In vivo evaluation of occlusal wear of two experimental composites versus amalgam

Two experimental inhomogeneous microfilled composites with spherical prepolymerized particles and an interpenetrating network (IPN), which provides a stable bond between prepolymerized spheres and the matrix (B-21 and B-51), and amalgam were used for Class II MOD fillings in mandibular molars. After 3 and 6 months of clinical use, wear of the material was measured with a replica technique and a modified surface roughness test. The failure mode was analysed with SEM photographs also using a replica technique. After 6 months the wear of the composites in the occlusal contact area was more than twice as high as the substance loss of amalgam. It was concluded that the composites were not suitable for fillings bearing occlusal load. However, the failure mode seen in the SEM for B-21 indicated that the IPM leads to a stable incorporation of the spherical prepolymerized particles into the matrix. Due to its good surface characteristics B-21 should be further investigated for its use as an anterior composite. B-51 was especially designed as a posterior composite. Beside the construction elements of B-21 it contained also barium glass spheres to obtain radiopacity. This hybrid construction failed due its wear mode.     

Surface roughness and marginal behaviour of experimental and commercial composites: an in vitro study

Three experimental inhomogeneous microfilled composites (IMC) containing spherical prepolymerized particles with an interpenetrating network (IPN) were compared with the reference materials Estic MF, Adaptic and the amalgam Dispersalloy in vitro. With surface roughness tests, different polishing procedures were investigated. In addition an SEM analysis of the margins of Class I fillings using a replica technique was performed. With the same technique the proximal boxes of Class II fillings were analysed to further determine the best method to handle the materials clinically. The experimental materials showed a superior adaptation to the walls of proximal boxes of Class II cavities than the reference materials. This superiority was increased by the use of a filled bonding agent. The influence of viscosity, filler load and glass transition point on adaptation and polymerization shrinkage are discussed. It was concluded that especially designed diamonds with very fine abrasive particle size (40 micrograms and 15 micrograms) are the best for finishing and contouring composite fillings. Based on the results of this study it is recommended to use the experimental material for clinical investigations.     

Acute lymphoblastic leukaemia in childhood: cell proliferation without rest

The percentage of non-cycling blast cells in children with untreated acute lymphoblastic leukaemia (ALL) was investigated by staining smears for statin, a nuclear protein specifically present in non-growing resting cells. Results were compared with purified normal CD34-positive progenitors. A low fraction of ALL and CD34-positive cells expressed statin (2.0 ± 3.8% and 2.8 ±3.1%, respectively), the growth fraction assessed by staining for the nucleolar antigen p120 was 94% in both ALL and CD34-positive cell samples. From this analysis it can be concluded that the compartment of non-replicating cells in ALL as well as in normal CD34-positive precursor cells collected from peripheral blood is very small and that most cells are cycling.