New processing techniques for denture base acrylic resins have been introduced which have not comparatively quantified the residual monomer content. While proper processing keeps the residual monomer in a tolerable range for most patients, tissue irritation and reaction due to potentially higher residual monomer in these alternative techniques could be a clinical concern. Decreased degree of conversion may influence physical properties as well as biocompatibility. This investigation evaluated the residual monomer content of acrylic resins cured by three different polymerization modes. Materials (polymerization system) evaluated were: Lucitone 199 (conventional process), Accelar 20 (rapid boil-out), and Acron MC (microwave). Fourier transform infrared spectrometry (FTIR) was employed to determine the degree of conversion. All curing methods produced similar results (Lucitone 199 = 92.7% (0.21), Acron MC = 92.6% (0.57), Accelar 20 = 90.9% (0-73). Conversion for Accelar 20 (rapid boil-out technique), though statistically different (P < 0.05, ANOVA) from the other two materials and polymerization techniques, was only slightly less. It is unlikely that the rapid boil-out technique would induce more adverse tissue responses than the other techniques included in this study.

Many endodontic sealers contain constituents that have been shown to inhibit the polymerization of resin cements. This may be important when prefabricated posts are cemented at the same appointment as root canal obturation. This study evaluated the effects of cementing posts with a resin cement immediately or at a delayed time period after obturation using Roth's 801 Elite Grade or AH26 sealer cements. The contribution of mechanical post-space preparation was also assessed as a critical variable. One hundred twenty extracted canines were randomly divided into eight experimental groups. The variables evaluated were the order of post preparation (either before or after obturation), the type of sealer used, and the time of post cementation. All teeth received a stainless steel #6 Parapost XP cemented with a resin cement, Panavia 21. Each experimental group underwent tensile testing for retention using an Instron universal testing machine. For both sealers posts cemented in teeth in which the canal was obturated before post-space preparation and thus had sealer-contaminated dentin removed by the space preparation procedure had significantly higher retentive values than those obturated after post-space preparation in which contaminated dentin might remain. Sealer used and time of cementation had no specific effect on retention. Achieving a clean, "freshened" dentinal surface during mechanical post-space preparation seems to be a critical variable for post retention when a resin cement is used.

In all cases, tooth shade was the most important factor, followed in sequence by unrestored natural teeth and number of teeth displayed. No correlation was found to exist between specific demographic groups and smile variables.

High flexural strength is a desirable property for denture base resins. Currently there is a lack of published studies evaluating the physical properties of newer denture bases such as the CAD/CAM milled bases. The purpose of this study was to compare the flexural strength of three different denture base resins fabricated by compression molding, injection molding, and pre-polymerized CAD/CAM milling. Three groups of ten PMMA acrylic denture base resins were processed into rectangular plates for total sample size of thirty (n=30). The groups differed in their method of processing and resin composition. The three groups were injection molded (SR-Ivocap High Impact, Ivoclar Vivadent), compression molded (Lucitone 199, Dentsply), and pre-polymerized CAD/CAM milled resins (Avadent Digital Dentures). Following storage in water for one week, flexural strength was measured using a 3-point bend test until failure. Kruskal-Wallis and Mann-Whitney tests were used for statistical comparison between groups. Significant differences in flexural strength was observed among the groups tested. The flexural strength of the pre-polymerized CAD/CAM milled acrylic resin group was higher than that of conventional method groups of compression molded and injection molded. The compression molded group exhibited higher flexural strength than the injection molded group. The results suggest that pre-polymerized milled denture bases may be a useful alternative to conventionally processed denture bases in situations where increased bending forces are anticipated.

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Higher-concentration carbamide peroxide bleaching agents, used as intended by the manufacturer, pose no significant risk to resin composite restoration surfaces.

The purpose of this study was to determine the effect of ultrasonic vibration on the force required to remove prefabricated posts. Ninety-six extracted human canines were divided into eight groups, which were prepared and obturated with gutta-percha and either a eugenol-containing (Roth's 801 Elite) or eugenol-free (AH26) sealer. Titanium #6 Parapost XH posts were cemented with either zinc phosphate or Panavia 21 resin cement. One half of the sample was subjected to ultrasonic vibration for 16 min at the post-dentin interface, whereas the other half received no vibration (controls). Each combination of sealer, cement, and vibration status was subjected to tensile load to failure using an Instron testing machine. Posts cemented in teeth obturated with gutta-percha and AH26 sealer demonstrated significantly greater resistance to dislodgement, compared with teeth obturated with gutta-percha and Roth's 801 Elite sealer. There was no statistical difference in retention of posts cemented with either zinc phosphate or Panavia 21, regardless of the sealer used. Additionally ultrasonic vibration increased post retention for both cements.