25 research outputs found
The effect of office bleaching on the color and bond strength of resin restorations
No full textBackground: Bleaching may affect the bond strength of existing composite fillings and may weaken it. Hence, the aim of this study was to find the best method of in-office bleaching with the least effect on microshear bond strength (MSBS) of existing composite resin fillings to tooth structure.
Materials and Methods: In this in vitro study, Class V cavities were prepared on buccal surface of 50 extracted third human sound molars. The cavities in 25 teeth had enamel axial walls, Group E, which were divided into five subgroups of E1 through E5 and in 25 teeth had dentin axial walls, Group D, which were divided into five subgroups of D1 through D5. Cavities were treated with Single Bond 2 adhesive system and restored with composite resin (Z250). The corresponding subgroups received similar bleaching methods and materials; 1 – not bleached, 2 – hydrogen peroxide (HP) 25%, 3 – HP + ultraviolet light, 4 – HP + light-emitting diode-curing device, and 5 – HP + diode laser. Teeth colors were monitored before and after bleaching, and MSBS test and failure modes were examined. Results were analyzed with one-way ANOVA and Kruskal–Wallis tests. P < 0.05 was considered significant.
Results: One-way ANOVA did not show differences in MSBS of enamel subgroups but showed significant differences in dentin subgroups (P < 0.00). Adhesive fracture in all of the subgroups was the most frequent mode of failure. Kruskal–Wallis test showed that laser was the most effective instrument to change ΔE.
Conclusion: Diode laser was the best method for tooth bleaching because lowering the shear bond strength between composite resin and enamel was minimum and also had the most ΔE in tooth bleaching
Effect of fluoride-free and fluoridated carbamide peroxide gels on the hardness and surface roughness of aesthetic restorative materials
No full textBackground: Bleaching products may show some side effects on soft and hard tissues and restorative materials in the oral cavity. This study evaluated the effect of carbamide peroxide gel with and without fluoride ions on the microhardness and surface roughness of tooth-colored restorative materials.
Materials and Methods: In this in-vitro study, 76 cubic specimens (4 mm 3 × 4 mm 3 × 3 mm 3 ) were fabricated from 4 aesthetic A3-shade restorative materials. These materials consisted of two composite resins and two glass ionomers. The specimens made from each material were treated with the following surface treatments: 1. Control group: The specimens were not bleached and were stored in normal saline. Group 2. Fluoridated 20% carbamide peroxide gel, treated 3 h a day for 4 weeks. Group 3. Treated 1 h a day with fluoride-less 22% carbamide peroxide for two weeks. From each group, three other specimens were selected to be evaluated in terms of changes in surface roughness, under scanning electron microscopy (SEM).
Results: In this study, fluoridated 20% carbamide peroxide gel increased the microhardness of the four aesthetic restorative materials. The fluoride-free carbamide peroxide 22% reduced the microhardness of the four used materials, which this change was significant for Vitremer and Amelogen. SEM analyses showed changes in surface roughness of glass ionomer specimens.
Conclusion: The effect of bleaching on the microhardness of restorative materials is material dependent. Before the application of bleaching systems on the glass ionomer materials, the application of a protective barrier should be considered
Effect of different surface treatments on microtensile bond strength of two resin cements to aged simulated composite core materials
No full textObjective: Roughening of the aged composite resin core (CRC) surface seems essential for durable adhesion. The aim of this study was to investigate the influence of various surface treatments and different resin cements on microtensile bond strength (µ TBS) between two aged core build-up composites (CBCs) and feldspathic ceramic.
Materials and Methods: A total of 16 composite blocks made of two CBCs, Core.it and Build-it were randomly assigned to four surface treatment groups after water storage and thermocycling (2 weeks and 500 cycles). Experimental groups included surface roughening with air abrasion (AA), hydrofluoric acid, pumice, and laser and then were bonded to computer-aided design/computer-aided manufacturing feldspathic ceramic blocks using two resin cements, Panavia F2 (PF), and Duo-link (DL). The µ TBS was tested, and the fracture mode was assessed. The data were analyzed with multiple analysis of variance to estimate the contribution of different surface treatments, resin cements, and two aged CRCs on µ TBS. Statistical significance level was set at α < 0.05.
Results: Surface treatment and cement type significantly affected bond strength (P < 0.001) but the type of CRC did not (P = 0.468). Between roughening methods, the highest and the lowest values of µ TBS were sequentially obtained in AA and Er.YAG laser groups. The highest bond strength was in AA group cemented with PF (31.83 MPa). The most common failure mode was cohesive fracture in the cement.
Conclusion: Different surface treatments had different effects on µ TBS of aged CRCs to feldspathic ceramics. PF was significantly better than DL
Effect of concentration of hydrofluoric acid and etching time on microtensile bond strength of Zirconia-reinforced lithium silicate ceramics
No full textIntroduction: Etching the internal surface of ceramic restorations with hydrofluoric (HF) acid and silane is a well-accepted technique to enhance the bond strength. The aim of this study was to assess the effect of concentration of hydrofluoric acid and etching time on microtensile bond strength (µTBS) of zirconia-reinforced lithium silicate (ZLS) ceramics in 2021.
Materials & Methods: This in vitro study was conducted on 8 Celtra-Duo ceramic blocks size 14 measuring 12×14×18 mm. Each ceramic block was divided into three equal pieces by a cutting machine to obtain a total of 24 specimens. The specimens were randomly divided into 6 groups for etching with 5% and 10% HF acid for 30, 60, and120 seconds. Silane (Clearfil porcelain activator) and bonding agent (Clearfil SE Bond) were applied to the etched specimens. Panavia F2 resin cement was applied on the surfaces and light-cured. The mTBS of resin cement to porcelain was measured by a universal testing machine. The mode of failure was determined under a stereomicroscope at x40 magnification. Data were analyzed by one- and two-way ANOVA (P<0.05).
Results: The mean mTBS of Celtra-Duo ceramics subjected to etching for 30, 60, and 120 seconds was not significantly different in the use of 5% and 10% HF acid concentrations (P>0.05). Two-way ANOVA showed that the effects of HF acid concentration and etching time, and their interaction effect were not significant on µTBS of CAD/CAM Celtra-Duo ceramics (P>0.05). The mode of failure was dominantly adhesive in both concentrations of 5% and 10% HF acid. No mixed failure occurred in both concentrations.
Conclusion: Considering the non-significant difference in µTBS of ceramics subjected to different concentrations of HF acid for different times, the application of HF acid with lower concentration for a shorter period is recommended to prevent possible adverse effects on ceramic strength
Effect of hydrofluoric acid surface treatments on micro-shear bond strength of CAD/CAM ceramics
No full textEffect of hydrofluoric acid surface treatments on micro-shear bond strength of CAD/CAM ceramics
No full textIntroduction: Dental ceramics are appreciated as highly esthetic restorative materials that can simulate the
appearance of natural dentition better than other materials. The aim of this study was to evaluate the effect of
hydrofluoric acid concentration and etching time on micro-shear bond strength (µSBS) to IPS e.max CAD and
Vita Mark II of a dual cured resin cement (Panavia F2.0).
Methods: This study was an experimental in vitro study, performed in the dental material research center of
Babol University of Medical Sciences in 2016. Two hydrofluoric acid concentrations (5% and 10%) and three
different etching times (20, 60 and 120 seconds) were used to etch the specimens respectively. A silane coupling
agent (Clearfil porcelain activator) and priming and bonding agent (Clearfil SE bond) were used on the etched
surfaces in accordance to the manufacturer’s instructions of use. Then resin cement was applied on the prepared
ceramic surfaces and light cured. µSBS between resin cement and the porcelains were measured with a universal
testing machine. Mode of failure was observed with 40x magnification by means of a Stereo microscope. Data
were analyzed with ANOVA and independent-samples t-test and Chi-square tests.
Results: In both e.max and Vita Mark II groups, µSBS were not significantly different when different etching
times (one-way ANOVA) and HF acid concentrations (Independent-samples t-test) were used (p>0.05), but the
highest µSBS was shown in e.max specimens etched 60 s with 5% HF and Vita Mark II specimens etched 20 s
with 10% HF. µSBS of e.max was significantly higher than Vita Mark II (p=0.00).
Conclusion: Best surface treatment for e.max and Vita Mark II ceramics is 20 s etch using 5 % hydrofluoric acid
Effect of different surface treatments on microtensile bond strength of two types of composite substructures with ceramic by resin cements
No full textIntroduction: The aim of this study was to investigate the effect of different surface treatments on the microtensile bond strength (µTBS) of two types of composite substructures with Vita Mark II ceramics by resin cement.
Materials & Methods: Sixty-four substructure specimens were molded from two dual-cure composites Core.it and Build-it, equally, and cured by LED light. The specimens of each group were randomly divided into 4 subgroups (n=8) treated by one of HF acid 10%, air abrasion, Er: YAG laser, and one group without any treatment (control group), and then the specimens of each group were bonded to Vita Mark II CAD/CAM ceramic blocks using two Duo-Link and Panavia F 2.0 resin (n=4 and 20 slice in any group). Each final specimen was thermocycled between 5 °C and 55 °C for 2500 cycles and then cut by a slow speed saw to obtain 5 sticks with cross-section dimensions of about 1×1 mm². The µTBS test was done at a speed of 0.5 mm/min by Universal Testing Machine. The fracture pattern was then determined using a stereomicroscope. Statistical differences between groups were determined by one-way ANOVA using Tukey's multiple comparison tests.
Results: Among all 16 groups, the highest µTBS was observed in the group with Core.it substructure composite and Duo-link resin cement without any surface treatment and after that in the second step in build-it substructure composite group and Panavia resin cement without surface treatment. The most common fracture pattern in all groups was cohesive in resin cement (P value<0.05).
Conclusion: According to this study, composite substructure surface treatment by hydrofloridric acid, laser and air abrasion reduced µTBS between substructure- ceramic and so is not recommended
Effect of hydrofluoric acid concentration and etching time on the surface roughness of CAD/CAM ceramics
No full textIntroduction: Dental ceramics are considered as materials that can restore the appearance of natural teeth. Etching the inner surface of a ceramic restoration with hydrofluoric acid (HF) followed by using a silane coupling agent is a well-known and recommended method to increase the bond strength. The aim of etching on ceramic structure is to enhance the surface roughness (Ra) and energy and to cleanse the bonding area. The aim of this study was to evaluate the effect of different HF concentrations and etching times on the Ra of IPS e.max CADTM and Vita mark IITM.
Material & Methods: Two HF concentrations (5% and 10%) and three etching times (20, 60 and 120 seconds) were evaluated. Etched patterns were observed by scanning electron microscopy (SEM) and Ra was measured using atomic force microscopy (AFM). Surface element analysis was performed using energy dispersive X-ray spectroscopy (EDAX). Data were analyzed on SPSS 20 using ANOVA and T-test.
Results: The Ra had no significant difference among various Vita mark IITM specimens (P=0.973). Among IPS e.maxTM specimens etched with 5% HF, the AFM results showed that 20-s etching time had the lowest Ra and among those etched with 10% HF and 120-s etching time had the most Ra. In IPS e.maxTM specimens etched with acid for 20 s, a significant difference was observed in Ra of 5% and 10% acid concentrations (5% HF lower than 10% HF) (p=0.012).
Conclusion: Among IPS e.maxTM specimens etched with 5% and 10% HF, increasing the etching time lead to higher Ra. For both IPS e.maxTM and Vita mark IITM, 20-s etching with 5% HF provides acceptable Ra for the bond
Effect of Glass Ionomer Filler Size on Fluoride Release, Antiplaque Properties, and Abrasive Effects of Toothpaste
No full textABSTRACT Objectives This study aimed to assess the impact of incorporating glass ionomer fillers of varying sizes on fluoride release, antiplaque properties, and the abrasive effects of toothpaste. Materials and Methods In this laboratory study, three toothpaste samples containing glass ionomer filler particles (0.5, 5 µm, and a hybrid combination of equal proportions of both fillers) were tested, along with a base toothpaste without fillers or fluoride and a commercial toothpaste (Colgate Total) as controls. Fluoride release was measured using a fluoride ion‐selective electrode. Antiplaque properties were assessed by evaluating the effect of toothpaste on cultured saliva in tissue culture plates, with optical density measured using an ELISA reader. Abrasive effects were analyzed by changes in enamel thickness of bovine teeth using a three‐body wear test. Data were analyzed with ANOVA and Tukey's tests in SPSS software at a 0.05 significance level. Results Toothpaste containing 0.5 µm fillers showed the highest fluoride release, whereas the lowest release was associated with 5 µm fillers. All formulations demonstrated antiplaque activity, though differences among filler‐containing toothpastes were not statistically significant (p > 0.05). Enamel abrasion differed significantly among the samples (p < 0.001), with the greatest abrasion observed for toothpaste containing 5 µm fillers and the least abrasion observed for 0.5 µm fillers. Conclusions Incorporating glass ionomer fillers into toothpaste formulations provides fluoride release and antiplaque effects comparable to those of commercial toothpaste. Smaller filler sizes enhance fluoride release and reduce abrasiveness, though filler size does not significantly influence antiplaque efficacy
Man-machine interface prptotype for realtime prediction of motion of exoskeleton's users
No full textLAUREA MAGISTRALEIn the United States, over 282.000 people today are affected by Spinal Cord Injury, which is a traumatic damage to the spinal cord that leads to a partial or total body paralysis. At the UC Berkeley Human Robotics & Engineering Laboratory has been developed the Phoenix Exoskeleton which aims to reduce the impediments due to this physical damage by replacing the wheelchair in order to give to the patients the opportunity of changing their quality life, by improving overall health and mobility. This work introduces an innovative approach for replacing the current user interface, allowing to the user to have an interaction with the device totally free of active inputs, while walking, through a safe system which predicts in real time the users intentions. The software prototype is designed for providing an MMI (Man-Machine Interface) able to reduce the time gap and the balance variation between the moment when the intention of walking presents itself and the trigger of the swing really happens, according to the empiric hypothesis formulated by the author which assumes that exoskeletons users have involuntary body movements which differentiate their motion desires. The system has been developed using a machine learning model fed with post- processed data collected by two encoders and one IMU, which describe the users gait. It has been called Body Motion Triggering.
The efficiency of the prototype has been tested in laboratory by the pilot: the system turned out to be totally safe; the predicting outcomes still need to be widely improved but the achieved results are encouraging and have demonstrated the validity of the formulated hypothesis, opening a new potential field of research.
The hope behind the analysis carried out is to have been useful in order to improve the lives of people that need it
