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Showing 13 results for Shirazi

M. Shirazi,
Volume 1, Issue 1 (9 1987)

Deep bite is a major clinical problem manifested as higher than normal overbite in anterior region of the jaws. Various studies were conducted to identify the effects of using bite plan and its results. 14 subjects with deep bite were selected out of 400 students of a school who had not proximal caries and had not lost any permanent teeth with healthy periodontal condition. 8 patients were considered as case group and the 6 other as the control group. In case group, a simple labial arc with acrylic palate that caused a gap in occlusion was placed. 2 lateral radiographs were obtained both pre and post 14 months treatment period. After cephalometric analysis, due to bite plane application significant intrusion in mandibular  incisors were observed as well as elongation in both maxillary and mandibular molars.

M. Shirazi ,
Volume 1, Issue 2 (9 1987)

Normal 0 false false false EN-US X-NONE AR-SA Canine retraction to the place of extracted premolar is a basic step in the majority of orthodontic treatments. This is performed frequently by incorrect axis change of canine which moves its root anteriorly. This study is aimed to evaluate canine bodily movements by removable orthodontic appliances and describing the steps of an ideal orthodontic treatment as well as discussing important points on canine retraction. 4 patients with treatment plan of extracting first premolar and replacing the space by canine movement were selected and simple orthodontic appliance were delivered to them. Radiographic analysis showed pdl increased continuously in the side of force application which confirms bodily movement of tooth. Besides, chair side time  is less for removable appliances. Therefore, removable systems are the most desirable orthodontic treatments although there are some limitations in their application.

A. Shirazi, Ar. Talaiepoor, Y. Noroozpoor, H. Bashizade Fakhar, A. Ghasemzade, N. Shakeri,
Volume 21, Issue 3 (8 2008)

Background and Aim: Image distortion is one of the major problems in panoramic radiography. Horizontal and vertical correction factors could be determined for more efficient clinical applications. The purpose of this study was to determine horizontal and vertical correction factors in panoramic radiography.

Materials and Methods: In this test evaluation study in which an asymetric mandibular phantom was constructed by plexiglass and aluminium as soft and hard tissue equivalents. The right half was slightly shorter than the left half. Steel markers were installed to make vertical and horizontal measurments possible.The length of the markers as well as the intermarker distances were measured by Mitutoyo digital micrometer which was accurate within ±0.05mm. The phantom was then positioned in PM 2002 cc proline (Planmeca, Finland) panoramic machine and panoramic images were obtained. 8 times for each half of the phan. The same length and inter marker distances were measured on digitized panoramic images by Cygnus software, which was accurate whitin ±0.01 mm. Magnification and correction factors were determined for the vertical and horizontal dimensions in each region of pantomograms.

Results: The mean vertical correction factor was 0.77±0.02 (range: 0.75-0.80) in the right and 0.77±0.05 (range: 0.75-0.85) in the left half jaw. The mean horizontal correction factor was calculated as 0.98±0.15 (range: 0.76-1.18) in the right and 1.02±0.14 (range: 0.90-1.25) in the left half jaw.

Conclusion: Dissimilarity of vertical and horizontal correction factors among left and right half jaws and also in different regions of a half jaw is relatively considerable. However, a constant correction factor, specialy in horizontal aspect, could not be applicable. Comparing with horizontal correction factors the vertical correction factors showed less variations between different regions as well as different samples.

Zafar Mahdavi Ezadi, Ezatolah Jalalian, Mohamad Hasan Salari, Shima Azimzad, Tahmine Safaie, Mahdi Shirazi, Behzad Salari,
Volume 26, Issue 4 (1-2014)

  Background and Aims : According to the common application of non-metal prefabricated posts in dentistry and lack of enough information about the stress distribution in the root canal walls by these posts, this study was performed to compare the effect of two simple taper and double taper posts on the stress distribution on root canal walls by photo elastic method .

  Materials and Methods: The design of this study was experimental in photoelastic system. The posts, used in this investigation, were double taper and simple taper fiber posts with 0.9 mm diameter and 20 mm length and epoxy resin. First two photo elastic models with tooth dimensions were fabricated and the posts were placed inside the model. Then the core of the each post was fabricated on the model. Each models were loaded in polariscope and the formed fringe order colored ring were photographed.

  Results: In 100 N, 90 degree angle loading in cervical and apical fringe order showed 2.50 and 1.39 in simple taper posts and 1.39 and 2.35 in double taper post. In 150 N, 30 degree angle loading in cervical and apical fringe order showed 4 and 2.65 in simple taper posts, and 4 and 2.5 in double taper post.

  Conclusion: In the vertical and oblique loads, double taper fiber post showed better stress distribution than that of simple tapered posts.

Hadi Asgharzadeh Shirazi, Mohammadreza Mallakzadeh,
Volume 27, Issue 2 (6-2014)

  Background and Aims: Hydroxyapatite coating has allocated a special place in dentistry due to its biocompatibility and bioactivity. The purpose of this study was to evaluate the relation between the hydroxyapatite thickness and stress distribution by using finite element method.

  Materials and Methods: In this paper, the effect of hydroxyapatite coating thickness on dental implants was studied using finite element method in the range between 0 to 200 microns. A 3D model including one section of mandible bone was modeled by a thick layer of cortical surrounding dense cancellous and a Nobel Biocare commercial brand dental implant was simulated and analyzed under static load in the Abaqus software.

  Results The diagram of maximum von Mises stress versus coating thickness was plotted for the cancellous and cortical bones in the range between 0 to 200 microns. The obtained results showed that the magnitude of maximum von Mises stress of bone decreased as the hydroxyapatite coating thickness increased. Also, the thickness of coating exhibited smoother stress distribution and milder variations of maximum von Mises stress in a range between 60 to 120 microns.

  Conclusion: In present study, the stress was decreased in the mandible bone where hydroxyapatite coating was used. This stress reduction leads to a faster stabilization and fixation of implant in the mandible bone. Using hydroxyapatite coating as a biocompatible and bioactive material could play an important role in bone formation of implant- bone interface.

Shirazi Mohsen , Darvishpour Hojat , Nateghi Reza , Mirhashemi Amir Hosein , Salari Behzad ,
Volume 28, Issue 1 (5-2015)

  Tehran University of Medical Sciences, Tehran, Iran ( )

  Background and Aims: Nowadays patients refer to orthodontist for issue such as dental crowding and other aesthetic problems. The aims of this study were to evaluate the relationship between some of mandibular anatomical landmarks and dental crowding in the patient with skeletal Cl II due to mandibular deficiency.

  Materials and Methods: 108 cases have been randomly selected out of patients with mandibular related Cl II problem associated with lower incisor crowding, out of orthodontic patient department of Tehran university of medical sciences. ANB, SNB, mandibular discrepancy, gonial angle, Sn-Go-Gn and IMPA was evaluated out of the data. Lateral cephalograms were used for this matter. The correlation between variables was evaluated by correlation test and after reviewing the data was analyzed using Normality test, the Pearson correlation coefficient was used for normally distributed variables.

  Results: Corpus-ramus length ratio had a significant relationship with dental crowding (P≤0.05) but there was no meaningful and significant relationship between other facial landmarks ( P = 0.26 ).

  Conclusion: there seems to be a slight relationship between facial landmarks and dental crowding in lower incisors. But further case control and clinical studies may be helpful in achieving more reliable data.

Mohsen Shirazi, Yasamin Farajzadeh Jalali, Hojat Darvishpour,
Volume 28, Issue 3 (10-2015)

Background and Aims: Cleft lip and palate patients require orthodontic treatments during their childhood and adolescence. Tweed diagnostic triangle as well as cephalometric assessments provides important data regarding the skeletal patterns for the treatment and diagnostic purposes. The present study determined the cephalometric changes of Tweed triangle in the cleft lip and palate patients compared to normal patients.

Materials and Methods: In total, 101 cleft and palate patients as well as 95 normal individuals with the balanced age, gender and race were evaluated. All the cleft and palate patients had similar treatment histories. Radiographic clichés were obtained from both groups and the images were traced after identifying the anatomic landmarks. The studied landmarks included points, lines, and plans as well as dental and skeletal angles and distance ratios measured in radiographic images. The landmarks were statistically analyzed using Student t test.

Results: Significant differences were found between the cleft lip and palate patients and normal individuals regarding craniofacial complex morphology (P<0.001). Gender did not show significant effect on the cephalometic indices changes (except to IMPA and FMIA angles). Tweed angle changes were more in the males than that of females between normal and cleft lip and palate patients. Mandibular retrusion (decreased SNB), gonial angle opening, increased mandibular plan inclination and facial anterior height were similar in the normal and cleft lip and palate individuals while no significant differences were found between two groups regarding cranium indices (P>0.05).

Conclusion: In total, significant differences were observed between normal and cleft lip and palate individuals regarding Tweed diagnostic triangle area. These differences were decreased IMPA and increased FMA and FMIA angles. No significant differences were found in terms of other indices.

Shirazian Shiva , Arash Mansourian, Mehdi Vatanpour, Fatemeh Tirgar,
Volume 28, Issue 3 (10-2015)

Background and Aims: The purpose of the present study was to investigate the relationship between study skills and academic performance of dental students in Tehran University of Medical Sciences.

Materials and Methods: 195 dental students at dental faculty of Tehran University of Medical Sciences in 2013 participated in this descriptive-analytical study. Data were collected using Congos´ Study Skills Inventory including six subscales. Grade Point Average (GPA) indicated their academic performance. Data were analyzed using ANOVA and Tukey test.

Results: The mean score of students’ study skills were 108 out of 200 with standard deviation of 22.06±0.7. Note taking had a significant correlation with GPA (P=0.015).

Conclusion: Since no significant correlation between study skills and academic performance of the students was observed, it seems that there are other dynamics involved in their academic performance which have to be examined.

Arash Mansourian, Shiva Shirazian, Mohammad Jalili, Mehdi Vatanpour, Leila Pour Momen Arabi,
Volume 29, Issue 3 (10-2016)

Background and Aims: The objective of this study was the development of a checklist for assessment of students’ clinical skills in the clinical oral medicine. The second aim was the assessment of stake holders’ satisfaction of this checklist in comparison to the routine global rating method.

Materials and Methods: The checklist was developed in an expert panel sessions and the validity and reliability of checklist were assessed by CVI and test-retest method, respectively. All students (n=66) were assessed in 2 groups, one with developed checklist and another with global rating. At the end of the session, the satisfaction’s level of staff and students were analysized using Wilcoxon and Mann-Whitney test and the mean scores of students were analysized using Paired T test.

Results: Content validity index (CV I) of checklist was 0.88. Reliability of checklist confirmed with high correlation coefficient (0.9). Staffs’ satisfaction had no significant difference between the two methods
(Wilcoxon P=0.06). The mean score of students who assessed by checklist was higher than global rating with no significant differences (P=0.06).

Conclusion: Regarding the higher students’ satisfaction from checklist and more attention to component of assessment and more objectivity of this method and also higher score in checklist, it seems that the use of a checklist is more proper method for assessing the students’ clinical skills.

Mohsen Shirazi, Armina Mellat, Behzad Salari,
Volume 29, Issue 3 (10-2016)

Background and Aims: In the field of orthodontics, gaining comprehensive information around dento-skeletal complex is necessary to choose the best treatment plan for each patient. The aim of this study was to investigate the linear and angular parameters in panoramic radiographs to find a path to correlate transvers to sagittal dimensions.

Materials and Methods: Total number of sixty two, 8-14 years old children who sought for orthodontic therapy were selected (32 skeletal Class III and 30 skeletal Class I). They were exposed to x-ray to obtain the panoramic and lateral views in a controlled condition. Various linear and angular parameters were measured after tracing the landmarks on the panoramic radiograph. Data were obtained and analyzed using T-test. The level of significance was set at 0.05 (P<0.05).

Results: Linear parameters of Co-Co, Go-Go and PTM-PTM were significantly lower in class III patients than class I ones (P=0.04, 0.04, 0.02, respectively). The ramus width value was also lower in class III patients. Angular parameters of  Me˄ and N˄ also showed the same results (P<0.001). Go˄ angle was significantly lower in the class I than class III patients (P=0.002, 0.007).

Conclusion: Some traceable linear and angular parameters were found in the panoramic radiographs which had the potential to correlate the transverse with sagittal dimension.

Somayeh Zeighami, Marzieh Alikhasi, Maryam Memarian, Moeen Hosseini Shirazi,
Volume 30, Issue 4 (1-2018)

Background and Aims: For the clinical success of implant-retained prostheses, fitness of matching components and stability of the applied torque to the implant-abutment assembly under dynamic occlusal loading is essential. The aim of this study was to evaluate the torque loss in Co-Cr castable abutments after cyclic loading.
Materials and Methods: 10 castable abutments were cast in Co-Cr alloy with similar size and height. Each specimen was mounted vertically on a separated implant using a 30 Ncm tightening torque. The detorque values of the abutments were evaluated after 10 min. The same tightening torque was applied to the abutments on their corresponding implants and cyclic loading was applied for 500,000 cycles to the implant-abutment assembly. The torque values after cyclic loading were recorded for each specimen. T-test analysis was conducted on scores from the groups.
Resultes: The results of this study showed that the percentage of torque loss in castable abutments was significantly increased after cyclic loading (P<0.001).
Conclusion: Misfit between the castable implant components can cause torque loss before and after cyclic loading. However, it is more appropriate to relate the results of this study to the screw loosening of the above mentioned abutments than judging their clinical performance.

Mohsen Shirazi, Shiva Shadmand, Behzad Salari,
Volume 32, Issue 4 (1-2020)

Background and Aims: Nasal obstruction is a common condition among children, in which delaying treatment can stabilize its negative effects on dentoalveolar structures during adulthood. In this study we aimed to investigate the effect of total nasal obstruction on the craniofacial structures of rabbits.
Materials and Methods: In this animal study, total numbers of 44 rabbits with high genetic proximity were selected. Several metal implants were inserted in the anatomic landmarks of their skulls and then underwent three different types of x-ray exposure (lateral, posterior-anterior and occlusal views). Half of them underwent surgically assisted total nasal obstruction, and the other half were considered as control group. All rabbits were kept in the same environment up to maturation period. Then, they underwent the same x-ray exposures. The primary and final radiographs were traced and various linear and angular were compared between them.
Results: The anterior facial height (P=0.01), maxillary depth (P=0.005), articular angle (P=0.005), maxillary and mandibular plan angle were significantly more in the rabbits with total nasal obstruction. However, the interdental width (P=0.005), maxillary perimeter (P=0.005), nasopharyngeal width (P=0.01) and maxillary and mandibular width were significantly less in them. The skull base length (P=0.30), gonial angle (P=0.40), and maxillary length (P=0.10) were not significantly different between the two groups.
Conclusion: Total nasal obstruction had various impacts on the craniofacial structures.

Shiva Shirazian, Sakineh Nikzad Jamnani, Maryam Memarian, Homa Shaghi,
Volume 33, Issue 1 (7-2020)

Background and Aims: Due to the very high importance of assessing the clinical performance of students, choosing the best assessment tool and method is one of the most important goals and tasks in medical education. The objective of this study was the development of a checklist for the assessment of dental students’ clinical skills of Tehran University of Medical Sciences, in the clinical complete denture course. The second aim was to determine the validity and reliability of the checklist, and The third aim was the evaluation of raters’ and students’ satisfaction.
Materials and Methods: The checklist was developed in expert panel sessions, and the validity and reliability of the checklist were assessed with CVI (content validity index) test-retest and inter-rater reliability methods, respectively. Students (n=15) were evaluated with a developed checklist. At the end of the session, the satisfaction level of staff and students were assessed. The obtained information was reported descriptively with the expression of mean and standard deviation and in the form of relative and absolute frequencies.
Results: The content validity index (CVI) of the checklist was 0.96. The reliability of the checklist confirmed with a high Intraclass Correlation Coefficient (>0.8) (between 0.82-0.97) (P<0.05). The coefficient of agreement in inter-rater reliability was 0.99 (between 0.991-0.998). Raters’ and students’ satisfaction earned a high percentage of satisfaction.
Conclusion: The designed checklist has the optimal features of a good students’ clinical performance assessment tool; it seems that using this checklist can be an excellent alternative method to a global rating scale to assess the clinical skills of dental students in the complete denture courses.

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