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108 rev port estomatol med dent cir maxilofac. 2019;60(3):104-110

Kooliner and Ufi Gel Hard are both direct reline resins com- The three materials tested in the present study are reline
posed of poly(ethyl methacrylate) particles; however, Kooliner acrylic resins that are not used independently in the oral cav-
is also composed of isobutyl methacrylate, forming a ity but always associated with a base denture material. Further
non-crosslinking net, whereas Ufi Gel Hard is composed of research should be conducted to study the flexural and adhe-
1,6-hexanediol dimethacrylate and forms a crosslinking net, sive strength of these materials together. Likewise, other phys-
thus being more complex than Kooliner. 41-42 In turn, Probase ical and mechanical properties of reline acrylic resins loaded
Cold is an indirect reline resin composed of poly(methyl meth- with CHX, under a combination of thermal, chemical and me-
acrylate) and methyl methacrylate that presents a reduced chanical aging, should be tested, in order to better reproduce
amount of residual monomer after its polymerization. 41-42 the oral environment.
The CHX concentration used to load each reline acrylic
resin was based on the findings of previous studies. 30-37 A 2.5%
CHX concentration in Kooliner and a 5% CHX concentration in Conclusions
Ufi Gel Hard and Probase Cold seem to reduce the microbio-
logical activity of Candida albicans without affecting the me- The indirect reline acrylic resin presented higher microhard-
chanical properties of the reline resins. 31,33-34 Incorporating ness and flexural strength than the direct reline acrylic resins
higher percentages of CHX could negatively influence the me- tested.
chanical properties of the studied materials. 31,33 After chemical aging, loading Kooliner or Ufi Gel Hard with
In order to simulate oral conditions, all specimens were CHX did not affect their microhardness and flexural strength.
aged immersed in artificial saliva in interchanging cycles of 6 However, incorporating 5% chlorhexidine into Probase Cold
hours at pH=3 and 18 hours at pH=7. 39,43-45 decreased its flexural strength, even though its microhardness
Since the reline acrylic resin may be considered a provi- was not affected.
sional material, and considering the time during which CHX
release levels remain constant for an effective treatment of
denture stomatitis, a 28-day aging period was selected to allow Acknowledgments
comparison with previous research studies. 14,17,26,28-30,46
Given that Probase Cold presented higher microhardness The authors thank VOCO GmbH for providing the Ufi Gel Hard
and flexural strength than the other reline acrylic resins stud- evaluated in this study.
ied, the first and second null hypotheses are rejected. These
results are in accordance with previous studies with different
aging conditions. 32-33 The higher degree of conversion of Ethical disclosures
Probase Cold could justify these results. 41-42
The third hypothesis is not rejected since, after a chemical Protection of human and animal subjects. The authors
aging process, the microhardness of the three reline acrylic declare that no experiments were performed on humans or
resins was not affected by the CHX incorporation. These re- animals for this study.

sults agree with a previous study that included a thermal, and
not chemical, aging protocol. 32 Confidentiality of data. The authors declare that no patient
data appear in this article.
Although the incorporation of resins with antimicrobial
agents has shown a reduction of flexural strength, 31-33,47-52 in Right to privacy and informed consent. The authors declare
the present research, the flexural strength of Kooliner and Ufi that no patient data appear in this article.
Gel Hard was not influenced by the CHX incorporation. The
results obtained in the present study agree with previous re-
sults found by this research group, where Kooliner loaded with Conflict of interest
2.5% CHX and Ufi Gel Hard with 5% CHX did not show a nega-
tive impact on flexural strength, with different aging environ- The authors have no conflicts of interest to declare.
ments. 32-33 The similar chemical constitution of these direct
reline materials could explain why they were not affected. In
41
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