فهرست مطالب

Journal of Dental School
Volume:33 Issue: 3, Summer 2015

  • تاریخ انتشار: 1394/07/05
  • تعداد عناوین: 7
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  • M. Akbari, Mj. Moghaddas, Sh. Gilshan, A. Boruzi Niat Pages 189-195
    Objective
    Fiber-reinforced composite (FRC) posts have recently become more popular for restoring endodontically treated teeth because of providing esthetics, better stress distribution and lower risk of root fracture. Resistance against tensile forces dislodging the post from the root canal is a prerequisite for these posts. This study aimed to evaluate the tensile retention (strength) of intracanal glass fiber posts produced by three manufacturers.
    Methods
    In this interventional study, the crowns of 30 sound human maxillary central incisors were cut at the cementoenamel junction and the roots were endodontically treated. Post space was prepared to a length of 10mm and the specimens were divided into three groups of 10. HtCo, Anthogyr and Svenskposts were used in groups 1, 2 and 3, respectively. The posts were cemented with Panavia F2 resin cement according to the manufacturer’s instructions. Specimens were then immersed in water at 37°C for 30 days and were then subjected to 7500 thermal cycles between 5-55°C. Intracanal tensile retention (strength) was measured at a crosshead speed of 0.5 mm/min. Data were analyzed using one-way ANOVA at p<0.05 level of significance.
    Results
    The mean retention was 188.53 (15.43), 183.81 (16.37) and 192.19 (17.50) N in Htco, Anthogyr and Svensk posts, respectively. Statistical analyses showed no significant difference in this regard among groups (p=0.111).
    Conclusion
    Within the limitations of this study, retention of HtCo glass fiber posts in the root canals was similar to that of two other posts.
    Keywords: Bond strength, Glass fiber post, HtCo post, Resin cement, Retention, Thermal cycles
  • M. Hosseini Matin, M. Zare Jahromi, M. Fesharaki, M. Ostad Sharif Pages 196-204
    Objective
    In necrotic immature teeth, intra canal medicaments such as triple antibiotic paste (TAP) and calcium hydroxide (CH) are used for root canal disinfection and regeneration treatment. However, the effect of these medicaments on dental pulp fibroblasts has yet to be known. This study aimed to assess the cytotoxicity of CH and TAP against cultured human dental pulp fibroblasts (HDPFs) obtained from third molars.
    Methods
    In this in vitro study, fibroblasts were obtained from the dental pulp of two third molars. Fibroblasts were exposed to 0.1, 1 and 10 mg/mL concentrations of TAP and CH. Six samples were prepared of each medicament and fibroblast viability was evaluated after 72 hours. Data were analyzed using one-way and two-way ANOVA (p<0.001). The percentage of cell viability was calculated and the cytotoxicity of the medicament was categorized as severe (30%), moderate (30-60%), mild (60-90%) and non-toxic (>90%).
    Results
    In TAP samples, only the 10 mg/mL concentration had a significant difference with the control group in terms of the percentage of cell viability and showed moderate cytotoxicity. In CH samples, the 1 and 10 mg/mL concentrations showed significant differences with the control group and were severely cytotoxic.
    Conclusion
    Reduction in cell viability of fibroblasts by increase in concentration was significantly greater in CH compared to TAP group. Thus, in regeneration treatments, these medicaments must be used in concentrations with adequate therapeutic and insignificant adverse effects on fibroblasts.
    Keywords: Calcium hydroxide, Cytotoxicity, Dental pulp, Fibroblast, Triple antibiotic paste
  • M. Moshfeghi, A. Mirzaeipour, M. Kheirkhahi Pages 205-209
    Objective
    Taurodontism is a dental anomaly characterized by elongation of root body and apical displacement of the pulp chamber floor associated with shortening of roots and their narrowing at the cementoenamel junction (CEJ). Due to having a dilated apical one-third, these teeth may cause complications during extraction, locating canal orifices and instrumentation. This study aimed to assess the prevalence of taurodontism of permanent molars in a small Iranian population.
    Methods
    This retrospective descriptive study was conducted on 1,100 dental records of patients that were randomly selected among 5,672 records available in the archives of School of Dentistry, Shahid Beheshti University of Medical Sciences from 2000 to 2010 that met the inclusion and exclusion criteria. Teeth with extensive restorations or carious lesions were excluded. One observer evaluated all the radiographs and the teeth were classified based on the presence or absence of taurodontism. All positive cases were re-evaluated by two examiners and accurate measurements were made using a caliper according to Shifman and Chanannel criteria.
    Results
    A total of 1,184 radiographs were evaluated; of which 447 (47.7%) belonged to males and 737 (62.3%) belonged to females. A total of 5,532 first and second molars of both jaws were evaluated in these radiographs. There were 1,310 (23.7%) maxillary first molars, 987 (17.8%) mandibular first molars, 1,731 (31.3%) maxillary second molars and 1,504 (27.7%) mandibular second molars. Overall, 293 teeth had taurodontism; of which, 179 belonged to females and 114 belonged to males.
    Conclusion
    The prevalence of taurodontism in the understudy population was 6.41%. It appears that taurodontism is not as rare as it is thought to be.
    Keywords: Dentition, Molar, Permanent, Population, Taurodontism
  • Ha. Shafiee, Sh. Mohebi, N. Ameli, R. Omidvar, Ar. Akbarzadeh Pages 210-219
    Objective
    Increased enamel surface roughness following orthodontic bracket debonding leads to increased plaque accumulation and enamel decalcification. Therefore, different methods are employed to achieve smoother enamel surfaces after bracket debonding. This study compared enamel surface roughness following orthodontic bracket debonding and composite resin removal using white stone and tungsten carbide burs.
    Methods
    In this in-vitro, experimental study, 20 first and second premolars of 10-20 year-olds were collected and their crowns were mounted in acrylic blocks. Roughness of the buccal surfaces of teeth was determined by atomic force microscopy (AFM) and the brackets were bonded to the teeth. After bracket debonding, composite remnants were removed using white stone and tungsten carbide burs. Parameters of enamel surface roughness were determined by AFM and time required for composite removal was also calculated. Repeated measures ANOVA was used to assess the changes in parameters based on the time of measurement, type of bur and their interaction effect. Time required for composite resin removal by bur was analyzed using one-way ANOVA and Tukey’s multiple comparisons.
    Results
    Resin removal increased enamel surface roughness compared to the baseline values in all groups. However, no significant differences were noted between the two types of burs regarding arithmetic average of the roughness profile (Ra), the root mean square roughness (Rq) and the maximum peak-to-valley height in the sampling length (Rt) after resin removal. Time required for resin removal with tungsten carbide bur (34.2 seconds) was significantly shorter than with white stone bur (56.6 seconds)(both ps<0.0001).
    Conclusion
    Considering the similar enamel surface roughness values achieved by the two burs, tungsten carbide burs are recommended for resin removal following orthodontic bracket debonding.
    Keywords: Atomic force microscopy, Composite resin, Debonding, Enamel, Orthodontic bracket, Tungsten carbide bur, White Stone bur
  • E. Tavakoli, Ar. Davari, Zs. Javadi, M. Ghaffari Targhi Pages 220-224
    Objective
    Tooth decay is one of the most common chronic diseases in the world. After pit and fissures, enamel of proximal surface is the second region prone to rot. Bitewing images are one of the most important diagnostic tools for the detection of caries. Given the importance of accurate and timely detection of decay, the current study was aimed to evaluate the ability and skill of the final-year dental students to identify the presence and depth of proximal caries in dental bitewing radiography.
    Methods
    In this descriptive cross-sectional study 208 inter proximal surfaces among the 13 dental bitewing radiographs were selected randomly. The radiographs were evaluated by two experienced dental specialists (a radiologist and a restorative specialist) to detect inter proximal decay between teeth. These diagnoses were considered as the gold standard. The radiographs were further assessed by fourteen final-year dental students. Finally, the collected data were analyzed by SPSS-17 software using Kappa coefficient of agreement and ICC. The sensitivity and specificity values were also determined.
    Results
    The value of Kappa correlation coefficient to assess the similarity between students'' responses and gold standards was obtained as 0.28 (p<0.001). The Kappa correlation coefficient for evaluation of the precision of the data was 0.71. The sensitivity in the whole population was 0.43, while the specificity was 0.84.
    Conclusion
    According to the results obtained in this study, the performance of final year dental students to identify the presence and depth of proximal caries from bitewing radiographs was not satisfactory. Moreover, the ability to detect normal surfaces was unacceptable.
    Keywords: Bitewing, Dental students, Depth, Detection, Diagnoses, Proximal caries, Radiography
  • S. Valizadeh, E. Mohammad Rabie, Z. Azizi Pages 225-232
    Objective
    The diagnosis of vertical root fracture (VRF) in endodontically treated teeth is a clinical challenge due to lack of specific clinical and radiographic signs. Although radiographic evaluation such as CBCT is helpful, intracanal posts can produce artifacts and may impair the quality of CBCT scans. This study aimed to compare the diagnostic accuracy of different resolutions of CBCT in detection of VRF in roots with casting post.
    Methods
    Eighty extracted human premolars were under went routine endodontic procedure and cast posts were subsequently prepared. The teeth were randomly divided into two groups. The fracture lines were induced by an Instron machine in test group, while the teeth in control group had no fracture. The teeth were scanned by CBCT with two voxel resolution protocols (0.15mm and 0.2mm). Three observers assessed the scans for presence of VRF on a 5-point scale. Diagnostic accuracy indices were estimated and the difference were analyzed with the Mann-Whitney test (p<0.05).
    Results
    Probabilistic sensitivity for 0.15mm and 0.2mm resolution was 59.16 (5.2) and 46.66 (16.64), respectively. Furthermore, probabilistic specificity for 0.15mm resolution was 56.16 (15.21) and for 0.2mm was 61.66 (8.77).There were no statistical differences between different resolutions in all diagnostic values including sensitivity, specificity, positive and negative predictive values (p>0.05).
    Conclusion
    Diagnostic ability of CBCT in presence of casting posts was not influenced by system resolution. According to ALARA principle, 0.2mm voxel resolution protocol is recommended in these cases.
    Keywords: Cone Beam Computed Tomography, Post, Tooth fracture
  • S. Sargolzaei, F. Mashhadi Abbas, L. Hesami Moghadam, S. Jabbari, S. Zadsirjan Pages 233-237
    Objective
    The Ortho keratinized Odontogenic Cyst (OOC) is a rare lesion originates from dental lamina and clinically, it may be mistaken for many other odontogenic cysts and Tumors. Microscopically, It should be distinguished from KCOT because of differences in biologic behavior and histologic features. Case: An interesting case of OOC arising in the edentulous mandibular right first premolar region of a 55-year-old woman is reported. Under the initial clinical diagnosis of a residual cyst, the excisional biopsy was performed. Because of detection of an orthokeratinized epithelium lining, a definite diagnosis of OOC was made.
    Conclusion
    Microscopic examination is crucial for making the correct diagnosis of such lesions, therefore establishing patients'' prognosis accurately.
    Keywords: Bone, Jaw, Keratocyst, Odontogenic Cyst, Orthokertinized Odontogenic Cyst