abbas monzavi

The removal of ceramic veneers is a time-consuming procedure in a dentaloffice. Little research has been done in alternative removal techniques for ceramic veneers.The objective of this study was to evaluate the removal of feldspathic and lithium disilicatereinforced glass ceramic veneers by Er, Cr: YSGG and to measure debonding time and pulpaltemperature increase during veneer removal. Fifty-seven bovine incisor teeth were prepared and divided into 3 groups. Ceramicspecimens with a thickness of 0.7mm, a width of 4mm and a length of 8 mm were fabricatedfrom feldspathic ceramic, lithium disilicate reinforced glass ceramic HT (high translucency) andlithium disilicate reinforced glass ceramic MO (medium opacity) (19 for each group). Specimenswere cemented on the labial surface of incisors using resin cement. The Er, Cr: YSGG laserwas applied to each specimen at 2.5 W and 25 Hz. Debonding time was measured for eachspecimen, and the intrapulpal temperature was detected in 3 specimens for each group. Datawere analyzed via one-way analysis of variance (ANOVA) at significance level of 0.05 (α = 0.05). Mean debonding time was 103.68 (26.76), 106.58 (47.22) and 103.84 (32.90) secondsfor feldspathic, lithium disilicate MO, and lithium disilicate HT respectively. There was nosignificant statistical difference among the groups (P value = 0.96). The intrapulpal temperatureincrease was less than 1°C in all groups. Er, Cr: YSGG can successfully be used to efficiently debond feldspathic and lithiumdisilicate reinforced glass ceramic veneers. There was no significant difference for debondingtime among these ceramic materials. During ceramic laminate veneer removal by laserirradiation, no irritating temperature rise was detected.

Periodontitis is an inflammation of periodontal tissues that is caused by the biofilm of periodontal pathogens. Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is an opportunistic periodontopathogen that can be the cause of periodontal diseases via fimbriae as a virulence factor. In this study, we aimed to determine the expression level of A. actinomycetemcomitans rcpA gene as a virulence factor associated with biofilm formation after antimicrobial photodynamic therapy (aPDT) as a relatively new therapeutic modality.
To determine sub-lethal doses of aPDT against A. actinomycetemcomitans ATCC 33384 strain, we used curcumin (CUR) as a photosensitizer at a final concentration of 40 µmol/ml, which was excited with a light-emitting diode (LED) at the wavelength of 450 nm. Quantitative real-time polymerase chain reaction (qRT-PCR) was then applied to monitor rcpA gene expression in A. actinomycetemcomitans.
10-40 μmol/ml of CUR caused a significant reduction in the growth of A. actinomycetemcomitans compared to control group (P aPDT with CUR leads to decreased cell survival and virulence of A. actinomycetemcomitans. Thus, CUR-aPDT can be used as an alternative approach for the successful treatment of periodontitis in vivo.

This study aimed to analyze functional stresses around short and long implant-supported prostheses with different crown heights.
Four three-dimensional (3D) models were designed with SolidWorks 2015. In models 1 (control) and 2, three dental implants (second premolar 4.1x8 mm, molars: 4.8x8 mm) were placed. In models 3 and 4, three dental implants (second premolar 4.1x4 mm, molars: 4.8x4) were placed. Residual bone height was 10 mm in groups 1 and 2 (grafted bone) models and 6 mm in groups 3 and 4. The crown heights were modeled at 11.5 mm for groups 1 to 3, and 15 mm for group 4. The applied oblique force was 220 N to simulate chewing movements. The maximum von Mises and principal stresses on the implants and the supporting tissues were compared using the 3D finite element method.
In all models, the highest stress value was seen within the most coronal part of bone (crestal bone), which was cortical or grafted bone. The highest stress values in the bone supporting the implant neck were seen in the premolar region of each model, especially in model 4 (291.16 MPa). The lowest stress values were demonstrated in the molar region of model 3 (48.066 MPa). The model 2 implants showed the highest von Mises stress concentrated at their neck (424.44 MPa).
In atrophic posterior mandible with increased crown height space, short implants with wider diameter seem to be a more feasible approach compared to grafting methods.

Today bleaching is a routine noninvasive alternative for treatment of discolored teeth. The concern has been raised whether or not oxidizing reaction during this process, might endanger integrity of the teeth and raise the risk of caries formation. The aim of this study was to determine whether conventional or laser activated bleaching predispose teeth to develop caries or not.
Sixty human molars were mounted on acrylic cylinders and Knoop microhardness (KHN) and DIAGNOdent (DD) values of them were recorded. They were divided into four experimental groups; G1)conventional bleaching with 40% Hydrogen peroxide gel G2) Diode laser assisted bleaching with same gel. G3)Nd;YAG laser assisted bleaching with the same gel. G4)control group. After bleaching, all samples were subjected to a three day pH cycling regimen and then, KHN and DD values were measured.
All groups had significant reduction in KHN values. . It seems that there is no statistically meaningful difference between changes in enamel microhardness of sample groups and all groups have changed in a similar amount. Reduction of DD scores were significant in Diode laser and conventional groups, however changes in Nd:YAG laser and control groups were not significant. Changes in DD values have followed a similar pattern among groups, except in G1-G4 and G2-G4 couples. Conventional and Diode laser group had a meaningful difference in reduction of DD values in comparison with control group.
It can be concluded that bleaching whether conventional or laser activated method, does not make teeth vulnerable to develop carious lesions.

Autism spectrum disorder (ASD) is a common disorder among children which despite painstakingly effort, it is not yet possible to be precisely detected using paraclinical methods. On the other hand, early detection, before 18th month, has pivotal role in treatment procedure. In this study, we present a method for early diagnosis of ASD based on the qualitative analysis of the Electroencephalogram (EEG) signal. We develop a new domain for quantifying the quality of interaction is present. We name it 'stretching – folding space’ (SFS). This domain is based on cybernetics, holistic and information-based analysis approaches. Therefore, it provides a non-deterministic approach to the biosignals. We collected data from 60 normal and 60 children with ASD in the range of 3-10 years old. We extracted features from the data in the SFS domain. The design of the study is self-controlled, meaning that each child serves as his/her own control. Each subject in the study watched a cartoon with and without sound, and the EEG signals were recorded. Statistical tests are applied on the extracted qualitative features in the SFS domain. The difference between the features of the data for each group (normal and ASD) was extracted, and the difference were compared between the groups. The results indicate that there is a statistically significant difference between the SFS features of normal and autism children. We conclude that our proposed method can serve as a new signal processing tool for diagnosing autism.

The most important method of recognizing behavior of recurrent maps is to plot Bifurcation Diagram. Conventional method for plotting is to generate a variety of time series for different values of model parameter and plotting these points with respect to it after transient state. Bifurcation Diagrams are destitute of analytical interpretations for determining the cause of chaotic and period doubling behaviors. In this study, a diagram is presented which can be called Qualitative Bifurcation Diagram (QBD). One of the special features of Qualitative Bifurcation Diagram is recognition of parameter values and initial conditions, in which, the map has periodic, Aperiodic or chaotic behavior and for recognizing these behaviors, no primary information with regards to the map is needed.
The implementation of QBD on the logistic map indicates high susceptibility of the algorithm in distinguishing high periods and periodic windows; it has not only reduced the calculation time, but also has made it possible to examine initial conditions and logistic parameter effects with high velocity simultaneously. In spite of existence arrangement in Bifurcation Diagram, the result showed that logistic is not a mosaic arrangement, but it has a dynamic arrangement.
This article dealt with the investigation of Lyapunov Exponent as one of the tools of chaos examination which is analyzed analytically.

This study aimed to assess the Scanning Electron Microscope (SEM) analysis of tooth surface irradiated by erbium:yttrium–aluminum–garnet (Er:YAG) laser with various parameters. Number of 25 extracted human third molars free of caries were used in this study. The teeth were put into 5 groups for laser irradiation as follows: group 1 (power: 0.5 W, Energy: 50 mJ); group 2 (power: 1 W, Energy: 100 mJ); group 3 (power: 1.5 W, Energy: 150 mJ); group 4 (power: 2 W, Energy: 200 mJ); group 5 (power: 2.5 W, Energy: 250 mJ). All samples were prepared by repetition rate of 10 Hz and duration of 230 µs, using a non-contact handpiece at a distance of 4 mm. Then, the samples were prepared for SEM examination. SEM evaluation of every 25 samples, treated by Er:YAG, showed that all groups had exposed dentinal tubules without any melted area or cracks. In this study we used SEM to investigate ablated dentine with different parameters of Er:YAG laser energy. Our findings support these conclusions. All powers of laser below 3 W are proper for ablation, and make no cracks.

Peri-implantitis is one of the most common reasons for implant failure. Decontamination of infected implant surfaces can be achieved effectively by laser irradiation; although the associated thermal rise may cause irreversible bone damage and lead to implant loss. Temperature increments of over 10ºC during laser application may suffice for irreversible bone damage.Purpose of Study: The purpose of this study was to evaluate the temperature increment of implant surface during Er:YAG laser irradiation with different cooling systems. Three implants were placed in a resected block of sheep mandible and irradiated with Er:YAG laser with 3 different cooling systems namely water and air spray, air spray alone and no water or air spray. Temperature changes of the implant surface were monitored during laser irradiation with a K-type thermocouple at the apical area of the fixture. In all 3 groups, the maximum temperature rise was lower than 10̊°C. Temperature changes were significantly different with different cooling systems used (P<0.001). Based on the results, no thermal damage was observed during implant surface decontamination by Er:YAG laser with and without refrigeration. Thus, Er:YAG laser irradiation can be a safe method for treatment of peri-implantitis.

The aim of this study was to compare the level of agreement between four operators with different levels of experience for two methods of detecting secondary enamel and dentin carious lesions in composite restored teeth. Sixty teeth of 40 patients with with secondary carious lesions in the composite resin were selected. The teeth were examined by two methods; visual inspection and a laser fluorescence device (DIAGNO dent pen 2190) by four operators including an undergraduate student, a dentist with 5 years of clinical experience, a general dentist with 12 years of clinical experience and an oral and maxillofacial radiologist. Cohen''s kappa statistic was applied in order to assess the agreement between the diagnoses performed by the four operators with each diagnostic method. The diagnosis performed by different operators achieved an excellent agreement with high ICC. DIAGNOdent can be a useful device for secondary caries detection in posterior teeth as an adjunct to visual examination.

Little is known about the interaction of tissue conditioners and modeling plastics.This study evaluates the influence of a variety of commercial tissue conditioners on alteration of viscoelastic properties of modeling plastics. In this in vitro study, the dynamic viscoelastic properties of four commercially available tissue conditioners (TC), Visco-gel (VG), GC Soft-Liner (SL), FITT (FT), and Coe Comfort (CC), relined to modeling plastics with a thickness of 2mm were evaluated after 1 and 7 days of water immersion with the use of storage modulus, loss modulus, and tan delta parameters. Values for these three parameters for each tissue conditioner were statistically analyzed by Kruskal Wallis and Mann Whitney tests with P value sets at<0.05. Complex modulus and loss tangent values of TC were not significantly different among specimens containing 0, 2, 5 and 10 wt.%-SZ, respectively. In FT and TC containing 2 wt.%-SZ, these values were not significantly different between 1 and 28 days in both water- and saliva immersions. The results suggest that relining with modeling plastics does affect TC’s inherent dynamic viscoelastic properties, while the other tissue conditioners investigated may be found to have changed viscoelastic properties as a consequence of vicinity to the modeling plastics.

Accurate delivery of torque to implant screws is critical to generate ideal preload in the screw joint and to offer protection against screw loosening. Mechanical torque-limiting devices (MTLDs) are available for this reason. In this study, the accuracy of one type of friction-style and two types of spring-style MTLDs at baseline, following fatigue conditions and sterilization processes were determined. Five unused MTLDs were selected from each of Straumann (ITI), Astra TECH and CWM systems. To measure the output of each MTLD, a digital torque gauge with a 3-jaw chuck was used to hold the driver. Force was applied to the MTLDs until either the friction styles released at a pre-calibrated torque value or the spring styles flexed to a pre-calibrated limit (target torque value). The peak torque value was recorded and the procedure was repeated 5 times for each MTLD. Then MTLDs were subjected to fatigue conditions at 500 and 1000 times and steam sterilization processes at 50 and 100 times and the peak torque value was recorded again at each stage. Adjusted difference between measured torque values and target torque values differed significantly between stages for all 3 systems. Adjusted difference did not differ significantly between systems at all stages, but differed significantly between two different styles at baseline and 500 times fatigue stages. Straumann (ITI) devices differed minimally from target torque values at all stages. MTLDs with Spring-style were significantly more accurate than Friction-style device in achieving their target torque values at baseline and 500 times fatigue.

Accurate recording of implant location is required to achieve passive fit and have the implants without stress concentration. The aim of this in-vitro study was to evaluate the dimensional and angular accuracy of open-tray and closed-tray impression techniques using polyether impression material and also to assess the surface detail reproduction of the tooth while impression making. One reference metal model with 2 implants (Implantium) on the position of the maxillary second premolar and first molar and one molar tooth for evaluation of surface details was prepared. 27 polyether impressions of these models were made (9 using open-tray, 9 using closed-tray techniques and 9 were made just of the surface of the teeth without any implants). Impressions were poured with ADA type IV stone. Coordinate Measuring Machine was used for measuring the dimensional accuracy and video measuring machine for surface detail reproduction. All of these measurements were compared with the measurements on the reference model. Data were analyzed by and compared by T-test and One-way ANOVA. There was a significant statistical difference between open-tray and closed-tray techniques (P<0.001). There was no significant difference in the surface detail reproduction of open-tray and Closed-tray techniques and impression making with or without the implants (P>0.05). The accuracy of open-tray impression technique was more than closed-tray technique. The surface detail reproduction of the tooth was not affected by impression technique.

The aim of this study was to investigate the Scanning Electron Microscope (SEM) analysis of tooth surface irradiated by different parameters of Er:YAG laser. 15 caries-free extracted human third molars were used in this study. The teeth were put into 5 groups for laser irradiation as follows: Group 1 (power: 2.5 W, Energy: 250 mJ); Group 2(power: 3 W, Energy: 300 mJ); Group 3 (power: 3.5 W, Energy: 350 mJ); Group 4 (power: 4 W, Energy: 400 mJ); Group 5 (power: 4.5 W, Energy: 450 mJ). All samples were prepared by repetition rate of 10 Hz. Then,the samples were prepared for SEM examination. The SEM images showed cleaned ablated surface and exposed dentinal tubules, without production of smear layer. It can be concluded that Er:YAG laser can be an alternative technique for surface treatment and can be considered as safe as the conventional methods,like turbine and bur.

Whilst there is an extensive descriptive literature on the effective lecturing, there are few studies on student's perspective toward the attributes of effective lecture sessions. The aim of this study is to explore student's viewpoints on factors affecting the quality of lecture sessions.

This was a two-stage descriptive study in which 25 dentistry students at clinical stage, studying at Tehran University of Medical Sciences attended a focus group session and represented their viewpoints about weaknesses and strengths of lecture sessions of theory courses. A questionnaire was developed according to the students’ statements. Features of an effective lecture session were categorized into 4 groups of factors related to the lecturer, content, physical facilities available in class, and educational management. Reliability was assessed through Spearman correlation analysis. This questionnaire including 45 items was distributed among 130 students studying at fourth to sixth-year, in the School of Dentistry. Students’ agreement with each item in questionnaire was measured using 5-point Likert scale.

Ninety seven questionnaires were collected. Items of factors related to the lecturer mostly regarded by students, among them were “oral presentation techniques” (mean score of 4.64), “presenting case to demonstrate the association between theory and practice” (4.63), and “the lecturer’s ability to associate the content” (4.55) which received the highest scores.

Dentistry students at clinical stage thought that the role of lecture in theoretical courses is very important. They believed that the ability of lecturer in organizing and explanation of the content plays the most important role in giving an effective lecture.

Bond strength between veneers ceramic any zirconia framework is the weakest component in the layered structure. This bond was sensitive to the liner application and type of veneer ceramic. This study examined the core-veneer microtensile bond strength of a CAD/CAM (computer aided design/computer assisted manufactured) zirconia ceramic by comparing two ceramic veneers with and without liners. Disc-shaped (19.4×3.5mm) specimens were fabricated using CAD/CAM zirconia core materials (Cercon). Half of the discs were left white and the others were colored with an A2 liner. The specimens were veneered with Ceram Kiss or Zirkonzahn ICE veneering ceramics (3.5 mm). The discs were then cut into microbars (CC, ZC, CW, ZW) and the microtensile strength of the core-veneer bond was calculated. The specimens were analyzed by SEM and the data were compared using one-way ANOVA and Post hoc tests. The type of veneering ceramic (Ceram Kiss) and liner application (coloring) significantly affected the core-veneer microtensile bond strength (P<0.0001). The Zirkonzahn layer (ZC, ZW) did not show significant differences (P=0.08). Careful selection of veneering ceramics and liner applications can be recommended as they have significant roles in microtensile bond strength of core veneered restorations.

In patients with complete denture, some clinicians have used modelling plastic impression compound (MPIC) along tissue conditioner (TC) materials simultaneously. Little information is available on the composition of these materials and the interaction between them. The purpose of this study was to evaluate the influence of two components of MPIC on the structure and chemical composition of TC. In this experimental study, MPIC specimens were provided in 25×2 mm discs. Specimens were randomly divided into three groups and were immersed in ethanol 70%, plasticizer (dibutyl phthalate) and a mixture of them (ethanol 70% and dibutyl phthalate). All of the discs were weighed with a digital balance before and 2, 4, 6 and 24 hours after immersion. Values were analyzed by non parametric Kruskal-Wallis (α= 0.05) and SPSS 16 for Windows (SPSS Inc., Chicago, IL) was used for statistical analysis. Statistical analysis indicated significant differences among all groups (p>.05). Dibutyl phthalate (DBP) had high impact on the solubility of MP, while the mixture of dibutyl phthalate (DBP) and ethanol demonstrated the highest impact.

Educational evaluation is a process which deals with data collection and assessment of academic activities’ progress. In this research, educational evaluation of Dentistry School of Tehran University of Medical Sciences, which trains students in undergraduate and residency courses, was studied. This descriptive study was done with a model of educational evaluation in ten steps and 13 fields including purposes and mission objectives, management and organization, academic board members, students, human resources and support, educational, research, health and treatment spaces, educational, diagnostic, research and laboratory tools, educational, research, health and treatment programs and courses, process of teaching and learning, evaluation and assessment, alumni, and patients satisfaction. Data were collected using observation, interviews, questionnaires, and checklists. Results of the study were mainly qualitative and in some cases quantitative, based on defined optimal situation. The total mean of qualitative results of educational evaluation of dentistry school in all 13 fields was 55.98% which is relatively desirable. In the case of quantitative ones, results of some fields such as treatment quality of patients and education and learning of the students were relatively desirable (61.32% and 60.16% respectively). According to the results, educational goals and missions, educational and research facilities and spaces which were identified as the weakest areas need to be considered and paid more serious attention.

Ethical indecency and fineness have paramount importance in ethics. If it is denied, ethics will be considered relative. In this article, its definitions and aspects will be discussed using the Islamic sources. The data have been collected from reliable Islamic sources and search engines such as Yahoo, Google, and Iran Medex using key words such as “innate goodness and badness”, “ethical indecency and fineness” and “rational deductions”. The five found definitions are " compatibility and incompatibility with habitude"," aims agreement"," perfection and imperfection", “admiration and criticism” and “innate tendencies”. Human humors can be defined as brutal humor and spiritual humor. The first definition doesn’t give us a scale to differentiate ethical from unethical issues and the second one can’t prove spiritual deeds comprehensively; unless its correctness has been accepted. The aims have three types: individual aims, common aims and favorable aims. Individual aims lead to ethical chaos but common aims can support ethics. Common aims neither clarify the essence of an action nor concern innate "goodness and badness". They are really the explanations for reasonable indecency or fineness”. Favorable aims seek God's satisfaction and need good intends. Perfection and imperfection is actually another expression for “compatibility with humor”. "Admiration and criticism" is the only definition of optional conducts. It is defined as "appropriateness of admiration and criticism", " order of admiration and criticism"," having capability to be admired or criticized", "admiration and criticism by themselves "and " the wise opinions for admiration or criticism". “Innate tendencies” are another explanation for “compatibility with humor”. In defining “ethical indecency and fineness”, we should consider standards with ethical applications like compatibility with celestial humor, perfection and imperfection, innate tendencies and common aims.

Alginate is one of the most widely used impression materials in dentistry. Currently, a variety of alginates are available on the market. Quality control should be performed for all dental materials used in Iran. The aim of the present study was to evaluate several parameters of Plastalgin alginate (Made in France) according to the currently valid international standard for dental alginate impression materials.

The studied parameters were: working time, setting time, compressive strength, permanent deformation and strain in compression. All factors associated with packaging were also evaluated. All tests were performed in accordane with ISO or ADA standards and 6 specimens were employed for each test.

The working time of Plastalgin was within standard limits and the mean setting time was found to be 2 minutes and 28 seconds. The strain in compression, permanent deformation and mean compressive strength was 7/35%, 3/25% and 0/74 Mpa, respectively. Our findings did not confirm the information listed on the Plastalgin® packages.

The investigated parameters were in accordance with ISO standards, except for permanent deformation. Our findings did not correspond with the information written on the packages. Further studies are required to determine the properties of this material.