The effect of aluminum oxide addition on the flexural strength of heat activated acrylic resin: An in vitro study

Aim: This study was done to investigate the effect of adding 5-20% aluminum oxide (Al 2 O 3 ) powder by weight on the flexural strength of heat-polymerized acrylic resin. Materials and Methods: A total of 50 specimens of heat-polymerized acrylic resin were fabricated and were divided into five groups (n = 10). Group A was the control group (unmodified acrylic resin specimens). The specimens of the remaining four groups i.e., Groups B, C, D and E were reinforced with Al 2 O 3 powder to achieve loadings of 5%, 10%, 15% and 20% by weight. Specimens were stored in distilled water for 1 week and the flexural strength of the specimens was tested in a universal testing machine (5 mm/min crosshead speed). Results were analyzed by one-way analysis of variance. Weibull analysis was used to calculate the Weibull modulus, characteristic strength and the required stress for 1% and 5% probabilities of failure. Results: The mean flexural strength values of the heat-polymerized acrylic resin were (in MPa) 92.01, 114.46, 116.77, 123.11 and 129.72, for Groups A, B, C, D and E, respectively. The flexural strength increased significantly with the incorporation of Al 2 O 3 . Conclusion: Al 2 O 3 fillers are potential components to be added in denture bases to provide increased flexural strength. Adequate flexural strength of denture base is quite essential for the longevity of the prosthesis

A comparative study to evaluate retention of full metal crowns cemented with various luting agents with and without application of dentine conditioners: An in vitro study

Aim: The aim of the study is to assess the effect of dentin conditioners and luting cements on the retention of full metal crowns. Materials and Methods: Sixty recently extracted caries free molar teeth were prepared using airotor hand piece mounted to a surveyor with a custom made jig, to obtain a standardized 26° total convergence and 4 mm of axial height. Individual crowns were fabricated using base metal alloy. Thus prepared specimens were divided into six groups: 1) Two groups with no dentin conditioning (Control groups A and B), 2) Two groups, dentin conditioned with 10% polyacrylic acid conditioner (First test groups C and D), and 3) Two groups, dentin conditioned with 17% Ethylenediaminetetraacetic acid (EDTA) (Second test groups E and F). Groups A, C, and E were cemented with conventional glass ionomer whereas Groups B, D, and F were cemented with resin-modified glass ionomer. De-cementation was done using universal testing machine at a cross head speed of 1 mm/min after 48 hours of cementation. The obtained results were analysed using One-way analysis of variance (ANOVA) and Post hoc test. Results: The mean retentive (tensile) strength of Group A specimens was 2.26 ± 0.15 MPa, Group B specimens was 2.71 ± 0.15 MPa, Group C specimens was 12.26 ± 0.67 MPa, Group D specimens was 14.28 ± 1.47 MPa. Similarly, Group E specimens was 5.23 ± 0.62 MPa, and Group F specimens was 7.36 ± 0.51 MPa. Conclusion: Within the limitations of the study, retentive (tensile) strength required to dislodge the metal crowns was higher with the combination of resin-modified glass ionomer luting cement and 10% polyacrylic acid dentin conditioner