Peter Portmann | PubMed Health

PubMed2005

Obturation quality after four years of storage using the non-instrumentation technique.

The aim of this in vitro study was to compare the sealing quality of three root canal filling materials after four years of ageing. Obturation with the non-instrumentation technique (NIT) was compared with cold lateral condensation of gutta-percha. Seventy-six canals were endodontically treated with traditional hand instrumentation and cold lateral condensation (control) whereas 77 canals were cleansed and obturated with NIT Three different sealers were used: AH 26, AH Plus and Apexit. After obturation, the teeth were stored for four years at 37 degrees C. Coronal dye penetration was evaluated after the teeth were made transparent. The teeth cleansed and filled with the new method showed significantly less dye penetration than the hand-instrumented teeth (p < 0.001). Within the hand-obturated group, Apexit showed significantly more dye penetration (4.7 +/- 0.71 mm) (p < 0.01) than AH Plus (1.83 +/- 0.57 mm) or AH 26 (1.16 +/- 0.4 mm). No significant differences were found within the NIT groups. This study showed NIT to produce root canal fillings with significantly less coronal leakage compared to the conventional technique after four years of storage in vitro.

Bismuth↗

PubMed2005

[Composite curing with new LED equipment].

Standardized holes ("cavities") measuring 4 mm in diameter and 8 mm in depth were prepared using plexiglass cubes. The following LCUs were tested: Astralis 10 Halogen light curing units (LCU), Bluephase, Elipar Freelight 2 and SmartLite LED LCUs. Each LCU was examined according to the following test conditions. Light exposure time of 20 s and 40 s. Polymerization directly onto the composite, with a distance of 4 mm or through a 3 mm thick ceramic disk, respectively. The composite Tetric Ceram (A3) was inserted in one batch and after a seven-day incubation period the cubes were sectioned into two halves and polished. Knoop microhardness was determined 100, 200, 500, 1000, 1500, 2500, 3000, 4000, 5000 and 6000 microm from the occlusal surface. The total degree of polymerization of a composite specimen for any given curing time and curing light was determined by calculating the area under the hardness curve. Multiple linear regression revealed that the distance of the light tip from the composite, curing time and the LCU had a significant association with the degree of polymerization (p < 0.001). The same pattern of cure profile was shown by all LCUs during the course of the test. The hardest composite was usually encountered around 200 microm from the occlusal surface. It was concluded that without irradiation through ceramic and a light tip close to the composite a light exposure time of 20 s will sufficiently polymerize an increment of at least 2 mm. Polymerization through ceramic needs a curing time of 40 s from each side.

Ceramics↗