Aim: To compare the marginal adaptation of crowns fabricated by using three different resin-ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) materials. Materials and Methods: Crowns fabricated from three different resin-ceramic CAD/CAM blocks, applied on a typodont premolar (#14), were tested with regard to marginal adaptation, in this in vitro study. The typodont maxillary first premolar was prepared to serve as the master die and digitized with an intraoral scanner. The same virtual crown design was used to fabricate all specimens. Forty-eight crowns were fabricated from the same virtual crown design using three different CAD/CAM resin-ceramic blocks as follows ( n = 16): Lava Ultimate (LU), GC Cerasmart (GC), Vita Enamic (VE). Master die and crowns were scanned with a laboratory scanner and three-dimensional data were transferred into three-matic software. The software calculated the mean of the marginal discrepancy (MD) for each crown in negative and positive values, representing under and over estimation of the crown margin, respectively. A marginal discrepancy index (MDI) was obtained for each group using negative and positive MDs. All data were statistically analyzed using one-way analysis of variance and Tukey’s honest significance test ( α = 0.05). Results: The analysis of variance showed no statistical differences between materials regarding the negative and positive MDs ( P > .05). The MDI for LU was lower than GC and VE ( P < .05). Conclusion: The marginal adaptation of different resin-ceramic materials was different with regard to MDI values. Nevertheless, the MD values of all groups were within the clinically acceptable range.
The aim of this study was to evaluate the effect of multiple firings on the bond strength between yttriatetragonal zirconia polycrystals (Y-TZP) and 2 types of resin cements. MATERIALS AND METHODS. Sixty 3Y-TZP specimens (LAVA Frame Multi) were divided into 3 groups depending on the following firing procedures: (1) 2-firing cycles, (2) 5-firing cycles, (3) 10-firing cycles. Two samples from each group were investigated by using SEM to determine the morphological changes. All specimens were treated with 125 μm airborne-particle abrasion and the surface roughness of each specimen was measured. The specimens from each firing group were then further divided into 2 subgroups (n = 9) to apply 2 types of resin cement (MDP-free resin cement: RelyX Unicem-RU, and MDP containing resin cement: Panavia F 2.0-PA). The shear bond strength (SBS) test was performed and failure types of all the debonded specimens were classified by using a stereomicroscope as adhesive, cohesive, and mixed. The statistical analysis of surface roughness and SBS data were performed by using 1-way ANOVA and 2-way ANOVA followed by Tukey-HSD tests (α=.05). Failure modes were calculated as a percentage for each group. RESULTS. The bond strength of RU and PA to the specimens obtained with 2 firings were not statistically different from each other (P=.1). However, the SBS values of PA were found to be significantly higher than RU for the specimens obtained with 5 and 10 firing cycles (P=.001 and P=.02, respectively). Surface roughness analysis revealed no statistical difference between groups (P=.2). The SEM analysis of samples fired 5-and 10-times showed irregularities and boundary loss in zirconia grains, and empty spaces between zirconia grains. CONCLUSION. The bond strength of PA cement was higher than that of RU to the zirconia subjected to repeated firings (5 and 10 firing cycles). When zirconia is subjected to multiple firings, using MDP-containing resin cement can be recommended.
Bruksizm; genel kabul gören haliyle dişlerin okluzal yüzeyleri arasında non-fonksiyonel ve sürekli, kuvvetli temas olarak tanımlanır; çiğneme sisteminin non-fonksiyonel hareketleri esnasındaki istemsiz, aşırı gıcırdatma (grinding), dişlerin sıkılması (clenching), veya sürtünmesidir (rubbing). Hayatı tehdit edici bir rahatsızlık olmamasına karşın, insan yaşamının kalitesini dental problemler ve orofasiyal bölgedeki ağrı ile etkileyebilir. Günümüzde bruksizmin altında yatan nörokimyasal mekanizmalar tam olarak anlaşılamamıştır. Bununla birlikte, stres ve kişilik özellikleri gibi psikososyal faktörlerin de bruksizm etiyolojisinde önemli olduğu bildirilmiştir. Diş gıcırdatma periyodları kısa aralıklarda olmasına rağmen çiğneme sisteminde ciddi problemlere neden olabilmektedir. Bruksizm sonucu temporomandibular rahatsızlıklar, baş ağrısı, dişlerde aşınma, hassasiyet ve mobilite gibi problemler görülebilmektedir. Yıllar içinde bruksizmi durdurmak için protetik tedavilerde dahil olmak üzere birçok tedavi yöntemi denenmiştir ancak bruksizmi daimi olarak elimine eden bir tedavi yöntemi henüz bulunmamaktadır. Her ne kadar oklüzal ısırma plakları ile bruksizmin zararlı etkileri önlense de etkinliğinin net olarak gösterildiği kanıta dayalı çalışmalar bulunmamaktadır ve oklüzal tedavi bitirildiğinde uzun dönemde bruksizm tekrarlayabilir. Bu derlemede bruksizmin oluş nedenleri ve güncel tedavi yaklaşımları literatür bilgileri ışığında tartışılmıştır.
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