Type of manuscript: Research article

Running Title: Storage of denture base resins

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Joshini Shanmugam

Undergraduate Student

 

Saveetha Dental College, Saveetha University, Chennai, India

 

 

 

Corresponding Author

Dr. Ashok

Senior Lecturer

Department of Prosthodontics

Saveetha Dental College

Saveetha University

162, Poonamallee High Road

Chennai 600077

Tamil Nadu, India

 

E-mail : [email protected]

 

Telephone number: +919940291573

 

Total number of words: 1,151

 

 

 

 

 

 

 

 

 

 

 

 

 

Introduction-

 

The utilization
of acrylic resin as a denture base material since 1937 has reformed the
dentistry hugely. The resin has fine esthetic properties, is incredible in
shading and is chemically steady. It can be utilized with a straightforward
strategy for the development of dentures, however the properties of acrylic
resin are not perfect in all angles.

Resin
polymers have been presented as denture base materials and these denture bases
are made utilizing polymethyl methacrylate (PMMA). These materials have ideal
physical properties and fantastic esthetics with moderately low toxic quality
contrasted with other denture base materials.

 

 The dimensional changes which take place in
heat cure acrylic resins are shrinkage and expansion which influences the fit
and occlusal relationship of the denture with the underlying oral mucosa1.
Despite the fact that acrylic resin polymer is known for its phenomenal
properties, it has its own particular drawbacks like distortion. Exact
duplication of trial denture into the final prosthesis is the coveted point
amid handling in the lab. In any case, certain properties like dimensional
errors of the materials trade off the achievement of this objective ideally.

 

Consequently
a satisfactory medium ought to be chosen for storage of denture with a specific
end goal to limit the distortion for dependable utilization. So it is vital to
find what sort of storage medium can be prescribed keeping in mind the end goal
to avert dimensional changes of the denture. Considering the importance of
dimensional changes occurring during storage, the present study was undertaken
to determine linear dimensional changes of commercially available heat cure
acrylic resins in four liquid mediums.

 

Materials and
method-

 

This
in-vitro experimental study was conducted on four types of liquid medium
(water,  saline, artificial saliva,
vinegar) with heat cure acrylic resins. Based on the number of mediums, five
dentures were determined for each group (N=20).

 

The
fabricated denture bases were stored into following storage environments:
water, saline, artificial saliva vinegar. Saline and water mediums were kept at
room temperature whereas artificial saliva and vinegar mediums were stored at
refrigerator temperature. The dentures were allowed to be stored in the mediums
for 4 weeks where every 2 days the dentures were placed in the cast were
measured using digital vernier to check for any distortion. The denture bases
were measured in the posterior-palatal region, the interface between the cast
and the denture. Finally after four
weeks, all the measurements that were taken, were compared with the base
measurements and analyzed by Paired T-testusing SPSS software version 20 at
significant P-value of 0.05.

 

Results:

 

Table-1 represents the dimensional changes of measured
dentures  in four different storage
mediums after every two days for four weeks.

 

 

 

 

 

 

 

 

Water

Artificial saliva

Saline

Vinegar

Days:

Dimensional change measured at
posterior palatial region

P-value

Mean Standard deviation

P-value

Mean Standard deviation

P-value

Mean Standard deviation

P-value

2nd day-

0.000mm

0.209

0.000mm

0.274

0.000mm

0.250

0.000mm

0.246

4th day-

0.002mm

0.145

0.000mm

0.155

0.003mm

0.210

0.005mm

0.310

8th day-

0.009mm

0.349

0.002mm

0.593

0.10mm

0.453

0.012mm

0.398

16th day-

0.019mm

1.013

0.010mm

0.379

0.020mm

0.676

0.020mm

0.523

20th day-

0.022mm

0.149

0.012mm

0.416

0.028mm

0.761

0.028mm

0.512

25th day-

0.028mm

0.637

0.013mm

0.511

0.033mm

0.528

0.033mm

0.687

30th day-

0.031mm

1.000

0.015mm

0.721

0.040mm

0.947

0.052mm

0.841

 

 

To
determine the difference in each sample before and after storage in the liquid
mediums, paired t -test was used which is shown in table 1. The data showed the
dentures stored in vinegar and saline contracted 0.052mm and 0.040mm
respectively and the dentures which were stored in water and artificial saliva
contracted 0.031mm, 0.015mm respectively.

 

 

 

 

 

 

VINEGAR:

 

   
 

 

 

 

 

 

 

 

 

 

 

Discussion-

 

The
studies done in the past years indicate that the acrylic denture base resins
tend to absorb water, in this manner expansion can make up when minimal
polymerization shrinkage takes place. This can clarify the minimal measure of
dimensional changes seen in acrylic heat cure denture resins which were put in
water which is as per the findings of this study. (2-4)

Wong
et al (2), revealed that the tendecy to retain water in  acrylic
resins show shrinkage amid setting. Expansion that follows absorption of
water can make up for a part or the majority of the polymerization shrinkage or
even expansion can happen.

Goodkind 6
conducted a study which indicated that water immersion had no critical impact
on denture base measurements.

Consani 5 reported
that 90 days of storage of denture bases in water did not result in significant
changes in distances between the teeth in comparison to deflasking period.
Miessi 7 reported that 180 days of immersion in water caused major
dimensional changes and adaptation problems in denture bases. Some authors have
reported that water storage of acrylic denture bases results in expansion due
to water sorption. Water sorption forces the macromolecules apart and results
in acrylic expansion 8. This expansion
compensates the polymerization shrinkage of acrylic resin and improves the
adaptation of denture bases with underlying tissues 7. The
present study also confirmed this finding and showed that in both experimental
groups, 30 days of storage in water resulted in a significant decrease in
dimensional changes and compensated the polymerization shrinkage

Within
the limitations of this study, water and artificial saliva were the best
mediums to be used.

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