SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Dental materials journal

141

The accuracy of prostheses affects clinical success and is, in turn, affected by the accuracy of the scanner and CAD programs. Thus, their accuracy is important. The first aim of this study was to evaluate the accuracy of an intraoral scanner with active triangulation (Cerec Omnicam), an intraoral scanner with a confocal laser (3Shape Trios), and an extraoral scanner with active triangulation (D810). The second aim of this study was to compare the accuracy of the digital crowns designed with two different scanner/CAD combinations. The accuracy of the intraoral scanners and extraoral scanner was clinically acceptable. Marginal and internal fit of the digital crowns fabricated using the intraoral scanner and CAD programs were inferior to those fabricated using the extraoral scanner and CAD programs.

Concepts: Affect, Computer-aided design, Design, Clinical death, Scanners

2

The current study evaluated the effects of autoclave polymerization both with and without glass fiber (GF) reinforcement on the surface roughness and hardness of acrylic denture base material. Ninety disc specimens (30×2.5 mm) were prepared from Vertex resin and divided according to polymerization techniques into a water bath, short and long autoclave polymerization groups. Tested groups were divided into three subgroups according to the GF concentration (0, 2.5, and 5 wt%). Profilometer and Vickers hardness tests were performed to measure surface roughness and hardness. ANOVA and Tukey-Kramer multiple comparison tests analyzed the results, and p≤0.05 was considered statistically significant. Autoclave polymerization significantly decreased the surface roughness and increased the hardness of acrylic resin without GF reinforcement (p<0.05). However, 5 wt% GF addition significantly increased surface roughness and decreased hardness of the autoclave polymerized denture base resin (p<0.05). Surface properties of Polymethyl methacrylate (PMMA) denture base material improved with autoclave polymerization and negatively affected with GFs addition.

2

The present in vitro study sought to determine the effects of myrrh-containing solutions on common suture materials used in periodontal surgery. Three commonly used suture materials (silk, polyglactin 910, polytetrafluoroethylene) were immersed in four thermostatically controlled experimental media to simulate daily oral rinsing activity, namely -artificial saliva, normal saline solution with 0.2% Commiphora myrrh, full-concentration (100%) Commiphora myrrh oil, and a myrrh-containing commercial mouthwash. Tensile strength was measured at the end of each day using an Instron tensile testing machine. Silk sutures were susceptible to tensile strength loss when exposed to 0.2% myrrh solution once daily for 5 days. Myrrh-containing commercial mouthwash had no effect on tensile strength, but all three suture materials lost tensile strength when exposed to 100% myrrh oil. For patients that routinely use myrrh mouthwashes postoperatively, findings of this study suggested that silk sutures might not be the optimal material choice.

Concepts: In vitro, Materials science, Tensile strength, Surgical suture, Lactated Ringer's solution, Saline, Myrrh

0

The aim of this study was to evaluate how alumina-blasting pressure affects the bond strength of CAD/CAM resin blocks (CRBs) to bovine dentin using two different types of resin cements. CRB slices were divided into three groups by alumina-blasting pressure, namely, untreated and 0.1 MPa and 0.2 MPa, and further divided into three subgroups by combination of CRBs surface treatment and types of cement: Scotchbond Universal and RelyX ultimate (RXB), Scotchbond Universal and RelyX unicem2 (U2B), ceramic primer and RelyX unicem2 (U2C). The CRB slices were then cemented to bovine dentin, microtensile bond strength test was performed and evaluated. Regardless of the alumina-blasting pressure, RXB group have the highest µTBS and bond strength tends to increase with increasing alumina-blasting pressure. Alumina-blasting to CRB surface by at an appropriate pressure and use of conventional resin cement were required to obtain strong adhesion with the tooth structure.

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We investigated three bulk fill composites (Mat1, Mat2, Mat3) cured by two polywave (Poly1, Poly2) and one monowave (Mono) lamps. We used infrared spectroscopy, nanoindentation and atomic force microscopy to assess degree of conversion (DC), stiffness, and roughness after polishing, respectively. Mat2 exhibited the highest DC with Poly1 and second highest with Mono, however was the less stiff. Both Mat1 and Mat3 showed highest DC with Poly2, while Poly1 scored better than Mono. Mat3 scored better than Mat1 and was the third highest when cured with Poly2. For each composite cured by different lamps the stiffness ranked same as the DC. However, roughness did not correlate with hardness. Absolute stiffness value depends on composite formulation. Polywave lamps work better than monowave but not in all cases, as Mat2 showed higher DC with Mono than with Poly2. However, all lamps guarantee a DC≥50% but Mono for Mat1.

0

The purpose of this study was to formulate and evaluate an adhesive resin with tantalum oxide. Ta2O5 was evaluated by scanning electron microscopy and laser diffraction. The adhesive was formulated with methacrylate monomers and photoinitiators. Ta2O5 was added into the adhesive at 1, 2, 5 and 10 wt%. One group remained without filler (control group). Ta2O5 distribution, radiopacity (n=5), degree of conversion (DC) (n=3), softening in solvent (n=5) and ultimate tensile strength (UTS) (n=10) were evaluated. Data were analyzed by one-way ANOVA and Tukey’s test (α=0.05). Spherical nanometric Ta2O5 was arranged in 3.35 µm particles. The groups over 5 wt% presented higher radiopacity (p<0.05). The DC ranged from 61.78 (±1.19)% to 67.35 (±1.40)%, with statistical difference from control group over 5 wt% addition (p<0.05). There was no difference in softening in solvent (p>0.05) and UTS (p>0.05). Tantalum oxide is a promising alternative for adhesive formulation and it could be further tested for biomimetic remineralization.

0

The effects of contamination and cleaning methods on bonding of self-adhesive resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (Zpex Smile) specimens were divided into the following four groups: control (con), contaminated with saliva and cleaned with tap water (HS), cleaned with Ivoclean (IC), and cleaned with Multi Etchant (ME). The pretreated specimens were bonded using three self-adhesive resin cements, and tensile bond strengths were measured using a universal testing machine at a crosshead speed of 2 mm/min. Con and IC groups showed significantly higher bond strength than those of HS and ME groups. Separately, the surface chemical composition of the groups was determined using X-ray photoelectron spectroscopy (XPS). XPS revealed that the N/Zr ratio increased in the HS group but decreased in the IC and ME groups. Cleaning agents can improve the adverse effect of saliva contamination on zirconia, but this effect varies depending on the product.

0

The aim of this study was to evaluate the transmittance of visible light (VL) (λ: 400-700 nm) and blue light (BL) (λ: 360-540 nm) through six CAD/CAM zirconia blanks (ZiB) in comparison to a lithium disilicate ceramic (LS2). Disks of the zirconia materials Bruxzir (BX), Cercon (CE), Lava Frame (LF), Lava Plus (LP), Prettau (PT), Zenostar (ZS) and LS2 (EM) were manufactured and the transmittance was measured in a spectrophotometer. ZS, followed by CE, PT, LP, LF, and BX showed the lowest transmittance of VL and BL. The highest transmittance was shown by EM. The transmittance of BL was lower than that of VL in all groups. EM ceramics showed higher transmittance than all zirconia materials and the thickness of zirconia materials influenced the transmittance values. Knowledge about VL and BL transmittance would help clinicians to individually tailor the selection of material to the specific indication and to make the right choice regarding the luting procedure and light curing duration.

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The objective of the present study was to assess hard and soft tissue around dental implants made of three different materials with microgrooves on the collar surface. Microgrooved implants were inserted in the mandibles of five male beagles. Implants were made of three kinds of material; titanium (Ti), yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and ceria partially stabilized zirconia/alumina nanocomposite (Ce-TZP/Al2O3). The animals were euthanatized at three months after implantation, and harvested tissue was analyzed by means of histology. All kinds of implant were osseointegrated, and there were no significant differences in any histomorphometric parameters among the three groups of microgrooved implants made of different materials. Within the limitations of this study, implants with microgrooves integrated into the surrounding bone tissue, without statistically significant differences among the three tested materials, Ti, Y-TZP, and Ce-TZP/Al2O3.

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This study evaluated surface gloss, roughness and color change of six current flowable composites after simulated toothbrushing, including four traditional flowable composites (i.e. GrandioSO Flow, Arabesk Flow, Kerr Revolution Formula 2 and Gradia Direct LoFlo), one self-adhering flowable composite (Kerr Vertise Flow) and one universal injectable composite (G-ænial Universal Flo). Forty-eight dimensionally standardized specimens (n=8/group) were made from six composites. Before and after 1 h toothbrushing simulation, surface gloss was measured with a glossmeter, and surface roughness was evaluated with a profilometer, and color was measured with a spectrophotometer. In this study, G-ænial Universal Flo, termed as universal injectable composite by the manufacturer, presented excellent surface properties after toothbrush abrasion; Gradia Direct LoFlo showed excellent color stablity after toothbrush abrasion; color alteration of composites caused by toothbrush abrasion was acceptable on the premise that 3.3∆E units were considered as acceptable threshold values.