Biomedical subjects

Alvaro H Cury

Publications and source records attributed to Alvaro H Cury.

6 recordsLinked to original sources

PubMed2007

Effect of oxygen inhibition on composite repair strength over time.

The study was aimed at examining whether an oxygen inhibition layer is required for bonding a repairing to a pre-existing composite, and to determine the time required for free radicals within a composite substrate to decay to the extent that the composite repair strength drops significantly. Ten slabs of Gradia Direct Anterior (GC Corp.) were divided into (1) control group: an interfacial oxygen inhibition layer was created by applying and light-curing two layers of bonding resin (D/E Resin, Bisco) to the slabs surface in atmospheric air; (2) experimental group: the absence of an interfacial oxygen inhibition layer was obtained by light-curing the second bonding resin layer in a nitrogen atmosphere. After 1 and 2 h, 1, 14, and 30 days of air storage, a composite repair was layered over the bonding resin. Microtensile bond strengths were measured and statistically analyzed. The curing atmosphere was not a significant factor for bond strength (p = 0.82), and time and curing atmosphere-time interaction were significant (p < 0.001). The 30 day-strengths were the lowest (p < 0.05). An oxygen-inhibited layer is not initially required for bonding to resin composite, and it takes more than 14 days before the bond strength between a pre-existing and a fresh composite drops.

Biomechanical Phenomena↗

PubMed2006

The effect of immediate versus delayed cementation on the retention of different types of fiber post in canals obturated using a eugenol sealer.

Post can be placed immediately after the completion of the endodontic procedure or at a later stage after setting of the sealer. In this in vitro study, post space preparation and post cementation were performed immediately (group 1), 24 h (group 2), and 7 days (group 3) after root filling. A control group with no root canal obturation was included (group 4). Each group was further divided into three subgroups, according to the post type and to the materials used for luting the post. A push-out test was performed to evaluate post-root canal dentin interfacial strength. Differences among experimental groups were analyzed with two-way ANOVA and the Tukey test. Significant differences (p < 0.05) in interfacial strengths were observed for the factors post cementation interval and post type. Clinicians should be careful in performing immediate cementation of fiber posts, as delayed cementation shows higher post-dentin interfacial strengths irrespective of the post type.

Analysis of Variance↗

PubMed2006

Effect of hygroscopic expansion on the push-out resistance of glass ionomer-based cements used for the luting of glass fiber posts.

This study examined the contribution of hygroscopic expansion of glass-ionomer (GIC) and resin modified glass-ionomer (RMGIC) luting cements to the push-out resistance of fiber posts. Glass fiber posts were luted to post spaces using different cements. Experimental specimens were stored in water, while control specimens were desiccated and stored in mineral oil to eliminate water from intraradicular dentinal tubules and/or the external environment that could have contributed to hygroscopic expansion of the cements. Thin slice push-out tests revealed no difference in retention strengths of resin composite cements that were stored in water or oil. Conversely, GIC and RMGIC cements exhibited increased retention strengths after water sorption. As unfavorable cavity geometry is taxing to dentin bond integrity in root canals, a strategy that relies on increasing the frictional resistance to post dislodgement via delayed hygroscopic expansion of glass-ionomer based materials may be a more pragmatic approach to fiber post retention.

Acrylic Resins↗

PubMed2006

Microtensile bond strength and interfacial properties of self-etching and self-adhesive resin cements used to lute composite onlays under different seating forces.

PURPOSE: To evaluate strength and morphology of the interface created on enamel and dentin by Panavia F 2.0 (P, Kuraray), RelyX Unicem (RU, 3M ESPE), and Maxcem (M, Sybron-Kerr), applied under two standardized clinically realistic seating pressures. MATERIALS AND METHODS: Composite overlays (Paradigm MZ100, 3M ESPE) were luted on flat enamel or dentin surfaces of 48 extracted molars. During the initial 5-min self-curing period, a pressure of either 20 or 40 g/mm(2) was maintained on the overlay. Curing was completed by light irradiation from the top of the overlay for 20 s. Microtensile sticks and specimens for SEM observations were obtained from the luted teeth. Bond strength data from enamel and dentin (MPa) were analyzed with separate two-way ANOVAs in order to assess the effect of cement type, luting pressure, and their interactions. Tukey's test was used for post-hoc comparisons (alpha = 0.05). RESULTS: The bond strengths (MPa) to dentin were: P 20 g/mm(2) 7.5 +/- 3.7, 40 g/mm(2) 10.9 +/- 4.5; RU 20 g/mm(2) 6.8 +/- 2.6, 40 g/mm(2) 14.5 +/- 5.3; M 20 g/mm(2) 4.1 +/- 1.8, 40 g/mm(2) 5.2 +/- 1.6. The bond strengths (MPa) to enamel were: P 20 g/mm(2) 25.2 +/- 9.0, 40 g/mm(2) 30.7 +/- 8.6; RU 20 g/mm(2) 10.7 +/- 4.9, 40 g/mm(2) 11.1 +/- 5; M 20 g/mm(2) 7.3 +/- 3.1, 40 g/mm(2) 7.9 +/- .2. Cement type, luting pressure, and the interaction of these two factors had significant influences on dentin bond strength, with RU and P outperforming M. RU and P significantly benefited from the increase in luting pressure. In enamel, the type of cement was a significant factor for adhesion, with P yielding the highest and M the lowest strength. The measured bond strengths corresponded with the morphological results. CONCLUSION: Interfacial strength and adaptation of self-etching and self-adhesive dual-curing cements are enhanced if a seating force greater than finger pressure is maintained throughout the initial self-curing period.

Acid Etching, Dental↗

PubMed2005

Post-surface conditioning improves interfacial adhesion in post/core restorations.

OBJECTIVES: To verify the influence of different etching procedures of the post-surface on microtensile bond strength values between fiber posts and composite core materials. METHODS: 60 DT Light Posts were divided into 10 subgroups using five different chemical surface treatments and two composite materials to build-up the abutment. Chemical surface treatments including etching with potassium permanganate; treatment with 10% hydrogen peroxide; treatment with 21% sodium ethoxide; etching with potassium permanganate and 10 vol.% HCl; silanization (control group) were performed on the post's surface. The build-up was performed using (A) Core Paste XP (Dent Mat) and (B) Unifil Flow (GC). Two samples of each group were randomly selected to investigate the morphologic aspect of the post/core interface with a scanning electron microscope (SEM). The remaining specimens were cut so as to obtain microtensile sticks that were loaded in tension at a cross-head speed of 1mm/min until failure. The statistical analysis was performed using two-way ANOVA and the Tukey's test for post-hoc comparisons (alpha=0.05). RESULTS: SEM examination showed an interpenetrating adhesion network between the treated fiber post-surface and the composite material in all the groups tested. The results achieved with potassium permanganate had a significant influence on microtensile interfacial bond strength values with both the tested materials. Post-superficial treatments enhanced the bond strength particularly of Core Paste XP. SIGNIFICANCE: Etching procedures showed a similar effect on the post-surface and enhanced the adhesion of composite core build-ups as a result of micromechanical and chemical retention.

Composite Resins↗

PubMed2005

The influence of the cutting speed on bond strength and integrity of microtensile specimens.

OBJECTIVES: To verify the influence of cutting speed during microtensile specimen preparation, on bond strength values and on the sample microscopic integrity of a single-bottle adhesive system to enamel and dentin. METHODS: Thirty sound human third molars were restored with light-cured Excite and Tetric Ceram according to manufacturers' instructions, being half in ground enamel [E], and half in flat dentin [D]. After 24 h storage in distilled water at 37 degrees C, the restored teeth were sectioned in x and y-axes under different cutting speed: 100, 200 or 400 RPM, obtaining stick shaped specimens with cross-sectional area of 1.0 mm(2). Five specimens from each experimental group were randomly selected before being loaded for SEM analysis, while the remaining samples were subjected to the microtensile bond strength test. Because the variance of dentin specimens was significantly higher than the variance of enamel samples, analysis of the influence of the cutting speed was performed separately, by substrate. RESULTS: The mean values in MPa were calculated including/excluding premature failures: E1: 24.67/27.31(a); E2: 24.03/25.81(a); E4: 19.06/21.52(b); D1: 35.80/36.33(A); D2: 35.84/36.65(A); D4: 37.78/38.50(A). In the SEM analysis, better integrity of the dentin specimens was observed when compared to the enamel samples, for which the integrity was greater in the lower cutting speed groups. SIGNIFICANCE: It can be concluded that the cutting speed is an important factor that should be considered, mainly when enamel is involved, since it may affect the bond strength results and the integrity of the specimens.

Acid Etching, Dental↗