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PATHOGENESIS OF APICAL PERIODONTITIS AND THE CAUSES OF ENDODONTIC FAILURES
P.N.R. Nair
Institute of Oral Biology, Section of Oral Structures and Development,
Center of Dental and Oral Medicine, University of Zürich, Plattenstrasse 11,
CH-8028 Zürich, Switzerland; nair@zzmk.unizh.ch

Dr. Julian Webber

London, England

Management of Endodontic Failure

 

Dr. Webber opened with compliments to ROOTS and praised it as being one of Dentistry’s “most exciting recent innovations”.  

 

Management of Endodontic Failure is an important issue because the standards of Endodontics around the world are poor, therefore we have many failures to deal with and retreatment is a big part of many practices. We need to know how to save some of these teeth lest they end up as fodder for the Implantologists.
 
Firstly, we need a Biological and Anatomical understanding of Endodontic Success and Failure. Rather than use the term Apical Periodontitis (AP), Dr Webber prefers the term Periodontitis of Endodontic Origin (PEO) because we all know PEO can occur anywhere around the surface of the root that is inside the supporting bone – not just apical. He quoted classic studies by Kakehashi (1965) Moller (1966, 81) and Sundqvist (1976). Failures are undoubtedly bacterially related. We need to eradicate or eliminate the bacteria to a sufficient level, we will get healing.  We must also eliminate the substrate that the bacteria thrive upon. However, the complexity of the RCS anatomy makes this is a tall order.
 

Aim of Treatment:
We need to eliminate infection in the canal system and at the same time add a coronal seal to enhance the apical seal at the end of the RCS.  (Quotes Sjogren 97 Saunders & Saunders 94 Ray and Trope.) Although widely quoted, we shouldn’t let Ray and Trope’s study (that showed that quality of coronal restoration was sometimes MORE important than the quality of the endodontic treatment) be too influential. We need to do the best possible job in all aspects of treatment – eliminate bacteria, eliminate the substrate, fill in 3D and have a good coronal seal – in order to have optimal treatment success.

 

The quality of endodontic treatment around the world is generally poor. He showed a chart of studies of the
Chart - Prevalence and Quality of Endodontic Treatment: Inadequate Treatment (where filling is not within 1-1.5 mm from radiographic apex). 10 studies from Eu and N. Am. were shown (1990-2002). Success rates varied from as high as 87% to a low of 50%. Webber makes an excellent point: While we on roots continue to debate the merits of filling to the RT or patency – if we could just teach the General Practitioners of the world to clean adequately to within 1 mm of the apex and then put in a quality endodontic filling with a good coronal restoration, we would see much better results for Endodontics in general. While we Endodontists continue to argue about prep size, taper, location of filling, puffs and patency, etc.  – it will be a long time before we can persuade the whole world that Endodontic treatment is predictable, retreatment is predictable and that implants are NOT the answer.

 

Chart - Prevalence and Quality of Endodontic Treatment: Inadequate Treatment/Presence of AP (same studies from Eu and N. Am. (1990-2002)). We see that where the standard of RCT of poor – the associated level of PA disease is high. We need to elevate the standards so that these figures are not looked upon with glee by the Implantologists and are used against us.

 

In 1986, the late Dr. Herbert Schilder quoted the term “Retreatdodontics” and said that “the future of Endodontics lies in the Retreatment of Endodontic Failures”. 75 % of the cases in Webber’s practice are retreatment. Even if our success rates are in the 90s %, we still have a significant percentage of retreatment that is required all over the world.

 

 

Do Retreatments work?
Webber quotes Bergenholtz et al Scand J. Dent Res 87 217:233 that states: Treatments with technical shortcomings could, following retreatment, be markedly improved as regards effectiveness and distance to apex. Following a 2 year observation period of 556 cases, retreatments carries out because of technical inadequacies alone were successful in 94% of cases.

Abott PV (Aust Dent J.1999) A retrospective analysis of the reasons for and the outcome of conservative endodontic retreatment and periradicular surgery
- An in office study 575 teeth over 6 years. 555 (96.5%) were assessed as successful. All teeth were disassembled/removed all coronal obstructions/coronal caries and bacteria. When done in this way – (no compromises) 92% success was achieved after only 3-6 months.

Doornbusch et al IEJ 2002 Radiographic evaluation of cases referred for surgical Endodontics

278 radiographs of cases referred for surgical endo were assessed by an Oral surgeon, GP and Endodontist. OS said 41% of cases were amenable to conventional endo ReTx, GP 67% and the Endodontist 80%. It concluded that most teeth referred to surgical treatment to an OS could be retreated by orthograde nonsurgical TX rather than surgical RCT.

 

Indications for SRCT ReTx

- Procedural Errors in the apical third. Webber does only about a HALF DOZEN SURGICAL CASES PER YEAR!!  He only does it in situations where there is no other possible avenue of treatment. He shows an example of previous tx with badly torn apex – he did SRCT on this max premolar but said that this was the only SRCT he did during about 6 months of cases last year.

 

Retreatment Indications:

·         Failure of initial therapy or inadequate retreatment

·         Inadequate root filling radiographically or clinically checked in situ without evidence of failure in a tooth scheduled for placement of a new restoration. ( It doesn’t matter if no symptoms or no pathology – it still needs a good endo under the new restoration)


Problems with Retreatment

·         Frustration

·         Unpredictable results

·         Profitability

 

Retreatment Steps

  • Coronal Disassembly
  • Establish Access to the RCS
  • Remove Canal Obstructions
  • Establish Patency
  • Shape, Clean and Fill

 

Costing Retreatment Fairly and Sensibly

Ruddle (1996) How to profit from Endo: Finding the fair fee for Endodontics
Dent Econ 88(11)30

Retreatment is “A complex procedure that should cost the patient the same or less than the alternative to compensate the extra time required to achieve natural tooth retention.”  If you charge the same fee for conventional tx that you do for ReTx you will:

  1. Not make any money
  2. Undervalue the worth of the procedure.

You must sell the value of the retreatment of the procedure to your patient. You need to educate the patient and say that saving the tooth in this manner will cost you “a little bit less” than having the tooth extracted and replaced with an implant. Webber feels that, when faced with this decision, most patients would opt for retreatment. (This assumes that the perio condition is good and that the tooth can be properly restored.)

 

Webber then shows a disassembly case. Crown cut off, core dissected. Post removal, silver cone removal from core material. Access recleaned, canals shaped and cleaned and then filled. Webber charges 50% more than conventional endo fee when retreating a case like this.  Webber believes that in situation where the restorative dentist is not sure as to whether to proceed, the Endodontist should be the first consult. The Endodontist should be part of the decision making process.

 

Dealing with Retreatment Obstacles

·         Crowns and Bridges

o        Webber has tried devices such as Morell, Richwil, Higa, Metalift System and WAMkey. But in MOST cases, he simply CUTS THE CROWN OFF.

·         Posts

o        Hemostats and Microsurgical forceps (expensive!)

o        Ultrasonics

o        Dedicated Post removal devices

§         Thomas PRS ( has Peezo type drills for going through fiber posts)

§         Gonon PRS

§         Ruddle PRS –

Webber prefers to try to ultrasonically vibrate the post and try to get it out that way. Always use copious water to prevent overheating of the post during vibration. If he can’t remove it ultrasonically in about 10-15 minutes, he moves on to a post removal system. It is rare that you can NOT remove a post with one of these PRS systems. You should always warn patients when post size or length /root size may risk fracture. In that case SRCT might be a better option.  He then showed the Ruddle PRS video.

·         Silver Cones

o        Microsurgical Forceps – ideal for when silver cone heads are sticking up in the chamber

o        Braided Hedstrom files

o        Ultrasonics  - work around the periphery for the cone with an ultrasonic file

Some cases are best managed by to bypass the silver cones with very small hand files and then using them to remove the cone with an outward motion.

·         Gutta Percha

o        Solvents

§         Webber is not a fan of solvents because of the sludge of softened GP it creates (Chloroform, Xylol, DMS IV).  If you do use solvents, you must remove all of it with a paper point wicking technique before you start re-preparing it.

o        ProTaper Universal D1, D2, D3 @ 500-700 rpm

§         In may of 2006 this new ProTaper Universal system was introduced ( except in the US)

§         D1 file: Removes Filling Material from the coronal third

·         11mm handle -  16 mm cutting surface

·         White ring for ID

·         9% taper matches average coronal diameter

·         ISO 30 active tip for easier penetration of obturating material

§         D2 file: Removes filling material from the middle third

·         11mm handle -  18 mm cutting surface

·         2 White rings for ID

·         8% taper matches average mid canal diameter

·         ISO 25 Non active rounded tip to follow canal path

§         D3 file: Removes filling material from the apical third

·         11mm handle -  22 mm cutting surface

·         3 White rings for ID

·         Reduced 7 % taper matches apical third diameter

·         ISO 20 non active rounded tip to follow canal path

o        Micro Debrider

§         These are small files that are constructed with 90 degree bends and are used to remove any remaining Gutta Percha on the sides of the canal walls/isthmuses after re-preparation.

Most literature shoes that we cannot remove all the previously placed filling material.

Wilcox et al JOE 1987 13 453-7 Endodontic Retreatment: Evaluation of gutta percha and sealer removal and canal reinstrumentation. Canal walls completely free of debris are not usually observed.

Imura et al Comparison of relative efficiencies of four hand and rotary instrumentation techniques during retreatment JOE 2000 33 361-66 Overall all instruments leave filling material inside the root canal

·         Carrier Based Systems- Thermafil

o        Rotate ProTaper F1 or F2 into the groove of the carrier @ 800 RPM

o        Rotate D1,D2,D3 into groove @ 700 RPM

o        Insert and retrieve with Hedstrom File

Thermafils are not as difficult to remove as some people may think.

·         Pastes

o        Soluble ZnO Pastes

o        Insoluble/Hard Pastes

o        Russian Red ( Resorcinol based pastes)

Paste removal can sometimes be extremely difficult.

 Cohen AG The efficiency of different solvents used in the retreatment of past e filled root canals ( Master’s Thesis) BU 1986  The most effective solvents for softening formaldehyde resin pastes were those that had potentially harmful effects.

Vranas et al JOE 2003 29:69 The effect of endodontic solutions on resorcinol-formalin paste Endosolve R appeared to become incorporated into the paste softening it without actually dissolving it.

Jeng and El Deeb JOE 1987 13 295 – Removal of hard paste fillings from the root canal by ultrasonic instrumentation

Dr Webber mentions DMS IV as well as Endosolv R (Septodont) as agents for paste removal as well as a myriad of ultrasonic tips. He has no favorite manufacturers and suggests that each of us has our favorite types and brands. Sometimes ( especially with Russian Red) we have to accept some compromises. Because the tooth structure is stained red it is often difficult to discern where the tooth is and perforations are easy to make when attempting to remove this material. We need good magnification and careful ultrasonic .

·         Broken Instruments

Webber says that we need to have a strategy to do this. We need to reevaluate the “magnificent obsession” of attempting to remove broken root canal instruments. He quoted UGH and Berg IEJ 1986 19:2-10  Endodontic treatment of root canals obstructed by foreign objects

His strategy:

o        In coronal third – attempt retrieval

o        In middle third – retrieve or bypass

o        In apical third – leave and observe

Do we need to remove all broken instruments? 
Crump and Natkin JADA 1970 88(3) 134  Relationship of broken root canal instruments to endodontic case diagnosis 53 cases of inadvertent breakage at apex compared to 53 controls. 2 year follow up as good as success from correctly filled canal.

Fox et al 1972 N NY State Dent Assoc 38 (3) 154 Filling Root Canals with Files
Instruments twisted off at apex and locked tightly in the canal served to prevent apical percolation

Therefore in situations where the instrument is broken at the apex, there must be some consideration made for filling to the level of the broken instrument and then monitoring the case.

Minimal requirements:

·         Microscope

·         Assistant should also be able to see (via auxiliary scope or monitor)

·         Webber likes the Satelec ultrasonic unit and uses various tips

He uses the Carr technique for modifying a GG bur with a disc, then creating a staging platform before using an ultrasonic tip to rotate around the file in a counterclockwise manner to dislodge it.  If you can’t see what you are doing – if you do not have the correct magnification- you should not be doing this.

The secret of removing the instruments broken in the coronal and middle thirds is understanding how much coronal tooth structure you have to remove in order to gain access to the instrument. If we must “over-prepare” the coronal portion to gain access, then maybe it is a better idea to leave the instrument in place rather than compromise the coronal dentin.

Cancellier devices and Krazy Glue can also be used. Sometimes it works, sometimes it doesn’t but you still must have several different strategies to allow you the option of selecting the best device for the situation. He showed Ruddle’s IRS System video. He said that while the video is impressive, it rarely works that easily. We all have a good laugh while watching how simply the system seems to retrieve the broken file – he comments that he wishes they all came out that easily.

·         Bypassing Broken Instruments

o        Bypass with K file #8/10

o        Continue bypass sequence

o        (Dislodge with Ultrasonic K file #15 or 20

o        Copious irrigation

He showed a lower molar with a large portion of broken file in the middle and apical third. The angle of retrieval was such that too much coronal dentin would have to be removed to allow straight line access to the coronal part of the file. So he chooses a bypass strategy in this case. The canal was prepared well enough to incorporate the file into the prepared canal space. He shows another case that cannot be retrieved or bypassed. He remarks that breaking a file is not negligent, but NOT telling the patient is negligence.

Saunders et al 2004 JOE 30(3) 177-179  Effect of separated instrument on bacterial penetration of obturated root canals The presence of 3mm of a  fractured 40/.04 instrument did not speed up or slowdown penetration of bacteria compared to controls. Extruded sealer onto flutes equivalent of any other obturation technique. In the absence of residual infection coronal seal was the most important factor. 
In other words, in the absence of a periradicular lesion, (i.e./ a suspected vital case) we should consider leaving the instrument in place, IF we can do a good job with the rest of  the canal system AND we can get a good coronal seal as well. We need to reconsider the obsession with instrument removal at the expense of good tooth structure and risk of procedural or structural compromise.

·         Perforations

o        MTA is the material of choice ( Tulsa or Angelus<- faster set than Tulsa)

o        All the armamentarium associated with it is necessary – i.e./ Dovgan carriers and Pluggers, Lee Block and instrument

o        Webber has had success with the MAP system ( Produit Dentaire) now being sold by Dentsply as the MTA Gun.

 

·         Apical Closure and Perforation Repair

Webber showed a case where the patient insisted that the anterior tooth be saved. Very large resorbed apex with LEO.  An MTA plug was placed and the case re-restored. He then showed two perforation cases (furca and lateral). We must ensure that the perf repair material is up against bone because it washes out of exposed to the oral environment.



 

 

Webber says that that retreatment is hard but that we need to take an optimistic view when approaching cases. (Tanaka’s Law – 1. Nothing is as hard as it looks 2. Everything is more rewarding than it seems. 3. Everything will go right and at the best possible moment)
 

Single Visit Retreatments:

Webber usually does SINGLE VISIT RETREATMENT. The only indication for non-completion of retreatment in a single visit is when he is unable to get the canal dry.  In that case he will fill the other canals and then treat the wet canal with CaOH.  Note: He is the first of several “one steppers” who will present at the Summit.  Fred Barnett, take note.


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