Nial Balloch looks into how to deal with calcified root canals.
With an increasingly aging population, and one which is remaining dentate, the endodontic implications of sclerosis is one that we are perhaps more exposed to now, more than ever.
Sclerosis of the pulp is a natural process and happens due to both pathological and physiological causes. Secondary and tertiary dentine are deposited over time, thus reducing the viable pulp space as we age. Secondary dentine is deposited once apexification has occurred and continues throughout our lifetime. Tertiary dentine (reactionary/reparative dentine) is deposited in response to trauma to the pulp, this can be in the form of caries, bruxism, fractures, physical trauma or even tooth preparation. The process of tertiary dentine deposition is described quite eloquently by Trowbridge who describes the process as dentines response to shield the ‘king pulp’ during invasion attempts by bacteria (Trowbridge and Emling, 1997).
Fortunately advances in knowledge and especially endodontic armamentaria means that the management of calcified root canals can be more predictable, thus allowing resolution and restoration of teeth that perhaps would previously have been extracted, despite potentially being functional and restoratively sound (Hargreaves and Berman, 2016). In an age where patients have a greater expectation regarding retaining their own teeth it’s important to be aware of how best to manage these cases.
The most common way in which calcified canals will first be identified is from the pre-op radiograph (or radiographs in the case of multi-rooted teeth). From there on the management of calcified canals follows the same basic principles that all endodontic cases do:
- Chemo-mechanical disinfection.
Studies have highlighted the importance of magnification in location of canals, Scharwze et al (2002) demonstrated the benefit of magnification in locating MB2s in first molars, canals that are traditionally difficult to locate.
It therefore goes without saying that in teeth showing sclerosis and calcified canals that magnification, whether in the form of dental loupes (Figure 3) or an operating microscope (Figure 4), is of paramount importance in terms of managing these cases. These aid in providing visualisation and illumination into a small working area, and help to highlight landmarks in the pulp chamber that can aid in location and management of calcified canals.
Pre-operative radiograph assessment is essential in cases with sclerosis. For teeth with more than one canal it is therefore recommended to have more than one pre-op radiograph at different angulations. These should be studied to help gauge the depth from the crown to the pulp chamber, or in cases where the sclerosis is deep into the root, the depth to the beginning of the canal. Many digital radiograph systems will have built in software that can be used to measure these depths as a rough guideline.
Within teeth with calcification of the pulp chamber, the aim of access is the same as in ‘normal’ endodontics – allowing unimpeded access into the pulp chamber and the root canal system with as minimal destruction to sound tooth tissue, thus allowing restoration post endodontic work. The issue with cases with severe calcification of the pulp chamber is that access is more to do with location of the canal orifices, rather than locating the pulp chamber as this is non-existent. This unfortunately generally leads to more tooth structure being removed than desired in pursuit of the canal system. This can have dramatic consequences in the form of perforations or removal of too much tooth structure, thus rendering the tooth unrestorable.
Fortunately, there are some ways and equipment available that help us in our locations of the root canals. As stated previously, the sclerosis process is down to the deposition of secondary and tertiary dentine over the root canals, this fact allows us to use the differences in dentine types to help locate the root canals. Krasner and Rankow (2004) describe several laws which aid in location of root canals, all of which are excellent rules to use as a guide in orifice location.
One of these rules is that the colour of the pulp chamber is always darker than the walls of tooth. Under magnification and illumination these subtle changes in dentine colour can be noted. When in the pulp chamber and troughing for canals, ensure that it is dry and it can be noted that in use a bur or ultrasonic will remove ‘whitish chips’ which end up accumulating in one specific location – this often being a canal orifice. Therefore, against the backdrop of the dark dentine of the pulp chamber floor, canal orifices can often appear as little white spots (Thomas et al, 2014). The use of magnification is pivotal here to see the slight changes in dentine colour.
Personally, I find the use of ultrasonics and gooseneck burs (Figures 6 and 7) key pieces of equipment to use in such cases. These both allow careful, selective, controlled removal of dentine. The use of an endodontic DG16 (Dentsply Sirona) probe or micro-orifice openers are also routinely used to aid initial penetration and exploration of these ‘white spots’.
In multi-rooted teeth use of dyes can also be beneficial in terms of locating canal orifices. An example of this is Cerkameds ‘Canal Detector’, which works by having a dye contained in the product which invades into the root canal orifices and dyes them blue, thus enabling easier detection. The product can also be used in the same manner to detect cracks within teeth.
Once any calcified canals are identified, negotiation of them presents another challenge. As with all endodontic cases the use of both stainless steel (SS) hand files and nickel titanium files (rotary and/or reciprocating) are the mainstays of treatment.
The small hand files are important in creating a ‘glide path.’ This is effectively an initial preparation of the root canal structure from orifice to apex, which precede rotary/reciprocating files (Cassim and Van der Vyver, 2013).
Benefits of glide path creation include:
- Scouting of canal structure
- Initial introduction of irrigant
- Lubricates canal before introducing bigger files.
The use of pre-curved smaller hand files such as .06 and .08 is often the first step in initial exploration of calcified canals. In canals that are extremely calcified or curved, traditional stainless steel K files can struggle to negotiate the canal system and often unwind, twist and thus run the risk of fracturing. Dentsply’s (Dentsply Sirona Endodontics) C-Pilot files are often a good alternative in such cases. These files are made from a special steel alloy with a uniform structure, which offers maximum resistance to fracture, but with no limitations with flexibility. The files have an inactive tip, which allows the instrument to follow the canal rather than cutting its own pathway, thus decreasing the risk of perforation of the root canal system.
In all cases it is imperative to achieve a reproducible glide path before thinking of introducing any mechanically driven file.
Mechanically driven glide path
To aid in glide path production, there are a number of files on the market these days whose aim is to assist in initial preparation of canals by aiming to create/enhance glide paths. These nickel titanium files are designed to do the job that stainless steel hand files can do, but more efficiently and safely. Traditional stainless steel files have the disadvantage in that if not managed properly they can end up creating their own pathway within the root canal system (transportation) and thus run the risk of perforating or blocking the canal, due to lack of flexibility of the file.
With their improved metallurgy and engineering, nickel titanium endodontic files with small tapers and apical tips have been shown to follow natural canal curvatures better than hand stainless steel files (Patino, Biedma and Liebana, 2005; (West, 2011).
Examples of such files include: Proglider, Pathfiles and Waveone Gold glider.
Improved nickel titanium files for main preparation
Newer generations of nickel titanium alloys such as Waveone Gold, Protaper Gold, Reciproc Blue are thermomechanically treated nickel titanium alloys. The process of manufacture allows the files to be more flexible with improved cyclic fatigue resistance and greater angle of deflection at failure when compared to conventional nickel titanium and therefore offer many advantages when looking to negotiate calcified canals (Zupanc, Vahdat-Pajouh and Schafer, 2018).
Certain files, due to the heat-treated process in how they are manufactured, can also be pre-bent thus giving another advantage in terms of negotiating tight canals.
Chemo-mechanical preparation remains arguably the most important aspect of root canal treatment in terms of trying to disinfect the root canal system. With calcified canals, its especially important to never try to instrument in dry canals, to limit the chance of file separation, creating blockages etc.
Irrigants remain the most popular way of providing lubrication within the root canals and of all the irrigants available, sodium hypochlorite (NaOCl) is the most commonly used as it meets most of the requirements for an endodontic irrigant compared to every other compound (Zehnder, 2006). It has the ability to dissolve necrotic tissue and the organic components of the smear layer and it has a broad antimicrobial spectrum. Seventeen per cent EDTA can also be used to aid in removal of smear layer. If used, it’s important not to mix NaOCl and EDTA.
Rather than irrigation, EDTA in the form of a lubricant gel (such as Glyde, File-eze, Canal+ etc) can be used as an adjunct to irrigation to aid the passage of files.
Time – time is imperative in these cases, especially as you go deeper into the tooth in search of an opening. Make sure you have plenty of time for the appointment as rushing to locate canals in areas where there is minimal leeway for error, will ultimately lead to error.
Tiredness and limitations – if you find yourself searching and searching, there is no shame in dressing the tooth and coming back to it another day. The best weapon in our armamentaria for locating root canals are our eyes, and like all muscles if used a lot are prone to fatigue. I have countless anecdotal evidence in cases where I haven’t been able to find all canals by the end of a long appointment and yet I’m able to locate them within minutes of a second appointment.
Stop and continually reassess – if you are going deeper and deeper into a root canal system looking for an opening, it is worthwhile stopping and re-assessing at regular intervals. It is common to become fixated on one spot within the tooth and continually work there until you’ve located the canal or perforated. I advocate stopping every so often and re-assessing with radiographs to make sure you aren’t going off-course. In these difficult cases CBCT is incredibly useful to aid location, if you have access to one.
Limitations – even with all the advice, there will be some cases where you may have to stop mid-treatment and admit defeat. There is no shame in stopping if you’re having difficulty and then referring on to someone better equipped. It’s much better to realise your limitations and refer on before you potentially create other problems eg worsening a ledge, creating an apical block or perforating.
A new patient attended practice after seeing an emergency dentist due to a veneer debonding. The veneer was replaced temporarily and the patient was advised to see a dentist.
The patient was 58 years old, medical history was unremarkable but, they hadn’t seen a GDP for over six years. Her primary concern was her debonded veneer and their overall aesthetics (which had been present for over 10 years), but was aware that would likely need a lot of dental work.
She was seen by a colleague who recorded that gingival health was fair, the dentition was heavily restored with a number of leaking restorations, with all upper anterior veneers except LR3 showing gross secondary decay. Periapical radiographs of teeth UR1 and UL1 showed severe sclerosis of the root canal system. Due to the decay present and lack of sound coronal tooth structure, the canal space of UR1 and UL1 were required for restoration with post crowns.
A treatment plan was devised as follows:
- Course of hygiene phase therapy
- Management of posterior leaking/fractured restorations
- Temporisation of UR2-UL3 with temporary crowns following caries removal.
- Root canal treatments UR1, UL1 and UL3
- Crown lengthening to improve gingival zeniths UR3-UL3
- New temporary crowns UR3-UL3
- Review perio condition
- Finalised anterior crowns.
Root canal treatments UL1 and UR1 procedure
Following placement of temporary crowns UR1 and UL1 by a colleague, the patient was referred to myself for the endodontic management of the sclerosed canals. The patient was informed of the increased risks of root canal treatment in this situation and a full consent process was followed in relation to this.
Initial assessment was done before seeing the patient by using measuring tools on our digital radiograph system with the original radiograph, as described previously, to give an estimation regarding canal location in relation to the crown of the tooth.
Local anaesthetic was administered and dental dam was placed and secured by floss ligatures. Access was made palatally through the temporary crowns and the use of ultrasonics and predominantly LN gooseneck burs was used to aid location of the canal with use of a Leica Dental Operating microscope. Initial location was difficult due to the degree of sclerosis plus the challenge to keep access as minimal as possible to allow restoration post endodontic treatment. As previously described, in difficult cases I find it useful to use radiographs mid-treatment to aid in location of the canals.
Following preparation of canals the appointment time was complete and so they were dressed and the access resealed. At the second visit, two weeks later, the patient reported no symptoms and thus obturation was complete and fibre posts placed to allow definitive restoration in the future.
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Cassim I and Van der Vyver PJ (2013) The importance of glide path preparation in endodontics: a consideration of instruments and literature. SADJ Vol 68, no 7
Hargreaves KM and Berman LH (2016) Cohen’s Pathways Of The Pulp. 11th edition. Elsevier
Krasner K and Rankow HJ (2004) Anatomy of The Pulp Chamber Floor. Journal of Endo. Vol 30, No1
Patino PV, Biedma BM and Liebana CR (2005) The influence of a manual glide path on the separation rate of NiTi rotary instruments. J Endod 31: 114-6
Schwarze T, Baethge C, Stecher T and Geurtsen W (2002) Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope. Aust Endod J. 28: 57-60
Thomas B, Chandak M, Patidar A, Deosarkar B and Kothari H (2014) Calcified Canals – A Review. Journal of Dental and Medical Studies Vol 13 Issue 5
Trowbridge HO and Emling, RC (1997) Inflammation: A Review Of The Process. Fifth Edition. Quintessence Publishing Comp. Inc
West J (2011) Manual versus mechanical endodontic glide path. Dent Today. 30:136-40
Zehnder M (2006) Root Canal Irrigants. J Endod 32: 389-98
Zupanc J, Vahdat-Pajouh N and Schafer E (2018) New thermomechanically treated NiTi alloys – a review. IEJ. Vol 51, issue 10