BRIEF RESUME OF THE INTENDED STUDY:
6.1) NEED FOR THE STUDY:
Polymethyl methacrylate (PMMA) was introduced as a denture base material by Dr. Walter Wright in 1937. Presently it is the most widely used material because of its favorable working characteristics, superior esthetics, stability in oral environment, processing ease and use with inexpensive equipments. The inherent disadvantage of it is low strength, causes an acrylic denture to fracture during service as a result of fatigue due to usage or impact due to fall.Some of the factors responsible for denture fracture also include low strength, flexibility of the material, induced processing stresses and high masticatory forces1.
However, it has been shown to improve the flexural strength by adding rubber phase in polymer pearls and the resultant material known as high impact strength resin23.
Moreover, various approaches to strengthen the acrylic resin have been suggested, including metallic reinforcement, wire mesh and synthetic fibers reinforcement by nylon, aramid, glass, polyethylene and carbon fibers13.
The purpose of this study is to evaluate whether or not reinforcement of normal heat polymerizing resin with kevlar fibers, glass fibers and or nylon fibers increases the flexural strength.
To compare the results with that of a commercially available High Impact heat polymerizing resin to determine a better and stronger material.
6.2 REVIEW OF LITERATURE:
D. C . Jagger , A. Harrrison and K. D. Jandt, authors review the attempts to improve the mechanical properties of denture base materials takes account of papers published during the last 30 years. Author has discussed about chemical modification of PMMA by the addition of rubber graft copolymers and the reinforcement of PPMA with other materials such as carbon fibers, glass fibers and ultra - high modulus polyethelen3.
Gulay Uzun, Nur Hersek, and Teomam Tincer, conducted a study which measured the effect of 5 fiber strengtheners on the impact strength,deflection, transversestrength and elasticity modulus of heat polymerized denture base resin. Specimens were reinforced with glass, carbon, thin kevlar, thick kevlar and polyethylene fibers in the woven form. It concluded that polyethylene and glass fibers are more resistant to impact strength, fiber reinforcement had no significant effect on the transversestrength. Polyethylene reinforcement significantly raised deflection value. Carbon , thick kevlar and polyethylene reinforced specimen showed significantly higher elasticity modulus values4.
Jacob john, Shivaputrapppa A. Ganagadhar, Shah I, conducted a study to evaluate reinforcing a conventional acrylic resin with glass fibers, aramid , or nylon fibers .Ten specimens of similar dimensions were prepared for each of the 4 experimental group: conventional acrylic resin and the same resin reinforced with 3 different fibers.All the test specimens were subjected to 3- point bending test. It was concluded that specimens showed better flexural strength than the conventional acrylic resin. Specimens reinforce with glass fibers showed the highest flexural strength, followed by aramid and nylon1.
Orhan Murat Dogan et.al conducted a study to observechanges in impact resistance of a denture base reinforced with five types of fibers . E- glass , polyester, rayon, and nylon fibers were cut in 2,4,6 mm length and added into the resin at concentration of 3% by weight, additionally impact sections were observed under a scanning electron microscope. It was concluded that impact energy increased with fiber length and the highest value was recorded for rayon fiber - reinforcement of 6mm length. E - glass fiber reinforcement produced relatively stable, high values for each length, good interfacial strength between polymer matrix and glass fibers was confirmed by scanning electron microscope analysis5.
D. Vojvodic et.al conducted a study to determine the flexural strength of E - glasss fiber reinforced dental polymer and dental high impact strength resin. Specimens were tested after polymerization and after artificial ageing performed by storage at37°c for 28 days and thermocycling. Author concluded that there was significantly higher values of flexural strength of glass reinforced specimens compared to the unreinforced specimens. Between groups of samples tested after polymerization and storage in water there was no statistically significant difference while samples tested after thermocycling revealed higher values2.
6.3 AIM AND OBJECTIVES OF THE STUDY:
- To evaluate the flexural strength of a high impact denture base resin material
- To evaluate the flexural strength of a commonly available heat cure denture base material reinforced with kevlar fibers ( Dupont).
- To evaluate the flexural strength of a commonly available heat cure denture base material reinforced with glass fibers.
- To evaluate the flexural strength of a commonly available heat cure denture base material reinforced with nylon fiber.
- To compare the flexural strength of the above mentioned materials and evaluate to know which material has a superior flexural property.
7. / MATERIALS AND METHODS
7.1 METHODOLGY
Preformed stainless steel metal dies of 65x10x3mm in size will be fabricated. 12 specimens fabricated in each of the experimental group and total sample size of 48 specimens.Control group test specimens were made with high impact heat cure denture base resin.Remaining three experimental groups consisted of a commonly available PPMA resin specimen of the same dimensions reinforced glass, kevlar, nylon fibers. Fibers have thickness of 10 to 15µm and were cut to 5mm length , the cut fibers were soaked in monomer for 10 minutes for better bonding with acrylic resin. The resin and fibers ( 2% by weight ) were mixed thoroughly to dispense the fibers. All specimens are subjected to polymerization cycle. Specimens were retrieved, trimmed with diamond bur. All the specimens were stored in water at room temperature for 1 week before testing. All the samples were subjected to three- point bending test on a universal testing machine at across head speed of 2mm/min. Data got was statistically analyzed with a one-way analysis of variance.
7.2 MATERIALS:
Control group: lucitone 199 and / or Acrylyn H heat cure material
Study group: DPI heat cure material
Group 1: high impact denture base resin
Group 2: Commonly available heat cure resin reinforced with kevlar fibers
( Dupont, India)
Group 3: Commonly available heat cure resin reinforced with glass fibers
Group4: Commonly availableheat cure resin reinforced with nylon fibers
7.3 DOES THE STUDY REQUIRE ANY INVESTIGATIONS OR INTERVENTIONS TO BE CONDUCTED IN PATIENTS OR OTHER HUMANS OR ANIMALS?
No.
7.4 HAS ETHICAL CLEARANCE BEEN OBTAINED FROM YOUR INSTITUTION :
Yes
8. / 8.1 LIST OF REFERENCES
- Jacob john, Shivaputtrappa A, Gangadhar, Shah I. Flexural strength of heat polymerized PMMA denture resin reinforced with glass, aramid or nylon fibers.J Prosthet Dent 2001; 86: 424-427.
- D. Vojvodic , F Matejicek, Z Schauperl, K Mehulic, Ivana B and Sanja S.Flexural strength of E - Glass fiber reinforced dental polymer and dental high impact strength resin. Strojarstvo 2008;50(4):221-230.
- D. C . Jagger , A. Harrrison and K. D. Jandt.The reinforcement of dentures. Journal of oral rehabilitation 1999;26: 185-194.
- Gulay Uzun, Nur Hersek, and Teomam Tincer. Effect of five woven reinforcements on the impact and transverse strength of denture base resin. J Prosthet Dent 1999;81:612-620
- Orhan Murat Dogan, Giray Bolayir, Selda Keskin, Arife Dogan. The effect of esthetic fibers on the impact resistance of a conventional heat - cured denture base resin. Dental Materials Journal 2007;26(2):232-239.