Study Title: Comparison of Flexural Strength and Modulus of Conventional and Graphene-Reinforced PMMA

Introduction:

This in-vitro experimental study aims to compare the flexural strength and flexural modulus of conventional polymethyl methacrylate (PMMA) and graphene-reinforced PMMA (G-PMMA) used in denture bases. PMMA is widely used for dentures due to its affordability, aesthetics, and biocompatibility but has limitations such as low flexural strength and susceptibility to fracture. Graphene, a strong and flexible nanomaterial, has demonstrated potential in enhancing PMMA's mechanical properties.

OBJECTIVE:

To compare the flexural strength and flexural modulus of conventional and graphene reinforced polymethyl methacrylate

HYPOTHESIS:

Null Hypothesis:

There is no difference in flexural strength and flexural modulus of graphene reinforced PMMA and conventional PMMA.

Alternative Hypothesis:

There is a difference in flexural strength and flexural modulus of graphene-reinforced PMMA and conventional PMMA.

Methodology:

• Study Design: In-vitro experimental trial

• Study SETTING:

  • The study will be carried out at Altamash Institute of Dental Medicine in the department of prosthodontic, Karachi Pakistan.
  • The graphene (Miraculum Graphene Private Limited,Gujrat, Ahmedabad,India) will be reduced at Karachi University's Food Science Department.
  • For the formation of mold, the digital metal bar (CoCr, Eplus3D, Hangzhou China) will be fabricated by Selective laser melting (SLM) (Audental Shanghai, East-central China) at Chughtai Lab in Peshawar, Pakistan.
  • The acrylic (Mr. Teeth, Royale Elite, Surrey,United Kingdom) samples will be cured by short curing cycling in the prosthodontic department at Bahria dental University, Karachi.
  • The thermocycling (thermocycler, San Francisco, USA) and universal testing for flexural strength and modulus of acrylic samples will be performed at the research laboratory of Dow University of health sciences.

• Sample Size: The projected sample size for this study is 76 specimen, 38 samples per group by comparing two means in open epi software19 (version 3).The calculation was based on the result of Kaan Yerliyurt 11 study, considering the mean value of 68.16 MPa and standard deviation (SD) of 5.79 MPa for the experimental group and the mean value of 72.6 MPa and standard deviation (SD) of 7.84 MPa for the control group of flexural strength. The analysis accounts for multiple time intervals, and the significance level (α) is set at 0.05, with a power of 80%, confidence interval (CI) of 95%, a margin of error (ME) of 5%.

  76 specimens (38 for conventional PMMA, 38 for G-PMMA)

• Subgroups: Each group will have thermocycled and non-thermocycled samples to assess durability.

SAMPLING TECHNIQUE:

Stratified sampling followed by systematic division.

• Methodology:
• Thermocycling: 2000 cycles (5°C-55°C) simulating oral temperature variations

Data Collection:

A metal bar mold (65 mm × 10 mm × 3 mm) will be designed using Exocad CAD software and 3D-printed from CoCr material using Selective Laser Melting (SLM). After fabrication, the bar will be used to create a silicone mold, which will then be invested in dental plaster to prepare the final mold for specimen curing. Graphene oxide (GO) will be chemically reduced, purified, dried, and mixed into PMMA powder. The acrylic resin will then be packed into the mold and processed via short curing cycle (74°C for 2 hours, 100°C for 1 hour). Then all the specimen will be prepared, thermocycle and ready for flexural strength and flexural modulus.

- Data Analysis: The data will be evaluated using the statistical package for social sciences (SPSS version 29, IBM, Chicago, Illinois United States). Descriptive statistics will be evaluated by mean, standard deviation, median, interquartile range of flexural strength, flexural modulus for PMMA, and GPMMA. Shapiro-Wilk test will be used to check the normality of the data distribution. For interferential statistics, Kruskal Wallis or ANOVA will be used with factors of loading force (N) and deflection (Y) between G-PMMA and conventional PMMA. Post-hoc analysis will be performed by Bonferroni or Tukey's test. In order to assess the effect of the external environment, the cofounding variable in this study will be thermocycling, which will influence the flexural strength and flexural modulus of PMMA and graphene-reinforced PMMA samples. A Chi-square or independent t-test will be used to analyze the impact of the cofounding variable, thermocycling, on flexural strength and modulus. The level of significance will be set at p < 0.05.

Rationale:

This study aims to determine whether graphene reinforcement improves the mechanical properties of PMMA, potentially leading to stronger and more fracture-resistant dentures. The findings could contribute to the development of more durable denture base materials with enhanced longevity and performance.

Inclusion Criteria:

• INCLUSION CRITERIA:

  • Samples that are dimensionally accurate in accordance to ISO Standard 178.21
  • Sample that are free from surface porosities like gaseous, granular or contraction porosities.
  • Samples have uniform color and surface texture indicating proper curing.
  • Samples free from crazing defects and warpage.
  • Samples with no signs of distortion after thermocycling.
  • Samples with homogeneously distributed graphene by visual inspection of samples.

Exclusion Criteria:

• • Samples with incorrect mixing ratio of base to catalyst.

  • Samples in which the metal bar is partially exposed.
  • Samples that are not fully embedded in plaster.
  • Samples showing sign of contamination from foreign body during packing process.
  • Samples with improper mixing of plaster shows a sign of cracks and voids surrounding the samples.
  • Samples in which the flask will not properly sealed during flasking.
  • Samples fractured due to thermocycling.
  • Samples fractured during handling or transportation before testing.