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Showing 7 results for Erfan
Polymerisation shrinkage versus layer thickness of a dentine bonding resin: Method development
T. Jafarzadeh , M.  erfan , Dc. Watts , A. Cash ,
Volume 15, Issue 2 (8 2002)
Abstract
Dentine bonding systems are usually unfilled, and so their shrinkage may be significant. High shrinkage may cause internal stress at the interface between resin-composite restoration and the dentine substrate. Failure of the adhesive interface may be observed due to the interna! stress. The aims of this study were:A) To obtain a suitable method for measuring the kinetics of polymerisation shrinkage in unfilled resm at different thicknesses, particularly for thin films.B) Consideraing the effect of thickness on shrinkage.Scotchbond Multipurpose (3M) adhesive bond resin was used. To overcome the particular challenges presented by thin films, a filled-ring measurement procedure was used. Also, a non-contact laser analogue displacement sensor system was developed and applied to measure polymerisation shrinkage. Regression analysis was performed on a complete data set. Non-linear regression analysis established a logarithmic relationship between polymerisation shrinkage and layer thickness. The method applied in this study was found to be sensitive and accurate procedure for determining photo-polymerisation shrinkage of thin films. Polymerisation shrinkage increased with logarithmic of the adhesive thickness.
Measuring the degree of conversion of ScotchBond MP Plus Adhesive, Single Bond, Prompt L-Pop and an experimental bonding resin
Ts. Jafarzadeh Kashi, M. Erfan ,
Volume 18, Issue 1 (30 2005)
Abstract

Statement of Problem: The quantity of remaining unreacted double bonds may be a significant factor pertaining to the mechanical, physical and chemical properties of restorative resins. Insufficient polymerisation within the hybrid layer may cause significant differences in the quality of this layer, and act as a reservoir for monomer release thus increasing cytotoxic potential.

Purpose: The aim of this study was to measure the degree of conversion of three generations of 3M dentin bonding agents and an experimental dentin bonding agent

Materials and Methods: The quantity was determined from the transmission IR-spectrum of the materials before and after polymerization. ScotchBond MP plus adhesive, SingleBond, Prompt L-Pop, and an experimental dentin bonding were used to measure degree of conversion. Six repetitions of each bonding were investigated. Time of light curing was 120s. Kruskal-Wallis and Mann-whitney test were used to compare groups with P<0.05 as the limit of significance.

Results: The results showed a significant difference between groups (P<0.01). A trend of increasing in Singlebond conversion obtained in comparison with ScotchBond MP plus adhesive, Prompt L-Pop and experimental dentin bonding. The degree of conversion was not statistically significant among the other dentin bondings. No significant difference was found between conversion of the experimental dentin bonding and ScotchBond MP plus adhesive (P=1.00) with P<0.05 as the limit of significance.

Conclusion: Dentin bonding technology continues to evolve toward simpler systems. However, Prompt L-Pop as a self-etching adhesive does not show the trend of increasing the degree of conversion. However, the performance of these simpler systems must be further investigated.


In vitro evaluation of fracture resistance of Fiber-Reinforced Composite inlay bridges in upper anterior and lower posterior teeth
E. Jalalian , S. Banava , S. Erfani ,
Volume 20, Issue 3 (4 2007)
Abstract

Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC) and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.

Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195) with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.

Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and  1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T  test a significant statistical difference was observed between two groups (P<0.001). The fracture resistance of anterior samples was lower than the posterior ones.

Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.


Evaluation of polymerization of an experimental bonding resin cured with light emitting diodes using Differential Scanning Calorimetry
T. Jafarzadekashi, M. Erfan, M. Mirzaie, S. Kalbasi,
Volume 22, Issue 1 (11 2009)
Abstract

Background and Aim: Extent of polymerization (Ep) is the rate at which methacrylate C=C bonds are converted to aliphatic C-C bonds. The higher the Ep value, the better the polymerization of the polymer. If the polymer dose not polymerize sufficiently, it could have destructive effects e.g. releasing monomer, initiator, free radical or insufficient polymerization of hybrid layer. Therefore, measuring the Ep value is very important. Light-emitting diodes (LEDs) are becoming increasingly popular in dental practice as they have a long life expectancy. LEDs do not generate infrared wavelength, and have a constant light output. Therefore, comparison of LED and Quartz tungsten halogen (QTH) from the point of Ep is important. Differential Scanning Calorimetry (DSC) is a proper tool for determining the Ep value, monitoring the process of reaction and reaction kinetics. The aim of this study was to measure the Ep value of a dental bonding containing camphorquinone/amine photoinitiator which were cured by LED and QTH using DSC.

Materials and Methods: In this experimental study, 2.5 mg of bonding material were placed in DSC aluminum pans. Two different light cures, LED & QTH (Coltene Company Coltolux ®75 LED Curing Light), were used in this study. The light guide was positioned at a distance of 9mm from the base of the sample chamber. Each sample was photopolymerized for 30 seconds, and the DSC curves were obtained after 100 seconds from initiation of photopolimerization of each sample, at both 23oC and 37oC. The heat of photopolymerization (DH) was calculated from the area under the peak of the differential temperature curve. Five samples were used for each condition. The data was analyzed by two-way ANOVA.

Results: There was highly significant difference between two temperatures in the experimental bonding (pvalue<0.001). Representative DSC curves showed the same kinetic behavior for LED and QTH.

Conclusion: The results revealed that the Ep generated by high power density QTH was the same as that of produced by second generation of LED.


Comparison of shear bond strength and microleakage of Scotchbond multi-purpose (MP) adhesive system and an experimental dentin bonding agent based on standard of ISO TR 11405
T. Jafarzadeh Kashi, M. Erfan, A. Nezadi Niasar,
Volume 22, Issue 3 (1 2009)
Abstract

Background and Aim: Evaluation of shear bond strength and microleakage of bonding agents is important as these properties play main roles in adhesion of composite to dental tissues. Microleakage results in bacterial penetration into dentin tubules and enamel surfaces and causes sensitivity and recurrent caries followed by destruction of composite filling. Insufficient shear bond strength results in early failure of filling in low masticatory forces. The main goal of this study was to compare the microleakage and shear bond strength of an experimental adhesive and Scotchbond multi-purpose (MP) adhesive system.
Materials and Methods: In this experimental study, sixty extracted caries free human molar teeth were randomly assigned into 4 groups of 15 each for shear bond strength. Variables were bonding agents, enamel and dentin. Twenty teeth assigned into 2 groups of 10 each were used for valuation of the microleakage. Microleakage and shear bond strength were performed according to ISO TR 11405. All data were analyzed with parametric and non-parametric tests according to their normality distribution. Also, Weibull distribution performed on data.
Results: Data obtained from both microleakage and shear bond strength tests showed no significant difference between the experimental bonding and Scotchbond MP bonding (P>0.05). Furthermore, there was no significant difference between the microleakage of occlusal and gingival parts of both bondings (P>0.05).
Conclusion: Experimental adhesive bonding showed acceptable results regarding microleakage and shear bond strength. It may be concluded that the experimental dentin bonding had a comparable performance quality with that of commercial system.


Degree of conversion of micro-hybrid, nano-hybrid and Ormocer composites using LED and QTH light-curing units
Tahereh Sadat Jafarzadeh Kashi, Mohammad Erfan, Akbar Fazel Najafabadi, Seied Mostafa Fatemi, Marjan Behroozibakhsh, Haleh Hali, Hosein Bagheri Gorgani,
Volume 25, Issue 2 (9 2012)
Abstract

Background and Aims: The aim of this study was to measure the degree of conversion (DC) of three types of composite resins (micro-hybrid, nano-hybrid and Ormocer) with different light curing units (LED LCU and QTH LCU) in two depths.

Materials and Methods: Three commercially available dental resin composites were used in this study: (Tetric Ceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Tetric Evoceram, Ivoclar Vivadent, Liechtenstein-A2 shade), (Ceram X, Dentsply, Germany-M2 shade). Specimens were divided into two groups, 5 specimens were photo-activated by QTH unit (Coltolux 75-Colten) and the other five specimens were cured by LED (Demi-Kerr). Then each specimen was sectioned at the top surface and at 2-mm depth. The DC was measured by FT-IR
(Bruker-tensor 27). The data were analyzed by 3-way ANOVA test.

Results: There was significant difference between tested composite resins (P<0.001). The results of top surfaces were significantly different from those observed at 2-mm depth (P<0.001). The type of curing unit affected the polymerization of Ceram X resin composite.

Conclusion: This study showed a significant difference in the degree of conversion in different thicknesses within three groups of resin composites.


Evaluation of computer knowledge and information literacy among dental students of school of dentistry, Tehran medical sciences, Islamic Azad university in 2016
Fatemeh Shahsavari, Maryam Jolehar, Mohammad Javad Kharazi Frad, Shahrokh Erfanmanesh,
Volume 32, Issue 1 (7-2019)
Abstract
Background and Aims: Use of computer and internet in our modern and digitalized society is an efficient tool to be up to date and fulfil the information gaps. The aim of this study was to evaluate the extent of computer and internet usage among dental students of Islamic Azad University, Tehran, in 2016.
Materials and Methods: This descriptive study for evaluating access and usage of computer and internet by dental students was done using a researcher-made questionnaire on 401 dental students. Validity and reliability (Kappa: 0.82) of the questionnaire was confirmed. Statistical analysis was done by SPSS22 using descriptive and Logistic regression analyses.
Results: More than 95% of the students had access to the computer and Internet. 45.6% of students reported their skills were in the basic level. The major use of computer among the students was internet but only 13.2% of students used Microsoft Office program. The students used the internet for dental subjects even monthly (34.9%) or weekly (29.4%). Only 9.7% of the students had participated in educational workshop for learning methods of research. The most limitation was internet velocity. Positive correlation was found among prospering ownership status (P<0.001), economic status (P=0.05), level of education semester (P=0.038) and the computer & internet usage (what’s more in terms of access and also in terms of improve information and knowledge).
Conclusion: Based on the results, a higher economic level, higher level of education, and property ownership made better access to the computer and Internet. However, computer skills should be more concerned in educational program.

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