This study evaluated the influence of fiber inserts, type of composites, and location of the gingival seat on microleakage in Class II resin composite restorations. Fifty noncarious human third molars were selected for the study. Standardized Class II box type cavities were prepared on the mesial and distal side of 45 teeth. The gingival margin was placed above the cementoenamel junction (CEJ) on the mesial side and below the CEJ on the distal side. The remaining five teeth received no cavity preparations. The prepared samples were divided randomly on the basis of type of composite and presence or absence of fiber inserts, into four experimental groups of 10 teeth each and two control groups of five teeth each. The groups were defined as follows: group I (n=10) - Z350 XT; group II (n=10) - Z350 XT with fibers; group III (n=10) - P90; group IV (n=10) - P90 with fibers; and group V (n=5) - positive controls, cavities were not restored; group VI (n=5) - negative controls, no cavities were prepared. The samples were stored in distilled water in incubator at 37°C for 24 hours and then subjected to 500 cycles of thermocycling (5°C and 55°C) with a dwell time of 15 seconds. They were then placed in a 2% methylene blue dye solution for 24 hours at 37°C. Samples were sectioned longitudinally and evaluated for microleakage at the occlusal and gingival margin under a stereomicroscope at 20× magnification. Kruskal-Wallis and Mann-Whitney U-tests were used to compare the mean leakage scores. Restorations with gingival margins in enamel showed significantly less microleakage. Significant reduction in microleakage was observed in groups restored with P90 composite than those restored with Z350 XT. No improvement in microleakage was observed with the use of fiber inserts (p>0.05).

INTRODUCTIONRehabilitation of partially edentulous patients using fixed partial denture (FPD) is a well-established treatment protocol since many decades. These FPDs require a laboratory phase of fabrication that varies from days to weeks. A dimensionally stable, strong, and accurate interim restoration is an important component of this treatment modality. These interim restorations provide pulpal protection, positional stability, occlusal function, strength, and aesthetics.Polymethylmethacrylate (PMMA) is the most common material used to fabricate interim FPDs. This material lacks sufficient strength and hence various methods are being used for reinforcing it in the past like glass fibres, carbon fibres, kevlar fibres, polyethylene fibres, and stainless steel wire.1-4 To date, little information is available in the literature on fracture resistance of reinforced PMMA temporary crown and bridge materials. It is also not clear as to how the site of placement of fibre reinforcement, influences the fracture resistance of temporary crown and bridge materials. Therefore, this study was undertaken to evaluate the fracture resistance of interim FPDs using different types of fibre reinforcements and also to determine the most appropriate site of reinforcement of interim FPDs fabricated from PMMA. MATERIALS AND METHODThis study was designed in two stages. In the first stage various methods of reinforcement for interim FPDs made up of PMMA were evaluated. During the second stage, favourable sites of placement to strengthen the interim FPDs were evaluated. There were five groups of ten samples each namely the group 1 (unreinforced, control group), group 2 (glass fibrereinforced), group 3 (polyethylene fibre-reinforced), group 4 (glass and polyethylene mixed fibre) and group 5 (stainless steel reinforced).Samples were tested for fracture resistance in an Instron universal testing machine. The maximum load causing the initial fracture and fracture resistance were calculated. The mean and standard deviation for each group were determined. The data was analysed for differences using one way analysis of variance (ANOVA) (The Tukey's standardised range test) to An evaluation of fracture resistance of interim fixed partial denture fabricated using polymethylmethacrylate and reinforced by different fibres for its optimal placement: an in vitro study Col

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Introduction Provisional restoration is a critical component of fixed prosthodontics treatment, which must satisfy many inter-relative factors such as biological, mechanical, and esthetic. These restorations should have accurate marginal adaptation and optimum strength to maintain functional demands. The present “in vitro” study was conducted to evaluate the effect of water temperature and duration of immersion, on the marginal adaptation and microhardness of four different commercially available provisional restorative materials. Materials and Methods The 240 specimens were then seated on the stainless-steel die which simulated the prepared tooth, and evaluated for the marginal gap for four different provisional restorative materials and divided into four different groups A, B, C, and D. Each group was further divided into six subgroups according to temperature of water and time of immersion. In each group the samples were immersed in water at 20, 30, and 40 degrees, respectively for 5 and 10-minutes duration. Four different temporary restorative materials for crown fabrication were loaded each time to make temporary crowns. Results Each sample was placed under travelling stereoscopic microscope (20× magnification) and photographed. Results for each surface were obtained, and the average of three surfaces was calculated. Knoop hardness was measured using a microhardness tester. The study was subjected to statistical analysis, to know the statistical significance, of the effect of difference in time and temperature changes at the time of final polymerization on surface microhardness and marginal integrity of four different provisional restorative materials. Discussion The mean marginal discrepancies of bis-GMA (group B) at 20, 30, and 40°C for 5 and 10 minutes in water were smaller than the results of other groups. Microhardness evaluation showed that the poly ethyl methacrylate (PEMA) type resin exhibited significantly lower microhardness than the bis-acryl resin composites (Protemp 4 and Systemp.c&b) at both time and temperature intervals. Conclusion The bis-acryl composites material has the least marginal discrepancy in comparison with PEMA and polymethyl methacrylate (PMMA). The bis-acryl composites materials exhibit superior surface microhardness followed by PEMA and PMMA.