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

At a Glance

Metadata	Details
Publication Date	2025-05-28
Journal	BMC Oral Health
Authors	Şeref Nur Mutlu, Yasemin Derya FİDANCIOĞLU, Hatice Büyüközer Özkan, Hayriye Esra Ülker
Institutions	Selçuk University, Necmettin Erbakan University
Analysis	Full AI Review Included

Executive Summary

This in-vitro study investigated the chemical compatibility and resulting bond strength degradation of flowable composite materials (used for Deep Margin Elevation, DME) when exposed to common endodontic irrigation solutions.

Objective: Quantify the microtensile bond strength (µTBS) between a flowable DME composite and a restorative composite after the DME material surface was subjected to various irrigation protocols.
Primary Degradation Agent: Prolonged exposure (30 min) to 5.25% Sodium Hypochlorite (NaOCl) significantly reduced the bond strength of the resin composite surface.
Quantified Failure: NaOCl-exposed groups (A1, A2) exhibited mean bond strengths of approximately 25 MPa, representing a 33% reduction compared to the untreated control (37.44 MPa).
Superior Alternative: Initial exposure to 3.5% Chlorine Dioxide (ClO₂) resulted in bond strengths statistically similar to the control group (up to 36.81 MPa in Group B3).
Mechanism: NaOCl is believed to dissolve the organic matrix of the resin, reducing surface fracture resistance and inhibiting subsequent bonding. ClO₂ demonstrated lower material cytotoxicity and degradation potential.
Engineering Implication: Material selection for intermediate resin layers must prioritize chemical inertness against strong oxidizers used in subsequent processing steps to ensure long-term structural integrity.

Technical Specifications

The following table summarizes the key material parameters and measured results from the microtensile bond strength (µTBS) testing.

Parameter	Value	Unit	Context
Initial Oxidizer Concentration (NaOCl)	5.25	%	Group A exposure (30 min)
Initial Oxidizer Concentration (ClO₂)	3.5	%	Group B exposure (30 min)
Chelating Agent 1 (EDTA)	17	%	Applied for 1 min
Chelating Agent 2 (HEDP)	18	%	Applied for 5 min
Final Rinse Solution (CHX)	2	%	Chlorhexidine (Applied for 1 min)
Composite Light Curing Intensity	1000	mW/cm²	Used for both flowable and restorative layers
Surface Activation Particle Size	40	µm	Sodium Bicarbonate (Sandblasting)
Sandblasting Angle/Distance	30° / 5	mm	Standardized surface preparation
Tensile Test Crosshead Speed	1.0	mm/min	Rate of applied tensile force
Control Bond Strength (Mean)	37.44 ± 4.38	MPa	Untreated composite interface
Lowest Bond Strength (Mean)	25.12 ± 6.10	MPa	Group A2 (NaOCl + HEDP + NaOCl sequence)
Highest Test Group Bond Strength (Mean)	36.81 ± 10.14	MPa	Group B3 (ClO₂ + EDTA + ClO₂ sequence)

Key Methodologies

The study utilized a standardized protocol to simulate the clinical sequence of deep margin elevation followed by root canal irrigation and final restoration.

Sample Fabrication: G-aenial Universal Injectable (flowable composite) blocks (7 x 7 x 10 mm) were incrementally condensed and light-cured (20 s per increment, 1000 mW/cm²).
Surface Preparation: Block surfaces were polished with 600-grit abrasive paper to ensure a uniform substrate for chemical exposure.
Initial Chemical Exposure: Blocks were divided into two main groups (A and B) and immersed in 5 ml of either 5.25% NaOCl (Group A) or 3.5% ClO₂ (Group B) for 30 minutes, with solution renewal every 10 minutes.
Final Irrigation Protocols: Subgroups (A1-A4, B1-B4) received specific sequences involving chelating agents (17% EDTA or 18% HEDP), intermediate rinses (NaOCl or ClO₂), Distilled Water (DW), and a final 2% CHX rinse.
Surface Activation: All treated surfaces were air-abraded using 40 µm Sodium Bicarbonate powder for 10 s at a 5 mm distance and 30° angle.
Bonding and Restoration: G-Premio Bond adhesive was applied and light-cured. G-aenial A’CHORD (restorative composite) was then incrementally applied and light-cured onto the treated flowable composite surface.
Microtensile Specimen Preparation: The composite blocks were sectioned perpendicular to the interface using an IsoMet low speed diamond saw to obtain rectangular sticks with a target cross-sectional area of ~1 mm².
Mechanical Testing: Sticks (n=15 per group) were fixed to a universal testing device and tested for µTBS at a crosshead speed of 1.0 mm/min.

Commercial Applications

The findings of this study are relevant to industries focused on polymer stability, adhesive engineering, and material performance in chemically challenging environments.

Advanced Polymer Engineering: Provides critical data for selecting methacrylate-based resin systems (like Bis-MEPP and dimethacrylate) that must maintain structural integrity when exposed to strong oxidizing agents (e.g., hypochlorites) used in cleaning or sterilization protocols.
Adhesive System Development: Informs the design of multi-layer adhesive systems, emphasizing the need for chemically resistant primers or intermediate layers to prevent bond degradation caused by environmental chemical exposure.
Medical Device and Implant Materials: Relevant for materials used in surgical or restorative procedures where tissues or devices are exposed to strong disinfectants (NaOCl, ClO₂). It supports the use of ClO₂-based protocols for minimizing material damage.
Composite Repair and Maintenance: Establishes evidence-based protocols for surface preparation and bonding when repairing existing resin-based structures that have undergone chemical insult, confirming that mechanical roughening (sandblasting) must be coupled with effective chemical neutralization.
Water Treatment and Disinfection Systems: The comparative performance of NaOCl versus ClO₂ highlights the differential impact of these common industrial disinfectants on polymer and composite infrastructure, favoring ClO₂ for applications requiring material preservation.

Tech Support

Original Source

DOI: https://doi.org/10.1186/s12903-025-06229-2