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Table of Contents   
ORIGINAL RESEARCH  
Year : 2021  |  Volume : 32  |  Issue : 3  |  Page : 380-384
Estimation of IZOD impact strength between different concentrations of chitosan-reinforced denture base resins


1 Department of Prosthodontics, Sri Ramaswami Memorial Dental College, Ramapuram, Chennai, Tamil Nadu, India
2 Department of General Surgery, Sri Ramaswami Memorial Dental College, Ramapuram, Chennai, Tamil Nadu, India

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Date of Submission24-Jan-2021
Date of Decision23-Jun-2021
Date of Acceptance09-Aug-2021
Date of Web Publication23-Feb-2022
 

   Abstract 


Background: Poly-methyl methacrylate (PMMA) is an universally acceptable denture base material. Efforts are made to increase the applications with the addition of new constituents. Chitosan has established antifungal properties. The mechanical properties of Chitosan–denture base composite is less evaluated in the literature. This study estimates the differences in impact strength of material for different concentrations of chitosan-reinforced denture base resins. Aim: The study estimated the differences in IZOD impact strength of denture base resin reinforced with 0%, 5%, 10% and 15% of chitosan by weight. Materials and Methods: The acrylic samples were fabricated in according to ISO 180 regulations. The study had four test groups (n = 10). ACh0 was the control group with no reinforcements. ACh5, ACh10 and ACh15 had chitosan reinforcement of 5%, 10% and 15% by weight. The samples were processed by conventional heat polymerization cycle and tested in IZOD impact testing machine. The data were recorded and statistically analyzed with Kruskal–Wallis test. Results: The mean impact strength was high in ACh5 (4.25 ± 1.05 kJ/m2) compared to ACh0 (2.88 ± 0.60 kJ/m2), ACh10 (3.63 ± 0.40 kJ/m2), ACh15 (3.38±0.60 KJ/m2). Statistically significant differences between the test groups was determined by Kruskal–Wallis and post hoc Bonferroni test (Chi-square = 12.843, P = .005, df = 3). Conclusion: The impact strength of denture base resin increased with 5% chitosan compared with other percentage of chitosan. No statistical significant relationship was observed between the groups.

Keywords: Chitosan, chitosan-reinforced denture base, denture base resin, heat cure acrylic resin, impact strength

How to cite this article:
Chander N G, Jayaraman V. Estimation of IZOD impact strength between different concentrations of chitosan-reinforced denture base resins. Indian J Dent Res 2021;32:380-4

How to cite this URL:
Chander N G, Jayaraman V. Estimation of IZOD impact strength between different concentrations of chitosan-reinforced denture base resins. Indian J Dent Res [serial online] 2021 [cited 2022 May 27];32:380-4. Available from: https://www.ijdr.in/text.asp?2021/32/3/380/338130



   Introduction Top


Poly-methyl methacrylate (PMMA) is a widely used denture base material. It is a versatile material and possesses superior properties compared to other denture base materials.[1],[2] Denture base fracture was anticipated in adverse clinical situations.[3],[4] Research was done to improve the mechanical, physical and biological properties.[5],[6],[7] Various fillers, nanomaterials, antimicrobials and antifungal agents were added but lacunae exist in finding the ideal materials with advanced properties.[8],[9],[10] Among the superior properties, the antifungal function is significant for elderly as it aids in controlling candidiasis.

Chitosan is a natural polysaccharide obtained from sea shell. It exhibits significant physical, mechanical and biological properties.[11] The biocompatibility, biodegradability, antimicrobial and bioactive properties aid in extensive medical and dental applications.[12] It is widely used in tissue engineering, wound healing, drug delivery, remineralization of teeth, bone regeneration and improving the properties of various dental materials.[11],[12],[13] The most significant application of chitsoan was antifungal action that can be effectively used in prosthodontics. The studies have established the antifungal properties of chitosan with PMMA.[14],[15] Less studies were done to estimate the mechanical properties.

The fracture of denture occurs due to impact forces in adverse clinical situations.[16],[17] The evaluation of impact strength of denture base materials is essential to avoid impact failure. Impact strength is the capacity of the material to withstand the sudden applied load. Clinically, it can lead to failure due to dropping of denture. The influence of chitosan-reinforced denture base material on impact strength is critical and is estimated. The null hypothesis of the study is that there is no difference in the impact strength between the various concentrations of chitosan-reinforced denture base resins.


   Materials and Methods Top


The study was approved by institutional review board. The study followed the ISO 180 guidelines. The master brass dye for the test samples was CAD milled in accordance to ISO dimension of 80 mm × 10 mm × 4 mm. The brass dye was duplicated with additional silicone impression material from which 40 wax patterns were made.

The study samples were divided into four groups in accordance to the percentage of chitosan-reinforced denture base resins. ACh0 was the control group with no chitosan in denture base resin. ACh5, ACh10, ACh15 contained 5%, 10% and 15% chitosan by weight reinforced denture base resins. The chitosan (Sigma Aldrich, Product number 448869, CAS: 9012-76-4, MDL: MFCD00161512) was added to denture base resin polymer (Dental Products of India, product no: 11811) and ball milled (PM 100 CM, Retsch GmbH) for 10 minutes at 300 RPM for homogenized mixture. The reinforced samples were heat cure processed by compression moulding technique. The wax patterns made by duplicating the dye was flasked, dewaxed and heat cure processed in accordance to test samples groups following conventional long heat polymerization cycle. The fabricated samples were finished and polished conventionally with different grits of sandpaper and pumice polishing. The specimen was rechecked for dimensions, porosity and deformities. The finished samples were stored in water for 48 hours earlier to testing.

The samples were tested in IZOD impact testing machine (Frank Bacon machinery sales company, Warren, MI). The samples were notched to the dimension of 8 mm. The acrylic samples were clamped vertically to the impact testing machine with the notched side facing the hammering pendulum [Figure 1]a and [Figure 1]1b. The pendulum hammered horizontally at a speed of 5 J. The data was recorded in KJ/m2 and analyzed by Kruskal–Wallis test using, Statistical Package for the Social Sciences software (SPSS 25 -2017, IBM SPSS Statistics). One sample from each group was evaluated with scanning electron microscope (FEI Quanta FEG 200). The fracture area, matrix and distribution of particles were observed [Figure 2], [Figure 3], [Figure 4], [Figure 5].
Figure 1: (a) – IZOD impact testing machine. (b) – Testing of samples

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Figure 2: SEM image of control group

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Figure 3: SEM Image of ACh5

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Figure 4: SEM image of ACh10

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Figure 5: SEM image of ACh15

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   Results Top


The descriptive statistics of the study is listed in [Table 1]. The mean impact strength of control group was 2.88 ± 0.60 kJ/m2. The higher impact strength was observed in ACh5 (4.25 ± 1.05 kJ/m2). The impact strength decreased with higher concentration of chitosan ACh10 (3.63±0.40 kJ/m2) and ACh15 (3.38±0.0.60 kJ/m2). Kruskal–Wallis test estimated the differences on impact strength between different groups [Table 2] and [Table 3]. Statistically significant differences between the test groups was found (Chi-square = 12.843, P > 0.05, df = 3) with a mean rank impact strength score of 12.10 for ACh0, 28.70 for ACh5, 22.30 for ACh10 and 18.90 for ACh15. (P > 0.05). The post hoc test [Table 4] revealed more significant difference between ACh0 and ACh5 than other groups that were statistically insignificant.
Table 1: Descriptive statistics of test specimen

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Table 2: Kruskal–Wallis test ranks

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Table 3: Kruskal–Wallis test statistics

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Table 4: Post hoc test with Bonferroni corrections

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   Discussion Top


The study rejected the null hypothesis that there were no differences in the impact strength between various concentrations of chitosan-reinforced denture base samples. The fracture of denture occurs in both intra and extra oral environment. The fracture in intraoral environment is mostly due to fatigue fracture and in extra oral environment it is due to impact forces.[16],[17] Majority of the studies determine flexural strength for the intraoral fracture of the material. In most clinical situations, the denture fracture happens due to adverse impact forces.[18] Many studies were done on impact strength of various denture base reinforcement materials.[19],[20],[21],[22],[23],[24],[25] Fewer studies were done to evaluate the impact strength of chitosan reinforcement on denture base resin. The presence of antimicrobial and antifungal constituents in the denture base material can support elderly individuals due to the compromised immunity. Candidiasis is one of the commonest infection found in elderly due to poor intraoral environment. The antifungal properties of chitosan was established in the literature and can be vital in controlling the fungal infection in elderly.[14],[15]

The study established higher impact strength at 5% concentration of chitosan by weight. The impact strength decreased with higher concentrations, but the strength was greater than the control group. The higher strength in ACh5 (4.25 ± 1.05 kJ/m2) can be attributed to better distribution of particles. The SEM images established equal distribution of particles [Figure 2], [Figure 3], [Figure 4], [Figure 5]. The particle occupying the pore spaces of acrylic to obtain the improved strength. Studies with various filler particles have proven the theory of crosslinking, improved copolymerization, surface hydrophobicity and decreased particle agglomerations.[19],[20],[21],[22],[23] These theories were applicable for improved strength. The concepts are generalized for chitosan–acrylic composite reinforcement. Additionally, the availability of increased materials at the grain boundary and the compaction displayed improved impact strength. The molecular interaction for bonding is better in 5% compared to the other test groups. However, the mechanism of interactions is unclear. Lesser studies have evaluated the organic molecular interaction. More studies are required to establish the molecular interaction.

The decrease in strength in ACh10 (3.63±0.40 kJ/m2) and ACh15 (3.38±0.0.60 kJ/m2) can be due to decreased chemical bonding and increase in chitosan particles. The decrease in strength can be attributed to poor crosslinking and copolymerization.[24],[25],[26] Moreover, the increase in filler particles can cause microcracks and porosities during polymerization and can lead to decrease in impact strength.[27],[28]

The impact strength of ACh10 and ACh15 were lesser than ACh5, but it is higher compared to control groups. The even distribution of particles can aid in improved strength of the composite materials compared to non-reinforced materials. The ball milling of the composite material aided in even distribution, improved bonding and better material properties compared to the control group. The even distribution of particles was substantiated with SEM images. The earlier studies on chitosan have used hand mixing or low profilic mixing devices. The use of ball milling in this study has additionally improved properties due to improved distribution and chemical interactions.

Extensive studies were done with many inorganic particles' reinforcements to acrylic. Few studies were done with micro and nano-organic particles. The literature has fewer data on the nature of interaction of organic particles with acrylic. Extensive studies are required to obtain the understanding of bonding between chitosan and denture base resin. The differences in the guidelines for estimation can also influence the impact strength. It is essential in future studies that more definitive guidelines have to be established for determining the impact strength of denture base resins and its modifications.


   Conclusion Top


Within the limitations, the study established that the mean impact strength was higher in ACh5% and the impact strength decreased with increase in percentage of chitosan.

Acknowledgements

  • Nanotechnology Research Centre (NRC), SRMIST for extending the research facilities.
  • DST-FIST program no.SR/FST/College-110/2017, Government of India in Easwari Engineering College, Chennai, Tamil Nadu, India for providing the research facilities.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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Correspondence Address:
Dr. N Gopi Chander
Department of Prosthodontics, Sri Ramaswami Memorial Dental College, Ramapuram, Chennai - 600 089, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijdr.ijdr_71_21

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