Permissible Number Of Microwave Disinfection Cycle To Complete Maxillary Polymethyl

Methacrylate (PMMA) Denture Bases

Presenter

Noor Farishahbanu binti Ahmad

Sharifah Nor’Aishah Syed Yussof

Supervisor:

Dr Wan Nor Syariza Wan Ali

Introduction• Denture hygiene usually is done by mechanical or chemical

disinfection. However, these techniques show some disadvantages:-

• Therefore, we proposed microwave disinfection as an alternative method for denture disinfection for its benefits:-

Literature review

Rationale

•Dentures can be contaminated internally and externally, therefore microwave disinfection can prevent cross contamination from patient to the dentist or technologist or vice versa.

•Thus will reduce the risks of transferring pathogenic bacteria to the health personnel by direct contact during handling of the prosthesis in the clinic or laboratory.

Objectives General objectiveTo find any alteration in denture base adaptation prior to microwave disinfection.

Specific objectiveTo find maximum number of microwave irradiation cycle under power time setting 630W/3minutes in maxillary acrylic resin denture base adaptation until a statistically significant distortion is detected.

Hypothesis Denture base adaptation will be altered after a certain amount of cycle of microwave irradiation under power time setting of 630W/3 min.

Methodology

Samples were divided into 2 groups (n=15). Experimental disinfection treatments were: 1)control (no disinfection)2)protocol 1 (630W/3 min).

Denture immersed in water Irradiated under 630W

and for 3 minutesThe samples were stored in water bath at 37˚C between each cycles.

Coltene Rapid Liner®

0.5ml catalyst to 5ml base Coltene Rapid Liner® was hand mixed

Silicone coltene rapid liner® coated onto the internal surface of denture bases

Silicone excess trimmed using scalpel blade

Sample was pressed under an 8 kgf axial load

Silicone film peeled off from master cast

Silicone film

Weighed using analytical balance

RESULTAll data were analyzed by using SPSS paired t-testTable 1: control group

P > 0.05

No significant difference

Table 2: Experimental groupP > 0.05

P < 0.05

Significant difference

Discussion

• Microwave disinfection procedure heats water up to temperature of more than 72˚C that leads to further polymerization in the polymer chain and thus, increase in linear dimensional changes in the acrylic denture bases.

• This study is in disagreement with study conducted by Polyzois (1995), Sabrina et al (2005) which stated that there was no distortion after microwave disinfection. This is probably because their studies did not continue the research until distortion is detected and stopped only at a maximum of 7 cycles.

• Thomas (1995) and Webb et al (1998) also reported that 500W/3 and 15 min did not promote clinically relevant linear alteration in acrylic. However, their research uses rectangular resin and not denture bases.

Strength of this study

• This study was conducted to find the maximum number of microwave disinfection cycle and only stopped when distortion was detected.

• Nearly replicates a clinical situation since this study was conducted on denture bases instead of resin rectangles.

• Coltene Rapid Liner® was used which has high tear resistance property, thus it is easier to peel off than light body silicone.

Limitation of research

• Gap observed at T0 suggested pre existing discrepancy formed during denture processing procedure from polymerization shrinkage, stress induced and cooling during flasking, etc. However the changes was measured by using T0 as the baseline reading to compare the changes for every cycles.

Clinical Relevance

• Microwave sterilization recommendation to patient might be controversial due to several reasons:- Patient’s understanding and liability to use the 630W/3mins

power time setting concept. - Not recommended as daily or weekly routine since it will shorten the denture’s life span.

• Suggestion for microwave disinfection:- Prevent cross contamination to clinician in clinic and to technician or from a denture to another in laboratory.- High risk patient to infection episodes, i.e. patients with infectious disease and immunosuppressed patients.- Submission to microwave sterilization that does not exceed 10 cycles.

Conclusion

No significant changes found in the control group while microwave disinfection at 630W/3mins proved to cause linear dimensional changes and increase in misfit of denture bases to its corresponding cast after the tenth (10th) cycle.

Suggestion for further improvement

• This study was limited to an in vitro experiment and a further clinical trial should be conducted to compare adaptation of denture bases in patients;

- statistically significant distortion in laboratory experiment might not be significant clinically.- patient have adaptation ability to dentures such as saliva and muscular control.

References1. Asad T, Watkinson AC, Huggett R. the effect of disinfection procedures on flexural properties of denture base

acrylic resins. J Prosthet Dent 1992; 68: 191-195 2. Banting DW, Hill SA. Microwave disinfection of dentures for the treatment of oral candidiasis. Spec Care Dentist

2001; 21: 4-8).3. Baysan A, Whily R, Write PS. Use of Microwave energy to Disinfect a Long-Term Lining Material Contaminated with

Candida Albicans or Staphylococcus aureus. J Prosthet Dent 1998; 79: 454-84. Consani, Viera, Mesquita, Mendes, Arioli-Filho. Effect of microwave disinfection on physical and mechanical

properties of acrylic resin. Braz Dent J 2008;19(4): 348-3535. Craig RC. Prosthetic applications of polymers. In: Restorative dental materials. Craig RC (editor). 10th ed. Saint

Louis:Mosby; 1997. p. 500-5516. Dovigo, L.N.; Pavarina, A.C.; Ribeiro, D.G.; Oliveira, J.A.; Vergani, C.E. & Machado, A.L. (2009). Microwave

Disinfection of Complete Dentures Contaminated In Vitro with Selected Bacteria. Journal of Prosthodontics, Vol.18, 611–617, ISSN 1059-941X

7. Dixon DL, Breeding LC, Faler TA. Microwave disinfection of denture base materials colonized with Candida albicans. J Prosthet Dent 1999;81: 207-214

8. Dyer RA, Howlett JA. Dimensional stability of denture bases following repair with microwave resin. J Dent 1994;22:236- 241

9. Fleck G, Ferneda F, Ferreira da Silva DF, Mota EG, Shinkai RS. Effect of two microwave disinfection protocols on adaptation of poly methyl metacrylate denture bases. 2007; 56(3): 121-7.

10. Katberg JW., Jr. Cross contamination via the prosthodontics laboratory. J prosthet Dent 1974;32:412-41911. Neppelenbroek KH, Pavarina AC, Spolidorio DM, Vergani CE, Mima EG, Machado AL. Effectiveness of microwave

sterilization on three hard chairside reline resins. Int J Prosthodont 2003;16:616-620

12. R.M Nirale, Ram Thombre, Girish Kubasad. Comparative Evaluation of sodium Hypochlorite and Microwave Disinfection of Dimensional Stability of Denture Bases. J Adv Prosthodont. 2012 February;4(1):24-29

13. Polyzois GL, Zissis AJ, Yannikakkis SA. The effect of glutaraldehyde and microwave disinfection on some properties of acrylic denture resin.Int J prosthodont1995 8150-154

14. Powell GL, Runnels RD, Saxon BA, Whisenant BK. The presence and identification of organisms transmitted to dental laboratories. J Prosthet Dent. 1990;64(2): 235-7

15. Rohrer R, Bulard B. Microwave sterilization. J Am dent Assoc 1985; 110:194-816. Sabiha S. Bunek. Impression Materials 360°: How to choose the right impression material. Fri, 2012-

04-20 10:11.17. Sabrina PAVAN1 João Neudenir ARIOLI Filho1 Paulo Henrique DOS SANTOS2 Francisco de Assis

MOLLO Jr.1Effect of Microwave Treatments on Dimensional Accuracy of Maxillary Acrylic Resin Denture BaseBraz Dent J 16(2) 2005

18. Shay K. Denture hygiene: a review and update. J Contemp Dent Pract 2000;1: 28-4119. Thomas CJ, Webb BC, microwaving of acrylic resin dentures. Eur J prosthodont Restor Dent 1995; 3:

179-18220. Vig RG. Reducing laboratory aerosol contamination. J Prosthet Dent. 1969;22:156-15721. Webb BC, Thomas CJ, Harty DWS, Willcox MDP. Effectiveness of Two Methods of Denture

Sterelization. J Oral Rahabil 1998; 25: 416-423

Thank you