Journal of Dental School

Objectives: It is important to know the exact location and anatomic variety of inferior alveolar nerve canal for different procedures of mandibular surgeries. The aim of the present study was to evaluate inferior mandibular canal’s anatomic position by Cone-beam Computed Tomography (CBCT).

Methods: In a cross sectional study, CBCT were taken and assessed from 130 patients (260 semi-arch) referring to the radiologic department of Shahid Beheshti Dental Faculty. Three points including 1cm before mental foramen (point A), under second molar’s furcation (point B) and 1cm after mandibular foramen on the inferior alveolar canal (point C) were chosen. The canal diameter, length and the distance between the canal and inferior border of mandible were measured. SPSS version 19 software used for data analysis. T and variance tests evaluated the role of age, gender, canal length and jaw side.

Results: Mean age of patients was 43.73±13.25. Canal length, 61.71 ± 4.95 ml and canal diameter was 2.94 ± 0.58 mm. The distance between the canal and the inferior border of mandible was 9.47 ± 2.23 mm. There was a significant difference in gender and age for all parameters. The distance between the canal and the inferior border in C point and at mental foramen in cases with short and long canal length showed a significant difference. (p≤0.012)

None of the variables showed significant difference between right and left sides.

Conclusion: The anatomic position of mandibular canal is related to gender and canal length, and independent to age and side.

Objectives: Ceramics have advantages such as optimal esthetics and biocompatibility. However, in the oral environment, they are subjected to high levels of stress due to masticatory forces, saliva, thermal changes and alterations of pH, which increase their risk of fracture. Since replacement of these restorations is costly and time-consuming, composite resin is often used for intraoral repair of these restorations. This study aimed to assess the shear bond strength of two porcelain repair systems by Pulpdent and Ultradent and evaluate the effect of number of silane layers on the shear bond strength.

Methods: This invitro experimental study was conducted on 66 porcelain blocks measuring 3×5×8mm. In each kit, samples were randomly divided into three groups of 11. Silane was not used for group one. Groups two and three received one coat and two coats of silane, respectively. After surface preparation, composite was bonded to ceramic surfaces. Data were analyzed using two-way ANOVA.

Results: The LSD test showed that application of Ultradent silane significantly affected the shear bond strength (P<0.05) while Pulpdent silane had no such effect (P=0.89). Application of one layer and two layers of silane was not significantly different (P=0.94).

Conclusion: Ultradent ceramic repair kit yields higher shear bond strength at the ceramic-composite interface compared to Pulp dent ceramic repair kit. Use of one or two layers of silane does not make any significant difference with regard to the shear bond strength of ceramic to composite.

Objectives: Prefabricated functional appliances have therapeutic effects similar to those of custom-made functional appliances. This study aimed to assess the dentoskeletal effects of Multi P^® prefabricated functional appliance on Class II Div 1children in late mixed dentition.

Methods: This open label trial was conducted on 18 children aged 9-12 years with Cl II Div 1 malocclusion due to mandibular deficiency during a 9-month period. Written informed consent was obtained from the parents. Multi P ^® (RMO, Strasbourg, France) was used by the patients 4 hours/day and overnight (minimum of 8 hours) in conjunction with specific exercises (pressing the teeth in the recorded occlusion, pressing the tongue against the palate and uninostril breathing). Patients were visited monthly. Study casts and cephalometric radiographs were obtained before and after the treatment. Data were analyzed using paired samples t-test and McNemar’s test.

Results: The Go-Gn (P=0.029) and Me-N (P=0.021) distances significantly increased following the use of appliance while overjet (P<0.0001), absolute overbite (P=0.002) and the Wits appraisal (P=0.019) significantly decreased. Other understudy angles did not change significantly.

Conclusion: Multi P® appliance decreases the jaw base discrepancy and corrects the overjet and overbite.

Objectives: Among the various impression materials, for alginate tear strength is probably more important than the compressive strength. The tear strength is important when an impression involves a mechanical undercut and/or lacks bulk strength to resist tearing. This study evaluated tear strength of Iralgin and compared it with tear strength of Alginoplast.

Methods: In this invitro experimental study A mold was made with 100mm×20mm×1mm dimensions and a longitudinal prominence in 0.3 mm depth. Twenty–seven specimens (9 Super Iralgin, 9 Pocket Iralgin, and 9 Alginoplast) were selected non–randomizedly. Each specimen prepared corresponding to manufacturer and injected into the mold. And the mold was placed under press. After removing the mold from press, every specimen formed as a trouser-shaped specimen. The specimen was pulled in tensile machine with 50 mm/min speed. The data of specimens in different groups were statistically analyzed using one-way ANOVA, Kolmogorov-Smirnov, and Levene's tests.

Results: Mean of tear strength in first specimen (Super Iralgin), second specimen (Pocket Iralgin), and third specimen (Alginoplast) were 640±38 grf/cm², 500 ±20grf/cm², and 1100±27 grf/cm² respectively. According to ANOVA test, the mean of tear strength was not equal in three specimens (p<0.01). According to LSD Multiple Comparison, the first and second specimens were same in tear strength, whereas the third specimen was different from the two former (p<0.05 and p<0.01).

Conclusion: Super Iralgin and pocket Iralgin were the same in tear strength. Alginoplast was significantly higher than super and pocket Iralgin in tear strength.

Objectives: The aim of this study was to compare the microtensile bond strengths (µ TBS) of three core materials with one lithium disilicate reinforced ceramic using two resin cements.

Methods: Three core materials (Nulite F® (Biodental Technologies), Filtek Z250® (3M-ESPE), Prettau-Anterior® (Zirkonzhan, Germany)) were prepared as blocks (10×10×4 mm3) according to the manufacturer’s instructions. Lithium disilicate ceramic blocks were also constructed and bonded to core specimens with two dual curing luting resin cements (Duo-Link® (Schaumburg, IL), Bifix QM® (VOCO, Cuxhaven, Germany)). Micro-bar specimens were prepared and loaded in tension to determine the µ TBS Failure modes were classified by scanning electron microscope (SEM). Data were analysed using two-way ANOVA and Tukey HSD test.

Results: The µ TBS varied significantly depending on the core materials and resin cements used (P< 0.05). The µ TBS of Bifix QM was significantly higher than of Duo-Link in all core materials. The µ TBS of zirconia core was significantly higher than of both composite cores with both resin cements. There were no statistically significant differences among Nulite F and Filtek Z250 (P> 0.05). The highest bond strength was obtained between zirconia core and Bifix QM (45.3 ± 6.7 MPa).

Conclusion: In vitro µ TBS of glass ceramic blocks bonded to zirconia core material showed higher bond strength values than resin-based core material, regardless of the resin cement type used.

Objectives: Several methods of image acquisition are accessible in dentistry. There is no overall acceptable method for image digitization so all different types of images can be comparable. The objective of this study was to compare the diagnostic accuracy of different methods of image digitization.

Methods: This accuracy diagnostic test study used perceptibility curve test which first introduced by de Balder was applied. In this test a test object is used which is usually made by aluminum. Different levels of thickness and number of holes in the test object were necessary to have different levels of contrast. Images from film and CCD and digitized images by means of CCD scanners and digital camera were prepared. Nine observers assessed the images. Data collected was delivered to SPSS 13 software and for each image acquisition method, interclass correlation coefficience was computed and compared to the gold standard.

Results: Mean sensitivity, specifity, positive and negative like hood ratios in dependence on material thickness and the background gray value were calculated. In regions of high optical density the sensitivity for the film images was highest (0.994) following by CCD (0.905), scanner (0.889) and camera (0.821). Difference between CCD images and scanner images was not significant. In dark regions of no dark holes the sensitivity was highest for film images (0.832) following by CCD (0.798), camera (0.714) and scanner (0.615) Difference between film and CCD images was not significant.

Conclusion: The diagnostic quality of radiographic films was better than digital CCD sensors. For digitizing analog images scanners were better than digital cameras.

Objective: The purpose of this study was to retrospectively analyze the demographic characteristics of patients with central peripheral giant cell granulomas (CGCGs) / (PGCGs) an Iranian population.

Methods: In this 38-year retrospective study, the data were obtained from records of 1019 patients with CGCG and PGCG of the jaws referred to the Department of Oral and Maxillofacial, Pathology, Mashhad University of Medical Sciences, Iran between 1972 and 2010. Information regarding age distribution, gender, location of the lesion and clinical signs and symptoms was documented.

Results: A total of 1019 patients were affected by giant cell granuloma lesions (GCGLs) including 435 CGCGs and 584 PGCGs. The mean age was 28.91 ± 18.16. PGCGs and CGCGs had a peak of occurrence in the first and second decade of life respectively. A female predominance was shown in CGCG cases (57.70%), whereas PGCGs were more frequent in males (50.85%). Five hundred and ninety eight cases of all giant cell lesions (58.7 %) occurred in the mandible. Posterior mandible was the most frequent site for both Lesions. The second most common site for PGCG was posterior maxilla (21%), whereas anterior mandible was involved in CGCG (19.45%). The majority of patients were asymptomatic. Patient's age, location (mandible/maxilla) and bleeding were the influential variables on the type of the lesion.

Conclusion: Although the CGCGs share some histopathologic similarities with PGCGs, differences in demographic features may be observed in different populations.

Objectives: Periapical Granulomas (PGs) and Radicular Cysts (RCs), as the most common odontogenic lesions have yet unclear pathogenesis. This study was aimed to compare PCNA and Ki-67 expression in PGs and RCs and evaluate their possible relationship with two lesions.

Methods: In this cross-sectional descriptive study, twenty PGs and twenty RCs were evaluated immunohistochemically using an anti-PCNA and anti-Ki-67 polyclonal antibodies. PCNA⁺ and Ki-67⁺ cells were counted in connective tissue wall and epithelial lining (in RCs). Statistical analysis was performed by using Mann-Whitney U test and Spearman’s rank correlation coefficient.

Results: In PGs, percentage of PCNA and Ki-67 expression were found 70% and 30%, respectively; In RCs, PCNA and Ki-67 expression were observed 90% and 55%, respectively. Additionally, in RCS, Immunoexpression of PCNA (85%) and Ki-67 (60%) were detected at epithelial lining area. The positive immunoexpression of PCNA in RCs was greater than PGs (p<0.05).

Conclusion: Immunoexpression of PCNA and Ki-67 were detected in both lesions which may be mentioned as valuable markers for the prediction of biologic behavior of PGs and RCs.