Effect of Different Protective Bases on pH Changes and Hydrogen Peroxide Microleakage During Intracoronal Bleaching.

Objectives: This study aimed to evaluate the pH changes and penetration of hydrogen peroxide into radicular dentin when different protective bases were used with and without a bonding agent. Materials and Methods: In this in-vitro experimental study, 70 single-rooted bovine teeth were instrumented and obturated with gutta-percha. The gutta-percha was removed 3mm below the cementoenamel junction (CEJ) and the teeth were divided into seven groups (n=10). In each group, 2mm base (1mm apical to the CEJ) was applied as follows: TheraCal LC, TheraCal LC plus SE Bond, Lime-Lite, Lime-Lite plus SE Bond, Ionoseal, Ionoseal plus SE Bond, and resin-modified glass ionomer (RMGI). The teeth were placed in vials containing distilled water, and pH values and molar concentration of the medium surrounding the teeth were recorded immediately after internal bleaching with 35% hydrogen peroxide. The pH values were also recorded at 1, 7, and 14 days following renewal of the medium. Data were analyzed with t-test, one-way ANOVA, and Kruskal-Wallis test. Results: After bleaching, the medium pH became acidic in all groups. There were no significant differences among groups in the mean pH of the medium after bleaching (P=0.189). Moreover, there were no significant differences among the study groups with respect to hydrogen peroxide concentration (P=0.895). Conclusion: Intra-orifice barriers such as light-cure resin-modified calcium hydroxide, light-cure resin-reinforced glass ionomer, and light-cure calcium silicate can be as effective as RMGI in providing coronal seal during intracoronal bleaching.

The effect of intraorifice barriers (TheraCal LC, Lime-Lite and Ionoseal) on the fracture resistance and failure patterns of endodontically treated teeth submitted to intracoronal bleaching.

Background: The aim of the study was to compare the root reinforcement potential of different light cured intraorifice barriers (TheraCal, lime-lite, Ionoseal and resin-modified glass-ionomer [RMGI] [Fuji II LC]) with or without bonding agent placed in the orifice of endodontically treated and bleached teeth. Materials and Methods: In this experimental in vitro study, single-rooted bovine teeth were instrumented and obturated with gutta-percha. Except the control group, in other specimens, gutta-percha was removed 3 mm under cementoenamel junction. Then, the specimens were divided into seven groups according to the bases was applied: TheraCal LC, TheraCal LC with bonding agent, Lime-Lite, Lime-Lite with bonding agent, Ionoseal, Ionoseal with bonding agent, and RMGI (Fuji II LC). After internal bleaching, the teeth were decoronated. Then, all the groups were subjected to fracture resistance testing using Universal Testing Machine. For evaluating fracture resistance, analysis of variance and Tukey's test were used and for comparing the mode of fracture fisher test was applied in SPSS software. The significance was determined at (α = 0.05) confidence interval. Results: The group of TheraCal LC with bonding agent showed better fracture resistance as compared to the control group (P = 0.004). Although there was no statistically significant difference in the pairwise comparison between the other groups. Conclusion: TheraCal LC with bonding agent can be used as intraorifice barriers with good fracture resistance in endodontically treated and bleached teeth.

Effect of different cleansing methods on the artificially aged bond strength of resin to contaminated zirconia: A systematic review.

PURPOSE: The aim of this review was to evaluate studies investigating the effect of cleansing methods on the artificially aged bond strength of resin to contaminated zirconia restorations and determine which cleansing method of contaminated zirconia for resin bonding improvement is more efficient. METHODS: An electronic search of published studies in English language was carried out until July 2021 on Scopus, Web of Science, and Medline databases. Data from in vitro studies involving the evaluation of the artificially aged bond strength of resin to contaminated zirconia following different cleansing methods were included. In vitro studies in which samples were not subjected to at least 5000 thermocycles, were excluded. RESULTS: Of 162 articles retrieved initially, 19 were eligible to be included in the systematic review, of which 5 articles were excluded. Therefore, the final sample was 14 in vitro studies. All of the included studies for air abrasion suggested this method as an effective cleansing method, but 6 of 8 included studies reported cleaning paste (Ivoclean) as an effective cleansing method. All of the included studies for NaOCl and a cleaning gel (AD Gel) reported their efficacy. Finally, the results of included studies showed the ineffectiveness of phosphoric acid, water, isopropanol, enzymatic detergents, hydrogen peroxide, and acetone. CONCLUSIONS: Air abrasion has been reported as an effective cleansing method to improve the bond strength of resin to contaminated zirconia. To improve the effectiveness of cleaning paste in resin bonding, another efficient cleansing method should be followed after this method. However, the superior cleaning potential of air abrasion rather than cleaning paste has been reported. Sodium hypochlorite and cleaning gel seem to be as effective as air abrasion, but extensive water-rinsing is necessary after the application of these cleaning agents.

Comparison of antibacterial activity and fluoride release in tooth-colored restorative materials: Resin-modified glass ionomer, zirconomer, giomer, and cention N.

Background: Considering the important role of fluoride in preventing caries by reducing the number and activity of cariogenic bacteria and introducing new fluoride-releasing tooth-colored restorative materials, this study was performed to compare and evaluate fluoride ion release and antibacterial activity of resin-modified GI, zirconomer, giomer (Beautifil), and Cention N. Materials and Methods: In this experimental in vitro study, eighty samples (20 samples in each group) were prepared, 10 samples for fluoride testing and 10 samples for antibacterial activity. To evaluate the release of fluoride (PPM), fluoride ion-selective electrode was used on days 1st, 3rd, 7th, 14th, and 21st; and antibacterial activities against Streptococcus mutans were examined using direct contact test by absorption of light hourly once every 5 h and days 1st, 2nd, and 7th using an ELISA reader with a microplate reader of 800 TS at a wavelength of 630 nm. The results were analyzed using one-way ANOVA, Tamhane post hoc test, and paired t-test in SPSS software (IBM, Somers, NJ, USA) at a significant level of (P < 0.05). Results: The release of fluoride from materials showed a statistically significant difference (P < 0.001). The maximum mean of fluoride released during the 1st, 3rd and 7th days belonged to the zirconomer group and the minimum for the giomer group. During the measurement period of light absorption from 0 to 24 h after planting, light absorption of foursubstances together was found to be statistically significant (P <.001). Zirconomer light absorption increased on the 7th day, unlike other substances, but still, the minimum light absorption was related to zirconomer. Conclusion: The highest fluoride release was in zirconomer, Cention N, fuji II LC, and giomer, sequentially. Zirconomer showed maximum and giomer showed minimum antibacterial activities.

Evaluation of microleakage in Class II composite restorations: Bonded-base and bulk-fill techniques.

BACKGROUND: This study compared microleakage of Class II cavities restored using bonded-base and bulk-fill techniques with different bases. MATERIALS AND METHODS: In this in vitro study, in 60 extracted human molars, standardized (4 mm × 2 mm × 8 mm) Class II cavities were prepared, such that the gingival floor was located 1 mm below the CEJ. The teeth were randomly divided into five groups and filled with: (1) Fuji II LC + x-tra fil, (2) Ionoseal + x-tra fil, (3) x-tra base + x-tra fil, (4) Grandio Flow + x-tra fil, and (5) x-tra fil only [control group]; in open-sandwich technique, the base thickness was 1 mm. The bases were coated all gingival floor. Except for the first group, where dentin conditioner was used, the Clearfil SE bond was applied before application of the bases and restorative materials as a bonding agent. After 500 thermocycles between 5°C and 55°C, the specimens were immersed in 0.5% basic fuchsine solution for 24 h. The restored teeth were sectioned, and the dye penetration in gingival floor was observed by a stereomicroscope at ×32. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests in SPSS software. The significance was determined at 0.05 confidence interval. RESULTS: The statistical analysis revealed a significant difference in microleakage among the study groups (P < 0.001). The Ionoseal group followed by the control group (x-tra fil composite) had the greatest microleakage. Except for the Ionoseal group, all other groups had significantly less microleakage than the control group. CONCLUSION: The use of bonded-base techniques could reduce microleakage, including those in bulk-fill composite restorations.

Effect of Calcium Hypochlorite and Sodium Hypochlorite as Root Canal Irrigants on Push-out Bond Strength of Fiber Post Cemented with Etch-and-Rinse Resin Cement: An in Vitro Study.

Objectives: Calcium hypochlorite (CH) has been recently used as a root canal irrigant. The aim of the present study was to compare the effect of CH and sodium hypochlorite (SH), as root canal irrigants, on the push-out bond strength of fiber posts cemented with an etch-and-rinse resin cement. Materials and Methods: In this experimental in-vitro study, 40 human anterior teeth with similar root lengths were randomly divided into five groups (N=8) according to the protocol of root canal irrigation as follows: group 1: saline (control); group 2: 2.5% SH; group 3: 5.25% SH; group 4: 2.5% CH; group 5: 5% CH. Before post placement, the post space was irrigated using the same irrigation protocol, and after that, they were irrigated by distilled water. Fiber posts were cemented with All-Bond 3 bonding and Dou-Link Universal cement. After thermocycling (1000 cycles, 5-55°C), a push-out test was performed, and data were analyzed using one-way analysis of variance and Tukey's post-hoc test with SPSS version 23 (α=0.05). Results: The highest and lowest mean bond strengths were detected in groups 2 and 5, respectively. There was no significant difference between group 1 and the SH groups (P>0.05), but the difference between group 1 and the CH groups was significant (P<0.001). There was a significant difference between SH groups and CH groups (P<0.001). Conclusion: Compared to SH, as a root canal irrigant, CH decreased the push-out bond strength of fiber posts cemented with an etch-and-rinse resin cement.

Effects of Calcium Hypochlorite and Sodium Hypochlorite, as Root Canal Irrigants, on the Bond Strength of Glass Fiber Posts Cemented with Self-Adhesive Resin Cement.

OBJECTIVES: Calcium hypochlorite (Ca(OCl)2) is currently used as a root canal irrigant. The aim of this study was to compare the effects of calcium hypochlorite and sodium hypochlorite (NaOCl), as root canal irrigants, on the bond strength of posts cemented with a self-adhesive resin cement. MATERIALS AND METHODS: In this in-vitro study, 40 maxillary central incisors with similar root lengths were decoronated. The teeth were randomly divided into five groups based on the irrigant used: Group 1: normal saline (control), Group 2: 2.5% sodium hypochlorite, Group 3: 5.25% sodium hypochlorite, Group 4: 2.5% calcium hypochlorite, and Group 5: 5% calcium hypochlorite. Root canal treatments were performed with Gates-Glidden drills and the irrigant corresponding to each group was used upon changing the file and for irrigating the post space. Then, glass fiber posts were cemented by BisCem self-adhesive cement. After applying 1,000 thermocycles at 5-55°C, three samples of the mid-section of each root were prepared: one for scanning electron microscopy (SEM), and the rest for push-out testing. Data were analyzed with SPSS 23 software using one-way analysis of variance and post-hoc Tukey's test. RESULTS: The highest and lowest mean bond strengths were recorded in groups 5 and 1, respectively. There was a significant difference between the 5% calcium hypochlorite group and the other groups (P<0.001). The difference between the other groups was not significant. CONCLUSION: The use of 5% calcium hypochlorite with self-adhesive cements increases the push-out bond strength of fiber posts to radicular dentin.

In vitro evaluation of dentin tubule occlusion by three bioactive materials: A scanning electron microscopic study.

BACKGROUND: Dentin hypersensitivity (DH) is a common problem characterized by a short, sharp pain. Reduction of dentin permeability by occluding dentin tubules is considered as a method for treating DH. Many substances are available to decrease hypersensitivity. The aim of this study is to evaluate the ability of three different remineralizing agents for occluding dentinal tubules in comparison with positive and negative controls. MATERIALS AND METHODS: In this in vitro scanning electron microscopic (SEM) study, 75 extracted premolars were cut into crown and root fragments with a bur and divided into five groups: group 1: Sodium fluoride 5% varnish was applied (positive control), Group 2: No treatment (negative control), Group 3: Treated with Remin Pro (contains hydroxyapatite and fluoride), Group 4: Treated with MI paste (contains casein phosphopeptide-amorphous calcium phosphate [CPP-ACP]) and Group 5: Treated with GC tooth mousse (contains CPP-ACP). SEM images were obtained and mean tubular diameter was measured in each group. One-way ANOVA and Duncan's tests were used for statistical analysis. A significant level of α = 0.05 was set for comparison between the groups. RESULTS: Statistically significant difference was observed between Group 2 (negative control) and other four groups (P < 0.05). There was no significant difference between Groups 1, 3, 4, and 5 (P > 0.05). CONCLUSION: Under the limitations of the present in vitro study, it can be concluded that the application of a CPP-ACP paste as well as a paste which contains fluoride is effective on reduction of dentin permeability.

Evaluating the effect of antioxidant agents on shear bond strength of tooth-colored restorative materials after bleaching: A systematic review.

PURPOSE: The main objective of the present study was to make a systematic review of how antioxidant agents affect shear bond strength of tooth-colored restorative materials after bleaching. DATA SOURCES: Electronic search was used to extract the related articles on the targeted key words such as "antioxidant", "dental bleaching" and "shear bond strength" (SBS) from MeSH, PubMed, Medline, and Cochrane electronic data bases. These articles were all published before 2016. STUDY SELECTION: Inclusion criteria were restricted to English journal articles concerning humans, clinical trials, cohorts and case-control studies. Therefore, systematic reviews, case reports, letters to editors, editorials and congress abstracts were excluded from the analysis. CONCLUSIONS: Most studies conducted on the issue have produced experimental data which are rather controversial, and there is no general agreement about the reported outcomes. As an illustration, most studies have not considered the relationship between the type of antioxidant materials and the shear bond strength. In point of fact, some researchers (e.g Kimyai et al.) have concluded that antioxidants like gel and solution leave similar effects on SBS. Alternatively, certain studies (e.g., Kunt et al.) have produced inconclusive data regarding the impact of one week postponement of the restorative process on SBS after the bleaching process. The results of the studies evaluating the role of various adhesive systems used after bleaching have demonstrated that regardless of the type of adhesive system used, applying antioxidants before restorative procedures can adversely affect the bleaching agents utilized for SBS. It has also been suggested that the type of the adhesive system used might be correlated with the magnitude of SBS. The results obtained from the systematic review of the articles under investigation reflected that the use of antioxidant agents, regardless of their type, form, concentration and duration of application, can improve SBS after bleaching.

Effect of different bleaching regimens on the flexural strength of hybrid composite resin.

BACKGROUND: The entire effects of different bleaching regimens on the mechanical properties of composite resins have remained unknown. The purpose of this study was to evaluate the effects of different bleaching regimens on the flexural strength (FS) of hybrid composite resins. MATERIALS AND METHODS: In this in vitro study, 80 bar-shaped specimens of hybrid composite resins were fabricated and randomly divided into four groups, 20 specimens in each group. First group (C) was considered as control. The other groups were treated by home bleaching (HB) agent, in-office bleaching (IB) agent, and the combination regimens (HIB), respectively. The FS was evaluated by three-point bending test by using a Universal Testing Machine. All data were analyzed by using Statistical Package for the Social Sciences (SPSS) software version 18, analysis of variance (ANOVA), and Turkey's post hoc statistical tests (α = 0.05). RESULTS: The maximum mean value of FS was seen in HB group with significant differences to other groups (P < 0.05). Also, the minimum FS was observed in group HIB. CONCLUSION: Application of different bleaching regimens does not have any adverse effect on the FS of hybrid composite resins. However, the administration of HB regimens seemed to have lesser negative impact on the FS.

Effect of dentin conditioning on bond strength of fiber posts and dentin morphology: a review.

PURPOSE: Post and core systems are commonly used to restore endodontically treated teeth. A durable bond between fiber posts and dentin contributes to the success of the restorative treatment. Different irrigants are used during post space preparation and various studies have investigated the effects of these chemical agents on bond strength and dentin morphology. METHODS: The MEDLINE-PubMed, Cochrane, and SCOPUS databases were searched for appropriate papers addressing the effects of irrigants on bonding of fiber posts to dentin and on dentin morphology. Databases were searched from 2002 through 2012. The search was performed using a variety of keywords including fiber posts, bond strength, post space preparation, post space irrigation, and smear layer removal. RESULTS: Using multiple key words and different strategies, 68 publications were initially screened. The abstracts of these 68 publications were scanned for relevance, and 50 full-text articles were selected and read in detail. Thirty publications which discussed the effect of various intracanal irrigants on bond strengths of fiber posts and dentin morphology were incorporated in this review. Following review of all relevant papers, it can be concluded that bond strengths of fiber posts to radicular dentin can be affected by the irrigants used and that various irrigants affect different types of resin cements differently.

Effect of surface treatments on fracture resistance of root filled teeth with bonded fibre posts.

BACKGROUND/AIM: This study examined the effect of several dentin surface treatments on fracture resistance of root filled teeth containing bonded fibre posts. MATERIAL AND METHODS: The roots of 84 single-canal premolars were instrumented, filled with gutta-percha and randomly divided into seven groups. The coronal 9 mm of gutta-percha was removed to create a post space. In the experimental groups, canals were irrigated with distilled water, 37% phosphoric acid, 5% sodium hypochlorite, 17% EDTA, 5% sodium hypochlorite followed by 17% EDTA or 5% sodium hypochlorite followed by 10% ascorbic acid. Fibre posts were cemented using Panavia F2.0 resin cement, and the specimens were mounted in acrylic resin blocks. Following 1-week storage in an incubator, specimens were thermocycled and their fracture resistance was determined using a universal testing machine. Data were analysed using the Kruskal-Wallis test. RESULTS: Mean fracture resistance values ranged from 465.8 N in specimens treated with sodium hypochlorite and ascorbic acid to 739.1 N for those treated with sodium hypochlorite only. However, differences in fracture resistance were not statistically significant (P = 0.114). CONCLUSIONS: None of the surface treatments improved vertical fracture resistance of root filled teeth containing bonded fibre posts.

The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements.

BACKGROUND: Ultrasonic vibrations are used to remove a cemented post from a root canal requiring endodontic retreatment. Various results have been reported from the studies that evaluated the effect of ultrasonic instruments in removing the posts cemented with resin cements. The aim of this study was to evaluate the effect of ultrasonic energy on the retention of prefabricated metal post cemented with Panavia or Maxcem Elite cements. MATERIALS AND METHODS: In this in vitro study, forty eight extracted single root premolars were decoronated with a diamond disc leaving a 13 mm long root and endodontically treated. The root canals were obturated by gutta-percha up to 5 mm with vertical condensation method and the 8 mm post-space was prepared to receive a no. 2 long Dentorama post. The roots were placed in an incubator for 48 h in 37°C and 100% humidity. After mounting the teeth in acrylic blocks, posts were cemented in the root canals using Panavia F2.0 in 24 specimens and Maxcem Elite in 24 others. For half of the specimens in each subgroup, an ultrasonic device was applied for 4 min. Universal testing machine was used to measure the force needed to remove the posts with a crosshead speed of 1 mm/min until the post came out of the canal. Kruskal-Wallis test was used for statistical analysis at 5% level of significance. RESULTS: The removal force was not significantly different among the groups (P > 0.05). CONCLUSION: Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia) and the self-etch self-adhesive (Maxcem Elite) resin cements.

Reaction of rat subcutaneous connective tissue to resin composites polymerized with different light curing units and different lightening methods.

The aim of the study was to determine and compare the reaction of rat subcutaneous connective tissue to resin composites polymerized with different lights curing and lightening methods. In this in vivo study, 20 mature Wister Albino rats were used. The composite discs, 4 mm in diameter and 2 mm thick, were cured by QTH or LED light curing units with 4 different lightning methods (full power QTH, full power LED, pulse LED, and ramp LED). Five resin composite discs were implanted in each rat, so that 4 of 5 discs for implantation of cured composite discs differently and central one as control without implantation. After sacrificing at 7, 14, 30, and 60 days the inflammatory grade, fibrosis, and necrosis were determined. Freedman and Cochran tests were used to analyze the data using SPSS software ver. 15. The results of the study showed significant differences in inflammation grade and fibrosis among control group and 4 experimental groups at day 14 (P < 0.05). In necrosis, there was no significant difference among 4 groups in different times (P > 0.05). In conclusion, neither the type of light curing units (LED or QTH) nor the lightening methods can affect the grade of inflammatory reaction.