Abbas Ali Khademi

Periodontal healing of replanted dog teeth stored in milk and egg albumen

The type of storage medium used to store avulsed teeth prior to replantation has been shown to be a decisive factor in periodontal ligament (PDL) healing. The aim of the present study was to investigate the effect of storage medium on periodontal healing. Thirty teeth from three dogs were endodontically treated to prevent subsequent inflammatory root resorption. The teeth were atraumatically extracted and randomly stored in milk or egg albumen for 3, 6 and 10 h at 4 degrees C. All teeth were splinted for 1 weeks after replanting. After 2 months animals were sacrificed using vital perfusion-fixation and teeth were histologically prepared and evaluated following Andreasens method. It was found that teeth stored in egg albumen for 6 and 10 h had significantly higher incident of PDL healing than those treated with milk for the same period (P < 0.05). . The highest incidence of PDL healing was observed in teeth stored in egg albumen for 6 h. The least surface resorption was also evident in this group (P < 0.05). The result of this study shows that egg albumen is an excellent storage media for up to 10 h considering its likely availability at most accident sites.

Outcomes of revascularization treatment in immature dog's teeth

AIM The purpose of the current study was to examine the success rate of a revascularization treatment protocol involving canal space disinfection using copious irrigation, a triantibiotic dressing, and induction of a blood clot matrix in immature dogs teeth. MATERIALS AND METHODS Thirty-six immature mongrel dogs teeth were divided into two experimental and two control groups. The experimental groups included a necrotic-infected group (n = 20) and a vital group (n = 10). In the group with the necrotic-infected teeth, periapical lesions were induced, and disinfection of the canals was carried out using copious irrigation and a triple antibiotic medication (metronidazole, ciprofloxacin, and tetracycline). Subsequently, the periapical tissues were irritated to initiate bleeding, producing a blood clot. A double seal of the coronal access was then placed. In the vital group, the pulp was aseptically removed before the canal was irrigated and periapical tissues irritated to induce bleeding. The same protocol as that used for the necrotic-infected group was used to seal the coronal access. In the positive control group (n = 3), after pulp removal, sterile sponges soaked in plaque suspension were placed in the pulp chambers of the teeth, after which the chambers were sealed. In the negative control group (n = 3), one untouched 1st premolar tooth in each dog was assigned and left to develop naturally. Radiographic and histological findings were evaluated at 3 and 6 months. Data analysis was performed using Fishers exact test. RESULTS The necrotic-infected group radiographically demonstrated apical healing and apical closure in 70% of the cases and thickening of the walls in 40% after 6 months. The vital group showed apical closure in 77% and thickened walls in 44% of the cases after 3 months. Histological findings confirmed the radiographic findings. No significant difference was observed between the two groups (P > 0.05). CONCLUSIONS If necrotic-infected canals are effectively disinfected and treated according to the protocol, the ensuing revascularization response is similar to that of vital immature teeth.

Stability of antibacterial activity of Chlorhexidine and Doxycycline in bovine root dentine

Objective: The aim of this study was to compare the substantivity of chlorhexidine (CHX) and doxycycline bond to the dentin in diffusion disk method. Methods: A total of 92 dentin disks were prepared from Bovines teeth root. After removing cementum and standardizing disks in weight and outer diameter, they were irrigated with sodium hypochlorite 2.5%, ethylenediaminetetraacetic acid 17% and sterile saline and sterilled in autoclave. Then, the first group (n = 36) were irrigated with chlrohexine 2% and the second group (n = 36) with doxycycline 100 mg/mL, each for a period of 10 min. The third group (n = 20) was considered as the control group. Samples were divided into four subgroups, which after 1 day, 3, 6, and 12 weeks were incubated in plates containing Muller Hinton agar broth and Enterococcus faecalis for a period of 48 h at 37°C temperature; then the diameter of the zone of inhibition was measured. The antimicrobial effect of irrigating solutions without binding to the dentin was also studied using the plate well method. One-way and univariate variance tests as well as Post-hoc Tukey were used for data analyses. Findings: The diameter of the zone of inhibition of doxycycline group was significantly more than the CHX group from the beginning to the 3rd week (P < 0.005). After 3rd week, mean diameter in doxycycline group declined as compared with the CHX group up to 12th week (P < 0.005). The difference between means in two groups was not significant in the 3rd week (P = 0.87). Conclusion: The results of this study show that CHX and doxycycline show antibacterial activity for 12 weeks; although after 3rd week, the substantivity of CHX was significantly greater than doxycycline. Both of these irrigants can be used in other pharmacological and medical fields whenever a long-lasting antibacterial action is needed.

Effect of digital noise reduction on the accuracy of endodontic file length determination

Purpose The aim of the present study was to evaluate the measurement accuracy of endodontic file length on periapical digital radiography after application of noise reduction digital enhancement. Materials and Methods Thirty-five human single-rooted permanent teeth with canals measuring 20-24 mm in length were selected. ISO #08 endodontic files were placed in the root canals of the teeth. The file lengths were measured with a digital caliper as the standard value. Standard periapical digital images were obtained using the Digora digital radiographic system and a dental X-ray unit. In order to produce the enhanced images, the noise reduction option was applied. Two blinded radiologists measured the file lengths on the original and enhanced images. The measurements were compared by repeated measures ANOVA and the Bonferroni test (α=0.05). Results Both the original and enhanced digital images provided significantly longer measurements compared with the standard value (P<0.05). There were no significant differences between the measurement accuracy of the original and enhanced images (P>0.05). Conclusion Noise reduction digital enhancement did not influence the measurement accuracy of the length of the thin endodontic files on the digital periapical radiographs despite the fact that noise reduction could result in the elimination of fine details of the images.

Tissue engineering: Dentin – pulp complex regeneration approaches (A review)

Dental pulp is a highly specialized tissue that preserves teeth. It is important to maintain the capabilities of dental pulp before a pulpectomy by creating a local restoration of the dentin-pulp complex from residual dental pulp. The articles identified were selected by two reviewers based on entry and exit criteria. All relevant articles indexed in PubMed, Springer, Science Direct, and Scopus with no limitations from 1961 to 2016 were searched. Factors investigated in the selected articles included the following key words: Dentin-Pulp Complex, Regeneration, Tissue Engineering, Scaffold, Stem Cell, and Growth Factors. Of the 233 abstracts retrieved, the papers which were selected had evaluated the clinical aspects of the application of dentin-pulp regeneration. Generally, this study has introduced a new approach to provoke the regeneration of the dentin-pulp complex after a pulpectomy, so that exogenous growth factors and the scaffold are able to induce cells and blood vessels from the residual dental pulp in the tooth root canal. This study further presents a new strategy for local regeneration therapy of the dentin-pulp complex. This review summarizes the current knowledge of the potential beneficial effects derived from the interaction of dental materials with the dentin-pulp complex as well as potential future developments in this exciting field.

Effect of Polyhydroxybutyrate/Chitosan/Bioglass nanofiber scaffold on proliferation and differentiation of stem cells from human exfoliated deciduous teeth into odontoblast-like cells

Scaffolds and their characteristics play a central role in tissue engineering. The purpose of this study was to determine the effects of Polyhydroxybutyrate (PHB)/Chitosan/nano-bioglass (nBG) nanofiber scaffold made using the electrospinning method, on the proliferation and differentiation of stem cells obtained from human exfoliated deciduous teeth into odontoblast-like cells. In this experimental study, the pulps of the molten deciduous teeth were isolated, thereafter, the stem cells from human exfoliated deciduous teeth (SHED) were extracted and then the 3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the cell viability percentage. The expression of some stem cell genes was studied by flowcytometry. These cells were then subjected to odontoblast by using the bone morphogenetic proteins-2 (BMP2) growth factor in the differentiation medium and for the expression of their specific genes. Primers of collagen type-I, dentin sialophosphoprotein (DSPP) and alkaline phosphatase (ALP) were used and the percentage of differentiation to odontoblast cells in induction scaffolds was investigated using real-time PCR and immunohistochemistry methods. The results revealed a 6-fold increase in the expression of DSPP genes and collagen type-I, and a 2-fold increase in the expression of ALP in scaffold with BMP2 group compared to the scaffold as control group which according to the immunohistochemical test results, showed the extracted SHED to have been differentiated into dentin odontoblast-like cells. As a result, this scaffold can be used as a suitable substrate to apply in dentin tissue engineering.

Cytotoxicity assessment of polyhydroxybutyrate/chitosan/nanobioglass nanofiber scaffolds by stem cells from human exfoliated deciduous teeth stem cells from dental pulp of exfoliated deciduous tooth

Background: The aim of this study was to compare the cytotoxicity and the biocompatibility of three different nanofibers scaffolds after seeding of stem cells harvested from human deciduous dental pulp. Given the importance of scaffold and its features in tissue engineering, this study demonstrated the construction of polyhydroxybutyrate (PHB)/chitosan/nano-bioglass (nBG) nanocomposite scaffold using electrospinning method. Materials and Methods: This experimental study was conducted on normal exfoliated deciduous incisors obtained from 6-year-old to 11-year-old healthy children. The dental pulp was extracted from primary incisor teeth which are falling aseptically. After digesting the tissue with 4 mg/ml of type I collagenase, the cells were cultured in medium solution. Identification of stem cells from human exfoliated deciduous teeth was performed by flowcytometry using CD19, CD14, CD146, and CD90 markers. Then, 1 × 104 stem cells were seeded on the scaffold with a diameter of 10 mm × 0.3 mm. Cell viability was evaluated on days 3, 5, and 7 through methyl thiazol tetrazolium techniques (P < 0.05) on different groups that they are groups included (1) PHB scaffold (G1), (2) PHB/chitosan scaffold (G2), (3) the optimal PHB/chitosan/nBG scaffold (G3), (4) mineral trioxide aggregate (MTA), and (5) the G3 + MTA scaffold (G3 + MTA). Data were analyzed with two-way ANOVA at significance level of P < 0.05. Results: The results indicated that the PHB/chitosan/nBG scaffold and PHB/chitosan/nBG scaffold + MTA groups showed significant difference compared with the PHB/chitosan scaffold and PHB scaffold groups on the 7th day (P < 0.05). Conclusion: Thus, it can be concluded that the scaffold with nBG nanoparticles is more biocompatible than the other scaffolds and can be considered as a suitable scaffold for growth and proliferation of stem cells.

Comparative evaluation of Enterococcus faecalis counts in different tapers of rotary system and irrigation fluids: An ex vivo study

Background: Bacteria and their by-products are etiological factors for the failure of endodontic treatment. Reduction of root canal bacterial contamination is one of the chief aims of root canal therapy. The aim of this study was to compare the effects of different rotary file tapers and two irrigation fluids on Enterococcus faecalis counts. Materials and Methods: In this ex vivo study Root canals of 72 human upper lateral incisors were enlarged to ISO #20 K-file. Then, the samples were sterilized and inoculated with E. faecalis for 72 h, divided into six experimental groups and prepared with #30 Flexmaster files with 0.02, 0.04, and 0.06 tapers and two different irrigation solutions such as normal saline and sodium hypochlorite. The control group (n = 10) was subdivided into two groups with or without bacterial inoculation and no mechanical instrumentation. Cleaning efficacy was evaluated in terms of the reduction of colony forming units (CFUs). T-test, ANOVA, Duncan, and Tukey tests were applied to the groups. A significant level of α = 0.05 was set for comparison between the groups. Results: The canals instrumented with 0.06 taper exhibited greater significant reduction in CFUs compared to canals instrumented with 0.04 and 0.02 taper (P < 0.05); 0.04 taper also resulted in greater significant reduction in CFUs than 0.02 taper (P < 0.05). In addition, no significant differences were observed in E. faecalis counts between the two irrigation fluids (P > 0.05). Conclusion: Under the conditions of this study, root canal preparation with greater taper resulted in canal cleanliness and better debridement.

Nanobiomaterials in endodontics

Based on recent research in the biomedical science field, nanosized particles in the form of aggregates of small numbers of atoms/molecules lodged in nano-structured biomaterials demonstrate properties that are significantly superior compared to those of the same material at larger dimensions and measurement scales. This novelty is expected to open up new horizons in every branch of science, with endodontics being no exception. Although this branch is taking its first faltering steps, research on the use of nanotechnology techniques has swept through various treatment areas in endodontics. The superb resistance of nanomaterials to wear and fatigue is believed to bring about surface modifications in currently available rotary nickel–titanium endodontic files. Irrigation solutions, intracanal medicaments, sealers, and obturating materials might exhibit superior properties by incorporating nanoparticles and drug elutions in relation to disinfection and sealing of the root canal system. In addition, research on the use of nanoparticles in regenerative endodontics is currently under way, which might lead to improved scaffolds and more efficacious delivery of growth factors. On the other hand, nanobiomaterials are considered candidates for application in direct pulp-capping techniques, with a direct effect on the formation of dentin bridges and different types of biomaterials used in root canal therapy. This chapter reviews current knowledge and research findings as well as potential future applications of nanobiomaterials in endodontics.

Histologic evaluation of apical pulp of immature apex following extraction, surface treatment, and replantation in different storage media in dogs.

AIM This study was designed to evaluate the apical pulp of open apex teeth following extraction, surface treatment, and preservation in different storage media in dogs. MATERIALS AND METHODS Four healthy male dogs were included in this prospective animal study. In the first phase of extraction, 30 teeth were extracted atraumatically from dogs (incisors and premolars) and then randomly divided into three groups based on different types of storage media: (i) milk, (ii) HBSS, and (iii) dry storage. In milk and HBSS groups, teeth were contaminated by dogs saliva and then kept in milk and HBSS solution, respectively, for 2 h. In the third group, teeth were stored in a dry storage for 2 h. Before replantation, all teeth were soaked in 10% doxycycline. After 2 months, in the second phase of extraction, all experimental teeth were extracted (40 teeth including control group). Three longitudinal sections (3-4 mm thickness) were stained with H&E and investigated under optical microscope. Histologic evaluations were performed, and data were analyzed using Kruskal-Wallis and Fishers exact test (α = 0.05). RESULTS There was a significant difference between the milk and control groups regarding the presence of the odontoblastic layer and resorption (P = 0.04). Also, there was a significant difference between dry storage and control group in the presence of the odontoblastic layer (P = 0.02). There was no statistically significant difference in other histologic factors between different groups (P > 0.05). It was revealed that there is no significant difference between different groups regarding the intensity (P = 0.06) and the type of the inflammation (P = 0.24). Also, the hyperemia showed no significant difference between different groups (P = 0.51). CONCLUSION It was concluded that HBSS and milk are appropriate storage media. Also, it was shown that 2 h dry storage probably does not threaten the vitality of the pulp cells.