lindsay richards

Resin composites are common materials used to restore anterior teeth following root canal therapy, but are accompanied with shrinkage during polymerization. The aim of this in vitro study was to investigate the effect of the insertion method and polymerization shrinkage of resin composite on residual tooth structure.
Stereomicroscopy and computerized Finite Element Modelling (FEM) were used to compare residual stresses in endodontically treated, extracted maxillary central incisor teeth, in which the access cavities were restored with resin composite. Theoretical stresses derived from the FEM were analyzed during preparation and after teeth were restored using either a “bulk” or a “wedge incremental” method. These data were subsequently compared with stresses measured directly using strain gauges.
Results showed that intensive stresses, which had the potential to cause fracture in dental structures and composite de-bonding, were applied to teeth during polymerization.
According to the results of this study, the “bulk” build up led to less stress induction during restoration of teeth following root canal therapy.

Background and aim
Restorative dentistry searches the use of glass fiber-reinforced composite is just now experiencing rapid expansion in dentistry. This study compared of fracture strength a glass fiber-reinforced composite (GFRC) and a fiber-reinforced composite (FRC) as a framework for fabrication of resin-bonded fixed partial dentures (RBFPDs).
Methods and Materials
Twenty RBFPDs were made with GFRC (everStick) and FRC (Ribbond). The specimens were stored for 2 weeks at 37 1 C in distilled water, thermocycled (5-55C, x 2500) and statically loaded to fracture. The hounsfield testing machine measured fracture strength of the samples. Metal cone with tip 1 mm income vertically to central of labial surface of pontic with speed 1 mm/min. The force in Newtons was recorded at debonding of prothosis from abutment teeth and then SEM.
Results
The mean and standard deviation for fracture strength of GFRC RBFPDs were 440±75 and for FRC RBFPDs were 309±33. ANOVA showed that fracture strength between two groups were statistically significant (pv =0.000247). SEM examination revealed that debonding between the GFRC RBFPDs and the tooth and no debonding between the glass bundle and the composite.
Conclusion
On the basis of the results of this study, GFRC that can be used in the fabrication of 3-unit anterior FPDs.