study about effect of microwave disinfection on acrylic denture base materials

1. HELLO!

3. Presented by:
Abdullah Ahmad 5210039
Assem Awad 5211149

4. “Some journeys don't have
endings, they lead to new
beginnings. These are the
journeys that lead to great
adventures!”
Alex Haditaghi,

5. Let’s Start our Journey

6. INTRODUCTION
• To date the most commonly used denture base
materials are the conventional heat-cured
acrylic resins.
• Its popularity originated from its:
High aesthetic
quality
Ease in
manipulation
Stability in
the oral
conditions
Ease in
finishing and
polishing
Inexpensive
equipment.

7. Methacrylate-based polymers are polymerized by different
methods
Heat
curing.
Chemical
curing.
Light
curing.
Microwave
curing.
INTRODUCTION

8. • These processing methods can affect resin physical properties
mainly related to the degree of monomer conversion and
porosity, which in turn may impact surface characteristics and
prosthesis survival.
INTRODUCTION
Dimensional changes

9. • An acceptable polymerization method is the one
which is capable of achieving the best properties of
acrylic resin as fracture toughness, static strength,
flexural modulus , and dimensional stability, in short
possible time.
INTRODUCTION

10. The fracture resistance of polymethylmethacrylate (PMMA) IS NOT
SATISFACTORY. Different factors can be involved in denture fracture.
Among them, flexural fatigue and impact are the most common failure
mechanisms of an acrylic denture base
INTRODUCTION
Unfortunately

11. • Many approaches have been used to
strengthen acrylic denture base resins.
• These approaches involved the use of metal
wires or plates, fibers, metal powder or
rubber toughening agents.
INTRODUCTION

12. FURTHER MORE
• Conventional heat cured acrylic
resin is cured either by short curing
cycle (2 hours) or Long curing
cycle for more than 9 hours
INTRODUCTION

13. Advantages of microwave curing
Concept
Less time consuming
Less internal stress
Less procedures.
Good polymerization
Equal heat distribution
Ease of manipulation
INTRODUCTION
In expensive equipment

14. Human nature is complex. Even if we
do have inclinations toward violence,
we also have inclination to empathy,
to cooperation and to self-control.
Steven Pinker

17. •PUT HERE the
method of curing of
this type of resin

18. • Any studied prosthetic material has to
withstand repeated disinfection.
• Prosthetic materials sent from dental clinics to
the dental laboratories may be contaminated
by pathogenic bacteria, which can be
transferred to the prosthetic lab technicians
and cross transferred to other patients.
INTRODUCTION
In Addition

19. AND
• At home, denture DISINFECTION is necessary to remove oral
microorganisms, odor-causing particles and food debris.
• Denture disinfection should be carried out through a safe and simple technique
to ensure patient compliance for proper disinfection.
INTRODUCTION

20. BUT HOW TO DO
THAT?
INTRODUCTION

21. WE HAVE TWO
POSSIBLE
WAYS
INTRODUCTION

22. FIRST METHOD BY CHEMICAL DISINFECTION
• Using solutions of glutaraldehyde,
sodium hypochlorite, iodoform,
chlorine dioxide or alcohol
• But, chemical disinfection may
present disadvantages, such as
denture staining & oral tissue
reactions.
INTRODUCTION

23. What about
the second
way?
INTRODUCTION

24. SECOND WAY: MICROWAVE ENERGY
• Microwave energy has been indicated as a
simple, practical & low-cost
alternative to overcome the shortcomings
of chemical disinfection methods.
• It provides mechanical displacement to
bacterial colony all around the denture due
to orbiting of the microwave oven disc
INTRODUCTION

25. Is it mechanically safe to
microwave cure denture base
material, and to further disinfect
by microwave?

26. AIM OF THE
WORK

27. The aim of the present study was to compare between glass-
fiber-reinforced microwave-cured and conventional heat
cured acrylic denture base resin in regard to:
 Dimensional changes,
 Impact strength
 Flexural strength
Hardness,
Before and after repeated microwave disinfections.

28. MATERIAL
AND
METHODS

29. Conventional Heat Cured
Polymethyle Methacrylate
Acrylic Resin (Acrostone
Egypt)
MATERIALS & METHODS
Materials

30. Glass fibers reinforced
microwave cured acrylic
resin (conventional PMMA
reinforced by 5% e-glass
fibers)
MATERIALS & METHODS
Materials

31. MATERIALS & METHODS
Specimens preparation
A- CONVENTIONAL HEAT CURED ACRYLIC RESIN
(ACROSTONE)

32. MATERIALS & METHODS

33. MATERIALS & METHODS

34. SPECIMENS PREPARATION OF CONVENTIONAL
HEAT CURED ACRYLIC RESIN (ACROSTONE)

35. MATERIALS & METHODS
Specimens preparation
B- GLASS FIBERS REINFORCED MICROWAVE CURED
ACRYLIC RESIN

36. GLASS FIBERS REINFORCED MICROWAVE CURED
ACRYLIC RESIN
We kindly asked our partners at Pavia University, Italy to help us and to
fabricate the specimens with the same specifications as conventional
heat cured resin .

37. MATERIALS & METHODS
Specimens Groups
Group A: conventional heat
cured acrylic resin, N= 30
Group B: microwaved-cured glass
fiber reinforced acrylic resin, N=30
Impact
strength. N=10
Flexural
strength, n=10
Hardness, n=10
Impact
strength, n=10
Flexural
strength, n=10
Hardness, n=10
Half the specimens of each subgroup were tested before microwave disinfection.
Half the specimens of each subgroup were tested after repeated microwave disinfection

38. DIMENSIONAL CHANGES
MATERIALS & METHODS
• A digital caliber was used to measure the distance between the indentations on the surface
of the specimens of each type of acrylic resin used before being fractured by mechanical
testing.
• Measurements was made on specimens not subjected to microwave disinfection ( N=30)
• Measurements was made on specimens subjected to microwave disinfection ( N=30)

39. IMPACT STRENGTH
Is a standardized high strain-rate test
which determines the amount of
energy absorbed by a material during
fracture.
MATERIALS & METHODS
Specimens were subjected to an impact
strength test in the Charpy system (XJJ
Charpy impact tester, United, China) with
40 kpcm impact load.

40. FLEXURAL STRENGTH
Test provides values for the modulus of
elasticity in bending , flexural stress ,
flexural strain and the flexural stress-
strain response of the material.
MATERIALS & METHODS
Specimens were subjected to a 3-point bending test in a
universal testing machine (Digital display hydraulic UTM ,
WES 100, United, China) running at a crosshead speed
of 5 mm/min until failure.

41. KNOOP HARDNESS TEST
“Micro hardness test” a test for
mechanical hardness used
particularly for very brittle materials or
thin sheets, where only a small
indentation may be made for testing
purposes.
MATERIALS & METHODS
Specimens were subjected to Knoop hardness test in a
microindenter (United HV-1000; Chaina) calibrated with 25
g load during 10 s.

42. MATERIAL AND METHODS
DISINFICTION

43. The specimens were subjected to a 3-min microwaving cycle at 600 Watt in a
domestic microwave oven.
MATERIALS & METHODS

44. For this procedure, the specimens were immersed in glass bowls containing 150
mL of distilled water. Each specimen was subjected to 5 simulated disinfections,
being 1 per day
MATERIALS & METHODS

45. RESULTS

46. DIMENSIONAL CHANGES
Samples Dimensions before
disinfection
Dimensions after
disinfection
tuky’s test
Acrostone "G1" 18.16 18.06 (p>0.05)
Acrostone "G2" 18.18 18.8 (p>0.05)
Acrostone "G3" 18.22 18.12 (p>0.05)
Acron MC 18.20 18.12 (p>0.05)

47. Acrylic resin No disinfection
Simulated microwave
disinfection
Conventional resin 7.72 +- 0.41A 9.25 +- 0.09B
Arcon MC 7.88 +/- 0.19A 6.25 +/- 0.09A
Impact Strength
0
1
2
3
4
5
6
7
8
9
10
acrostone acron mc
before after

48. Acrylic resin No disinfection
Simulated microwave
disinfection
Acrostone 5.78 +- 0.40A 5.66 +- 0.07B
Acron MC 6.06 +/- 0.27A 5.78 +/- 0.10A
Flexural Strength
5.4
5.5
5.6
5.7
5.8
5.9
6
6.1
acrostone acron mc
Chart Title
before after

49. Acrylic resin No disinfection
Simulated microwave
disinfection
Acrostone 15.67 +- 0.90A 10.07 +- 0.28B
Acron MC 17.02 +/- 0.20A 16.16 +/- 0.17A
Knoop Hardness
0
2
4
6
8
10
12
14
16
18
acrostone acron mc
Chart Title
before after

50. CONCLUSIONS

51. CONCLUSIONS
Within the scope of this study, it was concluded that:
• Repeated microwave disinfection at 600 Watt, did not affect the
dimensional changes of acrylic resin denture base .
• Impact strength of conventional resin increased after repeated microwave
disinfection while that of the reinforced resin decreased
• Glass fiber reinforced microwave cured acrylic resin showed higher
flexural strength than conventional resin before and after repeated
microwave disinfection. Flexural strength is important to resist fracture
under masticatory loads on dentures.

52. CONCLUSION
Continue:
• Hardness of conventional resin was higher than
microwaved cured resin.
• After microwave treatment conventional resin hardness
decreased but microwaved cured remained stable.

53. RECOMMENDATIONS

54. RECOMMENDATIONS
• Further studies are recommended to clarify the results of this
study.
• Studies on reinforced resin with variable percent of glass fibers
and the study of its effect on mechanical properties and
survival of acrylic resin are needed.
• Microwave is a simple and reliable method for disinfection of
acrylic dentures.

55. REFERENCES

56. REFERENCES
1. Kahn RC, Lancaster MV, Kate W. The microbiologic cross-contamination
of dental prostheses. J Prosthet Dent 1982;47:556-559.
2. Sanitá PV, Vergani CE, Giampaolo ET, Pavarina AC, Machado AL.
Growth of Candida species on complete dentures: effect of microwave
disinfection. Mycoses 2009;52:154-160.
3. olyzois GL, Zissis AJ, Yannikakis SA. The effect of glutaraldehyde and
microwave disinfection on some properties of acrylic denture resin. Int J
Prosthodont 1995;8:150-154.
4. Consani RLX, Vieira EB, Mesquita MF, Mendes WB, Arioli-Filho JN.
Effect of microwave disinfection on physical and mechanical properties of
acrylic resins. Braz Dent J 2008;19:348-353.

57. Thank
You