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ePaper created 2015-03-10, 11:16:47 | version 1.33.01
74 — issue 1/2015 Laser Dentistry Article One of the major problems regarding intra-canal laserirradiation is the temper- ature increase at the external surface of the root. Laser light exerts a thermal ef- fect when it reaches tissue. The heat is di- rectly associated with the energy used, time and irradiation mode. An increase in temperaturelevelsabove10°Cperminute can cause damage to periodontal tissues, such as necrosis and anchylosis. Lan38evaluatedinvitrothetemperature increase on the external surface of the root after irradiation with a Nd:YAG laser under the following energy parameters: 50, 80 and 100mJ at 10, 20 and 30 pulses per second. The increase of temperature was less than 10°C. The same results were obtained by Bachman et al.,39 Kimura et al.40 and Gutknecht et al.41 In contrast to the external surface, the intra-canal temperature rises dramatically at the api- cal area, promoting effective action against bacterial contamination. For the Nd:YAG laser, 1.5W and 15Hz, are safe en- ergy parameters for temperature and morphological changes.33, 41 The primary use of the Nd:YAG laser in endodontics is focused on elimination of micro-organismsintheroot-canalsystem. Rooneyet al.42 evaluatedthe antibacterial effect of Nd:YAG lasers in vitro. Bacterial reduction was obtained considering en- ergy parameters. The researchers devel- oped different in vitro models simulating the organisms expected in non-vital, contaminated teeth. Nd:YAG irradiation was effective for Bacillus stearother- mophilus,43, 44 Streptococcus faecalis, Es- cherichia coli,45 Streptococcus mutans,46 Streptococcus sanguis, Prevotella interme- dia,47andaspecificmicro-organismresist- ant to conventional endodontic treat- ment, E. faecalis.48¯50 Nd:YAG has an antibacterial effect in dentine at a depth of 1,000μm (Fig. 5).50 Histological models were also devel- oped in orderto evaluate periapical tissue response after intra-canal Nd:YAG laser irradiation. Suda et al.51 demonstrated in dog models that Nd:YAG irradiation at 100mJ/30 pulses per second for 30 sec- onds was safe to surrounding root tissues. Maresca et al.,52 using human teeth indi- cated for apical surgery, corroborated Sudaetal.‘s51andIanamotoetal.‘s53results. Kobaetal.54analyzedhistopathologicalin- flammatory response after Nd:YAG irra- diationindogsat1and2W.Resultsshowed significantinflammatoryreductionatfour and eight weeks compared with the non- irradiated group. Clinical reports published in the litera- ture confirm the benefits of intra-canal Nd:YAG irradiation. In 1993, Eduardo et al.55 published a successful clinical case that combined conventional endodontic treatment with Nd:YAG irradiation forre- treatment, apical periodontitis, acute ab- scess and perforation. Clinical and radi- ographic follow-up showed complete healing after six months. Similar results were shown byCamargo et al.56 Gutknecht et al.57 reported a sig- nificant improvement in healing of laser- treated infected canals, when compared with non-irradiated cases. Camargo et al.58 compared in vivo the antibacterial effects of conventional en- dodontic treatment and the conventional protocolassociatedwiththeNd:YAGlaser. Asymptomatic teeth with apical radiolu- cency and necrotic pulps were selected anddividedintotwogroups:conventional treatment and laser irradiated. Microbio- logical samples were taken before canal instrumentation, after canal preparation and/orlaserirradiationandoneweekafter treatment. The results showed a significant anti- bacterial effect in the laser group com- paredwithconventionaltreatment.When no other bactericidal agent was used, it wasassumedthattheNd:YAGlaserplayed a specific role in bacterial reduction for endodontic treatment in patients. Diodes The diode laser is a solid-state semicon- ductor laser that uses a combination of gallium, arsenide, aluminium and/or in- dium as the active medium. The available wavelengthfordentaluserangesbetween 800and1,064nmandemitsincontinuous wave and gated pulsed mode using an op- tical fibre as the delivery system (Figs. 6a and b). Diode lasers have gained increas- ing importance in dentistry owing to their compactness and affordable cost. A com- bination of smear layer removal, bacterial Fig.4b Fig.4a Fig.5 Figs. 4a and b Nd:YAG laser intra-canal irradiation. Fig. 5 Nd:YAG laser irradiation, deep penetration.