Stress-reduced Direct Composites for the Restoration of Structurally Compromised Teeth: Fiber Design According to the "Wallpapering" Technique.

PURPOSE: The purpose of this work was to present a restoration technique based on an understanding of the biomechanical properties of the dentinoenamel complex (DEC) and the physical-mechanical properties of the resin-based composite including the stress generated from both polymerization shrinkage and occlusal forces. Technique Summary: The DEC is a functional interphase that provides crack tip shielding; the DEC should be preserved during restorative procedures. Dentists can design the strategic placement of restorative materials into the cavity to both resist the mode of failure and mimic the performance characteristics of the intact natural tooth. The term "wallpapering" describes a concept of covering the cavity walls with overlapping closely adapted pieces of Leno weaved ultra-high-molecular-weight polyethylene (LWUHMWPE) ribbons. The key for success is that the ribbons are adapted and polymerized as closely as possible against the contours of residual tooth substrate. The resulting thin bond line between the fibers and the tooth structure creates a "bond zone" that is more resistant to failing due to the intrinsic stress and energy absorbing mechanism of the LWUHMWPE ribbons. The formation of defects and voids, from which crack propagation may start, is also reduced. The fibers' tight adaptation to tooth structure allows a dramatic decrease of the composite volume between the tooth structure and the fiber, thus protecting the residual weakened walls from both the stress from polymerization shrinkage and the occlusal load. CONCLUSION: By using a similar approach, fiber-reinforced stress-reduced direct composite restorations may be performed in the restoration of structurally compromised vital and nonvital teeth.

Clinical evaluation of stress-reducing direct composite restorations in structurally compromised molars: a 2-year report.

OBJECTIVE: To evaluate the clinical performance of class II large-size direct composite restorations. MATERIALS AND METHODS: Fifty (50) patients 18 years or older were included in this clinical trial restoring 75 vital molar teeth with large-size cavities. INCLUSION CRITERIA: Occlusal extension greater than two-thirds the intercuspal distance and proximal extension greater than half the distance between line angles. Teeth with residual cavity walls less than 1 mm and with one or more cusps involved were excluded. Teeth were randomly divided in three groups. Group 1: Opti-Bond FL; group 2: Scotchbond 1 XT; group 3: PQ1. Total-etching was performed using 35% phosphoric acid followed by the application of 2% chlorhexidine gluconate in the three groups. All teeth were restored using Vit-l-escence microhybrid composite resin. The proximal surface was built up first, followed by dentin and enamel occlusal surface stratification; wedge-shaped increments of composite resin were placed and cured using the UltraLume V curing light through a combination of pulse and progressive curing techniques. RESULTS: Restorations were evaluated at six-month intervals during the two-year period using a modified US Public Health Service criteria by two independent evaluators precalibrated at 85% reliability. No failures were reported and α scores were recorded for all parameters. Statistical analysis was performed using a χ(2) test and the Fisher exact test (χ(2)=10.6; p=0.001). No teeth exhibited sensitivity in the three groups both at the two-week recall and two-year follow-up.

Determination of methadone and its primary metabolite in human urine by capillary electrophoretic techniques.

Data presented in this paper show that methadone and its primary urinary metabolite (M1) can not easily be determined by SDS-based micellar electrokinetic chromatography; however, they separate rapidly under cationic capillary zone electrophoretic conditions using a borate buffer with a pH of ca. 9. Eight urines obtained from individuals undergoing methadone therapy, which tested markedly positive for methadone using an enzyme multiplied immunoassay and in which the presence of methadone and M1 was also confirmed by GC-MS, have been analyzed. Using an extraction procedure with disposable cartridges containing a copolymeric sorbent, the presence of methadone and M1 could be confirmed in all urines, whereas with direct urine injection, the two compounds could only be determined in six urines. Thus, for unambiguous confirmation by capillary electrophoresis, extraction of the compounds of interest is preferred. The described assay is rapid (with typical run times being less than 6 min), free of interferences from coextracting drugs of abuse and/or their major metabolites, and characterized by a good reproducibility. After extraction of 5 ml urine, drug concentrations down to ca. 20 ng/ml can be monitored unambiguously.