Coronal Opening Research Articles

AVALIAÇÃO TOMOGRÁFICA DO REPARO DE PERFURAÇÃO CORONÁRIA INTRAÓSSEA UTILIZANDO AGREGADO TRIÓXIDO MINERAL: RELATO DE CASO

This clinical case report shows the repair of intraosseous coronary perforation in a maxillary canine, treated with Mineral Trioxide Aggregate (MTA), through clinical evaluation and cone beam computed tomography (CBCT) after 6 and 12 months of follow-up. Case report: The perforation occurred in the second session of endodontic treatment during the preparation of the access cavity and was located in the cervical region of the vestibular wall of the pulp chamber, communicating it with the bone tissue, at the subcristal level. Immediately after the accident, the area was cleaned with 2% chlorhexidine digluconate, the perforation was sealed with MTA Angelus and the vestibular wall of the pulp chamber was sealed with composite resin. Discussion: Intraosseous coronary perforation is an accident that occurs during the coronal opening stage, characterized by communication between the pulp cavity and the periradicular tissues, including the periodontal ligament, alveolar bone and/or gingival tissue. Sealing intraosseous perforations with bioactive materials such as MTA increases the success rate of treating these perforations. However, the long-term prognosis is not yet well established in the literature and few studies have evaluated the success of treating perforations with MTA using CBCT. Conclusion: Clinical and tomographic evaluation after 6 and 12 months showed bone healing and periodontal tissue health, demonstrating success in the treatment of intraosseous coronary perforation.

RETRATAMENTO ENDODÔNTICO NÃOCIRÚRGICO EM MOLAR INFERIOR COM INFECÇÃO SECUNDÁRIA: CINCO ANOS DE ACOMPANHAMENTO

This study reported the repair of a periapical lesion after endodontic retreatment. A 42-year-old female patient was referred to an endodontic specialist for endodontic retreatment of tooth 36. Clinically, she was asymptomatic, and the periapical radiographic examination revealed radiopaque material similar to gutta percha and an inadequate filling of the canal (sub -root canal filling, in addition to a radiolucent image present in the apical region of the tooth. After anesthesia, the coronal opening was performed using ProDesign Logic RT #30/10, #.25/08, #.20 rotary instruments. /06 At that moment, the instrument fracture occurred in the mesio-lingual canal, which was removed with ultrasonic tips and a microscope. , Belo Horizonte, Brazil) at CRT. The foraminal debridement was performed with a Logic 25.01 instrument along the actual length of the tooth. Root canal filling was performed using the #30.05 single cone technique and Bio-C Sealer bioceramic endodontic cement. At the 5-year follow-up, the patient was asymptomatic and the radiographic examination confirmed complete repair of the periapical lesion.

Antimicrobial Efficacy of Simvastatin and Double Antibiotic Paste as Intracanal Medicaments: A Randomised Clinical Study

Abstract Introduction: Root canal debridement, irrigation and a microorganism-free environment are key factors in the success of root canal treatment. Intracanal medicaments are used to enhance root canal disinfection. Simvastatin is derived from lovastatin and is a semisynthetic medication. This study compares and evaluates the effect of simvastatin and double antibiotic paste (DAP) as an intracanal medicament in single-rooted teeth with apical periodontitis using colony-forming units (CFUs)/ml. Materials and Methods: Twenty-eight patients with single-rooted teeth diagnosed with apical periodontitis were selected. Under aseptic conditions, patency was gained, sterile saline solution was deposited in the canal and the first sample (S1) was collected. Cleaning and shaping were then carried out following an appropriate technique depending on the configuration of the canal. After irrigation and biomechanical preparation, teeth were randomly assigned to two different groups, and the test intracanal medicament was applied to the root canals. Coronal openings were sealed with temporary restorative cement. The second sample (S2) was collected after 7 days. The samples obtained were checked for a reduction in the bacterial load. They were incubated aerobically for 48 h, and the CFUs were calculated. The Mann–Whitney U and Wilcoxon’s signed-rank tests were used to analyse the results statistically. Results: A significant reduction in bacterial count was present after administration of the intracanal medicament. On intergroup comparison, there was no statistically significant difference in bacterial decrease between the two groups. Comparatively, the mean reduction in the bacterial count was higher in the DAP group. Conclusion: It can be concluded that DAP and simvastatin were effective in the reduction of the bacterial count in single-rooted teeth diagnosed with apical periodontitis. However, DAP demonstrated a better performance in the reduction of bacterial counts.

Endodontic Intercurrences in The Coronal Opening During The Covid-19 Pandemic: A Cross-sectional Study

Objective: This research aimed to assess the impact of the suggestion of changing the clinical moment for the installation of rubber dam isolation during the COVID-19 pandemic, during the graduation period in Faculdade de Odontologia de Pernambuco, Universidade de Pernambuco (FOP/UPE). Materials and methods: This is an observational descriptive, cross-sectional survey of a quantitative nature, which aims to identify the main impacts of the suggestion of changing the clinical moment for the installation of rubber dam isolation in endodontic procedures, which was approved by the Ethics Committee in Research of the University of Pernambuco (CEP/UPE), under allowance ethics committee number CAAE: 47786521.4.0000.5207. The population of this research consisted of FOP/UPE undergraduate students, regularly enrolled from the 6th to the 10th period, in the years 2021 and 2022, and who accomplished dental coronal opening in endodontic treatments, in the practicing clinics of the university during the pandemic period. Information was collected through a questionnaire the researchers prepared, using the online forms application named Google Forms. Results: Only 6.7% identified intercurrences during coronal opening, restricted to difficulties in accessing the pulp chamber. Conclusion: It is understood, therefore, that the suggestions for changing the endodontic care protocol related to the prior installation of rubber dam isolation to the coronal opening procedure were used and did not increase the risk of operative complications by FOP/UPE academics, in the clinics-school during the COVID-19 pandemic.

Systemic inhibition of 5-lipoxygenase by MK-886 exacerbates apical periodontitis bone loss in a mouse model

BackgroundTo investigate if 5-LO selective inhibitor (MK-886) could be used for systemic treatment of experimentally induced apical periodontitis in a mouse model.MethodsTwenty-four C57BL/6 mice were used. After coronal opening, a solution containing Escherichiacoli LPS (1.0 µg/µL) was inoculated into the root canals of the lower and upper right first molars (n = 72 teeth). After 30 days apical periodontitis was established, and the animals were treated with MK-886 (5 mg/kg), a 5-LO inhibitor, for 7 and 14 days. The tissues were removed for histopathological and histometric analyses, evaluation of osteoclast number and gene expression for receptor activator of nuclear factor kappa-B (Tnfrsf11a), receptor activator of nuclear factor kappa-B ligand (Tnfsf11), osteoprotegerin (Tnfrsf11b), tartrate-resistant acid phosphatase (Acp5), matrix metalloproteinase-9 (Mmp9), cathepsin K (Ctsk) and calcitonin receptor (Calcr). Statistical data analysis was performed using Kruskal Wallis followed by Dunn’s tests (α = 0.05).ResultsAdministration of MK-886 for 7 days exerted no effect on apical periodontitis progression compared to LPS inoculation without treatment (p = 0.3549), while treatment for 14 days exacerbated bone loss (p < 0.0001). Administration of MK-886 enhanced osteoclastogenesis signaling and osteoclast formation within 7 days (p = 0.0005), but exerted no effect at 14 days (p > 0.9999). After 7 days of treatment, MK-886 induced mRNA expression for Acp5 (p = 0.0001), Calcr (p = 0.0003), Mmp9 (p = 0.0005) and Ctsk (p = 0.0008), however no effect in those gene expression was observed after 14 days (p > 0.05).ConclusionSystemic treatment with MK-886 exacerbated LPS-induced apical periodontitis in a mouse model.

Uma nova abordagem para acesso endodôntico em dentes anteriores - estudo piloto

Abstract Introduction The coronal opening is essential, during endodontic treatment, for direct access to the root canals. Usually, in the anterior teeth, endodontic access is achieved on the palatal/lingual surface, more specifically in the cingulum region. However, the lack of observation for dental positioning can lead to some accidents and complications, such as buccal perforations, causing esthetic damage and compromising the treatment. Objective To evaluate the applicability of a new approach for performing coronal opening in anterior teeth, regarding the wear caused on the tooth crown, and to evaluate the ease of performing the new technique to minimize the risk of perforation. Material and method Ten students (n=10) from the Improvement in Endodontics program participated in the present study. Twenty artificial teeth were used, which were upper, central incisors. Each participant performed two coronal openings. First, with no guidance (Group A - Conventional Technique) and afterward, a new opening, but with guidance with the spherical diamond tip placed parallel to the long axis of the tooth (Group B - Modified Technique). Result The results showed that 90% of the participants considered the Modified Technique as having lower risk of accidents, as well as being easier for locating the pulp chamber. There was a statistical difference both in the measurement of the total area of wear and in the width, while there was no statistical difference in the height. Conclusion Preliminary data collected with the survey were satisfactory for the Modified Technique. Statistically, it showed a favorable difference in relation to the area of wear and the width. However, in height there was no statistical difference.

Mandibular morphological analysis of rats with osteoporosis and periradicular lesions

The aim of the study was to perform a morphological analysis of the effects of osteoporosis on the periodontal ligament of rats with periradicular injury. Adult rats (n = 24), of the Wistar lineage, 3 months old, were included in the study. Twelve animals were ovariectomized (group OVX) and 12 were operated by simulation (group C). One hundred and twenty days after surgery, all animals were anesthetized, and in each animal, periradicular lesion was developed in the mandibular left first molar, by making a coronal opening in the mesial fossa on the occlusal surface until the pulp was exposed. At the end of each experimental time interval (21 and 40 days after the lesion developed), the animals were sacrificed, and blood was collected to confirm the effects of castration by serum estrogen measurement. The jaws were removed and prepared for quantitative analysis of the periodontal ligament thickness, by using an optical microscope. Comparative analysis of the data was performed using the non-parametric Kruskal-Wallis and Dunn Multiple Comparison tests. A reduction in serum estrogen levels was observed in the OVX groups (p &lt;0.01), and a significant increase in the periodontal ligament thickness in Group C 21, when compared with Group OVX 40 days (p &lt;0.01), and Group C 40 compared with Group OVX 40 days (p&lt;0.01). In all samples with osteoporosis, there were signs of resorption in the alveolar bone, and significant periodontal ligament thickening in animals with longer exposure to the disease.

Influence of cervical preflaring and root canal preparation on the fracture resistance of endodontically treated teeth

BackgroundEvaluate the fracture resistance of endodontically treated teeth after cervical preflaring and root canal preparation and to assess the volume of the root canal and the amount of remaining root dentin before and after cervical preflaring.MethodsForty-four mandibular incisors were selected using micro-CT scanning and distributed into 4 groups (n = 11) according to the instrument used for cervical preflaring: control group - no cervical preflaring; Gates Glidden – burs size #2 and #3; WXN – 25.07 Navigator instrument; and Easy – 25.08 ProDesign S instrument. Coronal opening was performed, and the canals were prepared with Wave One Gold Primary and filled with an epoxy-resin based sealer and gutta-percha cones. Micro-CT scans were performed before and after root canal instrumentation. All images were reconstructed and assessed for the thickness of mesial and distal root dentin at 3 mm and 5 mm from the cement -enamel junction and for the volume of cervical portion of the canal after preparation. Fracture resistance test was performed applying compressive loads at a crosshead speed of 0.5 mm/min, applied on the palatal aspect of specimens at 135° along the long axis of the tooth. The data were analyzed using ANOVA and Tukey’s test (P = .05).ResultsCervical preflaring and canal preparation reduced the dentin thickness (P < .05) and increased the canal volume (P < .05) in all groups at 3 mm an 5 mm. Cervical preflaring with Gates Gliden burs reduced the fracture resistance of endodontically treated teeth (P < .05).ConclusionsAll instruments reduced the dentin thickness and increased the canal volume in the cervical at 3 mm and 5 mm. Gates Glidden reduced fracture resistance of mandibular incisors submitted to cervical preflaring, whereas NiTi instruments did not.Clinical relevanceCervical preflaring assumes particular importance previously to the root canal preparation because it minimizes the occurrence of operative accidents, and permits more accurate determination of working length and the apical diameter.

The effect of zinc oxide based sealer on bone defects healing

Summary Introduction Obturation as the final phase of endodontic treatment aims to provide complete hermetic filling along the entire length of the canal system from the coronal opening to the apical end. The aim of this study was to evaluate histological response of bone tissue on the implantaton of zinc oxide based material in artificially prepared defect in the mandible of rats. Material and method For the experiment, sixteen male Wistar rats were used. Using sterile steel burs a defect was made in mandible, between the midline and mental foramen. Zinc oxide based sealer was implanted in the defects of experimental group while the defects of control group healed spontaneously. One half of animals in both groups were sacrificed after thirty days, and the second half after ninety days. Microscopic preparations consisted of the defect with surrounding bone and after processing were analysed using light microscopy. Results The thirtieth day after implantation of the material, fibrovascular connective tissue was noted, with scant chronic inflammatory cell infiltrate. Away from the experimentally made defect, in the depth of the bone, lamellar bone with well-formed larger osteons was noted as well as enlarged Volkmann and Haversian canals. Ninety days after implantation of the material, there was no restitutio ad integrum, but intense focal remodelling of bone tissue was noted. Conclusion Endomethasone N slowed down bone tissue healing process by showing the signs of prolonged inflammation in bone tissue in which it has been implanted. Extension of the healing process is reflected in the slow replacement of fibrovascular connective tissue with newly formed bone tissue.

Limewater and Polymyxin B Associated with NaOCl for Endotoxin Detoxification in Root Canal with Necrotic Pulp.

This clinical study investigated the effects of endodontic treatment by using different irrigants (limewater + NaOCl and polymyxin B + NaOCl) and intracanal medication on endotoxins in teeth with primary endodontic infection and radiographically visible apical periodontitis. Thirty-three teeth with necrotic pulp and periapical lesions from different patients were selected for this study. Samples were collected after the coronal opening (S1) and after instrumentation (S2). Root canals were divided in 3 groups (n = 11) according to the irrigant combination used: NaOCl + LW: 2.5% NaOCl + calcium hydroxide solution (0.14%, limewater); NaOCl + PmB: 2.5% NaOCl + 10.000 UI/mL polymyxin B; 2.5% NaOCl (control). The third sampling (S3) was performed after ethylenediaminetetraacetic acid and the fourth (S4) after samples got 14 days with intracanal medication with 2% chlorhexidine gel + calcium hydroxide. Endotoxins (lipopolysaccharide) were quantified by chromogenic Limulus amebocyte lysate (LAL). Endotoxins were detected in all root canals after the coronal opening (S1). NaOCl + PmB group presented the greatest endotoxin reduction after instrumentation (76.17%), similar to NaOCl + LW group (67.64%, p<0.05) and different from NaOCl group (42.17%, p<0.05). After intracanal medication period (S4), there was significant increase of endotoxins neutralization. It was concluded that NaOCl + PmB promoted the greatest reduction of endotoxin levels, followed by NaOCl + LW. Intracanal medications had no significant complementary role in the reduction of endotoxins at the end of the treatment.

Effect of Simvastatin on induced apical periodontitis in rats: a tomographic and biochemical analysis

Abstract Introduction Simvastatin is one of several statins that are used to treat hypercholesterolemia, and in dentistry, few studies have attempted to associate the administration of this compound with bone repair. Objective To evaluate the effect of simvastatin on the progression of induced apical periodontitis in rats. Material and method To this end, 36 male Wistar rats were divided into 3 groups (N=12): Induced Apical Periodontitis Associated with Simvastatin Group (APSG N=12), Induced Periodontitis Apical Induced Group (APG N=12) and Negative Control Group (CG). On the first day, APG and APSG were anesthetized, and the coronal opening of the mandibular first molar was performed. For thirty days, the APSG received 6 mg of simvastatin daily via gavage. On the thirty-first day, all groups underwent blood collection and euthanasia. The jaws were removed and fixed in formalin. CT scans were performed to measure the periapical regions. In addition, the body mass and lipid profile were analyzed. The data were subjected to statistical analysis (ANOVA and Tukey’s test). Result The APG (3.42±0.65) showed the highest perimeters for the space periapical ligament, followed by APSG (1.54±0.78) and CG (0.64±0.24) (p&lt;0.05). The lipid profile revealed the effect of simvastatin on the amount of glucose, triglycerides, HDL, and VLDL (p&lt;0.05). Body mass APG showed the most weight gain (264.75±44.11), followed by CG (252.00±44.36) and APSG (245.41±42.56). The three groups showed significant differences in decreasing order (p&lt;0.05). Conclusion The use of simvastatin decreased the progression of the increasing periapical ligament space in rats.

Assessment of calcium ions diffusion and pH measurements of three intracanal medicaments through dentinal tubules (in vitro comparative study)

Objectives: The purpose of this study was to evaluate the release of Calcium ions from three intracanal medicaments [Ca(OH)2 , White Proroot MTA , Biodentine], and to measure the PH of these three materials. Materials and Methods: Forty-two single rooted permanent teeth were prepared using crown down technique with Protaper rotary files to a master apical file size 40. The canals were irrigated by using 2 ml 5.25% NaOCl for 60 seconds after each instrument change, final irrigation of canals using 5 ml of 17% EDTA for 3 minutes and 5 ml of 5.25% NaOCl for 60 seconds and finally 10 ml of saline solution. The canals were dried and the intracanal medicaments were applied according to manufacturer instruction after setting of materials, both apical and coronal openings were sealed by Cavit and a layer of Epoxy resin on it. Each root was immersed in 30 ml of deionized water. The digital pH meter was used for measuring the pH values for each root 10 times per each studied period (1, 2, 7, 15, 30, 45, 60) days; The Calcium ions release measurements were taken for each studied periods using Atomic Absorption Spectrophotometer device. The results were analyzed statistically using ANOVA (F test), a p-value &lt; 0.05 was considered as a significant. Results: The pH values for Ca (OH)2 and PMTA groups were gradually increased and need more time for increasing than the Biodentine. The pH values for Biodentine were the highest at the first day then decreased in the 2nd and 7th days, then increased over time until sixty days. The calcium ions release values were gradually increase for three medicament and its values were highest for Biodentine followed by Ca(OH)2 and finally PMTA. The differences between groups were statistically highly significant. Conclusions: Biodentine exhibited highest mean values in the calcium ions release and pH measurements than other groups and PMTA showed lowest mean values in the calcium ion release and pH measurement.

Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study.

The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

Analysis of the instrumentation time and cleaning between manual and rotary techniques in deciduous molars

The rotary instrumentation provides shorter instrumentation time with greater comfort for the patient but few studies have been conducted on primary teeth. Objective: this study compared the cleaning ability and instrumentation time between manual and rotary techniques in deciduous molars. Material and methods: a total of 15 molars were selected, submitted to coronal opening and root canal filled with India ink. After 48 hours, the teeth were divided into three groups: G1 – manual instrumentation with K files, G2 – rotary system Endowave, and G3 – rotary system ProTaper. After instrumentation, the teeth were sectioned and three blinded examiners evaluated the root canal cleaning. The mode of scores of examiners was analyzed by the Kruskal-Wallis test. The instrumentation time was recorded and the results were statistically analyzed by ANOVA. Results: the ProTaper system presented shorter instrumentation time compared to manual instrumentation (p = 0.0339). Endowave system did not present statistically significant difference in the instrumentation time compared to the other groups. There were no significant differences between groups concerning the ability of root canal cleaning (p = 0.6188). Conclusion: ProTaper system revealed shorter treatment time and similar cleaning ability compared to the other techniques, thus being indicated for deciduous teeth.

Radiological and histopathological evaluation of experimentally-induced periapical lesion in rats

ObjectiveThis study evaluated experimentally-induced periapical bone loss sites using digital radiographic and histopathologic parameters. Material and MethodsTwenty-seven Wistar rats were submitted to coronal opening of their mandibular right first molars. They were radiographed at 2, 15 and 30 days after the operative procedure by two digital radiographic storage phosphor plates (Digora®). The images were analyzed by creating a region of interest at the periapical region of each tooth (ImageJ) and registering the corresponding pixel values. After the sacrifice, the specimens were submitted to microscopic analysis in order to confirm the pulpal and periapical status of the tooth. ResultsThere was significant statistically difference between the control and test sides in all the experimental periods regarding the pixel values (two-way ANOVA; p<0.05). ConclusionsThe microscopic analysis proved that a periapical disease development occurred during the experimental periods with an evolution from pulpal necrosis to periapical bone resorption.

Effectiveness of the erbium:YAG laser and new design radial and stripped tips in removing the smear layer after root canal instrumentation

The aim of this study was to analyze in vitro the debriding ability of an Er:YAG laser system (2,940 nm) equipped with a newly designed radial and stripped tip of 400 µm diameter by scanning electron microscopy (SEM). A total of 80 single-rooted extracted human teeth were endodontically prepared with rotary instrumentation and standardized chemical irrigation using 5.25% sodium hypochlorite. At the end of mechanical instrumentation, four different final protocols were used. Group 1 was irrigated for 2 min with saline water as a control group. Groups 2, 3 and 4 were irradiated with an Er:YAG laser at 25 mJ and 15 Hz with a pulse duration of 50 μs and laser spray off using the tip in the coronal opening of the wet root canal. Different solutions and irradiation times were used: group 2 20 s, laser irradiation in sterile distilled water, wet canal; group 3 20 s, laser irradiation in 17% EDTA, wet canal; and group 4 40 s, laser irradiation in 17% EDTA, wet canal. Debridement of and smear layer removal from the apical third of root canals were evaluated by SEM. The study showed that standardized instrumentation, followed by a final Er:YAG laser irradiation in wet canals with EDTA irrigation resulted in more cleaning of the root canal walls and a higher quantity of open tubules in comparison with the traditional irrigation method.

Bilateral mandibular canines with two roots and two separate canals: case report

The mandibular canine is usually considered a single-rooted tooth with a single root canal. However, two canals and more rarely two roots may also occur. This paper reports the case of a patient with bilateral mandibular canines with two roots and two root canals. The initial periapical radiographs of the mandibular right and left canines for endodontic treatment revealed the presence of two roots in each tooth. After coronal opening, the cervical third was prepared with a SX file of the ProTaper system and root canal length was confirmed using Root ZX electronic apex locator. Root canal preparation was completed with the series of ProTaper instruments and the root canal was filled with gutta-percha and an epoxy resin-based endodontic sealer according to Tagger's hybrid technique. The final radiographs showed two well-obturated canals ending at the electronically located apexes. The 6-month posttreatment follow-up showed apparent clinical and radiographic success. Clinicians should always consider the presence of anatomical variations in the teeth during endodontic treatments. Despite the low prevalence, variations may occur in the number of roots and root canals of mandibular canines, as demonstrated in this case report.

Response of the periapical tissue of dogs' teeth to the action of citric acid and EDTA

The purpose of this study was to analyze the inflammatory response of dog's periapical tissues to 17% trisodium EDTA salt (pH 8.0) and 1% citric acid (pH 2.0). Saline was used as a control. Six adult dogs were used as the biological model of the study. The experimental units comprised 56 roots of mandibular molars (first and second) and premolars (first, second and third). After coronal opening, pulpectomy and root canal instrumentation were performed using the above-mentioned irrigating solutions. After 24 and 48 hours, the animals were euthanized and the teeth and their supporting tissues were removed and histologically processed. The sections were stained with hematoxylin and eosin and analyzed histopathologically with a light microscope at x100 magnification. The histological analysis focused on the occurrence of acute inflammatory response. The presence of swelling, vasodilatation and inflammatory cells were evaluated and the degree of inflammation was determined for each case. Data were analyzed by Fisher's exact test using the SPSS software with a confidence interval of 95% (p<0.05). 17% EDTA and 1% citric acid caused inflammatory responses in dog's periapical tissues with no significant differences to each other or to saline (control) at either the 24-hour (p=0.482) or 48-hour (p=0.377) periods. It may be concluded that the inflammatory response was of mild intensity for the tested substances.

Microbial distribution in the root canal system after periapical lesion induction using different methods

The aim of this study was to evaluate the microbial distribution in the root canal system after periapical lesion induction in dogs' teeth using different methods. Fifty-two root canals were assigned to 4 groups (n=13). Groups I and II: root canals were exposed to the oral cavity for 180 days; groups III and IV: root canals were exposed for 7 days and then the coronal openings were sealed for 53 days. The root apices of groups I and III were perforated, while those of groups II and IV remained intact. After the experimental periods, the animals were euthanized and the anatomic pieces containing the roots were processed and stained with the Brown & Brenn method to assess the presence and distribution of microorganisms. The incidence of microorganisms at different sites of the roots and periapical lesions was analyzed statistically by the chi-square test at 5% significance level. All groups presented microorganisms in the entire root canal system. A larger number of microorganisms was observed on the root canal walls, apical delta and dentinal tubules (p<0.05), followed by cementum and cemental resorption areas. In spite of the different periods of exposure to the oral environment, the methods used for induction of periapical periodontitis yielded similar distribution of microorganisms in the root canal system.

In vitro evaluation of root canal preparation using oscillatory and rotary systems in flattened root canals

Objective:The aim of this study was to evaluate the biomechanical preparation of flattened root canals using the following systems: Endo-Eze AET stainless steel oscillatory instruments (Ultradent) and RaCe rotary NiTi instruments (FKG Dentaire).Materials and Methods:Twenty extracted human mandibular incisors were randomly assigned to two groups: Group 1 - Instrumentation with oscillatory Endo-Eze AET files (oscillatory technique); Group 2 - Instrumentation with rotary NiTi RaCe files (rotary technique). The teeth were decoronated, had their apices and coronal openingssealed with sticky wax and were embedded in crystal-clear orthophtalic polyester resin. The roots were sectioned transversally with diamond discs at 10 mm (middle third) and 5 mm (apical third) from the apex and the segments were reassembled for instrumentation. The sections were photographed before and after root canal instrumentation and evaluated with respect to whether the original root canal shape was modified by instrumentation. To evaluate the differences in the root canal shape before and after biomechanical preparation, scores were given regarding the instruments touch on the intracanal walls.Results:In middle third of the root canals instrumented with the rotary system, there was a change in the original canal anatomy (p<0.05), with formation of a protuberance in the mesiodistal direction. This protuberance did not occur when the oscillatory instrumentation was used. The oscillatory system had better results in the middle and apical thirds as evaluated by Dunn’s multiple-comparison test (p>0.05).Conclusion:Under the tested conditions, Endo-Eze oscillatory system yielded the instrumentation of all flattened root canal walls, maintaining the canal original shape throughout the biomechanical preparation, and was more effective than RaCe rotary system.