Investigating the Effect of Different Surface Treatments on Vickers Hardness and Flexural Strength of Zirconium and Lithium Disilicate Ceramics.

PURPOSE: To investigate the effect of different surface treatments on Vickers hardness and flexural strength of zirconia and lithium disilicate ceramics. MATERIALS AND METHODS: 50 zirconia and 50 lithium disilicate ceramic specimens were used. After identifying one group as the control, grinding, sandblasting, CoJet, and Er:YAG laser were applied on the surface of specimens (n = 10). After applying Vickers hardness test to specimens, flexural strength test was performed. The data were analyzed with two-way ANOVA and Duncan's multiple comparisons tests. RESULTS: There were statistically significant differences found between surface treatment groups in terms of Vickers hardness of zirconia and lithium disilicate ceramics (p < 0.001), but there were no statistically significant differences found between surface treatment groups in terms of flexural strength (p > 0.05). CONCLUSIONS: Surface treatments could affect the hardness of ceramics. Therefore, was zirconia found to be harder and more durable than lithium disilicate ceramics.

An In Vitro Evaluation of the Effect of Various Adhesives and Surface Treatments on Bond Strength of Resin Cement to Polyetheretherketone.

PURPOSE: To investigate the effect of various surface pretreatments and adhesive systems on bond strength of resin cement to polyetheretherketone (PEEK). MATERIALS AND METHODS: 360 PEEK specimens were divided into 4 groups to receive the following pretreatments (n = 90): no pretreatment, sandblasting, silica coating and Er:YAG laser. Surface roughness (SR) and scanning electron microscopy (SEM) evaluations were conducted after mechanical pretreatments for topographical surface evaluations. After the pretreatments, each group was divided into 3 subgroups (n = 30) according to the adhesive system used: no adhesive system, Visio.link, and Signum PEEK Bond. Resin cement was applied, and specimens underwent 5000 thermocycles (5-55°C) before shear bond strength (SBS) test. One-way ANOVA and Tukey test were used to analyze the SR data; 2-way ANOVA and Fisher's LSD test were used to analyze the SBS data at the confidence interval of 95% (α = 0.05). RESULTS: The sandblasting group demonstrated the highest SR values (p < 0.05). No significant differences in SR values were identified among silica coating, laser, and control groups (p ˃ 0.05). Conditioning with Visio.link after sandblasting group exhibited the highest SBS values (p < 0.05). No significant differences in SBS values were found between laser and control group (p ˃ 0.05). Conditioned groups presented higher SBS values than unconditioned groups (p < 0.05). Between the two adhesive systems, Visio.link demonstrated statistically significant higher SBS values than Signum PEEK Bond (p < 0.05). CONCLUSION: Silica coating and sandblasting were shown to provide superior pretreatment of PEEK surface. Laser pretreatments showed no effectiveness on bond strength of resin cement to PEEK. Adhesive systems improved the resin bonding to PEEK.

Effect of different bleaching agents on the surface roughness and color stability of feldspathic porcelain / Efeito de diferentes agentes de clareamento na rugosidade superficial e estabilidade de cor da porcelana feldspática

Objective: The aim of this study was to evaluate the effect of different bleaching agents on the surface roughness and color stability of feldspathic porcelain. Material and Methods: In this study, totally 40 discshaped Noritake and Ceramco 3 feldspathic porcelain and two bleaching agents (Opalescence Boost and Opalescence Pf) were used. Bleaching agents were exposed to specimens according to their protocol. Then, the surface roughness of the specimens was evaluated with profilometer and the color of the specimens was recorded by colorimeter. Statistical analysis of the data was performed with IBM SPSS Statistics 20. Results: The results showed that that there were statistically significant differences between the bleaching agents on the surface roughness of feldspathic porcelain (p0.05). Conclusion: The obtained data presented that the bleaching agents increased the surface roughness and not affect the color stability of the feldspathic porcelain. (AU)

Objetivo: O objetivo deste estudo foi avaliar o efeito de diferentes agentes clareadores sobre a rugosidade superficial e estabilidade de cor da porcelana feldspática. Material e Métodos: Neste estudo, foram utilizados 40 porcelanas feldspáticas Noritake e Ceramco 3, em forma de disco, e dois agentes clareadores (Opalescence Boost e Opalescence Pf). Os agentes clareadores foram expostos às amostras de acordo com seu protocolo. Em seguida, a rugosidade superficial dos corpos de prova foi avaliada com perfilômetro e a cor dos corpos de prova foi registrada por colorímetro. A análise estatística dos dados foi realizada com o IBM SPSS Statistics 20. Resultados: Os resultados mostraram que houveram diferenças estatisticamente significantes entre os agentes clareadores na rugosidade superficial da porcelana feldspática (p 0,05). Conclusão: Os dados obtidos mostraram que os agentes clareadores aumentaram a rugosidade superficial e não afetaram a estabilidade de cor da porcelana feldspática.(AU)

The effect of various polishing systems on surface roughness and phase transformation of monolithic zirconia.

PURPOSE: The purpose of this study was to evaluate and compare three polishing systems on the surface roughness and phase transformation of monolithic zirconia. MATERIALS AND METHODS: 100 disk shaped specimens (10 mm diameter, 3 mm thickness) were fabricated from monolithic zirconia blocks. 20 specimens were left as a control group and remaining specimens were grinded by diamond bur to simulate the occlusal adjustments. Grinded specimens were randomly divided into 4 groups: group G (no polishing), group M (Meisinger, zirconia polishing kit), group E (EVE Diacera, zirconia polishing kit), and group P (EVE Diapol, porcelain polishing kit). Surface roughness was measured with profilometer and surface topography was observed with SEM. XRD analysis was performed to investigate the phase transformation. Statistical analysis was performed with one-way ANOVA and Tukey's post hoc tests at a significance level of P=.05. RESULTS: All polishing groups showed a smoother surface than group G. Among 3 polishing systems, group M and group E exhibited a smoother surface than the group P. However, no significant differences were observed between group M and group E (P>.05). Grinding and polishing did not cause phase transformations in zirconia specimens. CONCLUSION: Zirconia polishing systems created a smoother surface on zirconia than the porcelain polishing system. Phase transformation did not occur during the polishing procedure.

Effect of polymerization cycles on flexural strengths and microhardness of different denture base materials.

The purpose of this study was to evaluate the effect of different polymerization cycles on the flexural strengths and microhardness of two denture base materials (Meliodent and Paladent). Heat-polymerized acrylic resin specimens (65.0 mm long×10.0 mm wide×2.5 mm in height) were prepared using different short and long polymerization cycles. After the specimens had been polymerized, they were stored in distilled water at 37±1°C for 24 h. Flexural strength test was performed at a cross-head speed of 5 mm/min and Vickers microhardness was measured. Data were analyzed with a 1-way analysis of variance followed by Tukey test, and Student t-test (α=0.05). The flexural strengths and microhardness were significantly different between Meliodent and Paladent (p<0.05). Significant differences were found among the polymerization cycles in terms of flexural strengths and microhardness (p<0.05). Polymerization with G cycle may be suggested for Meliodent and H cycle may be suggested for Paladent.

The effect of veneering on the marginal fit of CAD/CAM-generated, copy-milled, and cast metal copings.

OBJECTIVE: This in vitro study investigated the marginal fit of metal and zirconia copings before and after veneering on dies with shoulder/chamfer (s/c) finish lines. MATERIALS AND METHODS: Using CAD/CAM, ten (n = 10) each s/c zirconia (NZ) copings and ten (n = 10) each s/c metal (MM) copings were generated. As controls, ten (n = 10) each s/c zirconia copings were copy-milled (ZZ) and ten (n = 10) each s/c metal copings were cast (CC). The vertical marginal discrepancy of the copings was measured at 20 predefined spots of the circular shoulder and chamfer finish lines in microns (µm) before and after a first and a second veneering firing using a stereomicroscope at ×40 magnification. Data were statistically analyzed, and the comparisons of CAD/CAM-milled (NZ, MM), copy-milled (ZZ), and cast (CC) copings before and after veneering were made at a significance level of p < 0.05. RESULTS: Gap width at s/c finish lines of ZZ was (91 ± 11/100 ± 28) and increased significantly (109 ± 21/141 ± 18) after the first firing (ZZ1). NZ showed significantly smaller gaps than ZZ (36 ± 6/46 ± 12) and (NZ1) after the first firing (61 ± 16/71 ± 29). Gap widths of CC groups (36 ± 8/25 ± 4) were not significantly different from NZ but were significantly lower after the (CC1) first veneering firing (40 ± 8/42 ± 7). MM copings showed gap values similar to NZ. Second firings did not significantly increase gaps in all groups except ZZ2 of chamfer finish line. CONCLUSION: Veneering increased the marginal gap width of copings. CLINICAL RELEVANCE: Within the limits of this in vitro study, aesthetic ceramic veneering of CAD/CAM-generated copings caused a statistically significant but tolerable loss of marginal fit precision.

Investigation of the effects of storage time on the dimensional accuracy of impression materials using cone beam computed tomography.

PURPOSE: The storage conditions of impressions affect the dimensional accuracy of the impression materials. The aim of the study was to assess the effects of storage time on dimensional accuracy of five different impression materials by cone beam computed tomography (CBCT). MATERIALS AND METHODS: Polyether (Impregum), hydrocolloid (Hydrogum and Alginoplast), and silicone (Zetaflow and Honigum) impression materials were used for impressions taken from an acrylic master model. The impressions were poured and subjected to four different storage times: immediate use, and 1, 3, and 5 days of storage. Line 1 (between right and left first molar mesiobuccal cusp tips) and Line 2 (between right and left canine tips) were measured on a CBCT scanned model, and time dependent mean differences were analyzed by two-way univariate and Duncan's test (α=.05). RESULTS: For Line 1, the total mean difference of Impregum and Hydrogum were statistically different from Alginoplast (P<.05), while Zetaflow and Honigum had smaller discrepancies. Alginoplast resulted in more difference than the other impressions (P<.05). For Line 2, the total mean difference of Impregum was statistically different from the other impressions. Significant differences were observed in Line 1 and Line 2 for the different storage periods (P<.05). CONCLUSION: The dimensional accuracy of impression material is clinically acceptable if the impression material is stored in suitable conditions.

Effects of multiple firings on the microstructure of zirconia and veneering ceramics.

The aim of study was to evaluate the effects of multiple firings on the microstructures of zirconia and two ceramics. Vita VM9 (VMZ) and Cerabien ZR (C-Z) ceramics on a zirconia framework and zirconia without veneering ceramic (WO-Z) were evaluated. Firing methods included firing two, five, and ten times (n=10). The effects of multiple firings on the surface hardness of the materials were evaluated using a Vickers hardness (HV) tester. Data were analyzed by two-way ANOVA and Tukey's test (α=0.05). After firing five and ten times, the hardness of VM-Z and C-Z increased significantly (p<0.001). The HVs of the Cerabien ZR and Vita VM9 veneering ceramics were similar (p>0.05). In the XRD analysis, zirconia had similar tetragonal (t)-monoclinic (m) phase transformations of Y-TZP after the different firing times. Clinically, multiple firings did not affect the microstructure of zirconia, but the structures of the two ceramics were affected.

Influence of Tooth Preparation Design on Fitting Accuracy of CAD-CAM Based Restorations.

OBJECTIVE: The purpose of this study was to evaluate the marginal fit of different zirconia and metal frameworks and compare them with each other on different finish line configurations. MATERIALS AND METHODS: 20 stainless steel dies 10 with shoulder and 10 with chamfer finish line including 6 mm preparation height and 3 degree axial angle simulating a 6 degree total occlusal covergence of the prepared tooth were produced. After embedding the each group of die into the arch-shaped acrylic resin blocks, impressions were made using silicone based impression material and 120 casts were prepared subsequently. The dies were divided into six groups each having 20 specimens (10 with shoulder, 10 with chamfer finish line). Group CM consisted of Co-Cr produced by conventional casting procedure, group MM of Co-Cr prepared by metal milling, group LM of Co-Cr prepared by direct laser metal sinterization (DLMS), group ZZ of Zirkonzahn (Zirkonzahn GmbH, Gais, Italy), group LZ of Lava Zirconia (3 M ESPE Dental AG, Seefeld, Germany) and group DZ of DC-Zirkon (DCS Dental AG, Allschwil, Switzerland). Stereomicroscope were used to evaluate the marginal fit of frameworks and marginal gap values obtained from the images were analyzed using Mann-Whitney U Test and Kruskal-Wallis H Test with Bonferroni correction. RESULTS: The lowest value of marginal gap was identified in the samples from the LZ group and the highest value was identified in those from ZZ in both finish lines. The effect of finish lines was not significant for most groups but CM frameworks with chamfer finish lines and the DZ frameworks with shoulder finish lines showed significantly lower marginal gap values. CONCLUSION: The marginal gaps of the various tested zirconia and metal framework were within the range of clinical acceptability (120 µm). CLINICAL SIGNIFICANCE: The results of this in vitro study suggest that margin preparation design and type of zirconia and metal framework materials for various CAD-CAM systems have a significant effect on marginal fit of the resulting restorations. (J Esthet Restor Dent 28:238-246, 2016).

Investigation of the effect of different polishing techniques on the surface roughness of denture base and repair materials.

STATEMENT OF PROBLEM: The rough surface of denture base materials may cause plaque accumulation and staining. Thus, the effectiveness of polishing techniques should be known. PURPOSE: The purpose of this study was to compare the effects of chairside polishing kits and conventional laboratory techniques on the surface roughness of denture base and repair materials. MATERIAL AND METHODS: Ninety-six specimens, 50 ±1 mm in diameter and 0.5 ±0.05 thick, were fabricated from heat-polymerized acrylic resin (HP), polyamide resin (PR), and autopolymerizing resin (AP) and submitted to grinding with a tungsten carbide bur. The specimens were divided into 4 groups according to the polishing technique used: control group without polishing, conventional laboratory polishing, polished with Acrylic Polisher HP blue kit, and polished with AcryPoint polishing kit. Surface roughness (Ra) was measured after polishing with a profilometer. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference (HSD) test was performed to identify significant differences (α=.05). RESULTS: The polishing techniques significantly affected the Ra of denture base materials (P<.001). The highest mean average Ra was measured for the control group. The lowest Ra values were determined in specimens exposed to conventional laboratory polishing techniques. No significant differences were found between Acrylic Polisher HP blue and AcryPoint polishing kits (P>.05). Statistically significant differences were found in the Ra between the PR and both the HP and AP (P<.001); PR exhibited the highest Ra values. CONCLUSIONS: Conventional laboratory polishing was the most effective polishing technique. A significantly smoother surface than that of the specimens in the control group was produced with chairside silicone polishing kits.

Effect of surface treatments on the bond strength of soft denture lining materials to an acrylic resin denture base.

STATEMENT OF PROBLEM: Adhesive failure between acrylic resin and resilient liner material is commonly encountered in clinical practice. PURPOSE: The purpose of this study was to evaluate the effect of different surface treatments on the bond strength of 2 different resilient lining materials to an acrylic resin denture base. MATERIAL AND METHODS: Ninety-six dumbbell-shaped specimens were fabricated from heat-polymerized acrylic resin, and 3 mm of the material was cut from the thin midsection. The specimens were divided into 6 groups according to their surface treatments: no surface treatment (control group), 36% phosphoric acid etching (acid group), erbium:yttrium-aluminum-garnet (Er:YAG) laser (laser group), airborne-particle abrasion with 50-µm Al2O3 particles (abrasion group), an acid+laser group, and an abrasion+laser group. The specimens in each group were divided into 2 subgroups according to the resilient lining material used: heat-polymerized silicone based resilient liner (Molloplast B) and autopolymerized silicone-based resilient liner (Ufi Gel P). After all of the specimens had been polymerized, they were stored in distilled water at 37°C for 1 week. A tensile bond strength test was then performed. Data were analyzed with a 2-way ANOVA, and the Sidak multiple comparison test was used to identify significant differences (α=.05). The effects of the surface treatments and resilient lining materials on the surface of the denture base resin were examined with scanning electron microscopy. RESULTS: The tensile bond strength was significantly different between Molloplast B and Ufi Gel P (P<.001). The specimens of the acid group had the highest tensile bond strength, whereas those of the abrasion group had the lowest tensile bond strength. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. CONCLUSIONS: Molloplast B exhibited significantly higher bond strength than Ufi Gel P. Altering the surface of the acrylic resin denture base with 36% phosphoric acid etching increased bond strength.

Effect of repair resin type and surface treatment on the repair strength of heat-polymerized denture base resin.

STATEMENT OF PROBLEM: Acrylic resin denture fracture is common in prosthodontic practice. When fractured denture bases are repaired, recurrent fractures frequently occur at the repair surface interface or adjacent areas. PURPOSE: The purpose of this study was to evaluate the effect of different surface treatments on the flexural strength of the acrylic resin denture base repaired with heat-polymerized acrylic resin, autopolymerizing resin, and light-polymerized acrylic resin. MATERIAL AND METHODS: Ninety-six specimens of heat-polymerized acrylic resin were prepared according to the American Dental Association Specification No. 12 (65.0 × 10.0 × 2.5 mm) and sectioned into halves to create a repair gap (3.0 × 10 × 2.5 mm). The sectioned specimens were divided into 3 groups according to their repair materials. The specimens from each group were divided into 4 subgroups according to their surface treatments: a control group without any surface treatment; an experimental group treated with methyl methacrylate monomer (MMA group); an experimental group treated with airborne-particle abrasion with aluminum oxide particles of 250-µm particle size (abrasion group); and an experimental group treated with erbium:yttrium-aluminum-garnet laser (laser group). After the surface treatments, the 3 materials were placed into the repair gaps and then polymerized. After all of the specimens had been ground and polished, they were stored in distilled water at 37°C for 1 week and subjected to a 3-point bend test. Data were analyzed with a 2-way analysis of variance, and the Tukey honestly significant difference test was performed to identify significant differences (α=.05). The effects of the surface treatments and repair resins on the surface of the denture base resin were examined with scanning electron microscopy. RESULTS: Significant differences were found among the groups in terms of repair resin type (P<.001). All surface-treated specimens had higher flexural strength than controls, except the surface treated with the methyl methacrylate in the heat-polymerized group. A significant difference between the control and abrasion groups (P=.013) was found. The scanning electron microscopy observations showed that the application of surface treatments modified the surface of the denture base resin. CONCLUSIONS: The repair procedure with heat-polymerized resin exhibited significantly higher flexural strength than that of the autopolymerized and light-polymerized resins. In addition, the airborne-particle abrasion with aluminum oxide particles of 250-µm particle size improved the flexural strength of the specimens tested.

Use of mouthguard rates among university athletes during sport activities in Erzurum, Turkey.

The purpose of this study was to determine the attitudes of mouthguard users in Erzurum, Turkey. The participants' appreciation in the use of protective devices, such as mouthguards, during sport activities was also evaluated. In this study, a 10-item questionnaire was distributed to 50 coaches and a 10-item questionnaire was distributed to 768 university athletes of three different sport modalities (basketball, soccer and volleyball) in the Atatürk University Sport Competitions. The Sport Competitions are composed of 20 faculty, except the faculty of dentistry. The result of the coaches' questionnaires indicated that none of the athletes used mouthguards while participating in sports. Of the coaches, 64% had seen orofacial trauma in their athletes during sport activities and 76% believed that mouthguards prevented oral injuries. Of the coaches, 76% reported that university athletes should use mouthguards in sport activities. The result of the university athletes' questionnaires revealed that the mouthguard utilization rate was 0%. Of all players, 78.1% were males (age 17-29) and 21.9% were females (age 18-23). Of all players, 7.31% had suffered from one or more type of oral injury while not wearing mouthguards. The results indicate that in Turkey, the use of mouthguards is rare in sports. It should be a combined duty of dentists, sports physicians, and coaches to encourage the use of mouthguards during training and sport activities. Doctors and dentists need to recommend a more intensive education of students in sports medicine and sports dentistry.

Evaluation of the solubility of dental cements in artificial saliva of different pH values.

The aim of this study was to determine the solubility of dental cements in artificial saliva of different pH values. A total of 180 specimens--20 specimens (20 mm diameter x 1.5 mm thickness) for each dental cement-were prepared. After the specimens were weighed, they were set in the media with different pH values. After 24 hours, 72 hours, seven days, and 28 days, the specimens were taken out, dried in a desiccator, and re-weighed. Percentage of solubility at each time period was calculated as 100 per cent times weight loss divided by the initial weight of the specimen. Analysis of variance and LSD multiple comparison test were applied. It was found that cement type, storage time, and medium pH exerted statistically significant (p<0.001) effects on solubility. Among the tested cement types, zinc phosphate cement (Adhesor Carbofine) presented the highest solubility. In terms of medium pH, the cements seemed to be most stable in the medium with pH 7.

Comparative study of water sorption and solubility of soft lining materials in the different solutions.

In this study, two acrylic based materials and three silicone rubber soft lining materials were investigated to determine the percentage of absorption and solubility in artificial saliva, distilled water, and denture cleanser. In addition, the effect of denture cleanser on surface properties of soft lining materials was also evaluated. For sorption and solubility testing, 75 discs (50 mm x 0.5 mm) were prepared and divided into 5 groups with 15 samples in each group. The specimens were stored in different solutions, and tested after 1, 4, and 16 weeks. Analysis of variance was used to find the significant differences between the materials at all time intervals. The acrylic resin soft lining materials had higher solubility (3.432% Visco-gel in artificial saliva) and absorption (3.349% Visco-gel in distilled water) than Molloplast-B after 16 weeks of aging. The greatest hardness and color change were shown in the acrylic soft lining materials.

Abrasion resistance of veneering materials to tooth brushing.

This study was carried out to comparatively examine abrasion which occurred as a result of brushing as well as abrasives in veneering materials used in prosthetic restorations. Twenty out of forty specimens prepared at the dimensions of 14x5x3 mm, there being ten specimens of each veneering materials, were subjected to tooth brushing with water alone. The other twenty specimens were subjected to a tooth brushing procedure with a paste- water mixture with the aim of evaluating the effects of abrasives on abrasion. As a result, it was statistically determined that porcelain, an ideal facet material, had the best resistance to abrasion by toothbrush, light cured aesthetic materials being second Poly methyl methacrylate had the least abrasion resistance.