based on the type of acrylic resin used , the specimens were divided into three groups with 10 specimens each .
they were group 1 - conventional denture base resins , group 2 - high impact denture base resins , and group 3 - glass reinforced denture base resins .
each group was subjected to flexural strength evaluation . to make the mold space for the specimens , three stainless steel cuboidal dies were milled measuring 65.5 mm  10.5 mm  3.5 mm in length , breadth , and thickness , respectively , [ figure 1 ] .
the metal dies were flasked using type ii dental plaster to complete the flasking procedure .
the plaster was allowed to set for an hour , and parts of the flask were separated [ figure 2 ] .
the stainless steel dies were retrieved to create the mold space for the acrylic specimen . the separating medium ( cold mold seal )
was applied to the mold space created and is allowed to set for 20 min .
three different pmma were evaluated , namely milled stainless steel die three stainless steel die were placed in a single flask 
 group 1 - conventional denture base resins ( dental products of india heat cure resins ) [ figure 3 ] 
 group 2 - high impact denture base resins ( trevalon hi ) [ figure 3 ] 
 group 3 - glass reinforced denture base resins ( acrylic composite ) [ figure 3 ] . 
 
group 1 - conventional denture base resins ( dental products of india heat cure resins ) [ figure 3 ] 
  group 2 - high impact denture base resins ( trevalon hi ) [ figure 3 ] 
  group 3 - glass reinforced denture base resins ( acrylic composite ) [ figure 3 ] .
ten acrylic specimens taken from each group for testing flexural strength the polymer and monomer were proportioned as suggested by the manufacturer in a ratio of 3:1 by volume .
the acrylic resin was packed into the mold , after trial closure the flask was tightened to their final position .
the specimens were subjected to curing cycle starting from room temperature to reach 74c in 30 min and held at this temperature for approximately 2 h and then terminal boiling point was done at 100c for 1 h. after bench cooling , the acrylic specimens were retrieved , trimmed , finished , and polished to the required dimension measuring 65 mm  10 mm  3 mm in length , breadth , and thickness , respectively ( according to international organization for standardization [ iso ] standardization 1567 ) .
the exclusion criteria for the samples were specimens with smaller dimensions , internal porosity , external porosity , worn out edges , and surface defects .
all the thirty specimens were immersed in distilled water for 28 days at room temperature to simulate the oral conditions .
the specimens were prepared by marking three lines a , b , and c. the first line a was drawn at a distance of 10 mm from the border of the specimen .
the second line b was marked at 45 mm away from line a. these two lines a and b correspond to the location of supporting arm in the universal testing machine .
a midline between these lines a and b was marked as line c , and it is the location the striker of the testing machine would come and contact with the specimen [ figure 4 ] . as the universal testing machine plunges into the specimen , the specimen would fracture at a particular load [ figure 5 ] .
this maximum load before fracture ( f ) is given in newtons in the display of the testing machine .
the flexural strength of the given sample in megapascals was computed from the maximum load by using the formula s = 3fl/2bd2 jigs of supporting arm mounted at 45 mm apart fracture occurring at the center of the acrylic specimen 
 s  flexural strengthf  maximum load ( force ) before fracturel  length of the support arm ( 45 mm)b  width of the specimend  thickness of the specimen . 
 
s  flexural strength f  maximum load ( force ) before fracture l  length of the support arm ( 45 mm ) b  width of the specimen d  thickness of the specimen .
the mean value of the flexural strength of all the groups was computed and then statistically analyzed using one - way analysis of variance ( anova ) , using spss software version 21.0 ( ibm corporation , armonk , ny , usa ) .
to make the mold space for the specimens , three stainless steel cuboidal dies were milled measuring 65.5 mm  10.5 mm  3.5 mm in length , breadth , and thickness , respectively , [ figure 1 ] .
the metal dies were flasked using type ii dental plaster to complete the flasking procedure .
the plaster was allowed to set for an hour , and parts of the flask were separated [ figure 2 ] .
the stainless steel dies were retrieved to create the mold space for the acrylic specimen . the separating medium ( cold mold seal )
was applied to the mold space created and is allowed to set for 20 min .
three different pmma were evaluated , namely milled stainless steel die three stainless steel die were placed in a single flask 
 group 1 - conventional denture base resins ( dental products of india heat cure resins ) [ figure 3 ] 
 group 2 - high impact denture base resins ( trevalon hi ) [ figure 3 ] 
 group 3 - glass reinforced denture base resins ( acrylic composite ) [ figure 3 ] . 
 
group 1 - conventional denture base resins ( dental products of india heat cure resins ) [ figure 3 ] 
  group 2 - high impact denture base resins ( trevalon hi ) [ figure 3 ] 
  group 3 - glass reinforced denture base resins ( acrylic composite ) [ figure 3 ] .
ten acrylic specimens taken from each group for testing flexural strength the polymer and monomer were proportioned as suggested by the manufacturer in a ratio of 3:1 by volume .
the acrylic resin was packed into the mold , after trial closure the flask was tightened to their final position .
the specimens were subjected to curing cycle starting from room temperature to reach 74c in 30 min and held at this temperature for approximately 2 h and then terminal boiling point was done at 100c for 1 h. after bench cooling , the acrylic specimens were retrieved , trimmed , finished , and polished to the required dimension measuring 65 mm  10 mm  3 mm in length , breadth , and thickness , respectively ( according to international organization for standardization [ iso ] standardization 1567 ) .
the exclusion criteria for the samples were specimens with smaller dimensions , internal porosity , external porosity , worn out edges , and surface defects .
all the thirty specimens were immersed in distilled water for 28 days at room temperature to simulate the oral conditions .
the specimens were prepared by marking three lines a , b , and c. the first line a was drawn at a distance of 10 mm from the border of the specimen .
the second line b was marked at 45 mm away from line a. these two lines a and b correspond to the location of supporting arm in the universal testing machine .
a midline between these lines a and b was marked as line c , and it is the location the striker of the testing machine would come and contact with the specimen [ figure 4 ] . as the universal testing machine plunges into the specimen , the specimen would fracture at a particular load [ figure 5 ] .
this maximum load before fracture ( f ) is given in newtons in the display of the testing machine .
the flexural strength of the given sample in megapascals was computed from the maximum load by using the formula s = 3fl/2bd2 jigs of supporting arm mounted at 45 mm apart fracture occurring at the center of the acrylic specimen 
 s  flexural strengthf  maximum load ( force ) before fracturel  length of the support arm ( 45 mm)b  width of the specimend  thickness of the specimen . 
 
s  flexural strength f  maximum load ( force ) before fracture l  length of the support arm ( 45 mm ) b  width of the specimen d  thickness of the specimen .
the mean value of the flexural strength of all the groups was computed and then statistically analyzed using one - way analysis of variance ( anova ) , using spss software version 21.0 ( ibm corporation , armonk , ny , usa ) .
one - way anova was used to determine statistical differences among the flexural strength of three groups .
data were analyzed by spss software , and the results were obtained [ tables 13 ] .
the mean flexural strength of conventional pmma ( group 1 ) was 101.18 mpa , for high impact pmma ( group 2 ) it was 121.50 mpa , and for e - glass reinforced pmma ( group 3 ) it was 144.45 mpa .
specimens reinforced with glass fibers showed the highest flexural strength values , followed by a specimen reinforced with butadiene styrene and followed by conventional unreinforced acrylic resin .
the results of the statistical analysis for flexural strength were shown in the bar diagram [ statistical figure 1 ] .
results of flexural strength between three denture base resins measured in terms of megapascals descriptive analysis of data on flexural strength and impact strength anova on flexural strength graphical representation of data on flexural strength the mean transverse strengths of all test groups have statistically significant differences ( p < 0.005 ) .
the analysis of data revealed a significant difference between group 1 and group 2 , and 3 ( p < 0.005 ) .
scheffe s post - hoc test was done to substantiate this [ table 4 ] .
the prime and most frequent site of fracture in the upper denture is in the medial line . during chewing ,
flexural strength is a measure to know the resistance of the polymer to flexural deformation .
therefore , in this study , flexural were evaluated for the above three denture base resins . over the years , there have been various modifications attempted to improve the mechanical properties of pmma .
the modifications include chemical modification of pmma , through the incorporation of butadiene styrene to produce graft copolymer ( high impact denture base resins ) and mechanical reinforcement through the inclusion of various fibers ( fiber reinforced denture base resins ) .
therefore , all the three denture base resins ( conventional resins , high impact , and glass reinforced ) were included in this study .
artificial aging such as underwater storage in thermally controlled condition was simulated in this study .
different authors use different time periods of underwater storage , but the important influence of water on the flexural strength occurs during the first 4 weeks of immersion causing decrease of the flexural strength values . hence , a 28 days immersion in distilled water at 37c was used in this study . regarding the fiber reinforcement in denture base resins
, it has long been hypothesized that the addition of synthetic fibers to the monomer - polymer mixture may strengthen the resultant acrylic resin .
different authors used various types of fibers such as carbon , aramid , glass , polyethylene fibers .
the result of the present study , showed that silanized ( e)-glass fibers could considerably enhance the flexural strength of dental polymers , which could be due to the proper impregnation of fibers with resin polymer .
the other factors that are related to the strength of the fiber composite are the type of fibers , percentage of fibers in polymer matrix , the orientation of the fibers , fiber form ( chopped , continuous , unidirectional , bidirectional ) , and the adhesion of the fibers to polymer .
the use of carbon and aramid fibers produced an important clinical problem , namely poor esthetics and difficulties in polishing .
other advantages include its white translucent appearance , negligible water sorption , and excellent polishing characteristics .
glass fiber reinforcement has been the most clinically successful ; glass fibers are also esthetically suitable and are reported to have improved flexural strength , flexural modulus , fatigue strength , and impact strength of resin .
therefore out of all the fibers , self - reinforced glass fibers were selected for this study . in the present study , the flexural strength of unreinforced and reinforced acrylic resin specimens
specimens reinforced with glass fibers showed the highest flexural strength values , followed by specimens reinforced with butadiene styrene and followed by conventional unreinforced acrylic resin .
the reason behind this would be the presence of glass fibers , which may prevent the propagation of a crack when the stresses are applied . hence , glass fibers are strongly recommended in patients with heavy occlusal load or when fracture strength of denture base resin is of great concern .
this finding is in agreement with results of previous studies . for better understanding , the fracture and deformation mechanisms future researches about the effects of the residual monomer content and the viscoelastic properties on the fracture process and microstructure of acrylic resins could be performed .
within the limitation of the current study , the following conclusions were drawn 
 the flexural strength values of heat polymerized pmma were considerably enhanced by reinforcementspolymethyl methacrylate reinforced with glass fibers showed the highest flexural strength values this was followed by pmma reinforced with butadiene styrene , and the least strength was observed in the conventional denture base resins . 
 
the flexural strength values of heat polymerized pmma were considerably enhanced by reinforcements polymethyl methacrylate reinforced with glass fibers showed the highest flexural strength values this was followed by pmma reinforced with butadiene styrene , and the least strength was observed in the conventional denture base resins .
 aim : the aim of this study was to evaluate whether the flexural strength of a commercially available , heat polymerized acrylic denture base material could be improved using reinforcements.materials and methods : a total of 30 specimens ( 65 mm  10 mm  3 mm ) were fabricated ; the specimens were divided into three groups with 10 specimens each . 
 they were group 1 - conventional denture base resins , group 2 - high impact denture base resins , and group 3 - glass reinforced denture base resins . 
 the specimens were loaded until failure on a three - point bending test machine . 
 an one - way analysis of variance was used to determine statistical differences among the flexural strength of three groups . 
 data were analyzed by spss software version 21.0 ( ibm corporation , armonk , ny , usa ) and the results were obtained.results:the flexural strength values showed statistically significant differences among experimental groups ( p < 0.005).conclusion : within the limitations of the study polymethyl methacrylate ( pmma ) reinforced with glass fibers showed the highest flexural strength values this was followed by pmma reinforced with butadiene styrene , and the least strength was observed in the conventional denture base resins . 
Materials and Methods
Making of acrylic specimen
Evaluation of flexural strength
Results
Discussion
Conclusion
Financial support and sponsorship
Conflict of Interest