فهرست مطالب

Dental Research, Dental Clinics, Dental Prospects - Volume:12 Issue: 4, 2018
  • Volume:12 Issue: 4, 2018
  • تاریخ انتشار: 1397/09/03
  • تعداد عناوین: 12
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  • Rezvan Rafatjou , Iraj Amiri , Atousa Janeshin * Pages 233-237
    Background.Stem cells isolated from human exfoliated deciduous teeth (SHED) are highly capable of proliferation and differentiation into odontogenic, osteogenic, adipose tissue and neural cells. The aim of this study was to investigate the effect of CEM cement on increasing mineralization in stem cells of exfoliated deciduous teeth. Methods.Dental pulps were isolated from extracted exfoliating primary teeth and immersed in a digestive solution. The dental pulp cells were immersed in α-MEM (modified culture medium) and 10% fetal bovine serum (FBS) was added. The culture cells were used for mineral deposit formation after the third passage. The cells were cultured in osteogenic cell culture medium in the control group and in osteogenic culture medium supplemented with CEM cement in the case group. Alizarin red staining was used to evaluate the mineral deposit formation on day 21. Statistical significance was determined with t-test. Results.Quantification of alizarin red staining showed that cells exposed to CEM cement induced more mineralized nodules (P=0.03). Conclusion.Mineral deposit formation in SHEDs was stimulated by CEM cement. Based on these data it might be suggested that CEM could improve osteoblastic differentiation.
    Keywords: Calcium-enriched mixture (CEM) cement, deciduous tooth, dental pulp, stem cells
  • Naser Sargolzaie , Mehrnaz Rafiee , Hamideh Salari Sedigh , Reza Zare Mahmoudabadi , Hooman Keshavarz* Pages 238-244
    Background
    Early bone loss due to tooth extraction can be significantly reduced by socket preservation. The aim of this study was to compare the in vivo effects of hemihydrate calcium sulfate granules (an alloplastic material) and Cerabone (a bovine-derived xenograft) on socket preservation in dogs.
    Methods
    Six male Mongrel dogs were randomly divided into 2 groups (n=3) for sacrificing and histological evaluation 4 and 8 weeks after a surgery. The second and third premolars on both sides of the lower jaw were extracted surgically. The sockets on one side were filled with Cerabone, and with calcium sulfate on the opposite side. In the slides, the ratio of the area of newly formed bone to the area of the entire cavity, and the ratio of the area of fibrous connective tissue to the area of the entire cavity were measured. The presence of inflammation was also examined. Wilcoxon signed-rank test, Sign test and McNemar test were used for statistical analyses (ɑ=0.05).
    Results
    The means of new bone proportion were 11% and 8% for Cerabone and calcium sulfate, respectively (P=0.58). The means of connective tissue proportion were 29% and 33% for Cerabone and calcium sulfate, respectively (P=0.72). No inflammatory cells were observed in the Cerabone group, although 50% of the samples in the calcium sulfate group showed inflammation (P=0.50).
    Conclusion
    The effects of calcium sulfate and Cerabone on socket preservation in dogs on bone formation, fibrous connective tissue and inflammation levels were not significantly different at 4- and 8-week postoperative intervals.
    Keywords: Animal experiment, calcium sulfate, Cerabone, dog, socket preservation
  • Seyed Hosein Tabatabaei , Mohammad Hasan Sheikhha , Mahammad Hasan Akhavan Karbasi , Sedighe Zarmehi*, Mehdi Hoseini Pages 245-251
    Background
    Our research was aimed to study p53 protein codon 72 polymorphism, a single base pair change of either arginine (Arg; CGC) or proline (Pro; CCC) that creates 3 distinct genotypes in reticular oral lichen planus (OLP) in comparison to oral SCC which is the most common oral mucosal malignancy as positive control and inflammatory fibrous hyperplasia (IFH) lesion as negative control.
    Methods
    Seventy paraffin-embedded tissue samples (30 OLP, 20 OSCC and 20 IFH) were studied. DNA was purified and amplified using allele-specific polymerase chain reaction to detect polymorphism. The final amplified products were identified using gel electrophoresis. Data were analyzed using chi-squared test and odds ratio.
    Results
    The mean ages in the OLP, OSCC and IFH groups were 43.28, 58.2 and 53.47 years, respectively, with significant differences. There were no significant differences in gender between the three groups (P=0.413); however, the differences in genotypes and alleles were significant between the three groups (P=0.021 and P=0.030, respectively). By considering IFH as a reference, the frequency of proline allele in OLP and OSCC was significantly higher than that of arginine allele (P=0.015 and P=0.028, respectively). In addition, by considering OSCC as a reference and at P=1, there were no significant differences in the frequencies of alleles between OSCC and OLP.
    Conclusion
    The results might indicate the premalignant potential of OLP, and such polymorphism might be a genetic predisposing factor for conversion of OLP to OSCC. In addition, in the subjects evaluated the proline allele was considered a risk factor.
    Keywords: codon 72, malignant transformation, oral lichen planus, p53 polymorphism
  • Arati C Koregol _Nagaraj B Kalburgi _Sireesha Kanniappa Sadasivan*_Shivaraj Warad _Apoorva Kamat Wagh _Tivin Thomas _Priya Sinha Pages 252-257
    Background
    Reactive oxygen species (ROS) are associated with the pathogenesis of inflammatory diseases and have a direct or indirect role in tissue damage constituting oxidative stress. ROS are also involved in impairment of β-cell function during development of diabetes, which leads to genetic ablation of KATP channels, triggering up-regulation of antioxidant enzymes. Several markers of lipid peroxidation, protein oxidation and DNA damage induced by ROS can be measured. Over the last decade, isoprostanes have been considered as the best markers of lipid peroxidation. The aim of this study was to determine the presence of 8-isoprostane in healthy, chronic periodontitis and chronic periodontitis subjects with type II diabetes and to find the correlation between 8-isoprostane levels among groups and with clinical parameters like gingival index, probing depth and clinical attachment levels.
    Methods
    Ninety subjects were selected and divided into 3 groups: healthy, chronic periodontitis and chronic periodontitis subjects with type II diabetes (n=30 each). Saliva was collected from these subjects after obtaining consent and analyzed for 8-isoprostane levels using ELISA kit. Statistical analysis was performed using Kruskal-Wallis test, Mann-Whitney U test and Spearman’s correlation coefficient (P<0.001).
    Results
    Statistically significant difference was found in the levels of 8-isoprostane between healthy, chronic periodontitis and chronic periodontitis subjects with type II diabetes and with all clinical parameters.
    Conclusion
    8-isoprostane can be considered as a pathophysiological marker to measure oxidative stress in periodontal diseases.
    Keywords: Antioxidant, chronic periodontitis, diabetes mellitus, isoprostanes, reactive oxygen species, saliva
  • Fahimeh Hamedirad , Tahereh Ghaffari*, Navideh Mehanfar Pages 258-263
    Background
    For esthetic considerations in anterior regions, abutments with high-strength ceramics such as alumina and zirconia have been developed as substitutes for titanium abutments. The present study was designed to investigate the distribution of stress in prosthesis and bone components of an implant-supported FPD with different abutments by using 3D finite element analysis.
    Methods
    Ceramic FPDs were made from the canine to the upper left second premolar with titanium fixtures. In order to investigate the stress distribution, forces of 100 and 300 N were applied at angles of 0, 15 and 35 degrees to the central fossa of the second premolar and pontic, as well as the cingulum of the canine crown. Force loading was static. After analyzing the mechanical properties of the materials, boundary conditions and loading were performed according to the existing averages, and subsequently, the results obtained from this analysis were analyzed.
    Results
    The highest level of stress was observed in the distal crest of the posterior implant (23.20 MPa) under lateral forces (15 and 35 degrees) in a model with both titanium abutments.
    Conclusion
    Lateral forces induced higher accumulation of stress in the implant and surrounding bone, while abutment change did not affect the distribution of stress.
    Keywords: Dental implant, implant-supported dental prosthesis, finite element analysis, stress distribution
  • Alireza Izadi , Fariborz Vafaee , Arash Shishehian , Ghodratollah Roshanaei , Behzad Fathi Afkari* Pages 264-271
    Background
    Recently, non-presintered chromium-cobalt (Cr-Co) blocks with the commercial name of Ceramill Sintron were introduced to the market. However, comprehensive studies on the dimensional accuracy and fit of multi-unit frameworks made of these blocks using the coordinate measuring machine (CMM) are lacking. This study aimed to assess and compare the dimensional changes and fit of conventional casting and milled frameworks using Ceramill Sintron.
    Methods
    A metal model was designed and scanned and 5-unit frameworks were fabricated using two techniques: (I) the conventional casting method (n=20): the wax model was designed, milled in the CAD/CAM machine, flasked and invested; (II) the milling method using Ceramill Sintron blocks (n=20): the wax patterns of group 1 were used; Ceramill Sintron blocks were milled and sintered. Measurements were made on the original reference model and the fabricated frameworks using the CMM in all the three spatial dimensions, and dimensional changes were recorded in a checklist. Data were analyzed with descriptive statistics, and the two groups were compared using one-way ANOVA and Tukey test (α=0.05).
    Results
    The fabricated frameworks in both groups showed significant dimensional changes in all the three dimensions. Comparison of dimensional changes between the two groups revealed no significant differences (P>0.05) except for transverse changes (arch) that were significantly greater in Ceramill Sintron frameworks (P<0.05).
    Conclusion
    The two manufacturing processes were the same regarding dimensional changes and the magnitude of marginal gaps and both processes resulted in significant dimensional changes in frameworks. Ceramill Sintron frameworks showed significantly greater transverse changes than the conventional frameworks.
    Keywords: CAD-CAM, Ceramill Sintron, discrepancies, fabrication techniques, fit of prostheses, frameworks
  • Cangul Keskin*, Evren Sar?y?lmaz Pages 272-276
    Background
    The present study aimed to compare the amount of apically extruded debris and irrigants produced by various nickel-titanium instruments.
    Methods
    A total of 100 single-rooted mandibular premolar teeth were root canal treated and prepared for agar gel model. The root canal fillings were removed using Reciproc Blue, ProTaper Next, R-Endo, WaveOne Gold systems or hand instrumentation. The mean weights of apically extruded materials were calculated. Data were statistically analyzed using one-way ANOVA and post hoc Bonferroni tests.
    Results
    Hand instrumentation resulted in significantly more debris and irrigants than other systems (P<0.05). The mean amount of apically extruded debris and irrigants produced by Reciproc Blue system was significantly greater than motordriven instruments (P<0.05). No significant difference was detected between ProTaper Next and WaveOne Gold systems (P>0.05), while they both produced significantly less apically extruded material than R-Endo system (P<0.05).
    Conclusion
    All the instruments caused apical extrusion. ProTaper Next and WaveOne Gold systems were associated with significantly less apical extrusion.
    Keywords: Agar gel model, apical extrusion, retreatment, nickel-titanium
  • Farzaneh Farid , Khadijeh Rostami , Sareh Habibzadeh*, MohammadJavad Kharazifard Pages 277-282
    Background
    This study investigated the effect of the thickness of two resin cements on push-out bond strength of fiber posts to root dentin.
    Methods
    Sixty decoronated single-rooted teeth were endodontically treated. The specimens were then randomly allocated to two groups (n=30); group 1: drill size 90 w, matching the size of fiber posts used; group 2: drill size 110, larger than the posts. The specimens in each group were divided into 2 subgroups (n=15); subgroup SE, in which the posts were cemented with self-etch Panavia F2.0 and subgroup SA, in which self-adhesive Panavia cement was used. After 72 hours, 2 slices with 1 mm of thickness were prepared from the mid-root of each specimen. Push-out bond strength test was performed in a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed with two-way ANOVA and t-test.
    Results
    The mean bond strengths of the posts cemented in matched-size spaces for SE and SA groups were 4.02±1.6 and 4.12±2.3 MPa, respectively. For posts cemented in oversized spaces, the values were 4.9±2.3 and 2.8±1.3 MPa, respectively. In matched-size spaces, there was no significant difference between the two groups.
    Conclusion
    The results of this study suggested that increasing the cement thickness would reduce the bond strength of fiber posts to root dentin when self-adhesive cements are used; however, self-etch adhesives were not affected.
    Keywords: Dental Adhesives, dental dowel, resin cement
  • Gül?ah Uslu , Taha ?zyürek , Mustafa Gündo?ar , Koray Y?lmaz * Pages 283-287
    Background
    The aim of this study was to compare the cyclic fatigue resistance of 2Shape, Twisted File (TF) and EndoSequence Xpress (ESX) nickel-titanium rotary files at intracanal temperature (35°C).
    Methods
    Twenty 2Shape TS1 (25/.04), 20 TF (25/.04) and 20 ESX (25/.04) files were tested for cyclic fatigue at intracanal temperature (35°C). All the instruments were rotated in artificial canals which were made of stainless steel with an inner diameter of 1.5 mm, 60° angle of curvature and a radius curvature of 5 mm until fracture occurred; the time to fracture was recorded in seconds using a digital chronometer and the number of cycles to fracture (NCF) for each file was calculated. Kruskal-Wallis test with Bonferroni correction was performed to statistically analyze data using SPSS 21.0. Statistical significance was set at P<0.05.
    Results
    NCF values revealed that the 2Shape had significantly the highest cyclic fatigue resistance, followed by TF and ESX at intracanal temperature (P<0.05). The difference was significant between the TF and ESX groups (P<0.05). There was no significant difference among the 2Shape, TF and ESX files with respect to the lengths of the fractured file fragments (P>.05).
    Conclusion
    Within the limitations of present study, it was concluded that the cyclic fatigue resistance of 2Shape files at the intracanal temperature is higher than that of TF and ESX files.
    Keywords: Cyclic fatigue, EndoSequence Xpress, Twisted File, 2Shape, static test
  • Cangul Keskin*, Duygu Hazal Güler , Evren Sar?y?lmaz Pages 288-293
    Background
    The aim of this study was to evaluate the effectiveness of different irrigation techniques in the removal of triple antibiotic paste (TAP), which was applied for 7, 21 or 90 days, from simulated root canals of immature teeth.
    Methods
    The root canal spaces of 190 maxillary canine teeth were filled with TAP and randomly divided into a control and 3 experimental groups according to the intracanal medicament period (7, 21 or 90 days). Syringe irrigation (SI), passive ultrasonic irrigation (PUI) and XP-endo Finisher (XP) were used for the removal of TAP (n=20). The amount of remaining medicament was calculated under a stereomicroscope using a 4-grade scoring system. Kruskal-Wallis H and Wilcoxon signedrank tests were used for statistical analyses (P<0.05).
    Results
    The mean percentage of residual TAP was significantly greater in the SI group compared to PUI and XP at all the time intervals (P<0.05). Paste removal efficacy of PUI was not affected by the intracanal time of TAP (P>0.05), whereas the efficacy of SI and XP was significantly affected (P<0.05). No significant differences were detected between PUI and XP at 7- and 21-day intervals (P>0.05); however, at 90-day interval, PUI removed significantly greater amount of TAP than XP did (P<0.05).
    Conclusion
    The time of the TAP in the root canal negatively affected the removal efficacy of the SI and XP-Endo Finisher; however, it did not affect the efficacy of the PUI.
    Keywords: Irrigation, passive ultrasonic irrigation, triple antibiotic paste, XP-endo Finisher
  • Sevinç Aktemur Türker*, Emel Uzuno?lu , Nuhan Purali Pages 294-298
    Background
    This study compared the effect of smear layer on the penetration depth and push-out bond strength of various root canal sealers.
    Methods
    A total of 90 extracted human mandibular premolars were assigned into 2 groups: smear layer preserved and smear layer removed. Then the roots were further divided into 3 subgroups according to the sealer tested: AH 26, BioRoot RCS and MTA Plus. Obturation was performed with gutta-percha and the relevant sealer was mixed with 0.1% rhodamine B. Three 1-mm-thick slices were obtained from the mid-third area of each root. Two slices were selected for the push-out test and the remaining slice was used to calculate the dentinal tubule penetration depth and percentage.
    Results
    The retention of MTA Plus and BioRoot RCS was higher than that of AH 26 when the smear layer was preserved (P<0.05). BioRoot RCS showed the lowest penetration depth when the smear layer was removed (P<0.05).
    Conclusion
    Dentinal tubule penetration of root canal sealers had a limited effect on their adhesion to root canal wall.
    Keywords: Calcium silicate-based sealer, confocal laser microscopy, bond strength, penetration depth
  • Les Kalman * Pages 299-303
    Implant-supported crowns remain an ideal treatment option for the replacement of a missing tooth. The provisionalization phase remains a critical step between surgery and final crown placement, guiding soft tissue healing and providing esthetics and function. Although there are several possible pathways for provisionalization, the options are time-consuming, technically difficult and expensive, resulting in confusion and frustration for the dentist and cost and time for the patient. A novel dental implant abutment has been developed that aims to resolve the shortcomings of current abutments and the provisionalization process. 3D printing or additive manufacturing, with plastic and metal, were employed as an alternative approach for production of the prototype abutment. Scanning, computer-aided design and 3D plastic and metal printing were employed. Abutments were fabricated in MED690 VeroDentPlus and Duraform 316L stainless steel, respectively. Prototypes were printed with a claimed accuracy of 16 µm (plastic) and 8 µm (metal). The prototypes were qualitatively assessed for functionality by implant threading and simulated provisionalization process in a laboratory setting. The plastic prototypes were not suitable due to threading issues and material weakness. Metal prototypes tolerated artificial tooth fabrication successfully but concerns with thread pitch and accuracy remained. 3D metal printing appears to be a suitable alternative to traditionally machined implant components; however, post-production processing seems to be required. Further research is warranted.
    Keywords: Dental implant, implant abutment, prosthodontics