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.
Table-1 represents the dimensional changes of measured dentures in four different storage mediums after every two days for four weeks.
Dimensional change measured at posterior palatial region
Mean Standard deviation
Mean Standard deviation
Mean Standard deviation
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.
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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