Showing 18 results for Majid
F. Baghaie Naeini , E. Yazdi , M. Seyed Majidi ,
Volume 15, Issue 4 (9 2003)
Abstract
The differential diagnosis between pleomorphic adenoma, the most common salivary gland neoplasm, microscopically, and two other common salivary gland neoplasms, meaning adenoid cystic carcinoma and mucoepidermoid carcinoma, is difficut.The purpose of this study was to determine the differences between pleomorphic adenoma, adenoid cystic carcinoma and mucoepidermoid carcinoma regarding the staining intensity with PTAH and H&E and also to investigate the relationship between staining intensity with PTAH and malignancy grade in mucoepidermoid carcinoma. 72 paraffin embeded samples including 24 pleomorphic adenoma, 24 adenoid cystic carcinoma and 24 mucoepidermoid carcinoma were selected and stained with PTAH. The staining intensity in total, in nucleus and cytoplasm of tumoral cells were evaluated and compared with H&E staining, statistically. The results were analyzed by Kruskal-Wallis, and Wilcoxon signed ranks tests (P<0.05).The logistic model was presented to predict the degree of malignancies through the assessment of nucleus and cytoplasm staining intensity in tumoral cells, and the patient's age. In this study, a statistically significant relationship was observed between staining intensity by PTAH and H& E in nucleus of tumoral cells in pleomorphic adenoma. Moreover, statistically significant relation between staining intensity by PTAH and H & E in cytoplasm of tumoral cells in adenoid cystic carcinoma was found. But there was no relation in other cases. On the other hand, a statistically significant relation between intensity of staining in total, in nucleus and cytoplasm of tumoral cells and the type of tumor was found. No relation was obtained between malignancy grade of mucoepidermoid carcinoma and staining intensity in total, in nucleus and cytoplasm of tumoral cells. The presented logistic model indicated a direct relation between tumor malignancy with patient's age and staining intensity in nucleus of tumoral cells, but a reverse relation was found between cytoplasm staining intensity in tumoral cells and tumor malignancy.Our findings show that PTAH and H & E staining methods, lead to similar results, however, PTAH staining is a reliable method in differential diagnosis of such salivary gland tumors.
Abdolrahim Davari, Alireza Danesh Kazemi, Majid Mousvinasab, Ali Nadaf,
Volume 24, Issue 4 (28 2012)
Abstract
Background and Aims: Composite restorative materials and dental adhesives are usually cured with light sources. The light direction may influence the bond strength of dental adhesives. The aim of this study was to evaluate the effect of light direction on the microtensile bond strength of fifth and sixth generation dental adhesives.
Materials and Methods: Prime & Bond NT and Clearfil SE bond were used with different light directions. Sixty human incisor teeth were divided into 4 groups (n=15). In groups A and C, Clearfil SE bond with light curing direction from buccal was used for bonding a composite resin to dentin. In groups B and D, Prime & Bond NT with light curing direction from composite was used. After thermocycling the specimens were subjected to tensile force until debonding occurred and values for microtensile bond strength were recorded. The data were analyzed using two-way ANOVA and Tukey post hoc test.
Results: The findings showed that the bond strength of Clearfil SE bond was significantly higher than that of Prime&Bond NT (P<0.001). There was no significant difference between light curing directions (P=0.132).
Conclusion: Light curing direction did not have significant effect on the bond strength. Sixth generation adhesives was more successful than fifth generation in terms of bond strength to dentin.
Amir Ghasemi, Hasan Torabzadeh, Majid Nasiri, Samaneh Mahvidyzadeh,
Volume 24, Issue 4 (28 2012)
Abstract
Background and Aims: The aim of this study was to evaluate the quality of an experimental hydrofluoric acid (HF) for preparation of porcelain and to compare it with two commercial hydrofluoric acids in Iranian trademark.
Materials and Methods: A- Evaluation of etch pattern of experimental HF using scanning electron microscope (SEM): 6 feldespathic discs were divided into 3 groups. Each group was etched with related HF (experimental, Ultradent and Kimia) for 1 minute. SEM images were recorded at 3 magnifications. B- Bond strength test: 18 feldespathic discs were considered for each acidic group. Then the porcelain surfaces were etched and bonded to composite with unfilled resin. Consequently, the microshear test was done. C- Microleakage test: 54 discs were divided into 3 groups (n=18). Then the porcelain surfaces were etched and bonded to composite with unfilled resin and finally observed under stereomicroscope. The data were analyzed with one-way ANOVA and Smirnov tests.
Results: SEM analysis showed no difference between groups in terms of etch pattern. Microshear bond strength values for experimental, Kimia, and Ultradent HF were 28.53 (±4.92), 28.21 (±6.61), and 26.14 (±7.61) MPa, respectively. There was no significant difference between the bond strength of test groups (P<0.05). Furthermore, no significant difference was found between the microleakage of test groups (P>0.05).
Conclusion: Quality of experimental HF in terms of etch pattern, microshear bond strength and microleakage of composite/porcelain interface was similar to that of two commercial hydrofluoric acids.
Alireza Danesh Kazemi, Abdolrahim Davari, Seied Majid Mosavi Nasab, Ehsan Geravand,
Volume 25, Issue 4 (9 2013)
Abstract
Background and Aims: Re-application of microbrush may affect the micro tensile bond strength of adhesives to dentin. The aim of this study was to evaluate the effect of re-application of microbrushes on the micro tensile bond strength of an adhesive to dentin.
Materials and Methods: Thirty freshly extracted molars teeth were collected and enamel of occlusal surface were removed to expose superficial dentin. Then superficial dentin was etched, washed and partially air dried. According to the times of application of microbrush, teeth were divided into two test groups. In group 1, new microbrushs were used, but in group 2, the ones that were already used for twice were included. Ambar dentin bonding agent (FGM/Brazil) was applied to the etched dentin with microbrushes according to the manufacturer's instructions. Then the crown of teeth was built up with LLiss (FGM/Brazil) composite resin. The teeth were sectioned in buccolingual direction to obtain 1mm slabs. Then 50 hourglass- shape samples were made from 30 teeth (25 Specimens per group). The microtensile bond strength of the specimens was tested using MTD500 (SD Mechatronik, Germany). The data were statistically analyzed by T-test.
Results: The mean values for the microtensile bond strength were 30.49±7.18 and 23.61±9.06 MPa±SD for the first and second groups, respectively. There was significant difference between the groups (P=0.005).
Conclusion: Microbrushes should not be used for more than one cavity preparation.
Mahshid Mohammdi Basir, Elham Tabatabai Ghomsheh, Abbas Azari, Zahra Malek Hosseini, Majid Vahdati Far,
Volume 26, Issue 2 (5-2013)
Abstract
Background and Aims: Endodontically treated teeth are prone to fracture because they loose a big amount of their structure. The treatment plan of those teeth is completed when they are rehabilitated with a strong and functional restoration. The purpose of this study was to evaluate the fracture resistance of endodontically treated teeth restored with amalgam cuspal coverage in comparison with other restorative techniques.
Materials and Methods: 40 human healthy maxillary premolars were divided into 4 groups: group1 (S): sound teeth, group 2(Co): endodontically treated teeth with MOD cavity restored with bonding and composite, group 3(Am-B): endodontically treated teeth with MOD cavity restored with bonding and amalgam and group 4 (Am-CC): endodontically treated teeth with MOD cavity restored with amalgam cuspal coverage. Then the restorations were stored in water and room temperature for 100 days at then thermocycled for 500 cycles between water baths at (5.5 ± 1) and (55 ± 1) 0 C. The fracture resistance was evaluated by universal testing machine (Instron, 1195 UK) with the compressive force of about 2000 N in 0.5 mm/min. The fracture modes were evaluated in four groups by a stereomicroscope. Statistical analysis (Scheffe test) was done for all groups (P<0.05 was considered as the level of meaningfulness).
Results: The highest fracture resistance was found in group 4 (Am-CC) (976 ± 23.27 N) that had no significant difference with sound tooth (P>0.05). The lowest fracture resistance was found in group 2 (Co) (384 ± 137.4 N) that had no significant difference with group 3 (Am-B) (P>0.05). The fracture resistance in group 4 was significantly higher than group 2 (Co) and 3 (Am-B). The fracture mode in group 1 was cohesive within tooth and in group 2 (Co) and 3 (Am-B) was mixed cohesive and adhesive, and in group 4 was cohesive within in restorative material.
Conclusion: The highest fracture resistance was found in teeth that received amalgam cuspal coverage.
Alireza Daneshkazemi, Abdolrahim Davari, Majid Mousavinasab, Alireza Zahedifar,
Volume 26, Issue 2 (5-2013)
Abstract
Background and Aims: Today, use of adhesive systems is the most common materials in restorative dental procedures. The aim of this study was to evaluate the effect of different air-drying periods on the microtensile bond strength of composite to dentin using adhesive.
Materials and Methods: 15 sound molar teeth were selected. The an occlusal surfaces of teeth were removed with silicon carbide disks (3M/USA) to reach flat surface of dentin. Then according to the air drying of solvent, the teeth were divided to five groups. After 5 sec etching and rinsing for 15 sec , the teeth were air dried for 3 sec . Then Singlebond (3M) was used with different air-drying times (0s, 2s, 5s, 10s, 30s) and cured. Then after insertion and curing of Saremco (microhybrid low shrinkage/Switzerland) composite, the teeth were thermocycled for 500 cycles. Then hour glass slabs with 1 mm2 interface was created. Specimens were then subjected to µTBS force until fracture. Data were analyzed using ANOVA and Bonferroni tests.
Results: Statistical tests showed that there were significant differences between bond strength of groups (P=0.002). The mean of µTBS for the 2 Sec and 30 Sec evaporating time was the most and the least vawes, respectively.
Conclusion: An optimum air-drying time for solvent evaporation was the lowest time recommended by the manufacturer. Over and under evaporation time decreased µTBS significantly.
Davari Abdolrahim , Kazemi Alireza Danesh , Mousavinasab Majid , Mohammadi Najmeh Pour ,
Volume 26, Issue 3 (8-2013)
Abstract
Background and Aims: Different adhesives with different solvents may have different solvent evaporation rates. The purpose of this study was to evaluate the solvent evaporation in the self etch and total etch adhesive in different air drying times.
Materials and Methods: Five adhesives were used in this study: Excite, Prime & Bond NT, UNO, Single Bond, SE Bond Primer. Twelve drops of each adhesive were used for each period of air drying (5, 15, 30 sec). The percentage of mass loss was measured during each test. Data were analized using two-way ANOVA and Tukey.
Results: Acetone base adhesives showed more loss of mass than other adhesives (P<0.01). P&B NT showed more loss of mass than other adhesives in all air drying times (P<0.01). Adhesives showed different evaporation rates in different air times (P<0.01).
Conclusion: Adhesives with acetone/water or alcohol/water solvent shows more stable behavior in comparison with adhesives containing pure aqueous solvents.
Majid Akbari, Mohhamad Javad Moghaddas, Sara Majidinia,
Volume 27, Issue 2 (6-2014)
Abstract
Background and Aims: The aim of this study was to evaluate the fracture strength of restored teeth with three different types of E glass-fiber posts after thermo-mechanical loading.
Materials and Methods: Sixty extracted upper central incisor human teeth, with similar size, were selected and divided into three groups (n=20). Endodontic treatment was done in all groups and crowns were sectioned from 2 mm above CEJ. Then one type of posts in each group (Anthogyr, Svensk, Hetco) cemented using Panavia cement and the crowns were restored with a composite. The specimens in each group were thermocycled for 6000 cycles (5-55°C) and subjected to 1200000 cycles of mechanical loadiong in an artificial mouth machine. Then the fracture strength was measured and data were analyzed using ANOVA and T-student test (α=0.05).
Results: The mean fracture strengths in Hetco group before and after thermomechnical loading were 581.098 ± 192.742 N and 564.74±213.59 N, in Anthogyr group were 664.358 ± 135.878 N and 629.12±390.3 N and, in Svensk group were 780.258 ± 379.133 N and 779.84±282.59 N, respectively. There was no significant difference between groups and also there was no significant difference in each group before and after thermo-mechanical loading (P>0.05).
Conclusion: Restored teeth with Hetco fiber glass post were similar in terms of the fracture strength with that of two other posts after thermo-mechnical loading.
Sahebi Majid , Hajizadeh Moslem ,
Volume 27, Issue 4 (1-2015)
Abstract
Background and Aims: Temporomandibular joint disorders are common problems among patients referring to dental schools and clinics. However appropriate treatment modalities are performed for the TMD patients in dental school, the results and success rate of these treatments are not studied distinctly. The aims of this study was to determine the treatment performed for temporomandibular patients at the TMJ department of Tehran University dental school in 2010-11 .
Materials and Methods: In a descriptive cross-sectional trial, 85 TMD patients treated at the TMJ department of Tehran University dental school were examined at least 3 months after the treatments. The patients demographic data ,TMD signs and symptoms and the improvements occurred in TMD disorder were determined (complete, partial and no improvement). The patients satisfaction regarding the treatment results were investigated and data were analyzed regarding the presence of different TMD signs and symptoms before and after the treatment using Mann-Whitney U test .
Results: TMJ pain (35 cases, 42.2%), click (33 cases, 39.8%) and muscle tenderness (26 cases, 31.3%) were the most prevalent obtained signs and symptoms. The mean age of the patients were 32.3 years old while females were the predominant group (72 cases vs.11 one). 44 individuals (53.0%) were treated by splint, 11 ones (13.3%) with anterior repositioning splint and 17 individuals (92.5%) were managed by physiotherapy plus splint. 65 patients (87.3%) were satisfied with the results and 16 ones (19.3%) were not. After the treatment, patients with TMJ pain (P<0.001) and muscle tenderness (P<0.001) showed significantly lower satisfaction than that of patients with no signs. No other significant differences were noted between patients satisfaction regarding the presence of TMD signs and symptoms (P>0.05) .
Conclusion: The results showed that the treatments presented for the TMD patients at Tehran University dental school were successful and most patients received satisfactory treatment.
Akbari Majid , Makarem Abbas , Fazel Akbar ,
Volume 27, Issue 4 (1-2015)
Abstract
Background and Aims: The importance of quality in medical education makes the need for better standards in educational systems in the center of interest as the basis for certification. Standards needed to be evaluated by program administrators before the implementation phase. The purpose of this study was to evaluate the general dentistry standards program in Islamic republic of Iran from dental schools view point.
Materials and Methods: This descriptive study was performed during the year 2011 and 2012. A list of 16 faculties was introduced by the dental secretariat of the Ministry of Health and Medical Education. A check list was conducted based on the basic standards of undergraduate dental program that consisted of the importance and feasibility of each standard. The checklist was evaluated by sixteen dental schools representatives and asked their faculty members and reported back to the dental secretariat of the Ministry of Health. Results were reported in descriptive statistics manner.
Results: Data were collected from 14 dental schools. (Response rate=87%). All of the criteria were essential with more than 85% agreement of the faculties. There were more than 70% of criteria that were not feasible in less than one year.
Conclusion: The dental standard program was widely accepted by the faculties over the country. However, it seemed that by the faculties it would fail if used as accreditation base line.
Majid Sahebi, Marzieh Alikhasi, Farshad Movafegh, Vahideh Nazari,
Volume 29, Issue 1 (7-2016)
Abstract
Background and Aims: In response to esthetic demand and use of zirconia abutments; detection of implant-abutment connection misfit is so important. The purpose of this study was to evaluate the sensitivity and specificity of radiographic images in the detection of abutment-implant connection misfit in zirconia and titanium abutments of three different implant connections.
Materials and Methods: One regular implant fixture of Branemark, Noble active and Replace systems were mount in acrylic models. Two pieces titanium and zirconium abutments were attached to the implants, once with correct adaptation and once with 0.5 mm spacer. Digital radiographic images were taken of 12 created states with zero degree vertical and horizontal inclination and evaluated by 10 specialists in implant treatment in two different time penods. Data were analyzed using Kappa analysis.
Results: Interclass Correlation Coefficients (ICC) of the agreement of answers in the first and second times were 97.4 and 97.5, respectively (P<0/001). Sensitivity of detecting gap in all groups was acceptable (95-100%) except titanium abutment in Noble active which was the lowest value (35%). Specificity of all groups were acceptable (80-95%) except zirconia abutments in Noble active and Replace with 45% and 30% values, respectively, and titanium abutments in Branemark had the highest value (95%).
Conclusion: The sensitivity of radiographic images in detection of abutment-implant connection misfit only in Noble active with titanium abutment was not acceptable. Specificity of radiographic images in the absence of gap in titanium abutments was more favorable.
Majid Akbary, Sanaz Kargozar,
Volume 29, Issue 2 (11-2016)
Abstract
Background and Aims: Implementation of innovative methods for promoting learning persistence is of high importance. The aim of this study was to introduce an innovative teaching method in preclinical course of restorative dentistry and to investigate its impact on the students’ clinical skills.
Materials and Methods: In our study, which was done at the dental School of Mashhad University of Medical Sciences, the Team Based Learning (TBL) technique was applied. 48 fourth-year students took part in the course optionally. They were divided into four groups and the stages of TBL were performed. At the end of the course, a questionnaire was administered to the students. After passing the clinical course of restorative dentistry, the mean scores of students who had passed the voluntary preclinical course were compared with those of who did not pass this course. Data was analyzed using T-test.
Results: The results of this study revealed that the mean scores of students who had passed the voluntary preclinical course was higher than that of the students who did not pass the voluntary preclinical course (P=0.02). Moreover, the questionnaire showed that 97% of students were satisfied with this course and believed that it was useful for them.
Conclusion: This study showed that the innovative method of Team Based Learning (TBL) could promoted learning along with students’ satisfaction of dental preclinical courses.
Mohammad Javad Moghadas, Ehsan Rohani, Sara Majidinia, Najmeh Ojrati, Negin Vatanparast,
Volume 31, Issue 4 (1-2019)
Abstract
Background and Aims: The aim of the present study was to evaluate the effect of applying hydrophobic resin after use of different generation of the bonding systems on nanoleakage.
Materials and Methods: 20 third molar teeth were selected. The teeth were randomly divided into 4 groups of 5, each was treated using the fourth, fifth, sixth, and seven generation of dentin bonding. Then, the crown of teeth was sectioned from the CEJ region and each specimen was divided into two halves with mesiodistal cut, one half for the application of dentin bonding without the addition of a hydrophobic resin, and the other for the same dentin bonding by the addition of a hydrophobic resin. Afterwards, the specimens were restotred by composites. After placement of specimens in silver nitrate, the amount of nanoleakage was evaluated by SEM. Data were analyzed using a repeated measurement statistical analysis (α=0.05).
Results: The use of hydrophobic resins decreased nanoleakage and range of variations in all groups (P<0.05). This reduction was greater for total-etch dentin bonding. Higher degree of nanoleakage occurred in total-etch dentin bonding in most evaluated areas. In general, Clearfil S³ bond showed the least percent of the nanoleakage.
Conclusion: All dentin bonding systems showed some degree of reduction in nanoleakage after hydrophobic layer application and the reduction was greater in Total-etch adhesives systems.
Majid Mehran, Roza Haghgoo, Mohsen Ashourioun, Elham Seifali, Nasrin Takzaree,
Volume 32, Issue 2 (10-2019)
Abstract
Background and Aims: Most children get a lot of anxiety while they visit a dentist. The most important factor in the child's fear at the beginning of treatment is the syringe and needle. Ways to cope with this anxiety include behavioural control techniques such as mental regeneration, distraction, and induction. The purpose of this study was to compare the pain and anxiety in children when using a syringe and toy- shape syringe needle. This study was the first study that used a toy-shape needle cover.
Materials and Methods: This clinical trial study was conducted on 20 children age from 5 to 8 years. More than half of them were anxious with Cfss-Ds (Dental Subscale of the Children's Fear Survey Schedule) and FIS
(Facial Image Scale) anxiety diagnostic tests, and the rest of them were not anxious. Patients were randomly divided into two groups. The first group received local anesthesia with conventional syringe and the second group, by syringe with toy shape needle cover. Following, the first group received local anesthesia by syringe with toy shape needle cover, and the second group, by a conventional syringe. Heart rate measuring and pain evaluating test was performed. Analysis of heart rate and anxiety data was performed by non-parametric wilcoxonsianed Ranks T-test (P-value was considered significant at 0.001).
Results: The mean amount of pain measured after using a syringe with a toy shape needle cover and using conventional syringe had a significant difference of 5.20% between the two groups. The pain was reduced in children who received local anesthesia by syringe with toy shape needle cover (P<0.001).
Conclusion: The physical appearance of the injection device plays an important role in reducing the anxiety and pain of injection in the children.
Noushin Khandan Dezfuli, Majid Sadeghpour, Mojgan Sarabi Nobakht, Elham Estabarghi, Kumarss Amini,
Volume 34, Issue 0 (5-2021)
Abstract
Background and Aims: Periodontitis is a common and inflammatory infectious disease that causes damage to the tissues supporting the tooth and consequent tooth loss. Periodontal disease is a multimicrobial and multifactorial disease and important anaerobic bacteria are involved in periodontal infection. TGF-1β is one of the growth factors and anti-inflammatory cytokines that play a crucial role in the repair of periodontal lesions. The aim of this study was to evaluate Tetra Arms-PCR with high sensitivity and specificity, which can be used to evaluate the genomic polymorphism among oral samples and show the relationship between TGF-1β and periodontal disease.
Materials and Methods: The present study was a case-control study in the periodontology department of Kerman Dental School. Sampling was done from 100 samples including 50 healthy individuals and 50 patients with microbial periodontal infection. Genotype was analyzed using DNA extracted from the blood of patients by PCR -ARMs-Tetra to determine the relationship between TGF-1β genomic polymorphism and periodontitis. Statistical analysis was performed with SPSS19 software and one-way ANOVA.
Results: The samples were culture positive, therefore, more than 65% of the isolated bacteria were anaerobic which included: Prevotella, Porphyromonas, Fusobacterium, Peptostreptococcus anaerobic. The results of Tetra PCR ARMs after sequence frequency were genotype CC allele (25%), CT allele (20%), TT allele (5%). Percentage of control group were CC allele (20%), CT allele (24%), and TT allele (6%). The frequency of C and T alleles in the patient group was 70% and 30%, and in the control group 63% and 37%, respectively with no significant difference between two groups (P=0.83). |
Conclusion: According to the results of this study and the application of anaerobic conditions, forced anaerobic bacteria can be isolated from clinical specimens of oral infections and by Tetra Arms-PCR no significant relationship between TGF-1β genomic polymorphism and periodontitis was observed. In addition, therer was no significant difference in the frequency of alleles and genotypes between the control and patient groups.
Maryam Mohammadi Nodeh, Majid Beshkar, Mohammad Javad Kharazi Fard,
Volume 34, Issue 0 (5-2021)
Abstract
Background and Aims: Fractures of the facial bones and jawbones could cause functional problems along with social and cosmetic problems. Various factors (including road accidents, assault, falling from height, sport injuries, and getting hit by a hard object) could cause these fractures. Collecting and reporting accurate epidemiologic data regarding the facial fractures are major steps toward planning preventive measures. The aim of this study was to collect the epidemiologic data regarding maxillofacial fractures in two referral centers (Shariati and Sina hospitals) in the city of Tehran.
Materials and Methods: The study was a cross-sectional retrospective investigation. All the necessary data were collected from the patients’ files and analyzed using SPSS 25.
Results: The present study pursued data of 454 trauma admitted patients in oral and maxillofacial surgery wards of Shariati and Sina hospitals in 1397 and 1398. These data showed that a number of 374 patients of all patients were men and the other 80 were women. The ratio of male patients to female patients was 4.5:1. In 290 of cases (64%), the fractures occurred as combined fractures and in 164 cases (36%), the fractures occurred as single fracture. These fractures happened mostly in the mandibular bone and in mandibular body, and the least of these fractures happened in Orbit. This study showed that there was a significant relation (with 95% confidence level) between the mandibular body fractures and mandibular angle fractures. This study also showed that there was another significant relation (with 95% confidence level) between the mandibular angle fractures and LeFort 2 fractures. In addition, this study also showed (by using k2 exam) a relation between the etiology of trauma and the number of fractures.
Conclusion: This present study showed that the maxillofacial fractures happened mostly in men much more than women. If we put motorcycle accidents and car accidents in a group together called road accidents, the most common etiology of maxillofacial fractures is road accidents. The results showed that the most fractures happened in the age range of 15-25 year old.
Afsaneh Ghorbani, Sedigheh Sheikhzadeh, Homayoun Alaghehmand, Valiollah Arash, Seyyed Ali Seyyed Majidi,
Volume 37, Issue 0 (3-2024)
Abstract
Background and Aims: Ensuring the long-term stability of orthodontic treatments and preventing tooth relapse remains a significant challenge in orthodontics, often addressed through the extended use of retainers. Given the pivotal role of retainers' physical and mechanical properties in this regard, this study aimed to investigate the tensile strength, flexural strength, and deflection of three distinct types of fixed orthodontic retainers.
Materials and Methods: In this laboratory study, each group comprised 12 samples of twisted, flat, and coaxial retainer wires, each measuring 8 mm in length. These samples were affixed onto the polyethylene blocks using cyanoacrylate adhesive and subsequently subjected to compressive loads using a universal testing machine. The maximum bending strength and deflection rate were recorded from stress-strain diagrams. To evaluate the tensile strength, the identical samples underwent tensile loading. Statistical analysis was performed utilizing SPSS software, employing analysis of variance tests to compare data between groups.
Results: Significant differences were observed in the bending strength (P=0.004), deflection (P<0.001), and tensile strength (P<0.001) among the investigated retainer wires. The flat retainer wire exhibited the highest bending strength, averaging 822.876±136.07 MPa, while the coaxial retainer wire showed the lowest, with an average of 673.65±73.35 MPa. Regarding deflection, the flat retainer wire displayed the highest average at 4.04±0.6 mm, surpassing the other two types of retainers. However, the tensile strength of the twisted retainer wires, averaging 699.7±83.46 MPa, exceeded that of both the flat and coaxial retainer wires.
Conclusion: The flat retainer wires demonstrated the highest bending and deflection strength, while the twisted retainer wires exhibited the highest tensile strength. Overall, the bending strength, deflection, and tensile strength of the 3-strand twisted and flat retainer wires outperformed those of the 5-strand coaxial retainer wires, increased flexural and tensile strengths imply a higher resistance of the wires to the forces induced by harder and more viscous foodstuffs.
Mahdieh Pashapour, Reza Faraji, Valiollah Arash, Seyedali Seyedmajidi,
Volume 37, Issue 0 (3-2024)
Abstract
Background and Aims: The display of an individual's teeth varies in different facial expressions, which significantly affects the beauty of the lower face and overall appearance. The ideal display of incisors is influenced by lip morphology and is an essential aspect of treatment planning. This study aimed to evaluate the ideal display of incisors at rest in women with different lip forms, as assessed by dentists and laypeople.
Materials and Methods: This was a cross-sectional study that was conducted in 2024 at Babol University of Medical Sciences. 46 dentists and 92 laypeople were selected and included in the study in an easy and accessible way. The distance between the uppermost area from the lower edge of the vermilion of the upper lip to the imaginary line between the two commissures was used to classify the lip shape, which was divided into three categories: straight (0-3 mm), medium (3-6 mm) and long (more than 6 mm). Smile images of three women in the age range of 15-30 years were collected and manipulated, resulting in six new images from each original image with varying degrees of incisor display using Photoshop (a total of 18 images). The designed images were randomly placed in a booklet and given to participants, who scored each image on a scale of zero to 100. The data were analyzed by SPSS software version 22 and using the Mann-Whitney test at a significance level of 0.05.
Results: A total of 138 participants took part in the study, including 46 dentists (33.3%), comprising 17 males (37%) and 29 females (63%), and 92 laypeople (66.7%), including 46 males (50.0%) and 46 females (50.0%). Laypeople gave higher scores to images of straight and moderate lip forms than dentists. However, this difference was not statistically significant (P>0.05). In addition, dentists gave significantly higher scores to all images related to the long lip form than laypeople (P<0/05). In addition, among laypeople, men gave a higher score than women to images related to straight and moderate lip form, which was statistically significant (P<0.05).
Conclusion: The findings of this study indicated that a 2.5 mm incisal display at rest was suitable for patients with a straight lip form. In general, it can be concluded that by changing the shape of the lip from straight to long, there is a preference for increasing the amount of incisal display in the resting state.
