جستجوی مقالات مرتبط با کلیدواژه "porcelain" در نشریات گروه "پزشکی"

The clinical porcelain repair system is almost entirely dependent on the integrity of the bond between porcelain and composite resins.   The preferred manner of conditioning the fitting surface of the ceramic restoration is by etching with hydrofluoric acid followed by the application of a silane coupling agent and bonding resin to achieve a high bond strength. Hydrofluoric acid etching of silica-based ceramics produces insoluble silica-fluoride salts, which can interfere with the bond strength to the resins.

The aim of this study is to evaluate shear bond strength of composite resin to porcelain treated with phosphoric acid compared to ultrasonic cleaner and air-water spray following hydrofluoric acid etching.

66 porcelain disks (Super Porcelain EX3, Noritake) of 8 mm diameter and 3 mm thickness were fabricated and stored in distilled water for 10 days. Porcelain surfaces were abraded with number 023 football shaped bur, etched with 9.5% Hydrofluoric acid and rinsed with water.  The disks were randomly divided into 3 groups: Group 1:  without any additional treatment    Group 2: Etching with 35% phosphoric acid for 30 seconds followed by water spray rinse.    Group 3: Ultrasonic cleaning in distilled water for 5 minutes.Silane and porcelain bonding resin (Bisco Inc.) was applied on the bonding surface of porcelain disks, according to manufacturerchr('39')s instructions. The composite samples (AELITE All Purpose Body) of 4 mm diameter and 3 mm thickness were bonded to the porcelain disks following fixation of a plastic mold on the center of disks.Study samples were stored in distilled water in room temperature for 1 week. Shear bond strength of each specimen was determined using universal testing machine following thermocycling protocol. (1000 cycles between 5°C and 55°C) The fracture modes (adhesive, cohesive, mixed) were examined under scanning electron microscopy at ×25 magnification. Data were analyzed by one-way ANOVA, post hoc Tukey’s test and post-hoc Dunnettchr('39')s t-test.

For both group 2 (P=0.015) and 3 (P<0.0001) the mean bond strength were significantly different from group 1. The bond strength values were significantly higher in group3 compared with group 2. (P=0.011) The highest and lowest bond strength was achieved in group 3 and 1, respectively.

According to increased bond strength between composite resin and ceramic following application of phosphoric acid and ultrasonic cleaning, they are both effective methods for post etching ceramic treatment, whereas regarding to the highest shear bond strength in group 3, ultrasonic cleaning is more recommended than phosphoric acid application.

This study was performed to compare the effect of Fractional CO2 laser or Q switched Nd:YAG laser of surface treatment on the shear bond strength of zirconia-porcelain interface.

Fractional CO2 laser at 30 W, 2 ms, time interval 1 ms, distance between spots 0.3 mm, and number of scans is (4) or Q switched Nd:YAG laser at 30 J/mm2 and 10 Hz were used to assess the shear bond strength of zirconia to porcelain. Pre-sintered zirconia specimens were divided into three groups (n = 10) according to the surface treatment technique used: (a) untreated (Control) group; (b) CO2 group; (c) Nd:YAG group. All samples were then sintered and veneered with porcelain according to the manufacturer’s instructions. Surface morphology was examined using a light microscope, the surface roughness test was done by the atomic force microscope (AFM), and the shear bond strength (SBS) test was done by a universal testing machine. After debonding following shear bond test, zirconia surfaces were examined under a light microscope to determine their fracture mode.

The Results of this study showed that the lowest SBS was recorded in the control group, and the highest SBS recorded in the Fractional CO2 group, followed by the Q switched Nd:YAG laser group, as well as an increase in surface roughness and change in the morphology and mode of failure in the experimental groups .

This study shows that Fractional CO2 laser and Q switched Nd:YAG laser treatments significantly increase the bond strength than untreated zirconia

Considering the increase in demand for orthodontic treatment in adults, bracket bond to restored teeth is a clinical challenge. This study sought to compare the shear bond strength (SBS) of orthodontic brackets to feldspathic porcelain using universal adhesive and conventional adhesive with and without silane application.

In this in vitro study Fifty‑six feldspathic porcelain discs were roughened by bur, and 9.6% hydrofluoric acid was used for surface preparation. Samples were divided into the following four groups (n = 14): Group 1: universal adhesive, Group 2: universal adhesive/silane, Group 3: conventional adhesive, and Group 4: conventional adhesive/silane. Mandibular central incisor brackets were bonded, and SBS was measured by Instron® machine. To assess the mode of failure, adhesive remnant index (ARI) score was determined. The data were analyzed using SPSS software and two‑way ANOVA, Bonferroni test, and Kruskal–Wallis test (P < 0.05 considered significant).

The highest SBS was noted in the universal adhesive/silane group (12.7 MP) followed by conventional adhesive/silane (11.9 MP), conventional adhesive without silane (7.6 MP), and universal adhesive without silane (4.4 MP). In the absence of silane, the conventional adhesive yielded significantly higher SBS than universal adhesive (P = 0.03). In the presence of silane, the two adhesives showed SBS values significantly higher than the values obtained when silane was not applied, while the two adhesives were not significantly different in terms of SBS in the presence of silane (P = 0.53). Based on ARI score, there were statistically significant differences between Groups 1 and 4 (P = 0.00) and Groups 2 and 4 (P = 0.023).

Based on the current results, SBS of bracket to porcelain mainly depends on the use of silane rather than the type of adhesive. Both universal and conventional adhesives yield significantly higher SBS in the presence of silane compared to that in the absence of silane.

In this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers.

Part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. The teeth were imbedded in autopolimerize acrylic resin. Cross section was preformed through the midline of the incisal, middle and cervical one-third of the labial surface of the teeth. The samples were observed under reflected stereomicroscope and the thickness of enamel was recorded. Part II, the effect of different types of preparation on dentin exposure was evaluated. Thirty maxillary central incisor teeth were randomly divided into two groups: A: Knife-edge preparation. B: Chamfer preparation.All samples were embedded in autopolimerize acrylic resin using a silicon mold. The samples were cut through the midline of the teeth. The surface of the samples were polished and enamel and dentin were observed under the stereomicroscope.

Data were analyzed by ANOVA-one way test. The results of this study showed that the least enamel thickness in the central incisor was 345 and in lateral incisor is 235 μ this thickness is related to the one-third labial cervical area. Maximum thickness in maxillary central and lateral incisors in the one-third labial incisal surface was 1260 μ and 1220μ, respectively. In the second part of the study, the tendency of dentinal exposure was shown with the chamfer preparation, but no dentinal exposure was found in the knife-edge preparation. The differences between groups were significant (p<0.05).

The knowledge of enamel thickness in different part of labial surface is very important. The thickness of enamel in the gingival area does not permit a chamfer preparation. The knife edge preparation is preferable in gingival area.