Page 17 - SPEMD_60-3

rev port estomatol med dent cir maxilofac . 2019;60(3):104-110 105

Microdureza e resistência à flexão após envelhecimento químico
de sistemas de libertação de clorexidina à base de resina acrílica

r e s u m o

Palavras-chave: Objetivos: Avaliar o efeito da incorporação de clorexidina na microdureza e na resistência à
Resinas acrílicas flexão de três resinas acrílicas de rebasamento, após um processo de envelhecimento quí-
Clorexidina mico de 28 dias.
Rebasamento Métodos: Um total de 48 espécimes foi fabricado de acordo com as diversas combinações
Estomatite protética possíveis entre resina acrílica de rebasamento e concentração de clorexidina incorporada
Dureza (Kooliner – 0% vs. 2,5%; Ufi Gel Hard – 0% vs. 5%; e Probase Cold – 0% vs. 5%), de forma a criar 6
Resistência à flexão grupos experimentais (n=8). Após um processo de envelhecimento químico durante 4 se-
manas (variações de pH em saliva artificial, com ciclos de 6 horas em pH=3 e 18 horas em
pH=7), foram avaliadas a microdureza Knoop (98,12 mN, 30 segundos) e a resistência à flexão
(1 kN, 5 mm/minuto) de todos os espécimes. Os dados obtidos foram submetidos a testes
estatísticos não paramétricos, segundo Kruskal-Wallis e Mann-Whitney (α=0,05).
Resultados: A incorporação de clorexidina não influenciou de forma estatisticamente signi-
ficativa (Kooliner – p=0,798; Ufi Gel Hard – p=0,798; e Probase Cold – p=0,195) os valores de mi-
crodureza de nenhuma das três resinas acrílicas. Apesar da incorporação de clorexidina não
ter influenciado a resistência à flexão de Kooliner (p=0,959) e de Ufi Gel Hard (p=0,645), a in-
corporação da Probase Cold com 5% de clorexidina conduziu a resistência à flexão estatisti-
camente mais baixa que a obtida sem incorporação (p=0,021).
Conclusões: Após envelhecimento químico, não se verifica uma diminuição nos valores de
microdureza de resinas acrílicas incorporadas com clorexidina. Contudo, a incorporação de
5% de clorexidina em Probase Cold afeta negativamente os valores de resistência à flexão.
(Rev Port Estomatol Med Dent Cir Maxilofac. 2019;60(3):104-110)
© 2019 Sociedade Portuguesa de Estomatologia e Medicina Dentária.
Published by SPEMD. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).

tions have been proposed, such as reline acrylic resins, which
Introduction
act as reservoirs of antimicrobial agents, like chlorhexidine
Tooth loss is associated with a decreased integrity of the (CHX), thus allowing a continuous release of drugs at the site
masticatory system, with negative consequences in the of infection. 14,24-25
functional and esthetic aspects, in speech and in self-es- CHX is an agent with antimicrobial properties against a
teem. 1-2 Rehabilitation with removable dentures continues large number of microorganisms, including Candida spe-
3
to be one of the most sought options. However, the progres- cies. 26-28 When incorporated into resins, it has a high release
sive resorption of the alveolar ridge may lead to a decreased in the first 2 to 7 days, which then decreases and remains
adaptation of the denture base to the underlying tissues. constant for, at least, 28 days. 17,28-30
The most common procedure to solve this problem is relin- The concentration at which CHX offers antifungal activ-
ing, which consists in placing a material, usually a reline ity but does not influence the properties of several reline
acrylic resin, onto the base of the denture to fill the gap be- resins has been established in some studies. 31-37 However, in
tween the contour of the denture and the new contour of the those studies, chemical aging was not taken into account.
tissues. 4-8 Food and drinks can affect dental materials and intraoral pH
Acrylic resins used in dentures bases are polymeric bio- values. 38-39
materials with proper mechanical properties, but their po- The objective of this study was to evaluate the effect of
rous structure promotes microbial colonization and the de- loading three reline acrylic resins with CHX on their micro-
velopment of oral diseases, such as denture stomatitis. 9-13 hardness and flexural strength, after a 28-day chemical aging
Despite the multifactorial etiology of this disease, it appears process. The following hypotheses were studied: 1) there are
to be related to a quantitative increase of Candida species, no differences in microhardness between reline acrylic res-
especially Candida albicans, 14-17 a commensal fungal organism ins; 2) the reline acrylic resin does not influence flexural
that can act as an opportunistic pathogen. 18-19 Treatment is strength; 3) the incorporation of CHX does not influence the
complex and includes reducing the denture wearing time, reline acrylic resin microhardness; and 4) the incorporation
denture relining and topical antifungal therapy. 15,20-23 Medi- of CHX does not affect the flexural strength of the reline
cal devices aimed to combine these two last-mentioned op- acrylic resin.