issn 2193-4673 • Vol. 16 • Issue 4/2020 roots international magazine of endodontics 4/20 research Reducing microleakage with lasers technique The advantage of using a dedicated carrier to place MTA trends & applications Calcified canals: A new approach

editorial | Adj. Prof. Philippe Sleiman Guest editor Daily clinical challenges Endodontics is the art and science of daily chal- lenges, expecting the unexpected, having eyes at the tips of your fingers and employing all your senses. First and foremost, we must not forget that we hold medical degrees, and indeed, endodontics can sometimes be very demanding when dealing with patients with special medical histories or some illness or even contagious virus, and we need to fulfil our paths. patient and to the referring dentist the best options for treatment. Sometimes, it may be considered a waste of your clinical time, but use it as an opportunity to have a break to check on your family and chat with your staff over a warm coffee. If microsurgery is needed to remove a cyst, better sooner rather than later. One of the ma- jor causes of burn-out in dentistry is not delivering what we wish for. Travelling to the office, looking at the day’s schedule and not knowing what challenges lie ahead, it is essential to foster a good mood and to spread it to your team in order to have a calm and smooth day, putting all your worries aside. Accepting the diagnosis as it is and trying to replace nature is something that we never have to do or prom- ise. If the tooth needs root canal therapy or does not, we need to say so. If the tooth is cracked or compro- mised, we need to accept it and try to explain to our We cannot be in control of everything; mother nature and our body have the upper hand. It is not a reversible treatment that we are doing, and room for error is almost non-existent. This is something that demands great mental preparation in order to keep calm and give the best that we can for our patients—after all, we are performing the most complicated treatment in dentistry; we are doing endodontics. Adj. Prof. Philippe Sleiman Guest editor roots 4 2020 03

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research | nal walls. The size of the Resilon master cones was then determined. An appropriate amount of the dual- polymerising Resilon sealer (SybronEndo; 4 ml) from the automix syringe was expressed on to a slab. The canals were coated with the sealer using the automix syringe, pre-measured Resilon master cones and a file. The vis- cosity of the sealer was modified by adding a drop or two of RealSeal thinning resin (SybronEndo, ref. No. 972- 2006). Subsequent accessory points of Resilon core ma- terial were also coated with the sealer and inserted into the canal and compacted through lateral condensation. Once the obturation was completed, the coronal surface was light-polymerised for 40 seconds. The coronal por- tions of all samples were then restored. Acid etching was done using a 35 % orthophosphoric acid-etch gel for 15 seconds. After acid etching, all cavities were coated with a layer of primer (Syntac Primer, Ivoclar Vivadent), adhesive (Syntac Adhesive, Ivoclar Vivadent) and bonding agent (Heliobond, Ivoclar Vivadent) and light-polymerised (Translux, Kulzer) for 20 seconds. Then a composite (Ivoclar Vivadent; Shade A3) was used in in- crements to seal the coronal 2 mm of the roots and was light-polymerised for 40 seconds. For the dye penetra- tion test, the samples were first coated with two layers of nail polish (Sally Hansen, Del Laboratories), except for the last apical 2 mm, which was left exposed so that the dye could only penetrate the canal via the apical region. The samples of each group were then kept in separate containers of distilled water and incubated at 37 °C for five days, to stimulate clinical conditions. After incubation, the samples of each group, again in sep- arate containers, were immersed in an aqueous solution of 2% methylene blue at 37 °C for seven days so that the root canals would be filled with dye solution by capillary action. After this time, the teeth were removed from the dye and rinsed under running water for 5 minutes and incubated again in distilled water at 37 °C for 24 hours. After incubation, the teeth were removed from the dye- containing solution, rinsed and dried. The samples were dehydrated in a sequence of alcohol solutions (70 % for 24 hours, 96 % for 24 hours and 100 % for 48 hours). Then they were kept in a histological cleaning agent (Histo- Clear II, National Diagnostics) for 2 hours and embedded in resin (K Plast) in groups in separate containers and stored in a water bath for four to seven days until the resin had set. The glass containers were broken to remove the resin-embedded samples, and Vaseline was applied into a self-made former container for each sample, to avoid sticking of acrylic to the container. Dye leakage was assessed after immersion in methy- lene blue, by examining vertical and horizontal sections under a transmitted-light microscope (Leica DMRX with an integrated Hitachi HV-C20A camera, Leica Microsys- tems) at an objective lens magnification of 0.63 x (optical lens magnification of 10 x) by means of a computer pro- gramme (Diskus, Hilgers Technisches Büro). Then hori- zontal cuts of 500 µm in thickness were made, splitting the roots into three portions: coronal third, middle third and apical third. The horizontal sections were examined under the transmitted-light microscope at an objective lens magnification of 2 x (optical lens magnification of 10 x) by means of the same computer programme, to as- sess dye penetration, and the data was saved. It is nec- essary to note that the digital camera, which connects the microscope to the PC and software, will magnify the image, but the power of magnification is not easy to cal- culate. Therefore, the final magnification of the image that is shown on screen or printed out depends on the size of screen. That is why we only report objective lens and optical lens magnification in such cases. Data analysis was performed using StatView software (SAS Institute Inc.), and the extent of leakage in each group was investigated in both vertical and horizontal cuts to gain a near 3D view. The scores were statisti- cally evaluated by three calibrated examiners using the Kruskal–Wallis test to determine the statistical differ- ences among the groups (p < 0.05), and comparison of paired groups was done using the Wilcoxon signed rank 708.86 683.75 Group 6 Group 5 Group 4 Group 3 Group 2 Group 1 65.24 1 261.79 424.81 218.06 800 700 600 500 400 300 200 100 0 2 Group 1 Group 2 Group 3 Group 4 Group 5 Group 6 Apical Middle Fig. 1: Average dye penetration depth (μm) in all six groups. Fig. 2: Average dye penetration depth (μm) in all six groups based on the images of the vertical cuts of the roots. roots 4 2020 09

research | 5 Fig. 5: A sample of cross-section cuts under the microscope. Dye penetra- tion depth was measured by a computer programme. Fig. 6: A sample of vertical cuts of roots. Measurements are not as accurate as for horizontal views. Fig. 7: The apical region can be seen with more detail in vertical cuts, but even so, the measurements could not be done as accurately as for hori- zontal cross sections. For better understanding of these findings, the depth of penetration was categorised as is shown in Table 2. The middle thirds of Group 1 show the lowest amount of dye penetration. The difference between the groups was not statistically significant (p > 0.05). However, the comparison between the apical thirds of the first three groups with the middle or coronal thirds of the same groups showed a sta- tistically significant difference (p < 0.1). This result was nar- rower in Group 1. Therefore, the most valid result is that in Group 1, for which both lasers were used, the lowest penetration depths were reported. In this group, the apical thirds showed significantly higher dye penetration depths compared with the middle and coronal thirds (Fig. 4). Discussion No study has reported on the combined use of laser and Resilon. In studies that used Resilon as a filling material, a similar efficacy to that of gutta-percha was observed. Thus, the concern of the current investigation was to determine whether Resilon would show an acceptable integrity with the dentinal walls after laser therapy. The graphs and standard deviation overlaps of the six groups show that only the group treated with both lasers plus EDTA had a statistically significantly lower amount of leak- age. The difference between the apical thirds and middle thirds of the same group was not statistically significant. As the average dye penetration depths in various areas in each cross section were reported as the resulting raw data of that slide, the horizontal images show more ac- curate and more reliable results (Fig. 5). But, as is seen in Figures 6 and 7 in vertical section imaging, the depth of penetration is not as easy and clear to measure as it is in horizontal samples. Therefore, for future studies, the use of horizontal cross sections only is recommended. 6 7 Conclusion Resilon as an adhesion-based filling material shows good results in combination with EDTA and both Er,Cr:YSGG and Nd:YAG lasers according to the crite- ria of this study. Editorial note: This article was first published in laser— magazine of laser dentistry, Vol. 12, Issue 2/2020. A list of references is available from the publisher. about Dr Mina Mazandarani holds a DDS and an M.Sc. in Lasers in Dentistry from the Aachen Dental Laser Center at RWTH Aachen University in Germany. She is a PhD candidate in the Clinic for Dental Conservation, Periodontology and Preventive Dentistry at RWTH Aachen University hospital. She can be contacted at mina.m83@gmail.com. roots 4 2020 11

technique | 5 6a 6b first twisted file to be used for enlarging a canal and is still in use today. Nickel-titanium (NiTi) files were introduced in 1991 and are still in use today. In 2007, at the European Society of Endodontology congress in Istanbul in Turkey, I gave my first lecture on the heat treatment of NiTi files and the creation of twisted NiTi files, and now all NiTi ro- tary files are heat-treated to different levels to create differ- ent properties. More recently, Traverse files (Kerr; Fig. 1), produced with another technique of heat treatment, were introduced, further advancing endodontics. files (Fig. 2), including a 25/.08 orifice opener of 17 mm in length, making it an ideal kit for all clinical situations as start-up files or initial file for shaping the canals. All Tra- verse files have a maximum flute diameter of 1 mm (Fig. 3), and this can limit the over-enlargement in the coronal part of the canal and will help the file to engage the space deeper and faster. The two other files are size 18/.06 and 13/.06. The job of these two files is to create a quick and safe access to the apex, that is, a traverse or “Le pas- sage” from the coronal part to the apical part of the root. The focus in this article is on clinical application in dif- ferent clinical situations. Traverse files are a set of three The first sequence (Fig. 4) is for large canals or canals that are easy to access. One starts with a 25/.08 Traverse 7 roots 4 2020 13

technique | 11 12 13a 13b 14a 14b 8 and 10 K-Files taken to working length. The M4 hand- piece can be a great help in establishing a small path. A 13/.06 Traverse is taken to full working length, followed by a 18/.06 Traverse, employing the same settings for speed and torque, 650 rpm and 3 Ncm. Once this step is done, one shifts to Adaptive Motion and uses the SM2 file and if possible the SM3. Figures 12 to 14 show examples treated with this sequence. about Adj. Prof. Philippe Sleiman is an Adjunct Professor at University of North Carolina (US) and Assistant Professor at the Lebanese University (Lebanon). He can be contacted at profsleiman@gmail.com. roots 4 2020 15

technique | 2 3a 3b Fig. 2: Micro-computed tomography 3D reconstruction of a maxillary molar, illustrating the root canal system’s complex anatomy. These areas must be cleaned of their organic debris and bacterial contaminants by thorough irrigation protocols and then subsequently 3D sealed with thermo-softened gutta-percha. (Image: © Dr Ronald Ordinola Zapata) Fig. 3a: Cone fitting. A suitably sized Conform Fit gutta-percha cone (Dentsply Sirona) is fitted into the tapered root canal preparation making sure of apical tugback at working length. The cone may then be cut by 0.5–1 mm to accommodate for apical movement. Fig. 3b: Conform Fit gutta-percha cone and preloaded gutta-percha cartridges. The Conform Fit gutta-percha fits intimately at the apical one-third of the root canal, and the single-use preloaded gutta-percha cartridge has enough material to fill an average four-canal molar. extent of downpacking in a single, continuous movement. Because the tip moves through a viscosity-controlled material into a tapered canal form, the velocity of the thermo-softened gutta-percha and sealer moving into the root canal system actually accelerates as the down- packing progresses, moving softened gutta-percha into extremely small ramifications (Fig. 2). The continuously tapered root canal preparation facili- tates the fit of a suitably sized Conform Fit gutta-percha cone (Dentsply Sirona; Figs. 3a & b). The master cone selected should be inserted to full working length and exhibit apical tugback (resistance to displacement) upon its removal. It is simple to fit a master cone into a patent, smoothly tapered and well-prepared canal.5–8 The cone 4a 4b Fig. 4a: Heat plugger fit. It is essential that an appropriate downpacking plugger is pre-fitted into each canal to its binding point. A rubber stop must be placed and adjusted to the appropriate coronal reference point for each canal. Fig. 4b: The electric heat pluggers are manufactured from annealed stainless-steel and are available in three sizes: large (60/.06, blue), medium (50/.05, yellow) and small (40/.025, black). roots 4 2020 17

technique | gutta- percha (Figs. 10 & 11). Because these pluggers heat from their tips, this separation burst of heat allows for quick, sure severance of the plugger from the already condensed and set apical mass of gutta-percha, mini- mising the possibility of pulling the master cone out. The length of this heat burst must be limited, as the goal is separation from the apical mass of gutta-percha without reheating. Clinicians must be very alert during the first second of the downpacking so that the binding point is not reached before completion of the downpacking. If heat is held for too long, the plugger will drop to its binding point in the canal and then cannot maintain condensation pressure on the apical mass of gutta-percha during cooling, pos- sibly allowing it to pull away from the canal walls. If bind- ing length is reached by mistake, the heat plugger should be removed immediately and the small end of the nickel– titanium (NiTi) end of a hand plugger may be used to con- dense the apical mass of gutta-percha until set. Once the downpacking has been completed in all canals of the tooth being treated, a radiograph may be taken to confirm the objective of apical seal. Backfilling The Gutta-Smart backfilling (Flow) handpiece accom- modates disposable preloaded cartridges of gutta- percha, and the dispensing needle tips are available in 20-gauge, 23-gauge and 25-gauge diameters. The one most commonly used is the 23-gauge one, as it is suit- able for most canals being treated. There is enough gutta- percha in the disposable cartridges to fill an average four-canal molar. Before backfilling, a small amount of sealer is lightly painted on to the walls of the root canals with a stain- less-steel hand file or paper point. The needle tip is placed into the root canal space until it penetrates the coronal aspect of the apical plug of gutta-percha for just a mo- ment, to re-thermo-soften its most coronal extent. This procedural nuance promotes cohesion between each injected segment of warm gutta-percha and the apical plug so that the two will seamlessly integrate. Segments of 4–7 mm of gutta-percha are then deposited. Injecting or dispensing too much gutta-percha may lead to cool- ing shrinkage and/or voids, which result in poorly obtu- rated canals within the deeper confines of the root canal space.8 As gutta-percha is extruded from the applicator tip, the viscosity gradient of the back-pressure produced will push the needle tip (and hence the Flow device) cor- onally from the root canal space. The technique sensitivity requires that, when this sen- sation occurs, the operator must sustain pressure on the activation cuff button mechanism as the needle tip moves from the canal. The stainless-steel or NiTi ends 7 8 9 Figs. 7 & 8: Initiation of downpacking. With the activation cuff depressed on the Gutta-Smart downpacking handpiece, the pre-fitted, preheated plugger is smoothly advanced without interruption through the mass of gutta-percha to within 4–6 mm of the binding point. Fig. 9: Sustained apical condensa- tion. The activation cuff on the Pack device should be released once within 3–4 mm of the apical binding point. The plugger should slow and stop within 2 mm short of the binding point. Apical pressure is maintained for a full 10-second sustained push in order to prevent the cooling gutta-percha mass from shrinking. 10 11 Figs. 10 & 11: Separation burst. The Pack activation cuff is depressed for 1 second and then released. The plugger is held in position for 1 second after the button is released, after which it is removed with the surplus of gutta-percha coronal to the apical plug adhering to the cooling plugger, leaving the apical seal intact. All portals of exit may be sealed, primarily with gutta-percha or a combination of gutta-percha and sealer, and the canal is ready for backfilling. roots 4 2020 19

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technique | 1d 1e 1f advantage, limiting fluids and blood absorption, prevent- ing discoloration and promoting a pleasant aesthetic outcome. canal instrumentation.6, 8 Future investigations with rigor- ous methods and materials are needed to compare the performances of these materials more accurately. Several investigations have evaluated other bioactive endodontic cements as pulp capping agents with short- term follow-up. More research with longer-term follow-up is needed to evaluate alternative pulp capping materials to MTA. In addition to the material used for direct pulp capping, there are several other factors that may influ- ence the final outcome; therefore, these variables should be controlled in future studies.5 Other bioactive endodontic materials, containing zirco- nium dioxide to provide radiopacity and guaranteeing su- perior colour stability, have been suggested to overcome MTA-related problems. The literature reports that some of the bioactive endodontic cements have shown prom- ising results,7 above all in vital pulp therapy, in terms of cementum deposition over the materials when used for root end filling,8 while others are associated with a signifi- cantly higher inflammation of the periapical tissue com- pared with tooth-coloured MTA.9 However, the number of studies comparing these products to MTA is still lim- ited and few histological investigations have evaluated bioactive endodontic cements as root end filling mate- rials. Their shortcomings include short-term follow-up, absence of controls, a large number of excluded spec- imens, placement of root end filling materials in intact teeth with healthy pulps that had no periapical lesions prior to treatment, preparation of root end cavities with- out prior canal debridement and filling, and root resec- tion and preparation of root end cavities prior to root MTA allows the clinician to achieve good outcomes in perforation repair (with respect to other materials such as amalgam, zinc oxide eugenol cements, calcium hy- droxide, composite resin and glass ionomer cements),10 reaching percentages of success ranging from 86 % to 92 %.11 Among the factors affecting the outcome of the therapy are the experience of the practitioner who per- formed the treatment, the negative influence of placing a post after treatment, the presence of preoperative lesions and communication between the perforation site and oral cavity, and the sex (female) of the patient.6, 12 The location of the perforation and the quality of the final restoration had a significant influence on the outcome of perforation repair, while the site of perforation (mid-root and apical) and a perforation size larger than 3 mm were reported as significant predictors for the recurrence of progressive inflammation.12 Recent studies, on the contrary, have concluded that the success of repairs carried out using MTA was not affected by the size of the perforation.13–15 One of the main factors to consider when applying MTA is the pH of the surrounding tissue: a persistent infection or excessive bleeding can lead to decrease of the pH, thus altering the setting properties of MTA.11 The literature reports that the presence of bismuth oxide as a radiopacifier in the MTA formula can lead to tooth discoloration.6 This potential can turn into a great dis- advantage in vital pulp therapy, treatment of resorption or perforation repair. To overcome this problem, several 2a 2b 3 roots 4 2020 23

technique | pulp capping, root canal obturation during apexogenesis and revascularisation procedures, apexification of imma- ture teeth and root canal perforation repair. An advantage of the MAP System is the possibility of employing nickel- titanium tips: these can be used in both orthograde and surgical procedures, and they allow placement of the material exactly where it is needed because they can be bent as necessary. After sterilisation, the tips regain their initial straight shape. When using an MTA carrier, it is mandatory to avoid the material hardening inside the applicator, because it could be almost impossible to remove it afterwards. Cleaning the tip immediately after MTA extrusion (better if done with dedicated tools) helps maintain the efficiency of the instrument. The amount of MTA to be used is dependent on the clini- cal procedure, but in general, it is not recommended to fill a root canal completely with MTA, because after setting, it would be difficult to remove the material from the root canal. A rigorous protocol and the use of specific tools helps achieve good outcomes in primary and second- ary endodontic treatments using MTA as an obturation material. Clinical application When applying MTA, for the clinician, it is important to position the material precisely into the site, avoiding the cement spreading into the cavity or being wasted. Without a dedicated carrier, the operator can shape MTA into a bar and deliver it into the cavity by means of a probe or a plugger. Once the canal has been cleaned and shaped, the MTA can be positioned into the root canal and packed until the apical portion has been filled. It is then possible to do the backfilling and restore the tooth (Figs. 1a–f). This technique is not particularly easy to perform, because it requires a skilled clinician to be executed correctly and without a huge waste of MTA. The use of a carrier makes it easier to deliver the correct amount of MTA precisely where it is meant to be posi- tioned. The MAP System allows the clinician to choose the size of the tip, according to the size of the defect to be filled. The bendable tip can be adjusted in order to easily reach the area to be treated. It is also possible to position a rubber stop to help the operator record the correct ref- erence point. The MTA is packed, leaving the canal walls clean (Figs. 2a & b). The red colour-coded tip of the MAP System was used in this case to fill the perforation in the premolar shown in Figure 3. A more coronal and larger perforation, how- ever, was filled with MTA using the blue colour-coded tip (Figs. 4a & b). In the case of a tiny perforation, a smaller tip (yellow colour code) was selected in order to reduce waste of material and ensure greater precision (Figs. 5a–c). Figures 6a–c show step by step the filling of a floor per- foration in a maxillary first molar using the MAP System. about Dr Massimo Giovarruscio is a highly skilled dental professional with extensive experience in endodontics and restorative and aesthetic dentistry. With over 19 years of experience in dentistry, he has developed his reputation within the profession as being an excellent clinician, endodontist and postgraduate lecturer. He is an accredited specialist in endodontics and a clinical teacher in endodontics at the Faculty of Dentistry, Oral and Craniofacial Sciences at King’s College London in the UK to both undergraduate and postgraduate students, as well as a visiting professor at the CEU Cardenal Herrera University in Spain in the international master’s course in endodontics. He has also developed exemplary communication skills and has a proven track record in private practice in both the UK and Italy, where he works in Rome, Bristol and London, specialising in endodontic treatment and restoration of endodontically treated teeth. Dr Giovarruscio is regarded as an opinion leader in endodontics and restorative procedures related to the endodontically treated tooth. He lectures worldwide and has published many articles in international journals and written several chapters and manuals on endodontics. He is co-author of the book Manuale di Endodonzia (Elsevier, 2013). He is an active member of the European Society of Endodontology and of the Italian Society of Endodontics. Dr Francesca Cerutti graduated from the University of Brescia in Italy in 2007. In 2013, she obtained her PhD in materials for engineering from the same university, and in 2016, she completed a master’s degree in aesthetic medicine. She collaborates with Dr Dino Re at the University of Milan in Italy, where she conducts clinical research and, since 2018, has been a visiting professor. Dr Cerutti has published several articles in peer-reviewed journals and has co-authored books on restorative dentistry and endodontics. She has spoken at national and international congresses on post-endodontic restoration and aesthetic reconstruction of teeth. She is a reviewer for international journals such as the Journal of Adhesive Dentistry, the European Journal of Paediatric Dentistry and Biomaterials. Dr Cerutti is a member of the Italian Society of Endodontics and served as editorial coordinator of the Giornale Italiano di Endodonzia from 2008 to 2011. She is a silver member of Style Italiano Endodontics. roots 4 2020 25

technique | 2 3 Fig. 2: The diamond-coated bur is held against the buccal surface of the crown with light pressure and moved in a direction that is parallel to the long axis of the diamond-coated bur to create a slot through the ceramic. Fig. 3: The diamond-coated bur continues to be used in a direction that is parallel to its long axis, sawing through the ceramic until either dentine (ceramic crown) or metal (porcelain-fused-to-metal crown) is encountered. The typical reasoning is that the harder the material and the more abrasive the ceramic, the more pressure (force) needs to be applied to cut it. Diamond-coated burs are used to cut ceramics because carbide burs are ineffective at cutting ceramics. When a carbide bur contacts a ceramic, the ceramic rapidly wears the car- bide bur’s flutes, creating irregularities on the carbide surface that may lead to microfracturing of the ceramic surface. Microfractures will not present an issue when removing the crown, but if the plan is to preserve the crown after endodontic treatment, it may lead to crown failure related to crack propagation over time. Whereas a diamond-coated bur abrades the surface being contacted, a carbide bur cuts. Ceramics need to be abraded in order to penetrate the material; they cannot be cut, as it leads to structural damage (microfractures) and is an inefficient prepa- ration method. Metal needs to be cut, and essentially a carbide bur mills the material it is preparing. Monolithic zirconia or zirconia-based restorations All-ceramic restorations constitute the majority of what has been used in the US with increasing frequency over the past ten or more years, and zirconia, especially in the posterior, is the dominant material chosen owing to its higher strength then other ceramic types. As zirconia is being manufactured with greater translucency, its use in the anterior will increase, especially in those patients with parafunctional habits that other ceramics may not withstand long term. The technique and materials that will work on zirconia, being the hardest ceramic mate- rial in use currently, will also work on ceramics that have lower material hardness. 4 5 Fig. 4: A slot is next cut across the occlusal surface in a similar manner that is continuous with the slot cut on the buccal surface, again moving the diamond- coated bur parallel to its long axis. Fig. 5: Crown removal of an anterior crown requires the buccal slot to continue over the incisal edge to the lingual surface. roots 4 2020 27

technique | 9 10 Fig. 9: After access through the zirconia or ceramic crown with the round diamond-coated bur, a carbide bur is utilised to complete endodontic access to unroof the pulp chamber. Fig. 10: Unroofing the pulp chamber may be accomplished with the diamond-coated bur or a carbide bur (practitioner preference), and the endodontic access is completed. As the crown may be fairly thick in this area, depend- ing on how the original tooth was prepared or what remained of the tooth prior to preparation, in some cases, this slot may be ≥ 3 mm deep. A flat-bladed instrument such as a crown remover is inserted into the buccal slot, where the occlusal or incisal slot is continued and a rotational torquing mo- tion is made to split the restoration into two halves and separate it from the prepared tooth (Fig. 6). It is not advisable to attempt this with a flat-bladed composite instrument, as the torque generated will either break the tip of the instrument or warp it. Crown removal in- struments are better designed for this and can with- stand the forces generated without instrument break- age. Should the crown not split into two pieces, verify that both grooves are continuous with the dentine and deepen them if ceramic remains in the slots. If the slots have penetrated to the dentine, and the crown is not splitting, continue the slot 2–3 mm on to the lingual surface. Should that still not allow crown splitting, using the same diamond-coated bur, remove ceramic inter- proximally at the expense of the crown being removed, in order to create space to allow the crown halves to separate when torqued with the instrument. Dental adhesives are less retentive to zirconia than to tooth structure, and there is debate whether a true adhesive bond occurs to this substrate.5 Upon crown removal, often the luting material is still bonded to the dentine, and this can be prepared off during re-prepa- ration of the tooth. This also applies to zirconia-based restorations that have an overlying ceramic for improved aesthetics, whereas ceramics such as lithium silicate, 11 12 Fig. 11: The diamond-coated bur is used to create the slot in the ceramic to the metal substructure with a porcelain-fused-to-metal crown. Fig. 12: The carbide bur is utilised to continue the slot through the metal to the underlying dentine. roots 4 2020 29

technique | through the metal into the dentine and then the outline form is widened to the dimensions of the outline cre- ated in the ceramic with the carbide bur and through the dentine to unroof the pulp chamber (Fig. 14). Conclusion Typically, access in precious and semi-precious met- als can be performed with a single carbide bur, but non-precious metals may require multiple carbide burs in order to complete the task. This also is true with re- moval of PFM crowns. All-metal crowns require more metal to be removed and usually require multiple car- bide burs to accomplish the task. Light pressure, allow- ing the carbide bur to cut the metal, is more efficient and less likely to snap the head off the carbide bur, which may occur when excessive pressure is applied to the restoration with the carbide bur. The carbide bur should be disposed of after a single crown removal or end- odontic access or when it stops cutting the metal during the procedure. The diamond-coated burs may be used multiple times and should be discarded when the dia- mond particles begin to fall off the shaft of the rotary instrument. This can be typically noted by baldness on the tip, as that area takes the most stress when in use. Crown removal and endodontic access can be accom- plished with efficiency and decreased chair time when the diamond-coated burs and carbide bur mentioned are utilised as described. Light pressure with a stroking motion (for crown removal slot preparation) or circular outline formation (endodontic access) with copious irrigation improves efficiency while decreasing stress on the rotary instrument as well as the practitioner. Acknowledgement: The author would like to thank Robert Wojciechowski for the illustrations in this article. Editorial note: A list of references is available from the publisher. contact Dr Gregori M. Kurtzman Implant Cosmetic Dental Center 3801 International Drive 102 Silver Spring MD 20906 USA Phone: +1 301 5983500 dr_kurtzman@maryland-implants.com www.maryland-implants.com IrriFle Flexible root canal irrigation needle Join the glide-cleaning revolution AD Order from your favorite dealer on pd-irriflex.com erland

is coming to PRAGUE 20–23 May 2021 Prague, Czech Republic www.ROOTS-SUMMIT.com Tribune Group GmbH is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry. Tribune Group GmbH designates this activity for 18.5 continuing education credits. This continuing education activity has been planned and implemented in accordance with the standards of the ADA Continuing Education Recognition Program (ADA CERP) through joint efforts between Tribune Group GmbH and Dental Tribune International GmbH.

case report | Preparation with remover file The first and decisive step in retreatment is the complete removal of the inadequate or aged gutta-percha filling. For this purpose, we use special remover files in our practice (Fig. 3). The 30/.07 MicroMega REMOVER file (COLTENE) adapts flexibly to the individual canal shape. In this case, we loos- ened the existing obturation material in this way without using additional solvents. At a speed of 1,000 rpm with continuous rotation, the filigree file was inserted into two-thirds of the canal. Thanks to the non-cutting instrument tip, the surround- ing dentine was spared as much as possible. This additional safety component has proved to be very valuable in daily work. Subsequently, the use of suitable nickel-titanium (NiTi) files is recommended for further shaping of the canal. The remain- ing distal root was treated with the HyFlex EDM OneFile in the contra-angle handpiece at 500 rpm. The 20/.05 HyFlex EDM file was used in the mesial canals. The speed was also 500 rpm. With the remover files, the existing gutta-percha could be eliminated surprisingly quickly and easily. Within seconds, a clean access to the apical third was achieved. To the root in autopilot Even more exciting for us was the test drive with a new type of digital endodontic assistance system. The CanalPro Jeni endodontic motor (COLTENE) was used for the first time to perform the mechanical and chemical preparation in the case described (Fig. 4). The motor is named after its devel- oper, Dr Eugenio Pedullà. For a long time, the Italian end - odontist was occupied with the question of how the concept of autonomous driving could be employed in endodontics for safe and less error-prone root canal therapy. The result is a fully automatic endodontic motor that independently finds its way through the root canal. The application was comparatively simple: just work steadily with light pressure from the coronal to the apical aspect. Meanwhile, the motor decides independently on the appropriate motion sequence. For this purpose, the software of the assistance system uses complex algo- rithms that make the whole thing possible in the first place. Every millisecond, the device controls the variable file movements and continuously adjusts the rotational move- ment, speed and torque. Unnecessary file stress is also continuously corrected by Jeni. The selection of the appropriate NiTi sequence on the touch screen was quick and easy. However, it took a bit of getting used to the consequent preliminary work in the canal from coronal to apical, since I was used to advancing carefully in a small pecking motion downwards relying on tactile feedback. With Jeni, the dentist just holds the con- tra-angle handpiece; the motor does the rest and adjusts the rotation to the root canal anatomy. This “teamwork” also makes root canal therapy much more efficient and 5 6 Figs. 5 & 6: Post-op radiographic images. less prone to errors. After my initial reluctance, I grew more confident and trusted Jeni to indicate in good time when things could get tricky in the canal. The digital co-pilot also indicates when it is time to change files and when to rinse. In turbulent weeks with many treatments and emergencies, you will be quite grateful to have an additional safeguard in addition to the assistance at the chair to subtly remind you of the next step in the treatment process. For the final shaping of the canal, the 25/~ HyFlex EDM OneFile was used in the mesial canals. A 40/.04 EDM file was used in the distal canal. The result on the radiograph after obtura- tion was extremely pleasing. Hopefully, it will be more durable than the first treatment approach five years ago (Figs. 5 & 6). Conclusion During revisions, flexible remover files can be used to effi- ciently loosen and remove insufficient gutta-percha fillings. Digital endodontic assistance systems navigate the den- tist step by step through the mechanical and chemical preparation by adjusting the variable file movement. Thanks to the continuous preprocessing from coronal to apical, canal shaping is much more efficient and less prone to errors than before. contact Dr Silviu Bondari 186 rue Constant Fouché 27210 Beuzeville France drbondari@yahoo.com roots 4 2020 35

trends & applications | 2a 2d 2b 2c 2e 2f Figs. 2a–f: Planning the guide path with CBCT software (a). A planned path on the CBCT image (b). An image of a digital impression in digital dentistry software (c). An endodontic guide with a low-speed drill (d). A template guide and drill (e). Placing the guide over a tooth (f). additional cost to the patient for fabricating the guide is much less than replacing the tooth. It enables predictable treatment of canals that otherwise would not be treatable. Very few patients have turned down the opportunity to save a tooth. This example of the reapplication of technology may be useful in other areas of dentistry. The only limitation is our imagination. To provide a look into the future, I have listed other challenges we could pursue. I hope you read this with no expectations but rather an open mind for what could be: – Current technology: Patients have multiple electronic medical files containing history and current medications. In the future, DNA may also be available on a file. – Future potential applications: Fingerprint access or re tinal scans could securely protect a single medical file that would efficiently transfer medical information to dentists. This information would enable personalised prescription of medications and more accurate use of the patient’s med- ical history. It may prevent accidental allergic re actions, adverse interactions and overprescribing. – Current technology: Microscopes can view computer screens through their optics. – Future potential applications: Radiographs, CBCT and digitalised impressions should be viewable through the microscope. The dentist could use tracked files (viewable on CBCT) in conjunction with preoperative or intraopera- tive images, to directly or indirectly guide the instrument, in an image-guided procedure. – Current technology: Ultrasonic light-activated nanoparticle- infused irrigation liquids need to be further adapted for irrigation of the canal system. – Potential dental application: Enhanced ultrasonic irriga- tion that would eliminate bacteria, viruses and prions. – Current technology: Laser fusion of dentine should be explored for obturation of root canals. – Potential dental application: The endodontic obturation process should seal the dentine and match the root’s physical properties to reestablish its strength. The pro- cess should be able to be reversed if retreatment is required. – Current technology: CBCT can identify canals and be used to measure their length accurately. – Potential dental application: This process should be automated. The future may include significant advances in technology, but the application of existing technology will continue to open the doors for new treatment. Imagination is the key to unlocking those doors. about Dr Randolph Todd is a technology- inspired diplomate of the American Board of Endodontics who began his academic dental career at Tufts University School of Dental Medicine, Boston, US. Upon completing a general practice residency at North Shore University Hospital and Long Island Jewish Medical Center (NSUH/LIJ), New York, US, he pursued his endodontic specialty training at New York University College of Dentistry (NYU Dentistry). Over the past forty years, Todd has maintained an exclusive microsurgical endodontic private practice in New York. roots 4 2020 37

interview | in clinics around the world that, in order to boost profits, one needs to try and pack as many appointments into a daily schedule as possible. There is also the belief of an unsuspecting public that a short consultation is some- thing positive, when in fact we know that dentists have never been trained to work fast; they have been trained to provide quality service to reach the best results. The whole reason behind Slow Dentistry is the commu- nication of four basic cornerstones that cannot be con- tested by any dentist in the world. These cornerstones do not rely on any technology or require special education. They are ubiquitous and globally accepted as true. When applied, they guarantee that patients will be treated in a disinfected dental unit, that they will receive an explana- tion in terms of what will be done to them from a medical perspective, that their experience will be pain-free and that a dental dam will be used in all root canal procedures as well as in most restorative dental work. We find these to be universal rights that must always be present on a trip to the dentist. The concept came about many years ago because I was seeing a lot of examples of failed dentistry, mostly poorly performed root canals, and could not understand why so many dental professionals were doing such a poor job. I later realised that it was mostly due to the time that the patient spent in the chair and not necessarily the fact that dentists were not good at their jobs; the clinics were simply managed in this way. Having approximately 16 appointments a day, dentists had limited time to fix all the problems. “The general public currently has no idea of their rights at a dental appointment.” Dental practices that work with insurance companies or sign subsidised deals with financial organisations do not usually get rated on the quality of their work or the time they take to complete a procedure, but rather on the technicality of their work. I feel that this is unacceptable to the general public. The goal of Slow Dentistry is to improve the standard of care globally through public awareness. People have to roots 4 2020 39

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practice management | make visible how one’s own behaviour has an effect on or is received by the other person, how a situation or perfor- mance is assessed or what potential for improvement ex- ists. Correctly used, feedback can therefore be extremely valuable. In everyday professional life, it is almost indis- pensable for the further development of one’s behaviour. Differentiation from praise Praise is usually not very specific, such as “you did a good job”, “I am very pleased with you” or “keep up the good work”. Praise is therefore positive feedback which, owing to a lack of specificity, does not bring about any lasting change. Praise might be very important in daily in- teraction—but giving feedback is essential. Giving feedback Giving constructive feedback has to be learned because, if applied incorrectly, it can have the opposite effect to that intended. Ideally, feedback should follow a method- ical framework—feedback rules. The feedback should help the recipient to reflect on his or her behaviour in order to better assess its effect on others and to mod- ify his or her behaviour if necessary. Feedback must be conveyed in a particular form in order to be fully effective. Feedback rules In order for feedback to have a motivating effect and to encourage one to develop oneself further as a conse- quence, it is important to follow the ten golden rules of feedback. The context especially is of vital importance: feedback is particularly effective if it is given promptly. Feedback should never take place according to fixed times. It makes much more sense to give constructive feedback as relevant things—whether positive or nega- tive—arise. Rules for constructive feedback: 1. Give feedback only in an emotionally relaxed state. This will help you to stay objective and avoid strong emotional reactions. 2. Is your counterpart receptive to feedback? Is feed- back desired? Ask for feedback! 3. Separate statements about behaviour from state- ments about personality traits! In this way, you can avoid affronting the person and increase the prob- ability that your feedback will be well received. IMPORTANT: Behaviour must be clearly separated from identity. There must be no moral judgement, generalisation or interpretation. 4. If you have negative things to communicate, also express your positive experiences, perceptions and feelings. 5. Give very specific feedback. Use concrete examples of the behaviour to which your feedback relates. 6. Observation: Describe only what is visible and objec- tifiable for all. 7. Perception/effect: Make sensory statements and name your own (emotional) reaction to the recipient of feedback. Say what and how something has af- fected you: “It affects me …”. 8. Express yourself exclusively using “I”: “I have seen …”, “I have noticed …”, “I feel …”. 9. Recommendation/wish: Address specific criteria for desirable behaviour so that your feedback is useful for future situations. “I recommend …”, “I would like …”, “I would like it if …”. 10. Be brief and only convey as much as your counter- part can take in. In teams, feedback should always be given directly to the intended recipient. Editorial note: This article was first published in laser— magazine of laser dentistry, Vol. 12, Issue 1/2020. Receiving feedback about Receiving feedback is also something that has to be learned. Most people initially react defensively to feed- back and this is just what must be avoided. Constructive feedback is valuable because it reduces our blind spot. Explaining or justifying oneself immediately after receiv- ing feedback would be counter-productive. Furthermore, feedback is not debatable. Even if one perceives the situation differently to the feedback received, it shows in a very appreciative way how one’s behaviour affects others. The giver of the feedback must always intend to trigger a positive outcome—regardless of whether it con- cerns something negative that needs to be improved or something positive that needs to be reinforced. If one is not receptive to feedback, one is unlikely to receive authentic feedback. Hence: LISTEN. TAKE IT IN. SAY THANK YOU. Germany-based Andrea Stix is a consultant for communication strategies. She is a coach in practice marketing and is specialised in personality diagnostics. She currently works as strategic consultant for CAMLOG. contact Andrea Stix, MSc, MBA Strategic consulting CAMLOG Distribution GmbH Phone: +49 7044 9445-733 andrea.stix@camlog.com roots 4 2020 43

news | Decellularised matrix hydrogel may promote dental pulp regeneration By Monique Mehler, Dental Tribune International Dental pulp regeneration has been a great challenge to researchers in the field of endodontics for decades. It has been widely regocnised that tissue-engineered biomateri- als might be beneficial for endodontic regeneration; how- ever, single-component materials or shape-fixed scaffolds are not able to meet the requirements for multifunctional dental pulp regrowth. Inspired by the clinical use of multiple acellular tissue grafts, researchers in China have become interested in decellularised dental pulp matrix. In a recent study, scientists from Dr Zhengmei Lin's group at the Affiliated Stomatological Hospital of Sun Yat-sen University, and their collaborators from School of Materials Science and Engineering in Guangzhou developed a decel- lularised matrix hydrogel (hDDPM-G), derived from human dental pulp, which might be able to serve as a growth- permissive microenvironment for dental pulp regeneration. In an interview with Dental Tribune International, Dr Ying Bai, who is part of the team that carried out the research, said that the most important requirements were that the bio- material had to be gel-based, fit into the root canals, form in situ and exhibit bioactivity. After complete decellularisation was implemented, protein contents found in the human decellularised dental pulp ma- trix were found to contribute to promoting cell proliferation, migration and regulation of stem-cell differentiation. The results showed that hDDPM-G-coated surfaces promoted hDPSC adhesion, migration and proliferation. Further more, hDDPM-G coatings facilitated odontoblast-like, neural-like and angiogenic differentiation of the seeded hDPSCs after being cultured in induction media for 14 days. “The whole study has been quite challenging, since it pi- oneers the exploration of endodontic regeneration at the intersection of materials science, biology and medical sci- ence,” Bai explained. “Among all the challenges we faced, the preparation of decellularised dental pulp hydrogel was probably the most difficult. The availability of healthy dental pulp is extremely limited—a small amount of hydrogel might be obtained from hundreds of routinely extracted third mo- lars. Moreover, the physical properties of the hydrogel could undergo batch-to-batch variations. Therefore, it is difficult to standardise the fabrication process of such tissue-derived biomaterial; we are still working on it,” he continued. This recent research into regenerative endodontics is only the beginning, according to researchers. The ultimate goal is to develop a novel therapeutic solution for dental pulp regeneration. Here, Dr Qiting Huang, who participated in the study, is showcasing tissue-derived decellularised matrix hydrogel. (Image: © Sun Yat-sen University) Looking to the future, Bai and his colleagues are investi- gating the possibility of developing a novel therapeutic solu- tion for dental pulp regeneration for clinical use in patients. He added: “The reported work was just the beginning of our journey in exploring the biological functions of the de- cellularised dental pulp matrix hydrogel. Through this work, it is clear that the hDDPM-G could promote multifunctional differentiation of dental pulp stem cells, but we do not yet know why or how. The underlying mechanisms are still to be discovered. However, further work on clinical applica- tions, proper treatments and animal models will be con- ducted. There might be a long way to go from laboratory to dental clinic, but we hope that this complex but viable biomaterial will be able to inspire more multidisciplinary research in the field of endodontic regeneration.” The study, titled “A decellularized matrix hydrogel derived from human dental pulp promotes dental pulp stem cell proliferation, migration, and induced multidirectional dif- ferentiation in vitro”, was published on 1 October 2020 in the Journal of Endodontics. roots 4 2020 45

manufacturer news | Co-pilot upgrade COLTENE extends options for fully automated endodontic motor Congestion reports in real time or information about new road layouts—regular updates of your navigation system help you and save your nerves when driving. The same concept underlies guided endodontics. With a range of new options, the latest end- odontic motors extend their capabilities for fully automated navi- gation through the root canal. As a result, these clever assistance systems offer even more flexibility during treatment. Extended file sequence With the latest update, the international dental specialist COLTENE has extended the options of the fully automated CanalPro Jeni endodontic motor. The motor automatically finds its path through the root canal, working in unison with the mechanical and chemi- cal preparation every step of the way. The user can choose from a number of popular sequences for the flexible nickel-titanium files. The highlight of the latest update is the addition of remover files, which make a significant difference to an endodontic revision treatment. The novel 30/.07 HyFlex and MicroMega remover files fit perfectly into the established file systems and quickly and reli- ably remove inadequate gutta-percha fillings as well as similar ageing endodontic restorations. Owing to their intricate shape, they adapt to the natural contour of the canal and ef- ficiently loosen the existing obturation material. In addition, the reaction time of the motor and the touch screen has been further reduced. Graphic optimisa- tion and enhanced system performance make the Jeni even more attractive. The result of these im- provements is that treatment becomes even safer and more comfortable. Exclusive service page Innovation leader COLTENE has developed a special service page for dental practices which provides regular access to the latest updates and information. Dentists can simply register with the serial number of their CanalPro Jeni at https://canalpro.coltene.com/ register-jeni. With these new options and improvements, this clever navigation aid makes it easier than ever to get started in endodontics. The user works forwards continuously from the coronal to apical aspect, applying only slight pressure, while the motor decides independently on the progress of movement. Employing complex algo- rithms, the software can control the variable file move- ments at millisecond intervals by constantly regulating rotational movement, speed, torque and file stress. Descriptive short video The mode of operation of the endodontic motor is demonstrated in detail in a new short video. The informative, explan- atory video is now available to view at https://youtu.be/Qw3uc3hSTkg on the COLTENE YouTube channel (see qr code). At https://canalpro. coltene.com/jeni, you can find more information about the CanalPro Jeni and register for your personal demonstration appointment. www.coltene.com roots 4 2020 47

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