International Journal of Dental Sciences and Research
ISSN (Print): 2333-1135 ISSN (Online): 2333-1259 Website: Editor-in-chief: Marcos Roberto Tovani Palone
Open Access
Journal Browser
International Journal of Dental Sciences and Research. 2015, 3(3), 64-71
DOI: 10.12691/ijdsr-3-3-6
Open AccessArticle

Effect of Varying Curing Regimes and Powder-liquid Ratios on the Flexural Strength and Surface Porosities of Heat Cure Acrylic: An In-vitro Experiment

Saleha Nisar1, Faisal Moeen2, and Uzma Hasan1

1Student of MPhil Dental Materials, Islamic International Dental College, Riphah University, Islamabad, Pakistan

2Department of Dental Materials, Islamic International Dental College, Riphah University, Islamabad, Pakistan

Pub. Date: May 14, 2015

Cite this paper:
Saleha Nisar, Faisal Moeen and Uzma Hasan. Effect of Varying Curing Regimes and Powder-liquid Ratios on the Flexural Strength and Surface Porosities of Heat Cure Acrylic: An In-vitro Experiment. International Journal of Dental Sciences and Research. 2015; 3(3):64-71. doi: 10.12691/ijdsr-3-3-6


Objectives: To evaluate and compare the effect of varying curing regimes and powder-liquid ratios on flexural strength and surface porosities in heat cure acrylic denture base resin. Methodology: Heat cured acrylic specimens (18 x 10 x 3mm) were made according to four powder-liquid ratio groups(2.22, 2.00, 1.80 and student-ratio) and polymerized according to four different curing cycles. Each group consisted of 16 samples with a total of 64 acrylic discs. Curing cycles 1A and 1B initiated curing of specimens at room temperature followed by a terminal boil for 60 and 30 minutes respectively. Cycles 2A and 2B initiated curing at 70°C and 100°C respectively, without any terminal boil. All discs were tested for flexural strength by the ‘short beam’ testing method after immersion in water at 37°C for 28 days. Perimeter of each surfacepore was outlined and area of each pore was measured by a SEM. Total area of surface pores was calculated and expressed in percentage form. Results: Regression analysis indicated a very weak negative correlation (-0.085) between the powder-liquid ratios and the flexural strength values (p =0.252), indicating that variations in powder-liquid ratio does not affect the flexural strength of the acrylic specimens. Placing the curing assembly directly in the water bath at 100°C for 30 minutes showed the lowest over-all flexural strength and highest porosity percent, while immersing the flask in water bath at room temperature, gradually increasing the temperature from 70°C to 100°C and maintaining it for 60 minutes displayed the lowest over-all percent porosity and highest flexural strength values. A weak positive correlation (0.286) between the groups and percent porosity values (p=0.025) indicate a poor effect of powder-liquid ratio on porosities. Conclusions: Flexural strength and percent porosity of acrylic resins are affected more by changes in curing regimes rather than variations in powder-liquid ratio. Increasing the terminal boil period by 30 minutes had a significant effect on reducing percent porosity however did not enhance flexural strength of heat cure acrylic specimens.

Polymethyl-methacrylate (PMMA) polymerization method flexural strength porosity terminal boil

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit


[1]  Meng TR, Latta MA. Physical properties of four acrylic denture base resins. J Contemp Dent Pract. 2005;6(4):93-100.
[2]  Lee H-H, Lee C-J, Asaoka K. Correlation in the mechanical properties of acrylic denture base resins. Dental materials journal. 2012;31(1):157-64.
[3]  Harrison A, Huggett R. Effect of the curing cycle on residual monomer levels of acrylic resin denture base polymers. Journal of dentistry. 1992;20(6):370-4.
[4]  Jagger R. Effect of the curing cycle on some properties of a polymethylmethacrylate denture base material. Journal of oral rehabilitation. 1978;5(2):151-7.
[5]  Anusavice KJ, Phillips RW, Shen C, Rawls HR. Phillips' science of dental materials: Elsevier Health Sciences; 2012.
[6]  Singh S, Palaskar JN, Mittal S. Comparative evaluation of surface porosities in conventional heat polymerized acrylic resin cured by water bath and microwave energy with microwavable acrylic resin cured by microwave energy. Contemporary clinical dentistry. 2013;4(2):147.
[7]  Pero AC, Barbosa DB, Marra Je, Ruvolo‐Filho AC, Compagnoni MA. Influence of microwave polymerization method and thickness on porosity of acrylic resin. Journal of Prosthodontics. 2008;17(2):125-9.
[8]  Shankar T, Gowd S, Ahmed ST, Vinod V, Goud MV, Rao NV. A Comparative Evaluation of the Dimensional Accuracy of Heat Polymerized Acrylic Resin Denture Base Clamped by the Conventional Method and by New-press Technique and Cured by Long Curing Cycle: An in vitro Study. The journal of contemporary dental practice. 2012;13(6):842-9.
[9]  Barbosa DB, Souza RFd, Pero AC, Marra J, Compagnoni MA. Flexural strength of acrylic resins polymerized by different cycles. Journal of Applied Oral Science. 2007;15(5):424-8.
[10]  Sadoon MM. The Effect Of Different Curing Times on The Hardness, Fracture Resistance And Color Change of Visible Light Cured Denture Base Resin. Al–Rafidain Dent J. 2009;9(1).
[11]  Raszewski Z, Nowakowska D. Mechanical properties of hot curing acrylic resin after reinforced with different kinds of fibers. International Journal of Biomedical Material Research. 2013;1(1):9-13.
[12]  Ghani F, Kikuchi M, Lynch C, Watanabe M. Effect of some curing methods on acrylic maxillary denture base fit. The European journal of prosthodontics and restorative dentistry. 2010;18(3): 132-8.
[13]  Doǧan A, Bek B, Cevik N, Usanmaz A. The effect of preparation conditions of acrylic denture base materials on the level of residual monomer, mechanical properties and water absorption. Journal of dentistry. 1995; 23(5):313-8.
[14]  Berg C, Tirosh J, Israeli M. Analysis of short beam bending of fiber reinforced composites. Astm Stp. 1972;497:206-18.
[15]  Doğan OM, Bolayır G, Keskin S, Doğan A, Bek B. The evaluation of some flexural properties of a denture base resin reinforced with various aesthetic fibers. Journal of Materials Science: Materials in Medicine. 2008; 19(6):2343-9.
[16]  Kanie T, Fujii K, Arikawa H, Inoue K. Flexural properties and impact strength of denture base polymer reinforced with woven glass fibers. dental materials. 2000;16(2):150-8.
[17]  Yunus N, Rashid A, Azmi L, ABU‐HASSAN M. Some flexural properties of a nylon denture base polymer. Journal of oral rehabilitation. 2005;32(1):65-71.
[18]  Vojvodić D, Komar D, Schauperl Z, Čelebić A, Mehulić K, Žabarović D. Influence of different glass fiber reinforcements on denture base polymer strength (Fiber reinforcements of dental polymer). Official Publication of the Medical Association of Zenica-Doboj Canton Bosnia and Herzegovina. 2009;6(2):227-34.
[19]  Vallittu PK, Ruyter I, Ekstrand K. Effect of water storage on the flexural properties of E-glass and silica fiber acrylic resin composite. The International journal of prosthodontics. 1997;11(4):340-50.
[20]  Compagnoni MA, Barbosa DB, de Souza RF, Pero AC. The effect of polymerization cycles on porosity of microwave-processed denture base resin. The Journal of prosthetic dentistry. 2004;91(3):281-5.
[21]  Kasina SP, Ajaz T, Attili S, Surapaneni H, Cherukuri M, Srinath H. To evaluate and compare the porosities in the acrylic mandibular denture bases processed by two different polymerization techniques, using two different brands of commercially available denture base resins-an in vitro study. Journal of international oral health: JIOH. 2014;6(1):72.
[22]  Novais PMR, Giampaolo ET, Vergani CE, Machado AL, Pavarina AC, Jorge JH. The occurrence of porosity in reline acrylic resins. Effect of microwave disinfection. Gerodontology. 2009;26(1):65-71.
[23]  R Moosa GF. Effect of curing methods and temperature on porosity in acrylic resin denture bases. Pak Dent Assoc. 2012;21(03):127-35.
[24]  Machado C, Sanchez E, Azer SS, Uribe JM. Comparative study of the transverse strength of three denture base materials. Journal of dentistry. 2007;35(12):930-3.
[25]  Urban VM, Machado AL, Oliveira RV, Vergani CE, Pavarina AC, Cass QB. Residual monomer of reline acrylic resins: Effect of water-bath and microwave post-polymerization treatments. dental materials. 2007;23(3):363-8.
[26]  Seo RS, Vergani CE, Giampaolo ET, Pavarina AC, Machado AL. Effect of a post-polymerization treatments on the flexural strength and Vickers hardness of reline and acrylic denture base resins. Journal of Applied Oral Science. 2007; 15(6): 506-11.
[27]  Bartoloni J, Murchison D, Wofford D, Sarkar N. Degree of conversion in denture base materials for varied polymerization techniques 1. Journal of oral rehabilitation. 2000;27(6):488-93.
[28]  Phoenix RD, Mansueto MA, Ackerman NA, Jones RE. Evaluation of mechanical and thermal properties of commonly used denture base resins. Journal of Prosthodontics. 2004;13(1):17-27.
[29]  Lee Sy, Lai Yl, Hsu Ts. Influence of polymerization conditions on monomer elution and microhardness of autopolymerized polymethyl methacrylate resin. European journal of oral sciences. 2002; 110(2): 179-83.
[30]  Faraj S, Ellis B. The effect of processing temperatures on the exotherm, porosity and properties of acrylic denture base. British dental journal. 1979; 147(8): 209.
[31]  Vallittu PK, Miettinen V, Alakuijala P. Residual monomer content and its release into water from denture base materials. dental materials. 1995;11(5):338-42.
[32]  Islam KZ, Moral MAA, Rahman MM. Effect of Curing Time on the Flexural Strength of Heat Cured Acrylic Resin. City Dental College Journal. 2012;9(2):15-8.
[33]  Williams DR, Chacko D, Jagger DC, Harrison A. Reline materials—handle with care? An investigation into the effect of varying the powder/liquid ratio on some properties of auto-polymerising acrylic resin materials. Primary Dental Care. 2001;8(4):151-5.
[34]  Geerts G, du Rand M. The influence of powder liquid ratio on the flexural strength of fibre reinforced acrylic resin material. 2009.