[Effects of mouthwashes on color stubitity of hleached teeth]

Background and Aim: Bleached teeth are susceptible to discoloration. The aim of this study was to evaluate discoloration of bleached teeth following short-term use of several mouthwashes.

Materials and Methods: In this In-vitro experimental study, 48 extracted maxillary central incisorswere selected and divided into four groups of 12. All the teeth were subjected to external bleaching with 38% hydrogen peroxide [H2o2]. After bleaching, the teeth were immersed in in distilled water [control group or group 1], chlorhexidine [CIx; group 2], Irsha [group 3] or Persica [group 4] for three, seven and 14 days. The color change was assessed by a spectrophotometer at each time point and reported as INCREMENT El, INCREMENT E2 and INCREMENT E3. The results were analyzed by paired t-test, repeated measures ANOVA, one-way ANOVA and LSD test.

Results: Different mouthwashes [p:0.0a3] and immersion times [p:0.03g] caused significantly variable color change in bleached teeth. After 14 days of immersion, the color change of samples in Persica group had significant differences with that of other goups [p<0.000]. The results of repeated measures ANOVA was only significant for the persica group indicating significant color change over time. Thus, paired t-test was applied for pairwise comparison of the time points, which revealed significant differences between INCREMENT EI and INCREMENT E3 and also INCREMENT E2 and INCREMENT E3 [p<0.0S].

Conclasion: Persica mouthwash would cause significant discoloration in recently bleached teeth.

[Effect of translucency and opacity of fiber reinforced posts on fracture resistance of compromised teeth]

Severely damaged teeth with no support at the coronal portion of root canal are very difficult to restore. The aim of this invitro study was to evaluate intraradicular reinforcement by dual cure composite resin and two different types of fiber reinforced composite [FRC] posts [translucent and opaque] in structurally compromised roots. Root canal therapy was performed for 48 maxillary central incisors. The teeth were divided into four groups, and specimens from three groups were prepared to simulate the teeth with flared canals. In the 1[st] group, no weakening was done. In the 2[nd] group, the compromised area of the root canal was filled with gutta percha. In the 3[rd] and 4[th] groups, universal DT light and DT white posts were used respectively in the root canal to 8 mm below the margin of the palatal wall. The posts were cemented with dual-cure composite. In all groups, the access cavity was restored with light-cure compo-site resin. After being mounted, all specimens were pressed at an angle of 45? relative to the long axis of the teeth. The amount of force at fracture was recorded. Results of fracture load were evaluated by one-way ANOVA and LSD post hoc test and the results of mode of fracture were evaluated by chisquare test. The mean fracture load for the four groups was 170.12, 71.40, 125.8 and 148.59 kgf, respectively. There was a significant difference between the mean fracture load of 1[st] and 2[nd] groups and that of other groups [P=0.001]. The mean fracture load of the 4[th] group was significantly [P=0.002] higher than that of the 3[rd] group. The frequency of restorable fractures was significantly different between these two groups [P<0.001]. Using dual cure composite resin and FRC posts in roots with thin walls will reinforce the compromised teeth but the type of post will affect the outcome

[Changes in bleached enamel microhardness after application of fluoride and CPP-ACP]

Tooth bleaching decreases enamel microhardness. The aim of this study was to evaluate the changes in microhardness of bleached enamel after applying fluoride and CPP-ACP [casein phosphopeptide amorphous calcium phosphate]. In this experimental study, sixty extracted human molars were divided into six groups [ten each]. The flatted occlusal surface was covered with nail varnish. In the second, third and fourth groups, tooth bleaching was performed. The first and second groups were positive and negative control groups. In the third and fifth groups, the specimens were covered with sodium fluoride varnish and the fourth and sixth groups underwent CPP-ACP therapy. Subsurface enamel microhardness was determined on the occlusal surface with 300 micron distance from the buccal or lingual surface. One way ANOVA and Tukey post hoc were used for statistical analysis. Microhardness of bleached enamel was significantly lower than the other groups. The teeth treated by fluoride agent or CPP-ACP after bleaching had a significant increase in their microhardness in contrast with the bleached enamel. CPP-ACP and fluoride treatment had no significant effect on sound enamel microhardness. Although using CPP-ACP and fluoride increases the enamel microhardness, there was no significant differences between them. Fluoride and CPP-ACP components increase bleached enamel microhardness

[Effect of cavity liners on micro leakage of Cl V amalgam restorations]

There is no bonding between amalgams and restored cavity walls. Therefore, these restorations are prone to leakage despite the deposition of corrosion products. The aim of this in vitro study was to evaluate the effectiveness of three cavity liners in reducing micro leakage of class V amalgam restorations. Sixty-eight extracted intact human molar teeth were selected. Class V cavity preparations were performed in all teeth and they were randomly divided into four groups. Group one was used as a control group [no liner], and the rest were Varnish, Resin Cement [Panavia F], and Light-cured dentin bonding agent [Single Bond] groups. Or alloy amalgam was condensed into the prepared Cl V cavities. All teeth were immersed in distilled water at 37°C, for 24 hours. All restorations were subjected to 1000 thermal cycles at 5-55 degrees centigrade. For micro leakage test, all teeth were immersed in 0.5% Basic Fuchsine and sectioned. Dye penetrations were evaluated by stereomicroscope. The collected data were analyzed statistically by Kruskal-Wallis and Bonferroni test. The results showed significant differences between four groups [P< 0.05]. Control group showed the maximum and Panavia group revealed the minimum micro leakage. There was no significant difference between Panavia and Single Bond groups. On the other hand, no significant difference [P>0.008] was observed between occlusal and gingival margins in the control, Single Bond and Panavia groups. Although, the difference was statistically significant in varnish group [P=0.002]. When compared with control group, the dentin bonding agent, varnish and cement resin groups demonstrated significantly decreased micro leakage at the enamel margin [P=0.0001]. However, when compared with varnish and control group, the dentin bonding agent and cement resin groups demonstrated significantly decreased micro leakage at the cementum margin [P<0.008]. Findings of this investigation clearly demonstrate the advantage of using lining materials in amalgam restorations. Therefore, we can conclude that such materials may significantly increase the sealing ability and decrease the micro leakage in Class V amalgam restorations

[Effect of used diamond burs on dentin bond strength]

Many researchers have reported that, constant use of diamond burs can reduce their cutting efficacy during cavity preparation. The aim of this study was to evaluate the effect of changes in diamond bur sharpness on dentin bond strength when using self-etch bonding system. A total of seventy-two caries-free human 3[rd] molars were included in this in-vitro investigation. The teeth were sectioned in occlusal surface in order to expose dentin, and then were randomly divided into four groups. For dentin preparation, a fine diamond bur was used in group 1, a new coarse diamond bur was used in group 2, a used coarse diamond bur was used in group 3 after applying on porcelain for two minutes, and a used coarse diamond bur was used in group 4 after it was applied on porcelain for ten minutes. Unique composite capsules were bonded to all dentin surfaces using Clearfil SE Bond and then cured. After storage for 24 hours in 37°C distilled water, the bonded teeth were subjected to shear testing by using Instron testing machine. The bond strengths were calculated and recorded as failure. Bond strength data were analyzed by One-Way ANOVA and Tukey tests. The mean [Standard Deviation] of shear bond strength in each group can be reported as follows: 22.2Mpa[3.38] for group one, 18.05Mpa[4.54] for group two, 24.5Mpa[5.69] for group three and the figure was 22.4Mpa[4.52] for group four. The statistical analysis demonstrated that Shear bond strength of new coarse diamond bur preparations were significantly [P<0.001] less than fine or used diamond burs. Used diamond burs of different durations can affect dentin bond strength of SE Bond self etch bonding system. Accurate type of bur and adhesive selection are essential in optimizing dentin adhesion to self-etching adhesives

influence of Iranian temporary components on shear bond strength of composite resin to deep dentin in a single bottle bonding system

There are controversies about the effect of eugenol containing cements on composite-dentin bond strength. This study was designed to evaluate the effect of eugenol containing temporary cements on shear bond strength of composite bonds to deep dentin when using Single Bond. In this in-vitro study, ninety extracted human third molars were sectioned horizontally at deep dentin and randomly divided in six groups after embedded into self cure acrylic material. Samples in five groups were covered with: Cavisol, Temband, and Zoliran with three different powder/liquid ratios of 10/2 gr., 10/3 gr., and 10/2 gr. respectively. The samples in group six were used as control and therefore they received no treatment. After elapse of one week, the temporary cements were removed mechanically from all samples in the first five groups. Only the samples in group five were cleaned by ethanol. All groups were pretreated with single bond and then composite cylinders were added. Debonding and shear bond strength was tested by using DARTEC universal testing machine. These data were analyzed using One-Way ANOVA and Duncan tests. The median shear bond strength were calculated for all six groups as follows: The values were 17.96 [ +/- 0.73], 15.06 [ +/- 0.78], 16.14 [ +/- 0.75], 13.76 [ +/- 0.66], 16.79 [ +/- 0.34], 18.12 [ +/- 36] Mega Paschal respectively. Significant group differences were found for all groups [P<0.001] except for first and sixth [P >0.05] as well as third and fifth groups. Temporary cements containing eugenol significantly reduced the shear bond strength of composite to deep dentin when using Single Bond