Journal of Mashhad Dental School
Year:2012 | Volume:36 | Issue:3 (82)|Papers Count:10

Introduction: Contemporary cephalometric analysis in orthodontics is based on comparison between craniofacial portions and reference planes. One of these planes is Frankfort Horizontal (FH) Plane that can be made by anatomic portion or machine portion. The aim of this study was to determine and compare the angle between Anatomic Frankfort Horizontal plane (AFH) and True Horizontal (TH) with the angle formed by Machine Frankfort Horizontal plane (MFH) and TH.Materials & Methods: In this Analytical-descriptive study, digital lateral cephalograms were taken in Natural Head Position from 50 orthodontic patients with the minimum age of 14 and class I malocclusion (Viazis analysis on Onyx Ceph software was employed to confirm the class I malocclusion). Then on each cephalogram, two FH planes were constructed using machine and anatomic portions. Then the angle between each FH plane and TH plane was measured and recorded. Finally, the data were analyzed by paired t-test (a=0.05).Results: Machine Frankfort Horizontal plane (MFH) and Anatomic Frankfort Horizontal plane (AFH) showed significant differences of -5.66 and -1.58 degrees with True Horizontal plane (TH) respectively (P<0.001).Conclusion: For cephalometric evaluation in orthodontic patients if the Frankfurt plane be used, it is better to use anatomical portion, because the difference between the Anatomic Frankfort Horizontal plane (AFH) and True Horizontal plane (TH) is significantly less than the difference between the Machine Frankfort Horizontal plane (MFH) and True Horizontal plane (TH).

Introduction: Low fracture resistance is one of the most important disadvantages of all-ceramic restorations. The aim of the present study was to assess the effect of convergence angle and change in copping thickness related to it on fracture resistance of all ceramic crowns.Materials & Methods: This study was an experimental study in which 30 brass dies were fabricated as crowns with a height of 5.5mm, base diameter of 6.2mm and marginal thickness of 1.2mm in the following design: (10 shoulder 90o ®Convergence 6o), (20 shoulder 90o ®Convergence 12o). With a special index, 0.6mm thickness acrylic cores were made on 20 dies (10 with 6o convergence, 10 with 12o convergences). With the 6o index and 12o dies, 10 cores were made with the thickness of 0.6mm+difference in thickness of 6o and 12o convergence angle. Cores were casted with IPS e.max porcelain of core and veneered with another index with parallel cylindrical wall and then cemented with Panavia F2 on the brass dies. After storage in distilled water of 37oC for 24 hours, the specimens were placed in compressive test ring within an Instron universal testing machine and loaded in the center of occlusal surface with a 4mm diameter stainless steel ball. An axial preload of 20N was applied followed by a compressive load until fracture occurred. The data were analyzed with one way analysis of variance (ANOVA).Results: Average fracture load in 6o convergence angle and 0.6mm core thickness was 1951.40N, in 12o convergence angle and 0.6mm core thickness, it was 2798.46N and in 12o convergence angle and 0.6mm+additional core thickness because of increase in convergence angle, it was 3151.05N. The results revealed no significant difference in the fracture load between two core thickness but fracture load of 12o convergence angle was significantly greater than 6o (P<0.001).Conclusion: Copping thickness didn’t affect the fracture load of all ceramic crowns but increase in convergence angle increased the fracture load significantly.

Introduction: Ameloblastoma is a benign epithelial odontogenic tumor that exhibits a more aggressive behavior than odontogenic keratocyst and follicular cyst. The purpose of this study was to determine and evaluate histomorphometric characteristics and blood vessels pattern adjacent to and far from odontogenic epithelium on the clinical behavior of the above odontogenic lesions with immunohistochemistry and morphometry method.Materials & Methods: In this descriptive-cross-sectional study, 45 paraffin blocks of mentioned lesions were selected and marked immunohistochemically with CD34. From three HPFs (High Power Fields) in each slide which had more density of blood vessels in adjacent to and far from odontogenic epithelium, photography was done by a camera joined to a microscope with 40 times magnification. Through the software Motic plus 2, the internal and external diameters, section surface and thickness were determined. Also the blood vessel pattern was determined in the mentioned lesions and was compared through ANOVA, t-test and Multiple Comparison Test.Results: The external and internal diameters and sectional surface in the regions far from the odontogenic ephithelium in ameloblastoma was greater than keratocyst (P<0.001) and dentigerous cysts (P=0.001) but there was no significant statistical differences seen in the thickness of blood vessels in the regions far from the odontogenic ephithelium in three lesions (P=0.05). Significant statistical difference was not seen in external (P=0.8) and internal (P=0.8) diameters, sectional (P=0.6) surface and blood vessels thickness in the adjacent regions of odontogeni ephithelium in these three lesions. The pattern of blood vessels in ameloblastoma was circumferential and in the keratocyst and follicular cyst, it was directional.Conclusion: It seems that morphometric characteristics of blood vessels (internal and external diameters, sectional surface) in areas far from odontogenic ephithelium and the type of blood vessels pattern affects clinical aggressive behavior of ameloblastoma more than keratocyst and follicular cyst.

Introduction: Squamous cell carcinoma (SCC) is the most common malignant tumor of oral cavity (O) and esophagus (E). P27 protein has a significant role in biological behavior of the tumors. The purpose of this study was to determine the frequency of P27 expression in OSCC and ESCC.Materials & Methods: Forty paraffin embedded blocks of OSCC & ESCC were collected & clinic pathological data were recorded in this descriptive study. Immunohistochemical staining (IHC) was done for P27 (Kip1) & Labeling Index (percent of positive cells in 10HPF) was calculated and then cases classified in to low (LI£25%) and high (LI>25%) expressions. Statistical analysis was performed by SPSS16 using Fisher's exact and Mann-Whitney tests.Results: Twenty-four cases (60%) were male and 16 cases (40%) were female. The mean age was 65.3±14.3. Twenty five percent of ESCCs and 10% of OSCCs showed high expression of P27. Seventy five percent of ESCC and 90% off OSCC showed low expression and there was no significant difference among OSCCs and ESCCs (P>0.05). There were no significant correlations between age, sex, grade or size of the tumors and P27 expression in OSCCs and ESCCs.Conclusion: Low expression of P27 was found in most of ESCC and OSCC cases.

Introduction: Evaluation of educational processes in different fields of medical sciences has high priority because of the important role in professional experts training.Dentistry, as an important field of medical sciences, requires scientific & professional skills. Surveying the opinions of dental students as the main actual consumers of the education is one of the most popular methods to evaluate the quality of dental clinical education. The aim of this study was to evaluate the students’ perception about clinical education and examination in Mashhad dental school in 2009.Materials & Methods: All students at fourth, fifth and sixth grades of Mashhad dental school in 2009, were participated in this cross-sectional study. A questionnaire was designed in this study to assess clinical education. The validity and reliability of the questionnaire was proved. The results were presented in tables. Kruskal Wallis test was used to compare between groups (a=0.05).Results: The results showed that the students’ perception, in most areas of education, performance of clinical faculty, clinical facilities, clinical assessment, evaluation of students’ activities by professors, nurses cooperation and educational purposes was positive while there were some deficiencies particularly in course selection, and monitoring student’s work in a few departments. There was no difference between clinical education and evaluation of departments in dental school in students’ points of view.Conclusion: It can be concluded that revision of school activities & review of curriculum for possible changes, providing equipment and materials required in the clinical environment is suggested.

Introduction: To ensure retrievability of cemented implant-retained restorations, use of provisional cements has been suggested as an alternative to that of definitive ones. Some cements are stronger than other ones. To maintain retrievability, selection of the provisional cement is important. The aim of this study was to compare the tensile strength of three different temporary cements in crowns cemented on one piece abutments with two lengths.Materials & Methods: Twenty DIO implant analogs were fixed in an acrylic block using a dental surveyor. Blocks were divided in to two groups of 10 abutments. In one group, solid abutments with 3.5 mm diameter and 5.5 mm height and in the other one, abutments with 3.5 mm diameter and 7 mm height were placed in each implant analogs and torque to 30 N.cm. After fabrication of crown for each abutment, provisional luting agents Temp bond, Dycal and Temp bond clear were used to cement the crowns to the respective abutments. All specimens were stored in 100% humidity environment for 48 hours at 37oc prior to testing. Crowns were pulled from abutments with a universal testing machine at a cross head speed of 0.5 cm/min and tensile strength was recorded in Newton. Data were analyzed using 2-way analysis of variance (ANOV A).Results: Tensile strength was significantly higher for Dycal (138.6) than for Temp bond clear (68.3) and Temp bond (30.3) (P<0.001). Also for each type of cement, the mean tensile strength was significantly higher at 7x3.5 mm abutments compared with 5.5x3.5 mm (P=0.006).Conclusions: It is preferred to use Temp bond while we need retrievabibity of cement retained fixed implant restorations and Dycal while we need higher retention.

Introduction: Routine materials used for restoration and reconstruction of primary teeth are composite resins, glass ionomers, amalgam and stainless steel crowns. The purpose of this study was to determine the amount of microleakage in pulpotomized primary molars restored with core max II (one kind of adhesive restorative materials).Materials & Methods: Thirty extracted primary molars were selected. After being cleaned, the teeth were pulpotomized and then covered with Zinc Phosphate as liner. The MOD cavity outline was performed with buccolingual width of 2/3 of the distance between cusp tips, and the gingival floor finished at CEJ level. Then, the teeth were divided into two equal groups of 15. Teeth in group A were restored with amalgam, whereas the others in group B were restored with Core max II. Both groups were carried to artificial mouth staying for 2 days, followed by a one-week period resting in incubator. Apices of the teeth were sealed with wax and the entire tooth surface, except for the restored zone and 1 mm beyond it, were covered with two layers of varnish and then they were floated in a special liquid paint, called Basic Fuchsin 20%. Next, roots of the teeth were cut three mm below the CEJ. After that, the teeth were mounted in epoxy resin up to 1 mm below the CEJ level. After 24 hours, all of the specimens were sectioned mesiodistally. Finally the specimens were examined with a steriomicroscope in order to determine the amount of microleakage.Using the SPSS software version 11.5 at 5% significance level, the results were analysed with Mann-Whitney U test.Results: Paint penetration intensity in restored teeth with no microleakage was equal in group A and B. There were minor differences between these two restorative materials when microleakage penetrated to either half of gingival wall or to all of gingival wall. Paint penetration intensity in group A was equal with that of group B when microleakage penetrated in axial wall. The difference in the amount of microleakage between amalgam and Core max II was not significant (P>0.05).Conclusion: According to the results of this study, since the amount of microleakage in Core max II was as low as amalgam, it can be used as an suitable alternative restorative material in pulpotomized primary molars.

Introduction: An ideal toothpaste should have most plaque removal efficacy with at least abrasivity. The aim of this study was to evaluate enamel abrasion induced by 12 toothpaste types including Darogar 3, Nasim, Crest 7, Crest sensitivity, whitening signal, sehat, pooneh 3 color, paveh, whitening pooneh, crest 3D white, sensodine original and pooneh sensitivity.Materials & Methods: This was an in vitro experimental study. Dental samples collected after cutting were embedded in acrylic blocks, and the enamel surface polished to be smooth. The samples were divided into six groups of twelve. The initial surface profile was measured with the profilometry device and for brushing; the samples were located in V8cross brushing machine. After washing and drying the samples, the secondary surface profile was measured with the profilometry device again. The value difference before and after brushing shows abrasion of the toothpaste on single micron. Data were analyzed by means of ONE WAY ANOVA.Results: There was no significant difference in abrasivity among different toothpastes. The highest rate and the lowest rate of abration were observed in crest sentifivity and pooneh sensivity, respectively. The abration sensitivity pooneh; rate of other toothpastes were between these two rates.Conclusion: According to the results it has been revealed that there were no differences among enamel abrasion of common Iranian toothpastes.

Introduction: A good apical seal plays a critical role in the success of endodontic treatment. The most common cause of treatment failure has been the lack of root apical seal. The aim of this study was to compare the apical seal of three root canal sealers including AH26, AH Plus and Tubliseal together and with positive and negative groups, using a dye penetration test.Materials & Methods: One hundred and ten humon upper central teeth were used in this study. Teeth were kept in 10% formalin solution and then were maintained for three days in 5.25% NaOCl. The teeth were randomly divided into three experimental groups (N=30) and two negative and positive control groups. After debridement of the external surfaces the crowns were cut at the CEJ, and were instrumented by stepback technique and obturated using lateral condensation technique with gutta-percha and either AH26 , AH Plus or Tubliseal. In positive control group, after preparation, the canals were filled with gutta-percha without sealer, and in negative control group, the canals were prepared but not filled. Two mm of coronal canals were filled with amalgam and negative control group were coated with two layers of nail polish and one layer of sticky wax, and next, were incubated for 72 hours after that, the surface of the other teeth except 2 mm in apical area was coated with nail polish and wax. Finally then the teeth were centrifuged with India Ink and kept in ink for 72 hours. After longitudinally sectioning, the amount of dye penetration was measured under the stereomicroscope by three individuals who were blind to the groups. Data were analyzed by ANOVA and post hoc Tukey HSD test, through SPSS 15 software.Result: Higher level of dye penetration was observed in group B (Tubliseal) which was significantly greater than the rate in groups A (AH26) and C (AHPlus), while the difference observed between groups A and C was not statistically significant.Conclusion: The results of this study showed that although AHPlus is better than AH26, there was no statistically significant difference in apical seal of AH26 and AH Plus sealers: However, the leakage of them was significantly less than that of Tubliseal sealer.