Thermo Cycling Research Articles

The effect of different bonding systems on shear bond strength of repaired composite resin

The purpose of this study is to compare the shear bond strength of repaired composite resin with different bonding agents and evaluate the effect of bonding agents on composite repair strength. Forty composite specimens (Z-250) were prepared and aged for 1 week by thermo cycling between 5 and with a dwell time of 30s. After air abrasion with aluminum oxide, following different bonding agents were applied (n = 10); SB group: Scotchbond multipurpose adhesive (3 step Total-Etch system); XE group: Clearfil SE bond (2 step Self-Etch system); XP group: XP bond (2 step Total-Etch system); XE group: Xeno III (1 step Self-Etch system). After bonding procedure was completed, new composite resin (Z-250) was applied to the mold and cured. For control group. 10 specimens were prepared. Seven days after repair, shear bond strength was measured. Data was statistically analyzed using one-way ANOVA and Tukey's test (p S.D.) per group were as follows: SB group: 17.06; SE group: 19.10; XP group: 14.44; XE group: 13.57; Control Group: 19.40. No significant difference found in each group. Within the limit of this study, it was concluded that the different type of bonding system was not affect on the shear bond strength of repaired composite resin.

Effect of conditioning methods on the microtensile bond strength of phosphate monomer‐based cement on zirconia ceramic in dry and aged conditions

The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 x 5 x 4 mm(3)) of a glass-infiltrated zirconia-alumina ceramic (In-Ceram Zirconia Classic) were randomly divided into three surface treatment groups: ST1-Air-abrasion with 110-mum Al2O3 particles + silanization; ST2-Laboratory tribochemical silica coating method (110-microm Al2O3, 110-microm silica) (Rocatec) + silanization; ST3-Chairside tribochemical silica coating method (30-microm SiO(x)) (CoJet) + silanization. Each treated ceramic block was placed in its silicone mold with the treated surface exposed. The resin cement (Panavia F) was prepared and injected into the mold over the treated surface. Specimens were sectioned to achieve nontrimmed bar specimens (14 sp/block) that were randomly divided into two conditions: (a) Dry-microtensile test after sectioning; (b) Thermocycling (TC)-(6,000x, 5-55 degrees C) and water storage (150 days). Thus, six experimental groups were obtained (n = 50): Gr1-ST1 + dry; Gr2-ST1 + TC(;) Gr3-ST2 + dry; Gr4-ST2 + TC; Gr5-ST3 + dry; Gr6-ST3 + TC. After microtensile testing, the failure types were noted. ST2 (25.1 +/- 11) and ST3 (24.1 +/- 7.4) presented statistically higher bond strength (MPa) than that of ST1 (17.5 +/- 8) regardless of aging conditions (p < 0.0001). While Gr2 revealed the lowest results (13.3 +/- 6.4), the other groups (21.7 +/- 7.4-25. 9 +/- 9.1) showed statistically no significant differences (two-way ANOVA and Tukey's test, alpha = 0.05). The majority of the failures were mixed (82%) followed by adhesive failures (18%). Gr2 presented significantly higher incidence of ADHESIVE failures (54%) than those of other groups (p = 0.0001). Both laboratory and chairside silica coating plus silanization showed durable bond strength. After aging, air-abrasion with 110-microm Al(2)O(3) + silanization showed the largest decrease indicating that aging is fundamental for bond strength testing for acid-resistant zirconia ceramics in order to estimate their long-term performance in the mouth.

The change of temperature on the shear strength of permanent soft-liner on acrylic resin

The characteristics of dental material such as solubility and water resorption, the use of adhesive, storage condition or used as thermo cycling or elevated-temperature are factors that can effect bond strength. The purpose of this study was to investigate the change of temperature on the shear strength of permanent soft liner on acrylic resin. Twenty-four specimens were divided into 3 groups and immersed in water at: 5 °C, 37 °C and 55 °C. Autograph AG 10 TE Shimadzu was used to determine the shear strength. The statistical test (ANOVA and LSD); showed that there were significant differences between temperature groups. The shear strength of 37 °C was higher than the temperature of 5 °C and 55 °C.

Shear Bond Strengths of Different Substrates Bonded to Lithium Disilicate Ceramics

The aim of this study was to evaluate the shear bond strengths of pre- and untreated resin core materials to lithium disilicate ceramics. Bond strengths to dental hard tissues served as controls. Ceramic cubes (IPS-Empress II) were luted either with a one-step (Variolink II/Excite DSC) or multiple-step total etching bonding system (Tetric Flow/Syntac Classic) to ground surfaces of human enamel, dentin, and resin core materials (Clearfil Core, Multicore). Resin core materials were additionally pretreated with hydrofluoric acid (HF) or were silica-coated (CoJet System). Shear bond strengths were determined after 24-hour water storage (n=10) and thermocycling (TC) (n=10; 2000 cycles, 5-55 degrees C, 30 seconds). Bond strengths to enamel, dentin, and silica-coated composites were significantly higher compared to untreated and HF-pretreated composites (p<0.05; Tukey B). Indeed, silica coating of the composite resins significantly increased the bond strength to ceramics (p<0.05; Tukey B). Due to the lower bond strength values of ceramics to untreated composite resins (as compared to enamel and dentin), any indication for a resin core build-up prior to the preparation of a ceramic restoration should be considered carefully.

Inhibition of mineral loss at the enamel/sealant interface of fissures sealed with fluoride- and non-fluoride containing dental materials in vitro

Objective. In this in vitro study we evaluated the enamel mineral loss effect of fluoride-containing and non-fluoride-containing materials at different distances from the sealant margin, and verified the fluoride-releasing capability of these materials. Material and methods. Extracted molars were randomly assigned into nine groups (n=12): Concise (C), FluroShield (F), Helioseal Clear Chroma (H), Vitremer (V), Fuji II-LC (FII), Ketac Molar (KM), Fuji IX (FIX), Single Bond (SB), and Clearfil Protect Bond (CF). All groups were subjected to thermo and pH cycling. Enamel mineral loss was evaluated by cross-section micro-hardness analysis at distances: −100 µm, 0 µm, 100 µm, 200 µm. The mineral loss data were analyzed using a multi-factor ANOVA with split-plot design, and fluoride-released data were submitted to ANOVA and Tukey tests. Results. FIX demonstrated a lower mineral loss than C, F, and H, but did not differ from the SB, CF, V, FII, and KM groups, which also demonstrated no difference among them. C, F, H, and V presented the highest mineral loss, with no difference among them. V did not differ from the other groups (p>0.05). Regarding the different distances from the sealant margin, −100 µm presented the lowest mineral loss. FIX showed the highest fluoride release on the 7th and 14th days of evaluation, while CF showed high fluoride release only on the 7th day. Conclusion. Resin sealant did not prevent enamel mineral loss, contrary to glass-ionomer cement, which showed the highest capacity for fluoride release. It is not exclusively the presence of fluoride in a material's composition that indicates its capability to interfere with the development of enamel caries-like lesions.

Influence of color coordinates on the color changes after polymerization and thermocycling of dental resin composites

Color changes after polymerization and aging of dental resin composites are perceptible. If these color changes can be predicted by the shade of material before polymerization or clinical use, color matching of composites with teeth would be improved. The objectives were to measure the correlations among the color coordinates (CIE L∗, a∗ and b∗) of dental resin composites and the changes in color (Δ E∗ab) and color parameters (Δ L∗, Δ C∗ab, and Δ H∗ab) after polymerization (PO) and thermocycling (TC), and to determine whether the range of color coordinates influenced these correlations. Color of two resin composites (26 shades) was measured before and after PO, and after TC with a reflection spectrophotometer. Regression analyses were performed among the color coordinates and the changes in color and color parameters after PO and TC. After PO, Δ E∗ab was correlated with CIE L∗ value measured after PO, and CIE a∗ and b∗ values measured before PO (p < 0.01). After TC, Δ E∗ab was correlated with CIE b∗, a∗, and L∗ measured after PO (p < 0.01). Correlations among the color coordinates and the changes in color parameters after PO or TC varied, but were generally significant (p < 0.01). Multiple regression analyses showed that Δ E∗ab values after PO and TC were mainly influenced by CIE L∗ after PO (multiple r = 0.87 after PO and 0.58 after TC). Correlations were also influenced by the range of color coordinates. Within the limit of this study, shade of resin composites significantly influenced the changes in color and color coordinates after PO and TC. Light shades (high CIE L∗ shades measured after polymerization) showed small color changes after polymerization and thermocycling.

Comparative Study of InGaN/GaN Structures Grown by MOCVD Using Various Growth Sequences

In this work we report results of direct comparison of two sets of InGaN/GaN MQW structures grown with and without using of thermocycling (TC) by electroluminescence, photoluminescence and photoluminescence excitation study. For both sets of structures luminescence originates from localized centres, but the density of states differs for structures grown with and without TC. Light emitting diodes (LED) grown with use of TC show nearly two times higher efficiency than the structures with the same design grown without TC.

Effect of multi-step dentin bonding systems and resin-modified glass ionomer cement liner on marginal quality of dentin-bonded resin composite Class II restorations

The use of resin composites in the restoration of Class II cavities with gingival margins located in dentin is still controversial. The purpose of this in vitro study was to evaluate the effect of four state-of-the-art multi-step dentin-bonding systems (A. R. T. Bond, Syntac, OptiBond DC, Scotchbond Multipurpose) on marginal adaptation and microleakage of dentin-bonded composite Class II restorations. A total of 72 Class II cavities with gingival margins in dentin were prepared in extracted molars and filled with fine-hybrid composites using a three-sited light curing technique. In one half of the cavities the pulpal wall was lined with a resin-modified glass ionomer cement liner (RM-GIC), in the other half a total bonding technique was applied. A. R. T. Bond and Syntac were tested with selective enamel etching (SE) and total etching (TE). Marginal adaptation was evaluated in a scanning electron microscope before and after thermocycling (TC). Microleakage was determined by dye penetration. After TC the proportions of continuous margin in dentin ranged from 37% (Syntac/SE) to 91.2% (A. R. T. Bond/TE). Scotchbond Multipurpose exhibited the lowest degree of microleakage (0.22 mm). Marginal enamel fracture was the most prevalent marginal defect at the enamel margins (8.3-22.2%). The use of the RM-GIC had no beneficial effect on any of the marginal parameters, either in dentin or in enamel. It is concluded that low degrees of marginal gap formation and microleakage can be achieved in totally bonded composite Class II restorations when using state-of-the-art multi-step bonding systems in combination with a meticulous incremental filling technique.

Bonding of Fissure Sealant to Etched Demineralized Enamel (Lesions)

Different aspects of the acid-etching of enamel lesions and subsequent bonding of resins were studied, in particular the measurement of the mineral loss as a result of etching and the structure of (etched) lesions in comparison with sound enamel in relation to bonding of resins. The experiments were performed on artificial lesions produced in an acidified gelatine-gel system. During the etching of enamel lesions less calcium was removed as compared to corresponding sound controls. Nevertheless the thickness of the etch steps for the two types of specimens was about the same. This relatively high resistance of the lesions to acid etching is attributed to the high fluoride content of the lesions. The hardness of the lesions and the sound enamel controls was measured at 15 μm below the surface. These values in both cases showed a decrease with successive etchings. The scanning electron microscopic appearance of the lesions revealed that after 1-min acid etching the surface topography was similar to sound enamel, with a prism pattern apparently suitable for resin tag formation and adhesion. The sealing quality of a lesion by a resin, and the integrity of the resultant bond, was tested by subjecting the specimens to a regimen of thermocy cling between 4 and 75 °C. In all cases the etched lesion turned out to support a successful bond. The study demonstrates that enamel lesions are an acceptable and suitable substrate for resin adhesion provided the enamel surface has been acid-etched.