Journal of Dental School, Shahid Beheshti University of Medical Sciences

Objective: The ideal time to commence orthodontic treatment is very important. In Iran, due to the widely distributed population and low number and uneven distribution of orthodontists, general dental practitioners (GDPs) play an important role in proper treatment of occlusal and functional disorders and referring orthodontic patients to orthodontists. The purpose of this study was to assess the knowledge of GDPs about the proper timing of orthodontic treatment in comparison with orthodontists practicing in Tehran.

Methods: This cross-sectional analytical study was conducted on GDPs and orthodontists practicing in Tehran, who were selected by random sampling. The questionnaire used in this survey asked for demographic information including age, sex, academic degree, work place and work experience and contained questions concerning the knowledge of clinicians regarding the proper time to commence treatment for the most common types of occlusal disorders, functional disorders, temporomandibular joint (TMJ) disorders and other orthodontic problems. The answers of both groups of participants were assessed based on the American Board of Orthodontics objective grading system (ABO OGS). Results: The results of ANOVA showed that the two groups were significantly different in terms of age (p<0.05), sex, academic degree (p<0.001), and place of work (private office, private clinic, governmental clinic) (p<0.05). The results of comparison of GDPs and orthodontists for the proper time of initiation of orthodontic treatment for occlusal, functional and TMJ disorders showed that the GDPs had significantly less knowledge in this regard.

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.

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.

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.

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).

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.

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.

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.