Microleakage and characteristics of resin-tooth tissues interface of a self-etch and an etch-and-rinse adhesive systems

Adhesion to enamel and dentine: an update

With the continuous development of adhesive technology leading to a wide variety of bonding systems in the market, clinicians are often faced with a vast number of systems to choose from. Although research and manufacture of bonding systems is constantly progressing, the focus has generally been on simplifying the bonding process by reducing the number of clinical steps, with little emphasis on evidence-based performance. This article draws attention to the current strategies of common commercially available products to guide clinicians during bonding system selection and application.

Dental restoration operative time and analysis of the internal gap of conventional resins (Incremental Technique) vs. Bulk Fill (Single-Increment Technique): In vitro study

Background

To determine the operative time and the internal restoration gap in the restoration-tooth interface in the cavity floor using an incremental technique for conventional resins and the single-increment technique for the bulk fill resin.

Material and Methods

In this in vitro experimental study, the internal gaps of the restoration-tooth interfaces in the cavity floors of two conventional resins and two bulk fill resins were microscopically analyzed, and the restoration times of the single-increment technique and the incremental technique were determined.

Results

Bulk fill resins had smaller internal gap (63.31 µm) than conventional resins (333.14 µm). Regarding the restoration time, the single-increment technique obtained the best results in operative time (3.52 minutes), with significant differences relative to the incremental technique.

Conclusions

The Tetric N-Ceram bulk fill resin presented better performance than conventional resins relative to the internal gap of the restoration-tooth interface in the cavity floor. In addition, the single-increment technique presented a short clinical restoration time. Key words:Composite, internal gap, restoration technique.

Exploration and preliminary clinical investigation of an adhesive approach for primary tooth restoration

The current study aims to investigate a suitable adhesive for primary tooth enamel. Shear bond strength (SBS) of primary teeth and the length of resin protrusion were analyzed using one-way ANOVA with Bonferroni multiple comparison tests after etching with 35% H ₃PO ₄. SBS and marginal microleakage tests were conducted with Single Bond Universal (SBU)/Single Bond 2 (SB2) adhesives with or without pre-etching using a nonparametric Kruskal-Wallis test. Clinical investigations were performed to validate the adhesive for primary teeth restoration using Chi-square tests. Results showed that the SBS and length of resin protrusion increased significantly with the etching time. Teeth in the SBU with 35% H ₃PO ₄ pre-etching groups had higher bond strength and lower marginal microleakage than those in the SB2 groups. Mixed fractures were more common in the 35% H ₃PO ₄ etched 30 s + SB2/SBU groups. Clinical investigations showed significant differences between the two groups in cumulative retention rates at the 6-, 12- and 18-month follow-up evaluations, as well as in marginal adaptation, discoloration, and secondary caries at the 12- and 18-month follow-up assessments. Together, pre-etching primary teeth enamel for 30 s before SBU treatment improved clinical composite resin restoration, which can provide a suitable approach for restoration of primary teeth.

Effects of carbodiimide combined with ethanol-wet bonding pretreatment on dentin bonding properties: an in vitro study

Purpose

This study evaluated the combined effects of Carbodiimide (EDC) and ethanol-wet bonding (EWB) pretreatment on the bond strength and resin-dentin surface.

Methods

Phosphoric acid-etched dentin specimens were randomly divided into five groups based on the following pretreatments: deionized water (control), EWB, 0.3M EDC in water (EDCw), EDC water solution combined EWB (EDCw + EWB), and 0.3M EDC in ethanol (EDCe). A scanning electron microscope (SEM) was used to observe the morphology of collagen fibrils on the demineralized dentin matrix in each group after pretreatment. The adhesives Prime & Bond NT (PB) (Dentsply De trey, Konstanz, Germany) or Single bond 2 (SB) (3M ESPE, St. Paul, MN, USA) was applied after pretreatments, and a confocal laser scanning microscope (CLSM) was used to evaluate the quality of resin tags. The degree of conversion (DC) of the adhesive was investigated by Fourier transform infrared spectroscopy (ATR-FTIR). The dentin was first bonded with resin and bathed in water at 37 °C for 24 h. Half of them were subjected to 10, 000 cycles in a thermocycler between 5 °C and 55 °C before a microshear bond strength (µSBS) test. The statistical methods were Analysis of Variance (ANOVA) and a Tukey post hoc test at α = 0.05.

Results

The µSBS was significantly affected by pretreatments (p < 0.001), adhesives (p < 0.001), and aging conditions (p < 0.001) as revealed by the three-way ANOVA. The EDCw, EDCw + EWB, and EDCe groups significantly increased the µSBS; the EDCw + EWB and EDCe groups produced the highest µSBS. In the EDC-containing groups, the SEM showed at the collagen fibrils in the dentin matrix formed a three-dimensional network structure in the tubules after cross-linking into sheets, and the hybrid layer formed thicker resin tags under a CLSM. In the EDC-containing groups, the CLSM observed an increase in the length of resin tags. PB showed a higher DC and bonding strength than SB, and the five pretreatment groups tested did not affect the DC of the two adhesives.

Conclusions

In etch-and-rinse bonding system, EDC combined with EWB pretreatment can improve the quality of the hybrid layer and enhance the mechanical properties of demineralized dentin matrix. Pretreatment with EDC-ethanol solution may be a new clinically friendly option for enhancing dentin bonding durability.

Development of low-shrinkage dental adhesives via blending with spiroorthocarbonate expanding monomer and unsaturated epoxy resin monomer

Polymerization shrinkage is one of the main drawbacks of dental resin adhesives. In this study, spiroorthocarbonate expanding monomer 3,9-diethyl-3,9-dimethylol -1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU) and unsaturated epoxy resin monomer Diallyl bisphenol A diglycidyl ether (DBDE) were synthesized and utilized as anti-shrinkage-coupling additive of methacrylate-based adhesives. Polymerization process and physicochemical properties including double bond conversion, polymerization shrinkage, compatibility, mechanical performance, thermal stability, contact angle, shear bond strength and cytotoxicity were characterized. Results indicated that adhesives containing anti-shrinkage-coupling additive had reduced volume shrinkage, improved compatibility and enhanced shear bond strength. When the amount of additive was 20 wt%, the volume shrinkage was decreased by 45.8% (4.17 ± 0.32%) and the shear bond strength was increased by 49.6% (19.64 ± 0.99 MPa). The results also showed that the use of additive had no adversely affect on double bond conversion and cytotoxicity. Therefore, novel low-shrinkage resin adhesives were prepared via blending with spiroorthocarbonate expanding monomer and unsaturated epoxy resin monomer.

The effects of amalgam contamination and different surface modifications on microleakage of dentin bonded to bulk fill composite when using different adhesive protocols

BACKGROUND

To evaluate the effect of amalgam contamination, different surface treatments, and adhesive protocols on dentin microleakage to bulk-fill composite resin material.

METHODS

Forty teeth were fixed in (polyvinyl siloxane) PVS molds, and the Class II cavities were placed on mesial and distal aspects. Thirty teeth were restored by amalgam and thermocycled to 10,000 cycles (5 and 55 °C, 30-s dwell time). The rest were restored with Filtek one Bulk Fill composite without amalgam predecessor. Samples were divided into: G1 (dentin pretreated with 2% chlorhexidine gluconate), G2 (0.5 mm of dentin was removed), G3 (no surface modification), and G4 (control, where composite was bonded to sound dentin without amalgam predecessor.). Single Bond Universal Adhesive system was used to bond the composite material, by using the etch-and-rinse protocol in the mesial cavity preparation and self-etch protocol in the distal. Specimens underwent thermocycling for 5000 cycles, then embedded in silver nitrate and sectioned for stereomicroscope examination. Descriptive statistics, Mann-Whitney U test, and Kruskal-Wallis test were used to analyze the results at p < 0.05.

RESULTS

The highest microleakage score values (4.00) were found in the G2, and G4 in etch-and-rinse protocol. While the lowest scores were found in G2 when using self-etching protocol (1.5). Lower microleakage values were associated with the chlorhexidine treatment group for both adhesive protocols. No significant differences were found between amalgam contaminated and non-contaminated groups.

CONCLUSIONS

Amalgam contamination did not affect microleakage. Self-etching adhesive protocol significantly reduced microleakage for all groups irrespective of the surface treatment. Chlorhexidine pretreatment improved microleakage for both adhesive protocols but had no significant effect.