Funda Bayindir

Bond strength of resin cement to yttrium-stabilized tetragonal zirconia ceramic treated with air abrasion, silica coating, and laser irradiation.

OBJECTIVE The purpose of this study was to evaluate the shear bond strength of a resin cement to yttrium-stabilized tetragonal zirconia (Y-TZP) surfaces treated with air abrasion, silica coating, or CO(2), Er:YAG, or Nd:YAG laser irradiation, or irradiated by each laser after air abrasion. BACKGROUND DATA Optimized methods are needed to improve the adhesive bonding between resin cement and Y-TZP ceramic. METHODS Twelve specimens were irradiated with each laser at different parameters and examined by scanning electron microscopy to determine which parameters to use in this study. One hundred forty-one Y-TZP discs were assigned to nine groups: C, no treatment; AA, air abrasion; CJ, silica coating; ER, Er:YAG laser; ND, Nd:YAG laser; CO, CO(2) laser; AA+ER, air abrasion + Er:YAG laser; AA+ND, air abrasion + Nd:YAG laser; AA+CO, air abrasion + CO(2) laser. The composite cylinders were fabricated. After the surface treatments, the specimens were silanized and composite cylinders were cemented with the resin cement. The shear bond strength test was performed after specimens were stored in water for 24 h and after thermocycling for 500 cycles. RESULTS The highest bond strength was obtained in the AA group and was similar to that of the CJ group. In C, ER, CO, ND, AA+ND, and AA+CO groups, the shear bond strengths were similar to each other according to the Duncan test results. The lowest bond value was obtained in the AA+ER group. CONCLUSION Although air abrasion and silica coating were the most effective surface treatment methods, CO(2) and Er:YAG laser irradiation alone or Nd:YAG laser irradiation after air abrasion may be used as an alternative treatment method to increase the bond strength between resin cement and Y-TZP material.

The effect of staining solutions on the color stability of provisional prosthodontic materials

OBJECTIVES The aim of this study was to evaluate the effects of staining solutions on the color stability of self-cure provisional resin materials. METHODS The specimens were prepared for each of three auto-polymerized bis-acryl resin and auto-polymerized methyl methacrylate provisional resin material. The baseline color values were measured with a colorimeter according to the CIE L(*)a(*)b(*) color scale. After the first measurement (T(0)), specimens were placed in staining solutions (coffee, coca-cola, burn and distilled water for control group) and the other measurements were taken after 24h (T(1)), 1 week (T(2)) and 4 weeks (T(3)). RESULTS Data were analyze statistically by (a) repeated measures (ANOVA), (b) one and two way ANOVA, and (c) Tukey HSD multiple comparison tests. At the 24h immersion period, the post hoc analysis indicated that AccessCrown-coffee revealed the highest ΔE(*) values (4.4). At the second immersion period (1 week), Structur2 SC-coffee had the highest ΔE(*) values compared with other materials (5.4). CONCLUSIONS The degrees of discoloration were increased with immersion time. The methylmethacrylate resin was more resistant to discoloration than bis-acryl resins. After immersion for 30 days, the coffee solution resulted in unacceptable discoloration for all the tested materials.

Microtensile Bond Strength of Resin Cement to a Feldspathic Ceramic

OBJECTIVE The purpose of this study was to evaluate the microtensile bond strength of resin cement to a feldspathic ceramic after treating the surface with (a) hydrofluoric (HF) acid, (b) air abrasion, (c) Er:YAG laser irradiation, (d) Nd:YAG laser irradiation, and (e) HF acid etching after either air abrasion or laser irradiation. BACKGROUND DATA It is unknown whether the laser application or its combination with another treatment method can be used as a tool to roughen the surface of a feldspathic ceramic in order to increase the bond strength between the resin cement and ceramic surface. MATERIALS AND METHODS Forty feldspathic ceramic blocks (Ceramco(TM)) were prepared and divided into eight equal groups (n = 5) according to the following surface treatments: no treatment; etching with 9.5% HF acid; air abrasion with 50 μm Al(2)O(3); Er:YAG laser irradiation; Nd:YAG laser irradiation; air abrasion plus acid etching; Er:YAG laser plus acid etching; and Nd:YAG laser plus acid etching. After surface treatment, a silane-coupling agent and resin cement (Panavia F(TM)) were applied to each block. After storing for 24 h at 37°C and thermocycling between 5°C and 55°C for 1000 cycles, the microtensile bond strength of each specimen was measured. RESULTS The highest bond strength was obtained from HF acid etching. HF acid etching after each laser irradiation significantly increased the bond strength (p < 0.05). However, HF acid etching after air abrasion decreased bond strength when compared to air abrasion alone. CONCLUSIONS HF acid etching is the most effective surface treatment method for a feldspathic ceramic. However, laser irradiation with either the Er:YAG or Nd:YAG laser is not an adequate method for improving the bond strength of Panavia F. The laser application should be combined with HF acid etching.

In vitro evaluation of long-term cytotoxic response of injection-molded polyamide and polymethyle metacrylate denture base materials on primary fibroblast cell culture

Abstract Objective. This study investigated the long-term cytotoxic response of thermoplastic polyamide and conventional polymethyle metacrylate (PMMA) denture base materials. Materials and ethods. Twenty discs were prepared for each polyamide, heat and cold cured PMMA denture base resins (totally 60) and divided into four sub-groups (n = 5). Cytotoxicity was assessed with the direct cell contact method using cell viability and neutral red (NR) uptake assay. Each sub-group was tested at initial and after being aged for 24 h, 1 week and 8 weeks with artificial saliva according to ISO 10993 standards. Results. There were no significantly difference among the materials and control groups after initial, 24 h and 1 week testing. In 24 h testing, only Deflex was more toxic according to the Control group (p < 0.05). After 8 weeks of aging with artificial saliva, all materials were significantly cytotoxic when compared to the control group. QC20 was more toxic than Deflex and SC Cold Cure (p < 0.05). There were significant differences between the 8 week aging group and the initial, 24 h and 1 week testing for all materials (p < 0.05). Conclusions. Cytotoxicity of all tested denture base materials increased significantly after the long-term aging. Therefore, long-term aging may be useful to determine a dental materials toxicity. Polyamide denture base material had a similar toxicity profile with conventional heat- and cold-cured PMMA.

Effect of number of firings on the color and translucency of ceramic core materials with veneer ceramic of different thicknesses

Statement of problem. Whether masking or translucency should be the goal for achieving an esthetic restoration with ceramic materials is unknown. Purpose. The purpose of this in vitro study was to examine the effect of the number of firings on the color and translucency of ceramic core material with different thicknesses of veneer ceramic. Material and methods. Three different ceramic systems were used: IPS Empress (IE), IPS e.max Press (IEP), and Turkom Cera (TC). Ninety disk‐shaped cores, 10 mm in diameter and 0.8 mm in thickness were prepared using each system (n=30). The specimens were divided into 3 subgroups (n=10) according to the thickness of the veneering ceramic: 0.5, 1.0, and 1.5 mm. The specimens were fired 1, 3, and 5 times, and the color parameters of the specimens were measured. The color measurements were repeated, and the data were statistically evaluated using 2‐way and multifactorial analysis of variance, the Duncan test, and the Bonferroni post hoc test. Results. The number of firings affected the translucency parameter and CIELab values. Increased porcelain thickness led to decreased translucency parameter and L* values and increased a* and b* values (P<.05). The IE system was the most translucent (P<.001). The changes with increased firing periods were not statistically significant (P>.05). The number of firings affected the color change of the IE and IEP systems but not of the translucency parameter system. Conclusions. Repeated firings and porcelain thickness affected the final color and translucency of the ceramic systems tested. These 2 factors adversely affected the esthetic result and should be considered in both the preparation and the laboratory phase.

Color changes in resin cement polymerized with different curing lights under indirect restorations

Aim: The aim of the study was to investigate the effects of different interface materials and curing units on color changes in a resin cement material. Materials and Methods: Three interface materials and different curing systems, quartz-tungsten-halogen and polywave and monowave light-emitting diode (LED) light curing units, were studied at two-time intervals. Polystyrene strip was used as a control group. All measurements were made on a white background for standard color measurement. According to the CIE LFNx01aFNx01bFNx01 color space, the baseline color values of each specimen were measured. Differences between the measurements were calculated as ΔE, ΔL, Δa, and Δb. Data were analyzed using analysis of variance (ANOVA) and Duncan′s tests (α = 0.05) with SPSS 20.0 software (SPSS Inc., Chicago, IL, USA). ANOVA revealed significance for interface materials and curing units and time for ΔE (P < 0.05). Results: Interaction between polymerizing units, material and time was not significant (P > 0.05). Monowave LED exhibited significantly higher color changes than the other units ([P < 0.05] [ΔE 2.94 ± 0.44]). QTH promoted composite specimens significantly less color change ([P < 0.05] [ΔE 0.87 ± 0.41]). Conclusion: This study concluded that color of resin cement used in the adhesion of indirect restorations was affected by curing device light and indirect restoration material type.

Cytotoxicity of soft and hard denture lining materials on MA-104, Vero and primary tooth cell culture

Abstract The aim of this in vitro study was to determine the cytotoxicity of three different soft and hard lining materials, which are used in prosthodontic clinic. Meliodent, Viscogel and Molloplast were evaluated with MA-104, Vero and primary tooth root cell culture for one, three and eight days. The results showed that the eluates from Viscogel were not cytotoxic but those from Molloplast were cytotoxic (20%) on primary tooth root cell culture. On the other hand, Viscogel was cytotoxic (10%), but Molloplast was not cytotoxic on MA-104 cell culture. Viscogel was also found to be cytotoxic (35%) on Vero cell culture. Meliodent was found to be non-cytotoxic on all tested cell cultures. The influence of the cytotoxicity depended on the materials and type of cell culture tested. However, additional in vivo studies are needed to evaluate the potential toxicities of the prosthodontic dental materials during clinical operative procedures.

Potentiodynamic polarisation technique for corrosion testing of Cr–Co and Cr–Ni alloys in artificial saliva and soft drinks

Abstract The corrosion of alloys used in dentistry affects the biological, functional and esthetic properties of the material. This study compares the corrosion behaviour of Cr–Co and Cr–Ni alloys used in restorative dentistry in four different types of solution (distilled water, orange nectar, cola and artificial saliva). Electrochemical polarisation experiments were performed using a potentiostat and carried out in a corrosion cell containing a solution of 500 mL at body temperature (37°C). It can be seen from experimental results that Cr–Co alloy has lower corrosion current densities than Cr–Ni alloy. When the media effect is observed, corrosion current densities are higher for cola and orange juice, which have lower pH. As a result, Cr–Co alloys seem to be, from the biocompatibility point of view, more convenient in the intraoral use as dental alloys. In conclusion, corrosive potential of Cr–Ni alloy is statistically higher in cola drinks compared with juices.

An investigation of the esthetic indicators of maxillary anterior teeth in young Turkish people

Statement of problem. Comprehensive studies evaluating the dimensions of anterior maxillary teeth in the Turkish population with respect to different esthetic parameters are lacking. Purpose. The purpose of this clinical study was to evaluate different proportions of teeth and compare them with current esthetic parameters such as the golden proportion, recurring esthetic dental proportion, and width‐to‐height ratio of central incisors and to evaluate whether the apparent contact dimension of maxillary anterior teeth follows the “50:40:30” rule. Material and methods. A total of 150 Turkish dental students (81 men and 69 women) aged between 18 and 24 years participated in the study. Standardized digital photographs of the mouth were made from an anterior view. The width and length of the maxillary central incisor, apparent width of the maxillary lateral and canine teeth, and distances between contact areas of the maxillary incisor teeth were measured with software. Differences between the measured proportions and the determined esthetic parameters were assessed with the 1‐sample t test (&agr;=.05). Results. The width and length proportions of the maxillary incisor teeth in both sexes were significantly different than the golden and recurring esthetic dental proportions. The width‐to‐height ratio for the maxillary central incisor was different from 80%, which is considered optimal, and the difference among these parameters was statistically significant (P<.001). The apparent contact dimensions on the right and left sides were not statistically significantly different (P>.05). However, the proportions did not fit the 50:40:30 ratio that has been defined as the esthetic proportion, and the differences were statistically significant (P<.001). Conclusion. Proportions among maxillary anterior teeth were found to be significantly different from the golden proportion and recurring esthetic dental proportion in both sexes. The proportions of apparent contact dimension were significantly different than the 50:40:30 ratio in both sexes. The width‐to‐height ratio for maxillary central incisor was significantly different from 80% in both sexes.

BOND STRENGTH OF SOFT LINING MATERIAL TO POLYAMIDE DENTURE MATERIAL

Aim: The aim of this study was to evaluate the bond strength of soft lining material to polyamide denture material. Materials and Methods: Twenty-five polyamide denture base materials and soft denture lining material were used in this study. The samples were divided into five groups according to the surface treatments: Group 1 (Control): No surface treatment Group 2: Samples were sandblasted with 5o µm Al 2 O 3 powder. Group 3: Samples were grinded with a diamond bur. Group 4: Samples were etched with % 37 Orthophosphoric acid. Group 5: Retention holes were slotted with diamond bur to samples. Then the samples were tested in tensile mode in a universal testing machine at cross-head speed of 0.5 mm/min. The statistically analysis of obtained data were performed with use one-way analysis of variance test. Results: The results showed that the highest bond strength value (92.54 N) was identified in Group 3, the lowest bond strength value (31.56 N) in Group 4. The result of one-way analysis of variance test showed that there were not statistically significant differences between the groups. (p>0.05) Conclusion: As a result of this study, the surface treatments were not affected on bond strength of soft lining material to polyamide denture material. Key Words: Polyamide denture, soft lining materia YUMUŞAK ASTAR MADDESININ POLIAMID KAIDE MATERYALINE BAĞLANMA DAYANIMI Amac: Bu calismanin amaci yumusak astar maddesinin poliamid kaide maddesine baglanma dayaniminin incelenmesidir. Gerec ve Yontem: Calisma kapsaminda 25 adet poliamid kaide maddesi ve bir yumusak astar maddesi kullanildi. Ornekler yuzey islemlerine gore bes gruba ayrildi: Grup 1 (Kontrol): Hicbir yuzey islemi uygulanmadi. Grup 2: Ornekler 50 µm partikul boyutlu Al 2 O 3 tozu ile kumlandi. Grup 3: Ornekler elmas frezle asindirildi. Grup 4: Ornekler % 37’lik ortofosforik asit ile asitlendi. Grup 5: Elmas bir frezle orneklere retansiyon oluklari acildi. Ornekler universal test cihazinda 0.5 mm/min baslik hizi ile test edildi. Verilerin istatistiksel analizi tek yonlu varyans analizi testi ile yapildi. Bulgular: Sonuclar en yuksek baglanma dayanimi degerinin (92.54 N) 3. Grupta, en dusuk baglanma dayanimi degerinin ise (31.56 N) 4. Grupta oldugunu gosterdi. Tek yonlu varyans analizinin sonuclarina gore gruplar arasindaki farkin istatistiksel olarak anlamli olmadigi goruldu (p>0.05). Sonuclar: Yuzey islemlerinin yumusak astar maddesi ile poliamid kaide maddesi arasindaki baglanti kuvvetini etkilemedigi sonucuna varildi. Anahtar Kelimeler: Poliamid kaide maddesi, yumusak astar maddesi