The aim of this study was to investigate the bond strength and adhesion of commercially available polydimethylsiloxane denture liner (Molloplast-B) to alumina-abraded or lased heat-cured polymethyl methacrylate denture base resin. The effect of laser irradiation on denture base resin by a surface analyzer and scanning-electron microscopy (SEM) was also determined. Laser-treated specimens demonstrated statistically significantly higher surface roughness values compared to alumina-abraded and untreated (control-group) specimens (p < 0.05). There were no statistically significant differences in surface roughness between alumina-abraded and control specimens. In the tensile debonding test, no statistically significant differences were found among the treatment modalities tested (alumina abraded, lased, and control) (p > 0.05). Molloplast-B applied to alumina-abraded polymethyl methacrylate resin surface recorded the highest mean tensile bond strength. Laser-treated specimens produced the next highest mean tensile bond strength, and untreated polymethyl methacrylate resin surface recorded the lowest tensile bond strength. Laser irradiation produced significant surface texture changes of the denture base material. However, this mechanical surface preparation of denture base before application of a resilient liner did not improve the adhesion between denture base and soft lining material.
The biomechanical behavior of implant thread plays an important role on stresses at implant-bone interface. Information about the effect of different thread profiles upon the bone stresses is limited. The purpose of this study was to evaluate the effects of different implant thread designs on stress distribution characteristics at supporting structures. In this study, three-dimensional (3D) finite element (FE) stress-analysis method was used. Four types of 3D mathematical models simulating four different thread-form configurations for a solid screw implant was prepared with supporting bone structure. V-thread (1), buttress (2), reverse buttress (3), and square thread designs were simulated. A 100-N static axial occlusal load was applied to occlusal surface of abutment to calculate the stress distributions. Solidworks/Cosmosworks structural analysis programs were used for FE modeling/analysis. The analysis of the von Mises stress values revealed that maximum stress concentrations were located at loading areas of implant abutments and cervical cortical bone regions for all models. Stress concentration at cortical bone (18.3 MPa) was higher than spongious bone (13.3 MPa), and concentration of first thread (18 MPa) was higher than other threads (13.3 MPa). It was seen that, while the von Mises stress distribution patterns at different implant thread models were similar, the concentration of compressive stresses were different. The present study showed that the use of different thread form designs did not affect the von Mises concentration at supporting bone structure. However, the compressive stress concentrations differ by various thread profiles.
This study aimed to evaluate the surface changes caused in zirconia by different surface treatments and the influence of the surface treatment and cement selection on bonding to zirconia under aging. Sintered zirconia specimens were divided into five groups (n = 31) based on the surface treatment, namely, control, air abrasion, silica coating, laser and air abrasion + laser. After surface treatment, surface roughness and microscope analyses were performed on one specimen of each group. Composite cylinders were then bonded to conditioned ceramics using RelyX U100 (RXU), Clearfil Esthetic Cement (CEC) and Panavia F (PF) (n = 10). After 24 h, the bonded specimens were subjected to thermal cycling (6,000 times), and then, a shear bond strength test was conducted. The roughness values were analysed using Kruskal-Wallis and Mann-Whitney U tests, and the bond strengths were analysed by two-way analysis of variance and Duncan's test. The relationship between the roughness and the bond strength was determined by Spearman's correlation analysis. Specimens subjected to surface treatments were rougher than the control specimen (p < 0.000). However, there were no significant differences between the air abrasion and air abrasion + laser groups and the silica coating and laser groups. Specimens treated with laser showed lower bond strengths irrespective of the resin cement used. CEC and/or PF showed higher bond strengths than RXU for each surface treatment group. No significant relationship was observed between the roughness and the bond strength. The results of this study showed that all the surface treatments, except for laser irradiation, were suitable for treating zirconia ceramics. Cement selection was found to be more important than surface treatment, and phosphate monomer-containing cements were suitable for cementing zirconia.
The purpose of this study was to investigate the surface morphology and roughness of zirconia after different surface treatments. Eighty sintered zirconia specimens were divided into four groups (n = 20) according to the surface treatments received: no treatment, erbium:yttrium-aluminum-garnet (Er:YAG) laser irradiation (400 mJ, 10 Hz, 4 W, 100 MPS, distance: 1 mm), tribochemical silica coating with 30 μm aluminum oxide (Al(2)O(3)) modified by silica, and air abrasion with 110 μm Al(2)O(3) particles. After the surface treatments, the surface roughness (Ra in μm) of the specimens was evaluated using a surface texture measuring instrument. Surface morphology of a specimen from each group was evaluated with atomic force microscope (AFM) and scanning electron microscope (SEM) analyses. The surface roughness values were statistically analyzed by the Kruskal-Wallis and Mann-Whitney U tests (p = 0.05). All of the surface treatments produced rougher surfaces than the control group (p < 0.005). While there were no significant differences between the surface roughness of laser and silica groups (p > 0.05). SEM and AFM analyses revealed changes in surface topography after surface treatments, especially in the laser group with the formation of rare pits and in the silica and air abrasion groups with the formation of microretentive grooves. According to the results of the statistical and microscopic analyses, all of the surface treatments can be used for roughening zirconia prior to cementation; however, air abrasion is the most effective surface treatment to obtain micromechanical retention.
The aim of this study was to determine the effect of sandblasting and electrical discharge machining (EDM) on cast and machined titanium surfaces and titanium-porcelain adhesion. Twenty machined titanium specimens were prepared by manufacturer (groups 1 and 2). Thirty specimens were prepared with autopolymerizing acrylic resin. Twenty of these specimens (groups 3 and 4) were cast with commercially pure titanium and the alpha-case layer was removed. For control group (group 5), 10 specimens were cast by using NiCr alloy. Groups 2 and 4 were subjected to EDM while groups 1, 3, and 5 were subjected to sandblasting. Surface examinations were made by using a scanning electron microscope (SEM). A low-fusing porcelain was fused on the titanium surfaces, whereas NiCr specimens were covered using a conventional porcelain. Titanium-porcelain adhesion was characterized by a 3-point bending test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests. Metal-porcelain interfaces were characterized by SEM. The bond strength of control group was higher than that of the titanium-porcelain system. There was no significant difference between cast and machined titanium groups (p > 0.05). There was no significant difference between EDM and sandblasting processes (p > 0.05). The use of EDM as surface treatment did not improve titanium-porcelain adhesion compared with sandblasting.
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