In Vitro Effect of Vent Size and Spacer Thickness on Pressure Produced during Maxillary Edentulous Impression Making by Different Impression Materials

Abstract

Background and Aim: Microleakage is a drawback of composite restorations and it is more noticeable in dentinal walls. Despite advances in dentin bonding agents, no adhesive can completely eliminate microleakage and provide a hermetic seal. This study aimed to compare microleakage of three resin bonding agents namely a universal adhesive, two-step self-etch system and two-step total-etch system. Materials and Methods: This in vitro, experimental study was conducted on 68 human molars. Class V cavities were prepared in the buccal or lingual surfaces of the teeth with occlusal margins in the enamel and gingival margins in dentin. The teeth were then randomly divided into four groups of 17. Group A: Adper Single Bond 2, group B: Clearfil SE Bond, group C: Scotchbond Universal adhesive (self-etch) and group D: Scotchbond Universal adhesive (total-etch). The teeth were then restored using different bonding agents and a microhybrid composite resin. The specimens were then subjected to 1000 thermal cycles between 5-55°C. The entire restoration surface except for 1mm around the margins was coated with nail varnish. The teeth were immersed in 2% methylene blue for 24 hours and sectioned longitudinally in a buccolingual direction and observed under a stereomicroscope to determine microleakage. Microleakage in use of the three bonding agents was compared using the Kruskal Wallis test (P<0.05). Results: Based on the Kruskal Wallis test, no significant difference was noted in enamel and dentin margins among different adhesives but the enamel margin showed less microleakage than the dentin margin. Conclusion: Different adhesive systems tested in this study showed similar microleakage at the enamel and dentinal margins.

Clinical Negative Pressure Measurement after Border Molding Procedure

“…It decreases by almost 50% during the pressure of 0.5 kg. 6 In a similar study, with a pressure of 1 kg/cm 2 the decrease was more than 80%. 7 Selection of impression materials depends on the anatomical features of the prosthetic field.…”

“…1 This new method can be used after elastification or hardening of the impression material, therefore we couldn't measure the pressure in different phases of the elastification reaction. 6,7 The anatomical features of the prosthetic field are very important for the pressure creation. According to our study the difference between the pressure, created with tested impression materials on the same patient was from -0.05 to -0.1 bars.…”