Mandibular 2 implant destekli overdenture protezlerde ataşmanlar üzerine gelen streslerin değerlendirilmesi

Objectives: The aim of this study was to evaluate the effect of implant locations on the stress around the two different attachment systems in mandibular two-implant overdentures.Materials and Methods: The data obtained from Visible Human Project were modified with the use of VRMESH and Rhinoceros 4.0 software to establish a 3D mandible model with 2 mm cortical bone covering the trabecular bone and 2 mm mucosae. 3D models (totally 6 models) of mandibular two-implant overdenture were designed according to different implant locations [lateral-lateral(LL), lateral-canine(LC), lateral-first premolar(LP)] and attachment systems [ball(BA), locator(LA)]. Foodstuff was used for occlusal loading (100N) and to simulate different biting configurations, foodstuff was positioned on incisors (anterior) and between the second premolar and first molar (posterior) bilaterally. The finite element analysis was performed by ALGOR FEMPRO software and von Mises stresses on attachments were evaluated.Results: For symmetric configuration (LL), there was more von Mises stress on BA compared to LA when foodstuff was positioned posteriorly. For asymmetric configurations (LC and LP), when the implant in the asymmetric side was positioned more posteriorly, von Mises stresses increased on both BA and LA of the implant positioned in the opposite side. In LC configuration, on BA higher von Mises stresses detected when compared to LA, whereas in LP configuration the higher stresses determined on LA when foodstuff was positioned posteriorly.Conclusions: In LL and LP configurations, LA showed lower stresses, which should lead the clinician to choose the appropriate attachment system according to the individual clinical situation.  ÖZETAmaç: Bu çalışmanın amacı, mandibular 2 implant destekli overdenture protezlerde farklı lokalizasyonlarda yerleştirilmiş implant üzerindeki 2 farklı tip ataşmana gelen streslerin değerlendirilmesi.Gereç ve Yöntem: “Visible Human Project” dataları VRMESH ve Rhinoceros 4.0 yazılımlarıyla, 2 mm mukoza ve 2 mm kortikal tarafından çevrelenmiş trabeküler kemik özelliklerine sahip 3 boyutlu (3B) mandibular modeli oluşturuldu. Mandibular 2 implant destekli overdenture protezi simüle eden 3B modeller (toplam 6 adet) farklı implant lokalizasyonları ve farklı ataşman sistemleri kullanılarak tasarlandı. Modeller üzerine oklüzal yüklemeler (100N), yarım yuvarlak sert materyal(YYSM) ile farklı fonksiyonel hareketleri (çiğneme, ısırma) simüle edebilmek için farklı konumlardan yapılmıştır. Sonlu elemanlar analizi ALGOR FEMPRO yazılımı ile yapılıp, ataşmanlara gelen stresler Von Mises değerleri ile değerlendirilmiştir..Bulgular: Simetrik lokalizasyonlarda (LL), posterior bölgeden yapılan yüklemeler sonucunda BA’ya gelen stresler LA’ya gelen streslerden daha fazladır. Asimetrik konfigürasyonlarda (LC ve LP), sol taraftaki implant posteriora doğru konumlandıkça, diğer tarafta bulunan implant üzerindeki hem BA hem de LA’da Von Mises stresleri artmıştır. YYSM posterior yerleştirildiğinde, LC konfigürasyonunda BA’da, LA’ya göre daha yüksek Von Mises stresleri gözlenirken, LP konfigürasyonlarda LA’da daha yüksek stresler tespit edilmiştirSonuçlar: LL ve LP konfigürasyonlarında, LA daha düşük stres değerleri göstermiştir. Bu sonuç, klinisyenlere implant destekli overdenture protez yaparken seçecekleri ataşman türü hakkında öncülük edecektir

Standards of CentroGraphic Analysis in an Anatolian Turkish Population

Aim:The aims of this study were to evaluate different facial-form assessment concepts (conventional numeric cephalometric approach and geometric centroid-oriented individualized cephalomorphic approach), to establish cephalomorphic norms from lateral cephalograms of Anatolian Turkish young adults, and to identify possible gender differences between Anatolian Turkish young men and women.Materials and Methods:The subjects included 28 Turkish men (mean age, 24.33±1.66 years) and 40 Turkish women (mean age, 23.12±2.24 years) ranging from 20 to 31 years old. Conventional cephalometric analysis and CentroGraphic analysis were applied to each lateral cephalogram. To determine the errors associated with radiographic measurements, 20 radiographs were selected randomly. Their tracings and measurements were repeated 8 weeks after the first measurements. A paired sample t test was applied to the first and second measurements. An independent-samples t test was performed for statistical evaluation of gender differences.Results:Generally, some differences were observed, but most of the values for skeletal measurements in Anatolian Turkish adults for cephalometric analysis were found to be similar to the ideal norms of different authors. According to statistical analysis, cephalometric and cephalomorphic measurements were similar for men and women, except facial centroid (FC) value. The FC value for women was statistically greater than that for men (p<0.05) CentroGraphic analysis results show that Anatolian Turkish adults have protrusive mandibular and retrusive upper lip.Conclusions:It is appropriate to put these practical CentroGraphic norms into daily orthodontic practice when an Anatolian Turkish population is being treated

Effect of Implant Height Differences on Different Attachment Types and Peri-Implant Bone in Mandibular Two-Implant Overdentures: 3D Finite Element Study

Implant-supported overdentures with self-aligning attachment systems are preferred to improve the stability and retention of complete dentures. The positioning of the implant attachments is a very important aspect of two-implant overdentures in obtaining better stress distribution. Therefore, the objective of this study was to compare two different attachment systems in a two-implant overdenture by evaluating the stress distributions in peri-implant bone and stresses on the attachments with positioning at different height levels using the 3D FEA method. Six models with ball attachments and 6 models with locator attachments—totaling 12 models (including 2 controls)—with the left implant positioned unilaterally at different height levels were subjected to 3 loading conditions (anterior, right posterior, and left posterior). Data for Von Misses stresses were produced numerically, color coded, and compared among the models for attachments and peri-implant cortical bone. The configurations in which implants presented 3 mm height differences in the bone level showed the most successful results in the peri-implant bone. When stresses on the attachments were compared, greater stress values were obtained from the ball attachments. As a conclusion, the configurations with a considerable (3 mm) height difference between quadrants of the mandible in the anterior segment showed the most successful results in the peri-implant bone. On the contrary, peak stress values around the implant observed from the models with less (1 mm) bone height difference may require leveling of the bone during surgery. However, these findings should be corroborated with clinical studies.</jats:p

Accelerated aging effects on surface hardness and roughness of lingual retainer adhesives

PubMedID: 18193969Objective: To test the null hypothesis that accelerated aging has no effect on the surface microhardness and roughness of two light-cured lingual retainer adhesives. Materials and Methods: Ten samples of light-cured materials, Transbond Lingual Retainer (3M Unitek) and Light Cure Retainer (Reliance) were cured with a halogen light for 40 seconds. Vickers hardness and surface roughness were measured before and after accelerated aging of 300 hours in a weathering tester. Differences between mean values were analyzed for statistical significance using a t-test. The level of statistical significance was set at P .05). Conclusions: Accelerated aging significantly increased the surface microhardness of both light-cured retainer adhesives tested. It also significantly increased the surface roughness of the Transbond Lingual Retainer. © 2008 by The EH Angle Education and Research Foundation, Inc