A2 ◊Page A1 ENDO TRIBUNE Dental Tribune Middle East & Africa Edition | 1/2021 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 1: Tooth #12—the radiograph showed a large periapical lesion. The asymptomatic tooth was prepared with an ISO 25/.06 TF Adaptive file (Kerr Dental). Fig. 2: Tooth #12—root canal filling was performed with mineral trioxide aggregate (ENDOSEAL MTA, Maruchi). Note the sealing of the apical ramification, possible because of the effective cleansing and decontamination of the apical terminus. There was almost complete healing after 12 months. Fig. 3: Tooth #33— the patient showed a buccal sinus tract that radiographically corresponded to the area between tooth #32 and tooth #33. The CBCT and radiograph showed a large periradicular lesion, especially on the distal side. Preparation was performed with a 20/.07v ProTaper Gold (F1; Dentsply Sirona). Fig. 4: Tooth #33—root canal obturation was performed with a sealer and carrier-based gutta-percha (AH Plus and Thermafil, Dentsply Sirona). The radiographic control six months post-op showed that several lateral canals had been filled and the healing process was in progress. at 50°C, which left a higher quantity of debris and the smear layer widely distributed.14 Other studies have reported that NaOCl at a concentra- tion of 1 % heated to 60°C was signifi- cantly more effective than 5.25% at 20°C. The advantage of using lower concentrations of NaOCl, heated to higher temperatures, could be re- lated to a twofold effect: the same effectiveness and less systemic tox- icity than that of non-heated, high- concentration NaOCl.15 Agitation techniques However, the effect of agitation on tissue dissolution was proved great- er than that of temperature and with continuous agitation resulted in the fastest tissue dissolution.16 Compar- ing the efficacy of various agitation systems, De Gregorio et al. found a limited penetration of the irrigant into lateral canals using an apical negative pressure irrigation system, whereas passive ultrasonic irrigation demonstrated significantly more penetration of irrigant into lateral canals.17 Nevertheless, it could be reasonable to combine the two tech- niques, using heated NaOCl and agi- tating it with the preferred method. Laser-activated irrigation using SWEEPS The physical concepts behind laser- activated irrigation and SWEEPS technology have already been ex- plained in a previous issue of this magazine (roots-international maga- zine of endodontics 4/2019).18 One of the great advantages of SWEEPS over all of the other activation techniques is its profound effectiveness. Unlike all the other techniques, SWEEPS ac- tion is not limited to the vicinity of the tip, as is the case with ultrasonic irrigation, but it is also effective at distant regions of the root canal sys- tem.19,20 For this reason, SWEEPS only requires positioning of the tip in the access cavity to stream the irrigant into all of the endodontic space at the same time. This is different to other techniques, which require nee- dle or tip/ file or probe insertion up to the apical third of each canal or so for irrigation after the root canals have been prepared. Thus, SWEEPS Fig. 5: Proper isolation for SWEEPS is important. A liquid dam was interlocked beneath the dam clamp. Traditional access cavity preparation of the maxillary first molar was performed using a cylindrical or round diamond bur under magnification (4.5–6.0 x). the treatment, EDTA cleans the canal walls of debris and the smear layer produced during instrumentation, just before the final decontamina- tion. EDTA is slightly irritating but not toxic to periapical tissue. Chlorhexidine Chlorhexidine (2%) has good an- tibacterial properties, but it is not able to dissolve pulp tissue. This sug- gests its use only in an additional final decontamination step because of its unique substantivity prop- erty, which could allow persistent residual antimicrobial action. It is important to prevent interaction between NaOCl and chlorhexidine, by rinsing the canals with distilled water in between solutions to avoid the formation of precipitates that may discolour the tooth and that may contain potentially mutagenic compounds.9,10 Its inability to dis- solve organic tissue also explains the absence of toxicity to periapical tissue.11,12 Other solutions Other chemical solutions have been investigated and used in endodon- tics. Among these, hydrogen per- oxide, iodine, citric acid, ozone (gas) and ozonated water are available, but none of them have demonstrat- ed superior properties and results to the previously cited NaOCl and EDTA solutions. EDTA plus Cetav- lon and a mixture of doxycycline, citric acid and a detergent are new solutions that combine different components, surface-active agents and antibiotics which can be very ef- fective and have broader action. The experimental use of nanoparticles is also very promising. Irrigant activation techniques The initial irrigation phase and the irrigation during shaping are per- formed using a syringe with an end- or side-vented needle that can only negotiate the canal up to the middle third. Therefore, it must be considered that the efficacy of hand irrigation is quite limited; thus, sup- plementary, active and dynamic ir- rigation (Table 2) is proposed at the end of the treatment to ensure the cleaning of the dentinal walls and the deep decontamination of the en- dodontic system.13 Among the vari- ous activation methods, we can find systems that heat the irrigating solu- tions or that activate the solutions by agitation, with positive or negative apical pressure. Heating Scanning electron microscope stud- ies on intra-canal heating of NaOCl at 180°C have proved this method to be more effective for cleaning the canal walls than extra-canal heating Chemomechanical systems Positive pressure systems Negative pressure systems XP-endo Finisher Hand dynamic Sonic Multi-sonic Ultrasonic Laser-activated irrigation (PIPS* and SWEEPS**) XP-endo Finisher * PIPS = photon-induced photoacoustic streaming. ** SWEEPS = shock wave enhanced emission photoacoustic streaming. Table 2: Irrigant agitation techniques. can be used from the initial phase up to the final phase of the therapy, permitting a progressive decrease in the bacterial load before any le is used. The efficacy and effectiveness of SWEEPS rely on both chemical activation of the endodontic solu- tions by agitation,21,22 improving the ability of irrigants to kill bacteria and to dissolve tissue, and mechani- cal flushing action to clean the root canal wall.23,24 Researchers have found the SWEEPS dual modality to be more effective than the single-pulse modality SSP (super-short pulse; PIPS, photon- induced photoacoustic tic stream- ing).25–28 Using the SWEEPS dual-pulse modality, the sudden expansion of the second bubble, generated by the second laser pulse, exerts additional pressure on the first bubble, lead- ing to its violent collapse, during which shock waves are emitted also in very small canals. Furthermore, shock waves are emitted from the collapsing secondary cavitation bub- bles that form naturally throughout the entire length of the canal during irrigation.25–29 The laser-activated secondary cavitation bubbles are in close proximity to the canal walls during their collapse, generating shear stress and vortical flows that are able to remove debris, the smear layer and biofilm from the root canal surface, as well as from undetected and uninstrumented anatomical ar- eas, such as isthmuses, lateral canals, loops and ramifications, thereby in- creasing the cleaning and decontam- ination mechanism even further (Figs. 1–4). The enhanced pressure generation along the root canal con- sequently also increases the depth of penetration of irrigants into dentinal tubules.25–28 Clinical protocols Proper patient draping with a water- proof bib to protect clothing is high- ly recommended. Local anaesthesia is performed in all cases (asympto- matic and symptomatic) to avoid any unpleasant sensation of internal pressure during the treatment. A dental dam is then applied, and a liq- uid dam is interlocked beneath the clamp to ensure complete isolation (Fig. 5). In case of occlusal or proximal decay or a defective filling, complete removal of the carious tissue and filling must be performed, followed by composite reconstruction of the entire tooth crown; this preliminary step is mandatory to minimise leak- age and reinfection. Furthermore, good marginal sealing prevents any irrigant extrusion during laser-acti- vated irrigation. Access cavity preparation At this point, the access cavity is opened using a small carbide, or cylindrical or round diamond bur under magnification (4.5–6.0x). Traditional access cavity prepara- tion, following the laws of central- ity and concentricity, is advisable (Fig. 5).30 Several studies have dem- onstrated the lack of usefulness of ultra-conservative “ninja” access cav- ity preparation in terms of fracture strength and preservation of the original canal anatomy during shap- ing compared with traditional access cavity preparation, particularly at the apical level. Furthermore, stand- ardised access cavity preparation is advisable when the X-SWEEPS mo- dality is chosen for laser-activated irrigation. Future publications will explain this topic in depth in order to establish the correct laser settings to be used with standardised access cavity preparation volumes. What- ever the pathology is, the concept is to minimise the root canal shaping, optimising the cleansing and decon- tamination of the endodontic space by exploiting the chemomechani- cal flushing of SWEEPS. The main difference between asymptomatic and symptomatic pulpitis and apical periodontitis therapy is in the longer or shorter initial NaOCl SWEEPS-acti- vated irrigation phase. Retreatment also involves a few differences in the energy applied during the initial phase when filling material has to be removed. Asymptomatic and symptomatic irreversible pulpitis In the case of irreversible pulpitis, the pulp is irreversibly inflamed, with or without acute symptoms. The patient’s age and preoperative radiograph give information on a possible immature apex; this con- dition contra-indicates a full-power SWEEPS irrigation and suggests a more careful intervention and low- ering of the energy used (more to follow). Once the pulp chamber has been opened, excessive bleeding may be present, indicating the pres- ence of inflamed pulp tissue inside the chamber and root canals. In this case, one-visit therapy is advisable. The treatment starts with NaOCl irri- gation by syringe (3–5 ml) and simul- taneous activation by Er:YAG laser (2,940 nm; LightWalker AT, Fotona), using the dual-pulse (25 µs duration) Auto-SWEEPS modality for 30–40 seconds. The resting time after irriga- tion can be extended to 1–2 minutes to allow more NaOCl pulp dissolu- tion. A at- or radial-ended SWEEPS tip (400 µ) is used. The pulp tissue may show different grades (levels) of inflammation, up to initial necrotic degeneration. It is important to con- sider at this stage whether the pulp tissue itself is preventing any extru- sion of the irrigant so that full-power Auto-SWEEPS activation (20 mJ at 15 Hz and 0.6 W) can be performed up to almost complete pulp dissolu- tion, which is indicated by a progres- sive decrease in bleeding. According to the tooth type and condition, this initial phase can be repeated for two to three cycles for single-rooted teeth and up to three or four cycles for pre- molars and molars. The initial irrigation phase also de- creases the bacterial load. The access cavity can now be observed under magnification (6–10x) in order to locate all canal orifices. If the orifices are not all visible, the use of ultra- sonic tips can easily discover orifices hidden under calcification in the pulp chamber. These are usually lo- cated at the angles, at the floor–wall junction and at the terminus of the root developmental fusion lines. Then pre-flaring of the orifices and enlarging of the coronal thirds of the canals allow easy and direct access to the canals. Subsequently, a direct glide path to the apical third is estab- lished by hand or dedicated rotary ÿPage A3