Effect of curing light sources on microleakage of class v resin based restorations

The purpose of this study is to investigate the effect of three different curing light sources with varying intensities on microleakage associated with class V resin -based restorations

Material and Methods: Thirty freshly extracted human premolars were cleaned and stored in 2% formaldehyde at 37° C for 24 hrs before cavity preparation. Standardized class V cavity preparations were cut on the buccal surfaces with occlusal margins on enamel and gingival margins on root dentin. Cavities were then treated with adhesives and restored using two resin-based restorative materials; Point-4 microhybrid composite resin [COMP] and Definite ormocer [ORM]. Three curing light sources with different light intensities; halogen light [HLC], plasma arc light [PAC], and light-emitting [LED] were used in this study. Specimens were divided into six groups of different curing light/restorative material combinations. Specimens were subjected to thermocycling for 600 cycles and were immersed in 1% methelyne blue dye for 24 hrs. Specimens were sectioned buc-colingually and examined under stereomicroscope at x20. Degree of dye penetration was scored at occlusal and gingival margins

Results: Kruskal-wallis non-parametric test indicated significant differences between groups at occlusal enamel margin [p < 0.027] and at gingival dentin margin [p < 0.026]. At the occlusal enamel margin, PAC /COMP showed the lowest dye penetration and PAC/ORM yielded the highest dye penetration. While at the gingival dentin margin, LED/ORM presented the lowest dye penetration and LED/COMP exhibited the highest dye penetration

Conclusions: Specimens cured with the three curing light sources included in this study exhibited microleakage. Occlusal enamel margins were associated with less microleakage than gingival dentin margins. Both microhybrid composite resin and ormocer exhibited microleakage where, in general, microhybrid composite resin showed lower degree of microleakage at occlusal enamel margins and ormocer was lower degree of leakage at gingival dentin margins. Specimens cured with plasma arc light showed the highest microleakage at occlusal enamel margins, while the lowest microleakage was associated with specimens cured with light-emitting diode at gingival dentin margins. CLINICAL SIGNIFICANCE: The combination of restorative material type and curing light source/intensity affect the marginal quality of the resin-based restorations and should be taken into consideration during the restorative procedure

Placement techniques of direct posterior composites in class II cavities and associated microleakage: a literature review

There are several techniques for placement of posterior composites in class II cavities some of which are old while others are recent. These are divided mainly into the bulk placement [one step] and the incremental placement [several steps]. There are several incremental placement techniques in Class II cavities that were introduced to overcome the clinical failures associated with the bulk technique. There was a significant difference in microleakage between bulk and incremental technique where there was a high microleakage associated with the bulk technique. However, there was no significant difference among the different incremental types in reducing the microleakage. Today's composite materials, though vastly improved, still have some drawbacks that must be overcome before they can replace amalgam as viable posterior restorative materials. Modifications of the tooth preparation and placement of composite resin may help diminish the inherent drawbacks

Reproducibility of the selected shade for indirect laminate veneers by using various shades of luting resins

The present study was performed to compare the reproducibility of each of the porcelain and composite laminates to the selected shade [A-2]. The effects of the laminate thickness [0.5 mm and 1 mm] and that of the luting resin shades on the final shade of the laminate samples were also investigated. This study was carried out on 84 laminate samples i.e 42 porcelain laminate samples [IPS Corum] and 42 composite laminate samples [Tetric Ceram]. The shade of the laminate materials [porcelain/composite] which was used in fabrication of laminate was A-2. Each laminate sample was square in shape with a side length 10 mm. Half of the laminate samples had 0.5 mm thickness while the other half of the samples had 1 mm thickness. All of the laminate samples were cemented to standardized acrylic substrates. The shade of the substrates was C-4. Cementation of the laminate samples to the substrates was done by using different shades [A-1, A-2, A-3.5] of Aeliteflo and Tetric Flow flowable composites. The color difference between each cemented sample and the A-2 vita lumen shade guide was measured by using a spectro-colorimeter. The porcelain laminate was found to be the most reproducible material to the selected shade, and the statistical analysis revealed that the difference in shade reproducibility was highly significant when compared with composite laminate martial. The laminate samples with 1mm thickness had superior reproducibility than the laminate samples with 0.5 mm thickness. Aeliteflo luting resin was more reproducible to the selected shade than Tetric how luting resin. There was a highly significant relation between the shade of the luting resin and the final shade of laminate

Influence of disinfection on elastomeric impression materials as measured by contact angles of die stone

Objectives: this investigation determines the effect on contact angles of die stone obtained from elastomeric impressions materials after immersion disinfection

Materials and method: three representative brands of commonly used elastomeric impression materials along with four types of disinfecting agents were used in this study. Contact angle measurements after disinfection of elastomeric impressions were recorded as a measure of wettability, at three time periods [15, 30 and 120 minutes], using the photographic method

Results: immersion disinfection of these materials rendered a general significant decrease in the contact angle values [P<0.01] as a function of the disinfection time and the disinfecting a period of disinfection yielded the greatest decrease in contact angles data indicating the best wettability. Polyether impression material showed significantly [P<0.01] the least contact angle data when immersed in chlorine dioxide

Conclusion: immersion disinfection of elastomeric impressions decreased the contact angle values and disinfecting solution. hence, an increase in their wettability occurred. The contact angle values varied as a function of disinfection time and disinfecting agent type