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Objective: The present study evaluated the pulp tissue response following direct pulp capping (DPC) with several materials in dogs' teeth. Methods: This study was performed on four doges with 64 mature healthy premolars and molars. The teeth randomly received the following materials: platelet-rich plasma (PRP), propolis, MTA, and glass-ionomer cement (GIC, negative control group). Afterwards, the teeth were restored with light cure GIC. Half of the animals were sacrificed after seven and half after 30 days. Histologic samples were prepared (n=8 per material/interval), and the levels of inflammation, and fibrous and calcified tissue formation were compared between the groups and intervals. Results: After seven days, inflammation and calcified tissue levels were comparable among the groups (P> 0.05). The MTA group showed significantly more fibrous tissue formation than the GIC samples (P<0.05). After 30 days, propolis and MTA showed significantly lower inflammation than GIC (P<0.05). PRP and MTA groups showed significantly higher fibrous tissue formation than the GIC group (P<0.05). Moreover, GIC showed the lowest calcification level among the groups, and PRP had lower calcification than MTA (P<0.05). Inflammation levels of the experimental groups decreased after 30 days, but the change was not significant (P>0.05). Fibrous tissue formation in the MTA and propolis groups decreased significantly after 30 days (P<0.05). Calcification levels of the experimental groups increased significantly over time (P<0.05). Conclusions: The findings suggest that propolis might be a favorable substitute for MTA in DPC procedures, as it produced comparable results to MTA in reducing inflammation and enhancing calcification. [ABSTRACT FROM AUTHOR]

Background: Electrochemical disinfection of the root canal system (RCS) is introduced as an alternative to conventional irrigation. The aim of this study was to assess the efficacy of depotphoresis method in the disinfection of accessible and inaccessible RCSs. Materials and Methods: In this comparative in vitro study disinfection of Enterococcus faecalis infected RCS using two methods, (1) depotphoresis and (2) sodium hypochlorite (NaOCl) irrigation plus passive ultrasonic agitation (PUA) took place on 40 extracted maxillary anterior teeth. Decoronation was done with a diamond disc, and the canals were instrumented. The roots were divided into two phases: the specimens with canal obstruction and the specimens without canal obstruction. The smear layer was removed, and the specimens were infected for 21 days with E. faecalis. After disinfection procedures, bacterial samples were taken using two sterile #35 paper points, and colony forming units (CFU) were counted. Data were analyzed statistically using the Kruskal--Wallis test, with a significance level at P < 0.05, to indicate differences between depotphoresis and NaOCl plus PUA groups. Results: In both phases, Log CFU after depotphoresis treatment was significantly lower than NaOCl irrigation plus PUA treatment (P < 0.05). Conclusion: Treatment with depotphoresis was significantly more effective than NaOCl irrigation plus PUA treatment. [ABSTRACT FROM AUTHOR]

Background: Mineral trioxide aggregate (MTA) becomes a hard mass after setting and making it difficult to remove and can cause significant problems in the retreatment process. The aim of this study was to evaluate the effect of different concentrations of hydrochloric acid (HCl) on MTA dissolution and its effect on dentin. Materials and Methods: In this in vitro study, 45 single-root premolars were selected. Artificially open apex was created in all samples with similar process. The samples were randomly divided into 4 experimental groups of 10, and a control group of 5. Four-millimeter thick apical plugs of Root MTA were placed in all samples in an orthograde manner. HCl was used at concentrations of 3.75%, 7.5%, 15%, and 22.5% (w/v) for the experimental groups and normal saline for the control group. Each sample was exposed to the desired solution for 15 min. Then, MTA retrieval and reaching the working length were attempted with k-file # 30. The times of each sample were recorded. Furthermore, after longitudinal incision of the roots with a disc, the dentin surfaces of canals were examined with a Dino-Lite microscope (x50). Results were analyzed by Shapiro-Wilk test and one-way analysis of variance tests. The level of significance P value was set at 0.05. Results: The lowest average time of reaching working length was observed with group 22.5% that was significantly lower than 15% and 7.5% concentrations (P = 0.005 and P = 0.011). Furthermore, by examining with x50 of Dino-Lite microscope, no difference was observed on the canal walls. Conclusion: The optimum concentration of HCl was 7.5%. Furthermore, different concentrations of HCl had no significantly different effect on the dentinal canal wall using Dino-Lite microscope with x50. [ABSTRACT FROM AUTHOR]

Statement of the Problem: One of the rare adverse effects in patients who take bisphosphonates is the osteonecrosis of the jaw in the oral cavity following any trauma such as tooth extraction. Purpose: The aim of this study is the histopathological evaluation of the jaw following intra-ligament anesthesia injection in Zoledronate-treated rats. Materials and Method: In this descriptive-experimental study, rats weighing 200-250 g were divided into 2 groups. The first group received a 0.6 mg/kg dose of zoledronate and the second group received normal saline. Five injections with a 28-day interval were performed. At the end of the injection, the animals were sacrificed. Then, five-micrometer histological slides were prepared from the first maxillary molars and the surrounding tissues. Hematoxylin and eosin staining was performed to evaluate osteonecrosis, infiltration of inflammatory cells, fibrosis, and root and bone resorption. Results: There was no difference between the macroscopic and clinical features in both groups and no evidence of osteonecrosis of the jaw was observed in the samples. From the histological point of view, all the samples had normal tissues and none of them showed any evidence of inflammation, tissue fibrosis, disorder, or pathological root resorption. Conclusion: According to the histological findings, the periodontal ligament space, the bone adjacent to the roots, and the dental pulp conditions were similar in both groups. Osteonecrosis of the jaw did not develop in the rats that took bisphosphonates after intraligamental injection. [ABSTRACT FROM AUTHOR]

The housing sector is an important part of every community. It directly affects people, constitutes a major share of the building market, and shapes the community. Meanwhile, the increase of developments in hazard-prone areas along with the intensification of extreme events has amplified the potential for disaster induced losses. Consequently, housing recovery is of vital importance to the overall restoration of a community. In this relation, recovery models can help with devising data-driven policies that can better identify pre-disaster mitigation needs and post-disaster recovery priorities by predicting the possible outcomes of different plans. Although several recovery models have been proposed, there are still gaps in the understanding of how decisions made by individuals and different entities interact to output the recovery. Additionally, integrating spatial aspects of recovery is a missing key in many models. The current research proposes a spatial model for simulation and prediction of homeowners' recovery decisions through incorporating recovery drivers that could capture interactions of individual, communal, and organizational decisions. RecovUS is a spatial agent-based model for which all the input data can be obtained from publicly available data sources. The model is presented using the data on the recovery of Staten Island, New York after Hurricane Sandy in 2012. The results confirm that the combination of internal, interactive, and external drivers of recovery affect households' decisions and shape the progress of recovery. [ABSTRACT FROM AUTHOR]

Although postdisaster housing recovery is an important player in community recovery, its modeling is still in its infancy. This research aims to provide a spatial regression model for predicting households' recovery decisions based on publicly available data. For this purpose, a hierarchical Bayesian geostatistical model with random spatial effects was developed. To calibrate the model, households' data that were collected from Staten Island, New York, in the aftermath of Hurricane Sandy were used. The model revealed that on the scale of census tract, residents with higher income or larger household size were significantly less likely to reconstruct. In contrast, odds of reconstruction rose with increase of long‐term residents. The model outputs were also employed to develop a reconstruction propensity score for each census tract. The score predicts probability of reconstruction/repair in each tract versus others. The model was validated through comparison of the propensity scores with the distribution of Community Development Block Grant Disaster Recovery assistance and its resultant reconstruction. The validation indicated capability of the model to predict the potential hotspots of reconstruction. Accordingly, the propensity score can serve as a decision‐support tool to tailor recovery policies. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this study was to evaluate the changes of canal configuration in simulated type II root canals that were instrumented by two different techniques using ProTaper Universal rotary files. Methods and Materials: Sixty simulated type II root canal in resin blocks were made and randomly divided into two groups. Pre and post-instrumentation images of resin blocks were prepared using stereomicroscope from three surfaces of blocks included two longitudinal section (mesiodistally and buccolingually), and one cross sectional surface. In the first group (G1) the straight canal was instrumented to the working length and the other canal was instrumented up to the area of canals junction. In second group (G2) both canals were instrumented to working length. The superimposed pre and post instrumentation images were assessed by the Adobe Photoshop software. The degree of transportation, centering ability, perimeter, surface and aspetic ratio (AR) in cross section and longitudinal section at apex, 3 mm and 5 mm above the apex, were measured. SPSS software, t-test and Mann-Whitney test were used for statistics analysis. Result: In mesiodistal direction, canal transportation was more (P=0.024) only in junction point in G2 which both canals were instrumented to working length. Also, surface changes were more significant (P=0.02) in G2 in cross sectional direction. The other parameter and also apical transportation had not significant difference in two groups. Conclusion: According to the results of this study, it can be concluded that both two preparation methods of type II canals can be used by rotary instruments. [ABSTRACT FROM AUTHOR]

Tricho-Dento-Osseous syndrome is a rare autosomal dominant disorder. Immunosuppressive drugs, though critical to the treatment, have undesirable effects on patient's healing process. This is a case report of a 10-year-old female, suffering from Tricho- Dento-Osseous syndrome who was under treatment with penicillamine. As the dental treatment was sought too late, both central and lateral incisors on the right side of mandible had severe enamel hypoplasia and tooth necrosis was evident. A large lesion was found in anterior mandible. After proper treatment of the teeth with appropritately considering the systemic condition of the patient, the favorable result was achieved. [ABSTRACT FROM AUTHOR]

Objective: Pulp regeneration within the root canal of necrotic teeth is considered an ideal treatment to allow for continued root development and recover teeth vitality. This study aims to evaluate the inductive effect of platelet-rich plasma (PRP) on expression of angiogenesis factors and pulpal revascularization of immature necrotic teeth. Materials and Methods: In this experimental animal study, we randomly divided 28 immature premolars from two mixed breed dogs into four groups, two experimental, negative and a positive control. Premolars in negative control group were left intact to develop normally. In the positive control and experimental groups, we removed the pulps and induced pulp necrosis, after which the chambers were sealed. Then, we applied the revascularization protocol in the experimental teeth located in the right quadrant. Two months later, the same protocol was applied to the left quadrant. The root canals were disinfected by irrigation with sodium hypochlorite (NaOCl) solution and application a triple antibiotic past. Following the induction of a blood clot (BC) inside the canal space, the coronal portion of the canals was assigned to either of two experimental groups: group 1 [BC+PRP+ mineral trioxide aggregate (MTA)], group 2 (BC+MTA). Access cavities were sealed with a Glass Ionomer. The jaws that held the teeth were processed for histologic analysis of newly formed tissue and immunohistochemical evaluation according to vascular endothelial growth factor (VEGF) and factor VIII expressions in the canals. Results: Histological analysis demonstrated no significant difference in the formation of new vital tissue inside the root canals between groups1 (42.8%) and 2 (43.5%, P>0.05). Based on immunohistochemical evaluation, micro-vessel density (MVD) of the granulation tissues in both groups were similar and were higher compared with the normal pulp. We observed strongly positive expressions of VEGF and factor VIII in the stromal and endothelial cells, with severe intensity after one month. Both factors showed downregulation at three months postoperative. Conclusion: PRP could not increase the formation of new vital tissue. The immunohistochemical results showed that VEGF and factor VIII played a pivotal role in the formation of new vessels inside the root canals of immature, non-vital teeth. [ABSTRACT FROM AUTHOR]

Background: Apical leakage assessment is a way to compare the efficiency of a filling material to seal the apical region of the tooth. Many microleakage testing techniques have been introduced through the years, but there has been no agreement as to which technique gives the most accurate results. The aim of this study was to compare the accuracy of fluid filtration and bacterial leakage techniques in the assessment of the apical sealing ability of mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM). Materials and Methods: A sample of 34 extracted single-rooted human teeth were selected and prepared. The samples were divided in to 2 experimental groups. The apical 3 mm of each root was resected at 90° to its long axis and root end preparation was done with ultrasonic tips to a depth of 3 mm and filled with MTA and CEM, respectively. Assessment of apical sealing ability was done with fluid filtration technique and bacterial leakage technique along 90 days with Enterococcus faecalis bacteria. Mann-Whitney U-test and Chi-square test were used to analyze the data using SPSS (SPSS Inc., Chicago, IL, USA). P less than 0.05 was considered as signifi cant. Results: There was no significant difference in apical sealing ability between MTA and CEM in bacterial leakage and fluid filtration techniques. Samples which had bacterial leakage showed higher leakage values by fuid filtration technique. Conclusion: Both techniques showed same results and there was no significant difference between fluid filtration and bacterial leakage techniques in assessment of apical microleakage. [ABSTRACT FROM AUTHOR]

Introduction: Endodontic treatment in pulpless immature teeth is challenging due to the lack of an apical stop. Insertion of an apical plug is an alternative to conventional long-term apexification with calcium hydroxide. The aim of this study was to compare the apical microleakage of mineral trioxide aggregate (MTA) and calcium-enriched mixture (CEM) cement as apical plugs with three different obturation techniques. Methods and Materials: This experimental study was conducted on 130 single rooted human teeth with one canal. Samples were randomly divided into 2 experimental groups (n=60) and two negative and positive control groups containing 5 samples each. After cleaning and shaping, an open apex configuration was prepared in all samples. MTA or CEM cement apical plugs with 5 mm thicknesses were placed. Then, each group was divided to 4 subgroups and the remaining space of root canals were filled with either lateral compaction or thermoplasticized injectable guttapercha or was obturated by filling the entire canal with apical plug material. In one remaining subgroup the canal space was left unfilled. Microleakage was measured by the fluid filtration method and results were analyzed by means of the two-way ANOVA test. Results: There were no significant differences between microleakage of MTA and CEM cement apical plugs (P=0.92). The difference between three obturation methods was not significant, either (P=0.39). Conclusion: MTA and CEM cement have similar sealing ability as apical plugs and no significant difference was found in microleakage of the three groups. [ABSTRACT FROM AUTHOR]

Objective: There is some concern that root resection may alter the seal of the previously set orthograde material. The aim of this study was to evaluate the apical sealing ability of orthograde mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM) plugs after resection of the roots. Materials and Methods: The fluid filtration method was carried out on a total of 51 roots in three experimental (n=15) and two control (n=3) groups. The root canals were prepared 3 mm shorter than the working length. In groups A and B, 4 mm of MTA and CEM were placed in an orthograde technique, respectively, and after setting, 3 mm of the root end was resected. In group C, the apical 3 mm of each root was resected, root end preparation was carried out to a depth of 3 mm and filled with MTA. Apical microleakage values of each group were measured. Data was analyzed using Kruskal-Wallis test. Results: Means and standard deviations of apical microleakage in groups A (MTA orthograde), B (CEM orthograde) and C (MTA retrograde) were 2.31×10-4 (0.32×10-4), 3.33×10-4 (0.29×10-4 ) and 4.42×10-4 (0.40×10-4 ) μl.min-1 .cmH2O-1 , respectively. The mean values were greater in group C; however, statistical analysis revealed no significant differences between these groups (P>0.05). Conclusion: Based on the results of this study, when there is an orthograde access to the root canal and surgery is likely to be necessary in the future, MTA and CEM can be placed in an orthograde technique and it just resects the root during surgery. [ABSTRACT FROM AUTHOR]

Background: The aim of the present study was to investigate the quality of root canal obturation performed by 6th year undergraduate dental students at the Dental School, University of Mashhad, Iran. Materials and Methods: A random 200 sample records of patients who received endodontic treatment at the Dental School, University of Mashhad between 2009 and 2010 was investigated. The quality of root canal filling was determined in relation to the adequate density and length of root fi lling. Statistical analysis of the data was carried out using statistical package for the social sciences (SPSS 12.0, SPSS Inc., Chicago, IL, USA) with Chi-square test. P < 0.05 was considered as significant. Results: About 38% of teeth fulfilled the criteria of an acceptable root canal filling. Adequate length and density of root filling was found in 73% and 66% of teeth respectively. There was significant difference between maxillary and mandibular teeth according to the quality (P = 0.009), length (P = 0.039) and density (P = 0.005) of root filling. The frequency of root canals with an “acceptable” filling was significantly greater in the anterior teeth than in molars. Conclusion: The technical quality of root canal treatment performed by undergraduate dental students was found to be less than ideal. Thus, the training course of the students at the preclinic and clinic has to be revised. [ABSTRACT FROM AUTHOR]

Introduction: There is a direct relationship between the quality of root canal obturation and success of endodontic therapy. The aim of the present study was to assess the quality of canal obturation performed by undergraduate dental students at the Faculty of Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. Materials and Methods: Records of 200 endodontically treated teeth from patients who were visited by undergraduate students between 2009 and 2010, at the Endodontic department, Faculty of Dentistry, Mashhad University of Medical Sciences, were randomly selected for evaluation. Periapical radiographs of all treated teeth were assessed in terms of canal obturation quality (i.e. adequate density and length). Statistical analysis of data was carried out using SPSS software and chi-square test. The Statistical significance level was set at P=0.05. Results: Forty-five percent of teeth fulfilled the criteria of an acceptable root canal obturation. Adequate length and density of root filling was found in 89% and 34% of teeth, respectively. There was a significant difference between maxillary and mandibular teeth regarding the length of root canal obturation (P=0.004). A significant difference was observed between molars and other tooth types. The frequency of root canals with an acceptable filling was significantly greater in the anterior teeth compared to premolars or molars. Conclusion: The technical quality of root canal treatment performed by undergraduate dental students was found to be less than ideal. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this in vitro study was to determine the sealing ability of orthograde ProRoot mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM) cement as root-end filling materials. Materials and Methods: Fifty four extracted single-rooted human teeth were used. The samples were randomly divided into 3 experimental groups. In group A and B, 4 mm of WMTA and CEM cement were placed in an orthograde manner and 3 mm of apices were resected after 24 hours. In group C the apical 3 mm of each root was resected and the root-end prepared with ultrasonic tips to a depth of 3 mm and subsequently, then filled with MTA. The apical sealing ability was performed with bacterial leakage method. Statistical analysis was carried out with Chi-square test. Results: There were no significant differences in the extent of bacterial leakage between the three experimental groups (P>0.05). Conclusion: Based on the limitations of this in vitro study, we concluded that MTA and CEM cement can be placed in an orthograde manner when there is a potential need for root-end surgery. [ABSTRACT FROM AUTHOR]

Objective: There is some concern that root resection may alter the seal of the previously set orthograde material. The aim of this study was to evaluate the apical sealing ability of orthograde mineral trioxide aggregate (MTA) and calcium enriched mixture (CEM) plugs after resection of the roots., Materials and Methods: The fluid filtration method was carried out on a total of 51 roots in three experimental (n=15) and two control (n=3) groups. The root canals were prepared 3 mm shorter than the working length. In groups A and B, 4 mm of MTA and CEM were placed in an orthograde technique, respectively, and after setting, 3 mm of the root end was resected. In group C, the apical 3 mm of each root was resected, root end preparation was carried out to a depth of 3 mm and filled with MTA. Apical microleakage values of each group were measured. Data was analyzed using Kruskal-Wallis test., Results: Means and standard deviations of apical microleakage in groups A (MTA orthograde), B (CEM orthograde) and C (MTA retrograde) were 2.31×10(-4) (0.32×10(-4)), 3.33×10(-4) (0.29×10(-4)) and 4.42×10(-4) (0.40×10(-4)) μl.min(-1).cmH2o(-1), respectively. The mean values were greater in group C; however, statistical analysis revealed no significant differences between these groups (P>0.05)., Conclusion: Based on the results of this study, when there is an orthograde access to the root canal and surgery is likely to be necessary in the future, MTA and CEM can be placed in an orthograde technique and it just resects the root during surgery.

Introduction: Disinfection and subsequent obturation of the root canal space require adequate mechanical enlargement of the canals. The purpose of this in vitro study was to compare the shaping ability of Mtwo, RaCe and Medin rotary instruments during the preparation of curved root canals., Materials and Methods: Sixty mesiobuccal root canals of mandibular molars with severe curvatures between 25-35(°) and radius of 4-9 mm were randomly divided into three groups of 20 canals each. Using pre- and post-instrumentation radiographs, straightening of the canal and the apical transportation were determined with AutoCAD software. The data were analyzed using Chi square, analysis of variance, and post-hoc tests and the significance level was set at P<0.05., Results: Mtwo instruments maintained the canal curvature significantly better than Race and Medin instruments (P<0.05). There was significant difference between the rotary instruments for iatrogenic transportation of the major foramen (P>0.05)., Conclusions: Under the conditions of this in vitro study, Mtwo instruments seemed superior to the two other rotary instruments.

Introduction: Many patients suffer from mild, moderate or severe pain during or after root canal therapy. Theoretically, post-operative pain control can be achieved by using long-acting local anesthetics. The aim of this study was to evaluate the efficacy of a long acting anesthesia, bupivacaine, on preventing post-operative pain associated with endodontic treatment, and to compare it with lidocaine., Materials and Methods: This study was a double blind and randomized clinical trial on 30 patients' anterior maxillary teeth. The patients were divided into two groups of fifteen. One group was administered lidocanine (2% with 1:100000 epinephrine) local anesthesia and the other group was given bupivacaine (0.5% without epinephrine). The pain in patients were compared using the visual analogue scale (VAS) at definite times i.e. before treatment, during treatment and 2,4,6,8,10,12,24,36 and 48 hours after operation. Data were analyzed using One-way ANOVA tests., Results: Bupivacaine significantly decreased postoperative pain compared to lidocaine. Postoperative pain was directly related to preoperative pain. Women reported more pain, though significant difference in postoperative pain report was not found between different ages., Conclusion: In conclusion, a single dose of bupivacaine 0.5% used in infiltration anesthesia could be more effective in reduction or prevention of post-operative endodontic pain compared with lidocaine.

Introduction: This study compared the cleaning efficiency of Mtwo, Race and Medin Nickel-Titanium (NiTi) rotary instruments., Materials and Methods: Sixty mandibular molar mesial roots were selected with angle curvatures between 25-35 degrees and divided into three groups; each containing 20 teeth. Canals were prepared with the rotary files and irrigated with 2.5% NaOCl solution after each instrument. Total of 5mL of normal saline was used as the final rinse; subsequently the canals were dried with paper points. The amount of debris and smear layer in three parts of the root canal walls was evaluated using SEM and the data were analyzed by using the Kruskal-Wallis test and the Mann-Whitney U test., Results: The results for remnant debris in the coronal part of root canals were similar, whereas in the middle third, Mtwo instruments achieved significantly better results compared to Race and Medin instruments. In the apical third of the root canals more debris was created by Race instruments., Conclusion: Overall, Mtwo instruments had greater success in producing clean canals.

Introduction: The aim of this study was to compare centering ability and dentin removal of three rotary systems in curved root canals of extracted teeth., Materials and Methods: Sixty root canals of mandibular first molars with curvatures ranging between 25-35(o) were divided into three groups of 20 teeth each. Based on pre-instrumentation radiographs that assessed the angle and the radius of canal curvatures, teeth with curvatures were equally spread between the three groups. The root canals were sectioned horizontally at two levels before preparation and then remounted onto the muffle. All root canals were prepared using a low-torque control motor with Mtwo or Medin or Race instruments. Cross sectional images were obtained before and after instrumentation. Cross-sectional area and centering ability were evaluated. The data were analyzed using the one-way ANOVA and Tukey tests., Results: Neither instrument fracture nor permanent deformation occurred during preparations. The best centering ability was obtained by Mtwo instruments compare to Race and Medin instruments. In the coronal and middle sections, Mtwo removed less dentin than Race and Medin; while the difference in the apical section was not significant., Conclusion: Under the conditions of this study, the debridement of root canals was more conservative with Mtwo. The canals prepared with these instruments were better centered in all three regions of the root.

Introduction: Open-apex teeth with irreversible pulpitis require complex and difficult treatment. Providing the right environment for apexogenesis and pulp protection is vital for their long term prognosis. The young pulp of open apex tooth, however, is better equipped against irritation and assault. The aim of this study was to evaluate pulp inflammation in open apex canine teeth of cats., Materials and Methods: In this in vivo study, twelve cats with open apex canines were used. Pulps were iatrogenically exposed and the animals were sacrificed at one, seven, thirty and ninety days after pulp exposure. Samples were prepared for histological evaluations., Results: During the first and seventh day, changes were limited to acute inflammation in the coronal pulp. During the first month pulp changes in 45.5% of samples were similar to the seventh day. In the other samples necrosis and abscess spread to the end of the root, and internal resorption and periapical abscess were observed. In 45.5% of samples in the apical region vital tissue was barely observed (during 90 days); in 54.5% of samples however, complete pulp necrosis, internal resorption and a large periapical lesion was observed., Conclusion: In one and seven-day periods pulp tissue was vital, however, in the thirty and ninety-day periods, minority of the pulp samples were vital.

Introduction: Apexogenesis is a way to save vitality of open apex damaged teeth with mild or moderate pulp involvement. Such teeth are not repaired through normal and usual treatments. This treatment provides usual and physiological conditions for root to develop in normal length. The aim of this study was to determine the success rate of apexogenesis according to the duration of pulp exposure., Materials and Methods: In this animal study, mineral trioxide aggregate (MTA) and calcium hydroxide (CH) were used. The examined teeth were canines of cats with open apices. The treatment was accomplished in three periods of 1, 3, and 6 weeks after pulpal exposure. Four months later, the results were evaluated histologically and radiographically., Results: The results showed no significant difference between the success rate of MTA and CH. Besides, after 6 weeks of pulpal exposure the treatment was successful. Root development and apical closure was detected in approximately 42% of teeth, while 33% of samples had a healthy Hertwig's sheath., Conclusion: The findings of this study suggested that the conservative treatment in traumatized teeth after 1.5 month of pulpal exposure could be successful.