Ramin Atash

Color variation induced by abutments in the superior anterior maxilla: an in vitro study in the pig gingiva

PURPOSE The aim of this work is to evaluate different types of materials used for making implant abutments, by means of an in vitro study and a review of the literature, in order to identify the indications for a better choice of an implant-supported restoration in the anterior section. MATERIALS AND METHODS 5 implant abutments were tested in a random order in the superior anterior maxilla of pig gingiva (n = 8): titanium dioxide (Nobel Biocare); zirconium dioxide, Standard BO shade (Nobel Biocare, Kloten, Switzerland); zirconium dioxide, Light BI shade (Nobel Biocare); zirconium dioxide, Intense A 3.5 shade (Nobel Biocare); and aluminium oxide. Each abutment was tested for 2 mm and 3 mm thickness. To determine color variation, VITA Easyshade Advance spectrophotometer (Vita Zahnfabrik, Bad Sackingen, Germany) was used. RESULTS Results showed that the color variation induced by the abutment would be affected by the abutment material and gingival thickness, when the gingival thickness is 2 mm. All materials except zirconium dioxide (Standard shade) caused a visible change of color. Then, as the thickness of the gingiva increased to 3 mm, the color variation was attenuated in a significant manner and became invisible for all types of abutments, except those made of aluminium oxide. CONCLUSION Zirconium dioxide is the material causing the lowest color variation at 2 mm and at 3 mm, whereas aluminium oxide causes the highest color variation no matter the thickness.

A Comparative Study of Microleakage on Dental Surfaces Bonded with Three Self-Etch Adhesive Systems Treated with the Er:YAG Laser and Bur

Aim. This study sought to compare the microleakage of three adhesive systems in the context of Erbium-YAG laser and diamond bur cavity procedures. Cavities were restored with composite resin. Materials and Methods. Standardized Class V cavities were performed in 72 extracted human teeth by means of diamond burs or Er-YAG laser. The samples were randomly divided into six groups of 12, testing three adhesive systems (Clearfil s3 Bond Plus, Xeno® Select, and Futurabond U) for each method used. Cavities were restored with composite resin before thermocycling (methylene blue 2%, 24 h). The slices were prepared using a microtome. Optical microscope photography was employed to measure the penetration. Results. No statistically significant differences in microleakage were found in the use of bur or laser, nor between adhesive systems. Only statistically significant values were observed comparing enamel with cervical walls (p < 0.001). Conclusion. It can be concluded that the Er:YAG laser is as efficient as diamond bur concerning microleakage values in adhesive restoration procedures, thus constituting an alternative tool for tooth preparation.

Comparison between shear forces applied on the overlay-dental tissue interface using different bonding techniques: An in vitro study

Aim: The aim of this study was to compare the adhesion of glass-ceramic overlays to tooth structure, under the effect of shear forces, using different bonding systems. Materials and Methods: Thirty healthy lower third molars were selected and randomly allocated into three groups (n = 10). Group 1: overlays bonded to tooth structure using Panavia V5 with immediate dentin sealing (IDS); Group 2: overlays bonded using Panavia V5 without IDS; and Group 3: overlays bonded using heated composite combined with a bonding agent with IDS. All the restorations were made of glass-ceramic (Suprinity, Vita). The restored teeth were then stored in distilled water for 7 days and at room temperature. Shear forces were applied using a universal testing machine. Load and displacement were recorded at intervals of 0.1 s. A statistical analysis was used to compare the groups. Results: The mean resistance to fractures ± standard deviation obtained for the Groups 1, 2, and 3 was, respectively, 15.7440 ± 2.13, 12.0750 ± 1.41, and 8.33364 ± 2.85 MPa. The analysis of variance was highly significant (P < 0.001) allowing us to reject the null hypothesis of equality between the three groups. Comparisons between pairs also provided significant results. Conclusion: Bonding using Panavia V5 with IDS showed a better resistance to shear forces when compared to other bonding techniques. The application of IDS increased the adhesion.

Influence of the amount of tooth surface preparation on the shear bond strength of zirconia cantilever single-retainer resin-bonded fixed partial denture

PURPOSE Conventional resin-bonded fixed partial dentures (RBFPDs) are usually made with a two-retainer design. Unlike conventional RBFPDs, cantilever resin-bonded fixed partial dentures (Cantilever RBFPDs) are, for their part, made with a single-retainer design. The aim of this study was to compare the effect of tooth surface preparation on the bond strength of zirconia cantilever single-retainer RBFPDs. The objective is to evaluate the shear bond strength of these single-retainer RBFPDs bonded on 3 different amount of tooth surface preparation. MATERIALS AND METHODS Thirty extracted bovine incisors were categorized to 3 groups (n=10), with different amounts of tooth surface preparations. Teeth were restored with single-retainer RBFPDs with different retainer surfaces: large retainer of 32 mm2; medium retainer of 22 mm2; no retainer and only a proximal connecting box of 12 mm2. All RBFPDs were made of zirconia and were bonded using an adhesive system without adhesive capacity. Shear forces were applied to these restorations until debonding. RESULTS Mean shear bond strength values for the groups I, II, and II were 2.39±0.53 MPa, 3.13±0.69 MPa, and 5.40±0.96 MPa, respectively. Statistical analyses were performed using a one-way ANOVA test with Bonferroni post-hoc test, at a significance level of 0.001. Failure modes were observed and showed a 100% adhesive fracture. CONCLUSION It can be concluded that the preparation of large tooth surface preparation might be irrelevant. For zirconia single-retainer RBFPD, only the preparation of a proximal connecting box seems to be a reliable and minimally invasive approach. The differences are statistically significant.

In Vitro Study of Bonding Strength of Zirconia on Dentin Using Different Adhesive Systems

PURPOSE To compare different dental bonding systems that are currently available on the market. MATERIALS AND METHODS A total of 100 extracted, intact third molars were coated in resin, cut, and divided into 10 groups of 10 molars each. Molars were bonded to zirconia blocks with a different bonding system per group. Resistance to shear forces was tested using a universal traction machine. Samples were observed under scanning electron microscopy (SEM) to determine the type of fracture. RESULTS Statistical analyses showed a significant influence of adhesive on the zirconia-dentin assemblys resistance to shear forces. SEM analysis showed mainly adhesive and mixed fractures. CONCLUSION Dentin bonding systems without adhesive capability showed better results than self-etch systems.

Effect of Coloring of Zirconia Framework and Ceramic Veneer on Adhesion of Interfacial Surfaces Determined Using Three-Point Flexural Bonding Strength: An In Vitro Study

PURPOSE The aim of this study was to investigate the effect of coloring on the interfacial surface adhesion between a zirconia framework and ceramic veneer using three-point flexural bonding strength. MATERIALS AND METHODS A total of 40 zirconia bars (Zirlux ST1; DE Healthcare) were cut and divided into two groups of 20 (Groups 1 and 2). The two groups were then further split and divided into four groups of 10 each (Groups 1a, 1b, 2a, and 2b). Groups 1a and 1b tested adhesion of uncolored zirconia and two different shades of ceramic veneer, and Groups 2a and 2b tested adhesion of zirconia colored with two different coloring liquids and one shade of ceramic veneer. RESULTS Some coloring liquids used to color zirconia can significantly affect the bond strength between zirconia and the veneer, whereas ceramic veneer shades do not influence adhesion. CONCLUSION Bonding strength between zirconia framework and ceramic veneer is affected by the coloring of the zirconia.

Comparison of resistance to fracture between three types of permanent restorations subjected to shear force: An in vitro study

Introduction: Our studys objective was to compare resistance to fracture between endocrown and conventional post and core restorations when subjected to shear force. Materials and Methods: Thirty human mandibular premolars were extracted for orthodontic reasons, endodontically treated, and restored using three different methods: endocrown, glass fiber post and composite resin core, and metal post. All the crowns were made from IPS e.max ceramic. Shear forces were applied to these restorations using a test machine until breakage. Load and displacement were recorded every 0.1 s. Results: No significant difference was observed in resistance to fracture between glass fiber post and metal post. No relationship between the displacement of prosthetic dental system and type of material used was uncovered and by comparing the type of fracture with the restoration material used. However, a greater number of favorable fractures were observed in the glass fiber group whereas most of the fractures in the endocrown and metal post groups were unfavorable. Conclusion: Endocrown displays better resistance to fracture compared to conventional post and core restorations. In addition, endocrown did not show more displacement or cause more unfavorable fractures than the conventional restorations. This restoration may represent a reliable alternative for restoring a damaged, endodontically treated tooth.

Adaptation of zirconia crowns created by conventional versus optical impression: in vitro study

PURPOSE The aim of this study was to compare the precision of optical impression (Trios, 3Shape) versus that of conventional impression (Imprint IV, 3M-ESPE) with three different margins (shoulder, chamfer, and knife-edge) on Frasaco teeth. MATERIALS AND METHODS The sample comprised of 60 zirconia half-crowns, divided into six groups according to the type of impression and margin. Scanning electron microscopy enabled us to analyze the gap between the zirconia crowns and the Frasaco teeth, using ImageJ software, based on eight reproducible and standardized measuring points. RESULTS No statistically significant difference was found between conventional impressions and optical impressions, except for two of the eight points. A statistically significant difference was observed between the three margin types; the chamfer and knife-edge finishing lines appeared to offer better adaptation results than the shoulder margin. CONCLUSION Zirconia crowns created from optical impression and those created from conventional impression present similar adaptation. While offering identical results, the former have many advantages. In view of our findings, we believe the chamfer margin should be favored.

In Vitro Study of the Sealing Ability of Cements for Zirconia Restorations.

PURPOSE The micropercolation testing of dental materials is currently used to evaluate the sealing ability. The aim of the present study is to compare the sealing ability of distinct assembling materials for zirconium oxide peripheric crowns. MATERIALS AND METHODS One hundred teeth were prepared to be thermocycled after being distributed at random in 10 groups each containing 10 specimens (group 1: Fuji One; group 2: Fuji Plus; group 3: Variolink II; group 4: RelyX Ultimate; group 5: Multilink; group 6: Panavia F2.0; group 7: Bifix QM; group 8: RelyX Unicem 2; group 9: Maxcem Elite; group 10: Bifix SE). RESULTS RelyX Unicem 2 and RelyX Ultimate yielded high imperviousness percentages. The sealing ability in the vestibular area and lingual area is indeed best in the presence of these two materials. Our results show no difference whether the chamfer is situated in the enamel or in the dentin. CONCLUSION A zirconium crown should be preferably cemented with a glass-ionomer cement modified by addition of resin material.

In vitro evaluation of microleakage under orthodontic brackets bonded with different adhesive systems

Objective: Adhesives systems have a drawback when utilized for bonding orthodontic brackets: they shrink during photopolymerization creating microleakage. The aim of this study was to assess the stability of different orthodontic adhesives around brackets and enamel. Materials and Methods: Sixty noncarious mandibular premolars extracted for orthodontic reasons were randomly divided into six groups of adhesives used for bonding brackets to dental enamel: NeoBond® Light Cure Adhesive Kit, Transbond™ Plus Self-Etching, Victory V-Slot APC PLUS® + Transbond™ MIP, Rely-A-Bond® Kit, Light Cure Orthodontic Adhesive Kit (OptiBond®), and Transbond™ MIP. Following bonding, all teeth underwent 2500 cycles of thermal cycling in baths ranging from 5°C to 55°C before being immersed in 2% methylene blue for 24 h. All samples were examined under a binocular microscope to assess the degree of microleakage at the “bracket-adhesive” and “adhesive-enamel” interfaces in the gingival and occlusal regions of the bracket. Results: A significant difference was found at the “occlusal bracket-adhesive” interface. The highest microleakage values were found in the occlusal region, although no significant. Microleakage was observed in all groups. Conclusion: Group 2 had the highest microleakage values whereas Group 6 had the lowest values.