Bond strength of resin cements to noble and base metal alloys after two surface treatments

The reported bond strengths of resin cements to metal alloys depend on the metal used, the conditioning methods and the adhesive resins. The aim of this study was to evaluate the bond strength of resin cements to two alloys [Degubond 4 and Verabond] after sandblasting or using Silano-Pen. Eighty disk shaped specimens [6mm diameter and 2mm thickness] of Verabond or Degubond 4 were cast according to the manufacturer's instructions. After mounting in auto polymerizing acryl, all samples were polished with a 600 grit silicon carbide paper under water. Half of each alloy's samples were randomly sandblasted with 50micro A1[2]O[3] and the other half were flamed with Silano-Pen device after sandblasting with 110 micro A1[2]O[3]. Cylinders of composite resin [Z250] were cured and then cemented to the prepared substrates by either Panavia F2 or RelyX Unicem. All specimens were stored in distilled water at 37°C for 24 hours and were subjected to 2000 thermal cycles [5-55°C], then submitted to shear bond strength [SBS] test using Universal Testing Machine at 0.5mm/min speed, until failure. SBS was analyzed by three way ANOVA [alpha=0.05]. Failure patterns were determined using stereomicroscope with 40X magnification. Both cements provided stronger bond to Verabond compared to Degubond 4 [p<0.001]. Comparing the surface treatments, Silano-Pen provided higher SBS of RelyX Unicem to both alloys. Panavia cement resulted in higher bond strengths to sandblasted Verabond alloy [p=0.003], but after treatment with Silano-Pen device RelyX Unicem showed higher bond [p=0.011]. When cementing Verabond or Degubond 4 by RelyX Unicem, Silano-Pen provided a stronger bond, but in case of using Panavia F2, treatment with Silano-Pen or sandblast resulted no difference in bond strength

[EDTA dentin conditioning and Micro-shear bond strength using SE and SEM]

The main objective of using adhesive material is the improvement of restorative materials bonding to dentin surface in clean environment. The aim of this study was to investigate the effect of EDTA on bond strength of composite resin to dentin surface when used at different times and concentrations prior to application of adhesive systems by employing Scanning Electronic Microscope [SEM]. A total of 100 dentin samples were prepared from 50 human premolars. These samples were divided into two groups according to bonding type [Clearfil SE Bond =group I, Futurbond NR=group II] and each one was classified 5 subgroups according to time and concentration of EDTA as follows: 1 - Control. 2- EDTA 15%, 30 seconds. 3 - EDTA 15%, 60 seconds. 4 - EDTA 24%, 30 seconds. 5 - EDTA 24%, 60 seconds. These samples were conditioned and composite cylinders were adhered to them. After 500 cycles of thermocycling, the testing for micro-shear bond strength was conducted on these samples. Another 10 samples were demineralized for 30 seconds with 6NHCL and deproteinized with 2.5% Naocl for 10 minutes, air dried with desiccators and viewed under SEM. Data were analyzed using one-way as well as three-way ANOVA and Tukey tests. The mean Micro-shear bond strength in group I [Clearfil SE bond] were: 31.88 [ +/- 13] for subgroup 1, 28.4 [ +/- 13] in subgroup 2, 29.8 [ +/- 9] in subgroup 3, 29.2 [ +/- 11] in subgroup 4, and 32.7 [ +/- 12] in subgroup 5. The mean Micro-shear bond strength in group 2 [Futurbond NR]: were: 22.6 [ +/- 10] for subgroup 1, 28.5 [ +/- 9] in subgroup 2, 27.3 [ +/- 10] subgroup 3, 32.4 [ +/- 15] in subgroup 4, and 31.1 [ +/- 14] in subgroup 5. There were no significant differences between the samples conditioned and the ones not conditioned with EDTA, time and the concentration of EDTA applied and also the two bonding types. EDTA conditioning prior to use of the two bonding agents under investigation in this study did not improve the bonding strength of the self etch systems, neither did the time and the concentration of EDTA applied

[Antiviral effects of different sterilization and disinfection methods on internal tubes of dental handpiece]

Dental handpieces are the most commonly used instruments in dentistry and their cross contamination is very high due to their direct contact with blood and saliva. The purpose of this study was to evaluate the antiviral effects of formalin tablets and autoclave on internal lumens of dental handpieces. This experimental study was designed in order to evaluate the effect of different materials and methods of sterilization and disinfection on virus elimination from internal spaces and interior chambers of dental turbines. Four study groups were composed of: 1] Vacuum autoclave, 2] Non vacuum autoclave, 3] Ten Para Formaldehyde tablets, and 4] Twenty Para Formaldehyde tablets. Nine turbines were tested in each group after preliminary washing, drying and autoclaving. The internal tubes and spaces were then contaminated with Polio and Herpes Simplex virus type I. Antiviral agents and devices were used according to the manufacturers' instructions. Two cell culture samples were obtained from each handpiece, after washing them with sterile distilled water and MEM [Minimum Essential Medium]. In each group one handpiece was designated as control. The culture results were recorded after one week. Autoclaving was perfectly effective on both Polio and Herpes Simplex virus type I in all groups [vacuumed, non-vacuumed, with or without lubricant]. Formalin tablets were 100% effective only on polio virus, and in the 20 tablet group turbines without lubricant. These tablets killed the Herpes Simplex virus in all groups. According to the results of this study, autoclaving is the best method of virus elimination in dental handpiece

[Evaluation of disinifecting of 5% sodium hypochlorite solution diluted to 2:100 along with the use of disposable covers on HBV contaminated dental office surfaces and equipments]

The efficiency of disinfecting materials and procedures in removal of contamination from dental surfaces and equipments is essential. In authors' previous study, daily use of 2:100 dilution of 5% sodium hypochlorite in water and disposable covers were recommended since HBV contamination was found on semi-critical parts of the operative dentistry department. The aim of this study was to evaluate the HBV contamination following application of the recommended procedures. The study was conducted in two parts. In the first cross-sectional part, samples were collected from 17 sites of dental surfaces. In the second interventional part samples were collected from 10 sites of 9 dental and 3 sites of 2 light cure units, before and after disinfection with 5% sodium hypochlorite solution diluted to 2:100. Sterile cotton swabs moistened with sterile BSAS [Bovcine Serum Albumin in Sodium Chloride] solution were used for sampling. Samples were tested by PCR technique in Pasteur Institute, Iran. None of the samples collected in the first part of the study showed contamination. In the second part of the study, from 96 samples taken from various parts of dental and light cure units, before and after disinfecting, there was only on HBV contaminated site before disinfection which showed not contamination after disinfection. Based on the results of this study, disinfecting procedure with 5% sodium hypochlorite solution diluted to 2:100 along with using disposable covers is effective in preventing HB contamination

Postoperative thermal sensitivity reduction after amalgam fillings; A clinical evaluation and presentation of a new method

Prepared cavities are usually treated with liners prior to amalgam placement. Light cured glass ionomer [RMGI] have been widely used for this purpose. The aim of this study was to compare the effect of RMGI on decreasing postoperative sensitivity with a new method of applying self etch bonding and glass ionomer simultaneously. In a blind randomized clinical trial study, A total of 36 patients with 2 deep caries in their posterior teeth [cavities with less than 2 mm distance from pulp in radiography] were included. Diagnostic tests [cold-heat, percussion, electric pulp test] were performed for each tooth prior to final restoration. After cavity preparation, one tooth was treated by light cured glass ionomer, the next one with SE bond and glass ionomer randomly, followed by amalgam restoration. Diagnostic tests were performed three days, thirty days and three months after amalgam restoration. The statistical analysis was performed using SPSS software version 11.5 as well as Friedman and Wilcoxon signed-rank tests. In second follow up, the sensitivity to cold was significantly less than the conventional method [P < 0.05] in our suggested compound method. However, there was no significant difference between the two groups when using the other vitality tests. Using SE bond and light cured glass ionomer simultaneously was an effective new method of decreasing the postoperative sensitivity in short term, [1 month] although, there was no difference between the two groups in the long term

[Comparison of nanoleakage in composite restorations following application of self-etch and total-etch adhesives in primary and permanent teeth]

Nanoleakage can cause discoloration around restoration margins, secondary caries, postoperative sensitivity and finally loss of restoration, thus adequate hybrid layer is of primary importance in prevention of nanoleakage in adhesive restorations. Because of structural differences between primary and permanent dentin, evaluation of nanoleakge in primary teeth is very important. The aim of this study was to evaluate the nanoleakage in composite restorations following application of self -etch and total-etch adhesives in primary and permanent teeth. In this experimental study, Cl V cavities were prepared in buccal surfaces of 20 extracted primary molars and 20 extracted premolars. Each group was divided into 2 subgroups: In group [A], Gluma One Bond and in group [B], iBond adhesive materials were applied. After silver nitrate staining, specimens were mesiodistally sectioned and polished and then SEM examination was carried out to measure the nanoleakage .Data were analyzed statistically using, ANOVA and Duncan tests with p<0.05 as the limit of significance. Factors tested had no significant effect on each other. Primary teeth showed more nanoleakage than permanent teeth [P<0.05]. Mean nanoleakage was significantly higher in cervical than occlusal margins [P<0.05] and also in iBond than in Gluma One Bond in primary teeth [P<0.05]. In permanent teeth, the lowest nanoleakage was observed in Gluma One Bond. The result of this study indicates that the use of total etch dentin adhesives [Gluma One Bond] in bonded restorations results in less nanoleakage in primary and permanent teeth

[ effect of different surface treatments of stainless steel crown and different bonding agents on shear bond strength of direct composite resin veneer]

Stainless steel crown [SSC] is the most durable and reliable restoration for primary teeth with extensive caries but its metalic appearance has always been a matter of concern. With advances in restorative materials and metal bonding processes, composite veneer has enhanced esthetics of these crowns in clinic. The aim of this study was to evaluate the shear bond strength of SSC to composite resin using different surface treatments and adhesives. In this experimental study, 90 stainless steel crowns were selected. They were mounted in molds and divided into 3 groups of 30 each [S, E and F]. In group S [sandblast], buccal surfaces were sandblasted for 5 seconds. In group E [etch] acidic gel was applied for 5 minutes and in group F [fissure bur] surface roughness was created by fissure diamond bur. Each group was divided into 3 subgroups [SB, AB, P] based on different adhesives: Single Bond, All Bond2 and Panavia F. Composite was then bonded to specimens. Cases were incubated in 100% humidity at 37°C for 24 hours. Shear bond strength was measured by Zwick machine with crosshead speed of 0.5 mm/min. Data were analyzed by ANOVA test with p<0.05 as the limit of significance. There was no statistical interaction between surface treatment and adhesive type [P>0.05] so the two variables were studied separately. No significant difference was observed in mean shear bond strength of composite among the three kinds of adhesives [P>0.05]. Similar results were obtained regarding surface treatments [P>0.05]. Based on the results of this study, treating the SSC surface with bur and using single bond adhesive and composite can be used successfully to obtain esthetic results in pediatric restorative treatments

[ clinical and histological evaluation of human pulpal response after power bleaching]

"Power Bleaching" which is a new an in-office whitening technique with a combination of a whitening agent [peroxide] and an auxiliary [plasma-Arch light], has been claimed to be an effective and fast method in tooth bleaching. What is more important in using this method is the maintenance of the pulp health after tooth whitening. The aim of this study was to evaluate the human pulpal response after bleaching with H2o2 38% and plasma-Arc light. Eighty seven sound first premolars from 27 patients were selected and divided into 3 groups of 29, based on the time intervals of histologic evaluation. In each group 9 teeth were considered as a control. Vitality tests were done before bleaching [base line] and in four intervals of 2, 7, 30 and 60 days, but histologic evaluation was performed in three intervals 2, 7 and 60 days. Immediately after extraction, apical one third of the roots were sectioned off and each specimen was placed in 10% buffered formalin solution for pulpal fixation. EDTA was used for decalcification and sections were prepared from each specimen and stained with H and E and subsequently assessed microscopically for the following criteria: Irregularities in the odontoblastic layer, the presence of inflammatory cell, vasodilatation and pulpal fibrosis. Data was analyzed using Friedman test and Wilcoxon test [alpha= 0.05]. There were significant differences between the 2 and 60 days groups and between 7 and 60 days groups with respect to inflammatory responses and vasodilatation [p<0.05]. Comparison of the control and experimental groups of the 2 and 7 days revealed statistically significant differences in inflammation and vasodilatation [p<0.05]. No patient had experienced sensitivity, after different bleaching periods. Bleaching of teeth with H2o2 38% and plasma-Arc light might cause slight to moderate pulp reactions after 2 and 7 days confined to the coronal pulp. However, the observed histological changes did not affect the overall health of the pulp tissue permanently

Bacterial contamination of four commonly used dental materials

Bacterial contamination of dental materials and devices used in dental clinics and laboratories can lead to infectious diseases in patients, dentists and dental care providers. The aim of this study was to examine bacterial contamination of four dental materials. In this analytic-descriptive study, flour of pumice, zinc oxide powder, prophylaxis paste and wooden wedges of available commercial brands were tested. To assure an examiner-blind study, the samples were coded in the microbiology laboratory. In sterile conditions, the samples were inoculated in tryptycase soy broth and sodium tioglycolate for aerobic and anaerobic bacterial growth, respectively. The media was then incubated in 35 degrees centigrade and checked daily. Flour of pumice showed contamination to coagulase-negative Staphylococci, Enterococcus faecallis, bacillus and diphteroid. Some of the prophylaxis pastes were contaminated with micrococcus roseous, coagulase-negative staphylococci and diphteroid. One brand of wooden wedges demonstrated contamination to staphylococcus, diphteroid and bacilli. Zinc oxide powders were not contaminated. None of the samples showed contamination to anaerobic bacteria. Some of the investigated materials showed bacterial contamination, but the identified bacteria are not pathogen in normal situations

Analysis of protection effect of vitamins A, E against Gamma induced chromosomal abnormalities post and past-irradiation on mouse bone marrow cells usingmicronucleus assay

The radioprotectory effects of vitamins A and E post and past Gamma-irraiation on mouse bone marrow cells using micronucleus assay was analyzed. Micronucleus assay is a very fast and effective method in evaluating, structural as well as numerical chromosomal abnormalities. Search for find/ng an effective way of protection against harmful effects of induced or spontaneous irradiation is actively progressing. Effects of antioxidants such as vitamin A and E in in vivo have studied extensively. In this study effect of different doses of vitamin A and E post and past Gamma-irradiation of 2 Gy wererepresenting chromosomal damages. Of all doses used [0.6mg/kg, 1.2mg/kg and 2.4mg/kg for vitamin A and 50mg/kg, l00mg/kg and 200mg/kg for vitamin E/ l.Amg/kg, body weight of vitamin A and 200mg/kg body weight of vitamin E had the best effect on reducing induced-damages. Combination of two vitamins in these doses post and past irradiation revealed that vitamin E was the most effective post irradiation whereas vitamin A was the most effective past irradiation in reducing the frequency of micronucleus.According to our knowledge this is the first time that the anticlastogenic effect of vitamin A and E post and past irradiation in in vivo has been studied at the same time using micronucleus assay

Effect of different saliva decontamination procedures on bond strength to dentin in single bottle systems

Statement of Problem: Following the increasing use of composites in restoring anterior and posterior teeth, problems due to its technique sensitivity have become a major concern. One of these problems is the possibility of contamination of dentin with saliva, blood and/or gingival fluid in different stages of bonding procedure, even with application of different methods of isolation. However, by introduction of Single-bottle dentin adhesives, the contamination possibility reduced to two stages. Scientific documents show that saliva contamination reduces bond strength of composites to dentin. Application of simple and efficient methods for reducing or eliminating saliva contamination enables clinicians to carry out dental treatment without any concern about deterioration of clinical longevity of restoration. Purpose: This study was designed to compare the effect of different decontamination methods on the shear bond strength of composite to dentin using a "Single-bottle" adhesive

Materials and Methods: Seventy-two extracted sound human molars and premolars were selected. Enamel of buccal surface was ground flat to expose dentin. The teeth were divided into 9 groups of 8 each. In control group [1] the adhesive "Excite" was used according to the manufacturer, without any contamination. Conditioned and saliva contaminated dentin was [2] rinsed and blot dried, [3] rinsed, dried and re-etched. In groups 4, 5, 6 uncured adhesive was saliva contaminated and then: [4] only blot dried [5] rinsed, blot dried with adhesive reapplication and [6] resurfaced with bur, rinsed, dried and followed by repeating the whole process. In groups 7, 8, 9 cured adhesive was contaminated with saliva and then: [7] rinsed and dried [8] rinsed, blot dried with adhesive reapplication [9] same as group [6]. Then "Tetric Ceram" composite cylinders were bonded to dentin surfaces. Samples were thermo cycled in 5°C and 55°C water, 30 seconds in each bath with a dowel time of 10 seconds for 500 cycles. Finally, samples were sheared using Instron testing machine and shear bond strength data were subjected to one way ANOVA analysis, and Tukey HSD PostHoc. Mode of failure of samples was examined under Stereomicroscope [×40] and using Log-rank survival data analysis

Results: No statistically difference between mean shear bond strength of groups 1, 2, 3 was observed [P=0.543]. Comparison of groups 4, 5, 6 with group 1 showed that shear bond strength of group 4 was significantly lower [P<0.001]. Mean shear bond strength of groups 1, 7, 8, 9 were not significantly different [P=0.150]. The major mode of failure was cohesive either in composite or dentin bonding

Conclusion: Blot- drying of saliva-contaminated uncured Single-bottle adhesive significantly decreased shear bond strength of composite to dentin. In other contamination protocols, the effect of treatments applied did not differ