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Showing 6 results for Bleaching
Effect of two bleaching agents on enamel morphology: a SEM study
M. Ghavam , Z. Sadat Hashemi ,
Volume 18, Issue 1 (3-2005)
Abstract

Statement of Problem: Bleaching materials are able to change the surface morphology as well as mineral and organic content of tooth structure. Considering that bleaching is done for aesthetic purpose, awareness of the possible effect of these materials on hard tissue is important, because it may affect the restorative treatments.

Purpose: The aim of this study was comparing the effect of two bleaching materials, Kimia and Ultradent both containing 35% H2O2, on tooth enamel by SEM.

Materials and Methods: Five intact central incisors were cut into three sections vertically and each part was randomly divided into three groups. Group 1 (control), without any bleaching. Group 2, bleached with Kimia 35% H2O2. Group 3, bleached with Ultradent 35% H2O2. Each tooth served as its own control. Then the samples were observed by SEM with 250 and 500 magnifications.

Results: In the control group some scratches and small white grains were observed which seems to be the result of mastication trauma and pumice powder. In the other groups, morphologic changes like increased surface roughness, deepening of cracks, rod exposure and presence of new cracks were observed. The two experimental materials did not differ in these regards.

Conclusion: It seems that both studied materials have limited destructive effects on tooth enamel which seems to be of no clinical importance.


Evaluation of the effect of 16% carbamide peroxide gel (Nite White) on mercury release from Iranian and foreign spherical and admixed amalgams by cold vapor atomic absorption method
Sh. Kasraie , Mj. Assary , Hr. Abdosamadi , Kh. Mani Kashani , S. Arabzadeh ,
Volume 20, Issue 4 (1-2008)
Abstract

Background and Aim: Nowadays, esthetic dentistry has become an important part of modern dentistry. Bleaching is considered as a conservative, safe and effective way for treatment of discolored teeth. Although bleaching is commonly used on anterior teeth, the bleaching gel may come into contact with patient's former amalgam restorations and result in corrosive effects, dissolution of amalgam phases and increasing release of mercury. Mercury released from dental amalgam during mouthguard bleaching can be absorbed and increase the total mercury body burden. The aim of this study was to determine the amount of mercury released from Iranian and foreign brands of amalgams with spherical and admixed particles, polished and unpolished, after 16%carbamide peroxide gel application.

Materials and Methods: This experimental in vitro study was performed on 256 Iranian and foreign amalgam samples with spherical and admixed particles. The provided samples were put in distilled water and classified according to the type of amalgam, shape of particles and quality of surface polishing. The test samples were placed in Nite White 16% carbamid peroxide gel and control samples were put in phosphate buffer (Ph=6.5) for 14 and 28 hours. The amount of released mercury was calculated using AVA-440 Mercury Analysis System (Thermo Jarrell Ash model SH/229) with cold-vapor atomic absorption. Data were analyzed using t-test, four way and three way ANOVA tests with P<0.05 as the level of significance.

Results: 16% Nite White carbamide peroxide gel caused a significant increase in amount of mercury released from amalgams in all groups (P<0.05). Mercury release from Iranian amalgam was higher than that from the foreign brands (P<0.05). There was no significant difference in mercury released from spherical and admixed amalgams (P>0.05). The amount of mercury released from Iranian and foreign amalgams was time dependent (P<0.05). Furthermore, the amount of mercury released from unpolished amalgams was higher than polished ones (P<0.05).

Conclusion: The present study indicated that exposure of amalgam to 16% Nite White carbamide peroxide  gel causes a significant increase in mercury release from the amalgam which is significantly influenced by the brand, exposure time, and surface polishing.


Effect of bleaching on the microhardness of tooth-colored restorative materials
Abdolrahim Davari , Maryam Kashfi, Ebrahim Ataei, Danesh Kazemi Alireza ,
Volume 26, Issue 3 (8-2013)
Abstract

  Background and Aims: Bleaching agents not only affect the tooth structure, but also may alter the properties of restorative materials. The aim of this in vitro study was to evaluate the effect of different bleaching regimens on the microhardness of four tooth-colored restorative materials.

  Materials and Methods: Eighty specimens of four restorative materials (Microhybrid resin composite (Z250 (3M, ESPE), nanohybrid composite Z350 (3M, ESPE), packable composite P60 (3M, ESPE), and resin modified glass ionomer Vitremer (3M, ESPE)) were fabricated and were polished after 24 h with Soflex discs (3M,ESPE). Then the specimens were divided into two groups: In office bleach group, 40 specimens (10 of each restorative material) were bleached with hydrogen peroxide 37.5% for 30 min in two sessions with 7 days interval. In home bleaching group, 40 specimens were bleached with carbamid peroxide 22%, 6 h a day for 14 days. Vickers microhardness test were done before and after bleaching (baseline). Finally data were evaluated using analysis of Variance.

  Results: Two bleaching regimens were significantly decreased the microhardness values. In Z250 resin composite, the microhardness values before and after bleaching were 95.30 and 92.67 kg/mm2, respectively. for office bleaching (P=0.011) and 95.38 and 92.39 kg/mm2 for home bleaching (P<0.001). In Z350 resin composite, the microhardness values before and after bleaching were 98.29 and 92.41 kg/mm2, for office bleaching (P<0.001) and 97.35 and 93.44 kg/mm2 for home bleaching (P<0.001) respectively. In P60 resin composite, the microhardness values before and after bleaching were 103.10 and 96.16 kg/mm2, respectively. for office bleaching (P=0.045) and 102.61 and 98.16 kg/mm2 for home bleaching (P=0.001). In resin modified glass ionomer (Vitremer), the microhardness values before and after bleaching were 56.79 and 49.41 kg/mm2, respectively. for office bleaching (P=0.004) and 54.17 and 46.50 kg/mm2 for home bleaching (P<0.001). There was no significant difference between two bleaching agents (P=0.365).

  Conclusion: Dental bleaching agents decrease the microhardness of tooth-colored restorative materials.


The effects of two types of bleaching agents on color and translucency changes of three types of composite with or without surface rebounding
Abdolrahim Davari, Alireza Daneshkazemi, Mahsan Sheshmani, Haleh Karami, Elham Motallebi,
Volume 32, Issue 3 (11-2019)
Abstract
Background and Aims: The bleaching agents can lead to color and translucency changes in composite resins. Due to the increasing use of the nano composites and the silorane-based composites, this study aimed at examining the color and translucency changes of these restorations after bleaching agents.
Materials and Methods: In this experimental - laboratory study, 198 composite discs were divided into three groups of 66 specimens using three types of composite: the microhybrid composite Z250, the nanohybrid composite Z350 and the silorane-based composite P90. After acid etching, half of the specimens in each group were covered by a resin rebounding agent. Then, the color and translucency assessment was done by reflectance spectrophotometer, using CIE LAB system. Each group was divided into three subgroups of bleaching agents: the 40% hydrogen peroxide and 20% carbamide peroxide bleaching agents and the control group. After applying bleaching agents, the final color and translucency changes were assessed. Data were analyzed using Mann Whitney and Kruskal Wallis tests.
Results: The effect of composite and bleaching agent type and bonding agent were significant (P<0.001). The color changes in the microhybrid composite were higher than nanohybrid and silorane-based composites (P<0.001) (∆E>3.3). Also, the color changes by 20% carbamide peroxide were higher than that of hydrogen peroxide and control groups (P<0.001). The results of translucency changes were generally consistent with color-change measurements (∆E>3.3).
Conclusion: According to the present study, the most color changes appeared in the microhybrid composite and by 20% carbamide peroxide bleaching agent. Rebound samples were generally less affected by bleaching agents. The least color and translucency changes were related to nanohybrid composites.

Effects of bleaching on color stability of enamel lesions treated with resin infiltrant
Mansoureh Emami Arjomand, Seyde Sahar Masoumi, Haleh Heshmat, Zahra Nouralizadeh,
Volume 35, Issue 0 (5-2022)
Abstract
Background and Aims: Considering the preventive and therapeutic effects of resin infiltration (RI) and the unknown effect of bleaching on the enamel treated with this method, this in-vitro study aimed to assess the effect of bleaching on color stability of enamel lesions treated with RI.
Materials and Methods: In this in-vitro, experimental study, enamel-dentin samples measuring 5×5×3 mm were prepared on the buccal and lingual surfaces of 30 extracted humans third molars with no caries, cracks or enamel defects by a microtome. The specimens were divided into three groups of 10 specimens: 1) sound enamel (control), 2) demineralized enamel, 3) demineralized enamel plus RI. White spot lesions were artificially created by immersing the samples in hydroxyethyl cellulose demineralizing gel with a pH of 4.5 for 4 days. Next, Icon RI was applied on the samples in group 3. The baseline color of the specimens was measured using a spectrophotometer. Then, 35% hydrogen peroxide was applied on the specimens in three cycles and time interval of 10 min. After the end of the last cycle, the samples were completely washed for 1 min and then, underwent colorimetry again. Data were analyzed using one-way ANOVA.
Results: The results of this study showed that the highest level of color change (ΔE) in the demineralized group was 6.3±2.003, while the least amount of ΔE in the enamel lesion group treated with resin infiltration was 3.54±0.98 and in the control group ΔE was 4.13±1.14. Therefore, there was a significant difference between demineralized and treated by infiltratant groups (P=0.005). However, there was no significant difference between control group and treated with resin infiltration group (P=0.54).
Conclusion: Bleaching induced a less change in the color of the enamel lesions treated by resin infiltration compared with that of the demineralized teeth.
 
 

Effect of three whitening mouthrinses with different formulations on whitening of tooth enamel
Fereshteh Naser Alavi, Ashkan Salari, Seyedeh-Maryam Tavangar, Reza Tayefeh Davalloo, Farideh Darabi, Zahra Farzi,
Volume 36, Issue 0 (5-2023)
Abstract
Background and Aims: The white color of teeth is one of the most essential factors in smile esthetics. Therefore, various whitening agents such as bleaching mouthwashes have been produced in response to the people’s high demand for having whiter teeth. The present study evaluated the efficacy of three whitening mouthwash products on tooth enamel whiteness.
Materials and Methods: In the present in vitro study, 32 bovine incisors were assigned to four groups in terms of the mouthwash used (n=8): control (C); Xenon Smart White (ZSW), containing pyrophosphate and triphosphate; Signal White Now (SWN), containing Blue Covarine; and Pasta Del Capitano whitening mouthrinse (PCW), containing Plasdone. Colorimetry was carried out using a spectrophotometer at the baseline and 2, 4, 8, and 12 weeks after treatment with mouthwashes. Data were analyzed using CIELab parameters with ANOVA, RM two-way ANOVA, and post hoc Tukey tests (α=0.05).
Results: The results showed that the whiteness created by the SWN mouthwash was clinically visible (ΔE>3.3). However, the functions of all the mouthwashes were statistically similar with no significant differences from the control group (P>0.05).
Conclusion: Although, Blue Covarine-containing mouthwash was somewhat effective in whitening of tooth enamel, none of the mouthwashes had significant efficacy compared to distilled water.

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