The Evaluation of Certain Properties of Polymethyl – Methacrylate Powder Treated By Autoclave. An in Vitro Study

The Evaluation of Certain Properties of Polymethyl –
Methacrylate Powder Treated By Autoclave. An in Vitro
Study •
Dr. Manar N. Y. Nazhat
Senior in prosthetic dentistry, Al-Salam hospital –Mosul, IRAQ
Prof. Tarik Y.K. Bashi
College of Dentistry, Mosul University, IRAQ
Prof. Dr. Amer A. Taqa
DBS. Department, College of Dentistry, Mosul University, IRAQ
Email: amertaqa@Hotmail.com

(PMMA) is the resin of choice for the fabrication of
denture bases. It has excellent physical properties
(Jagger et al., 2002).
Conventional acrylic resin material can be polymerized
by autoclave, requires less than 1hr., and utilizes
conventional equipment.

1- Study the effect of different curing techniques (by
water ˗ bath and by autoclave) on the physical,
chemical, and mechanical properties of acrylic resin
denture base material.
2- Invistigate the effect of autoclave on some
physical, chemical, mechanical properties, and some
thermal behavior on the (PMMA) powder by curing in
water bath and curing by autoclave.

(PMMA) is the material of choice for denture
prosthesis due to its desirable properties of excellent
aesthetics, and simple processing (Lee et al., 2002 ;
Trucker, 1981).
Although several new materials were used, (PMMA)
remained the most preffered material of choice for both
complete and partial denture prosthesis.

Methods of Curing of (PMMA) :-
1- Conventional water-bath :-
Water - bath processing technique has been the most
conventionally used.
Medium to long cured cycles of more than 7 hrs.
produce resin with less residual monomer and optimal
mechanical properties (Gugwad and Nagaral, 2010).

2- Microwave :-
A microwave is a device which depends on primary
heating effect by ionizing electromagnetic fields (Quan
et al., 1992).
One of the disadvantage is the use of the plastic flask
which is expensive and has a tendency to break down
after processing several dentures (Ebraheem, 2014).

3- Autoclave :-
An autoclave is a device that is used to sterilize
medical and other equipments.
An effective unit contains dry saturated steam, the air
should be removed from the chamber by automatic air
(Vernon, 2009).
Ming et al., (1996) show that when the acrylic resin
polymerized in autoclave with different pressure and
time, the results show no significant differences between
the autoclave curing and other conventional methods.

Tests Used in the Study :-
1-Transverse Strength Test :-
The transverse strength is a combination of
compressive, tensile and shear strength which directly
reflect the resistance of a material to fracture. (Lai et al.,
2004).
The strength is affected by composition of resin,
technique, degree of polymerization, water sorption and
also environment of the denture(Unalan et al., 2010).

2- Indentation Hardness Test :-
Hardness may be defined as the resistance to the
permanent surface indentation or penetration.
When the resin polymerized in autoclave with
different pressure and time, the results no significant
differences between the autoclave and conventional
polymerization methods (Ming et al., 1996).

3- Surface Roughness Test :-
It is influenced by either mechanical or chemical
polishing techniques.(Quirynen et al., 1990).
Surface roughness affected by factors such as
polymerization method, material used, and
incorporation of fibers into material (Karaagaclioglu,
2008).
4-Tensile Strength Test :-
It is defind as the internal induced force that resists
the elongation of a material in a direction of the stresses
(Academy of prosthodontics, 2005).
Polymerizing material under pressure can prove its
tensile strength and stiffness (Brosh et al.,2002).

5- Water Sorption & Solubility Tests :-
Sorption results an increase in weight and swelling
which affect the polymer properties.
Water act as a plasticizer and affects to dimensional
stability, internal stresses and crack formation (Tuna et
al., 2008).
6- Porosity Test :-
The presence of porosity is dependent on the type of
the material and the method of polymerization.
Porosity weakens prosthesis due to accumulation of
internal stresses and also lead to wrapage of acrylic
denture base. (Keller & Lautenchlager, 1985).

7- Density Test :-
Density is the physical property of matter as each
element and compound has a unique density associated
with it (O,Brein, 2008).
Low density is one of the criteria of the ideal denture
base material (Ebraheem, 2014).
8- Colour Property Test :-
Colour stability is one of the most important clinical
properties for dental materials and its ability to be able
to retain its orginal colour (Goiato et al., 2011).
•

The ability of resins to resist colour changes affected by
the structure, physical and chemical charactaristics of
inorganic fillers present in the resin (Galvao et al., 2010).
9- Melting Point Test :-
The melting point of a solid is the temperature at which
it changes state from solid to liquid at atmospheric
pressure.
The melting point of a pure substance is always higher of
an impure substance (Feistel and Wangner, 2006).

10- Polymerization Shrinkage Test :-
Dentures with poor fit are conductive to accelerated
jaw bone atrophy and affect to the retention of the
denture in the long time.
The variation in curing technique may not significantly
alter the pattern of dimensional behavior due to the
decrease in the molecular weight of polymer chains
(Sykora and Sutto, 1997).
.

11- Fourier Transform Infrared Spectroscopy
(FTIR) Test :-
It is based on infrared absorption and scattering
from the inter molecular bonds and they provide the
complementory information on the material
composition.
Abdul Razzak, (2010) concluded by (FTIR) that
raising temperature and extended polymerization
time showed improved conversion and lowering
monomer release.

12-Degree of Conversion Test :-
There is an inverse relationship between the degree
of conversion and the residual monomer(Rueggeberg,
1994; Barcelay et al., 1999).
Water - bath post polymerization treatment
increase the degree of conversion and reduced residual
monomer content rather than microwave irradiation.

13- Diffrentional Scanning Calometric (DSC)Test :-
It is a thermal technique that measures rate and
degree of heat changes in the material as a function of
time or temperature (Ebraheem, 2014).
(DSC) has been used for studying setting reactions of
dental acrylic resins, and for measuring the (Tg) of acrylic
materials (Aydogan et al., 2013).

14- Residual Monomer Analysis by High
Performance Liquid Chromatography (HPLC)
Test:-
Its important to determine the residual monomer
content of the acrylic resin which influences the allergy
of acrylic denture (Graig et al., 2000).
Attempts have been made to reduce the residual
monomer content of acrylic resins by using
thermoplastic and microwave polymerization rather
than heat technique (Alves et al.,2007).

Preparation of the samples :-
The samples in this study were prepared from VertexTM
regular type heat acrylic and divided into two main groups:
1The control groups were cured by water bath and by autoclave.
2The modified groups which modify the powder of acrylic by
autoclave . The heat applied is 132 °C and pressure for 4 hr. This
powder was also cured by water bath, and by using autoclave.
The modifiied powder before were cured, grinded by sieving
for about 5 minutes about 4000 cycle / min. and sieving in a sieve
No. 100 micron
•

F i g u r e ( 3 . 1 ) : A u t o c l a v e t y p e H I R A Y A M A - H I C T V E - H U A - 1 1 0
Figure (3.4): Grinding machine(XINGQIAN– XQ500)

Tests used in this study :-
1- Transverse Strength Test :-
The total no. of samples was thirty, five in each group,
in a bar shaped specimen.
The transverse strength test was performed using a
three point bending testing machine. The force required
for rupture was recorded and the stress was calculated
by equation (Dogan et al., 2008):
S ═ 3.P.L ⁄ 2.b.d2
Figure(3.7):Transverse strengthtestingspecimen dimension
65mm
10mm
2.5mm

Five specimens from each group, and Shore Hardness
Test Stand, was used
Tominimize the risk of misreading, readings were
taken in three different locations and the mean value
was taken from each sample subject to minor load and
the hardness inspector was calibrated after (15 - 20)
seconds .

The total no. of samples was eighteen, three in each
group,
The method used was to scan a diamond stylus across
the surface under constant load and compute the
numeric value which measured in µm by using a contact
profile meter.
10mm
10mm
2mm

4- Tensile Strength Test :-
Thirty samples were consructed of six groups.
Digital tensile testing machine was used and the samples
grasped by two arms of machine, forces was applied until
fracture of sample occured in the testing machine.
Vertical alignment of the sample was an important
factor for avoiding side loading or bending movements on
the sample. Tensile Strength = F (N) / A.
Figure(3.12):Tensile strengthTesting specimen dimensions.
90mm
10mm
3mm

Sixty samples prepared, ten in each group.
The samples were dried in air for 15 seconds at 37°C
until their weight was constant, this result was recorded
as (m1). The samples were then immersed in distilled
water for one week, removed, and weight, this result
was recorded as (m2).
The samples were placed in the desiccator and dried
until the final constant mass was recorded (m3). The
volume of samples (V) was calculated by multiplying
(length x width x thickness).

Tocalculate water sorption (Wsp) and solubility (Wsl)
the following equations (1) and (2) were used (Podyoski,
2010) :
Wsp = m2 ─ m1 ⁄ V (1)
(2)Wsl = m2 ─ m3 ⁄ V
6- Porosity Test :-
Sixty samples were prepared, ten from each group
The samples were dried in a desiccator.

With samples dried, two weights made, one with samples
in air and other immediately immersed in distilled water.
There were then weighetd at regular intervals until a
constant mass reached indicating a state of water saturation
for a 30 days.
The samples were removed from water and excess water
was removed and weighted, in air and with immediately
immersed in distilled water.

The porosity calculations were made using the
following equations (Keller and Lautenchlager, 1985;
Oliveira et al., 2003).
VS = ms ─ ms
⁄
⁄
Vd = md ─ md ⁄ ρw
⁄ ρw
(1)
(2)
% Porosity = ( VS ─ Vd ) x 100 ⁄ Vd (3)
Figure (3.15): Elecric sessitive balance up to 0.0001 gm.

7- Density :-
Two samples of (PMMA) powder were used and
divided in 2 groups.
Group 1- contain powder that is not treated by autoclave
Group 2- contain powder which was modified by
autoclave.
From each group, a sample of 2.5 gm powder of acrylic
and placed inside a graduated glass cylinder then vibrated
by the dental vibrator device for 2 minutes, then the
volume was recorded for groups (1 & 2).
The density was calculated according to the following
formula (Slowinnski et al., 2011):-
D = M / V

Total no. of samples was thirty, five in each group.
Measurments were done by Vita Easy shade device to
obtain the base line L*, a*, b* values
The total colour change :-
∆E = ] (∆L*)2+ (∆a*)2+(∆b*)2]½.
∆E = ](L2*- L1*) + (a2*- a1*) + (b2*- b2*)]½.
(1)
(2)
Magnitude of the difference between two colours in
specified condition, referred to as delta ∆E.

Several grains of (PMMA) of 5 samples from each
group.
The device used in this study for measuring the melting
point is electrothermal melting piont device.

10- Polymerization Shrinkage Test :-
Thirty samples were fabricated in both control and
modified groups. Six measurments distances (AB, BC, CD,
AD, AC & BD).
The dimensional changes in the polymerization of the
acrylic samples were calculated by this formula (Baydas et
al., 2003).

Dimensional Changes
= 𝑨𝑩 ² + 𝑩𝑪 𝟐 + 𝑪𝑫 𝟐
+
𝑨𝑫 𝟐
+
𝑨𝑪 𝟐 + (𝑩𝑫
)²
Polymerization shrinkage % determined by dimensional
changes.

11- Fourier Transform Infrared Spectroscopy
(FTIR) Test :-
A sample size of 1 mg was used in each group, samples
dried in a dry - oven for 12 hrs at 70 °C, the powder is
placed in the sample beam to obtain the chart of wave
length absorbed and transmitted in the wide range from
(500 - 4000 nm) region (Aydogan et al.,2013)

12- Degree of Conversion Test :-
Eighteen specimens were prepared, three specimens
from each type of group. All specimens were treated in
the same method for (FTIR) test.
By taking the ratio between the two absorbances of
each sample, the fraction of unreacted double bonds
could be calculated from the formula (Abdul Razzak,
2010)
DC % = [ 1-
𝑨𝒃𝒔(𝑪=𝑪)/𝑨𝒃𝒔 𝑪=𝑶 𝒑𝒐𝒍𝒚𝒎𝒆𝒓
𝑨𝒃𝒔 𝑪=𝑪 / 𝑨𝒃𝒔 𝑪=𝑶 𝒎𝒐𝒏𝒐𝒎𝒆𝒓
[ X 100 %
Where DC = degree of conversion
Abs = absorbance.

13-Diffrentional Scanning Calorimetric Test
(DSC) :-
Samples devided into 6 groups
A sample size of 4 mg was used in each study group,
(Tg) of each sample in the study groups was evaluated by
(DSC) in a nitrogen atmosphere with a heating rate of 10
°C / min. up to 250 °C (Aydogan et al., 2013).

14- Residual Monomer Test by (HPLC) :-
Eighteen samples were prepared.
A sample of 50 mg was dissolved in 1 ml of acetone
and then 10 ml of methanol was added to the solution
to precipitate the polymer (HPLC) analysis was
performed using liquid charomatography (Mohamed et
al.,2008).

Statistical Analysis :-
The following statistical methods were analyzed to
asses the results :-
1Descripitive Statistical analysis including, Mean,
Standerd Deviation and, Duncan᾿s Multiple Range
tests were used.
2 One way analysis of variance (ANOVA).

1-Transverse Strength Test :-
The descriptive statistics revealed a significant
difference between control groups and of modified
groups.
The presence of heat and pressure may affect to the
polymeric chains and change in structure which cause
enhancing the transverse strength of modified group.
1 •
Table(4.2):F–testbyANOVAtableofTransverseStrengthresults.
Sumof
Squares
df Mean
Square
F P-value
BetweenGroups 4659.173 5 931.835 248.825 0.000*
WithinGroups 89.878 24 3.745
Total 4749.052 29
*SignificantdifferenceatP≤0.05.df:degreeoffreedom
Figure (4.1): Mean, Standerd Deviation and Duncan᾿s Multiple Test of
Transverse strength test of acylic study groups.
120
100
80
60
40
20
0
A A1 B B1 C C1
TransverseStrength
N/mm2

The presence of porosities, and internal voids often
concentrated stresses in the matrix and formation of
microcracks under loading (Ming et al., 1996).
A significant difference between groups.
Conventional heat cured is leading to the formation of
a partial cross linked aliphatic polymer chains giving the
acrylic higher hardness (Antonio, 2000).

The treated acrylic powder with autoclave had a
plasticizing effect on acrylic particles which lead to a
decrease in hardness value.
65
80
75
70
85
60
A A1 B B1 C C1
Figure (4.3): Mean, Standerd Deviation and Duncan᾿s Multiple Test
of Indentation Hardness Test of acrylic study groups.
IndentationHardnessin
Kg/mm2
Table(4.8): F–testbyANOVAtableofIndentation Hardness results.
Sumof
Squar
es
df Mean
Squa
re
F P-
value
BetweenGroups 616.084 5 123.217 10.525 0.000
*
Total 897.042 29
*SignificantdifferenceatP≤0.05.df:degreeof freedom

A non - significant difference between groups. The
surface roughness of acrylic resin was not affected by
polymerization methods and without adverse effects on
the surface roughness of the material.
1.4
1.2
1
0.8
0.6
0.4
0.2
0
A A1 B B1 C C1
Figure (4.4): Mean, Standerd Deviation and Duncan᾿s Mutiple Range
of Surface Roughness Test of acrylic study groups.
SurfaceRoughnees
µm
Table(4.10):DescriptiveStatisticsofSurfaceRoughnessresults.
Groups N Mean Std.
Deviat
ion
Std.
Err
or
Minimum Maximum
A 3 1.19267 .404181 0.233354 0.929 1.658
A1 3 0.98367 0.026502 0.015301 0.965 1.014
B 3 1.25033 0.336898 0.194508 0.626 1.626
B1 3 0.96600 0.076374 0.044095 0.878 1.015
C 3 0.98500 0.109494 0.063217 0.868 1.085
C1 3 0.96833 0.090185 0.052068 0.875 1.055

4-Tensile Strength Test :-
A significant difference between groups. The value
may be related to degree of polymerization and
crystalline nature as well as less voids within materials
which agree with John et al., (2001), who reported that
presence of voids which assocaited with polymerization
shrinkage due to excess monomer applied during
procedure.
Figure (4.13): M ean, Standerd Deviation and Duncan᾿s Multiple
Range of Modulus of Elasticity results of acrylic study groups.
0
200
150
100
50
250
A A1 B B1 C C1
ModulusofElasticity
MPa
Table(4.14):F-testbyANOVAtableofTensileStrenght results.
Sumof
Squar
es
df Mean
Squa
re
F P-value
BetweenGroups 3353.787 5 670.757 62.234 0.000*
Total 3612.460 29*SignificantdifferenceatP≤0.05.df:degreeof freedom

A significant difference between all groups in water
sorption which may be due to the presence of voids that
lead to diffusion of ionic molecules of water between the
polar bonds of acrylic resin.
Table(4.23):F-testbyANOVAtableofWaterSorptionresults.
Sumof
Squares
df Mean
Square
F P-value
BetweenGroups 62.766 5 12.553 4.239 0.003*
Total 222.682 59
*SignificantdifferenceatP≤0.05.df:degreeof freedom
Figure (4.20): Mean, Standerd Deviation and Duncan᾿s Multiple Range of Water
Sorption result in acrylic samples groups.
4
3
2
1
0
7
6
5
A A1 B B1 C C1WaterSorptionmg/cm3

A non – significant difference between all groups in
water solubility test due to the small amount of residual
monomer released. Water solubility may be due to a
decrease in the potential sites of water exchange occur
and related to the leach of soluble materials like residual
monomer and plasticizers.
Figure (4.21): Mean, Standerd Deviation and Duncan᾿s Multiple Range of Water
Solubility results of acrylic sample groups.
1
0
4
3
2
6
5
A A1 B B1 C C1
Watersolubility
mg/cm3
Table(4.26):F-tsetbyANOVAtableofWaterSolubilityresults.
Sumof
Squ
ares
df Mean
Squ
are
F P-value
BetweenGroups 10.904 5 2.181 0.610 0.693
Total 204.066 59

6- Porosity Test :-
A non significant difference between all groups which maybe
related to polymer processing temp. higher than 74°C.
Density of the acrylic , pressure in polymerization was
considered to minimize porosity.
(PMMA) monomer has a high vapor pressure. Processing
temp. beyond 100.3°C causes vaporation of monomer which
produces porosity in the final set material.
Figure (4.22): Mean, Standerd Deviation and Duncan᾿s Multiple Range of
porosity results of acrylic study groups.
1.2
1
0.8
0.6
0.4
0.2
0
A A1 B B1 C C1
Porosity
%
Table(4.28):DiscripitiveStatisticsofPorosity results.
Grou
ps
N Mean Std.
Deviation
Std.Error Mini
mu
m
Maxi
mu
m
A 10 1.020790 0.4422391 0.1398483 0.3158 1.6670
A1 10 0.839650 0.2051769 0.0648826 0.4667 1.1818
B 10 0.990570 0.3158792 0.0998898 0.5333 1.5466
B1 10 0.897870 0.2451328 0.0775178 0.5385 1.3333
C 10 0.876950 0.4013481 0.1269174 0.4282 1.6250
C1 10 0.697150 0.2510358 0.0793845 0.4111 1.2677

7-Density Test :-
T- Test revealed a significant difference between
the powder of control and modified groups and
decrease in its weight due to thermal effect and
change in particle size, this finding is agreement with
AL - Saraj (2014) who reported that thermal effect
lead to enhanced the nucleation process, change
particle size and decrease density of acrylic
•7
Table(4.31):T-TestofDensityresults.
Grou
p
N Mean Std.
Deviation
Std.Error
Mean
t df P-
value
A 3 0.646933 0.0008386 0.0004842 10.263 4 0.001*
A1 3 0.601933 0.0075481 0.0043579
*SignificantdifferenceatP≤0.05.df:degreeFigure (4.23 ): T-Test results of acrylic study groups.
0.65
0.64
0.63
0.62
0.61
0.6
0.59
0.58
0.57
Control Group Modification
Density
gm/cm3

A non significant difference between all groups in (∆E) of
colour property test.
The monomer conc. was responsible for colour changes
associated with porosity caused by over heating .
This finding is in agree with Madhyastha and Kotain,
(2013) who found the colour stability was influenced by
the type of materials, methods of cure, and leaching of
monomer.
Table(4.48):F-testbyANOVAofColourDifference(∆E) results.
Sumof
Squares
df Mean
Square
F P-value
BetweenGroups 4.561 5 0.912 1.008 0.435
Total 26.283 29
F i g u r e (4.29): M e a n , S t a n d e r d De vi a t i on a n d D u n c a n ᾿ s M u l t i p l e
r a n g e results of c ol ou r d i f fe r enc e ( ∆ E ) of acrylic s t u d y g r ou p s .
4
3.5
3
2.5
2
1.5
1
0.5
0
A A 1 B B 1 C C 1
ColourDifference
(∆E)

A significat difference between all groups.
The finding of results may be due to the different in
the density of sample.
The higher the quantity of components of the
material is lower the melting point (Tylor, 1994).
Table(4.51):F-testbyANOVAofMeltingpoint results.
Sumof
Squar
es
df Mean
Squa
re
F P-value
BetweenGroups 268.400 5 53.680 2.668 0.047*
Total 751.200 29*SignificantdifferenceatP≤0.05.df:degreeof freeom
Figure (4.30): Mean, Standerd deviation and Duncan᾿s Multiple Range of
Melting point results of acrylic study groups.
292
290
288
302
300
298
296
294
A A1 B B1 C C1
MeltingPointC

10-Polymerization Shrinkage Test :-
A non significant difference between all groups.
This finding may be due to the type of curing cycle and
different coeffecient of gypsum and acrylic resin which
affects the residual monomer content.
Table(4.53):DescripitiveStatisticsofPolymerizationShrinkage results.
Groups N Mean Std.
Deviation
Std.Error Mini
mu
m
Maxi
mu
m
A 5 6.251480 4.3760532 1.9570305 1.4697 11.2290
A1 5 5.178660 0.6983465 0.3123100 4.2371 5.8948
B 5 7.213020 2.7929391 1.2490403 5.1175 11.5765
B1 5 7.064500 1.1863378 0.5305464 5.2911 8.6134
C 5 8.533660 1.4583795 0.6522071 6.2055 10.0616
C1 5 8.226300 1.3651397 0.6105090 5.9349 9.2656
9
8
7
6
5
4
3
2
1
0
A A1 B B1 C C1
Figure (4.31): Mean, Standerd deviation andDuncan᾿s MultipleRange of
Polymerization Shrinkageresults of acrylic study groups.
PoymerizationShrinkage%

Jorge et al., (2003) reported that, total heat in fast
polymerization cycles, could exceed the boiling point
of the monomer causes internal porosities that affect
the polymerization shrinkage and dimensional
accurey.
The curing of polymer by autoclave decreased
monomer released, internal porosities and changed
the (Tg) of the polymer.

11-Fourier Transform Infrared Spectroscopy
(FTIR) Test:-
The results showed no changes in the chemical
structure of the modified groups.
When the (C = C) bond was decreased in its height
the amount of residual monomer decreased and this
finding agree with Ebraheem, (2014) who reported
that the height of (C = C) bond indicates the residual
monomer polymer group.

12-Degree of Conversion Test :-
A non significant difference between all groups.
The polymerization time and the temp. affect the
residual monomer of polymer. Above (Tg) of polymer,
the monomer had a better ability to polymerize due to
higher molecular chain motions and this is as in the
modified groups.
Table(4.56):DescripitiveStatisticsofDegreeofConversion results.
Groups N Mean Std.
Deviation
Std.
Err
or
Mini
mu
m
Maxi
mu
m
A 3 90.11833 0.980086 0.565853 88.995 90.799
A1 3 90.78967 0.856109 0.494275 90.228 91.775
B 3 89.16433 0.624443 0.360522 88.655 89.861
B1 3 91.68800 3.511778 2.027526 88.959 95.650
C 3 91.77933 0.618636 0.357170 91.065 92.139
C1 3 93.11833 0.985715 0.569103 92.155 94.125
94
93
92
91
90
89
88
87
A A1 B B1 C C1
Figure (4.38) : Mean, Standerd Deviation and Duncan᾿s Multiple
Range results of Degree of Conversion of acrylic study groups.
DegreeofConversion%

13-Differential Scanning Calomateric (DSC) Test:-
The powder of control groups showed broad
endothermic peak. The powder of modified groups
showed a change in thermal behavior.
The thermal behavior of both groups have changes
between them and an increase in (Tg) may be due to
the polymerization of the residual monomer or
decomposition of the benzoyl peroxide,.

.
14-Residual MonomerTest By Using (HPLC) :-
A significant difference between all groups.
Curing cycles with a temperature under 100 °C
produced polymers with higher residual (MMA) content
than those produced with a prolonged curing period at
100 °C.
Figure (4.45): Mean, Standerd Deviation and Duncan᾿s Multiple Range results of
Residual Monomer by (HPLC) of acrylic study groups.
0.2
0.25
0.3
0.35
0.4
A A1 B B1 C C1
ResidualMonomerby(HPLC)
Figure (4.54) : Calibration curve of residual mo n o m e r concentration 5 % .
y = 3068.8x + 5188.5
R² = 0.9744
50000
40000
30000
20000
10000
0
90000
80000
70000
60000
0 5 10 15 20 25 30
a
a
)a

The cross - linking agents of the acrylic resins may
also affect the residual monomer content, a rigid
polymer structure hinders the conversion of the (MMA)
monomers especially at curing temperature lower than
the glass transion temperature.
In this study, the modified curing types had a great
influence in reducing the residual monomer content
which is in agreement with many reseachers who
reported similar findings by Mohamed et al., 2008.

Conclusions :-
Within the limitation in this vitro study,, we concluded
the following :-
-The autoclave processing technique might be a good
alternative to the conventional water - bath in the curing of
acrylic resin of all study groups.
-The treatment of acrylic powder by autoclave has a
significant difference in transverse strength,tensile strength
and modulus of elasticity of all study groups.
- The treatment of acrylic powder by autoclave has a
significant decrease in hardness value in group (B1).

-The treatment of acrylic powder by autoclave has no
significant difference in surface roughness, water
solubility, porosity and polymerization shrinkage of all
study groups.
-The density of acrylic resin was decreased when
treated the powder of acrylic resin by autoclave.
- The treatment of acrylic powder by autoclave a non
significant difference in colour change.

- The treatment of acrylic resin with autoclave has
a significant difference in residual monomer in all
study groups.
- The treatment of acrylic powder with autoclave
changed its thermal behavior.

Suggestions :-
The study comes with the following suggestions
-Studying the impact strength, compressive strength
and creep of the treated powder of acrylic with
autoclave.
- Studying the biocompatibility of the treated powder
of acrylic with autoclave
-Curing the modified powder with autoclave by
microwave in different times and powers, then
measuring the physical, chemical and mechanical
properties of it.

-Evaluating the physical and chemical properties of
modified acrylic resin by autoclave curing in different
times and temperature.
- Improvement the conventional prosthetic acrylic
resins and modified acrylic by nano technology.

The Evaluation of Certain Properties of Polymethyl – Methacrylate Powder Treated By Autoclave. An in Vitro Study

The Evaluation of Certain Properties of Polymethyl – Methacrylate Powder Treated By Autoclave. An in Vitro Study

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The Evaluation of Certain Properties of Polymethyl – Methacrylate Powder Treated By Autoclave. An in Vitro Study