Background Restoration of the teeth with extensive root canals with different post systems is a challenge for clinicians. Evaluation of these systems is important for clinical success. The aim of this study was to compare the fracture resistance and fracture mode of endodontically treated thin-walled teeth which restored with different post systems. Methods Eighty extracted and endodontically treated maxillary canines were divided into 4 groups (n = 20) and the thickness of the radicular dentin walls was reduced by using diamond burs. Each root was embedded in an autopolymerizing resin with a 0.25 mm layer of vinyl polysiloxane material to simulate the periodontal ligament. The subgroups were restored with one of the following post systems: only composite resin (Group 1), cast post (Group 2), glass-fiber post (Group 3), and I-TFC post (Group 4). The samples were subjected to a gradually increasing force (0,5 mm/min). The force required to fracture was recorded, and the data were analyzed with ANOVA, Tukey test's and Chi–Square test (p < 0.05). Results The highest fracture resistance was recorded for Group 2, followed by the Group 3, Group 4, and Group 1. Differences in the fracture resistance of teeth were significant among the groups (p < 0.05). The fracture resistance of Group 4 was significantly different than the other tested post systems (p < 0.05). Conclusions The lowest fracture resistance was recorded for Group 1, but among all post systems, Group 4 had the lowest fracture resistance. The fracture mode of the fiber posts (Radix and I-TFC posts) would permit repair of the tooth.

ObjectiveThe aim of this study was to investigate the color change, translucency, and whiteness index of three different resin matrix ceramics and a resin composite subjected to different bleaching agents.Materials and MethodsTwenty disc‐shaped specimens (A2 shaded) for three different resin matrix ceramic brands (Groups Ena, Ulti, and Cera) (totally 60) were prepared using the CAD/CAM technique and 20 nanofiller composite specimens (Group Comp) (A2 shaded) with the same dimensions were prepared as the control group. The color change (∆E00), relative translucency parameter (RTP), and whiteness index (WID) of the specimens initial and after different bleaching procedures (home‐bleaching and office‐bleaching) were calculated using ∆E00, TP00, and WID formulas. Two‐way analysis of variance (ANOVA) and multiple comparison test with Bonferroni correction (α = .05) at the significance level of P < .05 were performed for the comparisons of ∆E00 values. The RTP and WID values were evaluated by using repeated measures ANOVA and multiple‐comparison test with Bonferroni corrections (α = .05) at the significance level of P < .05.ResultsBleaching procedure and material type were found to be significant regardless of bleaching type for RTP and WID values. Material type has a significant effect on the ∆E00 values. The highest color change values were determined in Group Comp (P < .05).ConclusionsBleaching procedures significantly affected the RTP values of Groups Ulti and Cera (P < .05). ∆E00 values for the resin matrix ceramics after the bleaching procedures were below the clinically acceptable values, regardless of the bleaching agent.Clinical SignificanceOptically, materials such as resin matrix ceramics have properties different from not only enamel and dentin but also among themselves. The possible effect of bleaching agents on these materials should be considered carefully while choosing the restorative material.

Background. Zirconia restorations with high mechanical properties are the current treatment options for fixed restorations with advantages of high biocompatibility and low pulp irritation. Although the effect of sintering time and temperature on the optical and mechanical properties of zirconia core material were investigated, the effect of these parameters on the translucent monolithic zirconia is still uncertain. This study aimed to evaluate the effect of the changes in sintering temperature and holding time on the mechanical and structural properties of monolithic zirconia. Methods. Totally, 340 self-colored (A2) zirconia specimens from two different monolithic zirconia groups (n=170) were prepared, measuring 15.5×12.5×1.2 mm. Then, 17 subgroups (n=10), including the control groups, were sintered according to sintering parameters. XRD analysis was used to determine phase transformations. The surface roughness of the specimens was evaluated using profilometry, and the flexural strength of the specimens was evaluated by the three-point bending test. The data were analyzed using three-way ANOVA and post hoc multiple comparison test with Bonferroni correction (a=0.05) at a significance level of 0.05. Independent-samples t-test was used to compare the subgroups between the control groups (P˂0.05). Results. No tetragonal-to-monoclinic phase transformation was observed in the groups. Changes in the sintering parameters did not significantly affect the surface roughness and flexural strength of monolithic zirconia. Surface roughness values for all the subgroups were above the clinically critical limit. Conclusion. According to the results of this study, changes in the sintering parameters did not affect the surface phase transformation, surface roughness, and flexural strength of monolithic zirconia.

PURPOSEThe aim of this study was to evaluate effect of different surface treatment methods on the bond strength between aged composite-resin core and luting agent.MATERIALS AND METHODSSeventy-five resin composites and also seventy-five zirconia ceramic discs were prepared. 60 composite samples were exposed to thermal aging (10,000 cycles, 5 to 55℃) and different surface treatment. All specimens were separated into 5 groups (n=15): 1) Intact specimens 2) Thermal aging-air polishing 3) Thermal aging- Er:YAG laser irradiation 4) Thermal aging- acid etching 5) Thermal-aging. All specimens were bonded to the zirconia discs with resin cement and fixed to universal testing machine and bond strength testing loaded to failure with a crosshead speed of 0.5 mm/min. The fractured surface was classified as adhesive failure, cohesive failure and adhesive-cohesive failure. The bond strength data was statistically compared by the Kruskal-Wallis method complemented by the Bonferroni correction Mann-Whitney U test. The probability level for statistical significance was set at α=.05.RESULTSThermal aging and different surface treatment methods have significant effect on the bond strength between composite-resin cores and luting-agent (P<.05). The mean baseline bond strength values ranged between 7.07 ± 2.11 and 26.05 ± 6.53 N. The highest bond strength of 26.05 ± 6.53 N was obtained with Group 3. Group 5 showed the lowest value of bond strength.CONCLUSIONAppropriate surface treatment method should be applied to aged composite resin cores or aged-composites restorations should be replaced for the optimal bond strength and the clinical success.

All‐ceramics materials have been widely used in dental practice due to advantages of esthetic outcome. Color parameters, one of the major factors for the esthetic outcome, are affected from different factors such as repeated firings, chemical composition and thickness. In clinical practice, ceramics were frequently subjected to the repeated firings, but the effects of the repeated firings on the color parameters have been underestimated or unknown, so the aim of the study was to evaluate the effects of the repeated firings on the color parameters of all‐ceramic materials. Two commercially available A2 shaded all‐ceramic systems were used in this study (lithium disilicate pressable ceramics and computer aided design/computer aided manufacturing [CAD/CAM] fabricated zirconia). Ten samples for each group (zirconia and lithium disilicate) were prepared and subjected to repeated firings, respectively (1st, 3rd, 5th). Color measurements were performed after each repeated firings using a colorimeter (Minolta CR 321, Konica Minolta, Tokyo, Japan). The perceptibility threshold and acceptability threshold for color changes (ΔE00) was defined as 0.8 and 1.8, respectively. Statistical analysis of the results was performed by using repeated measures ANOVA for color parameters and using non‐parametric Kruskal‐Wallis and Mann‐Whitney‐U test for ΔE00 values (P < .05). L*, a* values showed statistically significant differences for lithium disilicate pressable ceramics and were not significant the zirconia specimens. ΔE00 values were above the perceptibility level for both lithium disilicate and zirconia specimens. Repeated firings affect the color parameters of the lithium disilicate specimens. As a result of repeated firings, lithium disilicate ceramics become lighter and greener.

PURPOSE Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group 15℃, Group 20℃, and Group 40℃. All groups were sintered according to heating rates with the sintering temperature of 1500℃, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups ( P >.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group 20℃ and Control Group, respectively. CONCLUSION Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.

Zirkonya restorasyonlarda görülen başarısızlıklar genellikle tabakalama seramiğinde atma şeklinde meydana gelse de altyapı materyalinde de geri dönüşümsüz kırılmalar meydana gelebilmektedir. Tekrarlanan fırınlama işlemlerinin, zirkonyanın kimyasal yapısını oluşturan temel elementlerde ve mekanik özelliklerinde nasıl bir etki meydana getirdiği tam olarak bilinmemektedir. Bu çalışmanın amacı tekrarlanan fırınlamaların zirkonya altyapılarında meydana gelen elementsel değişiklikler ve mekanik özellikler üzerine etkisinin değerlendirilmesidir. Gereç ve Yöntem: Altmış adet, 1 mm kalınlığında ve 10 mm çapında zirkonya tam seramik örnek pre-sinterize blok kullanılarak CAD/CAM sistemi ile üretildi. Tekrarlanan fırınlama prosedürü gruplara göre örneklere 900°C'de ilave fırınlamalar uygulanarak tamamlandı. Zirkonya yapısında meydana gelen elementsel değişiklikler XRF spektrometre cihazı kullanılarak tespit edildi. Zirkonya örneklerde meydana gelen bükülme dayanımı değişiklikleri biaksiyal bükülme dayanımı testi ile tespit edildi. Bulgular: Materyal yapısında zirkonyum elementinde meydana gelen değişikliklerin istatistiksel olarak anlamlı olmadığı, itrium elementinde meydana gelen değişikliklerin ise anlamlı olduğu tespit edildi (p˂0,05). Gruplar arasında ortalama bükülme dayanımı değerleri arasındaki farkın anlamlı olmadığı tespit edildi. Sonuç: Tekrarlanan fırınlama işlemleri materyal yapısındaki itrium elementi oranını anlamlı şekilde değiştirmiştir, fakat bu değişimin materyalin biaksiyel bükülme dayanımı üzerinde anlamlı bir etkisi olmadığı tespit edilmiştir. Anahtar kelimeler: Tekrarlanan fırınlamalar, XRF, zirkonya. SUMMARY Aim: Failure of zirconia restorations usually occurs in veneering ceramics as chipping, but catastrophic failures can also occur in the zirconia substructure. The effect of the repeated firings on the mechanical properties and chemical structure of zirconia is uncertain. The purpose of the study was to evaluate the effect of repeated firings on the mechanical properties and elemental changes of zirconia substructure. Materials and Methods: Sixty samples, 1 mm thickness and 10 mm in diameter, were produced with the CAD/CAM system using the pre-sintered zirconia blocks. Repeated firing procedure were completed by applying additional firings at 900 °C according to the groups. Elemental changes in the zirconia structure were determined using XRF analysis. The changes in the flexural strength of the zirconia samples were determined by the biaxial flexural strength test. Results: Changes in the zirconia element in the material structure were not statistically significant, while those in the itrium element were found to be significant(p˂0.05). It was found that the differences between the mean flexural strength values of the groups were not significant.

Ö ÖZ ZE ET T A Am ma aç ç: : Metal destekli porselen restorasyonlar sahip oldukları üstün mekanik özellikler gibi avantajları ile yaygın olarak kullanılan tedavi seçenekleridir. Farklı yöntemlerle elde edilen Co-Cr alaşımlarının metal-porselen bağlanma dayanımlarını, iki farklı test metodu kullanarak değerlendirmektir. G Ge er re eç ç v ve e Y Yö ön nt te em ml le er r: : Bu çalışmada, Co-Cr alaşım örnekler selektif lazer sinterleme (n=20) ve geleneksel döküm yöntemi (n=20) kullanılarak hazırlandı ve 4 alt grup (n=10) oluşturuldu. Geleneksel döküm ve selektif lazer sinterleme ile elde edilen örneklere üç nokta bükme testi için, ISO 9693'e göre toplam 1,1 mm kalınlığında olacak şekilde porselen tabakası uygulandı. Makaslama bağlanma dayanımı testi için ise örneklere 4 mm çapında ve 4 mm kalınlığında porselen tabaka uygulandı. Örneklere, universal test cihazı kullanılarak 1,5 mm/dk hız ve 90 o açı ile üç nokta bükme testi ve 0,5 mm/dk hızla makaslama bağlanma dayanımı testi uygulanarak, metal-porselen bağlanma dayanımları ölçüldü. Elde edilen veriler tek yönlü varyans analizi kullanılarak p<0,05 anlamlılık düzeyinde değerlendirildi. B Bu ul lg gu ul la ar r: : Farklı yöntemlerle elde edilen metal alaşımlarının metal-porselen bağlantısının üç nokta bükme testi ile değerlendirilmesi sonucu elde edilen değerler arasında istatistiksel olarak anlamlı bir fark bulunamamıştır. Selektif lazer sinterleme yöntemiyle elde edilen alaşımların metal-porselen makaslama bağlanma dayanımlarının, geleneksel döküm yöntemiyle hazırlanan alaşımlara göre anlamı derecede daha yüksek olduğu saptanmıştır. S So on nu uç ç: : Üç nokta bükme testi sonuçlarına göre, grupların metal-porselen bağlanım dayanımları arasında anlamlı bir fark bulunamamıştır ve bu değerler ISO 9693'e göre minimum kabul edilebilir sınırın üzerindedir. Selektif lazer sinterleme yöntemiyle hazırlanan örneklerin metal-porselen makaslama bağlanım dayanımları, geleneksel döküm yöntemiyle hazırlanan alaşımlara göre daha yüksek bulunmuştur.A An na ah ht ta ar r K Ke el li im me el le er r: : Dental porselen; metal-seramik alaşımlar; selektif lazer sinterleme A AB BS ST TR RA AC CT T O Ob bj je ec ct ti iv ve e: : Metal-supported porcelain restorations are widely used as a treatment options due to it's advantages such as superior mechanical properties. The aim of this study was to evaluate the metal-porcelain bond strengths of Co-Cr alloys obtained by different methods using two different testing methods. M Ma at te er ri ia al l a an nd d M Me et th ho od ds s: : In this study, Co-Cr alloy specimens were prepared using with selective laser sintering (n=20) and conventional casting (n=20) and specimens were divided 4 subgroups (n=10). For the three-point bending test, porcelain layer were applied to samples according to ISO 9693 with a total thickness of 1.1 mm. For shear bond strength test, porcelain layer 4 mm in diameter and 4 mm in thickness was applied to the specimens. The metal-porcelain bond strengths were measured by a universal testing machine using three-p oint-ben...