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| Benefits of a Seiler Microscope in Endodontic Applications: |
| 1. |
Allows surgeon to minimize the size of the surgical site, reducing patient discomfort and healing time. |
| 2. |
Improves accuracy of microsurgical incisions and suturing with 6-0 through 8-0 sutures, permitting precise tissue/tissue and tissue/tooth approximation for primary would healing. |
| 3. |
Improved lighting and magnification aid in locating additional canals. |
| 4. |
Aids in retreatment of broken instruments. |
| 5. |
Improves ability to thoroughly clean prepared canals. |
| 6. |
Accurate depth of retro-prep extension can be more easily assessed. |
| 7. |
Permits micro-level osseous surgery facilitating bone removal without nicking the root surface and allows for better periodontal ligament preservation during ostectomy. |
| 8. |
Permits accurate and easier root amputations and hemisection. |
| 9. |
Improves detection and evaluation of root fractures and abnormalities. |
| 10. |
Provides upright working conditions, alleviating occupational neck, back and shoulder problems. |
| 11. |
Provides high-resolution video and 35mm photography for patient education, enhanced training,legal documentation. |
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| Crown and Bridge procedures using a microscope |
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Patient presents following failed attempt at root treating mandibular right second permanent molar. The referring dentist had difficulties establishing working length. [Note also the lack of rubber dam clamp.] |
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| Access to the pulp chamber shows weak obturation with gutta percha. |
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Careful removal of gutta percha with protaper instruments reveals C-Shaped canal. Protaper instruments are used at maximum torque and 1000 rpm for removal of coronal gutta percha. Gutta percha located closer to apex is removed with k-Flex files utilising watch winding and balanced forces technique to develop a glide path for rotary instruments.
The avoidance of solvents allows the maintenance of a uncontaminated operating field. |
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| Further refinement of the coronal portion of the canals clearly show the C-Shaped morphology of root canal with three separate exits. |
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Following establishment of a glide path with stainless steel hand files [minimum ISO 20]: Protaper rotary instruments used at maximum torque but at only 150 rpm. The rotary instruments are taken to within 1mm of the canal apex [working length].
The working length is established using a combination of paper points, an electronic apex locator, radiographs, and from tactile feedback of the apical constriction if present.
Apical refinement is carried out using GT hand files. |
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The apical portion of the root canals are obturated using gutta percha and AH+ resin sealer utilising continuous wave condensation technique (System B).
The coronal portions are backfilled with gutta condensors. |
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The canal orifices and floor of the pulp chamber are sealed with white MTA. |
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The pulp chamber space is sealed with pink glass ionomer (Fuji VII). |
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The tooth is restored to function with a composite core. This will be the foundation for the cuspal coverage indirect restoration. |
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The post operative radiograph. |
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| Failed RCT LR6 |
There is apical pathology associated with the inadequate endodontic treatment in the LR6. The mesial canals are obturated short of the working length.
The patient is to undergo orthodontic treatment. It was decided to attempt initially to revise the existing root canal treatment rather than extract LR6, followed by space closure and uprighting of the LR8.
Notice how thin the intraradicular dentine is. |
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The crown is removed intact with a pneumatic crown remover.
Access is made through the existing glass ionomer core to the root canal material. Care is taken not to disturb the remaining natural morphology of the pulp walls.
The access cavity is disinfected for one minute with hypochlorous acid to reduce the bacterial load [Sterilox |
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The core material is broken down with ultrasound.
Under high magnification, diamond coated restorative ultrasonic tips are used. This allows for precise removal of core material only. This avoids damage and unnecessary removal of further dentine from the already thin floor of the pulp chamber.
Perforation of the floor of the pulp chamber will reduce prognosis |
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The existing root canal material [gutta percha] is removed with a combination of rotary instruments and heat.
Rotary instruments are taken to within 2mm of the apical extent of the exiting root canal. Taking rotary instruments closer than this may compound any existing deviation in the previous attempt at preparing the root canal.
When obturation is seen to be well short of the ideal working length, consideration should be given to the presence of ledges.
This is the view of the mesio-lingual root canal. |
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The last 2mm of gutta percha is removed with NiTi micro-openers and micro-debriders [Maillefer].
The blind use of hand instruments will exacerbate the ledge and make its successful navigation improbable. In such situations the very highest powers of magnification [X24] afforded by the microscope become invaluable. Any small pieces of gutta percha remaining can be removed with a solvent.
A - Ledge with remaining gutta percha
B - Root canal proper. Notice its deviation towards the buccal. |
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The ledge in the mesio-lingual root canal has been navigated successfully. Safe access has been established to the remaining root canal morphology.
Prior to further canal preparation, it is important to consider removal of the ledge. Failure to do this may result in further procedural errors. The easiest and most successful manner in which to do this is with NiTi hand GT files [Dentsply]
A - Ledge incorporated into canal preparation
B - Root canal proper. |
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Following complete disinfection of the entire root canal space; the root canals are obturated.
The dentine pin is removed and the root canals are sealed with MTA. A new provisional core is placed and the original crown is recemented. Following orthodontic treatment this will be replaced.
Notice that the remaining dentine thickness in the floor of the pulp is identical to that prior to treatment. |
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| Carious LR7 The LR7 is carious |
The signs and symptoms indicate an irreversible pulpitis.
The caries is removed and the tooth is provisionally restored with a glass ionomer core. This is to prevent the ingress of salivary bacteria during the endodontic treatment.
The prognosis for endodontic treatment in the presence of caries at the time of root filling is reduced. It is important to remove all the caries before starting any endodontic treatments. |
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Access is made through the GIC core to the pulp space. The pulp chamber was disinfected with hot 5% NaOCl for one minute to reduce the bacterial load.
Two canals are identified: A C-shaped dito-lingual canal extending mesially, and a conventional disto-buccal canal.
To facilitate vision: The canals are debrided of necrotic pulp tissue with micro-debriders [Maillefer].
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The dentine roof of the mesiobuccal pulp horn can be seen clearly at high magnification. With the excellent illumination and magnification afforded by the microscope it is possible to precisely remove dentine.
The dentine is removed with a combination of small long-shanked burs and ultrasonic tips [EMS RT1].
Failure to enlarge or eliminate the pulp horn and its necrotic contents, may result in insufficient penetration of disinfecting solutions. This will compromise the prognosis for the endodontic treatment. |
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Judicious removal of the roof of the pulp horn reveals an further canal.
Without the microscope the chances of being able to identify such anomalous anatomy is slim.
It is important to resist the temptation to rush towards the apex. Time spent identifying canals and refining the access cavity outline now will facilitate instrumentation and obturation later.
Furthermore it allows time for good penetration the of disinfecting solutions into the coronal and middle thirds of the root canal system. Together with the pulp space, these are the most heavily contaminated portions. |
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| The careful shaping of the mesio-buccal pulp horn without spoiling the walls and floor of the pulp chamber has enabled another canal orifice to be located! Injudicious use of instruments can damage the natural anatomy of the floor of the pulp chamber. This makes orifice location far more demanding - even with a microscope. Even if the first mesio-buccal canal had been located without a microscope; it would have been highly unlikely that this second canal could have been found. The canal is gently enlarged with micro-openers and micro-debriders. |
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Whilst it might be appealing to attempt to navigate such complex root canals with NiTi instruments: This temptation must be avoided.
The first step is to provide a glide path for the rotary instruments. The instrument of choice is a K-type, stainless steel file. Stainless steel files are more resistant to sudden catastrophic failure than rotary NiTi instruments.
Stainless steel will undergo plastic deformation prior to breaking. This can be seen clinically by examining the file carefully for elongation of the flutes. Such checks should be made before introducing a file into a canal.
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The working length [WL] is established using a combination of paper points, an electronic apex locator, radiographs, and from tactile feedback of the apical constriction if present.
In order to avoid confusion only two files were introduced for the working length radiograph. These were in the MB1 and DB canals. This prevents uncertainty when files are superimposed radiographically. The other canal WL are determined from the aforementioned techniques.
Notice the superior seal obtained distally by the GIC provisional core. |
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Following the completion of the shaping and cleaning, the final morphology of the root canal system can be visualised clealry with the microscope.
There is a distinct disto-buccal canal. The lingual canal is C-shaped extending from the disto-lingual towards the centre of the root mass. The exploration to confirm the absence of a genuine separate mesio-liniugal canal can also be seen.
Due to access, unfortunately it was not possible to simultaneously photograph both mesial canals within this image, without radically enlarging the access cavity to improve visibility. This would structurally weaken the tooth. For the sake of a photograph this was not considered clinically justifiable. |
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Interpretation of the post-operative radiograph requires some appreciation of the root canal morphology negotiated.
MB1 can be clearly identified as the most mesial canal. Just to left of this is the MB2. Distally the MB2 silhouette is superimposed by the mass of the C-shaped lingual canal. The distal canal can only be identified in its apical extent as it curves distally. This can be confirmed by the working length radiograph.
It is unlikely that this tooth could have been successfully treated without the use of a dental operating microscope |
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| Broken NiTi File LR7 |
There is a broken NiTi rotary file in the distal root canal of LR7.
It can be seen how the root canal deviates mesially in the middle third. It is possible that this sharp curve has resulted in flexural fatigue and failure of the instrument.
However torsional failure occurs more frequently than flexural fatigue. Applying too much apical pressure to a NiTi rotary instrument increases the likelihood of torsional failure.
It is important to establish a glide path with stainless steel files prior to using any rotary NiTi inside a root canal [minimum ISO20]. Furthermore, rotary NiTi instruments should be allowed to cut dentine with minimal loading. Excessive pushing on the instrument will increase the chance of file separation and should always be avoided. Copious use of a disinfecting irrigant will also reduce instrument loading. |
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If the broken instrument cannot be bypassed it becomes necessary to remove it in order to gain access to the remaining root canal system.
Under high power, provided that the fractured instrument is not beyond a bend in the root canal, it is possible to assess its size, shape, position and its degree of freedom within the root canal. This assessment is best made at X16 magnification and by contacting the most coronal portion of the instrument using a DG16 endodontic explorer.
The broken instrument can be clearly seen in the distal root canal of the LR7. |
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The core material is broken down with ultrasound.
Under high magnification, diamond coated restorative ultrasonic tips are used. This allows for precise removal of core material only. This avoids damage and unnecessary removal of further dentine from the already thin floor of the pulp chamber.
Perforation of the floor of the pulp chamber will reduce prognosis |
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In this case a "modified" Gates Glidden was used to create a circumferential "staging platform" above the instrument. Ultrasonic energy is then used to trephine around the instrument exposing 1/3 to 1/2 its length.
In this example an RT3 ultrasonic tip [EMS] was used with a delicate, anticlockwise stroking motion, to release and eject the broken instrument. It is tempting to use high power settings to dislodge broken instruments. However, high power ultrasonic energy can cause the instrument to partially disintegrate.
It is more productive to begin with a lower power setting and gradually increase this towards medium power. In this manner ultrasonic energy is used to excite the instrument, encouraging its ejection from the root canal, rather than causing its break-up. |
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In general, the removal of broken instruments sacrifices radicular dentine. It is important to be aware of the remaining dentine thickness and root canal anatomy at the level of the fractured instrument. This assessment is best made from a radiograph. Whilst attempting to retrieve a broken instrument, it critical to avoid root perforation or over-enthusiastic canal enlargement These will compromise the prognosis.
During the creation of "staging platforms" for instrument removal, it is also easy to create a ledge. Such defects in canal shape should be refined where possible. This allows for the smooth passage of instruments beyond this position and will later facilitate 3D-obturation of the root canal system.
In this case a ledge was created distally by the "modified" gates glidden drill. Refinement of the canal shape and re-establishment of a smooth glide path was carried out with GT Hand files [Dentsply] |
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Following the removal of the broken instrument: The entire root canal system is further shaped and disinfected in a conventional manner. The root canals can then be dried and obturated.
The root canal orifices are sealed with mineral trioxide aggregate and the core material is placed.
Notice the wine-glass silhouette in the middle third of the distal root canal. This is the position of the staging platform and dentine trephining. A common outcome of broken instrument retrieval is alteration of the root canal form.
Adopting correct technique and a safe discard strategy are still the best solutions for avoiding instrument failure. Should an instrument break however, then the use of a microscope in combination with ultrasonic energy can make its retrieval much easier and less stressful. |
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Following complete disinfection of the entire root canal space; the root canals are obturated.
The dentine pin is removed and the root canals are sealed with MTA. A new provisional core is placed and the original crown is recemented. Following orthodontic treatment this will be replaced.
Notice that the remaining dentine thickness in the floor of the pulp is identical to that prior to treatment. |
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| Failed RCT UR6 |
The existing RCT in UR6 is symptomatic. The tooth is tender to percussion and the buccal sulcus overlying the mesiobuccal root is tender to palpation.
Radiographically the mesiobuccal canal is inadequately obturated and there is a screw-type post in the palatal canal. The material utilised for the core is either very radiolucent, or a core does not exist.
It was decided to provide an orthograde revision of the existing endodontic treatment. |
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The crown was removed with a pneumatic crown remover and the post unscrewed without complication. No core material was present. The entire pulp chamber was filled with zinc phosphate cement. This was removed with ultrasonic instruments taking care not to damage the pulp chamber walls.
The pulp chamber is disinfected for one minute with hypochlorous acid to reduce the bacterial load [Sterilox]. Any secondary caries is removed with a combination of rotary and hand instruments. The pulp chamber is repeatedly disinfected during caries removal. |
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The coronal gutta percha is removed with a combination of heat, gates glidden drills and ProTaper rotary instruments. New glide paths are established with stainless files.
With the microscope a ledge of dentine can be seen to run from the mesio-buccal canal [MB1] towards the palatal canal. It is beneath this ledge that the second mesio-buccal canal [MB2] is located.
It is important not to destroy any anatomical landmarks when attempting to locate MB2. The floor of the pulp chamber provides guidance as to the location of the canal orifices. Careless use of a bur or ultrasonics will destroy such landmarks and make location of canals more difficult. The ledge or isthmus should investigated with a sharp DG16 explorer or micro-dedrider [Maillefer]. |
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Gently picking away at the ledge will eventually reveal and allow access to the first few millimetres of the MB2 canal.
It is important to realise that MB2 is only rarely located on a diagonal line from MB1 to the palatal canal. It is true that MB2 is palatal to MB1: However its position is most commonly found by locating it on an imaginary line that runs parallel to the mesial marginal ridge.
The location of a sclerosed MB2, such as those found in older teeth, can sometimes be difficult even with the use of a microscope. Tell tale signs of its location include bubbling around its orifice when using warm 5% NaOCl as the disinfecting solution.
With over 80% of maxillary first molars having two mesio-buccal root canals: It is important to assume there are always two canals: Unless careful examination reveals otherwise. |
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Instrumentation of MB2 is frequently much harder than MB1. Often the canal orifice is hidden beneath a calcified shelf and is of a smaller diameter and more sclerosed. Initial access is gained from a more distal approach than that for MB1 allowing for the safe removal of the calcified "roof" of dentine
To reduce the stresses on instruments it is important to refine the access cavity outline and canal orifice to facilitate straight line access to the coronal third of the root canal. In the majority of cases, the access cavity should be made more rhomboid in outline to assist in the palatal approach required for shaping of the canal.
Once access has been made to the middle third, instrumentation tends to revert to a more conventional approach along the long axis of the tooth. |
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The root canals are disinfected and shaped in a conventional manner.
For endodontic revision the author favours further disinfection of the root canal system with a 2% IKI solution for 5 minutes prior to obturation.
The root canal orifices are sealed with mineral trioxide aggregate and a core placed. In this instance a provisional acrylic crown was fitted during the healing period. In the absence of further signs and symptoms this will be replaced with a definitive restoration.
From the radiograph it can be seen that the two mesial canals share the same apical foramina [Type II]. |
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The working length [WL] is established using a combination of paper points, an electronic apex locator, radiographs, and from tactile feedback of the apical constriction if present.
In order to avoid confusion only two files were introduced for the working length radiograph. These were in the MB1 and DB canals. This prevents uncertainty when files are superimposed radiographically. The other canal WL are determined from the aforementioned techniques.
Notice the superior seal obtained distally by the GIC provisional core. |
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| Pulp Biopsy |
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The plastic restoration in the UL6 has failed. There is evidence of secondary caries undermining the enamel of the remaining mesiopalatal and distobuccal cusps. Cracks are also present within the enamel.
Flexidam [Coltene Whaledent] is applied and sealed with dental tape |
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The existing amalgam restoration is removed and an assessment of the cavity is made. There is gross caries together with evidence of a previous lining in the deeper portions of the cavity.
The cavity is disinfected with 5% NaOCl for one minute. This is to the reduce bacterial load prior to caries removal proper. |
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The more heavily contaminated peripheral caries is removed. The precision of both hand and rotary instruments is improved under the microscope.
The cavity is periodically disinfected with 5% NaOCl to reduce the numbers of viable bacteria. Bur changes are made to avoid contamination of the deeper portions of the cavity with infected dentine.
A better assessment of the lining is now possible. It is felt that the lining covers a previous exposure. |
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With removal of the caries under X10 magnification the cavity is assessed. As anticipated the lining had been placed over the site of a previous exposure.
Note that the colour of the dentine does not reflect its state of demineralisation or infectivity.
Under the microscope: Tactile feedback through instruments is still required to assess the degree of demineralisation of the dentine. |
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Under highest power a microexposure is revealed on the distoaxial wall of the cavity. There appears to be some limited blood supply to the fibrotic pulp associated with the distobuccal pulp horn. Coronal to this there are heavy tertiary dentine deposits [darker orange].
The distopalatal pulp horn is entirely occluded with tertiary dentine. |
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Following further disinfection with 5% NaOCL for one minute, with a sterile bur access is made to the pulp space.
The limited viability of the distobuccal pulp horn can be observed by the limited haemorrhaging from the pulpal tissues. The pulp occupying the palatal root canal is entirely avascular.
Without this level of magnification it is not possible to record the pulpal status. Clinical observation with the microscope dictate that this tooth undergo endodontic therapy. |
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With the diagnosis of a non-viable dentinopulpal complex, in preference to an unsuccessful pulp capping procedure, the UL6 is endodontically treated.
Note the presence of two mesiobuccal root canals with two distinct portals of exit. |
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