Effect of bleaching agents on sealing properties of different intraorifice barriers and root filling materials

Biological considerations of dental materials as orifice barriers for restoring root-filled teeth

There is ample published literature regarding the technical aspects of restoring root-filled teeth, but little concerning the biological impacts, consequences, and criteria for the selection of direct restorative materials following endodontic treatment. The provision of an effective coronal seal in addition to a sound root filling is known to be important in the prevention of root canal infection. This review seeks to explore the evidence concerning the selection of dental materials in the restoration of root-filled teeth, specifically with a close examination of the properties of commonly used materials as orifice barriers. © 2023 Australian Dental Association.

Evaluating the Effect of Different Intra-Orifice Barriers and Various Bleaching Agents on the Fracture Resistance of Teeth After the Walking Bleach Procedure: An In Vitro Study

Objective This study aimed to evaluate the effect of three different commercially available intra-orifice barriers and bleaching agents on root canal-treated teeth. Materials and methods Forty-five freshly extracted single-rooted incisors, canine, and premolars were collected and stored in 10% formalin. Root canal procedures were performed on the extracted teeth and these were classified into three groups and three subgroups (n=5). Group 1: resin-modified glass ionomer cement (RMGIC); placed at the level of cemento-enamel junction (CEJ) and cured for 20 seconds. Group 2: Biodentin^TM (Septodont Ltd., Saint Maur des Fausse´s, France); powder and liquid were mixed according to the manufacturer's instructions and placed at the level of CEJ, and waited for 15 minutes to set. Group 3: bulk-fill composite; placed at the level of CEJ. Group A was treated with 35% carbamide peroxide (Ultradent Opalescence 35% PF regular). Group B was bleached with 35% hydrogen peroxide (Pola Office). Group C, which was the control group, was treated with distilled water. The bleaching procedure was repeated once every seven days for a period of three weeks. After bleaching, every sample was sectioned 2 mm above the level of CEJ to remove the crown. Auniversal testing machine (UTM) was used for the evaluation of the fracture resistance of teeth. Data were analyzed for significance by using analysis of variance (ANOVA) and further pair-wise comparison was performed by pos-hoc analysis. The level of significance was set at p<0.05 Results There was a significant difference between the fracture resistance of the three materials when bleached using distilled water (p<0.05). The fracture resistance of Group 3 was significantly greater than that of Group 2 and Group 1 (p<0.05). The difference in the fracture resistance between Group 1 and Group 2 was nonsignificant (p>0.05). Conclusion Walking bleach performed via bleaching agents 35% carbamide peroxide and 35% hydrogen peroxide leads to a reduction in the fracture resistance of endodontically treated teeth; 35% hydrogen peroxide causes more fracture resistance reduction than carbamide peroxide of the same concentration. The presence of intra-orifice barriers leads to greater fracture resistance and reinforcement of endodontically treated teeth that undergo the walking bleach procedure. Bulk-fill composite can be used as an intra-orifice barrier with good fracture resistance.

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.

Evaluation of the penetration of intracoronal bleaching agents into the cervical region using different intraorifice barriers

Background

The present study aimed to make a comparison between the effects of 35% hydrogen peroxide gel (HP) and sodium perborate with distilled water (SP) bleaching agents on the sealing characteristics of glass ionomer cement (GIC), TheraBase, ProRoot MTA and Biodentine intraorifice barriers.

Methods

One hundred and twelve single-rooted mandibular human premolar teeth extracted from young patients (14–25 years) were chosen. Root cement and cementoenamel junction (CEJ) of teeth were examined under a stereomicroscope at 10 × magnification to ensure there was no cement defect or dentin gap in CEJ. After the endodontic access cavities were opened on the occlusal surfaces of the teeth, the working length was determined. Instrumentation of each root canal was performed with a ProTaper Gold rotary system in the determined working length and filled with gutta-percha + AH Plus with a single cone technique using. Root fillings were removed 3 mm short of the CEJ and sealed with one of the following intraorifice barrier materials (n = 30/group): 1. GIC; 2. TheraBase; 3. ProProot-MTA; 4. Biodentine. In each of the sub-groups, either HP or SP was used to perform intracoronal bleaching on days 1, 4, and 7. All outer surfaces of the specimens except the 3 mm cervical region were covered with nail polish and modeling wax layers. Specimens were immersed in a 5 ml Eppendorf tube that contained 2 mL of distilled water. The penetration of peroxide release was measured using the colorimetric ferric thiocyanate method. Statistical analysis of the data was performed with Three-way ANOVA and Tukey’s test (P = 0.05).

Results

In the HP groups, GIC showed the greatest peroxide release when compared with other tested groups on day 1 (P < 0.05). Biodentine and ProRoot MTA displayed a significantly lower peroxide leakage when compared to GIC and TheraBase on days 1 and 4 (P < 0.05). While GIC and TheraBase were used, HP observed higher peroxide penetration when compared with SP on days 1 and 4 (P < 0.05).

Conclusions

Peroxide diffusion was significantly influenced by the kind of intracoronal bleaching agents and intraorifice barrier materials used.

Study of the Intra-Coronal Pressure Generated by Internal Bleaching Agents and Its Influence on Temporary Restoration

Intra-coronal bleaching is a treatment that whitens non-vital teeth from within the pulp chamber, a procedure by which oxygen and free radicals are released. This in vitro study analyzed and compares the oxygen expansion produced when different bleaching agents encounter dental tissues during this type of bleaching. Here, 120 lower incisors were included and prepared to achieve conditions as close as practicable to internal bleaching with the walking bleach technique. The access cavity of the lingual surface was prepared to seal glass tubes with oil inside them by adhesive restoration once the bleach was placed inside the pulp chamber. The following bleaching groups were used: hydrogen peroxide (HP) 30% (n = 30), sodium Perborate (SP) with distilled water (n = 30), a mixture of HP 30% with SP (n = 30) and a control group (n = 30). After 10 days, the oil displacement that took place through the tube due to oxygen release was measured daily. Displacement of the oil was observed in all groups except the control group. The final mean expansion at 10 days was 335.24 ± 76.85 mm for the HP 30% group, 8.40 ± 1.74 mm for the SP group and 183.07 ± 49.93 mm for the HP30% + SP mixture. Significant statistical differences were observed between the three groups using the Games–Howell post hoc test, where HP30% caused the greatest expansion and SP the least expansion. These results suggest that the higher the amount of HP in the sample, the more oxygen expansion is observed, so that temporary restoration must be performed more carefully to avoid displacement.

Influence of intracoronal bleaching agents on the bond strength of MTA cements to composite resin and their surface morphology

The objective of the present in vitro study was to evaluate micro-tensile bond strength (µSBS) of MTA cements to composite resin using a universal adhesive after internal bleaching procedure, and to examine surface characteristics of MTA cements exposed to bleaching agents. MTA specimens were divided into three subgroups according to the bleaching agent used which were, 37% carbamide peroxide (CP), 35% hydrogen peroxide (HP), and no exposure as a control group (n = 12). After exposure to bleaching agent, composite resins were applied to MTA surfaces using a universal adhesive in self-etch mode. The specimens were exposed to a shear force until failure to evaluate bond strength. MTA surfaces were investigated using scanning electron microscopy (SEM) to observe the effects of the bleaching agents. Differences between groups were analyzed using two-way ANOVA test and intergroup comparisons were assessed with Tukey test (p < 0.05). Although there was a slight difference in bond strength between bleaching agents (CP and HP), no significant difference was found, irrespective of MTA cement. After the HP application, the bond strength values decreased approximately by half compared with the controls. SEM results demonstrated distinct morphological differences between the intact MTA surface (control) and treated MTA surface. Distinct micro-cracks, surface irregularities, and capillary voids formed due to the superficial dissolution caused by peroxides. Exposure to the intra-coronal bleaching agents had a negative influence on the surface morphology of MTA cements and their bond strength to composite resin.

Assessment of Oxygen Expansion during Internal Bleaching with Enamel and Dentin: A Comparative In Vitro Study

Internal bleaching is a conservative, non-invasive, and simple treatment that is frequently performed in daily clinical practice. The present in vitro study analyzes the oxygen expansion of different bleaching agents resulting from the oxidation reaction when interacting with enamel and dentin. Enamel and dentin were crushed separately until obtaining a fine powder with particles of an approximate size between 0.06 and 0.2 mm. Each enamel and dentin sample were mixed with 37% carbamide peroxide (CP 37%), 30% hydrogen peroxide (HP 30%), sodium perborate (SP) combined with HP 30% (HP 30% + SP) and SP with distilled water (SP). A total of 280 1 mm diameter glass tubes were used with 70 for each bleaching agent (30 for powdered enamel evaluation, 30 for powdered dentin evaluation, and 10 controls). The bleaching agents were placed in the prepared tubes immediately after mixing the components. As expansion occurred, the oil inside the tube was displaced, through which the resulting expansion was evaluated and measured for 10 days. A significant expansion was observed that varied in magnitude according to the bleaching agent and the tooth structure used. Student's t test and Welch's ANOVA were used to analyze the data obtained. The highest mean expansion of both enamel and dentin was observed with 30% HP (66.6 mm for enamel, 94.5 mm for dentin) followed by HP 30% + SP (48.6 mm for enamel, 52.7 mm for dentin), CP 37% (38.4 mm for enamel, 52.6 mm for dentin) and finally SP with water (12.7 mm for enamel, 4.4 mm for dentin). It was observed that the expansion in the SP group with enamel was significantly lower than in the rest of the groups, while that registered for HP 30% was significantly higher. (p < 0.001). The results with dentin were similar, with a significantly lower expansion for SP and higher for HP 30% (p < 0.001). The oxygen expansion observed as a result of the interaction between bleaching agents and dental tissues could contribute to improving our understanding of bleaching and its results. These results suggest that bleaching agents react with the organic component of the tooth structure.

Comparison of MTA, CEM Cement, and Biodentine as Coronal Plug during Internal Bleaching: An In Vitro Study

BACKGROUND

Internal bleaching is a choice of treatment in discolored endodontically treated teeth. Cervical root resorption is one of the important complications of this treatment. A suggested procedure to prevent this type of resorption is using a coronal barrier under the bleaching materials. The aim of the study was to compare the microleakage of mineral trioxide aggregate (MTA), calcium-enriched mixture (CEM) cement, and Biodentine.

MATERIALS AND METHODS

In this in vitro study, a total of 60 single canal incisors were included. They were randomly divided into three experimental groups (n = 16), one positive control group (n = 6), and one negative control group (n = 6). Coronal portion of the canals in the experimental groups was sealed with 3 mm of MTA, CEM cement, or Biodentine as a coronal barrier. After 3 days, specimens were bleached. A fresh Enterococcus faecalis suspension was added to the samples. The culture tubes were observed for 45 days, and the daily turbidity was recorded. Statistical analysis was accomplished by the Kaplan-Meier test and SPSS 22.

RESULTS

All positive samples showed turbidity, whereas none of the negative samples allowed bacterial leakage. Results showed no significant difference between MTA, CEM cement, and Biodentine groups. (P value = 0.304, 0.695, and 0.217). The bacterial microleakage for the two groups also did not show significant differences.

CONCLUSIONS

CEM cement and Biodentine showed promising results as coronal plug, and clinical studies are needed to test these materials with MTA for avoiding microleakage in internal bleaching treatment.

Effects of intracoronal bleaching agents on the surface properties of mineral trioxide aggregate

Bleaching agents may affect surface properties of mineral trioxide aggregate (MTA) as a coronal barrier. The purpose of this study was to investigate surface properties of MTA after exposure to intracoronal bleaching agents. MTA was set in acrylic molds with a 4 mm high central hole and a 6 mm diameter. Specimens were divided into four groups (n = 10); three groups were exposed to bleaching agents three times on every fourth day (carbamide peroxide-CP, hydrogen peroxide-HP, sodium perborate-SP) and a control group-C. The surface roughness and Vickers surface microhardness were measured. Differences between groups were analyzed using a Kruskal-Wallis test and intergroup comparisons were assessed with a Mann-Whitney U test with a Bonferroni correction (p < 0.0001). The microstructure and elemental composition were observed using a scanning electron microscope (SEM) and an energy-dispersive X-ray microanalysis (EDX) system. In terms of microhardness, the decrease in the HP group was significantly greater than that of the CP and SP groups; CP group significantly greater than that of the SP group, however, there was no significant difference between the SP and C groups. Surface roughness values were compared between groups, and no significant differences were observed between the CP and HP groups, and they exhibited significantly higher roughness values than the SP and C groups. SEM/EDX showed that the bleaching agents affected the elemental distribution. Bleaching agents adversely affected the surface roughness, surface microhardness and elemental distribution of MTA, with exposure to SP causing fewer changes on the surface properties than CP or HP.

Push-out bond strength of intra-orifice barrier materials: Bulk-fill composite versus calcium silicate cement

Background. The aim of this study was to compare the push-out bond strengths of calcium silicate-based ProRoot MTA and Biodentine cements and SureFil SDR and EverX Posterior bulk-fill composite resins.

Methods. Twenty-four single-rooted maxillary central incisors were sectioned below the cementoenamel junction, and the root canals were instrumented using rotary files. Thereafter, a parallel post drill was used to obtain a standardized root canal dimension. The roots were randomly assigned to one of the following groups with respect to the intra-orifice barrier used: ProRoot MTA; Biodentine; SureFil SDR; EverX Posterior. Five 1-mm-thick sections were obtained from the coronal aspect of each root. Push-out bond strength testing was performed and data were analyzed with Kruskal-Wallis and post hoc Dunn tests (P<0.05).

Results. SureFil SDR and EverX Posterior bulk-fill composite resins’ bond strengths were significantly higher than ProRoot MTA and Biodentine calcium silicate cements. However, no statistically significant differences were observed between bulk-fill composite resins values and calcium silicate cement values.

Conclusion. Within the limitations of present study, calcium silicate-based ProRoot MTA cement’s push-out bond strength was lower than those of Biodentine, SureFil SDR and EverX Posterior materials.

Effect of Carbamide Peroxide on the Push-out Bond Strength of Different Composition Glass-Ionomer Cement to Root Canal Dentin when used as Cervical Barrier

AIM

To evaluate the effect of 37% carbamide peroxide on the bond strength of conventional or resin-modified glass-ionomer cements when used as a cervical barrier in endodontically-treated teeth.

MATERIALS AND METHODS

After root canal instrumentation and obturation, 40 specimens of the cement-enamel junction were obtained after transversal root canal sectioning from human extracted canines. The root canal specimens were standardized and filled with the following materials (n = 10, each group): G1: zinc phosphate (control), G2: Ketac glass-ionomer, G3: vitrebond glass-ionomer or G4: GC GL glass-ionomer. After 24 hours, the specimens were subjected to an application of 37% carbamide peroxide for 21 days, changed each 7 days and stored in an artificial pulp chamber. The specimens were then submitted to push-out bond strength testing with an electromechanical test machine (EMIC) and the failure mode in each specimen was analyzed with confocal microscopy (LEXT).

RESULTS

G3 and G4 showed higher bond strengths values than the other groups (p < 0.05), and were similar to each other (p > 0.05). G1 showed the lowest bond strength value (p < 0.05).

CONCLUSION

Glass-ionomer cements showed higher bond strength values than the zinc phosphate cement, and resin-modified glass-ionomer cements presented the highest push-out values to root canal dentin (GC, GL and Vitrebond).

CLINICAL SIGNIFICANCE

Glass ionomer cements are recommended to use as cervical barrier materials before the internal dental bleaching, but its efficiency is questionable.

Fluid flow evaluation of coronal microleakage intraorifice barrier materials in endodontically treated teeth

Objective:

The objective of this study was to compare the coronal microleakage intraorifice barrier materials, called CoroSeal (CS), fissur sealant (FS), flowable composite FC, and policarboksilate cement (PC), by using the computerized fluid filtration method.

Materials and Methods:

Fifty freshly extracted, single-canal human maxillary central teeth were used in this study. The teeth were decoronated to a standardized root length of 15 mm. After preparation and irrigation, all the teeth were obturated with gutta-percha and AH-Plus. In all teeth, the coronal 2 mm of root filling was removed and replaced with one of the intraorifice barriers. According to intraorifice barriers, teeth were divided randomly into 4 experimental groups (n = 10) and 2 control groups (n = 5). Group 1: CS; Group 2: FS; Group 3: FC; and Group 4: PC.

Positive Control Group:

No barrier material was used.

Negative Control Group:

Roots were completely coated with the nail polish, including the orifice. Leakage was evaluated by using a computerized fluid filtration model. Differences in fluid filtration among groups were subjected to statistical analysis using the Kruskal-Wallis Test and multiple comparisons test.

Results:

A value of P < 0.05 was statistically significant. Statistical analysis has indicated that the CS leaked significantly less than other groups (P < 0.05). There was a significant difference between FS and PC (P < 0.05), in contrast there was no significant difference between FS and FC (P > 0.05).

Conclusions:

Using the CS material as an intraorrifice barrier material reduced amount of microleakage as compared with FS, FC, and PC.