Showing 13 results for Stress
A. Monzavi , Gh R. Farhang ,
Volume 13, Issue 3 (10-2000)
Abstract
The geometric shape of dental arch (square, tapering, ovoid) is an important factor in stress distribution pattern around dental implant. The aim of this study was to evaluate the role of arch form and the amount of bone loss (normal, moderate, high) in stress distribution around dental implant by considering different load direction. Three arch forms square, ovoid, and tapering with three different stages of bone loss were designed. Models were divided into three-dimensional elements, which made 5500 nodes. The 143N load was applied at two angles (straight, oblique) at the last fixture, 8mm, and 16 mm from the center of implant on l!ie cantilever. The Sap90 software was used for analyzing the stress distribution in this study. 54 different conditions were evaluated. Results showed that stress concentration changed from support toward fixture due to distally changing the load in the square and ovoid arch forms with normal bone. In the tapering arch with normal bone stress concentration was around the fixture. The amount of stress in normal tapering arch was more than physiologic extend, therefore, application of cantilever in tapering arches is not recommended.
A. Abolghasemi , M. Hajjaran , A. Kiamarsi ,
Volume 20, Issue 2 (5-2007)
Abstract
Background and Aim: Dental anxiety is a common problem in pediatric dentistry and results in behaviors like fear and anger that can negatively affect dental treatments. Exposure to various dental treatments and distressful experiences are reasons for anxiety during dental treatments. The aim of this study was to evaluate effect of cognitive behavioral interventions in reduction of stress during dental procedures in children.
Materials and Methods: In this clinical trial, 42 boys and girls, undergoing dental treatments were selected from dental clinics in Tehran. Patients were assigned to cognitive-behavioral interventions, placebo and control conditions. The fear scale, anger facial scale, pain facial scale and physiologic measure of pulse beat were evaluated. One way ANOVA and Tukey test were used to analyze the results and p<0.05 was the level of significance.
Results: Results showed significant differences between cognitive-behavioral interventions, placebo and control groups regarding fear, anger, pain and pulse beat. Comparison tests revealed that cognitive-behavioral interventions were more effective in reducing fear, anger, pain and pulse beat compared to the placebo or control.
Conclusion: According to the results of this study cognitive-behavioral interventions can be used to reduce distress of children undergoing dental procedures.
F. Sarkarat, B. Bohluli, Sh. Ansari, H. Shahabi,
Volume 22, Issue 3 (12-2009)
Abstract
Background and Aim: Due to the complications associated with fixation by Titanium screws and plates in Bilateral Sagittal Split Ramus Osteotomy (BSSRO) surgery, the use of resorbable polymers has been increasingly recommended. Since there are not enough studies on this issue, this study aimed to assess the most appropriate stress distribution in fixation with resorbable screws after BSSRO surgery by Fnite Element Analysis (FEA).
Materials and Methods: This experimental study was performed on simulated human mandible using Ansys and Catia softwares. The osteotomy line was applied to the simulated model and experimental loads of 75, 135 and 600 N were respectively exerted according to the natural direction of occlusal force. The distribution pattern of stress was assessed and compared for fixation with one resorbable screw, two resorbable screws in vertical pattern, two resorbable screws in horizontal pattern, three resorbable screws in L pattern and three resorbable screws in inverted backward L pattern using Ansys software.
Results: Among the four simulated fixations, L pattern showed the highest primary stability. Two screws in vertical pattern were also associated with sufficient primary stability and less trauma and cost for patients. One screw did not provide enough stability under 600 N.
Conclusion: Polymer-based resorbable screws (polyglycolic acid and D, L polylactide acid) provided satisfactory primary stability in BSSRO surgery.
R. Baghai Naini , S. Nokar , Sh. Borghei ,
Volume 23, Issue 2 (10-2010)
Abstract
Background and Aims: The All-on-4 design with its significant advantages is an appropriate model in reconstruction of edentulous mandible. Evaluation of stress and strain distribution in this model is necessary for better judgment. The purpose of this FEA study was to measure stress and strain distribution on peri-implant bone in All-on-4 design in edentulous mandible.
Materials and Methods: Three dimensional finite element model of human mandible was simulated according to data from CT-Scan of a cadaver. The model of 4×13.5 mm Nobel Biocare implant was simulated. Posterior implants were inserted in 452 inclination and anterior implants were parallel and vertical. Implants were splinted with a titanium bar and an acrylic superstructure was then simulated around the bar. Vertical loads of 178 N and 300 N were applied at incisor and left first molar positions, respectively. After meshing, defining boundary conditions and materials properties, analysis was performed with the aid of ABAQUS.
Results: Maximum Von-Mises stress of 38.9 MPa during anterior loading was located in peri-implant bone of anterior implants but maximum strain was observed in peri-implant bone of posterior implants. In posterior loading, maximum stress (77.3 MPa) was in peri-implant bone of posterior implant which was next to the place of load insertion. Maximum strain was found in the same area.
Conclusion: During posterior loading, significant amount of strain was observed in peri-implant bone of posterior angulated implant. As a result, there was a possibility of resorption in this area. During anterior loading, detected stress and strain was absolutely favorable.
Hr. Rajati Haghi , S. Nikzad , A. Azari , J. Kashani ,
Volume 23, Issue 2 (10-2010)
Abstract
Background and Aims: Freestanding fixed partial prosthesis is considered the first choice whenever possible. However, anatomical limitations for implants and other reasons may create situation in which it would be preferable to connect the implants to teeth. A biomechanical dilemma in a tooth/implant-supported system comes from dissimilar mobility. This disparity cause the bridge to function as a cantilever and a series of potential problems such as osseointegration loss, screw loosening arise. The aim of this study was to analyze the tooth-implant supported bridges in rigid/non-rigid connectors in cemented prostheses using finite element stress analysis.
Materials and Methods: In this study four three-dimensional models were simulated by use of Solid works software. These models are: 1-RCCP: rigid connector between tooth and implant, 2-NRC CP1: non-rigid connector at mesial side of implant, 3-NRC CP2: non-rigid connector at distal side of second premolar, 4-NRC CP3: non-rigid connector at the middle of pontic, The stress values of four models loaded with vertical forces (150 N) were analyzed.
Results: The maximum stress concentration was located at the crestal bone around implant and stress distribution was more balanced around the teeth except in the model of NRCCP2. Stress distribution was imbalanced in non-rigid connection especially in the NRCCP1 model. The presence of non-rigid connector in bridge increases the stress values in suprastructure and transfers to the adjacent structures. Conclusion: The tooth-implant supported prosthesis should be considered as a valuable prosthetic option. It could be suggested that if tooth and implant abutments are to be used together as fixed prostheses supports, rigid connector is the choice because the prosthesis and implant possess the inherent flexibility to accommodate dissimilar mobility characteristics.
G. Esfahanizadeh, A. Eyvaz Ziaee, Ak. Shams, R. Ghoseiri,
Volume 24, Issue 2 (4-2011)
Abstract
Background and Aims: Considering the great incidence of implant failures due to high stresses around implant and at bone-implant interfaces, the aim of this study was to compare the effects of three different implant-macro designs on the quantity and distribution pattern of stresses around implants.
Materials and Methods: In this experimental in vitro study, three types of implants including Biohorizon (4×10.5 mm), Iler (4×10 mm), and Swiss Plus (4.1×10 mm) were studied by applying photo-elastic method. The implants were placed within photo-elastic models with dimensions of 50×50×10 mm. Then through open tray impressed method, crowns for each implant were constructed and cemented. Vertical and oblique loads of 100 N and 150 N were applied on the cemented crowns within polariscope machine. Then the photographs were evaluated using Isochromatic Fringe Characteristics table.
Results: Under vertical loads of 100 N and 150 N, the values for Biohorizon, Iler, Swiss Plus fixtures at the cervical region were (2.35, 3.60) N, (2.50, 3.10) N, and (1.39, 2.35) N, respectively and in apical region the values were (1.63, 2.35) N, (1.82, 2.35) N, and (2.50, 3.10) N. Under oblique loads, the measures at the cervical region were (4.00, 5.00) N, (1.82, 5.00) N, and (5.20, 6.00) N and in apical region were
(1.39, 2.00) N, (4.00, 2.35) N, and (2.35, 3.00) N, respectively for mentioned implants.
Conclusion: Under vertical loads, the lowest cervical stresses were observed in Swiss Plus fixture and the lowest apical stress values were recorded for Biohorizon fixture. Under oblique loads, the lowest cervical stresses were found in Iler implant and lowest apical stresses were recorded for Bohorizon.
Zafar Mahdavi Ezadi, Ezatolah Jalalian, Mohamad Hasan Salari, Shima Azimzad, Tahmine Safaie, Mahdi Shirazi, Behzad Salari,
Volume 26, Issue 4 (1-2014)
Abstract
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.
Mohamad Reza Khalili, Babak Ziaie, Mahmoud Kazemi,
Volume 26, Issue 4 (1-2014)
Abstract
Background and Aims: Dental implants have been studied for replacement of missing teeth for many years. Productivity of implants is extremely related to the stability and resistance under applied loads and the minimum stress in jaw bone. The purpose of this study was to study numerically the 3D model of implant under thermal loads.
Materials and Methods: Bone and the ITI implant were modeled in “Solidworks” software. To obtain the exact model, the bone was assumed as a linear orthotropic material. The implant system, including implant, abutment, framework and crown were modeled and located in the bone. After importing the model in Abaqus software, the material properties and boundary conditions and loads were applied and after meshing, the model was analyzed. In this analysis, the loads were applied in two steps. In the first step, the mechanical load was applied as tightening torque to the abutment and the abutment was tightened in the implant with 35 N.cm torque. In the second step, the thermal load originated from drinking cold and hot water was applied as thermal flux on the ceramic crown surface in this model.
Results: Thermal analysis results showed that the thermal gradient in the bone was about 5.5 and 4.9 degrees of centigrade in the case of drinking cold and hot water respectively , although the maximum gradient of the whole system was reduced to 14 degrees, which occurred, in the crown by drinking cold water.
Conclusion Thermal stresses were so small and it was because of the low thermal gradient. Maximum stresses occurred in the abutment were due to the tension preloads which were originated from the tightening torque.
Ebrahim Akbari, Ali Mashhadi, Zeinab Azimi, Raheleh Abbas Nazhad, Ahamd Amiri Pichakolaei,
Volume 30, Issue 4 (1-2018)
Abstract
Background and Aims: While there are a lot of information about an illness risk factors, there are still some gaps in understanding factors influencing the progression of disease. Given the important role of psychological factors in physical conditions, the purpose of this study was to compare the cognitive emotion regulation, stress, depression, anxiety, and stress related to life events in people with and without periodontal disease.
Materials and Methods: The type of this study was causal comparative. Research society was all clients referred to dental clinics in Lamerd and Mehr cities, then 50 people with and 50 people without periodontal disease (male and female, 15-49 years old) were selected using purposive sampling. The group without periodontal disease was matched with patient group in terms of demographic characteristics. Both groups completed cognitive emotion regulation questionnaire (CERQ), Depression Anxiety Stress Scale (DASS), and life events questionnaire. Data analysis was conducted with SPSS version 17 using multivariate analysis of variance (MANOVA).
Resultes: Data analysis showed that people with periodontal disease had more stress, depression, anxiety, and stress related to life events than matched control group. The groups had significant differences in the components of self-blame, rumination, positive attention to evaluation and catastrophizing (P<0.05). People with periodontal disease had higher scores in self-blame, rumination and catastrophizing and lower scores in positive attention to evaluating compared with matched control group.
Conclusion: The results showed people who were vulnerable to stressfull situations, depression, and anxiety during their lives, and also use maladaptive emotion regulation strategies, were more susceptible to periodontal disease.
Bahram Kouhnavard, Hosseinali Mahgoli, Somayeh Bolghanabadi, Mohsen Yazdan Aval, Maryam Rostami Aghdam Shendi, Malihe Kolahdouzi,
Volume 31, Issue 2 (9-2018)
Abstract
Background and Aims: Making dental prostheses is sensitive and accurate work and requires powerful and skilled hands. Because of this, the dental prosthesis technicians may suffer harmful effects such as stress and fatigue during the course. The aim of this study was to investigate fatigue, stress and job performance and their relationship with some demographic variables in this community.
Materials and Methods: The present study was cross-sectional and done in 2016. The study population was a group of dental prosthesis technicians that had participated in a national congress in Tehran. Sampling was done by census Two standardized questionnaires on the subjects of fatigue and stress which were distributed among 100 female and male participants and sampling was done by census. Then, the obtained data was analyzed using SPSS16 software and applying descriptive statistics, Pearson correlation test, and ANOVA, T-test.
Results: From the 100 samples, there were 16 females and 84 males with mean age 34.71±7.90 and average work experience of 10.82± 9.01 years. 82 percent of the subjects were married and 42 percent of them were smokers. The results showed that 100 percent of dental prostheses technicians were facing with moderate to severe stresses. The stress and fatigue scores in married ones were higher than the single ones. The results showed a significant relationship between smoking, stress, and fatigue scores (P<0.05).
Conclusion: According to the high level of job stress in the dental prostheses technicians, this problem must be considered, minimized, and more attention should be paid to their psychological and emotional problems.
Ashkan Samkhanian, Asie Eftekhari,
Volume 34, Issue 0 (5-2021)
Abstract
Background and Aims: The stress, job satisfaction and depression can affect the performance of dental professionals in various fields. The aim of present study was to examin the level of stress, depression and job satisfaction among different specialized fields of dentistry in Zanjan provinc, Iran.
Materials and Methods: In this cross-sectional study, the depression, anxiety and stress scale questionnaire (DASS-21) and the Herzberg questionnaire were used to assess job satisfaction. The questionnaires were completed on the web, and the relevant link was sent to all specialists in different fields of dentistry in Zanjan province. Finally, 33 people participated in the study. Data were analyzed after appropriate code allocation using independent T-test and U-Mann Whitney tests and SPSS16.
Results: The results showed the mean of stress (24.4), depression (17.48) and anxiety (13.28) among specialists. The mean of stress and anxiety among female dentists was higher than male specialists, but there was no significant difference between these two variables between the two sexes (P>0.05). In terms of job satisfaction, 21.2% were dissatisfied with their job. By gender, 26.6% of female specialists and 16.7% of male specialists were dissatisfied with their jobs.
Conclusion: Despite the general perception that work conditions are suitable for dental specialists, these people suffer from the stresses, anxiety and depression and may not be satisfied with their job. As these conditions can affect the performance of these people in the workplace, it would be necessary to take measures, to identify, and to increase mental health and job satisfaction.
Mostafa Motallebi, Maryam Sadeghipour, Nika Mehrnia, Mohammad Behnaz, Nahid Mohammadnia,
Volume 35, Issue 0 (5-2022)
Abstract
Background and Aims: Today, academic stress and subsequent test anxiety is one of the most important problems for the last year of high school students. In addition to systemic effects, stress can affect the level of oral health by disrupting oral health behaviors. The aim of this study was to investigate the relationship between stress and variables related to oral health in the final year of high school students prior to University entrance exam.
Materials and Methods: In this descriptive-analytical study, the level of stress and variables related to oral health in 180 students of the final year of high school in Tehran, in three time periods during the academic year 2018-2019, were measured by a questionnaire and one clinical examination. Data were analyzed by Friedman, Bonferroni and Generalized Estimating Equations using SPSS software.
Results: As the exam approaches, some variables related to the oral health, such as toothbrush usage pattern, daily sleep, fast food frequency, and sweet snack consumption, changed (P<0.05). Daily sleep changes were significantly associated with the stress changes (P=0.022). According to the results of the Repeated Measures Analysis, significant changes were observed between the average score of the "Cognitive Error" aspect of three times (P<0.001). Also, according to the results of the Bonferroni Test, significant changes related to the difference in the average score of "cognitive error" 6 months and 3 months before the entrance exam (P<0.001), 6 months and 1 month before the entrance exam (P<0.001), and 3 months and 1 month before the entrance exam (P<0.001) were observed. In all three cases, as the time of the entrance exam approaches, the score of "cognitive error" had decreased significantly. Considering that the lower score in this index indicates a higher level of test anxiety, the closer we get to the entrance exam, the higher the level of test anxiety in the "cognitive error" dimension
Conclusion: The academic stress of the national university entrance exam can affect some oral health variables such as daily sleep, however, it is not related to other variables.
Shima Golban, Hajar Shekarchizadeh, Simin Zahra Mohebbi,
Volume 36, Issue 0 (5-2023)
Abstract
Background and Aims: Considering the problems associated with occupational stress and burnout caused by this stress, this study aimed to determine the academic burnout, dental environment stress, and their association among dental students in Isfahan.
Materials and Methods: This analytical cross-sectional study was conducted in 2020, applying a convenient sampling method. Data collected from undergraduate dental students from Isfahan University of Medical Sciences and Azad University of Isfahan using the validated Persian version of BCSQ-12-SS (Burnout Clinical Subtype Questionnaire) including 12 questions and DES (Dental Environment Stress) including 32 questions. Volunteer students filled in the online questionnaires using social media including WhatsApp and Telegram. Data were analyzed using SPSS26, U Mann-Whitney test, Kruskal-Wallis test, Spearman correlation coefficient, and a linear regression model (level of significance P<0.05).
Results: Among 300 participants (response rate=64%), the mean age was 24.25±2.72, and 54.7% were women. The mean score of academic burnout was 2.61±0.66 of the maximum score of 5. Overload was the most effective dimension of academic burnout. The mean score of DES was 2.80±0.51 of the maximum score of 4. Clinical education was the most effective dimension of DES. A direct correlation was observed between the dental environment stress and academic burnout (P<0.001; r=0.33).
Conclusion: The academic burnout among dental students in Isfahan was moderate and dental environment stress was high. Considering the direct association between the stress and burnout, more efforts should be made to reduce dental environment stress especially in the field of clinical education.
