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

138

The surface topography of implant fixture is an important factor affecting the osseointegration. We herein demonstrated the effects of surface microtopography of titanium disks on proliferation and differentiation of osteoblast-like cells isolated from rat calvariae. Titanium disks with machine surface (MS), rough surface (R1) and rough surface combined with small cavities (R2) were used in an in vitro culture system. Rough surfaces (R1 and R2 disks) induced stronger osteoblast proliferation and differentiation (BGP and sclerostin mRNA expressions and calcium content) than the smooth surface (MS disk). Furthermore, surface microtopography of R2 disk, which was rough with small cavities, more strongly induced cell proliferation and mineralized bone matrix production than R1 disk. Our results suggest that surface microtopography influences osteoblast proliferation and differentiation. R2 disk, which is rough with small cavities, may be used in implant fixtures to increase osseointegration.

Concepts: DNA, Bone, Cell nucleus, Gene expression, Dental implant, Surface, Osseointegration, Differential geometry

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.

1

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

Telescopic crowns made from zirconia/alumina can be manufactured using computer-aided design/computer-aided manufacturing systems. For their successful clinical use, a suitable retentive force must be maintained over an extended period. However, it is unclear how retentive force and secondary crown settling change after repeated crown insertion and removal. The aim of the present study was to investigate the changes in retentive force and secondary crown settling of telescopic crowns made from zirconia/alumina. Primary crowns with tapers of 2° and 4° were used. Repeated insertion and removal tests were performed for 10,000 cycles at a cyclic load of 50 N. The loads applied when measuring retentive force and settling were 50 and 100 N. The number of insertions and removals had a significant effect on retentive force and settling at both loads (p<0.01). Taper also had a significant effect on retentive force and settling at both loads (p<0.01).

0

Computer-aided design/computer-aided manufacturing (CAD/CAM) materials were submitted to thermocycling, to identify changes in mechanical behavior. Four CAD/CAM materials were divided in four subordinate groups (n=9): (1) dry out for 7 days, (2) distilled water at 37oC for 7 days, (3) 60,000 thermocycles, and (4) 120,000 thermocycles. Following thermocycling, samples were submitted to three-point bending test. Two-way ANOVA and post-hoc Tukey’s test were performed (α=0.05). The IPS e.max CAD had a flexural strength of 396±75 MPa and flexural modulus of 84±11 GPa, followed by Vita Enamic with values of 153±17 MPa and 28±5 GPa respectively. The flexural strength recorded for Lava Ultimate was 149±28 MPa and the flexural modulus was 12±3 GPa. Vitablocs Mark II had the lowest flexural strength values (125±10 MPa) and a flexural modulus of 49±15 GPa. Although polymer-based materials have similar mechanical properties compared to ceramics, they are affected by thermo cycling conditions.

0

We investigated the effects of the weekly application of pastes containing a surface reaction-type pre-reacted glass-ionomer (S-PRG) filler on dentin remineralization. Human dentin blocks were demineralized and polished using pastes containing S-PRG filler (0, 5, and 30%), and then immersed in remineralizing solution for 1 month. Nanoindentation testing was carried out during the immersion period, and the dentin surfaces were examined using scanning electron microscopy. A nano-hydroxyapatite-containing paste was used for comparison. Immersion in demineralization solution had a marked negative effect on the mechanical properties in all specimens. The mechanical properties of specimens polished with S-PRG filler-containing pastes recovered significantly after immersion in remineralization solution for 1 month compared with the other specimens. After remineralization, the open dentinal tubules were filled with a remineralization layer in specimens polished with S-PRG filler-containing and nano-hydroxyapatite-containing pastes. S-PRG filler-containing pastes can aid dentin remineralization.

0

This study examined the surface roughness (Ra) and shear bond strength (SBS) of Yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic after airborne particle abrasion at different pressures and particle sizes, pre- and post-sintering. Ninety specimens, prepared from Y-TZP ceramic blocks (Vita In-Ceram YZ, Vita Zahnfabrik), were divided into nine subgroups: control, and 50 and 110 µm Al2O3 airborne particle abrasion at 3 and 4 bar pressure, before and after sintering, respectively. According to the sintering order, before and after surface treatments, Ra values were measured using a profilometer. SBS to Y-TZP was assessed after thermocycling, using self-adhesive resin cement (Rely X U200, 3M ESPE). Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) were performed on one specimen per group. All surface-treated samples were rougher than the controls. ABS50-4 (50 µm Al2O3 airborne particle abrasion at 4 bar pressure before sintering), ABS110-3, and ABS110-4 showed the highest Ra values, among all cohorts. The controls displayed lower SBS values than the treated groups (p<0.05), which had statistically similar results to each other. Airborne particle abrasion of pre-sintered Y-TZP, followed by sintering, increased the tetragonal structure contents.

0

To improve initial osteoblast adhesion and subsequent osseointegration, TiO2 nanotubes layer was constructed on the titanium (Ti) surface by anodic oxidation (AO), with an additional hydroxyapatite (HA) coating to form the AO/HA surface. Tests on in vitro cellular activity displayed that the AO surface, especially the AO/HA surface, promoted initial adhesion, proliferation and differentiation of osteoblast cells. The modified AO and AO/HA surfaces further presented an up-regulated gene expression of osteogenic and adhesion markers collagen type 1 (COL), osteopontin (OPN), osteocalcin (OCN) and vinculin. In addition, in vivo experiments with a rat model demonstrated that the AO surface, particularly the AO/HA surface, achieved earlier osseointegration and a superior bone bonding ability compared with Ti. Our study shed light on a synergistic role played by nanotopography and HA in promoting osteoblast adhesion, proliferation, differentiation and osseointegration, thus suggesting a promising method for better modifying the implant surface.

0

To clarify the influence of translucent tetragonal zirconia polycrystals (TZP) on wear properties of esthetic dental materials, twobody wear test was performed using translucent TZP as abrader specimen, and bovine tooth enamel (BTE), two resin composites including hybrid filler (CRH) and nano filler (CRN), two glass ceramics including leucite reinforced feldspar porcelain (POR) and lithium disilicate (LDC), or translucent TZP as substrate specimen. After the wear test, wear volume were determined from substrate specimen and surface roughness were measured from abrader specimen. In addition, Vickers hardness was measured and surface morphologies were observed after wear test using a scanning electron microscope. The wear volume of the esthetic dental material against translucent TZP was greater in glass ceramics (POR, LDC), smaller in resin composite (CRH, CRN) and BTE, and no wear in translucent TZP. Microstructures of the esthetic dental material may play a crucial role for wear behavior against translucent TZP.