6,7 The roughness of intra-oral hard surfaces and free energy have a significant effect on primary adhesion and oral micro-organism retention. A surface roughness of 0.3 mm can be felt by the tongue, thus having a negative www.selleckchem.com/products/MLN-2238.html impact on patient comfort.8 In vitro studies regarding surface roughness for bacterial plaque retention have shown that an average surface roughness above 0.2 mm in fixed restorations increases the level of bacterial retention.8�C10 The aim of this study was to investigate surface roughness in provisional crown resins, after polishing, reinforced with different concentrations of glass fibers. MATERIALS AND METHODS Generally used and commercially available autopolymerizing resin was used in this study for provisional crown and fixed partial restoration (Dentalon Plus, Heraeus, Kulzer GmbH, Wehrheim, Germany).
The manufacturers recommended powder/liquid ratio was 2 grams of powder to 1 ml of liquid. Four different glass fiber groups in different concentrations were established, according to the powder to liquid mixture; Group A (no fiber), Group B (0.5%), Group C (1%) and Group D (2%), each group containing 12 disk specimens. A teflon mold was made in order to produce disk-shaped specimens (10 mm �� 2 mm). The unprocessed glass fibers were then cut to a length of 3 mm and kept in a predetermined amount of monomer. The provisional crown acrylic was mixed in the light of the manufacturer��s recommendations and added to the glass fiber mixture in predetermined quantities. The provisional resin paste added to glass fiber in desired concentrations was kneaded manually for 40 seconds and placed in the mold.
This was then placed in a hydraulic press (Rucher PHI, Birmingham, UK) and pressure slowly applied in such a way as to permit excess resin to escape. Pressure of 20 psi (140 kPa) was applied for 5 minutes. Once polymerization had been completed, the specimens were removed from the mold and analyzed with regard to air bubbles and size. Defective specimens were excluded from the study, and 48 specimens were obtained. All specimens were abraded for 10 seconds in a wet environment by means of a 300 rpm polishing device (Beuhler, Meta serv, Dusseldorf, Germany) using 600 grit sandpaper. All specimens were then polished for 15 seconds using a polishing machine with pumice mixed at a level of 2 g/2 ml.
Finally, diamond polishing paste was applied using a polishing device at 15,000 rpm. All polishing was performed by a single operator. Following the polishing process all specimens were washed in distilled water and left in an ultrasonic bath for 10 minutes. An Brefeldin_A average surface roughness value (Ra) from 4 randomly selected points on the surface was calculated using a profilometer (Mitutoyo Surf test 201, Japan). A 7.5 mm field was scanned at every measurement using the profilometer with a study gap of 250 ��m. Forty-eight pieces of data (12 �� 4) were obtained from each group, giving a total of 192 (Table 1).