No abstract

Mechanical failure of endocrown restorations does not significantly differ for silica-based ceramics modified either with zirconia or polymer.

Purpose An in vitro study to compare the marginal fit of cobalt‐chromium (Co‐Cr) metal copings fabricated with selective laser melting (SLM), computer‐aided design and computer‐aided manufacturing (CAD/CAM) milling, and lost‐wax (LW) techniques, on abutments with two different antirotational features. Materials and Methods A total of 60 stainless steel abutments with the same length and convergence angles were fabricated using a numerical control machining. Half of the abutments had one flat plane, while the other half had three grooves as an antirotation feature. Thirty abutments of each kind were then divided into three subgroups, and metal copings were fabricated with SLM, CAD/CAM milling, or the LW technique (n = 10). The metal copings were cemented with polycarboxylate cement. Marginal gap measurements were performed using a stereomicroscope at a magnification of × 45 and data were analyzed with two‐way analysis of variance (ANOVA) tests. Results The LW (p = 0.002) and CAD/CAM (p < 0.001) techniques exhibited increased marginal gaps on the abutments with a three groove antirotational feature; however, no significant difference was detected with the SLM technique (p = 0.259). The copings fabricated with the SLM technique demonstrated significantly lower gap values in both abutment types (p < 0.001). Conclusion While all marginal gap values were within the clinically acceptable range (<120 µm), abutments with more antirotational grooves exhibited wider marginal gaps with the LW and CAD/CAM techniques.

No abstract

Single-unit implant or tooth-supported zirconia crowns may be considered acceptable treatment modalities for restoration of either missing or compromised posterior teeth.

Background/purpose Advancements in digital dentistry and the development of intraoral scanners (IOS) have provided clinicians with an accurate and efficient alternative to analog impressions. The aim of this study was to assess the accuracy of the marginal and internal fit of 5-unit monolithic zirconia fixed dental prostheses (FDPs) fabricated with CAD/CAM technology using direct and indirect digitalization methods. Material and methods Three teeth in a maxillary typodont model were prepared to receive a 5-unit zirconia FDP. Six different groups were created according to the type of scanner (intraoral and extraoral) and the type of workflow. For direct workflow, the typodont was scanned with two different IOS (3Shape Trios 3 [3S-IOS] and Cerec Omnicam [C-IOS]). For indirect workflow, after conventional impressions were obtained, the impressions (IMP) were scanned with two different laboratory scanners (3S-IMP and C-IMP). After the impressions were poured, the stone (STN) casts were scanned with the same laboratory scanners (3S-STN and C-STN). Sixty 5-unit monolithic zirconia FDPs (10 in each group) were designed and milled. The marginal and internal fit was assessed. Results The mean marginal gap values were 78.2±9 μm in the IOS group, 82.6± 9 μm in the IMP group, and 82.6±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05). The mean axial gap values were 77.7 ± 10 μm in IOS group, 83.61 ± 15 μm in the IMP group, and 84.5±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05). Conclusion The marginal and internal fit of 5-unit monolithic zirconia FDPs fabricated with direct and indirect digital scans were similar. The smallest gap values were observed at the marginal region while the greatest gap values were detected at the occlusal region.

ÖZET GİRİŞAltmışbeş yaş üstü bireylerin popülasyondaki oranı her geçen gün artmaktadır. Farklı ülkelerde farklı sıklıkta gö-rülmesine rağmen, bu popülasyondaki bireylerde görü-len diş eksiklikleri ve alveol kemiklerinde oluşan rezorbsiyon da yaşlanma ile birlikte artış göstermektedir. Mevcut dişlerin çeşitli nedenlerle kaybı sonucunda tam dişsizlik kaçınılmaz hale gelmektedir. Geleneksel tam protez kullanan dişsiz hastalar fonksiyon sırasında özel-likle alt protezlerinin stabilitesinin ve tutuculuğunun yetersiz olması nedeniyle olumsuz tecrübelere sahiptirler. 1-3Daha önceleri konvansiyonel tam protezler, tam diş-sizliklerde sıklıkla en çok tercih edilen tedavi yöntemi iken günümüzde implant üstü overdenture'lar dişsizliğin giderilmesinde birinci seçenek olarak sunulmaktadır. 2İmplant üstü overdenture'lar ile konvansiyonel tam protezlerin karşılaştırıldığı çok sayıda çalışmada implant üstü overdenture kullanan hastalarda, çiğneme etkinliği, protez stabilitesi, protez retansiyonu ve estetiğin daha tatminkar olduğu ve buna bağlı olarak hasta memnuniyetinin çok daha fazla olduğu rapor edilmiştir.4-11 Alt çene tam dişsizlik durumunda implant destekli overdenture için maliyet ve hasta memnuniyeti dikkate alındı-ğında en az iki implanttan destek almak gerekmektedir. 2Ancak üst çenede implant destekli overdenture'lar için belirli bir implant sayısı belirtmeye yeterli kanıt literatürde bulunmamaktadır. [12][13][14] İmplant üstü overdenture'larda implant ile protez arasındaki bağlantı, hassas bağlantı yapısındaki bir tutucu sistem aracılığı ile sağlanmaktadır. Bu tutucu sistemler iki ana başlık altında toplanabilir.

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients (TECs), when zirconia ceramics were coloured at green stage. Zirconia blocks (N=240; 6 mm×7 mm×7 mm) were manufactured from two materials namely, ICE Zirconia (Group 1) and Prettau Zirconia (Group 2). In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid (shade A2). Three different veneering ceramics with different TEC (ICE Ceramic, GC Initial Zr and IPS e.max Ceram) were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys (Esteticor Plus) veneered with ceramic (VM 13) (n=16) acted as the control group. Core–veneer interface of the specimens were subjected to shear force in the Universal Testing Machine (0.5 mm⋅min−1). Neither the zirconia core material (P=0.318) nor colouring (P=0.188) significantly affected the results (three-way analysis of variance, Tukey's test). But the results were significantly affected by the veneering ceramic (P=0.000). Control group exhibited significantly higher mean bond strength values (45.7±8) MPa than all other tested groups ((27.1±4.1)−(39.7±4.7) and (27.4±5.6)−(35.9±4.7) MPa with and without colouring, respectively) (P<0.001). While in zirconia–veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering <1/3 of the substrate surface, in the metal–ceramic group, veneering ceramic was left adhered >1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core–veneer adhesion. Metal–ceramic adhesion was more reliable than all zirconia–veneer ceramics tested.