydrogen Peroxide (H2O2) , 10% peractic acid, 5% dichloroisocyanurate (a.ka. hypochlorous acid) (NaDCC) and 10% citric acid. Results: None of the test solutions except for NaOCl had any substantial tissue dissolution capacity. It was concluded that this might be important when considering the use of irrigants other than NaOCl.


Zehnder et al OOO 2002 showed that in contrast to earlier statements, the results of the study do not demonstrate any benefit in buffering NaOCl with sodium bicarbonate according to Dakin’s method. It is the amount of available chlorine (not the pH, osmolarity or buffer capacity) that determines the tissue solvent abilities of NaOCl.
Machtou showed a video recreation of Grossman’s 1943 pulp dissolution experiment. (Broached pulps dissolving in a glass of NaOCl.)
Why is NaOCl such a good tissue solvent, as seen in this experiment?

Two reasons:

  1. We have a lot of available chloride in the solution that is in the glass

  2. We have perfect contact of the solutions with the pulp. They are literally swimming in the NaOCl.

Therefore, in order to try to get similar results in treatment, the NaOCL solution needs to have as much contact with the pulp tissue as possible AND the solutions need to be exchanged frequently to keep the levels of available chloride at maximum.
NaOCL Solvent Action – 4 main factors:

  1. Large amounts necessary (The, 1979)

  2. Contact with the Tissue (Trepagnier, 1977)

  3. Mechanically agitated (Moorer, 1982)

  4. Exchanged ( Baumgartner & Cuenin, 1992)


The Most Important Factor – Irrigation Dynamics

  • Canal Size and Irrigant Penetration

Machtou said that although the initial research was done in the 70 and 80s (Ram 1977, Moser & Heuer 1982, Abou-Rass 1982 and Chow 1983) he was pleased to see newer research in this area: Sedgley et al 2005 and van der Sluts et al 2006. They concluded that if we want to get good irrigation we should use thin needles or enlarge the RCS in order to facilitate the penetration of the needle or both. Machtou says that this is NOT the best way to irrigate the RCS.
Machtou says that the recent excellent paper by Zehnder’s (JOE 2006) is a paper about irrigants but not about IRRIGATION. He disagrees with the recommendation that the apical sizes be enlarged to a minimum size 35 (for adequate penetration and exchange of NaOCl). He believes he can do this without such enlargement.

Sequeira et al 1997 used 5 different preparation techniques with different apical sizes. They concluded that “None of the five instrumentation techniques (Step back to #25, Step Back + NiTi files to #25, US Technique -#30, Roane to #40, Canal Master to #32.5) totally debrided the entire RCS, especially when variations in the internal anatomy were present.” Machtou says that this study shows no matter what apical size you select – the apex is not perfectly cleaned.

In another Sequeira et al study in 2002, 4 different methods and solutions (NaOCl, Citric Acid, and CHX) to instrument canals (1. ARM – Alternating Rotary Method i.e./watch winding and GT Rotary Files) and a control. They were used to test the bacterial reduction of preparation techniques. They concluded that” There was no significant difference between the experimental groups. All of them were significantly more effective than the control group. They recognized the importance of using antimicrobial irrigants, regardless of the solutions or instrumentation techniques used.

Machtou concludes that using different apical sizes and different irrigants makes no difference in the final results.


Instruments shape, Irrigants Clean (Baumgartner & Mader 1987)

Instruments create space inside the RCS in order to allow penetration of the irrigants. Machtou is NOT concerned about smear layer removal. Why? - Because he says that this occurs where the instruments have already worked. So, if we have “already been there”, it should be easy to remove the smear layer at this location.


Machtou then showed a crude experiment in a standard “plastic block simulated canal”. (Pierre said that if you wish to use plastic blocks in experiments it is important to plug the apical foramen with wax in order to simulate the PDL – leaving the apex open prevents air bubble formation at the apex and this is NOT similar to the PDL. i.e./bubbles DO form in vitro and we have to simulate this as well) He used red dye to illustrate that even with the first scouting file; it was possible to get the dyed irrigation solution to the apex. When we delver irrigating solution into a canal with the irrigating tip alone- the solution does not move more than 1 mm beyond the length of the tip. The more we shape the canal system, the further the solution can be placed into the canal. Irrigation is therefore only efficient at the END of the cleaning and shaping procedure. That is the only time that we can completely exchange the solution at the apex.

It is also important to use an “up and down” motion with the needle. Thin needles are NOT used to get the needle tip further down the canal!! They are used because we need “reflux space” between the needle and the canal wall. The needle is always free in the canal. It is possible to exchange solutions in this way – even in lateral canals.


Yana, Y. Thesis - Boston University 1989. – In vivo comparison of NaOCL in RCS during cleaning and shaping procedures using BU technique and sonic instrumentation. The objective was assessment of irrigant penetration and exchange. 60 canals from vital teeth. 4 groups of 15 canals from anterior and posterior teeth. 23 gauge needles, Hypaque (a radio-opaque solution with similar properties to that of NaOCl) and NaOCl. Each time he irrigated, Yana took a film – 21 possible radiographs per canal. Both techniques were compared with NaOCL and Hypaque irrigating media. After WL was achieved, the canal was irrigated and he found that the irrigant only traveled one mm or so further than the tip. (As in Machtou’s plastic block experiment). Yana referred to this as”Passive Irrigation”. Using a pre-bent #15 K file he was able to move Hypaque to the WL. Using the files with the irrigation in this manner gives us “Dynamic” or “Active” irrigation.
(Although it appears that the placement of the instrument into the canal space moves the solution down the canal, Machtou says this is not entirely true. It is not the placement of the file (which merely displaces the irrigant in the canal) it is the movement of the file in and out of the canal that carries the solution apically. Machtou points out that it is only possible to create these conditions IF we have a 4 walled access cavity with a sufficient reservoir of irrigant in the chamber. If we do not reconstruct the lost tooth material prior to treatment – we lose the advantage of having this reservoir of fresh solution and that makes Active irrigation impossible to achieve.)
Yana continued to shape the canals using the standard BU cleaning and shaping technique and was able to get a #25 to WL. Without further work on the apical “deep shape” he still was not able to get passive irrigation to move the Hypaque to the apex. After working on the deep shape and apical finishing, finally he could achieve this. Furthermore, once this occurred, the proper shape allowed him to completely exchange the Hypaque irrigant with NaOCL – yielding a canal with no radio-opaque material in it after NaOCL rinse. Tapered preparations are integral to this process because they create a better hydraulic circuit.

Klinghofer, A. Thesis - Boston University 1990 duplicated and confirmed Yana’s research but this time on necrotic teeth. She showed that it was possible to involve the lateral canals in properly shaped necrotic teeth. She was able to demonstrate that if no mistakes are made during canal irrigation (i.e./clog the needle) then if we inject solution without pressure, there is no risk in immature teeth or wide open apices of extruding the irrigant beyond the tip of the root.


Siqueira et al JOE 2000- concluded that there was no significant difference between 1%, 2.5% and 5.25% NaOCl solutions tested with respect to reduction of bacterial population after instrumentation. “A regular exchange and the use of large amounts of irrigant should maintain the antibacterial effectiveness of the NaOCl solution, compensating for the effects of concentration.”
Moorer and Wesselink 1982 –Although any concentration of NaOCl between .5% and 5% may be successfully in endodontic, the mechanical aspects of the technique appears to be more important than the initial NaOCl concentration. They suggest that lower concentrations (between .5% and 2%) can be used as long as better mechanical technique and frequent solution changes occur.
Heating Solutions?

Temperature optimizes all chemical resections. Should we heat NaOCL? Machtou says “Yes”. He uses a “Coffee Warmer” technique in which a glass beaker is filled with NaOCL and set on a coffee warming device. The irrigants are aspirated into the irrigation syringes from this warmed source.


Berutti et al JOE 1996 did a study of the debridement capability of NaOCL at different temperatures.

Cunninghalm et al OOO 1980 showed that 2.6% NaOCL @ 37 degrees C had the same collagen dissolving ability as 5.25% @ 20 degrees C.

But for heated solutions; because the antibacterial elements in NaOCL (the available OCl- (the anion hypochlorite) and HOCl (hypochlorous acid) in weaker solutions are more quickly dissipated by evaporation – we have to change them more frequently than more concentrated solutions at lower temperatures. The solutions we get at the store (bleach) are mostly hypochlorite and contain little hypochlorous acid.


Frais et al IEJ 2001 – Some factors affecting the concentration of available chlorine in commercial sources of sodium hypochlorite. They heated the solution over 4 hours (causing a lot of evaporation.) They concluded

  • Stored under appropriate conditions commercially available NaOCL solutions may be diluted to obtain predictable concentrations.

  • Heating solutions of NaOCl may cause unpredictable changes to the concentration, depending upon conditions.

Sirtes et al JOE 2005 – The effect of temperature on NaOCL Short term stability, pulp dissolution capacity and antimicrobial efficacy. They concluded that:



  • Heated solutions remained stable during the observation period (60 min).

  • 1% NaOCl at 45degrees C dissolved pulp tissues as efficiently as 5.25% at 20 degrees C. While 60C/1% solution was significantly more effective.

  • A 100 fold increase in killing efficacy was observed between corresponding NaOCl solutions at 20 degrees C and 45 degrees C

This means that we can use a weaker solution and by heating the solution, it becomes more efficient while maintain its low cytotoxicity.
The importance of Shape

Unshaped canals

  • Cannot be filled in three dimensions

  • Cannot be cleaned (Schilder 1974)

Machtou adds that unshaped canals cannot be disinfected.
In order to get deep penetration of the solution, we need Deep Shape. There is no reason to over-enlarge (in a lateral aspect) the apical part of the RCS. We can maintain a small apical size and shape “behind” this patent opening with enough deep shape. For Machtou this means a .10 taper. If we get this deep shape we can solve the irrigation problem. This shaping can also be done by hand, not just with Ni-Ti rotaries in all canals. A simple way to check this degree of taper is to step back a series of ISO files or to ensure that a Medium (Non-standardized) gutta percha cone can be properly fit.
Coldero et al IEJ 2002 concluded: “It may therefore not be necessary to remove dentine in the apical part of the root canal when a suitable coronal taper is achieved to allow satisfactory irrigation of the RCS with antimicrobial agents.”
Similarly, Albretch et al JOE 2004 stated: “When a taper of .10 can be produced at the apical extent of the canal, there is no difference in debris removal between a size #40 and size #20 preparations.”
Yared et al JOE 1994 - duplicated Ostravik’s initial study on apical enlargement. They found: No statistically significant difference was noted between the size 25 and 40 file groups after instrumentation and after 1 week of CaOH dressing.”
Khademi et al JOE 2996 performed a study of minimum instrumentation size for penetration of irrigants in the apical third of the RCS. 40 extracted Mandibular molars. 4 groups Size 20, 25, 30 and 35 with .06 taper. 2 ml of 5.25 % NaOCl & 27 gauge needle. Final flush 17% EDTA for 5 min/canal and 5.25 % NaOCl fir 5 min. SEM evaluation. They concluded: Based on the results, it appears that the minimum instrumentation size needed for the penetration of irrigants to the apical third of the RCS is a #30 file.

Machtou says that the larger apical size was required to achieve the desired results because they were using a .06 rather than a .10 taper, as he recommends.


Brennec, F. (MS Thesis Paris 2004 to be published- done with Machtou) studied the “Dynamics of irrigation during the cleaning and shaping of curved root canals with the ProTaper system.” 30 MB curved and S curved canals of extracted mandibular and maxillary molars were instrumented with Yana’s Hypaque method. Machtou wanted to see if the radiographic resolution of Yana’s original images were sufficient to demonstrate that no Hypaque was left in the RCS. Measurements of the extent of Passive and active irrigation were made using digital subtraction. (Adobe Photoshop and Image J) The instrumentation sequence included final shaping with F1 to the apex, F2 .5 mm short and F3 1 mm short to get deep shape.

Machtou then showed a profile image of the canal and superimposed colored images of the levels of penetration of the irrigants when used with Active Irrigation. The scouting files managed to get irrigation to the apex but subsequent use of ProTapers showed increasing ability to get irrigants to the apex as the canals were shaped and instruments re-introduced: S1 (coronal 2/3-> much better), SX (better), S1 to length (perfect) , S2 to length (perfect), F1 to length (perfect). He concluded that use of files (and patency files) in this manner predictably moved and replenished irrigation to the apex. In his clinical technique Machtou supplements movement of the solution to the apex by agitating the solution with a master gutta percha cone placed to the apex. This not only results in better cleaning of the main canal but the pumping action allows entrance of the solution into lateral canals as well.

The same procedure was repeated in the experiment, this time using Passive Irrigation. Even with insertion of all the instruments as before and to length (up to a size F1) only approximately 70% of the canal was irrigated and the apical third could not be rinsed with Passive Irrigation. He then increased the size of the apical preparations with size F2 and F3. At that point Passive Irrigation levels were greatly improved (to 95% of the length of the RCS).

Although we want to use as much Active Irrigation as possible for best results, it is the deep shaping that allows the solution to reach the apex, even when Passive Irrigation is used. Therefore, we can conclude that during irrigation we use combine Active Irrigation and Passive Irrigation – and that when proper deep shape is achieved (with .10 taper), full access to the apical portions of the RCS is possible. Further studies are being done to asses the volumes of solution needed. By increasing the volumes during the final flushing sequence, there is an increase in the hydraulic circuits and complete canal irrigation to length can be obtained.



Conclusions of this Study

  • For active irrigation penetration is complete from S2 use

  • Passive irrigation penetration increases after each instrument utilization

  • Passive irrigation penetration improves with apical taper increase but involves partly the last 2 mms

  • Patency files improve penetration & exchange of irrigant

  • Mechanical agitation improves the penetration & exchange of irrigant in the last few apical mms.

  • Volume of irrigant during the final flush enhances the penetration of passive irrigation

  • Anatomical factors (length and curvature) are not limiting factors for the penetration & exchange of irrigation.

The importance of a tapered canal preparation is confirmed.
Machtou uses the UltraDent Navi-Tips (Yellow 29 gauge). He recommends the use of smaller syringes (Monoject 3 cc) with these tips. If you use larger syringes and press hard on the plunger, significant pressure can be developed as the solution moves through the tip and this can be dangerous. If you use the smaller Monject syringe, the solution will be safely ejected from the syringe into the canal system. He reiterates “Deeper is NOT better”. With these shapes - Deeper irrigation does not allow for the creation of efficient hydraulic circuits.

Machtou says that those who advocate the creation of “apical boxes” obtain better bacterial reduction because the larger apical box allows them to place the irrigation tip close to the apex. He says it is not necessary to enlarge the apex that much. With his technique the tapered preps create shapes that allow bacterial reduction without the need for deeper needle penetration.
How to improve Irrigants – Surfactants

Tensio-active agents (a.ka Surfactants) can be used to lower the surface tension of solutions, give better “wetting” ability and deeper penetration. Agents that have been tried in the past are: Benzalkonium chloride (Zephiran), Cetrimide, Tween-80, Triton X-100, and ethanol 95 percent.

Machtou 1980 Paris - did a Master’s thesis examining the effects of Tween- 80.

Leclerc 1986 Boston U - did a Master’s thesis in using Zephiran

Surfactants are effective when used with NaOCL but have been shown to produce no improvement in the properties of EDTA rinses.
Machtou is convinced that good cleaning and shaping techniques can remove almost all biofilms by properly using Schilder’s technique or ProTapers. Still, Nair et al OOO 2005 demonstrated that even after cleaning and shaping (with an unknown technique) they found biofilms inside unreachable areas (like isthmuses)
We now recognize 3 objectives that are required to obtain the best irrigation:


  1. Intracanal Delivery

  2. Intracanal Aspiration

  3. Activation (Agitation)

Fukumoto et al - IEJ 2006 produced an in vitro device that introduced a separate canula and suction into the canal space. They delivered the solution in the coronal area and aspirated it out using the apically positioned tube. This created a very efficient hydraulic circuit. They found there was no need to place the irrigating tip close to the apex. (In fact, when they reversed the configuration (aspiration in coronal aspect, delivery at apex – they got a lot of extrusion)


Activation of Solutions

Methods:


  1. Mechanical – agitating the master cone in the canal space for 1 minute using EDTA – then followed with NaOCl rinse. Machtou showed that this worked in plastic blocks. Even when the apical foramen was sealed with resin and an apical air bubble was intentionally introduced at the start- the solution could be easily distributed to the apex and lateral canals by GP cone agitation and pumping with a master cone.

  2. Hydrodynamic – RinseEndo by Durr. This device is a mechanical automatic delivery /aspirator system. Machtou points out that deeper placement of the tip actually creates LESS efficiency in the apical and lateral areas and that it is best left in the straight portions of the canal. The needle has a 7 mm groove to allow flowback of the irrigating solution.




  1. Sonics - Machtou and Ruddle have developed the EndoActivator- a wireless sonic handpiece device that uses a nylon tip to activate the solution. Studies are currently being done in 7 universities to asses the efficiency of the device.

  2. Ultrasonic

  • Gutats et al JOE 2005 attached a 20 gauge needle to a Min-Endo Ultrasonic unit, used at full power. They showed impressive isthmus and apical cleaning. However Machtou said that the study had a lot of flaws:

  • Used “unrestorable teeth”

  • Used GG burs 1-5 on MB canal of mandibular molars

  • Used GG series (30 tip) in a decreasing manner

  • Used GG accessory 35/.12 50/12 and 70.12 instruments! (Machtou said he was skeptical of the shapes of these canals!)

  • Full power ultrasonics

Machtou also has some serious questions as to whether ultrasonics are as effective as we think they are. When we see debris in solution, is this as the result of the tip contacting the canal or loosening biofilm debris? Or do the results occur because of the heating action of the ultrasonics on the solution?

Van der Sluts et al - IEJ 2005 – placing an ultrasonically activated smooth wire or K file 1 mm from the apex removed debris from an artificially created groove in the canal walls of resin blocks. Machtou said that he is not in favor of using any ultrasonically activated metal instrument that close to the apex. He feels metal contact can create more smear layer.

Laser

Chelating Agents

Huismann et al IEJ 2003 and Zehnder JOE 2005 are good reviews of chelating agents.

Grawehr et al IEJ 2003 studied the interaction of EDTA and NaOCL in aqueous solutions. They concluded: “EDTA retained its calcium complexing ability when mixed with NaOCl but EDTA caused NaOCL to lose its tissue dissolving capacity and virtually no chlorine was detected in the combinations. Copious amounts of NaOCL should be used to wash out the remnants of EDTA.” Machtou says that alternating the solutions is not a good idea since it actually decreases the effectiveness of the NaOCl. Machtou prefers to use Sybron’s Smear Clear or Septodont’s version of EDTA.
One of Machtou’s students, G. Charon (2006), did some recent work at the School of Chemistry in Paris. They have developed a model to assess the cleaning efficiency of the apical few mms of curved canals using 3 different modalities of irrigant activation and used a SEM. They studied the effects of agitation of the master cone with irrigation as he had previously shown. The SEMs showed good cleaning results.
MTAD (Biopure)

Zhang and Torabinejad JOE 2003 evaluated the Cytotoxicity of MTAD.



  • Removes the smear layer

  • Residual antimicrobial action

  • Used as a final rinse after 1.3% NaOCl

  • No solvent action on organic tissue

In this paper they decreased the NaOCl to 1.3% and said that MTAD was less cytotoxic than 5.25% NaOCl but more cytotoxic than 2.25% NaOCL. The rationale behind the use of MTAD was to limit the erosion of the peritubular dentin that was caused by using EDTA solutions. When comparing the SEM results obtained with NaOCL 5.25% +EDTA and NaOCL 5.25% + MTAD (used for 2 minutes), we find no difference. However the written instructions that come with MTAD say that is should be used as a 5 minute rinse (a long time!).
Tay et al JOE 2006 examined the ultrastructure of smear layer covered intra-tubular dentin after irrigation with MTAD. They concluded that MTAD is comparatively more aggressive in demineralizing intact intraradicular dentin, exposing demineralizing collagen matrices that were 1.5 to 2 times as thick as those produced by EDTA.
Tay et al JOE 2006 showed that use of MTAD had the potential for iatrogenic staining of the root.

Ruff et al JOE 2006 showed MTAD had no antifungal properties.

Dunavant et al JOE 2006 tested 1% and 6% NaOCL, 2% CHX, REDTA and MTAD. They concluded that both 1% and 6% NaOCL were more efficient in eliminating E. faecalis biofilms than the other solutions tested.

Clegg et al JOE 2006 tested 1%, 3% and 6% NaOCl, 2% CHX, and 1% NaOCL/MTAD. They concluded that 6% NaOCL was the only solution capable of rendering the bacteria nonviable and physically removing biofilms.


Chlorhexidine (CHX)

  • No cytotoxicity.

    • Not cytotoxic at .02% topical skin application. But IS cytotoxic at the 2% level we use in canals.

  • Residual antimicrobial action

  • No Solvent Action

  • Less effective on Gram (-) bacteria.

    • This is important to recognize because many often studies with CX have used E Faecalis - which is Gram (+). This means that it is not generally that effective in primary AP cases.

  • Produces a brownish precipitate when mixed with NaOCL

CHX 2% is basically used a FINAL FLUSH after NaOCl and as a INTRACANAL MEDICATION.
Machtou asks “Why do we continue to search for something else when we already have the most efficient, economical, easy to use product available to us – NaOCl? It is still the best.”

HealOzone

Machtou said that he was amused that Ozone was now being discussed and used by some groups of clinicians in 2006, considering that the French did research on it back in the 1960s. He said that although they used poor cleaning and shaping techniques back then, they found that application of Ozone did nothing. (Deltour et al Rev. Odontosomatol. 1970 (French)) Machtou said that Ozone has been completely discarded.
Machtou’s Irrigation Protocol

We need to avoid a complicated irrigation protocol; we need to keep it simple with a minimum number of instruments and a lot of solution.




Irrigant

Stage

Glyde or File Eze (Canal Lubricant) – for scouting narrow canals

Initial Negotiation

NaOCl 1-2.5% (Heated) 2ml/canal approx

Or until the canal liquid is clear of debris

Aspirate remnants of NaOCl


Crown Down Shaping

Liquid EDTA

2 ml or enough to fill the canal – activated with the master cone for 1 minute (timed)



Final Flush

NaOCl 1-2.5% - to remove EDTA – no activation

Final Flush


END


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