Evaluation of Dimensional Stability for Denture Bases in different Curing Techniques

Abstract

Stable record base is critical for recording an accurate maxillo-mandibular relationship and evaluation of the esthetics and phonetics of the wax trial prosthesis. To ensure intra-oral stability and retention of the record base, the base should maintain close adaptation to the cast and be dimensionally stable, this study compare the dimensional stability of visible light cure acrylic both conventionally and by using new technique of short curing cycle. Thirty maxillary cast edentulous models poured with a type IV dental di-stone, the specimen divided into three subgroups each group consist of ten cast. In the first group denture base constructed from heat cure acrylic resin using short curing cycle, while in the second group it constructed by using visible light cure acrylic resin and for the third group from visible light cure acrylic resin using new technique, the gap space occurs between the denture base and the cast measured by using traveling microscope measuring device. In this study the reading for the gap space occur between the denture base and the cast show that significantly both the short cycle and VLC new technique more dimensionally stable than that of VLC conventional technique when compared by ANOVA Table and LSD multiple comparison. The dimensional accuracy or fit for the denture base improved by using either a heat cured acrylic resin (using short curing cycle or by using light activated poly methylmethacrylate with the aid of new technique so that better stability and retention of the record bases obtained.

Dimensional Stability of Light-Activated Urethane Dimethacrylate Denture Base Resins

“…Visible light-cured resin is characterized by improved physical characteristics, such as increased stiffness, good form, volume stability, and low sensitivity to moisture. In addition, these materials are easy to use, and their use saves time [ 10 , 11 , 12 ]. Hence, the record base should be fabricated to be accurately fitted, and it should not change, but remain stable.…”

“…The sample size was selected based on a similar previous study in which the sample size was 30 [ 12 ]. Based on the recommendations for sample size calculations in in vitro studies, the number of samples should be in accordance with the statistical calculation of previous studies and should be 10–15% greater than the regular sample size in order to anticipate the incontinence in standards [ 13 ].…”

“…The polymerization shrinkage during curing and the stresses released during flask cooling in heat-cured acrylic resins result in changes in dimensions and their magnitude is mainly affected by acrylic resin thickness [ 6 , 7 , 8 ]. Other factors include polymerization techniques, in which the difference in thermal expansion of gypsum and acrylic resin results in the development of internal stresses and variation in base thickness at different sites inside the flask results in altered record base adaptation and stability [ 9 , 10 , 11 , 12 ]. On the other hand, few authors stated that there is a reduction in the molecular weight of the resulting polymer chains after curing and so the variation in the curing techniques may not alter significantly the pattern of dimensional changes in acrylic resin.…”

“…It was marketed under the trade name “triad” and was suitable for many prosthodontic applications, including removable, fixed and maxilla facial prostheses. Light-activated urethane dimethacrylate (UDMA) denture base polymers were developed to overcome the allergies, the pungent smell in the laboratory and the conventional time-consuming lost wax method of fabricating prosthesis Polymethyl methacrylate (PMMA) materials [ 12 ]. The VLC resin was promoted as a material containing a urethane dimethacrylate matrix with an acrylic copolymer, micro-tins, silica filler, and a photo-initiator system.…”

“…Previous research into VLC documented that the material close to the light cure unit would get polymerized first, resulting in gap formation due to transformation and contraction [ 19 ]. The cause for the gap formation with the master cast is the contraction because of polymerization and cooling, as well as being lifted by internal stress during polymerization [ 2 , 8 , 12 , 18 ]. VLC resins are considered to be dimensionally stable directly after complete polymerization with the use of a proper light source and exposure time [ 1 , 2 , 17 , 18 ].…”