Oxygen-inhibited Layer Research Articles

Effect of Aqueous Storage on Original and Repair Bond Strength and Residual Monomer Release of Fiberreinforced Composites.

To evaluate the effects of aqueous storage on shear bond strength (SBS) and monomer release of fiberreinforced composites (FRCs). Four unidirectional FRCs were tested, including one semi-interpenetrating polymer network (IPN) (ES, everStick) and three cross-linked polymer (CLP) FRCs (GT, GrandTec; TF, TenderFiber; DP, Dentapreg). The SBS of samples of original resin to fresh FRC with an intact oxygen inhibition layer (n = 30/group) and repair resin to FRC after surface treatment (n = 30/group) was evaluated after 6 and 12 months of storage in artificial saliva. Monomer release of polymerized resin-coated and uncoated FRCs was detected by high-performance liquid chromatography after immersion for 1 h, 1 day, and 7 days. After 6 months, a significant decrease in SBS was seen with ES-repair (p < 0.0001). After 12 months, significant decreases were seen with ES-original (p < 0.0001), ES-repair (p < 0.0001), and TF-repair (p = 0.0003). A significant reduction was also found for GT-original (p = 0.0254) and GT-repair (p = 0.0176). At 6 and 12 months, GT showed the highest SBS values, with DP-repair being statistically similar to GT at 12 months. For UDMA and bis- GMA, the greatest amounts of release were seen in uncoated specimens, followed by flowable resin-coated and viscous resin-coated specimens. Matrix composition, interfacial bonding, and resin coverage seem to account for differences in the aging behavior of FRCs. The semi-IPN material is likely to suffer most from the challenging oral conditions. CLP FRCs might be more stable over the long term. Coverage of FRCs with viscous resin is highly recommended to reduce residual monomer release.

Study of the oxygen-inhibited layer of three universal dental adhesives

Study of the oxygen-inhibited layer of three universal dental adhesives

Influence of an oxygen-inhibited layer on enamel bonding of dental adhesive systems: surface free-energy perspectives.

The influence of an oxygen-inhibited layer (OIL) on the shear bond strength (SBS) to enamel and surface free-energy (SFE) of adhesive systems was investigated. The adhesive systems tested were Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to bovine enamel surfaces to determine the SBS, with and without an OIL, of adhesives. The SFE of cured adhesives with and without an OIL were determined by measuring the contact angles of three test liquids. There were no significant differences in the mean SBS of SM and CS specimens with or without an OIL; however, the mean SBS of SU specimens with an OIL was significantly higher than that of SU specimens without an OIL. For all three systems, the mean total SFE (γS), polarity force (γSp), and hydrogen bonding force (γSh) values of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The results of this study indicate that the presence of an OIL promotes higher SBS of a single-step self-etch adhesive system, but not of a three-step or a two-step self-etch primer system. The SFE values of cured adhesives with an OIL were significantly higher than those without an OIL. The SFE characteristics of the OIL of adhesives differed depending on the type of adhesive.

Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 μm) for water-sprayed Silorane and greatest (22.9 μm) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected.

Does immediate dentin sealing influence the polymerization of impression materials?

Objectives:The objective of the following study is to evaluate the interaction between the resin materials used in immediate dentin sealing (IDS) techniques and impression materials with two different techniques to eliminate the oxygen-inhibition layer.Materials and Methods:The occlusal dentin surface of 35 human molars was exposed. The teeth were used in two Groups: Group 1 – Impression with Express XT; Group 2 – Impression with Impregum. Groups 1 and 2 were divided into 14 subgroups: Groups 1a and 2a – Control groups; 1b and 2b – IDS with Clearfil SE Bond (CSE); 1c and 2c – IDS with CSE + additional polymerization with glycerin jelly; 1d and 2d – IDS with CSE + alcohol; 1e and 2e – IDS with CSE and Protect Liner F (PLF); 1f and 2f – IDS with CSE and PLF + additional polymerization with glycerin jelly; and 1g and 2g – IDS with CSE and PLF + alcohol. Five teeth were used in each experimental group, and the tooth surface was photographed using a digital camera.Results:Small quantity of unpolymerized impression material remained attached to the CSE or to the PLF in Groups 1b and 1e. Groups 1c and 1d prevented the interaction. Small quantity of polymerized impression material remained attached to the CSE or to the PLF for Groups 2b and 2e. The same interaction was observed for Groups 2c and 2d. For Groups 2c and 2f, no interactions were observed.Conclusion:Resin materials interacted with impression materials. The application of glycerin jelly and alcohol prevented the interaction of CSE with Express XT and PLF with Impregum; however, these treatments were not completely effective in preventing the interaction of CSE with Impregum and PLF with Express XT.

Incremental layer shear bond strength of low-shrinkage resin composites under different bonding conditions.

The purpose of this study was to determine the incremental shear bond strength of a silorane-based composite (Filtek Silorane) repaired with silorane or a methacrylate-based composite (Filtek Z250) under various aging conditions. Also, the incremental bond strength of the silorane-based composite was compared with that of another low-shrinkage methacrylate-based composite (Aelite LS Posterior) under fresh and aged conditions, with and without the use of an adhesive resin between successive layers. The two brands of low-shrinkage composites were compared with a microhybrid, Filtek Z250, which served as the control. Substrate discs were fabricated and second layers were adhered to them immediately, after two weeks of aging, or after four weeks of aging and with and without an adhesive resin. Shear bond strengths were measured and failure modes were evaluated. The incremental bond strength of silorane to the silorane-based composite was not significantly different from that of the methacrylate-based composite. However, repairing a silorane-based composite with a methacrylate-based composite significantly reduced the bond strength. Aelite showed a lower incremental bond strength than Z250 and silorane, but the use of an adhesive significantly improved the bond strength. The absence of an oxygen-inhibited layer did not affect the bond strength of the consecutive layers of the silorane-based composite.

Original and repair bond strength of fiber-reinforced composites in vitro

ObjectiveA great benefit of FRC technology is that, in case of minor failure events, restorations can be repaired or reinserted. However, various FRC materials are available, that differ in matrix composition and fiber pre-treatment. The aim of this investigation was, therefore, to evaluate original and repair bond strength of FRC materials. MethodsFive fully pre-impregnated, unidirectional FRCs were selected, one semi-interpenetrating polymer network FRC and four cross-linked-polymer FRCs. The primary endpoint was the evaluation of shear bond strength (SBS) between FRC and composite resin, which was performed by a universal testing machine. For each FRC specimens were divided into control (original SBS, resin to fresh FRC with oxygen inhibition layer (OIL), n=30) and test groups (repair SBS, resin to FRC after removal of OIL and adhesive infiltration, n=30). ResultsThe cross-linked-polymer FRC GrandTec® (12.4±5.4MPa) yielded the highest control SBS, followed by the semi-interpenetrating polymer network FRC (everStick®, 9.2±3.5MPa). With everStick®, repair led to a significant increase in the test SBS (14.6±5.8MPa, p=0.01). SignificanceControl SBS was best with GrandTec® indicating that the material is superior in direct clinical application. Test SBS was significantly increased with everStick® which points at potential reparability and advantages in semi-direct or indirect fabrication of fiber-reinforced fixed partial dentures.

Effect of oxygen inhibition in two-step self-etch systems on surface free energy and dentin bond strength with a chemically cured resin composite.

We compared the surface free energies and dentin bond strengths of two-step self-etch systems with and without an oxygen-inhibited layer. The adhesives were applied to self-etching primer-treated dentin surfaces of bovine incisors, after which the teeth were light-irradiated and the oxygen-inhibited layer was left intact or removed with ethanol. We determined surface free energies (γS) and their components by measuring the contact angles of three test liquids placed on the cured adhesives. We also measured the dentin bond strengths of chemically cured resin composite to the adhesives, with and without the oxygen-inhibited layer. For all surfaces, the estimated surface tension component, γS(LW), was relatively constant. The Lewis base (γS(-)) component decreased significantly when the oxygen-inhibited layer was removed, whereas the Lewis acid (γS(+)) component slightly increased. The dentin bond strengths of the two-step self-etch systems did not significantly differ in relation to the presence of the oxygen-inhibited layer. Although the surface free energy of the adhesive was affected by the presence of the oxygen-inhibited layer, no changes in dentin bond strength were detected.

Influência de diferentes matrizes oclusais na fotopolimerização de uma resina composta: análise de microdureza Knoop

ObjectiveTo evaluate the influence of three occlusal matrix materials in the light curing effectiveness of a resin composite. Furthermore, we intend to determine if the application of these materials could prevent the oxygen-inhibited layer of the composite surface. MethodsOne-hundred composite (GrandioSO, VOCO) specimens, 2mm thick, were light-cured (20seconds) with a LED curing device (800 mW/cm2) through the study materials. The specimens were divided into ten groups (n=10) according to the placed material [no interposed material, mylar strip, Registrado Clear (VOCO), Memosil-2 (Heraeus Kulzer) e Bite-perf (BITEPERF Dental Products)] and thickness / light-cure tip distance (1 and 2mm). After 24hours, Knoop microhardness tests were performed at top and bottom surfaces. The data was analyzed with a two-way MANOVA followed by the Tukey post-hoc test. Statistical testing was performed at a 0.05 level of significance. ResultsThe light-cure tip distance did not show statistical differences (p≥0.05). The mylar strip groups showed the highest (p<0.05) microhardness values on top surface. The Bite-perf groups showed lower hardness values comparing to the mylar strip groups, but higher than the other groups (p<0.05). On the bottom surface, the Bite-perf group presented the lowest values (p<0.05). There were no statistically significant differences between the other groups (p≥0.05). ConclusionsThe Bite-perf was the only material that influenced the resin composite depth of cure and the only that seems to prevent the oxygen-inhibited layer.

Influence of oxygen‐inhibited layer on dentin bond strength of chemical‐cured resin composite

This study evaluated the influence of an oxygen-inhibited layer on the surface free energies of three single-step self-etch adhesives and on the bond strength of chemical-cured resin. Adhesives were applied to bovine dentin and light irradiated, and the oxygen-inhibited layer was either retained or removed. Surface free energies were determined by measuring the contact angles of test liquids placed on the cured adhesives. Dentin bond strengths of chemical-cured resin with and without the oxygen-inhibited layer were measured. Ultrastructural observation of the restorative-dentin interface was made by scanning electron microscopy. For all surfaces, values of the estimated surface tension component, Lifshitz-Van der Waals force (γS(LW)), were relatively constant. Values for the Lewis acid (γS(+)) component increased slightly when the oxygen-inhibited layer was removed, whereas those of the Lewis base (γS(-)) component decreased significantly. The bond strength of the chemical-cured resin composite was significantly higher in specimens without an oxygen-inhibited layer (7.6-8.0 MPa) than in those with an oxygen-inhibited layer (4.8-5.2 MPa). Small gaps between adhesive and resin composite were found for the group with an oxygen-inhibited layer. These results indicate that the absence of an oxygen-inhibited layer in single-step self-etch adhesives promotes higher dentin bond strength of the chemical-cured resin.

Polymerization behavior within adhesive layer of one- and two-step self-etch adhesives: A micro-Raman spectroscopic study

This study investigated the polymerization behavior within the adhesive layer of one- and two-step self-etch adhesives at the dentincomposite interface. Dentin surfaces were applied with Clearfil S(3) Bond (TS), Clearfil S(3) Bond Plus (TSP) and Clearfil SE Bond (SE), and then placed with a light-curing resin composite. After water storage for 24 h, the bonded teeth were sectioned and polished perpendicular to the adhesive interface, and the degree of conversion (DC) of the adhesive layer between the dentin and composite were determined using micro-Raman analysis. For all the adhesives, the DCs of the adhesive layers significantly decreased near the adhesive-composite join (p<0.05). For the maximum DC value (Pmax) and the DC value at the adhesive-composite join (Pitf), TS was significantly lower than TSP and SE (p<0.05). The polymerization of oxygen-inhibited layer at the top of the adhesive could not reach maximum DC even after polymerization of the overlying resin composite.

Observation of oxygen inhibited layer of organic dental resin by confocal Raman-microscopy

AbstractThis study investigated degrees of conversion of oxygen inhibited layer (OIL) of organic dental resins for restoration using Confocal-Raman spectroscopy. The aim was to determine which laser is adapted to determine the degrees of conversion of OIL and to measure variations of thickness and degrees of conversion in OIL with respect to monomers proportions. Bis-GMA (bis-phenol A glycidyl dimethacrylate) and TEGDMA (triethylene glycol dimethacrylate) based resins with various ratio of an equimolecular mixture of camphorquinone/EDMAB (ethyl (4-dimethyl amino) benzoate) were studied with different lasers by confocal- Raman spectroscopy. Results show that this technique is adapted for the non destructive measurement of OIL. The Thickness of OIL is not correlated with the proportions of Bis-GMA and TEGDMA in the resin and was close to 3-4μm. Thickness of OIL is very thin without inorganic fillers (3 or 4 μm). Inorganic fillers might be responsible of greater OIL in composite resins.

Influence of oxygen inhibition on the surface free energy and enamel bond strength of self-etch adhesives

We compared the surface free energies and enamel bond strengths of single-step self-etch adhesives with and without an oxygen-inhibited layer. The adhesives were applied to the enamel surfaces of bovine incisors, light irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free energies and their components (γ(S)(LW), γ(S)(+), and γ(S)(-)) were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The enamel bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component γ(S)(LW) was relatively constant. The value of the γ(S)(+) component increased slightly when the oxygen-inhibited layer was removed, whereas that of the γ(S)(-) component decreased significantly. The enamel bond strengths of the self-etch adhesives were significantly lower in the specimens without an oxygen-inhibited layer. The oxygen-inhibited layer therefore appeared to promote higher enamel bond strength.

Influence of oxygen inhibition on the surface free-energy and dentin bond strength of self-etch adhesives

We compared the surface free-energies and dentin bond strengths of single-step self-etch adhesives with and without an oxygen-inhibited layer. The labial dentin surfaces of bovine mandibular incisors were wet ground with #600-grit silicon carbide paper. The adhesives were applied to the ground dentin, light-irradiated, and the oxygen-inhibited layer was either retained or removed with ethanol. The surface free-energies were determined by measuring the contact angles of three test liquids placed on the cured adhesives. The dentin bond strengths of specimens with and without the oxygen-inhibited layer were measured. For all surfaces, the value of the estimated surface tension component was relatively constant at 35.5-39.8 mJ m(-2) . The value of the , Lewis acid component increased slightly when the oxygen-inhibited layer was removed, whereas that of the , Lewis base component decreased significantly. The bond strengths of the self-etch adhesives were significantly lower in specimens without an oxygen-inhibited layer (13.2-13.6 MPa) than in those with an oxygen-inhibited layer (17.5-18.4 MPa). These results indicate that the presence of an oxygen-inhibited layer in single-step self-etch adhesives with advanced photoinitiators promotes higher dentin bond strength.

The effect of solvent evaporation of dentin adhesive on bonding efficacy

Objectives: The purpose of this study is to evaluate bonding efficacy by means of measuring the effect of remained solvent on Degree of conversion(DC) and and FE-SEM examination. Materials and Methods: Two 2-step total etching adhesives and two single-step self etching adhesives were used in this study. First, volume weight loss of 4 dentin adhesives were measured using weighting machine in process of time in normal conditions and calculate degree of evaporation (DE). Reaction/reference intensity ratio were measured using micro-Raman spectroscopy and calculate DC according to DE. Then 2 experimental groups were prepared according to air-drying methods (under, over) and control group was prepared to manufacturer's instruction. Total 12 groups were evaluated by means of micro tensile bond strength and FE-SEM examination. Results: Degree of evaporation (DE) was increased as time elapsed but different features were observed according to the kind of solvents. Acetone based adhesive showed higher DE than ethanol and butanol based adhesive. Degree of conversion (DC) was increased according to DE except for bond. In evaluation, bond strength was increased by additional air-drying. Large gaps and droplets were observed in acetone based adhesives by FE-SEM pictures. Conclusions: Additional air-drying is recommended for single-step self etching adhesive but careful consideration is required for 2-step total etching adhesive because of oxygen inhibition layer. Evaporation method is carefully chose and applied according to the solvent type.

Cytotoxicity and Degree of Conversion of Orthodontic Adhesives

To test the hypothesis that there is no difference in the cytotoxicity related to the modes of polymerization of five commercially available orthodontic bonding resins, with and without an oxygen-inhibited layer (OIL), and to evaluate the degree of conversion (DC) of these resins and correlate this to cytotoxicity. Five commercially available orthodontic bonding resins were tested for cytotoxicity and DC. Thirty-six disks of standardized dimensions, for each resin, were used for cytotoxicity assessment. Half of them were washed with 99% acetone to remove the OIL (washed resins), and the remaining disks were left intact (intact resins). Glass disks were used as a control. Vero cells were exposed to intact and washed resins on day 1. Cell viability was determined by tetrazolium bromide reduction assay 1, 3, and 6 days after exposure. The DC of the adhesive specimens of each resin, prepared with a procedure identical to the clinical bonding process, was assessed by Fourier transform infrared spectroscopy. Single-cured systems were comparatively less cytotoxic than dual-cured systems. With removal of the OIL, increased cell viability was noted only with two resins on all three days. Resins tested showed differences in DC. A positive correlation was demonstrated by two resins. The hypothesis is rejected. Single-cured systems are superior to dual-cured systems in exhibiting comparatively less toxicity and higher DC. A significant positive correlation was not established between cytotoxicity and DC.

Interactions between impression materials and immediate dentin sealing

Immediate dentin sealing is a new strategy in which a dentin bonding agent is applied to freshly cut dentin and polymerized before making an impression. Interactions are suspected between the resin coating and the impression material. The purpose of this study was to identify possible interactions between 2 impression materials and resin-coated tooth surfaces using 2 different dentin bonding agents. Extracted molars (n=6) with flat midcoronal preparations underwent 1 of 4 procedures: control group, unsealed tooth surface/impression; IDS group, immediate dentin sealing (Optibond FL or Clearfil SE Bond)/impression; IDS/AB group, immediate dentin sealing/air blocking/impression; IDS/AB-P group, immediate dentin sealing/air blocking/pumicing/impression. All specimens underwent impressions (Impregum Soft or Extrude). Optical microscopy was used to detect unpolymerized and residual impression material on the bonded tooth surface. A substantial layer of unpolymerized resin (oxygen-inhibited layer) was found in the IDS group, which resulted in100% faulty impressions (unpolymerized impression material) for both adhesives and impression materials. Air blocking the resin coating (IDS/AB group) did not completely eliminate the oxygen-inhibited layer of Optibond FL and slightly altered the surface of SE Bond (wrinkles). Only SE Bond along with Extrude generated ideal impressions in group IDS/AB, while all other combinations of adhesive/impression material resulted in faulty impressions (unpolymerized impression material or adhesions). The IDS/AB-P group yielded ideal Extrude impressions but generated faulty Impregum impressions (adhesions) in more than 50% of the specimens. Immediate dentin sealing should be followed by air blocking and pumicing to generate ideal impressions with Extrude. Impregum is not recommended in combination with immediate dentin sealing.

Oxygen inhibition and incremental layer bond strengths of resin composites

Objectives When dentists light cure resin composite restorations in increments or after contouring the surface layer to shape with a hand instrument the surface layer is exposed to air during polymerization. The presence of an oxygen inhibited resin surface layer may impact on clinical performance. Conflicting data has been produced in vitro regarding this topic. Methods To shed further light on this subject the current investigation assessed the thickness of the oxygen inhibited layer (OIL) and subsequent interfacial bond strength at various times post-cure of an “initial increment” for a range of experimental and commercial resin composites. The latter included conventional methacrylate-based composites and a novel low shrink Silorane resin chemistry product. Results A decrease in composite viscosity brought about by an increase in diluent monomer content in the matrix for the experimental composite formulations led to increase in OIL thickness. The OIL surface layer thickness for the commercial methacrylate-based RBC specimens cured in air were 19.2 ± 6.3 and 13.8 ± 5.3 μm, respectively and 9.0 ± 6.6 μm for Silorane. No test material exhibited a measurable OIL thickness polymerized in the nitrogen atmosphere. Significance From the current findings it may be concluded that incremental bond strength is not wholly reliant on surface inhibition since no differences in bond strength following immediate placement were observed between air and nitrogen atmosphere for any experimental or commercial material. For large restorations requiring multiple increments which are placed on fresh material, the bond strength between successive layers of Silorane should be no different to conventional methacrylate materials. Repair and bonding to aged Silorane restorations may be more problematic as inferior incremental bond strengths ensued when addition was delayed.

Utilization of Occlusal Index and Layering Technique in Class I Silorane-based Composite Restorations

PURPOSE This article describes a technique that uses an occlusal index to restore teeth back to their original contour and anatomy with minimal finishing. A new type of ring-opening silorane composite reported to have less than 1% volumetric shrinkage was used in the restoration. For the silorane-based composite, there is no oxygen-inhibited layer to be polished away. The final composite layer is cured under pressure and further minimizes voids and gap formation. The technique can also be used on multiple posterior restorations under rubber dam isolation. Overall, if used properly, this technique helps the clinician produce superb anatomy and reduces time for posterior composite restorations.

Effect of surface condition and storage time on the repairability of temporary crown and fixed partial denture materials

Objectives The aim of the present study was to investigate which parameters (chemical nature, time after mixing, surface characteristics) might affect the repair strength of temporary crown and bridge materials (t-c&b). Methods Four different t-c&bs (Cool Temp Natural, Protemp 3 Garant, Structur Premium, Trim) were investigated using a shear-bond strength (SBS) setup. A cylinder (2 mm × 2.37 mm) of identical t-c&b ( n = 10) was bonded onto a specimen surface of either freshly set t-c&b (10 min after mixing) or onto specimens that were stored for 24 h (37 °C, distilled water) and 7 days (thermocycling ×5000, 5–55 °C = TC), respectively. The specimen surface was roughened with SiC paper (grit size 320) or left as it was (specimens stored for 10 min) prior to repair to retain the oxygen-inhibition layer. In addition, mono-block specimens were fabricated as control. The thickness of the oxygen-inhibition layer and the surface morphology was determined. Statistical analysis was carried out with an ANOVA followed by parametric tests ( p = 0.05). Results SBS values ranged from 10 to 40 MPa. Trim showed lowest SBS values for most storage conditions. Material, surface characteristics and time after mixing significantly affected the SBS (ANOVA p < 0.001). TC significantly reduced the SBS ( p < 0.05) for all t-c&bs except for Trim ( p > 0.05). Conclusions In case of monomethacrylates, storage and surface condition do not affect the repair strength. In contrast, the repair quality of dimethacrylates greatly depends on the material. In any case, roughening the surface is recommended, even if an oxygen-inhibition layer is present.