Farklı Diş Beyazlatma Yöntemlerinin Dişlerde Renk Değişimi ve Yüzey Özelliklerine Etkileri

Amaç: Işık ile aktive edilmeden, LED ışık kaynağı ile ve Er: YAG lazer ile aktive edilen %40 konsantrasyondaki hidrojen peroksit (HP) beyazlatma jeli ile beyazlatma işleminin renk değişikliğine, yüzeyin mikrosertlik ve pürüzlülük özelliklerine olan etkilerini incelemektir. Gereç ve Yöntem: Çalışmada çekilmiş sağlıklı üçüncü büyük azı dişleri kullanılmıştır. Akrilik bloklara gömülen dişler 2200 grit’e kadar zımpara ile zımparalanarak minede düz yüzeyler elde edilmiştir. Biri kontrol grubu (Grup K) olmak üzere toplam dört grup değerlendirilmiştir. Bunlar; aktivasyon yapılmaksızın beyazlatma jeli uygulanan grup (Grup J), 385-515 nm dalga boyunda ve 3200 mW/cm2 güçte ışık üreten LED ışık kaynağı ile beyazlatma yapılan grup (Grup LED) ve 50 mJ enerji ile10 Hz’de ve VLP modunda (1000 µs atım süresi) ile kullanılan Er:YAG lazer ile aktivasyon yapılan gruptur (Grup Er:YAG). Beyazlatma işleminin öncesinde ve sonrasında spektrofotometre ile renk ölçümü yapılmış ve renk değişimi (∆E00) CIEDE2000 formülü ile hesaplanmıştır. Bir hafta örnekler yapay tükürük içerisinde bekletildikten sonra 980 g yük 15 s boyunca uygulanarak mikrosertlik ölçümleri ve kontakt tipi bir profilometre ile pürüzlülük ölçümleri yapılmıştır. Veriler Oneway ANOVA testi ile değerlendirilmiştir. Bulgular: Beyazlatma yapılan tüm gruplarda renk değişikliği gözle fark edilebilme eşiğinin üzerinde saptanırken gruplar arası anlamlı farklılık bulunmamıştır. Kontrol grubu ile beyazlatma yapılan gruplarda mikrosertlik ve pürüzlülük değerleri anlamlı bir değişim göstermemiştir. Sonuç: Beyazlatma işleminden bir hafta sonra diş minesinin yüzey özellikleri beyazlatma yapılmamış mineden farklı değildir

Farewell, Norbert

PURPOSE OF THE REVIEW: The concept of tree-related microhabitats (TreMs) is an approach to assess and manage multi-taxon species richness in forest ecosystems. Owing to their provision of special habitat features, TreMs are of special interest as a surrogate biodiversity indicator. In particular, in retention forestry, TreMs have gained attention over the past decade as a selection criterion for retained structural elements such as habitat trees. This review seeks to (a) address the suitability of TreMs as biodiversity indicator in the context of retention forestry, (b) summarize drivers of TreM occurrence and the status quo of the implementation of TreM-based retention concepts in forest management, and (c) discuss current and future challenges to the use of TreMs as biodiversity indicator. RECENT FINDINGS: The TreM concept originated in Europe where it is now increasingly implemented. Most studies of the quantity, quality, and diversity of TreMs are focused on tree species from this region, although it is increasingly applied in other contexts. In addition to tree species, tree dimensions and live status have been identified as the main drivers of TreM occurrence. One major remaining research challenge is to verify relationships between the occurrence and abundance of forest-dwelling species from different taxonomic groups and TreMs to improve the evidence basis of this concept and thus increase its integration in forest conservation approaches. TreMs are not the “silver bullet” indicator to quantify biodiversity of forest dwelling species, but they provide an important tool for forest managers to guide the selection of habitat trees for the conservation of the associated biodiversity

The effect of artificial accelerated aging on the color stability, microhardness, and surface roughness of different dental laminate veneer materials

© 2020 Wiley Periodicals, Inc.Objective: This study aimed to evaluate the effect of artificial accelerated aging (AAA) on color stability, surface roughness, and microhardness of three laminate veneer (LV) materials. Materials and Methods: Specimens of ceramic LV (CLV-IPS E.max Press), hand-layered composite LV (hand-layered laminate veneer [HLV]-Tetric N-Ceram), and prefabricated composite LV (prefabricated laminate veneer [PLV]-Componeer Coltene) were prepared as discs (n = 10). CIE L*, a*, and b* color coordinates, the Vickers microhardness, and surface roughness were measured 24 hours after preparation and reevaluated after aging for 300 hours in an ultraviolet (UV)-AAA system (Ci35 Weather-Ometer). Color difference (CIEDE2000 [ΔE00]) was calculated. Data were statistically analyzed with the Shapiro-Wilk test and the Kruskall-Wallis test followed by the Mann-Whitney U tests (α =.05). Results: All of the LV groups showed significant differences in ΔE00 after AAA (P <.001). Comparing the color changes of the HLVs with the PLVs, no significant difference could be found (P =.705). There was a statistically significant difference in the means of changes in microhardness among the LVs materials (P <.001). The changes in surface roughness results showed a significant difference after AAA in all the LVs (P <.001). Conclusions: Within the limitations of this in vitro study, the color stability, the microhardness, and surface roughness of tested LVs were influenced by AAA. Clinical significance: The prefabricated composite LV system does not replace the individualized ceramic LV technique, but rather offers an alternative to hand-layered LVs, which is delicate and time-consuming technique

The Effect of Dentin Desensitizer With Different Layers on Thermal Changes on the Pulp During Fabrication of Provisional Restoration

Purpose: This study investigated the effects of different desensitizers and an adhesive material application on pulpal temperature rise during direct provisional restoration polymerization. Materials and Methods: Two dentin desensitizers (Systemp, Ivoclar; BisBlock, Bisco) and a dentin adhesive (Prime Bond, Dentsply) were applied to the dentin surfaces as single layer or double layer. One autopolymerizing methacrylate (Prevision, Heraeus Kulzer) and one light polymerizing composite (Revotek LC, GC) provisional restoration materials were used in this study. A total of 160 dentin disks were prepared from extracted molars. These dentin disks were placed on an apparatus developed to measure temperature rise. After the desensitizer or dentin adhesive application, provisional materials were polymerized according to the manufacturers' instructions. The temperature increase was measured under the dentin disk with a J-type thermocouple wire that was connected to a data logger. Differences between initial and highest temperature reading were taken, and 10 readings were averaged to determine the mean value in temperature rise. Statistical analysis was performed with three-way analysis of variance followed by Tukey HSD test (alpha = 0.05). Results: Temperature rise varied according to the provisional restoration material used (composite resin, methacrylate) (p < 0.001.), the agent thickness (single, double) (p < 0.001), and the agent (desensitizer, adhesive) (p < 0.001). The composite resin-based provisional material induced higher thermal changes than methacrylate based provisional material (p < 0.01). Conclusion: The thickness of desensitizing agents affected the thermal changes; however, the desensitizers did not affect on the intrapulpal temperature although the type of provisional material used may be effective. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 91B: 362-365, 200