Apical Pressure Research Articles

Assessment of apical pressures at different automated irrigant flow rates: an ex vivo study based on computational fluid dynamic analysis

Objective: The current study aimed at assessing the induced apical pressure at various simulated irrigantflow rates. Materials and Methods: Forty eight freshly extracted single-rooted premolars were decoronatedand prepared to size 30 0.04 taper using HY-Flex CM rotary file system and were scanned using cone-beamcomputed tomography (CBCT). The scanned images were reconstructed to three-dimensional Computer-aideddesign models (CAD) and the 3D needle was also reconstructed. Finally, simulations were done by placing the30 gauge open-ended needle 3 mm short of the working length. Results: There was a statistically significantdifference (p<0.05) among the different groups compared. 1 ml/min flow rate induced the least apical pressures(p<0.05) as compared to the other types. Conclusion: 1 ml/min flow rates induced the least apical pressureswhen open-ended needles are used for irrigation. KEYWORDSApical pressure; Computational fluid dynamic analysis; Flow rate; Irrigation; Root canal.

Comparative evaluation of shaping ability of sequential rotary, single rotary, and single reciprocating file systems in simulated curved canals using cone-beam computed tomography: An in vitro study

Comparative evaluation of shaping ability of sequential rotary, single rotary, and single reciprocating file systems in simulated curved canals using cone-beam computed tomography: An in vitro study

Apical pressures generated by several canal irrigation methods: A laboratory study in a maxillary central incisor with an open apex.

AimA laboratory study to determine the apical pressure generated by seven canal irrigation methods in an anterior tooth with an open apex.MethodologyCanal irrigation was performed on a 3D‐printed central maxillary incisor with an open apex (maximum diameter of 2.1 mm). Ultrasonically activated irrigation (UAI), sonic activation (EDDY), negative pressure irrigation (EndoVac), the self‐adjusting file (SAF) and the XP‐endo Finisher were employed at tooth length (TL), TL—1 mm, TL—2 mm and TL—3 mm. UAI was tested at three intensity levels additionally. Hydrodynamic irrigation with RinsEndo was performed in the pulp chamber, at the canal orifice, the coronal third, the middle of the canal and at TL. Er:YAG laser activation, at four frequency settings, was performed in the pulp chamber and at the orifice of the canal. The pressure of the fluid towards the canal terminus generated by activation was directly transferred to a pressure sensor with a range of 0 to 120 mmHg and a response time of ≤0.5 ms. The critical threshold for apical extrusion of the irrigant was set at 5.73 mmHg (lower limit of the central venous pressure: 5.88 ± 0.15 mmHg). Each experiment was repeated ten times. The tests were followed by descriptive analyses (maximum, mean, standard deviation, 95% confidence interval).ResultsEndoVac, the SAF, the XP‐endo Finisher, and UAI never exceeded the critical threshold at any insertion depth or intensity level. Er:YAG laser activation exceeded the critical threshold exclusively at frequency settings that varied from the manufacturer's recommendation. EDDY at TL and RinsEndo at any insertion depth exceeded the critical threshold in 100% of the measurements. EDDY at TL—1,—2, and—3 mm crossed the critical threshold in 30%, 10%, and 20% of the measurements, respectively.ConclusionsIn a simulated maxillary central incisor with an open apex, irrigation with EndoVac, Er:YAG laser activation, UAI, the SAF, and the XP‐endo Finisher generated apical pressures below the critical threshold of 5.73 mmHg. By contrast, using EDDY and RinsEndo for irrigation produced higher apical pressures that exceeded the critical threshold.

Syringe Irrigation in Minimally Shaped Root Canals Using 3 Endodontic Needles: A Computational Fluid Dynamics Study

IntroductionThe aim of this study was to compare the irrigant flow in curved root canals prepared to various apical sizes by constant-taper or variable-taper instruments during syringe irrigation with 3 endodontic needles at 2 different flow rates. MethodsTwo matched curved mesial root canals of human mandibular molars were imaged by micro–computed tomographic imaging after preparation to apical size 20, 25, and 30/.06 taper either by constant-taper or variable-taper instruments. A Computational Fluid Dynamics model was used to simulate the irrigant flow in the 2 root canals prepared to each apical size during syringe irrigation with a 30-G open-ended needle and 30-G and 31-G closed-ended needles at 0.05 and 0.15 mL/s. ResultsThe irrigant could not penetrate up to the working length in root canals prepared to apical size 20 or 25/.06 taper. The 30-G open-ended needle combined with the low flow rate allowed the irrigant to reach the working length in size 30/.06 taper root canals while maintaining a relatively low apical pressure, but the wall shear stress was very low. The 31-G closed-ended needle combined with the high flow rate also delivered the irrigant to the working length in size 30 root canals and developed higher wall shear stress, but the apical pressure was also higher. ConclusionsSyringe irrigation using 30-G and 31-G needles was compromised in minimally shaped root canals.

Apical Pressure Generated Using Conventional Syringe Irrigation in Immature Teeth-An In Vitro Study.

This in vitro study aimed to evaluate apical pressure during irrigant delivery with syringe irrigation in immature teeth with an open apical foramen. Conventional syringe irrigation was performed in a 3D-printed immature incisor. A 5 mL syringe combined with 25 G and 30 G cannulas was used. Open-ended and side-vented needle tip designs were assessed. Cannulas were placed at tooth length (TL), TL −1 mm, TL −2 mm, and TL −4 mm. The syringe plunger was moved with a force of 10 N, 20 N, 40 N, and 80 N to simulate clinical conditions. A pressure sensor measured periapical pressures during irrigation. Each experiment was repeated 10 times. Data were analyzed descriptively (maximum, mean, standard deviation, 95% CI) with the critical threshold indicative of extrusion set at 7.64 mbar. 30 G cannulas with both needle tip designs never exceeded the threshold at any TL with a plunger force of 10–40 N. At 80 N, 30 G open-ended cannulas exceeded the threshold in 10%, 30 G side-vented in 20–60% of the measurements. At any TL, 25 G open-ended cannulas and 25 G side-vented cannulas never crossed the threshold with forces of 10–20 N and 10 N, respectively. Consequently, 30 G cannulas with both designs can be recommended for irrigant delivery in immature teeth. 25 G cannulas ought to be used with caution.

Use of Negative Apical Pressure Technique for Removal of Apically Extruded Gutta-percha Fragment

The aim of this case report was to present using negative apical pressure technique for removal of apically extruded gutta-percha during retreatment procedures. A 22 year-old female patient was referred to the clinic with severe pain, swelling, and tenderness to percussion and palpation in the tooth of #26. Periapical radiograph showed previous root canal treatment of tooth #26 with incomplete root canal fillings. During retreatment procedures gutta-percha apically extruded from mesial root canal. The patient was recalled after one day. At the second session, it was observed that the swelling was increased. One of the tips for calcium hydroxide paste application was adjusted to suction of dental unit. Tip was placed into the canal as deep as possible. After a few attempts, apically extruded gutta-percha was removed and the patient was recalled after one day. At one day from the fragment removal, the swelling was decreased. Calcium hydroxide paste was placed into the canals for one week. At the fourth session, the patient was asymptomatic and the treatment was completed at this session. Keywords: gutta-percha, negative apical pressure, retreatment

Comparison of various irrigation activation procedures after post space preparation on push-out bond strength of fiber posts: an in vitro study

Aim: This study aimed to compare the effectiveness of various irrigation activation methods applied after post space preparation on the push-out bond strengths of fiber posts to root canal dentin. Materials and methods: Twenty maxillary central incisor teeth were prepared and root-filled. Following the preparation of the post spaces, the teeth were randomly allocated to 5 groups (n=4) based on the irrigation activation method. Post spaces were irrigated with 2.5% NaOCl and 17% EDTA and various irrigation activation techniques were applied in each group as follow. Group 1: conventional syringe irrigation (CSI); Group 2: manual-dynamic activation (MDA); Group 3: negative apical pressure (EndoVac); Group 4: passive ultrasonic irrigation (PUI) and Group 5: Er,Cr:YSGG laser. Subsequent to fiber post placement, the samples were transversally sectioned and push-out tests were applied for measurement of the bond strength of fiber posts. Results: Irrigation activation with Er,Cr:YSGG laser, EndoVac and PUI resulted higher push-out bond strength in comparison to MDA and CSI (P<.05). Conclusions: Irrigation activation with EndoVac, PUI and Er,Cr:YSGG laser provides superior bonding strength for fiber posts. gth for fiber posts.

Effect of apical size on apical pressure during syringe-needle and multisonic negative pressure irrigation.

Apical pressure during root canal irrigation is regarded as a key factor affecting the risk of irrigant extrusion. The aim of this study wasto examine the effect of apical size on the apical pressure by positive and negative pressure syringe-needle and multisonic negative pressure irrigation. An extracted maxillary first molar with two separate buccal roots, one palatal root and four canals was selected. The roots of the molar were fixed in a specially made apparatus to acquire the apical pressure of the four root canals separately. The apical sizes tested were from sizes 10, 30, 40, 50, 60, 70, 80, 90, 110. Multisonic negative pressure irrigation protocol was as recommended by the manufacturer (45mL/min), syringe-needle irrigation was done using 30-G side-vented needle 3mm from the working length at 5mL/min as a conventional positive pressure irrigation (SNI), and as negative pressure irrigation (NPSNI) using suction. Apical pressure by SNI was measured also at 10mL/min with an open-ended 30G needle, for the smallest and largest apical sizes. Apical pressures by SNI stayed positive, except when suction was used (NPSNI). The apical pressure by multisonic negative pressure irrigation remained negative in all situations. With increasing apical size, apical pressure by SNI decreased, whereas with multisonic negative pressure irrigation and NPSNI, it was not affected by apical size. Large apical size did not result in higher apical pressure values compared to small apical sizes.

In vitro apical pressure created by 2 irrigation needles and a multisonic system in mandibular molars.

ObjectivesThe aim of this study was to evaluate the apical pressure generated by 2 endodontic irrigation needles and the GentleWave system in mandibular molars.Materials and MethodsThe mesial and distal root canals of 12 mandibular molars were irrigated with a 30-gauge close-end needle or with a 30-gauge open-end needle. Procedures were performed in the mesial and distal canals. The GentleWave procedure and irrigation at 1 mm from the apex in the distal roots using an open-end needle were used, respectively, as negative and positive controls. The apical pressure was measured using a data acquisition pressure setup. Apical pressure exerted by the different needles in the 2 different canal types was statistically compared using 2-way analysis of variance.ResultsSignificant differences were found in the apical pressure for both needles and the canal type. The lowest values were obtained with close-end needles and in mesial canals. Negative apical pressure values were obtained using GentleWave.ConclusionsThe needle and the canal type influenced the apical pressure. The GentleWave procedure produced negative apical pressure.

Assessment of irrigant flow and apical pressure in simulated canals of single-rooted teeth with different root canal tapers and apical preparation sizes: An ex vivo study

Background:Irrigation dynamics vary in optimally shaped canals. Various factors combine to create a stress-induced environment leading to a dynamic irrigant flow.Aim:The aim of the study is to evaluate the irrigant flow and apical pressure using 30G open-ended needle in virtually created root canal model of single-rooted teeth.Materials and Methods:Sixty extracted single-rooted premolars were selected and prepared using a single rotary instrument Hyflex CM and grouped as – Group I: 30 size 0.6% taper (n = 15), Group II: 30 size 0.4% taper (n = 15), Group III: 25 size 0.6% taper (n = 15), and Group IV: 25 size 0.4% taper (n = 15). Postinstrumentation imaging was carried out using cone-beam computed tomography, and computer-aided design models were obtained. Subgrouping was done based on the nozzle position, and computational fluid dynamic analysis was carried out for the respective parameters assessed.Results:Statistical significance was elicited in all the groups at different nozzle positions analyzed (P < 0.05). A post hoc test revealed significance in the mean flow rate and flow velocity in Group I at low nozzle position (P < 0.05) as compared to others.Conclusions:30 size 0.6% tapered preparations proved efficient irrigant flow and least apical pressures at all nozzle positions.

Glide Path with Reciprocating Driven Pathfinding Instrument: Performance and Fracture Rate

IntroductionThis study assessed the number of mesial and distal canals of mandibular molars in which the R-Pilot pathfinding reciprocating instrument reached the working length (WL) during macro glide path procedure. Fracture and deformation rates were also evaluated. MethodsOne hundred fifty-six root canals of 52 teeth were scouted to the length of the apical foramen. Then the R-Pilot instrument was positioned at the canal orifice and activated. The instrument was moved by using a pecking motion and light apical pressure. This procedure was repeated in an attempt to reach the WL. The type of fracture and/or instrument deformation was assessed by scanning electron microscopy, whereas the roots with fractured instruments were scanned through micro-computed tomography. The percentage frequency distribution of fractures, deformations, and root canals in which the R-Pilot reached the WL were recorded and statistically compared by using the Pearson’s χ2 test with α = 5%. ResultsR-Pilot instruments reached the WL in 139 root canals (89.10%), and χ2 test showed a significant difference between the observed frequencies and the expected frequencies (χ2 = 95.41, P = .000). The observed frequencies of fractures (2.56%) and deformations (1.92%) were also significantly lower than the expected (fracture: χ2 = 140.41, P = .000; deformation: χ2 = 144.23, P = .000). Fractures occurred mostly at the apical and curved parts of the root canals. ConclusionsR-Pilot reached the WL in 89.10% of the root canals of mandibular molars with fracture and deformation rates of 2.56% and 1.92%, respectively.

CFD analysis on the effect of combining positive and negative pressure during the irrigation of artificial isthmuses.

Fluid dynamics generated by irrigation needles have not been deeply analyzed in root canal irregularities such as apical ramifications or isthmus where the cleaning capacity of irrigants might be compromised and hence the treatment outcome. The goal of this study was to compare the key irrigation parameters (flow pattern, irrigant velocity, apical pressure, and shear stress) between two irrigation needles and the additional effect of aspiration cannulas through computational fluid dynamics. A 3D-model consisting of two canals linked by an isthmus was modeled. The abovementioned needles irrigated the primary canal, whereas an aspiration cannula was located inside the secondary canal. Both the geometry definition and spatial discretization were carried out with ANSYS 16.2, through which six different simulations were performed: lateral exit (LE) needle, frontal exit (FE) needle, LE and cannula in crown (LEC), FE and cannula in crown (FEC), LE and cannula in middle third (LEM), FE and cannula in middle third (FEM). FE and FEM showed that the irrigation flow only passes through the isthmus in the most apical section (maximum irrigant velocity / shear stress = 8.44 m/s / 1628.44 Pa and 8.63 m/s / 1185.69 Pa, respectively). However, the remaining simulations showed the irrigation flow passing through the isthmus twice, through the most apical section first and through the upper part of the isthmus later (maximum irrigant velocity / shear stress = 8.48 m/s / 1298.24 Pa (LE), 8.61 m/s / 1261.36 Pa (LEM), 8.61 m/s / 1355.24 Pa (LEC), 8.59 m/s / 1256.87 Pa (FEC)). Furthermore, the highest velocity values were detected when aspiration cannulas were added.

Investigation of an Improved Side-Vented Needle and Corresponding Irrigation Strategy for Root Canal Therapy with CFD Method

Background and Objective: This research aimed to present an improved side-vented needle and explore its availability as well as the corresponding irrigation strategy. Methods: A CFD model was used to simulate the irrigant flow in a simplified prepared round root canal with an apical delta respectively with different needles for irrigation. The needle types include flat end-tip needle, original side-vented needle, and improved side-vented needle. Different insertion depths and inlet velocities were contrastively studied, as well as the gap size between the bulb at the end tip of the improved side-vented needle and the root canal. The study includes a total of 13 schemes. Velocity, pressure, and shear stress in the root canal were measured to contrast the internal flow-field details and irrigation efficiencies between different schemes. Results: Poor irrigation replacement appeared in the schemes without enough needle insertion no matter which kind of needle has been used, though relatively lower pressure emerged at the apical foramen. On the contrary, deepening needle insertion not only brings better irrigant replacement but also higher apical foramen pressure. The original side-vented needle tends to make lower pressure at the apical foramen and simultaneously worse irrigant replacement as compared to the flat end-tip needle. The fluid entering the apical anatomy part deceases a lot as the original side-vented needle was replaced by the improved one. The scheme using the improved side-vented needle with gap size ratio and inlet velocity respectively equaling 5.0% and 5.50m/s can be considered the best one. Conclusions: The improved side-vented needle can ensure acceptable irrigant replacement performance without leading to a high-pressure level at the apical foramen. The gap between the bulb and the wall of the root canal is very crucial for the pressure at the apical. The ideal irrigation strategy is ensuring the gap equals zero. However, it is a little hard to realize during the whole procedure of the root canal preparation except the final step. Consequently, another strategy that keeping the value of gap size ratio as small as possible such as less than 15% and simultaneously ensuring lower-velocity coming fluid, is necessary in the non-final irrigation.

Effect of Pulse Energy, Pulse Frequency, and Tip Diameter on Intracanal Vaporized Bubble Kinetics and Apical Pressure During Laser-Activated Irrigation Using Er:YAG Laser.

Objective: Er:YAG laser-activated irrigation (LAI) is an effective method of root canal cleaning, but irrigant extrusion from the apical foramen has been a concern. We aimed to analyze the effects of pulse energy, pulse frequency, and laser tip diameter on intracanal vapor bubble kinetics and periapical pressure generation during LAI with Er:YAG laser. Background: Irrigant vapor bubble kinetics are one of indices of root canal cleaning efficacy. However, few studies have compared laser pulse conditions to vapor bubble kinetics, in relation to periapical pressure. Methods: A plastic root canal model (apical diameter 0.50 mm, 6% taper, 20 mm long) was filled with distilled water, and LAI with Er:YAG laser (Erwin AdvErl Unit; 30, 50, or 70 mJ; 10, or 20 pulses per second; laser tip R200T or R600T) was performed with the end of the tip fixed at 15 mm from the root apex. The number, maximum diameter, and velocity of vapor bubbles were analyzed by high-speed video imaging. Pressure generated outside the apical foramen was measured with a pressure sensor. Results: Vapor bubble count and maximum diameter increased significantly with pulse energy, pulse frequency, and tip diameter. Vapor bubble velocity increased significantly with pulse frequency, but not with pulse energy or tip diameter. Periapical pressure increased significantly with pulse energy, pulse frequency, and tip diameter. Conclusions: The pulse frequency was the single factor that significantly affected all the examined parameters (the number, diameter, and velocity) of vapor bubble kinetics together with the periapical pressure.

Eliminación de una biopelícula intraradicular compuesta por Enterococcus faecalis y Candida albicans utilizando un sistema de irrigación de presión apical negativa

Endodontic treatment consists of the cleaning and disinfecting the root canal system, which is achieved using adequate mechanical instru-mentation and chemical irrigation. Endodontic microorganisms are present in root canals in the form of a biofilm, and their elimination ensures the success of endodontic treatment. Irrigation is a key factor contributing to the elimination of this intraconduct biofilm, and different irrigator agents and irrigation techniques, such as irrigation with negative apical pressure, a novel automated irrigation mechanism based on suction intraconduct, have been used. In this study, we evaluated the ability of a negative apical pressure system with different concentrations of sodium hypochlorite and durations to reduce the microbial load. Materials and Methods: An intraradicular biofilm composed of Enterococcus faecalis and Candida albicans was generated during twenty-one days of static culture on one hundred mesio-vestibular roots of upper molars with complex curvatures greater than 30°C, and the roots were classified in six groups with different concentrations and contact times of sodium hypochlorite. Subsequently, the reduction in the microbial load was measured with McFarland scale and the enumeration of colony forming units and was evaluated with scanning electronic microscopy. Results: We observed a significant difference in the reduction of the microbial load prior to instrumentation compared with postinstrumentation between the groups treated with 2.25% and 5.25% NaOCl for 30, 60 and 90 seconds of contact time (p&lt;0.05), but we did not observe differences in the reduction of microbial load between different contact times and concentrations of sodium hypochlorite employed (p&gt;0.05). Conclusion: Negative apical pressure is a good option for irrigation in endodontics, as it allows the passage of the irrigation fluid along the total length of the root canal and produces a better antimicrobial effect.

Positive and negative pressure irrigation in oval root canals with apical ramifications: a computational fluid dynamics evaluation in micro-CT scanned real teeth.

To compare using computational fluid dynamics (CFD) the flow pattern, irrigant velocity, apical pressure and shear stress produced by negative (MiC) and positive pressure with different types of needles (side-vented (SV), front-vented (FV) and notched (N)) at two insertion depths in the apical ramification of oval root canals. The micro-CT of a mandibular molar with an oval root canal with an apical ramification was used for computational analysis after preparation and geometric reconstruction. Geometries with the needles in two positions (1 and 3mm from WL) were created to run the simulations. Key parameters of irrigation were displayed with CFD and compared. The penetration depth of the needle in the root canal strongly influenced shear stress and apical pressure. The three needles revealed that the highest shear stress, velocity and apical pressure were 1mm from the WL and generated medium velocities. In N simulations, the fluid flow did not reach the apical ramification and the lowest shear stress values for positive pressure needles were found. The predominant axial component for FV revealed a different pattern of irrigation with high shear stress values and higher apical pressures than those exerted by other needles. SV simulations had generalized fluid flow in most of the main canal, the highest shear stress values and lower apical pressure than the threshold determined for risk of extrusion. MiC was associated with low velocity, shear stress and apical pressure. The SV needle demonstrated a combination of low positive pressure and high shear stress; while N had the lowest shear stress and FV the highest apical pressure. MiC generated fluid flow in part of the apical ramification with negative apical pressure values but low shear stress and velocity.

Negative Pressure Irrigation Presents Mineralizing Potential in Dogs' Immature Teeth with Periapical Lesion.

The objective of this in vivo study was to assess the effect of the root canal irrigation by negative and positive apical pressure on the expression of molecules that are an indicative of cell differentiation with mineralizing phenotype in teeth of dogs with incomplete rhizogenesis and induced periapical lesion. A total of 30 teeth (60 roots) were distributed into 3 groups (n=20): EndoVac®, Conventional and Control. After 90 days, the routine histotechnical procedures were performed and the sections were submitted to immunohistochemical technique for the staining of osteopontin (OPN), alkaline phosphatase (ALP) and the RUNX2 transcription factor in the apical and periapical regions of the roots. A semi-quantitative analysis of the positive immunostaining was performed and the intensity of the expression was classified in absent (0), mild (1), moderate (2), or intense (3). Scores data were statistically analyzed by the Kruskal-Wallis non-parametric test and Dunn post-test, and the significance level was set at 5%. RUNX2 immunostaining revealed that in the negative pressure group there was a significantly stronger (p<0.05) immunostaining in comparison to the control group. Regarding the OPN expression, it was not possible to detect a statistically significant difference between the groups (p>0.05). After analyzing ALP immunostaining, a statistically significant difference was observed between the groups (p<0.05), and the negative pressure group showed a markedly stronger mark immunostaining than the control group. The results of the present in vivo study allowed concluding that negative apical pressure irrigation presents mineralizing potential in immature teeth with apical periodontitis.

Intracanal Vaporized Bubble Kinetics and Apical Pressure During Root Canal Irrigation Activated by Er:YAG laser:

Intracanal Vaporized Bubble Kinetics and Apical Pressure During Root Canal Irrigation Activated by Er:YAG laser:

Numerical investigation of irrigant flow characteristics in curved root canals with computational fluid dynamics method

This study aims to provide valuable insight into the irrigation in curved root canals with CFD method. Numerical simulation of the flow originated from a side-vented or an open-ended flat needle located in the prepared root canal with two different insertion depths was performed. The distribution of velocity, wall shear stress, apical pressure, and the detailed flow structures were all evaluated. The results show that both the side port of the side-vented needle and the curved portion of the target root canal tends to make circumferentially non-symmetric wall shear stress distribution and asymmetrical streamlines. However, the impact of the root-canal curvature variation on the flow pattern is apparent only when the open-ended flat needle was selected for irrigation or the needle was inserted into the curved part of the root canal. The insertion depth and the size of the gap between the outer surface of the needle and the root canal internal wall are critical to the apical pressure, except the former is simultaneously crucial for the micro-velocity zone decreasing. Overall, the optimal method for effective irrigation in a curved root canal is the side-vented needle with the same curvature to the root canal, deeper insertion, and reasonable gap size.

Endodontic treatment of a large periapical cyst with the aid of antimicrobial photodynamic therapy - Case report

Introduction: Periapical cysts, especially those of great extension, represent a challenge for endodontics, since they are not repaired with traditional treatment. The aim of this case report was to evaluate the effectivity of antimicrobial photodynamic therapy “aPDT” when associated with calcium hydroxide Ca(OH)2 in treating such cysts. Case report: A 40-year-old female patient complained of bulging in the upper anterior region of the mouth. The clinical examination showed an extensive swollen periodontal area, painful with digital palpation, with a negative response to thermal tests on teeth 11 and 21. After traditional treatment, the canals of 11 and 21 were filled with photosensitizer methylene blue 0.005% pre irradiation time (PIT) of 5 minutes and irradiation by low power diode laser with visible red wavelength (660 nm) during 2 minutes without intervals, using an optical fiber delivering system with a helical movement from apical to cervical. Then the canal were filled with Ca(OH)2 paste for 45 days being changed each 15 days, and repeating the radiation. Results: After 45 days, the patient already had a bulging remission, with painless resistance to apical pressure in the region and signs of bone repair at the radiographic examination, and total absence of signs or symptoms. Conclusion: the association of aPDT with Ca(OH)2 paste is effective in treating of periapical lesions of great extension and avoid surgical treatment.Keywords: Antimicrobial; Calcium hydroxide; Diode Laser; Periapical cysts; Photodynamic Therapy; Root canal treatment.