Page 18 - SPEMD_60-3

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

Materials and methods
Three auto-polymerizing reline acrylic resins, presented in
powder-liquid formulations, were selected. Two were direct
reline resins: Kooliner (GC America Inc., Alsip, IL., USA), a
non-crosslinking material, and Ufi Gel Hard (Voco GmbH.,
Cuxhaven, Germany), a crosslinking material; these are both
composed of pre-polymerized poly(ethyl methacrylate) pow-
der particles and also the monomers isobutyl methacrylate
and 1,6-hexanediol dimethacrylate, respectively. The other
one was an indirect reline resin: Probase Cold (Ivoclar
Vivadent AG., Liechtenstein), which is composed of poly(me-
thyl methacrylate) and methyl methacrylate (Table 1). A
chlorhexidine diacetate monohydrate (Panreac Applichem,
Darmstadt, Germany) was also selected.
The powder of the reline acrylic resin and CHX were
weighed using a precision balance (A&D Company, Limited, Figure 1. Experimental design (n=8) [CHX – chlorhexidine]
Tokyo, Japan), and the liquid was measured using a graduated
pipette.
Two groups were established for each material: a control After polymerization, the specimens were removed from
group, with a 0% concentration of CHX; and an experimental the mold and polished with a 600-grit silicon carbide paper (Car-
group, where a certain concentration of CHX was incorporated bimate Paper Discs, Buehler Ltd., Lake Bluff, IL., USA) with con-
(Figure 1). Based on previous studies, 31-37 a 2.5% CHX concen- stant refrigeration. Each specimen was weighed (A&D Company,
tration was incorporated in the Kooliner experimental group Limited, Tokyo, Japan) and immersed in artificial saliva, 35,40 with
and a 5% CHX concentration in both the Ufi Gel Hard and the a ratio of 1 g/5 mL in individual graduated falcon tubes. The
Probase Cold experimental groups. specimens were stored at 37ºC (Memmert, Schwabach, Germa-
In each experimental group, CHX was incorporated and ny) with constant gentle shaking (300 rpm) for 28 days. In order
mixed with the powder of the corresponding reline acrylic res- to simulate oral conditions, the samples were subjected to a
in, using a mortar and a pestle for homogenization. After mix- protocol of chemical aging, based on cycles of 6 hours in artifi-
ing with the liquid monomer, eight specimens of each group cial saliva at pH=3 interchanging with 18 hours in artificial sa-
(n=8) were prepared using rectangular-shaped stainless molds liva at pH=7. Between each change, the samples were washed
(64×10×3.3 mm). with distilled water and dried with absorbent paper.
During the recommended polymerization time of the di- The Knoop microhardness test was performed (Duramin,
rect reline resins, specimens were maintained under compres- Stuers DK 2750, Ballerup, Denmark) with a 98.12 mN load for
sion between two glass slabs, in an oven (Ehret, Mahlberg, 30 seconds. Twelve equidistant measurements were made in
Germany), at 37±2ºC. Polymerization of the indirect reline res- each specimen, and the mean value was used as the speci-
in was carried out in a pressure device (Ivomat, Ivoclar Viva- men’s microhardness (KHN).
dent, Schaan, Liechtenstein) at the recommended time, tem- A three-point flexural test was performed with a universal
perature and pressure (Table 1). testing machine (Instron, Model 4502, Bucks, England), with a

Table 1. Materials used, composition and manufacturers’ instructions
P/LI
Material Composition Ratio Curing Cycle Manufacturer Batch Number
(g/ml) (Expiration Date)
P: PEMA, dibenzoyl peroxide, silicon
Kooliner dioxide, titanium dioxide and 10 minutes, GC America Inc., P: 1707271 (27/07/2020)
(K) cellulose acetate; 1.4/1 at 37ºC Alsip, IL., USA LI: 1608021 (08/2019)
LI: IBMA and accelerant.
P: PEMA and benzoyl peroxide; 7 minutes, Voco GmbH., P: 1816582 (09/2020)
Ufi Gel Hard (UG) LI: 1,6-HDMA and hydroxyethyl 1.77/1 at 37ºC Cuxhaven, Germany LI: 1804406 (02/2020)
methacrylate.

P: PMMA, softening agent, benzoyl 15 minutes, Ivoclar Vivadent AG., P: WT0487 (21/08/2021)
Probase Cold (PC) peroxide, catalyst and pigments; 1.5/1 at 40ºC, 4 bar Liechtenstein LI: W85050 (01/10/2021)
LI: MMA, BDMA and catalyst.
Chlorhexidine diacetate Panreac Applichem,
Chlorhexidine (CHX) – - 8F015944 (10/2023)
monohydrate. Darmstadt, Germany
P – Powder; LI – Liquid; PEMA – Poly(ethyl methacrylate); IBMA – Isobutyl methacrylate; 1,6-HDMA – 1,6-hexanediol dimethacrylate; PMMA – Poly(methyl
methacrylate); MMA – Methyl methacrylate; BDMA – 1,4-butanediol dimethacrylate