Effects of endodontic irrigation solutions on structural, chemical, and mechanical properties of coronal dentin: A scoping review

Do irrigation solutions effect bond strength of composite resin to deep margin elevation material? An in-vitro study

BACKGROUND

The deep margin elevation (DME) technique provides advantages for root canal treatment, but the impact of applied irrigation protocols on bonding for subsequent restorations is a significant concern. The aim of this in vitro study was to test the bond strength of a flowable resin material used in DME restorations after composite restorations were exposed to different irrigation protocols.

METHODS

Standard composite samples (G-aenial® Universal Injectable) were divided into nine groups according to irrigation protocols. Untreated composite sample were used as control. The group A were kept in 5.25% sodium hypochlorite (NaOCl) and the group B were kept in 3.5% chlorine dioxide (ClO2) for 30 min. Then, the following treatment protocols were applied to the subgroups, respectively. Group1A/B: 17%EDTA + 5.25%NaOCl + Distilled Water + 2%CHX, Group2A/B: 18%HEDP + 5.25%NaOCl + Distilled Water + 2%CHX, Group3A/B: 17%EDTA + 3.5%ClO2 + Distilled Water + 2%CHX, Group4A/B: 18%HEDP + 3.5%ClO2 + Distilled Water + 2%CHX. After irrigation procedures, samples were washed with distilled water and sandblasted. G-Premio Bond and composite restorations (G-aenial® A'CHORD) were applied. The samples were then cut perpendicular to the interface with an IsoMet® low speed diamond saw under water. For the microtensile bond strength test, rectangular sticks with an average cross-sectional area of ∼1 mm2 will be obtained. The first section with 1-mm thickness was excluded to prevent its possible confounding effect on the results. Three sections were obtained of each sample (n = 15) and tested for microtensile bond strength. The analysis of the data collected in accordance with the purpose of the study was performed with One-way ANOVA (n = 15). For multiple comparisons between groups, it was evaluated with Tukey HSD test.

RESULTS

Groups A1 and A2, immersed in NaOCl for 30 min, showed statistically significantly lower bond strength compared to Group B3, immersed in ClO₂ for 30 min, and the control group (P < 0.05). The use of ClO₂ irrigation is recommended due to its positive effects on bond strength.

CONCLUSION

Prolonged NaOCl irrigation may adversely affect the bond strength of flowable composites used for deep margin elevation.

Effect of immediate pre-endodontic dentin sealing on the cuspal deflection and fracture strength of endodontically treated teeth

OBJECTIVES

This study aims to measure and compare the effects of immediate pre-endodontic dentin sealing (IPDS) and late dentin hybridization (LDh), combined with two different irrigation protocols (NaOCl/EDTA or normal saline), on cuspal deflection (CD) and fracture strength (FS) of endodontically treated teeth.

MATERIALS AND METHODS

Sixty maxillary first premolars were divided into four experimental groups (A1: LDh + NS, A2: LDh + NaOCl/EDTA, B1: IPDS + NS, B2: IPDS + NaOCl/EDTA) and two control groups (C: sound teeth, D: unrestored teeth). Teeth underwent standardized MOD cavity preparation, endodontic treatment, and restoration, except for group D was left without restoration. CD was measured after cavity preparation, 15 min post-restoration, and after thermocycling. FS was assessed using a universal testing machine.

RESULTS

No significant CD differences were found after cavity preparation. However, 15 min post-restoration, LDh groups (A1, A2) exhibited significantly higher CD than IPDS groups (B1, B2), with A2 group CD being higher than A1 group. After thermocycling, IPDS groups demonstrated greater cuspal relaxation compared to LDh groups. FS was highest in sound teeth (1533.2N) and lowest in unrestored teeth (571.5N). IPDS groups had significantly higher FS than LDh groups, with no significant difference between B1 and B2 groups.

CONCLUSIONS

The study concluded that IPDS reduces CD and enhances FS compared to LDh, suggesting it as an effective step before endodontic treatment. NaOCl/EDTA irrigation influenced CD and FS in LDh groups but had no significant impact in IPDS groups.

CLINICAL RELEVANCE

Dentin sealing before root canal treatment and prior to exposure to chemical substances (such as irrigation with NaOCl) enhances the structural integrity of endodontically treated teeth. This protective measure protects the freshly cut dentin from the detrimental effects of these substances, thereby improving the bonding strength and overall clinical outcomes.

Advancing Adhesive Strategies for Endodontically Treated Teeth-Part II: Dentin Sealing Before Irrigation Increases Long-Term Microtensile Bond Strength to Coronal Dentin

OBJECTIVE

To compare the long-term microtensile bond strength (μTBS) to coronal dentin using pre-endodontic dentin sealing (PEDS) and post-endodontic adhesion (PEA) techniques under various endodontic irrigation protocols.

MATERIALS AND METHODS

Ten study groups (n = 10) were established based on the timing of adhesive application (PEDS versus PEA) and irrigation protocol: distilled water (control), 3% sodium hypochlorite (NaOCl), 3% NaOCl followed by 17% ethylenediaminetetraacetic acid (EDTA), 3% NaOCl followed by 17% EDTA and 2% chlorhexidine, and a mixture of 3% NaOCl and 9% etidronic acid (HEDP). Specimens underwent μTBS testing after a six-month microspecimen aging period. Fracture patterns were analyzed, and adhesive interfaces were assessed using scanning electron microscopy (SEM). Statistical analysis employed a mixed linear regression model with a 5% significance level.

RESULTS

PEDS consistently preserved high bond strength across all irrigation protocols (57.4-59.5 MPa), while PEA groups treated with endodontic irrigants resulted in significantly lower values (33.3-40.8 MPa; p < 0.001). No significant differences were observed within the PEDS groups (p > 0.05). SEM analysis revealed consistent hybrid layers in PEDS and PEA/Control groups, while PEA groups treated with endodontic irrigation solutions showed significant resin-dentin interface variations and interfacial gaps.

CONCLUSIONS

The PEDS technique preserved high and consistent μTBS regardless of the irrigation protocol, whereas endodontically irrigated PEA groups exhibited significantly reduced bond strength. PEDS offers a predictable approach to optimizing adhesive performance in endodontic-restorative treatments.

CLINICAL SIGNIFICANCE

Integrating PEDS into routine endodontic-restorative workflow is recommended to enhance long-term bond strength to coronal dentin. The PEDS technique ensures consistent adhesive performance regardless of the endodontic irrigation protocol, enhancing restorative predictability and treatment success while preserving tooth structure.

The impact of passive ultrasonic irrigation on the bond strength of two different self-etch adhesives to human pulp chamber dentine: a laboratory investigation

OBJECTIVES

To evaluate the impact of passive ultrasonic irrigation on the micro-tensile bond strength of two different self-etch adhesive systems, including a universal one-step adhesive and a two-step adhesive system, to pulp chamber dentine compared to conventional syringe irrigation.

METHODS

Twenty-four extracted human mandibular first molar teeth were chosen according to strict criteria and mounted in epoxy resin blocks. Subsequently, the pulp chambers were exposed using an Isomet cutting machine. The specimens were numbered and assigned to four groups (6 teeth each) based on the canal irrigation method and the adhesive system used as follows: Conventional syringe irrigation in which a universal one-step self-etch adhesive system was applied (CSIU), conventional syringe irrigation in which a two-step self-etch adhesive system was used (CSIT), passive ultrasonic irrigation in which a universal one-step self-etch adhesive system was utilized (PUIU), and passive ultrasonic irrigation in which a two-step self-etch adhesive system was employed (PUIT). Following placement of the final restoration and submission to simultaneous thermo-mechanical cycling (artificial aging) equivalent to 6-month intra-oral aging, the teeth were sectioned and dentine/restoration beams were prepared. The micro-tensile bond strength was evaluated and the failure mode was defined, with a confirmatory evaluation of the dentine-resin interface using a scanning electron microscope. Statistical analysis was conducted using one-way ANOVA and Tukey's post hoc tests to compare irrigation regimens for each adhesive technique independently, while failure modes of each adhesive system were represented as the frequency for each irrigation method. The significance level was set at 5%, with a confidence interval (CI) of 95%.

RESULTS

The micro-tensile bond strength of composite resin restorations to pulp chamber dentine was reduced significantly with ultrasonic irrigation with more unfavorable failure modes compared to syringe irrigation (P < 0.0001), irrespective of the type of adhesive system used. The means of the micro-tensile strength for teeth treated with the two-step adhesive system were 26.1055 ± 4.7611 MPa and 16.0079 ± 3.7665 MPa for CSIT and PUIT, respectively. For teeth treated with the universal adhesive system, the mean for CSIU (20.1818 ± 3.8500 MPa) was significantly higher than that of PUIU (11.2090 ± 2.9928 MPa). The micro-tensile bond strength was significantly greater with the two-step adhesive system compared to the universal adhesive, regardless of the irrigation method (p < 0.05). An adhesive layer with varying thickness was noted in all groups, displaying distinct morphological features.

CONCLUSIONS

Within the limitations of the present laboratory investigation, ultrasonic irrigation may negatively affect the bond between composite resin restorations and pulp chamber dentine compared to conventional syringe irrigation. The two-step self-etch adhesive tended to achieve a stronger bond to pulp chamber dentine than the universal one-step self-etch adhesive.

CLINICAL RELEVANCE

While ultrasonic irrigation would be essential for effective root canal debridement and disinfection, it is imperative for clinicians to consider its potential adverse effects. This method may considerably impact the bond strength of composite resin restorations to the pulp chamber dentine, particularly when compared to conventional syringe irrigation. In root canal-treated teeth, a two-step self-etch adhesive system might be more effective in maximizing the bond strength to pulp chamber dentine than a universal adhesive system. However, these findings were concluded under the conditions of the present study and must be interpreted cautiously. Further research is recommended to validate these results and fully understand the clinical ramifications of ultrasonic irrigation on adhesive performance in different dental situations.

CLINICAL TRIAL NUMBER

Non-applicable. Conducting the current experiment was limited to the approval of the local Research Ethics Committee at the Faculty of Dentistry, Minia University, Egypt (Committee No. 106, Registration No. 910, Date: April 30, 2024).

Advancing Adhesive Strategies for Endodontically Treated Teeth-Part I: Impact of Endodontic Irrigation Protocols on the Chemical Composition and Structural Integrity of Coronal Dentin

OBJECTIVE

To evaluate the effects of four endodontic irrigation protocols on the chemical composition and ultrastructure of coronal dentin.

MATERIALS AND METHODS

Coronal dentin fragments were assigned to five study groups: NaOCl (3% sodium hypochlorite), NaOCl/EDTA (3% NaOCl and 17% ethylenediaminetetraacetic acid), NaOCl/EDTA/CHX (3% NaOCl, 17% EDTA and 2% chlorhexidine), NaOCl/HEDP (mixture of 3% NaOCl and 9% etidronic acid), and control (distilled water). Confocal Raman microscopy was employed to analyze the spatial distribution of organic and inorganic components, while attenuated total reflection Fourier transform infrared spectroscopy and energy-dispersive spectroscopy were used to assess the surface composition of dentin. Ultrastructural evaluation was conducted using scanning electron microscopy (SEM). Statistical analysis was performed using a mixed linear model with a significance level of 0.05.

RESULTS

All NaOCl-treated groups showed reduced amide II (p < 0.001), indicating protein degradation. Exclusive NaOCl irrigation yielded the lowest amide II, highest mineral content, and increased phosphate/amide II and carbonate/phosphate ratios (p < 0.05). Chelators reduced mineral content (p < 0.001), with NaOCl/HEDP and NaOCl/EDTA/CHX producing more mineralized surfaces than NaOCl/EDTA and control groups (p < 0.05). A general decrease in organic (C and N) and an increase in inorganic (O, P, and Ca) components occurred across treatments, particularly in NaOCl and NaOCl/HEDP groups. EDTA disturbed the Ca/P equilibrium (p < 0.05). SEM showed a dense smear layer and mostly obliterated tubules in NaOCl and control samples, while chelators reduced the smear layer, partially opened tubules, and caused erosion.

CONCLUSIONS

Exclusive use of 3% NaOCl produces hypermineralized, collagen-depleted coronal dentinal surfaces, with a dense smear layer. Sequential irrigation with 17% EDTA induces stronger demineralization compared to a continuous chelation protocol with 9% HEDP. Both EDTA- and HEDP-treated coronal dentin display partially opened dentinal tubules, signs of erosion, and substantial smear layer reduction.

CLINICAL SIGNIFICANCE

Clinically recommended endodontic irrigation protocols significantly alter the chemical composition and ultrastructural integrity of coronal dentin, the primary substrate for adhesive restorations. These findings enhance the understanding of post-irrigation coronal dentin conditions and their potential implications on the interaction with adhesive restorative materials.

Retreatment or replacement of previous endodontically treated premolars with recurrent apical periodontitis? An 8-year historical cohort study

OBJECTIVES

The study evaluated previously-endodontically-treated premolars affected by periapical lesions and/or secondary caries requiring a multidisciplinary decision between (non-surgical) retreatment or extraction and implant replacement over an 8-year minimum follow-up.

MATERIALS AND METHODS

The decision-making was performed among a pool of patients attending a University Dental School. All patients presented at least one failing previously endodontically treated premolar. Recorded parameters were: structural conditions (residual coronal-structure, caries), periodontal and endodontic status (CEJ-MBL, initial-PAI, post-presence). Two experienced operators made the decision-making and classified teeth as retreatable and restorable (Endo-group) or suitable for extraction and implant replacement (Implant-group). Logistic regression and Cox-proportional-hazard analyses with clustered-standard-errors compared baseline-characteristics and treatment-outcomes. Odds-ratios (ORs) with 95% confidence-intervals (CIs) were reported for baseline-characteristics. Hazard-ratios (HRs) expressed the association of treatment-groups with time-to-event.

RESULTS

Ninety-six patients (n = 124 premolars) were enrolled (49 M;47 F; mean-age 53.1 ± 11.6 years). The decision-making splitted 54.8% treatments to Endo-group (n = 68) and 45.2% to Implant-group (n = 56). The 8-year survival were 85.1% for Endo-group and 98.2% for Implant-group. The 8-year success were 80.5% and 93.9%. The HR from Cox regression favored Implant-group (HR = 0.12, P = 0.049). The Endo-group showed the highest number of critical complications (15%) due to fractures, despite the healing of lesions. Implant-group had a higher percentage of minor prosthetic complications (14%).

CONCLUSIONS

Endo-group demonstrated higher percentage of critical complications compared to Implant-group during the follow-up. Root fractures were accounted as main responsible, while periapical disease did not affect healing, survival and clinical longevity.

CLINICAL SIGNIFICANCE

Insufficient crown structure was the major parameter associated with root fracture. In these cases, implant replacement strategy represented an adequate therapy justified by the higher success compared to root canal retreatment.

Assessment of Endocyn on Dental Pulp Stem Cells (DPSCs): A Pilot Study of Endodontic Irrigant Effects

Many endodontic procedures within the pediatric population are performed with patients aged 12 years and older, using intracanal irrigants to complement mechanical debridement for the removal of debris and to disinfect the root canal system. The use of antimicrobial irrigants that limit damage to the dental pulp are the goals of endodontic biomaterials research. Using an existing biorepository of dental pulp stem cells (DPSCs), Endocyn was evaluated in varying concentrations in proliferation and viability assays, and compared with positive (sodium hypochlorite or bleach) and negative (phosphate-buffered saline) controls. The DPSC viability was reduced in the range of -8.3% to -15.8%, p = 0.22 to p = 0.042, while the growth inhibition varied between -29.7% and -63%, p = 0.041 to p = 0.022. However, the RNA analysis revealed that no significant changes in biomarker mRNA expression (Nestin, NANOG, Sox2, Oct4, CD73, CD90, and CD105) were observed. These data demonstrated that all of the concentrations of Endocyn inhibited the DPSC viability and growth, although only high concentrations were statistically significant. Moreover, the administration of Endocyn did not alter the DPSC biomarker expression, which are novel and important findings not previously observed or reported that may assist with the development of clinical decision protocols and methods for the treatment of vital pulp tissue.

Effect of Final Irrigation Solutions on Mechanical Properties of Root Canal Dentine Running title: Final Irrigation on Mechanical Properties

OBJECTIVES

The final irrigation solution should have the capability of a chelation agent to remove the smear layer. The purpose of this study was to determine the effect of EDTA, novel silver citrate, and chitosan nanoparticles as a final irrigation solution on the mechanical properties of root canal dentine, namely the flexural strength and elastic modulus.

METHODS

Thirty-two intact, single, and straight roots, with no caries, no cracks, and no restoration of premolars, were assigned into four groups of 8 teeth each. Group 1: irrigated with EDTA; Group 2: irrigated with novel silver citrate; Group 3: irrigated with chitosan nanoparticles; Group 4: irrigated with saline as control. Using a Universal Testing Machine, each sample was tested for flexural strength and elastic modulus with a three-point bend test. The data were analysed using one-way ANOVA and followed by the Tukey's test with a significance level of 95%.

RESULTS

Chitosan nanoparticles generated the highest flexural strength and elastic modulus of root canal dentine (212.03 +- 1.64 and 16.40 +- 1.05, respectively) than EDTA (127.10 +- 0.90 and 7.37 +- 0.94) and novel silver citrate (177.87 +- 2.03, and 12.27 +- 1.01) (p<0.05). However, chitosan nanoparticles have similar flexural strength and elastic modulus of root canal dentine when compared to saline (213.76 +- 1.48, 17.02 +- 1.14, respectively) (p>0.05).

CONCLUSION

Among final irrigations used, chitosan nanoparticles produced the highest flexural strength and elastic modulus of root canal dentine compared to EDTA and novel silver citrate.