Bond strength and interfacial characterization of eight low fusing porcelains to cp Ti.

OBJECTIVES: The aim of this study was the interfacial characterization and the determination of bond strength of commercially available low fusing dental porcelain for Ti. METHODS: Eight materials were included in this study: Duceratin, Duceratin Plus, Initial Ti, Ti-22, TiKrom, TitanKeramik, Triceram (powder) and Triceram (paste). Eight ISO 9693 bond characterization specimens from each porcelain were prepared according to manufacturers' instructions. One specimen from each group was embedded in acrylic resin and after metallographic preparation was studied under an SEM. Interfacial characterization was carried out with Backscattered Electron Imaging and X-ray EDS analysis operating in line scan mode. Metal-ceramic specimens were tested in three point bending at a crosshead speed of 1.5mm/min according to ISO 9693 requirements. Additionally the fracture mode (adhesive-cohesive) of all specimens was evaluated employing SEM/EDS analysis. The results of bond strength and adhesive percentage were statistically analysed with one-way ANOVA and SNK multiple comparison test (a=0.05). Additionally the possible correlation between the bond strength and fracture mode was also tested using Pearson test. RESULTS: Interfacial characterization showed the mutual diffusion of Ti, Si, O and La along the Ti-ceramic interface. Only in Tricerap (paste) Zr showed an increased concentration at the interface. The results of bond strength classified the materials in the following decreasing order: TiKrom>Duceratin>InitialTi>Duceratin Plus>Ti-22>Triceram(paste)>Triceram(powder)>TitanKeramik. No correlation (r=0.132) between the fracture mode and bond strength of the selected material denoting that the fracture mode is irrelevant with the bond strength of Ti-ceramic joint and thus the former should not be applied for comparison among different materials. SIGNIFICANCE: According to the results of this study the materials tested provided great difference in interfacial analysis and bond strength with metallic Ti.

Marginal and internal adaptation of Class II ormocer and hybrid resin composite restorations before and after load cycling.

To overcome the shortcomings of the conventional composite restorative materials, ormocer materials have been introduced over the past few years. The purpose of this study was to evaluate the marginal and internal adaptation of two ormocer restorative systems (Admira, Voco and Definite, Degussa) compared to a hybrid composite one (TPH Spectrum, Dentsply/ DeTrey), before and after load cycling in Class II restorations. Standardized Class II restorations with cervical margins on enamel were divided into three groups ( n=16). Teeth of each group were filled with one of the restoratives tested and its respective bonding agent. Each group was divided into two equal subgroups. The marginal and internal adaptation of the first subgroup was evaluated after 7-day water storage at room temperature and of the second after cyclic loading in a mastication simulator (1.2x10(6) cycles, 49 N, 1.6 Hz). The occlusal and cervical marginal evaluation was conducted by videomicroscope and ranked as "excellent" and "not excellent". One thin section (150 microm), in mesial-distal direction, of each restoration, was examined under metallographic microscope to determine the quality of internal adaptation. The occlusal and cervical adaptation of both ormocer restorative systems was similar and clearly worse compared with the hybrid composite restorative one before as well as after load cycling. Concerning internal adaptation, no gap-free ormocer restorations were detected, whereas all Spectrum restorations presented perfect adaptation. The bonding agents of the ormocers formed layers with unacceptable features (pores, fractures) whereas that of the hybrid composite achieved perfect bonding layer even after loading. The rheological characteristics of the bonding agents of the ormocer restorative systems are proposed to be responsible for their inferior marginal and internal quality in Class II restorations compared with the hybrid composite one.