Evaluation of Flexural Strength of Thermocycled Interim Resin Materials Used in Prosthetic Rehabilitation- An In-vitro Study.

INTRODUCTION: Provisional restoration is an analytical component of fixed prosthodontics serving as a ground plan for the design of fixed dental prosthesis. Flexural strength is critical in case of long standing fixed dental prosthesis, to appreciate success of full mouth rehabilitation cases and temporomandibular joint dysfunction therapies. AIM: The present study was to evaluate the flexural strength of different provisional restorative resins used for prosthetic rehabilitation. MATERIALS AND METHODS: Forty identical samples (n=10 for each material) measuring 25mm×2mm×2mm according to ADA/ANSI specification no. 27 were fabricated using autopolymerizing Poly Methyl Methacrylate (PMMA) (Group A); heat activated PMMA (Group B); autopolymerizing Bis-GMA composite resin (Group C) and light activated Urethane Dimethacrylate Resin (UDMA) (Group D). For 14 days all these samples were stored in artificial saliva. Ten samples from each material were subjected to thermal cycling for 2500 cycles (5°C to 55°C). Later, a standard three point bending test was conducted on all the specimens with a universal testing machine at a crosshead speed of 0.75mm/min. Statistical analysis used included Kruskal-Wallis and Mann-Whitney U test. RESULTS: The mean flexural strength of specimens confirmed higher flexural strength for Group C (102.98 Mpa) followed by Group B (91.86 Mpa), Group A (79.13 Mpa) and Group D (60.01 Mpa). There were significant differences between any two materials tested (p <0.05). Comparison between mean flexural strength values between four groups revealed significant difference between the interim materials (p <0.05). CONCLUSION: The greatest flexural strength was observed for Bis-GMA composite resins followed by heat cure methacrylate resins, autopolymerizing methacrylate resins and was least for light cure resins. While fabricating provisional restorations, these greater values should be considered for better outcome of the treatment.

The Effect of Al2O3 Addition on the Thermal Diffusivity of Heat Activated Acrylic Resin.

AIM: This study aimed at investigating the effect of adding 5% to 20% by weight aluminium oxide powder (Al2O3) on thermal diffusivity of heat-polymerized acrylic resin. MATERIAL AND METHODS: Twenty five cylindrical test specimens with an embedded thermocouple were used to determine thermal diffusivity over a physiologic temperature range (0 to 70°C). The specimens were divided into five groups (5 specimens/group) which were coded A to E. Group A was the control group (unmodified acrylic resin specimens). The specimens of the remaining four groups were reinforced with 5%, 10%, 15%, and 20% Al2O3 by weight. RESULTS were analysed by using one-way analysis of variance (ANOVA). RESULTS: Test specimens which belonged to Group E showed the highest mean thermal diffusivity value of 10.7mm(2)/sec, followed by D (9.09mm(2)/sec), C (8.49mm(2)/sec), B(8.28mm(2)/sec) and A(6.48mm(2)/sec) groups respectively. Thermal diffusivities of the reinforced acrylic resins were found to be significantly higher than that of the unmodified acrylic resin. Thermal diffusivity was found to increase in proportion to the weight percentage of alumina filler. CONCLUSION: Al2O3 fillers have potential to provide increased thermal diffusivity. Increasing the heat transfer characteristics of the acrylic resin base material could lead to more patient satisfaction.

"Redefining smile-a multidisciplinary approach".

This article presents a case report of a 20 year old female who was very much dissatisfied with her facial appearance and smile.On examination, it was found that there was a Angles class II division 1 malocclusion and a generalised spacing in the anterior teeth, with a retained, deciduous, left maxillary canine and a malposed 15. On radiographic examination, an impacted 18, 23 was noticed. As the part of the treatment plan, the retained deciduous canine and the impacted permanent canine were extracted and an orthodontic correction of the malocclusion was accomplished. The missing canine was planned to be replaced with a fixed partial denture.The short clinical crown height of the abutment teeth was increased by crown lengthening procedures and the pontic space was contoured to receive a ovate pontic by using diode lasers. The missing tooth was restored by using an all ceramic three unit zirconia bridge. This multi-disciplinary approach improved the smile of the patient and it ultimately enhanced her aesthetics and self confidence.