This study evaluated the fracture strengths, microleakage and stress distrubition of composite laminate veneers that were produced by two different types of composites and four different preparation techniques. Two hundred and fourty of Two hundred and fifty six caries-free human maxillary central incisors were randomly divided into eight experimental groups each containing of 30. The other sixteen teeth divided to use as control groups. Group 1 and Group 5 were designed with window type preparations, Group 2 and Group 6 with feather, Group 3 and Group 7 with bevel, Group 4 and Group 8 with incisal overlap preparations. A nanofil resin composite (Filtek Supreme XT) was used in Group 1, 2, 3 and 4 while using a nanohybrid resin composite (Clearfil Majesty Esthetic) in Group 5, 6, 7, and 8. Group 9 was the control and remained intact. Following to thermocycling of all specimens, one hundred and thirty-five were mounted in 10 cc syringes with acrylic resin. Shear bond strength test realized with universal testing machine by loading incisally and failure-loads (N) were determined for ?maksimum force? and ?break force?. Break force values of the study groups were different than maximum forces. Two-way analysis of variance (ANOVA) with Tukey post hoc multiple comparisons test and t-test was performed statistically (p<0.05). There were no significant differences between the composites (p>0.05) while the preparation techniques affected the failure loads of the laminate veneers for maximum forces significantly (p<0.05). Multiple comparisons revealed that failure loads of the samples prepared with incisal overlap were higher than those of the window and feather types of preparations (p<0.05).The rest one hundred and twenty-one specimen were immersed into basic fucsin, and then nitric acid solution for volumetric dye penetration test. Results determined by a spectrophotometer and statiscal analyses performed with two-way analysis of variance (ANOVA) and Tukey post hoc multiple comparisons test (p<0.05). There were no significant difference between the composite resins used in groups (p>0.05), but there were significant difference between the preparation techniques (p<0.05). Microleakage values were the highest at the Group 7 and Group 3, the lowest at the Group 1 and Group 5.To understand the influence of tooth preparation design on the stress distribution and localization of critical sites in maxillary central incisors restored by different techniques with two types of composite resins, 3D-finite element analysis was performed. A 3D maxillary central incisor model was created for all groups on the software to perform the influence of functional loading at the virtual context. When the composite area increased by adding the incisal edge to the preparation, finite element analyse showed that stress being has naturally increased. As we considered the results of the shear bond strength test, this is an expected result for the aforesaid groups to have reached the highest stress distribution.As a result of the investigation it was found that to include the incisal edge to the preparation of composite laminate veneers strengthens the restoration.Within the limitation of this study, the preparation techniques seem to affect the maximum failure load of the restorations. In addition to this results, we should say that ?the break force? values should be considered besides of ?the maximum force? values for the further studies.

Çalışmamızda, iki farklı tip kompozit ve dört farklı preparasyon tekniği ile hazırlanmış kompozit laminat venerlerin bağlanma dayanımları, mikro sızıntıları ve stres dağılımları incelendi. 256 adet çürüksüz insan üst santral kesici diş rastgele 8 gruba ayrıldı (n=30). Grup 1 ve 5 pencere tipi, Grup 2 ve 6 feather, Grup 3 ve 7 bevel, Grup 4 ve 8 insizal overlap preparasyonla hazırlandı. Grup 1, 2, 3 ve 4 nanofil; Grup 5, 6, 7 ve 8 nanohibrit rezin kompozitle restore edildi. Kalan 16 adet diş kontrol grubu olarak kullanıldı. Makaslama bağ dayanımı testinde örneklerin insizaline kuvvet uygulanarak ?maksimum force? ve ?break force? değerleri belirlendi. İki yönlü varyans analizi, t testi ve Tukey post-hoc testi kullanılarak istatistiksel analizler yapıldı (p<0.05). Kompozitler arasında anlamlı bir fark bulunmamışken (p>0.05), preparasyon tipleri arasındaki fark anlamlıdır (p<0.05). Grup 4 ve 8'de daha yüksek kırılma direnci bildirilmiştir (p<0.05).Boya penetrasyon testi için örnekler önce bazik fuksin, ardından nitrik asit solüsyonunda bekletildi. Sonuçlar spektrofotometre cihazı ile belirlendi. İki yönlü varyans analizi ile Tukey post-hoc testi kullanılarak istatistiksel analizler yapıldı (p<0.05). Kompozitler arasında anlamlı bir fark bulunmamıştır (p>0.05). Preparasyon tipleri arasındaki fark maksimum force'a göre anlamlıdır (p<0.05). Mikrosızıntı değerleri en yüksek Grup 7 ve 3'tedir.Üç boyutlu sonlu elemanlar analizi için yazılım programında gruplara ait üst santral diş modeli oluşturuldu. Preparasyon tipine insizal kenar dahil edilerek kompozit alanı arttırıldığında, stres oluşumunun da arttığı gözlendi. Makaslama bağ dayanımı testinde yüksek kırılma değerlerinin gözlendiği gruplarda stresin yüksek değerlere ulaşması beklenen bir sonuçtur.Araştırmamızda, kompozit laminat vener preparasyonlarına insizal kenarın dahil edilmesinin restorasyonu güçlendirdiği görüşüne vardık.