Vol 14, No 3 (2017)
Original Article
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Objectives: This study sought to assess the root morphology and root canal anatomy of the maxillary first and second molars in an Iranian population using cone-beam computed tomography (CBCT).
Materials and Methods: Sound fully-developed maxillary first (n=345) and second (n=423) molars were evaluated on 450 CBCT scans ordered for pre-operative assessment for implant placement. The (I) number of roots and their morphology (II) number of canals per root, (III) canal configuration and presence of a second mesiobuccal canal according to the Vertucci’s classification and (IV) unilateral or bilateral occurrence of a second mesiobuccal canal (MB2) were evaluated.
Results: Single roots were found in 1.1% of the first and 11.3% of the second molars. Four separate roots were identified in 0.5% of the first molars; none of the second molars had four separate roots. First and second molars showed a higher prevalence of three separate roots of mesiobuccal, distobuccal and palatal with one canal in each root (54% and 86 %, respectively). The most common anatomical variation in the maxillary first molars was related to the configuration of the MB root; the root canal system of the maxillary second molars showed more anatomical variations.
Conclusions: Mesiobuccal roots of the maxillary molars had more variations in their canal system than the distobuccal or palatal roots. The root canal configuration of the maxillary second molars was more diverse than that of first molars; CBCT enhances mapping of the mesiobuccal root canal system with the potential to improve the quality of root canal treatment. -
Objectives: This study aimed to assess and compare the microleakage of two bulk fill and one conventional composite in class II restorations of primary posterior teeth.
Materials and Methods: This in vitro, experimental study was conducted on 60 primary mandibular second molars, which were randomly divided into three groups. Standard class II cavities were prepared in teeth and restored with 3M bulk fill composite in group 1, SonicFill bulk fill composite in group 2 and Z250 conventional composite in group 3. Single Bond 2 bonding agent was used in all cavities. The teeth were then thermocycled and immersed in 1M silver nitrate solution. The teeth were then mesiodistally sectioned and evaluated under a stereomicroscope at´10 magnification. Dye penetration depth was recorded in microns and data were analyzed using one-way ANOVA.
Results: The mean (± standard deviation) dye penetration depth in the gingival margins was 543±523µm, 343±290µm and 597±590µm for 3M bulk fill, SonicFill and Z250 conventional composite, respectively. These values were 214±93µm, 302±127µm and 199±145µm in the occlusal margins, respectively. The three groups were not significantly different in terms of occlusal or gingival microleakage (P>0.05), but gingival margins showed significantly higher microleakage than occlusal margins in all three groups (P<0.05).
Conclusions: Bulk fill composites are not significantly different from conventional composites in terms of microleakage. -
Objectives: The frequency of non-odontogenic lesions of the jawbones is lower than that of odontogenic lesions; however, study of the epidemiologic data of these lesions is required for health care programs. This study aimed to assess the relative frequency and demographic profile of non-odontogenic jaw lesions in an Iranian population over a 30-year period.
Materials and Methods: This archive review was performed using demographic and biopsy information of all patients with non-odontogenic lesions of the jawbones submitted to the Oral Pathology Department of Dental School of Tehran University of Medical Sciences from 1984 to 2014. Demographic data included in the study were: age at diagnosis, gender and location of lesion. The lesions were divided into three groups of group 1: cystic lesions, group 2: tumors and tumor-like lesions, and group 3: infectious/ inflammatory/reactive lesions. Frequency and clinical data were analyzed using SPSS 22.
Results: Of 972 non-odontogenic jaw lesions, the ratio of mandibular to maxillary lesions was 1.63:1. Female to male ratio was 1.33:1 and the mean age of patients was 29.09±16.90 years. The most common non-odontogenic jaw lesion was central giant cell granuloma (CGCG). In groups 1, 2 and 3, nasopalatine duct cyst, CGCG, and osteomyelitis were the most frequent lesions, respectively.
Conclusions: Non-odontogenic lesions of the jawbones are a diverse group of lesions with different frequency and behavior. This study demonstrated that tumors and tumor-like lesions of the jaws were more common than cystic and infectious/ inflammatory/reactive lesions. Overall, the most common non-odontogenic jaw lesion was CGCG. -
Objectives: The practice of dentistry has long been associated with high levels of occupational stress and anxiety and music has been shown as a method of reducing stress. Considering the reportedly high level of stress among dental students and its consequences and also considering the positive effect of music therapy, the aim of this study was to evaluate the relationship between music practice and level of stress in dental students.
Materials and Methods: In this analytical, cross-sectional study, 88 students, including 44 with a history of music practice and 44 matched controls without music practice who met the defined inclusion criteria, participated. Upon obtaining written informed consent, all volunteers filled the Beck anxiety inventory (BAI) and Beck depression inventory (BDI) questionnaires. Data were analyzed using the Kolmogorov-Smirnov test, and multiple linear regression test with backward method was used to evaluate the effect of demographic factors on anxiety and depression scores.
Results: The level of anxiety was higher in students who did not have music practice and this difference was significant (P<0.001). The same was observed for depression (P=0.027). Other factors including age, gender, and being far from family had no significant effect on depression and anxiety (P>0.05). But level of anxiety and depression was higher in students of universities with tuition fee compared to free public institutes (P<0.05).
Conclusions: It may be concluded that music practice can reduce anxiety and depression of dental students. -
Objectives: Many studies have evaluated re-etched enamel by using scanning electron microscopy (SEM); however, there is no evidence regarding the use of Erbium-doped yttrium aluminium garnet (Er:YAG) laser at primary and secondary bonding instead of acid etching with regards to enamel surface changes. The purpose of the present study was to determine that whether or not the methods of primary and secondary enamel preparation affect enamel characteristics after rebonding, by using SEM analysis.
Materials and Methods: Twelve freshly extracted premolars were divided into 4 groups. The samples in each group were conditioned by acid etchant or Er:YAG laser at primary conditioning, according to the instructions. Afterwards, they were bonded with orthodontic brackets. After debonding, the samples were prepared for second conditioning. Also, two samples were conditioned only once with acid etchant or laser, to compare enamel morphology changes with those after re-etching. Finally, buccal enamel surfaces were evaluated using SEM.
Results: Enamel etching patterns were observed in the samples which had been acid-conditioned at first or at both conditionings. The samples irradiated by Er:YAG laser showed amorphous and irregular surfaces, with no signs of typical etching patterns. A large deep gap was seen in one of the samples irradiated with laser at primary and secondary conditionings, which might have penetrated the underling layers of enamel and dentin.
Conclusions: Enamel surface preparation with Er:YAG laser produces irregular and indistinct morphologic changes, completely different from those produced after acid etching at both conditioning and reconditioning. Therefore, it is recommended to use this laser with caution to avoid permanent enamel damage.
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Objectives: Bonding of fiber posts to intracanal dentin is challenging in the clinical setting. This study aimed to compare the effect of self-adhesive and separate etch adhesive dual cure resin cements on the bond strength of fiber post to dentin at different parts of the root.
Materials and Methods: This in-vitro experimental study was conducted on 20 single-rooted premolars. The teeth were decoronated at 1mm coronal to the cementoenamel junction (CEJ), and the roots underwent root canal treatment. Post space was prepared in the roots. Afterwards, the samples were randomly divided into two groups. In group 1, the fiber posts were cemented using Rely X Unicem cement, while in group 2, the fiber posts were cemented using Duo-Link cement, according to the manufacturer's instructions. The intracanal post in each root was sectioned into three segments of coronal, middle, and apical, and each cross-section was subjected to push-out bond strength test at a crosshead speed of 1mm/minute until failure. Push-out bond strength data were analyzed using independent t-test and repeated measures ANOVA.
Results: The bond strength at the middle and coronal segments in separate etch adhesive cement group was higher than that in self-adhesive cement group. However, the bond strength at the apical segment was higher in self-adhesive cement group compared to that in the other group. Overall, the bond strength in separate etch adhesive cement group was significantly higher than that in self-adhesive cement group (P<0.001).
Conclusions: Bond strength of fiber post to intracanal dentin is higher after the use of separate etch adhesive cement compared to self-adhesive cement.
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Objectives: This study sought to assess the effect of quaternary ammonium salt (QAS) on shear bond strength of orthodontic brackets to enamel.
Materials and Methods: In this in vitro experimental study, 0, 10, 20 and 30% concentrations of QAS were added to Transbond XT primer. Brackets were bonded to 60 premolar teeth using the afore-mentioned adhesive mixtures, and the shear bond strength of the four groups (n=15) was measured using a universal testing machine. After debonding, the adhesive remnant index (ARI) score was determined under a stereomicroscope. Data were analyzed using one-way ANOVA.
Results: The mean and standard deviation of shear bond strength of the control and 10%, 20% and 30% groups were 23.54±6.31, 21.81±2.82, 20.83±8.35 and 22.91±5.66 MPa, respectively. No significant difference was noted in shear bond strength of the groups (P=0.83). Study groups were not different in terms of ARI scores (P=0.80).
Conclusions: The results showed that addition of QAS to Transbond XT primer had no adverse effect on shear bond strength of orthodontic brackets. -
Objectives: Zirconia restorations have been suggested as a more durable and more appealing alternative to metal restorations. However, their mechanical properties may be negatively affected by fatigue due to superficial stresses or low temperature degradation. This study aimed to assess the fatigue fracture strength of three-unit implant-supported full contour zirconia and pre-sintered cobalt-chromium (Co-Cr) alloy posterior fixed partial dentures (FPDs).
Materials and Methods: In this in-vitro experimental study, 28 posterior three-unit implant-supported FPDs were fabricated of full contour zirconia and pre-sintered Co-Cr alloy, and were cemented on implant abutments. To simulate the oral environment, FPDs were subjected to 10,000 thermal cycles between 5-55°C for 30 seconds, and were then transferred to a chewing simulator (100,000 cycles, 50 N, 0.5 Hz). Afterwards, fatigue fracture strength was measured using a universal testing machine. Data were analyzed by Mann-Whitney U test.
Results: The mean and standard deviation of fracture strength were 2108.6±440.1 N in full contour zirconia, and 3499.9±1106.5 N in pre-sintered Co-Cr alloy. According to Mann- Whitney U test, the difference in this respect was statistically significant between the two groups (P=0.007).
Conclusions: Since the fracture strength values obtained in the two groups were significantly higher than the maximum mean masticatory load in the oral environment, both materials can be used for fabrication of posterior three-unit FPDs, depending on the esthetic demands of patients.
